CN107091545A - A kind of falling film evaporator suitable for low pressure refrigerant - Google Patents

Abstract

The invention discloses a kind of falling film evaporator suitable for low pressure refrigerant, including evaporator tube, demister, distributor and liquid barrier, the evaporator tube is divided into the return-air chamber that the first chamber and remainder of side are constituted below the demister by the demister and the liquid barrier；First chamber is divided into superposed gas-liquid separation chamber and the evaporation cavity positioned at bottom by the distributor, and the return-air chamber is connected with the evaporation cavity bottom.The falling film evaporator of the present invention overcomes the defect of refrigerant distributor in traditional falling film evaporator, can be applied to the system using low pressure refrigerant, and it has the advantages that, and simple in construction, heat transfer efficiency is high, refrigerant charge is few.

Description

A Falling Film Evaporator Suitable for Low Pressure Refrigerants

technical field

The invention relates to the technical field of refrigeration, in particular to a falling film evaporator with a gas-liquid separation chamber suitable for low-pressure refrigerants.

Background technique

Falling film evaporators have been used in more and more refrigeration and air conditioning units due to their higher heat transfer efficiency and less refrigerant charge. The falling film evaporator generally adopts the structure shown in FIG. 1 , which includes an evaporator outlet pipe 25 , a liquid inlet pipe 24 , a refrigerant distributor 22 and an evaporator tube bundle 23 . The gas-liquid two-phase refrigerant enters the evaporator through the liquid inlet pipe 24, and after passing through the refrigerant distributor 22, the refrigerant liquid drops on the evaporator tube bundle 23 for evaporation and heat exchange, and the generated refrigerant gas is discharged through the evaporator outlet pipe 25 into the compressor. The refrigerant distributor 22 in FIG. 1 is a key component in the falling film evaporator. In order to realize the uniform distribution of the refrigerant to the evaporator tube bundle, it is generally required to have a sufficiently large pressure difference between the inner and outer sides of the refrigerant distributor. For example, in a refrigeration unit using a medium-high pressure refrigerant (such as R134a, etc.), the pressure difference between the inside and outside of the refrigerant distributor usually needs to reach 150-300kPa.

The low-pressure refrigerant R1233zd(E) has attracted more and more attention in the refrigeration and air-conditioning industry due to its advantages of environmental protection and high efficiency. Table 1 shows the R1233zd (E) Compared with the evaporation pressure and condensation pressure of R134a, it can be seen that the difference between the evaporation pressure and condensation pressure of R1233zd (E) is only 23.1% of that of R134a. For low-pressure refrigerants such as R1233zd(E), the refrigerant distributor in the traditional falling film evaporator obviously cannot meet the requirements.

Table 1 Typical refrigeration conditions

Therefore, there is a need for a falling film evaporator that can more effectively and evenly distribute refrigerant to heat exchange tubes and is suitable for low-pressure refrigerant environments.

Contents of the invention

The purpose of the present invention is to provide a falling film evaporator suitable for low-pressure refrigerants, which overcomes the defects of traditional falling film evaporators applied to refrigerant distributors in low-pressure refrigerant environments, and solves the problem of falling film evaporators for low-pressure refrigerants. The problem of refrigerant distribution in film evaporators can be applied to systems using low-pressure refrigerants.

In one aspect, the present invention provides a falling film evaporator suitable for low-pressure refrigerants, comprising an evaporator cylinder, further comprising a mist eliminator, a distributor, and a liquid baffle, the mist eliminator and the liquid baffle The plate divides the evaporator cylinder into the first chamber located on the lower side of the demister and the return air chamber composed of the remaining part; the distributor divides the first chamber into the gas-liquid separation chamber located on the upper part and the evaporation chamber located at the lower part, the return air chamber communicates with the bottom of the evaporation chamber.

In one embodiment, the falling film evaporator further includes an evaporator inlet pipe, and the evaporator inlet pipe communicates with the gas-liquid separation chamber.

In one embodiment, falling film tube bundles are arranged in the evaporation chamber.

In one embodiment, the falling film evaporator further includes an evaporator outlet pipe, and the evaporator outlet pipe communicates with the return air chamber.

In one embodiment, the outlet pipe of the evaporator communicates with the suction port of the compressor.

In one embodiment, the distributor is arc-shaped along the axial direction of the evaporator cylinder, high in the middle and low at both ends.

In one embodiment, the demister is a screen or a Z-plate.

In one embodiment, a liquid separation groove is arranged below the inlet pipe of the evaporator, and the liquid separation groove extends to both ends of the evaporator cylinder along the axial direction of the evaporator cylinder.

In one embodiment, the distributor is a porous media material or a porous plate, such as a porous plate or wire mesh.

