AU2013201697B2 - Integrated Fan Drive System For Air-Cooled Heat Exchanger (ACHE) - Google Patents

Abstract

An integrated fan drive system for air-cooled heat exchangers. The integrated fan drive system has a high-torque, low speed permanent magnet motor having a rotatable shaft, a fan that is directly connected to the rotatable shaft, and a variable frequency drive device in electrical signal communication with the permanent magnet motor to control the rotational speed of the permanent magnet motor. The high- torque, permanent magnet motor comprises no more than two bearings in operative associa N tion with the shaft. The variable frequency drive device has a variable frequency controller that has an input for receiving AC power and an output for providing electrical signals that control the operational speed of high-torque, permanent magnet motor. The variable frequency drive device also includes a user interface in electronic data signal communication with the variable fre quency controller to allow a user to input motor speed control data. Other embodiments of the invention are described herein.

Description

2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242

1 INTEGRATED FAN DRIVE SYSTEM FOR 2 AIR-COOLED HEAT EXCHANGERS (ACHE) 3 4 CROSS-REFERENCE TO RELATED APPLICATIONS: 5 This application claims the benefit of U.S. provisional application no. 6 61/038,851, filed March 24, 2008. The entire disclosure of the aforesaid application 7 no. 61/038,851 is hereby incorporated by reference. 8 9 TECHNICAL FIELD: 10 The present invention generally relates to fan drive systems for use with air- 11 cooled heat exchangers (ACHE). 12 13 BACKGROUND ART: 14 Air Cooled Heat Exchangers (ACHE) are well known in the art and are used for 15 cooling in a variety of industries including power plants, petroleum refineries, 16 petrochemical and chemical plants, natural gas processing plants, and other industrial 17 facilities that implement energy intensive processes. ACHE exchangers are used 18 typically where there is lack of water, or when water usage permits cannot be 19 obtained, or where there is not sufficient real estate to build a tower. ACHEs lack the 20 cooling effectiveness of “Wet Towers”. 21 Typically, an ACHE uses a finned-tube bundle with rectangular box headers on 22 both ends of the tubes. Cooling air is provided by one or more large fans. Usually, 23 the air blows upwards through a horizontal tube bundle. The fans can be either forced 24 or induced draft, depending on whether the air is pushed or pulled through the tube 1 1 bundle. The space between the fan(s) and the tube bundle is enclosed by a plenum 2013201697 23 Jan 2014 2 chamber which directs the air (flow field) over the tube bundle assembly thereby 3 providing cooling. The whoie assembly is usually mounted on legs or a pipe rack. 4 The fans are usually driven by electric induction motors through some type of speed 5 reducer. The speed reducers are typically V-belts, HTD drives, or right-angle gears. 6 The fan drive assembly is supported by a steel mechanical drive support system. 7 They usually include a vibration switch on each fan to automatically shut down a fan

8 which has become imbalanced for some reason. Airflow is very important in ACHE 9 cooling to ensure that the air has the proper “flow field” and velocity to maximize ίο cooling. Turbulence and “choked-fldw conditions can impair cooling efficiency. 11 Therefore, mass airflow is the key parameter to removing heat from the tube and 12 bundle system. ACHE cooling differs from “wet" cooling (i.e. wet cooling towers) 13 towers in that ACHE systems do not use water to cool the tube bundle and thus, do μ not benefit from the latent heat of vaporization or “evaporative cooling”. 15 Prior art ACHE fan drive systems use anyone of a variety of fan drive 16 components. Examples of such components include electric motors, steam turbines, 17 gas or gasoline engines, or hydraulic motors. The most common drive device is the is electric motor. Steam and gas drive systems have been used when electric power is 19 not available. Hydraulic motors have also been used with limited success. 20 Specifically, although hydraulic motors provide variable speed control, they have 21 relatively low efficiencies. 22 Fan-tip speed should not exceed 12,000 feet per minute for mechanical 23 reasons, and may be reduced to obtain lower noise levels. Motor and fan speed are 2 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 sometimes controlled with variable frequency drives. The most commonly used speed 2 reducer is the high-torque, positive type belt drive, which uses sprockets that mesh 3 with the timing belt cogs. They are used with motors up to 50 or 60 horsepower, and 4 with fans up to about 18 feet in diameter. Banded V-belts are still often used in small 5 to medium sized fans, and gear drives are used with very large motors and fan 6 diameters. Fan speed is set by using a proper combination of sprocket or sheave 7 sizes with timing belts or V-belts, and by selecting a proper reduction ratio with gears. 8 In many instances, right-angle gear boxes are used as part of the fan drive system in 9 order to translate and magnify torque from an offset electrical motor. However, belt 10 drives, pulleys and right-angle gear boxes have poor reliability. 11 The aforesaid complex, prior art mechanical drive systems require stringent 12 maintenance practices to achieve acceptable levels of reliability. In particular, one 13 significant problem with ACHE fan systems is the poor reliability of the belt due to belt 14 tension. A common practice is to upgrade to “timing belts” and add a tension system. 15 One technical paper, entitled “Application of Reliability Tools to Improve V-Belt Life on 16 Fin Fan Cooler Units”, by Rahadian Bayu of PT. Chevron Pacific Indonesia, Riau, 17 Indonesia, presented at the 2007 International Applied Reliability Symposium, 18 addresses the reliability and efficiency of V-belts used in many prior art fan drive 19 systems. 20 The reliability deficiencies of the belt and pulley systems and the gear reducer 21 systems used in the ACHE fan drive systems often result in outages that are 22 detrimental to mission critical industries such as petroleum refining, petro-chemical, 23 power generation and other process intensive industries dependant on cooling. 3 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 Furthermore, the motor systems used in the ACHE fan drive systems are complex 2 with multiple bearings, auxiliary oil and lubrications systems, complex valve systems 3 for control and operation, and reciprocating parts that must be replaced at regular 4 intervals. Many petroleum refineries, power plants, petrochemical facilities, chemical 5 plants and other industrial facilities utilizing prior art ACHE fan drive systems have 6 reported that poor reliability of belt drive systems and right-angle drive systems has 7 negatively affected production output. These industries have also found that service 8 and maintenance of the belt drive and gearbox system are major expenditures in the 9 life cycle cost, and that the prior art motors have experienced failure due to the mis- 10 use of high pressure water spray. 11 The duty cycle required of an ACHE fan drive system is extreme due to intense 12 humidity, dirt and icing conditions, wind shear forces, corrosive water treatment 13 chemicals, and demanding mechanical drive requirements. 14 In an attempt to increase the efficiency of ACHE cooling systems, some end- 15 users spray water directly on the ACHE system to provide additional cooling on 16 process limiting, hot days. Furthermore, since fan blades can become “fouled” or dirty

