JPH0445739B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method of controlling refrigerant flow rate in a refrigeration or heat pump cycle.

(Prior art) A compressor, a condenser, a refrigerant controller, a low-pressure liquid receiver, an evaporator, etc. are connected through a refrigerant pipe, and the liquid refrigerant stored in the low-pressure liquid receiver is transferred between the evaporator and the low-pressure liquid receiver. In a so-called liquid recirculation type (liquid pump type) refrigeration cycle in which the liquid is circulated by a pump during the cooling process, conventionally, the rotation speed of the pump is controlled according to changes in the load. Nothing has been done.

In other words, the system described in Utility Model Application Publication No. 54-132850 controls the compressor using an indoor thermostat when the load fluctuates, and also controls the refrigerant tank (low-pressure liquid receiver).
Although the compressor is also controlled by changes in the liquid level of the liquid refrigerant in the refrigerant tank, the rotation speed of the pump in the refrigerant tank is not controlled in accordance with the load.

In addition, those published in Japanese Patent Application Laid-Open No. 48-91638 are
When the load fluctuates, the discharge gas temperature on the inlet side of the condenser and the liquid refrigerant temperature on the outlet side are detected and the proportional control valve is controlled so that the two temperatures always maintain a constant temperature difference. The rotation speed of the pump that circulates the liquid refrigerant in the liquid separation mechanism (low-pressure liquid receiver) between the evaporator and the evaporator is not controlled according to the load.

As mentioned above, the conventional technology does not control the pump for circulating liquid refrigerant according to load fluctuations.
Control in response to load fluctuations is not performed quickly enough,
In addition, the front and back of the pump are connected by a bypass to return the liquid refrigerant from the discharge side to the suction side of the pump, and since the pump itself is constantly running at an appropriate constant rotation speed, it consumes extra pump power and reduces economical operation. I can't do it enough.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned problems of the prior art. The purpose of this invention is to ensure stable operation and economical operation by quickly controlling the refrigeration or heat pump cycle by controlling the rotational speed of the pump.

[Structure of the invention]

(Means for Solving the Problems) The refrigerant flow rate control method in a refrigeration or heat pump cycle of the present invention is configured by the following means in order to solve the above problems.

First invention: A positive displacement two-phase flow expander is connected to an induction motor,
The rotation of the induction motor is electrically converted and controlled according to the refrigerant liquid level in the low-pressure liquid receiver, and the induction motor is operated as a generator to recover power, thereby controlling the refrigerant flow rate during the expansion process. controlling the refrigerant liquid level in the low-pressure receiver by connecting a positive displacement liquid pump to the electric motor in a liquid recirculation cycle that circulates the refrigerant liquid in the low-pressure receiver to and from a load; The rotation of the electric motor is electrically converted and controlled according to the temperature and pressure of the refrigerant, or the temperature on the load side, thereby controlling the refrigerant flow rate.

Second invention A positive displacement two-phase flow expander and a positive displacement liquid pump are coaxially connected to each other, an induction motor is connected thereto, and the rotation of the induction motor is controlled by electricity according to the temperature and pressure of the refrigerant or the temperature on the load side. controlling the refrigerant flow rate during the expansion process of the expander and controlling the refrigerant liquid level in the low-pressure liquid receiver by converting and controlling the induction motor as an electric motor; The refrigerant flow rate is controlled by controlling the rotation of the positive displacement liquid pump in a liquid recirculation cycle that circulates the refrigerant liquid between the refrigerant and the load section.

(Operation) The rotation of the induction motor connected to the positive displacement two-phase flow expander is electrically converted and controlled according to the refrigerant liquid level in the low-pressure liquid receiver, and the induction motor is operated as a generator to generate power. The refrigerant liquid level in the low pressure liquid receiver is controlled by controlling the refrigerant flow rate during the expansion process by recovering the refrigerant liquid. On the other hand, the rotation of the electric motor that drives the positive displacement liquid pump in a liquid recirculation cycle that circulates the refrigerant liquid in the low-pressure liquid receiver between the load part and the load part is controlled electrically depending on the temperature and pressure of the refrigerant or the temperature on the load side. The refrigerant flow rate is controlled by performing conversion control (first invention).

