A gas heat pump unit with direct utilization of engine waste heat and adjustable air supply

Abstract

A gas-fired heat pump unit that directly utilizes engine waste heat and features adjustable air supply is disclosed. The condenser and water supply and return lines are combined with refrigerant and coolant heat exchange lines. Refrigerant flows from the quasi-two-stage compressor outlet through the refrigerant heat exchange line, dividing it into a main path and an auxiliary path. The auxiliary path connects to the quasi-two-stage compressor air supply port after passing through a first electronic expansion valve and a flue gas heat exchanger. The main path, switched by a four-way reversing valve, can control forward and reverse circulation between the second electronic expansion valve and the outdoor evaporator. The outlet is connected to the quasi-two-stage compressor inlet. Coolant flows from the gas engine outlet through a coolant circulation pump and the coolant heat exchange line back to the inlet. The gas engine exhaust port is connected to the flue gas heat exchanger. Compressor air supply is simple and highly adjustable. The condenser utilizes stepped heating to decouple engine waste heat from compressor power. Heating is continuous during reverse cycle defrosting, improving indoor thermal comfort.

Description

Technical Field

[0001] The present invention relates to a gas heat pump unit, in particular to a gas heat pump unit that directly utilizes engine waste heat and has adjustable air supply, belonging to the technical field of heat pump unit performance optimization. Background Art

[0002] Gas-fired heat pumps, which use a gas engine to drive a compressor, are highly energy-efficient devices that significantly improve primary energy utilization and save electricity. However, this also leads to a high degree of coupling between the compressor and the gas engine. Current heat pumps directly recover engine waste heat into the refrigerant pipeline, serving as the heat pump's low-level heat source. However, when outdoor temperatures are low (below -10°C), the heat pump's inherent thermal integrity is limited. With existing gas engines and compressors, the engine's waste heat is sufficient to serve as the heat pump's low-level heat source. At this time, the outdoor evaporator draws little heat from the outdoor air. Consequently, the refrigerant pressure in the outdoor evaporator is significantly lower than the refrigerant pressure used for waste heat recovery. This leads to uneven refrigerant flow distribution, insufficient refrigerant flow to the outdoor evaporator, insufficient heat absorption, and reduced unit efficiency. Increasing the compressor power to increase the refrigerant flow to the outdoor evaporator would increase the gas engine speed, increasing waste heat, and the problem of insufficient heat absorption by the outdoor evaporator persists. Summary of the Invention

[0003] In order to address the deficiencies in the background technology, the present invention provides a gas heat pump unit with direct utilization of engine waste heat and adjustable air supply. The air supply of its quasi-two-stage compressor comes from the flue gas heat exchanger, which is simple and highly adjustable. The condenser adopts a stepped heating method, which realizes the decoupling of engine waste heat and compressor power, compensates for the defect of insufficient heat exchange capacity of the outdoor evaporator at low temperature, and during the reverse cycle defrost, the low-temperature return water can still exchange heat with the engine coolant, providing uninterrupted heating and improving indoor thermal comfort.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a gas heat pump unit with direct utilization of engine waste heat and adjustable air supply, comprising a quasi-two-stage compressor, a condenser, a flue gas heat exchanger, a four-way reversing valve, an outdoor evaporator, a gas engine, and a coolant circulation pump, wherein:

[0005] The condenser is provided with a water supply and return pipeline and two heat exchange pipelines matched therewith, wherein the two heat exchange pipelines are divided into a refrigerant heat exchange pipeline and a coolant heat exchange pipeline;

[0006] The refrigerant is divided into a main path and an auxiliary path after passing through the refrigerant heat exchange pipeline of the condenser from the outlet of the quasi-two-stage compressor. The auxiliary path is connected to the refrigerant inlet of the flue gas heat exchanger after passing through the first electronic expansion valve. The refrigerant outlet of the flue gas heat exchanger is connected to the air supply port of the quasi-two-stage compressor for air supply. The main path is a circulation loop provided with a four-way reversing valve and includes a second electronic expansion valve and an outdoor evaporator. The forward and reverse circulation of the second electronic expansion valve and the outdoor evaporator can be controlled by switching the four-way reversing valve. The outlet of the four-way reversing valve is connected to the inlet of the quasi-two-stage compressor.

