Electric compression type-absorption type heat pump unit of coupling plate type evaporator

Abstract

The invention relates to the technical field of waste heat recovery, in particular to an electric compression type-absorption type heat pump unit of a coupling plate type evaporator, which comprises an electric heat pump evaporator, a compressor, an absorption type heat pump absorber, an absorption type heat pump evaporator, an absorption type heat pump generator, an absorption type heat pump condenser and a solution heat exchanger, the electric heat pump evaporator and the absorption heat pump evaporator are the same in structure. According to the electric compression-absorption heat pump unit of the coupling plate type evaporator, heat of a low-temperature heat source can be effectively extracted to heat a medium-temperature heat source for heat supply, an electric heat pump condenser is omitted through the arrangement of the electric heat pump evaporator and the absorption heat pump evaporator, and the cost is reduced. The effects of electric heat pump refrigerant condensation and absorption heat pump refrigerant evaporation are directly achieved in the absorption heat pump evaporator, high heat exchange efficiency is achieved, intermediate circulating water in a conventional scheme does not need to be used, and heat loss, equipment manufacturing cost and operation cost are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery, and in particular to an electric compression-absorption heat pump unit coupled with a plate evaporator. Background Art

[0002] At present, there are many low-temperature heat sources with relatively low temperatures in the field of waste heat recovery for heating. For example, heat is extracted from the soil by using buried pipes. The temperature difference between the low-temperature heat source and the heat required for heating is relatively large. It is neither possible to directly use an absorption heat pump to extract heat, nor can the outlet temperature of the hot water side of a conventional electric heat pump meet the heating requirements. Therefore, a combined operation method of an electric + absorption heat pump is considered to achieve the purpose. Generally, a scheme is to set up a circulating water and a circulating pump between the condenser of the electric heat pump and the evaporator of the absorption heat pump. This circulating water absorbs heat in the condenser of the electric heat pump and then releases heat in the evaporator of the absorption heat pump. However, this method has three main problems. One is the loss of heat transfer temperature difference, which reduces the temperature of the circulating water entering the evaporator of the absorption heat pump and the evaporation temperature, increasing the cost of the absorption heat pump. The second is that the circulating water pump increases the power consumption and operating cost. The third is that the electric heat pump also needs to be provided with a condenser, which is generally of a shell-and-tube structure, with high cost and large floor area.

[0003] At present, the evaporators of various electric compression refrigerators / heat pumps and absorption refrigerators / heat pumps generally adopt a shell-and-tube structure. The refrigerant is immersed or film-fed outside the refrigerant tube, and the low-temperature heat source (generally water, steam or other working fluids) flows inside the tube. There are also some electric compression refrigerators that adopt a dry evaporator, that is, the refrigerant evaporates inside the tube and the low-temperature heat source flows outside the tube. Limited by the physical properties, flow rate and resistance requirements of the media on both sides, the heat transfer coefficient of this shell-and-tube heat exchanger is relatively low. In order to improve the heat transfer coefficient, special processing is required on both the inside and outside of the heat transfer tube to enhance heat transfer. Therefore, this type of heat exchanger generally has a large volume, requires a lot of metal for the shell, high cost of the heat transfer tube, and a large refrigerant filling amount. In addition, this shell-and-tube heat exchanger is generally of a fixed tube sheet structure, and the heat transfer tube needs to be connected to the tube sheet by welding, expansion or a combination of expansion and welding. For the above reasons, the traditional shell-and-tube evaporator has low heat transfer efficiency, large volume, high cost, and great difficulty in processing and manufacturing.

[0004] Based on this, the present invention provides a plate evaporator and an electric compression-absorption heat pump unit coupled with the plate evaporator that can improve the heat transfer efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide an electric compression-absorption heat pump unit coupled with a plate evaporator, which can effectively extract the heat of a low-temperature heat source to heat a medium-temperature heat source with high heat transfer efficiency.