The rotation of an induction motor coaxially connected to a positive displacement two-phase flow expander and a positive displacement liquid pump is controlled by the temperature of the refrigerant,
The induction motor is operated as an electric motor by electrical conversion control according to the pressure or temperature on the load side, and the refrigerant liquid level in the low-pressure receiver is controlled by controlling the refrigerant flow rate during the expansion process of the expander. controlled. Further, the refrigerant flow rate is controlled by controlling the rotation of a positive displacement liquid pump in a liquid recirculation cycle that circulates the refrigerant liquid in the low-pressure liquid receiver to and from the load section (second invention).

(Embodiment) FIG. 1 shows a first embodiment of carrying out the method of the present invention, in which 1 is a compressor, 2 is a condenser, 3a is a screw type two-phase flow expander, 4 is an evaporator, 5 is a low pressure liquid receiver, 6 is a positive displacement liquid pump, and 7a is an expander 3a.
8 is an electric motor connected to the induction motor; 9a is a frequency converter that controls the rotation of the induction motor 7a;
b is a frequency converter that controls the rotation of the electric motor 8.

In the A cycle, the refrigerant compressed by the compressor 1 is cooled and condensed by the heat radiation load 16 in the condenser 2, flows into the expander 3a from the high-pressure liquid inlet port 19 through the liquid pipe 12, and is expanded. , the induction motor 7a works as a generator, recovers the energy lost as friction loss in the conventional throttle valve type as power, flows out from the discharge port 20, passes through the communication pipe 13, and is sent to the low-pressure liquid receiver. 5. The controller 26 is for controlling the refrigerant liquid level in the low-pressure receiver 5 at a constant level, and controls the frequency by the frequency converter 9a according to the rise and fall of the refrigerant liquid level to control the rotation of the induction motor 7a. Act to control.

In cycle B, the refrigerant liquid in the low-pressure liquid receiver 5 passes through the liquid pipe 14 and flows into the positive displacement liquid pump 6 from the inlet 21, flows out from the outlet 22, is introduced into the evaporator 4, and is subjected to evaporative action due to the heat load 17. After performing this, the liquid returns to the low-pressure liquid receiver 5 again from the communication pipe 15. The positive displacement liquid pump 6 performs inverter control by a frequency converter 9b inserted between the electric motor 8 and the commercial power source 25. That is, the controller 27 is operated according to the temperature and pressure of the refrigerant or the temperature on the load side, and the frequency is controlled by the frequency converter 9b, so that the electric motor 8
The rotation of the positive displacement liquid pump 6 is controlled to adjust the amount of refrigerant liquid supplied to the evaporator 4. If the positive displacement liquid pump 6 is of a screw type, a particularly highly accurate discharge amount corresponding to a flow meter can be guaranteed.

Note that it is of course possible to provide a plurality of expanders 3a and perform a number control operation at the same time.

In the embodiment shown in FIG. 2, the low pressure liquid receiver 5
Since the control of the refrigerant liquid level and the control of the heat load in the evaporator 4 are controls that both change proportionally to each other, the
are made coaxial, and the induction motor 7a and the motor 8 are made common to form the induction motor 7b.Therefore, the controllers 26, 27 and frequency converters 9a, 9b are also made common to form the controller 28 and the frequency converter 9c, respectively. It is also possible to operate the controller 28 according to the temperature and pressure of the refrigerant or the temperature on the load side as shown in FIG.

Furthermore, since a positive displacement type two-phase flow expander is used as the expander, better results can be achieved in terms of thermal efficiency than in the case where this is used as an airfoil turbine. That is, in Fig. 3, when using a blade-type turbine, the point is C, and if an expansion valve is used, it can be made to point G, but when a positive displacement two-phase flow expander is used, the gas and liquid inside the expander As a result of the efficient and good operation of the mixture, the expansion process of the high-pressure refrigerant liquid can be made similar to FD, which is more efficient than when using a blade-type turbine.
At the same time as power recovery increases by GD (iG−
iD) can increase the amount of heat pumped by the cycle.