[0007] The coolant flows from the outlet of the gas engine through the coolant circulation pump and the coolant heat exchange pipeline of the condenser back to the inlet of the gas engine;

[0008] The exhaust port of the gas engine is connected to the air inlet end of the flue gas heat exchanger.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can reduce the exhaust temperature of the compressor through intermediate air supply, ensuring the safe and stable operation of the unit at low temperatures; the air supply heat of the quasi-two-stage compressor comes from the flue gas heat exchanger, and the independent adjustability of the air supply amount can realize a wide range of adjustment of the heating capacity of the heat pump unit; the condenser adopts a stepped heating method, and uses the waste heat of the engine to heat the low-temperature return water, thereby realizing the decoupling of the waste heat of the engine and the compressor power; on the one hand, it makes up for the defect of insufficient heat exchange of the outdoor evaporator at low temperatures, greatly improving the low-temperature performance and primary energy utilization rate of the unit; on the other hand, it reduces the engine coolant temperature, prevents the gas engine from overheating, and improves the safety and stability of the gas engine operation; and during the reverse cycle defrosting of the heat pump, the low-temperature return water in the condenser can still exchange heat with the engine coolant, ensuring uninterrupted heating of the unit during defrosting, thereby improving indoor thermal comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a system principle diagram of the gas heat pump unit of the present invention. DETAILED DESCRIPTION

[0011] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0012] Combine Figure 1 As shown, a gas heat pump unit with direct utilization of engine waste heat and adjustable air supply includes a quasi-two-stage compressor 1, a condenser 2, a flue gas heat exchanger 4, a four-way reversing valve 5, an outdoor evaporator 7, a gas engine 8 and a coolant circulation pump 9, wherein:

[0013] The condenser 2 is provided with a water supply and return pipeline and two heat exchange pipelines coordinated therewith. The two heat exchange pipelines are divided into a refrigerant heat exchange pipeline and a coolant heat exchange pipeline. This form helps to achieve step-by-step heating of the condenser 2. The low-temperature return water first exchanges heat with the engine coolant in the coolant heat exchange pipeline, absorbs heat and becomes medium-temperature water, and then exchanges heat with the high-temperature and high-pressure refrigerant in the refrigerant heat exchange pipeline, absorbs heat and becomes high-temperature supply water.

[0014] The refrigerant is divided into a main path and an auxiliary path after passing through the refrigerant heat exchange pipeline of the condenser 2 from the outlet end of the quasi-two-stage compressor 1. The auxiliary path is connected to the refrigerant inlet of the flue gas heat exchanger 4 after passing through the first electronic expansion valve 3. The refrigerant outlet of the flue gas heat exchanger 4 is connected to the air supply port of the quasi-two-stage compressor 1 for air supply. The quasi-two-stage compressor 1 preferably adopts a scroll compressor with an intermediate air supply port and is driven by a gas engine 8. The main path is a circulation loop provided with a four-way reversing valve 5 and including a second electronic expansion valve 6 and an outdoor evaporator 7. The forward and reverse circulation of the second electronic expansion valve 6 and the outdoor evaporator 7 can be controlled by switching the four-way reversing valve 5. The outlet end of the four-way reversing valve 5 is connected to the inlet end of the quasi-two-stage compressor 1 to realize the circulation of the refrigerant.

[0015] The coolant flows from the outlet of the gas engine 8 through the coolant circulation pump 9 and the coolant heat exchange pipeline of the condenser 2 back to the inlet of the gas engine 8, thus realizing the circulation of the coolant;

[0016] The exhaust port of the gas engine 8 is connected to the air inlet end of the flue gas heat exchanger 4, and is discharged into the atmosphere through the air outlet end of the flue gas heat exchanger 4 or further processed to achieve the smoke exhaust task.

[0017] The main circuit performs reverse circulation by switching the four-way reversing valve 5, changing the flow direction of the refrigerant in the outdoor evaporator 7, and realizing the heat pump reverse cycle defrosting task.