[0006] The present invention provides an electric compression-absorption heat pump unit with a coupled plate evaporator, which includes an electric heat pump evaporator, a compressor, an absorption heat pump absorber, an absorption heat pump evaporator, an absorption heat pump generator, an absorption heat pump condenser, and a solution heat exchanger; the electric heat pump evaporator and the absorption heat pump evaporator have the same structure, both being plate rising film evaporators. The evaporator includes a housing, and a pair of heat exchange plates is arranged inside the housing. A heat source inlet and a heat source outlet are provided on the pair of heat exchange plates. A refrigerant is provided between the housing and the pair of heat exchange plates. A refrigerant vapor outlet is provided at the top of the housing, and a liquid refrigerant inlet is provided at the bottom of the housing.

[0007] The heat source inlet of the electric heat pump evaporator is connected to a low-temperature heat source. The refrigerant vapor outlet of the electric heat pump evaporator is connected to the compressor, the heat source inlet of the absorption heat pump evaporator, the heat source outlet of the absorption heat pump evaporator, and the liquid refrigerant inlet of the electric heat pump evaporator in sequence through a pipeline. The refrigerant vapor outlet of the absorption heat pump evaporator is connected to the absorption heat pump absorber, the solution heat exchanger, the absorption heat pump generator, the absorption heat pump condenser, and the liquid refrigerant inlet of the absorption heat pump evaporator in sequence through a pipeline. The absorption heat pump generator is connected to the solution heat exchanger and the absorption heat pump absorber in sequence through a pipeline. The medium to be heated is discharged after being heated through the absorption heat pump absorber and the absorption heat pump condenser through a pipeline. The inlet of the absorption heat pump generator is connected to a driving heat source.

[0008] Preferably, multiple pairs of heat exchange plates are arranged in parallel inside the housing. Two vertically opposite interfaces are provided on the upper side of each pair of heat exchange plates, and the interfaces are respectively connected to the heat source inlet and the heat source outlet.

[0009] Preferably, each pair of heat exchange plates is composed of two plate sheets, and a medium channel is provided inside. The peripheries of the two plate sheets are connected by laser, resistance seal welding or brazing.

[0010] Preferably, a liquid retaining device is provided inside the housing. The liquid retaining device is located at the top of the housing. The liquid retaining device is composed of several vertically arranged baffles, and the refrigerant vapor outlet is located above the liquid retaining device.

[0011] Preferably, a liquid level gauge is provided inside the housing, and the height of the refrigerant liquid level in the evaporator is lower than the height of the pair of heat exchange plates.

[0012] Preferably, the liquid level gauge adopts one of a differential pressure liquid level gauge, a float ball liquid level gauge, a magnetic flap liquid level gauge, a tuning fork liquid level gauge, and a guided wave radar liquid level gauge.

[0013] Preferably, a valve is provided on the pipeline connected to the liquid refrigerant inlet.

[0014] Preferably, the valve is one of an electric valve, a solenoid valve, a float valve, and a thermostatic expansion valve.

[0015] Preferably, the refrigerant in the electric heat pump evaporator shell is Freon.

[0016] Preferably, the refrigerant in the absorption heat pump evaporator shell is water.

[0017] Beneficial effects:

[0018] The present invention provides an electric compression-absorption heat pump unit coupled with a plate evaporator, which can effectively extract the heat of a low-temperature heat source to heat a medium-temperature heat source for heating. By setting an electric heat pump evaporator and an absorption heat pump evaporator, the electric heat pump condenser is omitted, and the condensation of the electric heat pump refrigerant and the evaporation of the absorption heat pump refrigerant are directly achieved in the absorption heat pump evaporator, with high heat exchange efficiency, without using the intermediate circulating water in the conventional scheme, reducing heat loss, equipment cost, and operation cost.