Furthermore, in the embodiments shown in FIGS. 1 and 2,
Although the frequency converters 9a to 9c are frequency converters, they are not limited to such an inverter type, and any type that can electrically convert and control the rotation of the induction motors 7a, 7b and the electric motor 8 may be used. - A variable speed controller such as a chopper system can also be used.

〔Effect of the invention〕

The rotation of an induction motor connected to a positive displacement two-phase flow expander is electrically converted and controlled according to the refrigerant liquid level in a low-pressure liquid receiver to operate the induction motor as a generator and recover power. Since the refrigerant flow rate during the expansion process can be controlled by this, the refrigerant liquid level in the low-pressure liquid receiver can be controlled. On the other hand, the rotation of the electric motor that drives the positive displacement liquid pump in a liquid recirculation cycle that circulates the refrigerant liquid in the low-pressure liquid receiver between it and the load section is determined by the temperature of the refrigerant.
Since the conversion can be controlled electrically according to the pressure or the temperature on the load side, the flow rate of the refrigerant can be controlled (first invention).

The rotation of an induction motor coaxially connected to a positive displacement two-phase flow expander and a positive displacement liquid pump is controlled by the temperature of the refrigerant,
By electrically converting and controlling the induction motor according to the pressure or temperature on the load side and operating the induction motor as an electric motor, the flow rate of refrigerant in the expansion process of the expander can be controlled. Liquid level can be controlled. In addition, since the rotation of the positive displacement liquid pump in the liquid recirculation cycle that circulates the refrigerant liquid in the low-pressure liquid receiver to and from the load section can be controlled, the refrigerant flow rate can be controlled (second invention).

Furthermore, the positive displacement liquid pump of the liquid recirculation type cycle corresponds to a flow meter, and the discharge amount is maintained accurately, so that the refrigerant flow rate can be well adjusted.

[Brief explanation of the drawing]

1 and 2 are flow sheet diagrams of different embodiments for carrying out the method of the present invention, and FIG. 3 is a P-i diagram for explaining the effects of the method of the present invention. . 3a, 3b... Expander, 5... Low pressure liquid receiver, 6... Positive displacement liquid pump, 7a, 7b... Induction motor, 8... Electric motor, 9a, 9b, 9c... Frequency converter as an electrical conversion controller.

Claims (1)

[Scope of Claims] 1. A positive displacement two-phase flow expander is connected to an induction motor, and the rotation of the induction motor is electrically converted and controlled according to the refrigerant liquid level in a low-pressure receiver, and the induction motor is By operating as a generator and recovering power, the refrigerant flow rate during the expansion process is controlled and the refrigerant liquid level in the low-pressure receiver is controlled, while the refrigerant liquid in the low-pressure receiver is used as a load section. A positive displacement liquid pump in a liquid recirculation type cycle that circulates between 1. A refrigerant flow rate control method in a refrigeration or heat pump cycle, the method comprising: controlling the refrigerant flow rate in a refrigeration or heat pump cycle. 2 A positive displacement two-phase flow expander and a positive displacement liquid pump are coaxially connected to an induction motor, and the rotation of the induction motor is electrically converted according to the temperature and pressure of the refrigerant or the temperature on the load side. The induction motor is operated as an electric motor to control the refrigerant flow rate during the expansion process of the expander to control the refrigerant liquid level in the low-pressure liquid receiver, and to load the refrigerant liquid in the low-pressure liquid receiver. A refrigerant flow rate control method in a refrigeration or heat pump cycle, characterized in that the refrigerant flow rate is controlled by controlling the rotation of a positive displacement liquid pump in a liquid recirculation type cycle in which the liquid is circulated between the refrigeration and heat pump cycles.