17 in regular service and lose performance, many end-users water-wash their ACHE

18 system to maintain their cooling performance. However, directly exposing the ACHE 19 system to high pressure water spray can lead to premature maintenance and/or failure 20 of system components, especially since prior art drive systems are typically open 21 thereby allowing penetration by water and other fluids. 22 Refining of petroleum cannot take place without cooling. Refineries process 23 hydrocarbons at high temperatures and pressures. The loss of cooling within a 4 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 refinery can lead to unstable and dangerous operating conditions requiring an 2 immediate shut down of processing units. Cooling systems have become "mission 3 critical assets" for petroleum refinery production. As demand for high-end products 4 such as automotive and aviation fuel has risen and refining capacity has shrunk, the 5 refineries have incorporated many new processes that extract hydrogen from the 6 lower value by-products and recombined them into the higher value fuels, improving 7 yield. Many of these processes depend on cooling to optimize the yield and quality of 8 the product. Refining processes also incorporate many advanced processes that 9 need reliable cooling systems to protect profitability. Cooling reliability has become 10 mission critical to refinery profit and is affected by many factors such as environmental 11 limitations on cooling water usage, inelastic supply chain pressures and variable 12 refining margins. Many refineries have been adding processes that reform low grade 13 petroleum products into higher grade and more profitable products such as aviation 14 and automotive gasoline. These processes are highly dependent upon cooling 15 systems to control the process temperatures and pressures that affect the product 16 quality, process yield and safety of the process. In addition, these processes have 17 tapped a great deal of the cooling capacity reserve leaving some refineries "cooling 18 limited" on hot days and even bottlenecked. Most U.S. refineries operate well above 19 90% capacity and thus, uninterrupted refinery operation is critical to refinery profit and 20 paying for the process upgrades implemented over the last decade. The effect of the 21 interruption in the operation of cooling units with respect to the impact of petroleum 22 product prices is described in the report entitled "Refinery Outages: Description and 5 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 Potential Impact On Petroleum Product Prices", March 2007, U.S. Department of 2 Energy. 3 Thus, the efficiency and production rate of a process is heavily dependent upon 4 the efficiency of the ACHE cooling fan drive system and its ability to remove heat from 5 the system. 6 Therefore, in order to prevent supply interruption of the inelastic supply chain of 7 refined petroleum products, the reliability and subsequent performance of ACHE fan 8 drive systems must be improved and managed as a key asset to refinery production 9 and profit. An efficient and reliable fan drive system is required to maintain a relatively 10 high cooling efficiency and prevent interruptions in production. 11 12 DISCLOSURE OF THE INVENTION: 13 Accordingly, it is an object of the present invention to provide a fan drive 14 system that substantially eliminates the aforementioned problems and disadvantages 15 associated with prior art fan drive systems. The present invention is directed to, in 16 one aspect, a fan drive system for an air-cooled heat exchanger system, comprising a 17 high-torque, low speed permanent magnet motor having a rotatable shaft, a fan 18 comprising a hub that is directly connected to the rotatable shaft and a plurality of fan 19 blades that are attached to the hub, and a variable frequency drive device in electrical 20 signal communication with the permanent magnet motor to control the rotational 21 speed of the permanent magnet motor. 22 In a related aspect, the present invention is directed to an air-cooled heat 23 exchanger system having a forced draft configuration, comprising a structure 6 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 supporting a tube bundle, a fan rotatably mounted to the structure and positioned 2 under the tube bundle, a high-torque, low speed permanent magnet motor supported 3 by the structure and having a rotatable shaft that is connected to the fan, and a 4 variable frequency drive device in electrical signal communication with the permanent 5 magnet motor to control the rotational speed of the permanent magnet motor. 6 In a further aspect, the present invention is directed to an air-cooled heat 7 exchanger system having an induced draft configuration, comprising a structure 8 supporting a tube bundle, a fan rotatably mounted to the structure and positioned 9 above the tube bundle, a high-torque, low speed permanent magnet motor supported 10 by the structure and having a rotatable shaft that is connected to the fan, and a 11 variable frequency drive device in electrical signal communication with the permanent 12 magnet motor to control the rotational speed of the permanent magnet motor. In one 13 embodiment, the high-torque, permanent magnet motor is positioned above the tube 14 bundle. In another embodiment, the high-torque, permanent magnet motor is 15 positioned below the tube bundle. 16 Other objects of the present invention, as well as particular features, elements 17 and advantages thereof will be apparent from the following description and the 18 accompanying drawing figures. 19 20 BRIEF DESCRIPTION OF THE DRAWINGS: 21 Understanding of the present invention and the various aspects thereof will be 22 facilitated by reference to the accompanying drawing figures submitted for the 23 purposes of illustration only and not intended to define the scope of the invention. In 24 which: 7 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 FIG. 1 is a basic diagram, partially in cross-section, of an induced draft, air- 2 cooled heat exchanger (ACHE) system that uses a prior art fan drive system; 3 FIG. 2 is a basic diagram, partially in cross-section, of a forced draft, air-cooled 4 heat exchanger (ACHE) system that uses a prior art fan drive system; 5 FIGS. 3 and 4 are side views of a prior art, gear-box type fan drive system; 6 FIG. 5 is a partial, top plan view of a prior art, belt-driven fan drive system; 7 FIG. 6 is a partial, top plan view of a prior art, driven-sprocket fan drive system; 8 FIG. 7 is a partial, side view, in elevation and partially in cross-section, of a 9 forced-draft, ACHE that uses a fan drive system of the present invention; 10 FIG. 8 is a schematic diagram of the fan drive system of the present invention; 11 FIG. 9 is a schematic diagram showing the fan drive system of the present 12 invention in conjunction with a plurality of performance monitoring sensors; 13 FIG. 10 is a plot of motor speed versus horsepower for a high torque, low 14 speed permanent magnet motor used in the fan drive system of the present invention; 15 FIG. 11 is a graph illustrating a comparison in performance between the fan 16 drive system of the present invention and a prior art gearbox-type fan drive system 17 that uses a variable speed induction motor; 18 FIG. 12 is a plot of motor speed versus motor torque for the high torque, low 19 speed permanent magnet motor used in the fan drive system of the present invention; 20 FIG. 13 is a side view, in elevation and partially in cross-section, of an induced 21 draft, ACHE that uses the fan drive system of the present invention; and 8 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 FIG. 14 is a side view, in elevation and partially in cross-section, of an induced 2 draft, ACHE that uses the fan drive system of the present invention, the fan drive 3 system being mounted above the tube bundle; 4 5 BEST MODE FOR CARRYING OUT THE INVENTION: 6 Referring to FIG. 1, there is shown a basic diagram of an air-cooled heat 7 exchanger (ACHE) system 10 that uses a prior art fan drive system. ACHE system 10 8 is configured as an induced draft system. ACHE system 10 generally comprises a 9 support structure that comprises a plurality of support columns 11. Tube bundle 12 is 10 supported by the ACHE support structure. Plenum 13 is located above tube bundle 11 12. Fan ring 14 is attached to plenum 13. Fan 15 rotates within fan ring 14. Fan 15 12 has hub 15A. Vertically oriented fan shaft 16 extends through plenum 13 and tube 13 bundle 12 and is connected to prior art fan drive system 17. Fan drive system 17 is 14 typically supported by a support 18 that is connected to support columns 11 and or 15 other portions of the ACHE support structure. Referring to FIG. 2, there is shown a 16 basic diagram of another air-cooled heat exchanger (ACHE) system 20 that uses a 17 prior art fan drive system. ACHE system 20 is configured as a forced draft system. 18 ACHE system 20 generally comprises a support structure that comprises a plurality of 19 support columns 21. Tube bundle 22 is supported by the ACHE support structure. 20 Plenum 23 is located below tube bundle 22. Fan ring 24 is attached to and positioned 21 under plenum 23. Fan 25 rotates within fan ring 24. Fan 25 has hub 25A. Vertically 22 oriented fan shaft 26 is connected to prior art fan drive system 27. Fan drive system 23 27 is typically supported by support 28 that is connected to support columns 21 and/or 24 to other portions of the ACHE support structure. Prior art fan drive systems 17 and 27 9 1 shown in FIGS. 1 and 2, respectively, can be configured as any one of the prior art 2013201697 23 Jan 2014 2 fan drive systems discussed in the foregoing discussion. FIGS. 3, 4, 5 and 6 show 3 the commonly or widely used prior art fan drive systems. FIGS. 3 and 4 show the 4 common gear-box type fan drive system. This prior art fan drive system comprises 5 induction motor 29 and right-angle gear box 30. The shaft of motor 29 is coupled to

