JPH0258559B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Detailed Industrial Description] The present invention relates to a heat transfer device for heating, cooling, drying, etc., and particularly to a jet heat transfer device with high heat transfer efficiency.

[Prior Art] Jet heat transfer devices are used in heating devices, coolers, dryers, etc., and devices with higher heat transfer coefficients are considered more advantageous.

The heat transfer coefficient improves as the flow rate increases, but spraying a large amount of fluid to improve the heat transfer coefficient results in a loss of heat and power energy.

Thus, the value of the heat transfer coefficient, or heat transfer efficiency, under constant flow rate determines the performance of the heat transfer device.

In general, this jet heat transfer device uses a parallel flow method, in which heat is transferred by flowing the fluid in the same direction as the traveling direction of the object to be heated, and a countercurrent method, in which the fluid flows in the opposite direction, parallel to the surface to be heated. This method has been attracting a lot of attention in recent years because it is advantageous in that it can increase heat transfer efficiency compared to methods that transfer heat through a continuous flow.

[Objective] The present invention aims to further improve heat transfer efficiency than conventional jet heat transfer devices.

[Structure] To briefly explain the main points of the present invention, it is composed of a jet port A, a discharge port B, and a heat transfer target surface C as shown in FIG. We improved the conventional device in which the path was more than three times the width of the nozzle opening, and installed a small gap between the nozzle A and the discharge port B and the surface C of the heat transfer target, as shown in Figure 2. By adding fluid throttle plates D facing each other in parallel planes, it is intended to improve heat transfer.

That is, the jet heat transfer device of the present invention is characterized in that a slit-shaped discharge port is provided parallel to the longitudinal direction of the slit-shaped jet port, and a guide roller is fixed at a position facing the slit-shaped jet port. A diaphragm plate is provided between the ejection port and the discharge port so as to face the heat transfer target running on the guide roller in a parallel plane, and the opening width of the ejection port and the diaphragm plate are The ratio of the width of the gap to the surface of the heat transfer target is set to 1/2 or more, and the velocity of the fluid flowing from the jet port along the surface of the heat transfer target is maintained at a high speed.

[Effect] Next, the operation of the present invention will be explained.

Fig. 3 is a diagram showing the flow velocity distribution of the fluid ejected from the ejection port in a conventional device along the surface of the transmitted object.In this example, the average wind speed V= 40mm/sec Distance between the nozzle and the object to be dried Z = 24mm Nozzle opening width L = 3mm The wind speed near the surface of the object to be dried is a little less than 1/2 that of the nozzle, but as it moves away from the surface Therefore, the wind speed decreases rapidly, and the wind speed near the surface of the object to be dried decreases as the distance from the nozzle increases.

On the other hand, as shown in Figure 4 A, B, and C,
In contrast to the conventional example shown in Fig. B, the distance Z between the nozzle and the object to be dried is narrowed as shown in Fig. B, and a diaphragm plate D is provided so as to crush the upper part of the wind speed distribution diagram, that is, the part where the velocity is low. When this is done, the wind speed flows at a high speed that is almost uniform between the distance Z between the aperture plate and the object to be dried. This example shows the case where Z/L=2. Further, the diagram C shows a case where Z/L=1 or less.

In this way, between the nozzle (spout port) and the discharge port, the diaphragm plate D, which faces the object to be dried in a plane, is placed between the object to be dried (the surface of the object to be heated) C, with a small gap, for example, Z/L<1.
When installed under such conditions, as shown in Figure 5, the wind speed flows from the nozzle toward the outlet with an almost uniform velocity distribution along the surface of the material to be dried, and with almost no deceleration. Naturally, it is clear that the heat transfer efficiency is improved compared to the conventional one.

According to the above example, in the general conventional nozzle shown in FIG. 4A, almost no flow occurs in the portion where Z'/L>2 (Z' is the distance upward from the heat transfer surface). Therefore, even if Z/L>2, the aperture plate has almost no effect. Therefore, as shown in Fig. 4B, when Z/L = 2, the effect of the aperture plate is obtained, and in the case of Z/L = 1 or less, as shown in Fig. A good effect can be obtained.

