CN102155859B - U-shaped gravity assisted heat pipe for freezing system - Google Patents

Abstract

A U-shaped gravity heat pipe used in a refrigeration system in the technical field of heat exchangers, comprising: an evaporation section, a condensation section, a U-shaped elbow and an inner casing, one end of the evaporation section and the condensation section are respectively connected to the pipe of the heat exchanger, The other ends of the evaporating section and the condensing section are respectively connected to the two ends of the U-shaped elbow, and the inner sleeve is welded inside the heat pipe. The invention can ensure that the heat pipe of the heat pipe heat exchanger works stably and maintains better heat transfer capacity under the condition of long length. The application of the invention can improve the dehumidification effect of the air conditioning system and play the role of energy saving.

Description

U-shaped gravity heat pipe for refrigeration system

technical field

The invention relates to a device in the technical field of heat exchangers, in particular to a U-shaped gravity heat pipe used in a refrigeration system.

Background technique

Heat pipe heat exchange is a high-efficiency heat conduction element that uses phase change for heat transfer, and has been widely used in aerospace and various industrial heat recovery applications. At present, heat pipes are mainly divided into gravity heat pipes and capillary-assisted horizontal heat pipes in terms of liquid return methods. There is generally no capillary structure inside the gravity heat pipe, and the condensed liquid relies on gravity to return from the upper part of the heat pipe to the evaporation section at the lower part of the heat pipe.

In the refrigeration dehumidification system, the dehumidification process is mainly carried out on the surface cooler used as the evaporator of the refrigeration system or the central air conditioner. The temperature of the treated air is first reduced to the dew point temperature on the surface cooler, and then cooled to dehumidify, and passed through the surface cooler. Finally, the temperature drops, usually through the evaporator of the refrigeration system or a special heater, and then enters the air-conditioned environment. Through a reasonable form of heat exchange, heat exchange between the air in front of the surface cooler and the dehumidified air can reduce the pre-cooling load of the surface cooler on the treated air, and also reduce the heating of the treated air after the surface cooler heater heating load. As a structure with high thermal conductivity, the heat pipe can realize the above functions by arranging the heat pipes at the front and rear ends of the surface cooler, and reduce the sensible heat cooling load of the treated air. This technology has been applied in many projects at home and abroad. However, in many occasions, the evaporator or surface cooler of the refrigeration system used for cooling is placed vertically, the air duct is horizontal, and the heat exchangers in the air duct are arranged closely. It is designed to be placed in a horizontal U shape, where one arm of the U bend is slightly higher than the other arm, and operates as a gravity heat pipe. That is, the evaporating end and condensing end of the heat pipe are arranged at the front and back of the surface cooler and close to the surface cooler, and the level of the evaporating end is only slightly lower than that of the condensing end. This is the most energy-saving heat pipe form in the dehumidification process. Due to the existence of the U-shaped elbow during the operation of this type of heat pipe, the low-speed reflux condensate and the evaporated high-speed steam flowing to the condensation end interact in this area, and part of the reflux liquid is difficult to return to due to the gas-carrying effect. To the evaporating end, thus affecting the heat transfer capacity of the heat pipe. This effect is much higher in the U-bend region than in the straight pipe section. Especially for the case of longer heat exchange tubes, it is easy to cause the carrying limit earlier due to the interaction of gas and liquid in the U-shaped area, which affects the performance of the heat exchanger and affects the operating economy of the system.

In the literature "Experiment on Improving the Dehumidification Performance of Small Dehumidifiers Using Heat Pipe Heat Exchangers" (Proceedings of the Twelfth National Heat Pipe Conference, October 2010), the heat pipe operation characteristics of the U-shaped heat pipe structure used in the dehumidifier are discussed. Through numerical simulation, it is found that during the operation of the heat pipe, the gas-liquid vortex flow in the adiabatic elbow obviously affects the fluid transport process in the evaporation and condensation sections, thereby causing fluctuations in the phase interface. The interface is unstable, and the gas-liquid temperature fluctuates accordingly. Therefore, the heat and mass transfer at the phase interface in the evaporation and condensation sections is unstable.