6 right-angle gear box 30 by coupling 31. Shaft 32 extends from gear box 30. A 7 coupling 33 is connected to shaft 32. Induction motor 29 and gear box 30 are 8 mounted to support plate 34. Support plate 34 is mounted to machinery mount 35. 9 Support plate 34 and machinery mount structure 35 are part of the structure of the id ACHE system. Fan mount 36 is attached to coupling 33. The fan (not shown) is 11 connected to fan mount 36. Fan mount support members 37 provide support to fan 12 mount 36. 13 FIG. 5 shows a prior art fan-drive system that uses a belt-drive configuration 14 to drive the fan in an ACHE system. This fan-drive system comprises induction motor is 38 (shown in phantom), sprocket 39 and belt 40. Sprocket 39 is connected to a fan 16 mount 42. Rotation of the shaft of induction motor 38 causes rotation of sprocket 39 π which, in turn, causes rotation of the fan (not shown). Induction motor 38 is mounted is to a support plate 43 which is adjustably attached to support member 44. Belt- 19 tension adjustment device 45 can adjust the position of support plate 43 with respect 20 to support member 44 in order to adjust the tension on belt 40. 21 FIG. 6 shows a prior art fan-drive system that uses a drive sprocket to drive 22 the fan in an ACHE system. This fan-drive system comprises induction motor 46 23 (shown in phantom), driver sprocket 47 and driven sprocket 48. Driver sprocket 47 is 10 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 connected to the shaft 46A of induction motor 46 and engaged with driven sprocket 2 48. Driven sprocket 48 is connected to fan mount 42 which is connected to the fan 3 (not shown). Rotation of driver sprocket 47 causes rotation of driven sprocket 48 4 which, in turn, causes rotation of the fan. Motor 46 is mounted to motor support 5 member 49A. Motor support member 49A is movably attached to support structure 6 49B. Motor position adjustment device 49C can be used to adjust the position of 7 motor support member 49A so as to ensure proper engagement of driver sprocket 47 8 and driven sprocket 48. 9 Referring to FIG. 7, there is shown a partial view of an ACHE system that is 10 configured as a forced draft ACHE and has the same general structural components 11 as the ACHE shown in FIG. 2, except for the prior art fan drive system which has now

12 been replaced with the fan drive system of the present invention. Since this ACHE 13 system is a forced draft system, fan 25 is below tube bundle 22. The fan drive system 14 of the present invention comprises variable frequency drive (VFD) device 50 and 15 motor 52. In accordance with the invention, motor 52 is a high torque, low speed 16 permanent magnet motor. Permanent magnet motor 52 has a high flux density. The 17 superior results, advantages and benefits resulting from permanent magnet motor 52 18 are discussed in the ensuing description. VFD device 50 and permanent magnet

19 motor 52 are mounted to or supported by the support structure 28 of the ACHE 20 system. VFD device 50 is in electrical signal communication with permanent magnet i, 21 motor 52 via cables or wires 54. Permanent magnet motor 52 has shaft 56 that rotates 22 when the appropriate electrical signals are applied to permanent magnet motor 52. 11 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 Shaft 56 is connected to fan hub 25A. Thus, rotation of vertical shaft 56 causes 2 rotation of fan 25. Fan 25 rotates within fan ring 23. 3 Referring to FIG. 8, VFD device 50 comprises a variable frequency controller 4 60 and a user or operator interface 62. VFD device 50 controls the speed, direction

5 (i.e. clockwise or counterclockwise), and torque of permanent magnet motor 52. AC 6 input power is inputted into variable frequency controller 60 via input 64. Variable 7 frequency controller 60 converts the AC input power to DC intermediate power.

8 Variable frequency controller 60 then converts the DC power into quasi-sinusoidal AC 9 power that is applied to permanent magnet motor 52. User interface 62 provides a 10 means for an operator to start and stop permanent magnet motor 52 and adjust the 11 operating speed of motor 52. In a preferred embodiment, user interface 62 comprises 12 a microprocessor, and an alphanumeric display and/or indication lights and meters to 13 provide information about the operation of motor 52. User interface 62 further includes 14 a keypad and keypad display that allows the user to input desired motor operating 15 speeds. VFD device 50 includes input and output terminals 70 and 72 for connecting 16 pushbuttons, switches and other operator interface devices or controls signals. In a 17 preferred embodiment, VFD device 50 further includes a serial data communication 18 port 80 to allow VFD device 50 to be configured, adjusted, monitored and controlled 19 using a computer. In one embodiment, VFD device 50 includes sensor signal inputs 20 82, 84, 86, 88 and 89 for receiving sensor output signals. The purpose of these 21 sensors is discussed in the ensuing description. 22 Referring to FIGS. 7 and 8, permanent magnet motor 52 is directly coupled to 23 the fan hub 25A. Since permanent magnet motor 52 is controlled only by electrical 12 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 signals provided by VFD device 50, there are no couplings, gear boxes, drive shafts or 2 related components as found in the prior art gearbox-type fan drive system shown in 3 FIGS. 3-4, and there are no sprockets, belts and related components as found in the 4 prior art fan drive system shown in FIG. 5, and there are no driver sprockets, driven 5 sprockets and related components as found in the prior art fan drive system shown in 6 FIG. 6. In accordance with the invention, permanent magnet motor 52 is a high- 7 torque, low speed motor. Permanent magnet motor 52 is of simplified design and uses 8 only two bearings 90 and 92 (see FIG. 9). Permanent magnet motor 52 includes stator 9 94. Such a simplified design provides relatively high reliability as well as improved 10 energy efficiency. Permanent magnet motor 52 has relatively low maintenance with a 11 three year lube interval. Permanent magnet motor 52 can be configured with sealed 12 bearings. Permanent magnet motor 52 meets or exceeds the efficiency of Premium 13 Efficiency Induction Motors. Permanent magnet motor 52 substantially reduces the 14 man-hours associated with service and maintenance that would normally be required 15 with a prior art, induction motor fan drive system. In some instances, permanent 16 magnet motor 52 can eliminate up to 1000 man-hours of maintenance and service. 17 Such reliability reduces the amount of cell outages and significantly improves product 18 output. 19 In one embodiment, permanent magnet motor 52 has the following operational 20 and performance characteristics:

21 Speed Range: 0-350 RPM

22 Maximum Power: 75 HP 23 Number of Poles: 12 13 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 Motor Service Factor: 1:1 2 Rated Current: XX A (rms)