Note that when Z/L=1, the air flow path is the nozzle opening width B.
(because the flow separates from the nozzle to the left and right), and the wind speed flowing through the gap between the aperture plate and the heat transfer surface becomes 1/2. Further, when Z/L<1, the wind speed becomes 1/2 or more of the nozzle wind speed, so the effect of heat transfer enhancement becomes more significant.

Further, the guide roller provided at a position facing the jet port suppresses the pressure applied in a direction perpendicular to the traveling direction of the surface of the heat transfer target when the fluid flowing from the jet port hits the surface of the heat transfer target. Therefore, stable running is possible without increasing the tension applied to the heat transfer object, and the width between the heat transfer object and the aperture plate can be kept constant, improving the heat transfer coefficient. be able to.

[Example] Next, the present invention will be described in detail using an example of application to a drying device.

Conventionally, when coating ink, adhesive, etc. on paper, metal foil, plastic film, etc., and evaporating and drying, a jet type drying apparatus is usually used to increase the drying speed.

One example is the arch-type and flat-type drying apparatuses shown in FIGS. 6 and 7.
A coating liquid 4 such as ink or adhesive is applied between the rolls 2 and 3, and the liquid is run on guide rolls 5 and sent to a drying device 6. Inside the drying device 6, there are spaced apart at regular intervals, for example, 100~
A duct 8 having a nozzle 7 is provided every 4000 mm, and this duct 8 is
The hot air a sent through the nozzle 7 is blown out toward the strip 1 as a jet stream at a constant blowing velocity, for example, 10 to 50 m/sec, thereby drying the strip 1.

The air used for drying is exhausted from exhaust ports 9 provided on both sides of the nozzle 7. The opening width of the ejection port of the nozzle 7 is about 1 to 10 mm, and the distance from the tip of the nozzle 7 to the strip 1 is about 10 to 50 mm.

In contrast, in the present invention, as shown in FIG. 8, in order to narrow the hot air flow path compared to the conventional device, the belt-like material
A diaphragm plate 10 is provided that faces parallel to the diaphragm plate 10, and the ratio of the gap between the diaphragm plate 10 and the strip 1 to the opening width of the jet nozzle of the nozzle 7 is set to 2 or less, and the fluid flows from the spout port along the strip 1. The speed is maintained at a high speed. Note that the nozzle 7 and the aperture plate 10 may be integrated here.

The hot air a jetted from the nozzle 7 hits the strip on the guide roller 5 located directly below the jet nozzle, is forcibly squeezed by the throttle plate 10, and flows almost parallel to the strip 1 at high speed. The flow further collides with each other directly under the discharge ports 9 provided on both sides of the nozzle 7 or near the nozzle 7, and is then discharged from the discharge ports 9. The collision between this high-speed parallel flow and the flow immediately below the discharge port promotes the destruction of the film between the hot air a and the strip 1 between the nozzle discharge ports, improving the heat transfer coefficient, that is, further improving the drying ability.

[Effects of the Invention] The present invention has the above-described configuration, and the air flow path between the jet port and the discharge port is three times or more the width of the jet port opening in the conventional system, whereas the Since the shape is narrowed to less than twice the exit opening width, the following two effects can be brought about.

One is to force the wasteful fluid, which conventionally flows outside the vicinity of the boundary film between the fluid and the object to be transferred, into the vicinity of the boundary membrane in the flow part almost parallel to the heat transfer surface,
By increasing the flow velocity near the boundary film, destruction of the boundary film can be promoted, and as a result, the heat transfer coefficient can be increased.

Another method is to actively reduce the turbulence caused by the collision of the flows from the jet ports on both sides directly below the discharge port by narrowing the flow path to actively create a film between the fluid and the object to be transferred. Promote destruction of the membrane by bringing it closer to the area,
As a result, the heat transfer coefficient can be increased.

Furthermore, by arranging the guide rollers to face the jet nozzles, the distance between the heat transfer target and the aperture plate, which runs linearly between the guide rollers, can be kept constant.
It can bring about the effect of improving heat transfer coefficient.