[0018] The core principle of the present invention is:

[0019] 1. The heat of gasification of the supplementary air refrigerant of the quasi-two-stage compressor 1 comes from the flue gas heat exchanger 4, which is independent of the main refrigerant. This reduces the exhaust temperature of the quasi-two-stage compressor 1 while achieving adjustable supplementary air volume.

[0020] 2. Condenser 2 adopts a stepped heating method, using the engine's waste heat to heat the low-temperature return water, using the waste heat as a high-level heat source, and absorbing the air heat through the outdoor evaporator 7, making up for the defect of insufficient heat exchange of the outdoor evaporator 7 at low temperatures, effectively improving the low-temperature performance and primary energy utilization rate of the unit;

[0021] 3. During the reverse cycle defrosting period of the unit, the four-way reversing valve 5 changes the flow direction of the refrigerant in the outdoor evaporator 7. The system cannot absorb heat from the outdoor evaporator 7, but the gas engine 8 operates normally. The low-temperature return water in the condenser 2 can still exchange heat with the engine coolant, ensuring uninterrupted heating during the defrosting period and improving indoor thermal comfort.

[0022] The operating conditions of the present invention are as follows:

[0023] Refrigerant cycle process

[0024] The high-temperature, high-pressure refrigerant gas discharged from the quasi-two-stage compressor 1 is condensed and released in the condenser 2 to become a low-temperature, high-pressure refrigerant liquid, which is then divided into a main path and an auxiliary path at the outlet of the condenser 2. The auxiliary path refrigerant liquid is throttled and depressurized by the first electronic expansion valve 3, becoming a medium-pressure two-phase refrigerant mixture. It enters the flue gas heat exchanger 4 to exchange heat with the high-temperature flue gas, absorbs heat, evaporates, and becomes a gas. It then enters the air supply port of the quasi-two-stage compressor 1 for air supply. The main path refrigerant liquid is throttled and depressurized by the four-way reversing valve 5 and the second electronic expansion valve 6 to become a low-temperature, low-pressure two-phase refrigerant mixture. It then enters the outdoor evaporator 7 to absorb heat and evaporate. Finally, the main path refrigerant gas enters the quasi-two-stage compressor 1, is compressed by the quasi-two-stage compressor 1, and is mixed with the auxiliary path refrigerant gas. It is then further compressed and discharged, forming a complete refrigerant cycle.

[0025] Waste heat recovery process

[0026] The engine coolant absorbs the waste heat of the engine in the gas engine 8 and becomes high-temperature coolant, which then enters the condenser 2 through the coolant circulation pump 9, exchanges heat with the low-temperature return water, and becomes low-temperature coolant before returning to the gas engine 8.

[0027] Reverse cycle defrost process

[0028] During the refrigerant circulation process, the four-way reversing valve 5 controls the main circuit reverse circulation, changes the refrigerant flow direction in the outdoor evaporator 7, and realizes the defrosting task.

[0029] Smoke exhaust process

[0030] The high-temperature flue gas discharged by the gas engine 8 enters the flue gas heat exchanger 4, exchanges heat with the auxiliary refrigerant and is discharged into the atmosphere. After heat exchange in the flue gas heat exchanger 4, the water vapor in the exhaust gas is liquefied into condensed water, reducing the exhaust gas temperature.

[0031] The quasi-two-stage compressor 1 adopts a scroll compressor with an intermediate air supply port. After throttling, a part of the refrigerant absorbs heat and evaporates into gas in the flue gas heat exchanger 4 and enters the intermediate air supply port of the compressor. The other part of the refrigerant enters the outdoor evaporator 7 to absorb heat and evaporate into gas refrigerant and enters the compressor intake port. The intermediate air supply reduces the compressor exhaust temperature, ensuring that the heat pump operates efficiently and stably at low temperatures (below -10°C), and the exhaust temperature does not exceed 120°C.

[0032] The heat of gasification of the supplementary air refrigerant comes from the flue gas heat exchanger 4, rather than the conventional quasi-two-stage compression gas heat pump that realizes supplementary air gasification through main line cooling. This not only realizes the adjustable supplementary air volume, but also recovers the waste heat of the flue gas, thereby improving the primary energy utilization rate of the unit.