3 Peak Current: 150 A

4 Rated Voltage: 277 V 5 Drive Inputs: 277 V, 3 phase, 60 Hz, 90A (rms max. continuous) 6 FIG. 10 shows a plot of speed vs. horsepower for high torque, low speed 7 permanent magnet motor 52. However, it is to be understood that the aforesaid 8 operational and performance characteristics just pertain to one embodiment of 9 permanent magnet motor 52 and that motor 52 may be modified to provide other 10 operational and performance characteristics that are suited to a particular application. 11 Referring to FIG. 11, there is shown a graph that shows “Efficiency %” versus 12 “Motor Speed (RPM)” for the fan drive system of the present invention and a prior art 13 fan drive system using a variable speed, induction motor. Curve 100 pertains to the 14 present invention and curve 102 pertains to the aforementioned prior art fan drive 15 system. As can be seen in the graph, the efficiency of the present invention is 16 relatively higher than the prior art fan drive system for motor speeds between about 17 125 RPM and about 350 RPM. Referring to FIG. 12, there is shown a plot of motor 18 torque versus motor speed. Permanent magnet motor 52 exhibits substantially 19 constant torque from about 70 RPM to about 425 RPM. 20 Referring to FIG. 9, in a preferred embodiment, the fan drive system of the 21 present invention further comprises a plurality of sensors 200, 202, 204, 206 and 208 22 that provide sensor signals to sensor signal inputs 82, 84, 86, 88 and 89, respectively, 23 of VFD device 50. Sensors 200 and 202 are positioned in proximity to bearings 90 14 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 and 92, respectively, of permanent magnet motor 52 in order to sense vibration and 2 heat. Sensor 204 is positioned on stator 94 of permanent magnet motor 52 to monitor 3 heat at stator 94. Sensors 206 and 208 are positioned downstream of the air flow 4 created by the fan of the ACHE system to measure airflow. For purposes of 5 simplifying FIG. 9, the fan of the ACHE system is not shown. All sensor output signals 6 applied to sensor signal inputs 82, 84, 86, 88 and 89 are inputted into user interface 7 62 of VFD device 50 and are then routed to an external processing device, such as 8 computer 300, via data port 80. Computer 300 includes a display screen device 302 9 that enables a user or operator to visually monitor the data outputted by sensors 200, 10 202, 204, 206 and 208. Computer 300 further includes a user interface, e.g. 11 keyboard, (not shown) that allows an operator to input commands. Computer 300 is 12 configured to implement a reliability algorithm using the data outputted by sensors 13 200, 202, 204, 206 and 208 and in response, output appropriate control signals that 14 are inputted into user interface 62 via data port 80. Such control signals can be used 15 to adjust the speed of motor 52. Thus, the sensors and computer 300 provide a 16 feedback loop that: 17 a) monitors vibrations and heat at the bearings of motor 52; 18 b) monitors heat at the stator of motor 52; 19 c) monitors airflow produced by the fan of the ACHE system; 20 d) provides a trim balance to compensate for fan-unbalance inertia on the 21 cooling tower structure; 22 e) alerts the operators to a “blade-out” situation and automatically reduces 23 the speed of motor 52; and 15 1 f) locks out a particular motor speed that creates resonance; 2013201697 23 Jan 2014 2 g) alerts the operator to imbalance such as ice accumulation on fan blades 3 and automatically initiates corrective action. 4 h) sensor data is used by system logic and software algorithms to provide 5 "cooling performance management" of the system. (Cooling performance 6 management provides real-time operating, reliability and performance data and 7 analysis of the cooling system to predict and schedule corrective action, 8 maintenance intervals and provide cooling performance feedback to the operator for 9 use in adjusting the process based on cooling performance). ίο Referring to FIG. 13, there is shown an ACHE system that is configured as an

11 induced draft ACHE and has the same general structural components as the ACHE 12 shown in FIG. 1, except for the prior art fan drive system which has now been 13 replaced with the fan drive system of the present invention, in this configuration, 14 variable frequency drive (VFD) device 50 and motor 52 are supported by support 15 member 18. Motor 52 is located below tube bundle 12. Fan 15 is positioned above 16 plenum 13 and rotates within fan ring 14 as described in the foregoing description. 17 One end of vertical shaft 16 is coupled to hub 15A and the other end is coupled to 18 shaft 56 with coupling 150. VFD device 50 is in electrical signal communication with 19 permanent magnet motor 52 via cables or wires 54. 20 Referring to FIG. 14, there is shown another ACHE system that is configured 21 as an induced draft ACHE and which uses the fan drive system of the present 22 invention. ACHE system 400 generally comprises a support structure that comprises

23 a plurality of support columns 402. Tube bundle 404 is supported by the ACHE 16 1 support structure. Plenum 406 is located above tube bundle 404. Fan ring 408 is 2013201697 23 Jan 2014 2 attached to plenum 406 and to the support structure of ACHE 400. Fan 410 rotates 3 within fan ring 408. Fan 410 includes hub 412. Plenum 406 has an upper portion 4 414to which motor 52 and VFD 50 are mounted. Shaft 56 of motor 52 is directly 5 coupled to hub 412 of fan 410. VFD device 50 is in electrical signal communication 6 with permanent magnet motor 52 via cables or wires 54. 7 Thus, the fan drive system of the present invention provides many 8 advantages and benefits, including: 9 a) elimination of many components found in the prior art fan drive systems, ίο such as gear boxes, pulleys, belts, sprockets, drive shafts, couplings, π bearings, shaft seals, etc.; 12 b) elimination of oil changes; ο c) significant reduction in service and maintenance; 14 d) ability to vary the speed of the permanent magnet motor over a relative 15 wide range of speeds; 16 e) ability to reverse direction of the permanent magnet motor without any 17 additional components; 18 f) consumption of significantly lower amounts of energy in comparison to prior 19 art fan drive systems; 20 g) easy retrofit with existing fan thereby eliminating need to construct new 21 ACHE cooling towers or structures; 22 h) significant reduction in the occurrence of cell outages; and 23 i) provides significantly more cooling capacity in comparison to prior art 17 1 gearbox-type fan drive. 2013201697 23 Jan 2014 2 The operational logic and system architecture of the present invention will 3 provide the ability to optimize the cooling tower for energy efficiency (e.g. at night 4 when it is cold) and to maximize cooling on hot days or when the process demands 5 additional cooling or to avoid fouling of auxiliary systems such as condenser and 6 heat exchangers ? Other significant advantages of the fan drive system of the present invention 8 are improved reliability, in comparison to prior art fan drive systems, "more air flow 9 per ampere" improves electrical efficiency in comparison to prior art systems, and 10 has a relatively smaller footprint due to the elimination the gear train offset thereby 11 providing more space for airflow per envelope and less structural obstructions and 12 passing flow frequency issues. The present invention provides direct-drive simplicity 13 with a simple, two-bearing, robust design. The fan drive system of the present 14 invention is relatively easier to install, maintain and remove. The simple, low-part 15 count design of the fan drive system of the present invention allows it to be "dropped 16 in" existing ACHE installations and eliminates tension-alignment devices that are 17 required by prior art fan drive systems using shafts, belts and pulleys. 18 The permanent magnet motor 52 is capable of providing constant high-torque 19 with infinitely variable speed control that allows an existing installation envelope to 20 be optimized for cooling effectiveness and high energy efficiency. The permanent 21 magnet motor 52 provides high, constant torque and electrical efficiency through-out 22 the entire variable speed range. 23 Thus, with the fan drive system of the present invention, it is easier to match 24 the required mass airflow of a particular application with 18 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 the high, constant torque and variable speed of permanent magnet motor 52. This is 2 in contrast to the time consuming, iterative approach previously taken to match motor 3 torque to a pulley (i.e. of a prior art fan drive system) to achieve the required torque to 4 rotate the fan while maintaining speed. The prior art fan drive systems using the 5 induction motor and the pulley or gearbox do not have the constant high torque 6 capacity through out the variable speed range of the fan drive system of the present 7 invention. Existing ACHE systems retrofitted with the fan drive system of the present 8 invention realize significant space savings as a result of the elimination of the prior art 9 complex mechanical system. The fan drive system of the present invention is IP 65 10 and/or IP 66 wet environment rated. Furthermore, the fan drive system of the present 11 invention may be integrated with a feedback loop to provide variable cooling load 12 control for cooling performance management. 13 The complex support structure and related “clap trap” of prior art drive systems 14 can result to “passing frequency” and airflow-interruption problems similar to those 15 exhibited in wet cooling towers. However, the direct drive system of the present 16 invention substantially eliminates such problems. . 17 High constant torque of the permanent magnet motor 52, regardless of speed, 18 allows for greater fan pitch and therefore airflow for a given plenum when compared to 19 the incumbent technology and induction motor. Thus, airflow and energy efficiently 20 can be optimized for given demand and outside condition for a given plenum (retrofit) 21 or new application. Thus, the present invention allows for greater design flexibility. 19 1 In accordance with the invention, permanent magnet motor 52 is a sealed 2013201697 23 Jan 2014 2 motor unlike prior art motor drive systems which are open to the environment and 3 susceptible to contamination from water, chemicals, dust and foreign particles. 4 Although the foregoing discussion is in terms of the applicability of the present 5 invention to the petroleum industry, it is to be understood that the present invention 6 provides benefits to any industry using ACHE cooling systems. Thus, the present 7 invention has applicability to many industries that consumer large amounts of energy 8 and are process intensive, such as the power generation, petro-chemical, pulp and 9 paper, chemical, glass, mining, steel, and aluminum industries. Other examples of ιό systems, industries and applications to which the present invention may apply 11 include air cooler fans, process coolers/condensers, gas coolers, gas compressor 12 inter/after coolers, steam condensers, seal/lube oil coolers, closed-loop cooling 13 water system coolers, HVAC, geothermal plant condensers, inter-coolers and after- 14 coolers, HVAC and Refrigeration Condensers, Air-Cooled Condensers, Air Cooled is Radiators for large stationary power applications such as gensets as well as 16 transportation applications such as railroad locomotives, marine power, mining and 17 large earth moving equipment. 18 It will thus be seen that the objects set forth above, among those elucidated in, 19 or made apparent from, the preceding description, are efficiently attained and, since 20 certain changes may be made in the above construction and/or method without 21 departing from the scope of the invention, it is intended that all matter contained in 22 the above description or shown in the accompanying drawing figures shall be 23 interpreted as illustrative only and not in a limiting sense. It is also to be understood 24 that the 20 2013201697 20 Mar 2013 WO 2009/120522 PCT/US2009/037242 1 following claims are intended to cover all of the generic and specific features of the 2 invention herein described and all statements of the scope of the invention which, as a 3 matter of language, might be said to fall therebetween. 4 21