In another aspect, the present invention also provides a method of using the above-mentioned falling film evaporator, the method comprising:

The gas-liquid two-phase refrigerant enters the gas-liquid separation chamber from the inlet pipe of the evaporator, and in the gas-liquid separation chamber, due to the effect of gravity, the gas-liquid two-phase refrigerant is separated;

The gaseous refrigerant enters the air return cavity after passing through the demister;

The liquid refrigerant is deposited on the bottom of the gas-liquid separation chamber to form a liquid level at a certain height, and through the distributor, it evenly drops onto the falling film tube bundle for evaporation and heat exchange;

The gaseous refrigerant generated by evaporation enters the air return chamber through the opening at the bottom of the liquid baffle, merges with the gaseous refrigerant that enters the return air chamber through the demister, and passes through the evaporator outlet pipe into the compressor suction port.

In one embodiment, after the refrigerant enters the liquid distribution tank, liquid is deposited in the liquid distribution tank, and when the liquid fills the liquid distribution tank, it overflows from the top of the liquid distribution tank.

In another embodiment, after the refrigerant enters the gas-liquid separation chamber through the evaporator inlet pipe, the liquid flows along the axial direction of the evaporator cylinder to both ends of the evaporator cylinder.

The present invention includes any combination of any one or more of the embodiments described above.

The invention provides a falling-film evaporator with a gas-liquid separation chamber suitable for low-pressure refrigerants, which has the advantages of simple structure, high heat transfer efficiency, less refrigerant charge and the like.

It should be understood that both the foregoing general description and the following detailed description are exemplary illustrations and explanations, and should not be used as limitations on the claimed content of the present invention.

Description of drawings

With reference to the accompanying drawings, further objects, functions and advantages of the invention will be clarified through the following description of the embodiments of the invention, wherein:

Fig. 1 schematically shows a schematic structural view of a traditional falling film evaporator;

Fig. 2 schematically shows a kind of falling film evaporator structural representation with gas-liquid separation chamber;

Figure 3 shows a schematic diagram of a porous plate that can be used as a distributor;

Figure 4 shows a schematic diagram of a wire mesh that can be used as a distributor;

Figure 5 shows a schematic diagram of a Z-shaped plate that can be used as a mist eliminator;

Fig. 6 schematically shows another kind of falling film evaporator structure diagram with gas-liquid separation chamber, and a liquid separation tank is arranged below the inlet pipe of the evaporator;

Fig. 7 schematically shows the structure of another falling film evaporator with a gas-liquid separation chamber, and the distributor is arc-shaped.

detailed description

The objects and functions of the invention and methods for achieving the objects and functions will be clarified by referring to the exemplary embodiments. However, the invention is not limited to the exemplary embodiments disclosed below; it can be implemented in various forms. The essence of the description is only to help those skilled in the relevant art comprehensively understand the specific details of the invention.

Hereinafter, embodiments of the invention will be described with reference to the drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

Embodiment one

A schematic structural diagram of a falling film evaporator provided by the present invention is shown in Figure 2, including an evaporator cylinder 210, and also includes a mist eliminator 202, a distributor 204, and a liquid baffle 209, and the mist eliminator 202 and a liquid baffle The plate 209 divides the evaporator cylinder 202 into the first chamber located on the side below the demister 202 and the return air chamber 207 composed of the remaining part; the distributor 204 divides the first chamber into a gas-liquid separation chamber located on the upper part of the distributor 204 203 and the evaporation chamber 206 located at the lower part of the distributor 204, and the return air chamber 207 communicates with the bottom of the evaporation chamber 206. The two-phase refrigerant enters the gas-liquid separation chamber 203 from the evaporator inlet pipe 201, and in the gas-liquid separation chamber 203, the gas-liquid refrigerant is separated due to the action of gravity. The gaseous refrigerant enters the gas return chamber 207 after passing through the demister 202 arranged at the top of the gas-liquid separation chamber 203 . The liquid refrigerant is deposited on the distributor 204 at the bottom of the gas-liquid separation chamber 203 to form a liquid level at a certain height, and through the distributor 204, it evenly drops onto the falling film tube bundle 205 for evaporation and heat exchange, and the gaseous refrigeration generated by evaporation The refrigerant enters the air return cavity 207 through the opening at the bottom of the liquid baffle plate 209, and after joining the gaseous refrigerant that enters the return air cavity 207 through the demister 202, enters the compressor suction port through the evaporator outlet pipe 208.

Wherein, the cross-sectional shape of the evaporator cylinder 210 may be a rectangle as shown in FIG. 2 , or a circle or other shapes. The liquid baffle 209 runs through the entire cylinder along the axial direction of the evaporator cylinder 210, and can be arranged vertically as shown in Figure 2, or in other non-vertical arrangements, and its cross-sectional shape can be rectangular, arc or other shapes .

Wherein, the distributor 204 can adopt the perforated plate 302 shown in FIG. 3 (with holes 301 on the perforated plate), the steel wire mesh shown in FIG. 4 or other porous medium materials. The refrigerant liquid is deposited on the distributor 204, and when a certain liquid level is reached, the amount of liquid entering the gas-liquid separation chamber 203 and the amount of liquid flowing out of the gas-liquid separation chamber 203 and entering the evaporation chamber 206 are balanced.