[0019] The evaporator adopted in the present invention is a plate rising-film evaporator, which combines the advantages of plate heat transfer surface condensation and boiling, and rising-film heat transfer, with excellent heat exchange effect. After testing in the lithium bromide absorption heat pump evaporator, its heat transfer coefficient is more than twice that of the conventional shell-and-tube heat transfer tube structure, that is, the heat transfer area can be saved by more than half, saving the material consumption for heat exchange, making the evaporator more compact and smaller in volume; in addition, the processing and installation process of this plate-structured evaporator is simpler and more efficient, facilitating the improvement of equipment production efficiency and the reduction of manufacturing costs. Moreover, compared with the conventional electric compression refrigeration machine / heat pump using a shell-and-tube immersion evaporator, the refrigerant filling amount is less, saving the cost of refrigerant and being beneficial to environmental protection. Description of the drawings

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0022] Description of the reference numerals:

[0023] 1 - heat exchange plate pair, 2 - liquid retaining device, 3 - refrigerant vapor outlet, 4 - housing, 5 - heat source inlet, 6 - heat source outlet, 7 - liquid level gauge, 8 - valve, 9 - liquid refrigerant inlet, 10 - electric heat pump evaporator, 11 - absorption heat pump evaporator, 12 - solution pump, A - absorption heat pump absorber, C - absorption heat pump condenser, G - absorption heat pump generator, EX - solution heat exchanger, COM - compressor. Detailed implementation manners

[0024] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention.

[0026] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined. In addition, the terms "mounted", "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0027] Embodiment 1

[0028] As Figure 1As shown in the figure, an electric compression-absorption heat pump unit with a coupled plate evaporator includes an electric heat pump evaporator 10, a compressor COM, an absorption heat pump absorber A, an absorption heat pump evaporator 11, an absorption heat pump generator G, an absorption heat pump condenser C, and a solution heat exchanger EX; the electric heat pump evaporator 10 and the absorption heat pump evaporator 11 have the same structure, both being plate type rising film evaporators;

[0029] The evaporator includes a housing 4, which is made of a metal material. A plurality of groups of heat exchange plate pairs 1 are arranged in parallel inside the housing 4. Each group of heat exchange plate pairs 1 consists of two plate pieces, with a medium channel provided inside. The four sides of the two plate pieces are connected by laser, resistance sealing welding or brazing. The plate type of the plate pieces adopts a herringbone pattern, dimpled or corrugated plate structure to enhance the heat exchange effect and mechanical strength of the plate pieces. The plate pieces are made of metal materials such as stainless steel or titanium. Two interfaces that are vertically opposite to each other are provided on the upper side of each group of heat exchange plate pairs 1, and the interfaces are respectively connected to a heat source inlet 5 and a heat source outlet 6. A refrigerant is provided between the housing 4 and the heat exchange plate pairs 1. The liquid level height of the refrigerant in the evaporator is lower than the height of the heat exchange plate pairs 1. Preferably, the refrigerant submerges half of the height of the heat exchange plate pairs 1 to facilitate the evaporation and rising film of the refrigerant in the later stage. The specific liquid level height of the refrigerant can be further determined through experiments according to external conditions such as its physical properties, evaporation temperature, and pressure to determine the optimal immersion height. A liquid level gauge 7 is provided inside the housing 4 to detect the liquid level height of the refrigerant inside the housing 4. The liquid level gauge 7 adopts one of a differential pressure liquid level gauge, a float type liquid level gauge, a magnetic flap liquid level gauge, a tuning fork liquid level gauge, and a guided wave radar liquid level gauge.

[0030] A refrigerant vapor outlet 3 is provided at the top of the housing 4, a liquid refrigerant inlet 9 is provided at the bottom of the housing 4, and a liquid blocking device 2 is provided inside the housing 4. The liquid blocking device 2 is located at the top of the housing 4 and consists of a number of vertically arranged baffles. The baffles adopt structures such as a herringbone shape and a Z shape to increase the contact area with the refrigerant vapor. The refrigerant vapor outlet 3 is located above the liquid blocking device 2.

[0031] The heat source enters the heat exchange plate pairs 1 through the heat source inlet 5. The refrigerant and the heat source exchange heat through the heat exchange plate pairs 1. After the refrigerant absorbs heat, the splashing refrigerant droplets in the boiling and evaporating state rise to the position of the plate pieces not submerged by the refrigerant, forming a rising film wetting state. The liquid film continues to exchange heat with the heat source inside the heat exchange plate pairs 1 and is then heated and evaporated into a vapor state. The refrigerant vapor rises to the top of the evaporator, and the droplets carried therein will adhere to the baffles, preventing the droplets from entering the subsequent equipment. The refrigerant vapor from which the droplets have been removed is discharged through the refrigerant vapor outlet 3 at the top of the liquid blocking device 2 and enters the next process.