Claims (78)

1. An industrial air-cooled heat exchanger for cooling fluids used in an industrial process, comprising: a support structure; a tube bundle supported by the support structure, the tube bundle being configured to receive fluids to be cooled; a motor comprising a rotatable shaft, a stator and bearings that locate and support the rotatable shaft; a fan connected to the rotatable shaft of the motor such that rotation of the rotatable shaft causes rotation of the fan which causes an airflow that cools the fluid flowing through the tube bundle; wherein the support structure positions the tube bundle, the fan and the motor at a predetermined height above ground level; a sensor to measure vibrations of the bearings and output signals representing the measured vibrations; and a variable motor-speed control device to generate electrical signals that cause rotation of the rotatable shaft of the motor at a predetermined rotational speed in order to rotate the fan, the variable motor-speed control device having an input for receiving control signals representing the predetermined rotational speed of the motor.

2. The industrial air-cooled heat exchanger according to claim 1 wherein the motor comprises a permanent magnet motor.

3. The industrial air-cooled heat exchanger according to claim 1 wherein the variable motor-speed control device comprises a variable frequency drive device.

4. The industrial air-cooled heat exchanger according to claim 1 further comprising an external processing device in electronic signal communication with the variable motor-speed control device and the sensor, the external processing device processing the signals outputted by the sensor and generating the control signals that are inputted into the input of the variable motor-speed control device.

5. The industrial air-cooled heat exchanger according to claim 4 further comprising sensors to measure heat of the stator and the bearings and output signals representing the measured heat, the external processing device processing the output signals representing the measured heat.

6. The industrial air-cooled heat exchanger according to claim 4 further comprising at least one airflow sensor to measure airflow produced by rotation of the fan and output signals representing the measured airflow, the external processing device processing the output signals representing the measured airflow.

7. The industrial air-cooled heat exchanger according to claim 1 wherein the external processing device comprises a computer.

8. The industrial air-cooled heat exchanger according to claim 7 further comprising a display device in data signal communication with the computer.

9. The industrial air-cooled heat exchanger according to claim 1 wherein the fan comprises a fan hub and the rotatable shaft of the motor is connected to the fan hub.

10. The industrial air-cooled heat exchanger according to claim 1 wherein the motor comprises a permanent magnet motor and the rotatable shaft is oriented in a substantially vertical position.

11. The industrial air-cooled heat exchanger according to claim 10 wherein the fan is positioned above the permanent magnet motor.

12. The industrial air-cooled heat exchanger according to claim 10 wherein the fan is positioned below the permanent magnet motor.

13. The industrial air-cooled heat exchanger according to claim 1 wherein the motor comprises a permanent magnet motor configured to have a speed range of 0-350 RPM.

14. The industrial air-cooled heat exchanger according to claim 1 wherein the efficiency of the motor is greater than 90% when the motor speed is between about 200 RPM and 350 RPM and wherein the motor has substantially constant torque between about 70 RPM and 425 RPM.

15. An industrial air-cooled heat exchanger for cooling fluids used in a process, comprising: a support structure; a tube bundle supported by the support structure, the tube bundle being configured to receive fluids to be cooled; a permanent magnet motor comprising a rotatable shaft, a stator and bearings that locate and support the rotatable shaft; a fan connected to the rotatable shaft of the permanent magnet motor such that rotation of the rotatable shaft causes rotation of the fan which causes an airflow that cools the fluid flowing through the tube bundle; wherein the support structure positions the tube bundle, the fan and the permanent magnet motor at a predetermined height above ground level; a sensor to measure vibrations of the bearings and output signals representing the measured vibrations; at least one airflow sensor to measure airflow produced by rotation of the fan and output signals representing the measured airflow; a variable motor-speed control device to generate electrical signals that cause rotation of the rotatable shaft of the permanent magnet motor at a predetermined rotational speed in order to rotate the fan, the variable motor-speed control device having an input for receiving control signals representing the predetermined rotational speed of the permanent magnet motor; and an external processing device external to the motor for processing the signals representing the measured vibrations and airflow and in response, generating the control signals for input into the variable motor-speed control device.

16. The industrial air-cooled heat exchanger according to claim 15 further comprising sensors to measure heat of the stator and the bearings and output signals representing the measured heat, the external processing device processing the output signals representing the measured heat.

17. An apparatus for cooling water used in an industrial process, comprising: a permanent magnet motor having a rotatable shaft, wherein the permanent magnet motor is oriented such that the rotatable shaft is substantially vertical and is oriented downward; a variable motor-speed control device to generate electrical signals that effect rotation of the rotatable shaft of the permanent magnet motor; a fan positioned beneath the permanent magnet motor, wherein the downward oriented rotatable shaft of the permanent magnet motor is directly connected to the fan such that rotation of the rotatable shaft causes rotation of the fan and the production of air-flow; a water distribution structure positioned beneath the fan so that air-flow produced by rotation of the fan flows throughout the water distribution structure, the water distribution structure receiving water to be cooled and uniformly distributing the water throughout the water distribution structure so as to the maximize the surface area between the air-flow produced by the fan and the water to be cooled; and a structure for supporting the permanent magnet motor, fan and water distribution structure at a predetermined height above ground level.

18. The apparatus according to claim 17 wherein the water distribution structure comprises a tube bundle.

19. The apparatus according to claim 17 wherein the variable motor-speed control device comprises a variable frequency drive device.

20. The apparatus according to claim 17 further comprising a sensor to measure vibrations of the bearings and output signals presenting the measured vibrations.

21. The apparatus according to claim 20 further comprising an external processing device in electronic signal communication with the variable motor-speed control device and the sensors, the external processing device processing the signals outputted by the sensors and generating the control signals that are inputted into the input of the variable motor-speed control device.

22. The apparatus according to claim 21 wherein the external processing device comprises a computer.

23. The apparatus according to claim 21 further comprising sensors to measure heat of the stator and the bearings and output signals representing the measured heat, wherein the external processing device processes the output signals representing the measured heat.