Contents of the invention

Aiming at the above-mentioned deficiencies in the prior art, the present invention provides a U-shaped gravity heat pipe used in a refrigeration system. The device can ensure that the heat pipe of the heat pipe heat exchanger works stably and maintains a good temperature when the heat pipe heat exchanger is long. heat transfer capacity. The application of the invention can improve the dehumidification effect of the air-conditioning system and play the role of energy saving.

The present invention is achieved through the following technical solutions. The present invention includes: an evaporating section, a condensing section, a U-shaped elbow and an inner casing, wherein: one end of the evaporating section and the condensing section are respectively connected to the pipeline of the heat exchanger, and the evaporating section and the condensing section The other end of the section is respectively connected with the two ends of the U-shaped elbow, and the inner sleeve is welded inside the heat pipe.

The inner sleeve fitting adopts a non-porous plate or a porous plate, the shape of the inner sleeve fitting matches the shape of the U-shaped elbow of the heat pipe, and the wall thickness is 0.2-1.0 mm. The inner sleeve fitting and the inner wall of the U-bend form a ring Shaped space, the distance between the outer wall of the inner casing and the inner wall of the outer tube is 1/20-1/5 of the inner diameter of the outer tube.

The outer walls of the U-shaped heat pipes in the evaporating section and the condensing section are provided with heat exchange fins.

The inner casing of the present invention has the function of separating the gas and liquid flowing in opposite directions inside. During normal operation, in the U-shaped elbow, the condensed liquid mainly flows back to the evaporation section in the space between the inner casing and the U-shaped pipe. The steam is restricted by the inner casing when it moves, and has less influence on the condensate moving in the opposite direction. The invention can be applied to occasions where there is no obvious height difference between the heating and cooling sections.

The heat exchanger formed by the invention can be used in an air-conditioning treatment box of an air-conditioning system to improve the dehumidification effect of a surface cooler and play a role in energy saving.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

FIG. 2 is a cross-sectional view of Embodiment 1. FIG.

FIG. 3 is a cross-sectional view of Embodiment 2. FIG.

Detailed ways

The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following the described embodiment.

Example

As shown in Figure 2, this embodiment includes: an evaporating section 1, a condensing section 2, a U-shaped elbow 3 and an inner casing 4, wherein: one end of the evaporating section 1 and the condensing section 2 are respectively connected to the pipe of the heat exchanger, and the evaporation The other ends of section 1 and condensing section 2 are respectively connected to two ends of U-shaped elbow 3 , and the inner casing 4 is placed in the U-shaped elbow to form an annular space with its inner wall.

The evaporating section 1, the condensing section 2 and the U-shaped elbow 3 can be arranged with enhanced heat exchange fins outside the tubes according to heat exchange requirements.

As shown in FIG. 3 , the inner casing member 4 adopts a perforated plate.

This embodiment can isolate the gas and liquid flow channels in the U-shaped region of the heat pipe to a certain extent, so that the backflow liquid will not be greatly affected by the counterflow of high-speed air flow.

Claims (4)

1. A U-shaped gravity heat pipe for a refrigeration system, comprising: an evaporation section, a condensation section, a U-shaped elbow and an inner sleeve fitting, characterized in that: one end of the evaporation section and the condensation section are respectively connected to the pipeline of the heat exchanger, The other ends of the evaporating section and the condensing section are respectively connected to the two ends of the U-shaped elbow, and the inner sleeve is welded inside the heat pipe. The inner wall of the curved pipe forms an annular space, and the distance between the outer wall of the inner casing and the inner wall of the outer pipe is 1/5 of the inner diameter of the outer pipe. 2. The U-shaped gravity heat pipe used in a refrigeration system according to claim 1, characterized in that, the inner sleeve member adopts a non-porous plate or a porous plate. 3. The U-shaped gravity heat pipe for refrigeration system according to claim 1, characterized in that, the wall thickness of the inner casing member is 0.2-1.0mm. 4. The U-shaped gravity heat pipe for refrigeration system according to claim 1, characterized in that, the outer walls of the U-shaped heat pipes in the evaporating section and the condensing section are provided with heat exchange fins.

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