Next, the effects of the present invention will be explained in more detail using specific examples and comparative examples.

Specific Example When the drying apparatus of the present invention shown in Fig. 8 was measured under the following conditions: distance between nozzle and strip 1.5 mm, nozzle opening width 3 mm, nozzle pitch 200 mm, hot air blowing speed 43 m/sec, hot air and strip were measured. The average heat transfer coefficient during this period was 219 [Kcal/hr・m ²・℃].

In addition, in order to locally grasp the degree of improvement in the heat transfer coefficient, the local heat transfer coefficient was determined, and it was as shown in FIG. 9.

Comparative Example 1 In the conventional drying apparatus shown in Fig. 7, measurements were made under the following conditions: distance between nozzle and strip 24 mm, nozzle opening width 3 mm, nozzle pitch 200 mm, hot air blowing speed 43/sec. The average heat transfer coefficient during this period was 148 [Kcal/hr·m ² ·°C], and the local heat transfer coefficient at that time was as shown in Figure 9.

Comparative Example 2 Using a conventional drying device (Figure 7), the nozzle and web were brought close together and measured under the following conditions: distance between nozzle and strip 1.5 mm, nozzle opening width 3 mm, nozzle pitch 200 mm, and hot air blowing speed 43 m/sec. However, the average heat transfer coefficient between the hot air and the strip was 187 [Kcal/hr·m ² ·°C], and the local heat transfer coefficient at that time was as shown in Figure 9.

In this way, with conventional nozzles, by reducing the distance between the nozzle and the material to be dried from 24 mm (8 times the nozzle opening width, which was previously considered the best dimension) to 1.5 mm, the average heat transfer coefficient was improved by 26%. I found out what to do.

Furthermore, by providing the fluid restricting plate 10 according to the present invention, the distance between the nozzle and the object to be dried is 17% compared to a conventional nozzle in which the distance between the nozzle and the object to be dried is 1.5 mm, and the distance between the nozzle and the object to be dried in the conventional nozzle is 24 mm. An astonishing 48% improvement.

It was also found that the local heat transfer coefficient was improved over the entire area between the nozzle and the exhaust port.

As described above, according to the present invention, the heat transfer coefficient can be further improved significantly compared to the conventional nozzle method, which is generally considered to have a high heat transfer coefficient.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of the conventional device, Fig. 2 is a schematic explanatory diagram of the present invention device, Fig. 3 is a wind speed distribution diagram under the nozzle in the conventional device, and Fig. 4 A, B, and C are the conventional and the present invention. A diagram showing the wind speed distribution under the nozzle of the device, FIG. 5 is a wind speed distribution diagram of a preferred example of the present invention, FIG. 6 is a perspective view showing an example of a conventional drying device, and FIG. 7 is a conventional drying device 8 is a sectional view showing an example of the vicinity of the nozzle of the drying device according to the present invention, and FIG. 9 is a diagram showing an example of the heat transfer coefficient distribution of the conventional drying device and the present invention. It is. A...Blowout port, B...Discharge port, C...Heat transfer target surface, D...Fluid throttle plate, a...Hot air, b...Exhaust air, 1...Band-shaped object (material to be dried), 2... ... Coating plate cylinder, 3... Coating impression cylinder, 4... Coating liquid, 5... Guide roll, 6... Drying device, 7... Nozzle, 8
...Duct, 9...Discharge port, 10...Hot air diaphragm plate.

Claims (1)

[Claims] 1. A slit-shaped discharge port is provided parallel to the longitudinal direction of the slit-shaped discharge port, a guide roller is fixedly provided at a position facing the slit-shaped discharge port, and a heat transfer target running on the guide roller and a A throttle plate is provided between the jet port and the discharge port so as to face each other in parallel planes, and the ratio of the opening width of the jet port to the width between the throttle plate and the surface of the heat transfer target is set to 1/2. A jet heat transfer device as described above, characterized in that the velocity of the fluid flowing from the spout along the surface of the heat transfer target body is maintained at a high speed.