24. The apparatus according to claim 21 further comprising at least one airflow sensor to measure airflow produced by rotation of the fan and output signals representing the measured airflow, the external processing device processing the output signals representing the measured airflow.

25. An industrial air-cooled heat exchanger for cooling fluids used in an industrial process, comprising: a support structure; a tube bundle supported by the support structure, the tube bundle being configured to receive fluids to be cooled; a permanent magnet motor comprising a rotatable shaft, a stator and bearings that locate and support the rotatable shaft, the permanent magnet motor being positioned below the tube bundle; an elongate member attached to the rotatable shaft of the permanent magnet motor and extending through the tube bundle; a fan positioned above the tube bundle and connected to the elongate member such that rotation of the rotatable shaft causes rotation of the fan which causes an airflow that cools the fluid flowing through the tube bundle; wherein the support structure positions the fan, tube bundle and permanent magnet motor at a predetermined height above ground level; and a variable motor-speed control device to generate electrical signals that cause rotation of the rotatable shaft of the motor at a predetermined rotational speed in order to rotate the fan, the variable motor-speed control device having an input for receiving control signals representing the predetermined rotational speed.

26. The industrial air-cooled heat exchanger according to claim 25 further comprising a fan ring mounted to the support structure, wherein the fan rotates within the fan ring.

27. The industrial air-cooled heat exchanger according to claim 25 wherein the variable motor-speed control device comprises a variable frequency drive device.

28. The industrial air-cooled heat exchanger according to claim 25 further comprising a sensor to measure vibrations of the bearings and output signals representing the measured vibrations.

29. The industrial air-cooled heat exchanger according to claim 28 further comprising sensors to measure heat of the stator and the bearings and output signals representing the measured heat.

30. The industrial air-cooled heat exchanger according to claim 29 further comprising at least one air-flow sensor to measure airflow produced by rotation of the fan and output signals representing the measured air-flow.

31. The industrial air-cooled heat exchanger according to claim 30 further comprising an external processing device in electronic signal communication with the variable motor-speed control device and the sensors, the external processing device processing the signals outputted by the sensors and generating the control signals that are inputted into the input of the variable motor-speed control device.

32. An apparatus for cooling water used in an industrial process, comprising: a variable speed motor having a rotatable shaft, wherein the motor is oriented such that the rotatable shaft is substantially vertical and is oriented downward, the motor including a vibration sensor to sense vibrations of the bearings and output signals representing the sensed vibrations; a variable motor-speed control device to generate electrical signals that effect rotation of the rotatable shaft of the motor, the variable motor-speed control device having an input for receiving control signals representing the predetermined rotational speed of the motor; an external processing device in electronic signal communication with the variable motor-speed control device and the vibration sensor, the external processing device processing the signals outputted by the vibration sensor and generating the control signals that are inputted into the input of the variable motor-speed control device; a fan positioned beneath the motor, wherein the downward oriented rotatable shaft of the motor is directly connected to the fan such that rotation of the rotatable shaft causes rotation of the fan and the production of air-flow; a water distribution structure positioned beneath the fan so that air-flow produced by rotation of the fan flows throughout the water distribution structure, the water distribution structure receiving water to be cooled and uniformly distributing the water throughout the water distribution structure so as to the maximize the surface area between the air-flow produced by the fan and the water to be cooled; and a structure for positioning the motor, fan and water distribution structure at a predetermined height above ground level.

33. A forced-draft, air-cooled heat exchanger for cooling process fluids used in an industrial process, comprising: a main support structure; a tube bundle supported by the main support structure, the tube bundle configured to receive process fluids used in an industrial process; a plenum connected to the main support structure and positioned beneath the tube bundle, the plenum being configured to direct air-flow through the tube bundle; a fan assembly supported by the main support structure and positioned beneath the plenum, the fan assembly having a plurality of fan blades, wherein rotation of the fan produces an air-flow that is directed through the tube bundle by the plenum; a fan drive system supported by the main support structure and positioned beneath the fan assembly, the fan drive system comprising a permanent magnet motor comprising a motor casing, a stator and a rotatable shaft, the rotatable shaft being connected to the fan; and wherein the main support structure positions the tube bundle, plenum, fan assembly and fan drive system at a predetermined height above ground level.

34. The forced-draft air-cooled heat exchanger according to claim 33 wherein the fan drive system further comprises a device to generate electrical signals that effect rotation of the motor rotatable shaft at a rotational speed in order to rotate the fan.

35. The forced-draft air-cooled heat exchanger according to claim 34 wherein the device comprises a variable frequency drive device, the variable frequency drive device comprising electronic circuitry for receiving control signals that represent a particular rotational speed and generating electrical signals for the permanent magnet motor, wherein the electrical signals represent the rotational speed represented by the received control signals.

36. The forced-draft air-cooled heat exchanger according to claim 33 wherein the permanent magnet motor is a high-torque, low variable speed permanent magnet motor.

37. The forced-draft air-cooled heat exchanger according to claim 33 further comprising a sensor to measure vibrations at the bearings and output signals representing the measured vibrations.

38. The forced-draft air-cooled heat exchanger according to claim 33 further comprising a plurality of sensors to measure heat at the stator and at the bearings, the sensors outputting signals representing the measured heat.

39. The forced-draft air-cooled heat exchanger according to claim 33 further comprising a fan ring connected to the main support structure and positioned beneath the tube bundle, wherein the fan rotates within the fan ring.

40. An induced-draft, air-cooled heat exchanger for cooling high-temperature process fluids used in an industrial process, comprising: a main support structure; a tube bundle supported by the main support structure, the tube bundle configured to receive process fluids used in an industrial process; a plenum connected to the main support structure and positioned above the tube bundle; a fan assembly positioned above the plenum, the fan assembly comprising a plurality of fan blades and a fan shaft, wherein the fan shaft extends downward through the plenum and tube bundle, wherein rotation of the fan induces an air-flow through the tube bundle; a fan drive system supported by the main support structure and positioned beneath the tube bundle, the fan drive system comprising a permanent magnet motor comprising a motor casing, a stator and a rotatable shaft, the rotatable shaft being connected to the fan shaft; and wherein the main support structure positions the tube bundle, plenum, fan assembly and fan drive system at a predetermined height above ground level.

41. The induced-draft air-cooled heat exchanger according to claim 40 wherein the fan drive system further comprises a device to generate electrical signals that effect rotation of the rotatable shaft of the motor in order to rotate the fan.

42. The induced-draft air-cooled heat exchanger according to claim 41 wherein the device comprises a variable frequency drive device, the variable frequency drive device comprising electronic circuitry for receiving control signals that represent a particular rotational speed and generating electrical signals for the permanent magnet motor, wherein the electrical signals represent the rotational speed represented by the received control signals.

43. The induced-draft air-cooled heat exchanger according to claim 40 wherein the permanent magnet motor is a high-torque, low variable speed permanent magnet motor.

44. The induced-draft air-cooled heat exchanger according to claim 40 further comprising a sensor to measure vibrations of the fan assembly and output signals representing the measured vibrations.

45. The induced-draft air-cooled heat exchanger according to claim 40 further comprising sensors to measure heat at the stator and at the bearings and output signals representing the measured heat.

46. The induced-draft air-cooled heat exchanger according to claim 40 further comprising a fan ring connected to the main support structure and positioned above the plenum, wherein the fan rotates within the fan ring.