Assuming that the pressure drop across the distributor 204 is ΔP, the liquid level h in the gas-liquid separation chamber can be expressed as:

Among them, ρ is the refrigerant liquid density, and g is the gravitational acceleration.

The design of the refrigerant distributor needs to satisfy that the pressure drop ΔP generated by flowing through the distributor 204 is within a certain range, so that a certain liquid level height h can be guaranteed to meet the requirements of refrigerant distribution uniformity, and it can also meet the requirements of using low pressure. Refrigerant system design requirements.

The demister 202 can use a Z-shaped plate as shown in FIG. 5 , or a porous medium material such as a steel wire mesh of the distributor 204 . When the refrigerant gas flows through the demister 202 , the entrained liquid foam adheres to the demister 202 , and falls back into the gas-liquid separation chamber 203 after reaching a certain amount.

Embodiment two

Fig. 6 is the second embodiment of the present invention. Compared with the first embodiment, a liquid separator 607 arranged below the evaporator inlet pipe 601 is added in the evaporator cylinder 611, and the liquid separation groove 607 is along the evaporator cylinder 611. The axial direction runs through the entire evaporator cylinder 611 . After the refrigerant enters the liquid-separating tank 607 , the liquid is deposited in the liquid-separating tank 607 , and when the liquid fills the liquid-separating tank 607 , it will overflow from the top of the liquid-separating tank 607 . Compared with Embodiment 1, the addition of the liquid separation tank 607 is beneficial to the uniformity of refrigerant distribution along the axial direction of the evaporator cylinder 611 . In this embodiment, 602 is a demister, 603 is a gas-liquid separation chamber, 604 is a distributor, 605 is a falling film tube bundle, 606 is an evaporation chamber, 608 is a return air chamber, 609 is an evaporator outlet pipe, and 610 is baffle.

Embodiment three

Fig. 7 is the third embodiment of the present invention. Compared with the first embodiment, the distributor 702 is arc-shaped along the axial direction of the evaporator cylinder, the middle is high, and the two ends are low. After the refrigerant enters the gas-liquid separation chamber 701 from the evaporator inlet pipe 704, the liquid will flow along the axial direction of the evaporator cylinder to both ends of the cylinder, which is beneficial to the uniform distribution of the refrigerant along the axial direction. In this example, 705 is a demister and 703 is an evaporation chamber.

Other embodiments of the invention will be apparent to and understood by those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The description and examples are considered exemplary only, with the true scope and spirit of the invention defined by the claims.

Claims (9)

1. a kind of falling film evaporator with gas-liquid separation chamber suitable for low pressure refrigerant, including evaporation Device cylinder (210,611), it is characterised in that also including demister (202,602,705), divide Orchestration (204,604,702) and liquid barrier (209,610), the demister and the gear liquid The evaporator tube is divided into the first chamber and remainder of the side below the demister by plate The return-air chamber (207,608) of composition；First chamber is divided into superposed gas by the distributor Liquid disengagement chamber (203,603,701) and the evaporation cavity (206,606,703) positioned at bottom, institute Return-air chamber is stated to connect with the evaporation cavity bottom.

2. falling film evaporator according to claim 1, it is characterised in that the falling film evaporation Device also includes evaporator inlet pipe (201,601,704), the evaporator inlet pipe and the gas Liquid disengagement chamber is connected.

3. falling film evaporator according to claim 1, it is characterised in that in the evaporation cavity It is provided with falling liquid film tube bank (205,605).

4. falling film evaporator according to claim 1, it is characterised in that the falling film evaporation Device also includes evaporator outlet pipe (208,609), and the evaporator outlet pipe connects with the return-air chamber It is logical.

5. falling film evaporator according to claim 1, it is characterised in that the distributor edge The axial direction of the evaporator tube is curved, and middle high, two ends are low.

6. falling film evaporator according to claim 1, it is characterised in that demister is filter screen Or Z-shaped plate.

7. falling film evaporator according to claim 1, it is characterised in that the evaporator enters A point liquid bath (607), axial direction side of the described point of liquid bath along the evaporator tube are provided with below mouth pipe To the two ends for extending to the evaporator tube.

8. falling film evaporator according to claim 1 or 5, it is characterised in that the distribution Device is porous media material or porous plate (302).

9. use the method for the falling film evaporator according to any one of claim 1-8, methods described bag Include：

Gas-liquid two-phase cold-producing medium enters the gas-liquid separation chamber by the evaporator inlet pipe, described Gas-liquid separation intracavitary, due to the effect of gravity, gas-liquid two-phase cold-producing medium is separated；

After the gaseous refrigerant is via the demister, into the return-air chamber；

Liquid refrigerant is deposited on the bottom of the gas-liquid separation chamber, forms the liquid level of certain altitude, Via the distributor, equably drop onto and carry out evaporation and heat-exchange in the falling liquid film tube bank；

Evaporate the gaseous refrigerant of generation, the opening through the liquid barrier bottom, into the return-air Chamber, with entering through the demister after the gaseous refrigerant of the return-air chamber converges through the evaporator Outlet enters compressor air suction mouthful.