[0032] A valve 8 is provided on the liquid refrigerant inlet 9 connecting pipe. The valve 8 is one of an electric valve, a solenoid valve, a float valve, and a thermostatic expansion valve. By means of the valve 8, the liquid refrigerant inlet flow rate in the evaporator can be regulated, and further the liquid level of the refrigerant in the evaporator can be regulated. The valve 8 and the liquid level gauge 7 cooperate to accurately control the liquid level in the evaporator, ensuring that the refrigerant liquid level is always at the target height.

[0033] The heat source inlet 5 of the electric heat pump evaporator 10 is connected to a low-temperature heat source. The refrigerant in the shell 4 of the electric heat pump evaporator 10 is Freon, which can effectively absorb the heat of the low-temperature heat source. The refrigerant vapor outlet 3 of the electric heat pump evaporator 10 is sequentially connected to the compressor COM, the heat source inlet 5 of the absorption heat pump evaporator 11, the heat source outlet 6 of the absorption heat pump evaporator 11, and the liquid refrigerant inlet 9 of the electric heat pump evaporator 10 through pipelines. The refrigerant in the shell 4 of the absorption heat pump evaporator 11 is water. The refrigerant vapor outlet 3 of the absorption heat pump evaporator 11 is sequentially connected to the absorption heat pump absorber A, the solution pump 12, the solution heat exchanger EX, the absorption heat pump generator G, the absorption heat pump condenser C, and the liquid refrigerant inlet 9 of the absorption heat pump evaporator 11 through pipelines. The absorption heat pump generator G is sequentially connected to the solution heat exchanger EX and the absorption heat pump absorber A through pipelines. The medium to be heated is discharged after being heated through the absorption heat pump absorber A and the absorption heat pump condenser C through pipelines. The inlet of the absorption heat pump generator G is connected to a driving heat source.

[0034] With the above connection method and refrigerant type, the intermediate circulating water in the conventional scheme is omitted, reducing heat loss, and it can effectively extract the heat of a low-temperature heat source at a relatively low temperature (such as lower than 0 °C) for heating or other process heat uses.

[0035] Working process:

[0036] A method for recovering a low-temperature heat source by an electric compression-absorption heat pump unit coupled with a plate evaporator includes the following steps:

[0037] The low-temperature heat source is input into the heat exchange plate pair 1 through the heat source inlet 5 of the electric heat pump evaporator 10, and is discharged from the heat source outlet 6 of the electric heat pump evaporator 10 after releasing heat. The refrigerant Freon outside the heat exchange plate pair 1 synchronously absorbs heat. The refrigerant droplets splashing in the boiling evaporation state rise to the position of the plate that is not submerged by the refrigerant, and film boiling heat transfer occurs in the upper half of the plate. After the evaporated refrigerant vapor adsorbs the droplets through the liquid retaining device 2, it is discharged through the refrigerant vapor outlet 3 of the electric heat pump evaporator 10 and enters the compressor COM to be compressed into refrigerant vapor with increased temperature and pressure;

[0038] After the refrigerant vapor is heated and pressurized, it enters the heat exchange plate pair 1 through the heat source inlet 5 of the absorption heat pump evaporator 11, releases heat therein and is cooled into a liquid refrigerant, and then enters the liquid refrigerant inlet 9 of the electric heat pump evaporator 10 via the heat source outlet 6 of the absorption heat pump evaporator 11 and the valve 8, repeating the above process again;