47. An induced-draft, air-cooled heat exchanger for cooling high-temperature process fluids used in an industrial process, comprising: a main support structure; a tube bundle supported by the main support structure, the tube bundle configured to receive process fluids used in an industrial process; a plenum connected to the main support structure and positioned above the tube bundle; a fan drive system supported by plenum and positioned above the tube bundle, the fan drive system comprising a permanent magnet motor comprising a motor casing, a stator and a rotatable shaft; a fan assembly positioned above the tube bundle, the fan assembly comprising a plurality of fan blades, wherein the rotatable shaft of the motor is connected to the fan and wherein rotation of the fan induces an air-flow through the tube bundle; and wherein the main support structure positions the tube bundle, plenum, fan drive system and fan assembly at a predetermined height above ground level.

48. The induced draft, air-cooled heat exchanger according to claim 47 wherein the permanent magnet motor is a high-torque, low variable speed permanent magnet motor and wherein the drive system further comprises a device to generate electrical signals that effect rotation of the rotatable shaft of the motor in order to rotate the fan.

49. The induced-draft air-cooled heat exchanger according to claim 48 wherein the device comprises a variable frequency drive device.

50. The induced draft, air-cooled heat exchanger according to claim 47 further comprising a fan ring connected to the plenum, wherein the fan rotates within the fan ring.

51. An induced air-cooled heat exchanger for use in a petroleum refinery for cooling fluids used in a petroleum refining process wherein the air-cooled heat exchanger has a tube bundle for receiving the fluids, and a fan that causes an airflow that cools the fluid flowing through the tube bundle, wherein the improvement comprises: a high-torque, low variable speed permanent magnet motor comprising a rotatable shaft directly connected to the fan, a stator and bearings that locate and support the rotatable shaft; a sensor to measure vibrations of the fan and output signals representing the measured vibrations; a variable frequency drive device to generate electrical signals that effect rotation of the rotatable shaft in order to rotate the fan, the variable frequency drive device controlling the speed, direction and torque of the high-torque, low variable speed permanent magnet motor, the variable frequency drive device comprising electronic circuitry for receiving control signals that represent a particular rotational speed and generating electrical signals for input to the permanent magnet motor, wherein the electrical signals represent the rotational speed represented by the received control signals; and an external processing device external to the permanent magnet motor and in electronic signal communication with the variable frequency drive device and the sensor, the external processing device processing signals outputted by the sensor and generating the control signals that are inputted into the input of the variable frequency drive device.

52. The induced air-cooled heat exchanger according to claim 51 wherein the improvement further comprises sensors to measure heat of the stator and bearings and output signals representing the measured heat, wherein the external processing device processes the signals representing the measured heat.

53. A heating, ventilation and/or air-conditioning (HVAC) system comprising: a fan: a variable speed permanent magnet motor comprising a rotatable shaft connected to the fan a stator and bearings that locate and support the rotatable shaft; a sensor to measure vibrations of the bearings and output signals representing the measured vibrations; a variable frequency drive device to generate electrical signals that effect rotation of the rotatable shaft of the permanent magnet motor in order to rotate the fan, wherein the variable frequency drive device controls the speed, direction and torque of the high-torque, low variable speed permanent magnet motor, the variable frequency drive device being configured to receive control signals that represent a desired rotational speed of the permanent magnet motor, and in response, generate electrical signals for input into the permanent magnet motor to cause the permanent magnet motor to operate at a rotational speed that is substantially the same as the desired rotational speed ; and an external processing device external to the permanent magnet motor and in electronic signal communication with the variable frequency drive device and the sensor, the external processing device processing signals outputted by the sensor and generating the control signals that are inputted into the input of the variable frequency drive device.

54. The HVAC system according to claim 53 further comprising: sensors to measure heat of the stator and the bearings and output signals representing the measured heat; and at least one airflow sensor to measure airflow produced by the fan and output signals representing the measured airflow.

55. The HVAC system according to claim 54 wherein the external processing device comprises a computer, wherein the computer is in electronic signal communication with the variable frequency drive device and all of the sensors and is programmed to process the signals outputted by all of the sensors and generate the control signals for input into the variable frequency drive device in order to adjust the speed of the permanent magnet motor in response to the processed signals.

56. An industrial air-cooled heat exchanger for cooling fluids used in an industrial process, comprising: a support structure; a tube bundle supported by the support structure, the tube bundle being configured to receive fluids to be cooled; a variable speed motor comprising a rotatable shaft, a stator and bearings that locate and support the rotatable shaft; a fan connected to the rotatable shaft of the motor such that rotation of the rotatable shaft causes rotation of the fan which causes an airflow that cools the fluid flowing through the tube bundle; a variable motor-speed control device to generate electrical signals that effect rotation of the rotatable shaft of the motor, the variable motor-speed control device having an input for receiving control signals representing the predetermined rotational speed of the motor; wherein the support structure positions the tube bundle, the fan and the motor at a predetermined height above ground level; a sensor to measure vibrations of the bearings and output signals representing the measured vibrations; sensors to measure heat of the stator and the bearings and output signals representing the measured heat [.] ; at least one airflow sensor to measure the airflow produced by rotation of the fan and output signals representing the measured airflow; a computer external to the motor and in electronic signal communication with the variable motor-speed control device and the sensors, the computer being programmed to process the signals outputted by all of the sensors and generate the control signals for input into the variable motor-speed control device in order to adjust the speed of the motor in response to the processed signals.

57. An industrial air-cooled heat exchanger (400) for cooling fluids used in an industrial process, wherein the industrial air-cooled heat exchanger has a tube bundle (22, 404) for receiving the fluids, a fan (25, 410) that causes an airflow that cools the fluid flowing through the tube bundle (22, 404) and a fan drive system for causing rotation of the fan (25, 410), characterized in that the drive system is a direct-drive system comprising: a high-torque, low variable speed permanent magnet motor (52) comprising a rotatable shaft (56) connected to the fan (25, 410), a stator (94) and a bearing system comprising bearings (90, 92) that locate and support the rotatable shaft (56); a variable frequency drive device (50) to generate electrical signals that effect rotation of the rotatable shaft (56) of the high-torque, low variable speed permanent magnet motor (52) in order to rotate the fan (25, 410), wherein the variable frequency drive device (50) is configured to receive control signals that represent a desired rotational speed of the high-torque, low variable speed permanent magnet motor (52), and in response, generate electrical signals for input into the high-torque, low variable speed permanent magnet motor (52) to cause the high-torque, low variable speed permanent magnet motor (52) to operate at a rotational speed that is substantially the same as the desired rotational speed; a plurality of sensors (200, 202) in proximity to the bearings (90, 92) for measuring vibrations and heat of the bearings (90, 92) and outputting signals representing the measured vibrations and measured heat; a plurality of sensors ( 204) for measuring heat of the stator (94) and outputting signals representing the measured heat; at least one airflow sensor (206, 208) for measuring airflow produced by the fan (25, 410) and outputting signals representing the measured airflow; and a computer (300) in electronic signal communication with the variable frequency drive device (50), wherein the computer (300) processes the signals representing (i) the measured heat of the motor stator (94) and bearings (90, 92), (ii) the measured vibrations of bearings (90, 92), and (iii) the measured airflow and generates the control signals for input into the variable frequency drive device (50) in order to adjust the speed of the high-torque, low speed permanent magnet motor (52) in response to the processed signals.

58. The industrial air-cooled heat exchanger according to claim 57 further comprising a support structure (21,28, 402) that supports the air-cooled heat exchanger at a height above ground.

59. The industrial air-cooled heat exchanger according to claim 57 wherein the fan (25, 410) comprises a fan hub (25A, 412) and the rotatable shaft (56) of the high-torque, low variable speed permanent magnet motor (52) is connected to the fan hub (25A, 412).

60. The industrial air-cooled heat exchanger according to claim 57 wherein the computer (300) is programmed to generate control signals that reduce the rotational speed of the high torque, low variable speed permanent magnet motor (52) if the computer (300) determines, as a result of processing the measured vibrations, a pending fan blade-out situation exists.