[0033] Condenser 2 utilizes a stepped heating system. Low-temperature return water first exchanges heat with the engine coolant, absorbing heat to become medium-temperature water. It then exchanges heat with the high-temperature, high-pressure refrigerant, absorbing heat to become high-temperature supply water. This direct recovery of engine waste heat into the supply and return water loops decouples engine waste heat from compressor power, reducing high-quality energy waste and significantly improving the unit's low-temperature performance. At low temperatures (-20°C), the unit's primary energy utilization coefficient (PER) is increased from 0.75 to 1.05, and its COP is raised to 2.33.

[0034] During the reverse cycle defrosting period of the unit, although heat cannot be absorbed from the outdoor evaporator 7, heat can still be absorbed from the engine coolant, ensuring uninterrupted heating of the unit during the defrosting period and improving indoor thermal comfort.

[0035] Overall, the gas heat pump unit of the present invention undergoes step-by-step heating and heat recovery, which not only greatly improves the low-temperature performance of the unit and reduces the energy consumption of the unit, but also ensures uninterrupted heating of the unit during defrosting, thereby improving indoor thermal comfort.

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other configurations without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations coming within the meaning and range of equivalents of the claims are intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0037] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A gas heat pump unit that directly utilizes engine waste heat and has adjustable air supply, characterized by: It includes a quasi-two-stage compressor (1), a condenser (2), a flue gas heat exchanger (4), a four-way reversing valve (5), an outdoor evaporator (7), a gas engine (8) and a coolant circulation pump (9), wherein: The condenser (2) is provided with a water supply and return pipeline and two heat exchange pipelines coordinated therewith, wherein the two heat exchange pipelines are divided into a refrigerant heat exchange pipeline and a coolant heat exchange pipeline; The refrigerant is divided into a main path and an auxiliary path after passing through the refrigerant heat exchange pipeline of the condenser (2) from the outlet of the quasi-two-stage compressor (1). The auxiliary path is connected to the refrigerant inlet of the flue gas heat exchanger (4) after passing through the first electronic expansion valve (3). The refrigerant outlet of the flue gas heat exchanger (4) is connected to the air supply port of the quasi-two-stage compressor (1) for air supply. The air supply heat of the quasi-two-stage compressor (1) only comes from the flue gas heat exchanger (4). The air supply amount is independently adjusted by the first electronic expansion valve (3). The main path is a circulation loop provided with a four-way reversing valve (5) and including a second electronic expansion valve (6) and an outdoor evaporator (7). The forward and reverse circulation of the second electronic expansion valve (6) and the outdoor evaporator (7) can be controlled by switching the four-way reversing valve (5). The outlet of the four-way reversing valve (5) is connected to the inlet of the quasi-two-stage compressor (1); The coolant flows from the outlet of the gas engine (8) through the coolant circulation pump (9) and the coolant heat exchange pipeline of the condenser (2) back to the inlet of the gas engine (8); The condenser (2) performs step heating, and the return water first exchanges heat with the engine coolant in the coolant heat exchange pipeline, and then exchanges heat with the refrigerant in the refrigerant heat exchange pipeline; The four-way reversing valve (5) switches and controls the second electronic expansion valve (6) and the outdoor evaporator (7) to reversely circulate, thereby performing reverse cycle defrosting on the unit. During this period, the return water in the condenser (2) still exchanges heat with the engine coolant, thereby ensuring uninterrupted heating during the reverse cycle defrosting of the unit. The exhaust port of the gas engine (8) is connected to the air inlet end of the flue gas heat exchanger (4).

2. The gas heat pump unit with direct utilization of engine waste heat and adjustable air supply according to claim 1, characterized in that: The quasi-two-stage compressor (1) adopts a scroll compressor with an intermediate air supply port.

3. A gas heat pump unit with direct utilization of engine waste heat and adjustable air supply according to claim 1 or 2, characterized in that: The gas engine (8) drives the quasi-two-stage compressor (1).

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