[0039] The coolant water in the absorption heat pump evaporator 11 absorbs the heat released during the condensation process of the medium in the heat exchange plate pair 1. The coolant water boils and evaporates and undergoes falling film heat transfer in the upper half of the plate. The evaporated refrigerant vapor is discharged through the liquid baffle device 2 and the refrigerant vapor outlet 3 of the absorption heat pump evaporator 11 and enters the absorption heat pump absorber A; the lithium bromide solution in the absorption heat pump absorber A absorbs the above-mentioned coolant water and releases heat during the dilution process. After dilution, the lithium bromide solution is pumped by the solution pump 12 and enters the absorption heat pump generator G through the solution heat exchanger pump for concentration. The concentrated lithium bromide solution returns to the absorption heat pump absorber A through the solution heat exchanger pump; the inlet of the absorption heat pump generator G is connected to a driving heat source to achieve the concentration of the lithium bromide solution. Water vapor is generated during the concentration process of the lithium bromide solution in the absorption heat pump generator G. The water vapor enters the absorption heat pump condenser C, releases heat and is cooled therein, and then enters the interior of the absorption heat pump evaporator 11 via the valve 8 and the liquid refrigerant inlet 9 of the absorption heat pump evaporator 11.

[0040] The medium to be heated is heated and its temperature is raised by sequentially passing through the absorption heat pump absorber A and the absorption heat pump condenser C through a pipeline. The medium to be heated can be hot water in the heating process.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electric compression-absorption heat pump unit coupled with a plate evaporator, characterized in that: It includes an electric heat pump evaporator, a compressor, an absorption heat pump absorber, an absorption heat pump evaporator, an absorption heat pump generator, an absorption heat pump condenser and a solution heat exchanger; the electric heat pump evaporator has the same structure as the absorption heat pump evaporator, both of which are plate-type rising film evaporators, the evaporator includes a shell, a heat exchange plate pair is arranged in the shell, a heat source inlet and a heat source outlet are arranged on the heat exchange plate pair, a refrigerant is arranged between the shell and the heat exchange plate pair, a refrigerant vapor outlet is arranged at the top of the shell, and a liquid refrigerant inlet is arranged at the bottom of the shell; The heat source inlet of the electric heat pump evaporator is connected to a low-temperature heat source, the refrigerant vapor outlet of the electric heat pump evaporator is sequentially connected to the compressor, the heat source inlet of the absorption heat pump evaporator, the heat source outlet of the absorption heat pump evaporator and the liquid refrigerant inlet of the electric heat pump evaporator through a pipeline, the refrigerant vapor outlet of the absorption heat pump evaporator is sequentially connected to the absorption heat pump absorber, the solution heat exchanger, the absorption heat pump generator, the absorption heat pump condenser and the liquid refrigerant inlet of the absorption heat pump evaporator through a pipeline, the absorption heat pump generator is sequentially connected to the solution heat exchanger and the absorption heat pump absorber through a pipeline, the heating medium is discharged after being heated by the absorption heat pump absorber and the absorption heat pump condenser through the pipeline, and the inlet of the absorption heat pump generator is connected to a driving heat source.

2. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 1, characterized in that: A plurality of heat exchange plate pairs are arranged in parallel in the shell, and two upper and lower interfaces are arranged on the upper side of each heat exchange plate pair, and the interfaces are respectively connected to the heat source inlet and the heat source outlet.

3. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 2, characterized in that: Each group of the heat exchange plate pairs consists of two plates, with a medium channel arranged inside, and the two plates are connected around by laser, resistance sealing welding or brazing.

4. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 1, characterized in that: A liquid blocking device is arranged inside the shell, the liquid blocking device is located at the top of the shell, the liquid blocking device is composed of a plurality of vertically arranged baffles, and the refrigerant vapor outlet is located above the liquid blocking device.

5. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 1, characterized in that: A liquid level gauge is provided inside the shell, and the height of the refrigerant liquid level in the evaporator is lower than the height of the heat exchange plate pair.

6. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 5, characterized in that: The liquid level meter is one of a differential pressure liquid level meter, a float liquid level meter, a magnetic flap liquid level meter, a tuning fork liquid level meter, and a guided wave radar liquid level meter.

7. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 1, characterized in that: A valve is provided on the liquid refrigerant inlet connecting pipeline.

8. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 7, characterized in that: The valve is one of an electric valve, a solenoid valve, a float valve and a thermal expansion valve.

9. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 1, characterized in that: The refrigerant in the electric heat pump evaporator shell is Freon.

10. The electric compression-absorption heat pump unit coupled with a plate evaporator according to claim 1, characterized in that: The refrigerant in the absorption heat pump evaporator shell is water.

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