61. The industrial air-cooled heat exchanger according to claim 60 wherein the computer (300) is programmed to perform a reliability algorithm on the signals outputted by the all of the sensors (200, 202, 204, 206, 208).

62. The industrial air-cooled heat exchanger according to claim 61 wherein the computer (300) generates control signals, in response to the implementation of the reliability algorithm, for input into the variable frequency drive device (50) in order to adjust the speed of the high torque, low variable speed motor (52).

63. The industrial air-cooled heat exchanger according to claim 58 wherein the computer (300) is configured to generate control signals to the variable frequency drive device (50) to cause reverse rotation of the high-torque, permanent magnet motor (52).

64. The industrial air-cooled heat exchanger according to claim 57 wherein the high torque, low variable speed permanent magnet motor (52) is configured to have a speed range of 0-350 RPM.

65. The industrial air-cooled heat exchanger according to claim 57 wherein the high torque, low variable speed permanent magnet motor (52) is configured to have an efficiency between 85% and 95% when the motor speed is between about 125 RPM and 350 RPM.

66. The industrial air-cooled heat exchanger according to claim 57 wherein the high torque, low variable speed permanent magnet (52) provides substantially constant torque from about 70 RPM to 350 RPM.

67. The industrial air-cooled heat exchanger according to claim 57 wherein the computer (300) includes a display screen device (302) that enables a user or operator to visually monitor the signals outputted by sensors (200, 202, 204, 206 and 208).

68. The industrial air-cooled heat exchanger according to claim 57 wherein the bearings (90, 92) are sealed bearings.

69. A method of installing a direct-drive system in an industrial air-cooled heat exchanger for cooling fluids used in an industrial process, wherein the industrial aircooled heat exchanger has a tube bundle for receiving the fluids, a fan that causes an airflow that cools the fluid flowing through the tube bundle, and a preexisting fan-drive system for rotating the fan, wherein the preexisting fan-drive fan system is configured either as a drive system utilizing a belt, pulley and motor, or a drive system utilizing a gear box, a drive shaft that drives the gearbox and a motor that drives the drive shaft, the method comprising: disconnecting the preexisting fan drive system; removing the preexisting fan drive system; providing a high-torque, low variable speed permanent magnet motor comprising a rotatable shaft, a stator and a bearing system comprising bearings that locate and support the rotatable shaft, the high-torque, low variable speed permanent magnet motor further comprising a plurality of heat sensors for measuring heat of the stator and bearings and outputting signals that represent the measured heat, the high-torque, low variable speed permanent magnet motor further comprising a vibration sensor in proximity to the bearings to measure the vibrations of the bearings and output signals that represent the measured vibrations; connecting the rotatable shaft of the high-torque, low variable speed permanent magnet motor to the fan; providing a variable frequency drive device for providing electrical signals to the high-torque, low variable speed permanent magnet motor to control the rotational speed of the high-torque, low variable speed permanent magnet motor; electrically connecting the variable frequency drive device to the high-torque, low variable speed permanent magnet motor; positioning an air-flow sensor to measure air-flow produced by the fan and output signals that represent the measured air-flow; providing a computer comprising a processor programmed to process the signals representing (i) the measured heat of the motor stator and bearings, (ii) the measured vibrations of the motor bearings, and (iii) the measured airflow, wherein the processor is configured to generate electrical signals for input into the variable frequency drive device in order to adjust the speed of the high-torque, low speed variable permanent magnet motor in response to the processing of the signals; and electrically connecting the computer to the variable frequency drive device, the air-flow sensor, the heat sensors and the vibration sensor.

70. The method according to claim 69 wherein step of connecting the rotatable shaft of the high-torque, low variable speed permanent magnet motor comprises the step of connecting the rotatable shaft to the fan hub.

71. A method of operating an industrial air-cooled heat exchanger (400) for cooling fluids used in an industrial process, wherein the industrial air-cooled heat exchanger comprises a tube bundle (22, 404) for receiving the fluids, a fan (25, 410) that causes an airflow that cools the fluid flowing through the tube bundle (22, 404), a direct-drive system for causing rotation of the fan (25, 410), wherein the direct-drive system comprises a high-torque, low variable speed permanent magnet motor (52) comprising a rotatable shaft (56) connected to the fan (25, 410), a stator (94) and bearings (90, 92) that locate and support the rotatable shaft (56), the direct-drive system further comprising a variable frequency drive device (50) to generate electrical signals that effect rotation of the rotatable shaft (56) of the high-torque, low variable speed permanent magnet motor (52) in order to rotate the fan (25, 410), wherein the variable frequency drive device (50) is configured to receive control signals that represent a desired rotational speed of the high-torque, low variable speed permanent magnet motor (52), and in response, generate electrical signals for input into the high-torque, low variable speed permanent magnet motor (52) to cause the high-torque, low variable speed permanent magnet motor (52) to operate at a rotational speed that is substantially the same as the desired rotational speed, wherein the method comprises the steps of: measuring vibrations of the bearings (90, 92) and providing signals representing the measured vibration; measuring heat of the stator (94) and the bearings (90, 92) and providing signals representing the measured heat; measuring airflow produced by the fan (25, 410) and providing signals representing the airflow; and processing the signals representing (i) the measured heat of the motor stator (94) and bearings (90, 92), (ii) the measured vibrations of the motor bearings (90, 92), and (iii) the measured airflow; and generating control signals for input into the variable frequency drive device (50) in order to adjust the speed of the high-torque, low variable speed permanent magnet motor (52) in response to the processed signals.

72. The method according to claim 71 further comprising the step of generating control signals for input into the variable frequency drive device (50) to cause reverse rotation of the high-torque, low variable permanent magnet motor (52).

73. A heating, ventilation and/or air-conditioning (HVAC) system comprising: a fan: a high-torque, low variable speed permanent magnet motor (52) comprising a rotatable shaft (56) connected to the fan, the high-torque, low variable speed permanent magnet motor (52) comprising a stator (94) and bearings (90, 92) that locate and support the rotatable shaft (56); and a variable frequency drive device (50) to generate electrical signals that effect rotation of the rotatable shaft (56) of the high-torque, low variable speed permanent magnet motor (52) in order to rotate the fan, wherein the variable frequency drive device (50) is configured to receive control signals that represent a desired rotational speed of the high-torque, low variable speed permanent magnet motor (52), and in response, generate electrical signals for input into the high-torque, low variable speed permanent magnet motor (52) to cause the high-torque, low variable speed permanent magnet motor (52) to operate at a rotational speed that is substantially the same as the desired rotational speed.

74. The HVAC system according to claim 73 further comprising a plurality of sensors (200, 202) in proximity to the bearings (90, 92) for measuring vibrations and heat of the bearings (90, 92) and outputting signals representing the measured vibrations.

75. The HVAC system according to claim 74 further comprising a sensor ( 204) for measuring heat of the stator (94) and outputting signals representing the measured heat.

76. The HVAC system according to claim 75 further comprising at least one airflow sensor (206, 208) for measuring airflow produced by the fan and outputting signals representing the measured airflow.

77. The HVAC system according to claim 76 further comprising a computer (300) in electronic signal communication with the variable frequency drive device (50), wherein the computer (300) processes the signals representing (i) the measured heat of the motor stator (94) and bearings (90, 92), (ii) the measured vibrations of bearings (90, 92), and (iii) the measured airflow and generates the control signals for input into the variable frequency drive device (50) in order to adjust the speed of the high-torque, low speed permanent magnet motor (52) in response to the processed signals.

78. The HVAC system according to claim 73 wherein bearings (90, 92) are sealed bearings.