CN101093116A - Multistage-cascaded compression type heat pump set under large temperature difference - Google Patents

Abstract

The invention discloses a multi-stage series series large temperature difference compression heat pump unit, which belongs to a kind of high-efficiency heat pump equipment that can realize large temperature difference and small flow operation on both the cold source side and the heat source side. The present invention is composed of multi-stage condensers, evaporators, compressors and corresponding throttling devices and connecting pipelines, and the water systems of the condensers and evaporators at each level are connected in series to each other to form a connected inlet and outlet water system; adjacent condensers are refrigerated The refrigerant pipelines are connected in series through a throttling device, the last stage condenser is connected with the first stage evaporator through a throttling device, and the refrigerant pipelines of adjacent evaporators are also connected in series through a throttling device, and the corresponding evaporation The compressor and the condenser are connected through a compressor to form a refrigerant passage. The invention can effectively increase the temperature difference between hot water and cold water at the inlet and outlet of the heat pump, and can operate with a large temperature difference and a small flow rate, while the performance coefficient of the heat pump unit is still maintained at a relatively high level, and the comprehensive energy utilization efficiency of the system is higher than ordinary The heat pump unit is greatly improved.

Description

A multi-stage series series large temperature difference compression heat pump unit

technical field

The invention belongs to a heat pump unit used for heating, cooling and hot water supply, in particular to a high-efficiency compression heat pump unit capable of obtaining a large temperature difference between inlet and outlet at both the cold and heat source sides.

Background technique

At present, various heat pump devices have been widely used in various heating, cooling and hot water supply systems. Among them, in medium and large heating and air conditioning systems, water-water compression heat pumps have been widely used, such as using groundwater , Surface water or industrial waste hot water are heat pump cold and hot water units with low-temperature heat sources. In order to reduce transmission energy consumption, save water, and reduce the initial investment of the transmission and distribution system, the general water side is easy to operate with a large temperature difference and a small flow. When the inlet water temperature is constant, a large temperature difference and a small flow rate mean that the temperature of the hot water supply increases and the temperature of the cold water outlet decreases. For common heat pump devices, it will cause an increase in the condensation pressure and a decrease in the evaporation pressure, resulting in system failure. The coefficient of performance (COP) is reduced, and the energy utilization efficiency is reduced.

Contents of the invention

In view of the above problems, the present invention provides a multi-stage series-connected large temperature difference compression heat pump unit that operates at both the cold and heat source sides with a large temperature difference and small flow rate, so that its energy utilization efficiency is significantly improved compared with conventional heat pump devices.

Technical scheme of the present invention is as follows:

A multi-stage series series large temperature difference compression heat pump unit is characterized in that the unit is composed of two or more stages of condensers, evaporators, compressors and corresponding throttling devices and connecting pipelines; The hot water pipelines are connected in series, that is, the inlet and outlet pipes used for heat exchange in the condensers at all levels are connected in series to form a connected inlet and outlet circuit, sharing a water system; the cold water pipelines of the evaporators at all levels are connected in series, that is, The inlet and outlet pipes used for heat exchange in the evaporators of each stage are connected in series to form a connected inlet and outlet circuit, sharing a water system; the refrigerant pipes of adjacent condensers are connected in series through throttling devices, and finally The first-stage condenser and the first-stage evaporator are connected through a throttling device; the refrigerant pipelines of adjacent evaporators are also connected in series through a throttling device; the same-stage evaporator and condenser are connected through a compressor to form a refrigerant path.

The technical feature of the present invention is also that: an economizer is set between the final stage condenser and the first stage evaporator, and the flash gas passage pipeline is connected with the intermediate stage of the last stage compressor, and the described economizer adopts an open type Economizer or closed economizer.

Compared with the prior art, the present invention has the following advantages and prominent effects: the present invention can increase the temperature difference between hot water and cold water at the inlet and outlet of the heat pump, so that it can operate with a large temperature difference and a small flow rate, while the performance coefficient of the heat pump unit It is still maintained at a relatively high level, so the comprehensive energy utilization efficiency and economy of the system are greatly improved compared with ordinary heat pump units. The improvement of the performance of the multi-stage series heat pump unit is mainly reflected in: first, the temperature of the cold water is lowered in steps, and the temperature of the hot water is increased in steps, which reduces the heat transfer temperature difference between the evaporation end and the condensation end, and reduces the irreversible heat transfer loss; second, The refrigerant in the condenser is connected in series, the temperature of the condensate decreases successively, and the heat of the refrigerant is fully recovered; third, the refrigerant liquid is flash-cooled step by step in the evaporators at all levels, and the pressure is reduced step by step, which increases the cooling capacity and system energy efficiency; fourth , using a multi-stage series connection method, different heat pump units can be selected according to the working conditions of different temperature rise sections to ensure that each compressor operates under its high-efficiency working condition, and the cold and hot water can be adjusted by controlling the number of compressors running temperature to meet user requirements.

Description of drawings

Fig. 1 is a schematic flow diagram of an embodiment of a two-stage series-connected large temperature difference compression heat pump unit of the present invention.

Fig. 2 is a schematic flowchart of an embodiment of a three-stage series-connected large temperature difference compression heat pump unit of the present invention.

Fig. 3 is a schematic flowchart of an embodiment of a multi-stage (more than three-stage) large temperature difference compression heat pump unit of the present invention.

Fig. 4 is a schematic flowchart of an embodiment of a large temperature difference compression heat pump unit with an open economizer at the final stage of the present invention.

Fig. 5 is a schematic flowchart of an embodiment of a large temperature difference compression heat pump unit with a closed economizer at the final stage of the present invention.

Labels in the figure: 1a—first stage condenser; 1b—second stage condenser; 1c—third stage condenser; 1m—mth stage condenser; 1n—nth stage condenser; 2a—first stage evaporation 2b—second stage evaporator; 2c—third stage evaporator; 2m—mth stage evaporator; 2n—nth stage evaporator; 3a—first stage compressor; 3b—second stage compressor; 3c—the third-stage compressor; 3m—the m-th stage compressor; 3n—the final stage compressor; 4a—the first-stage condenser outlet refrigerant throttling device; 4b—the second-stage condenser outlet refrigerant throttling device ;4c—refrigerant throttling device at the outlet of the third-stage condenser; 4m—refrigerant throttling device at the outlet of the m-th condenser; 4n—refrigerant throttling device at the outlet of the final condenser; 5a—exit of the first-stage evaporator Refrigerant throttling device; 5b—refrigerant throttling device at the outlet of the second-stage evaporator; 5c—refrigerant throttling device at the outlet of the third-stage evaporator; 5m—refrigerant throttling device at the outlet of the m-th evaporator; 5n— Refrigerant throttling device at the outlet of the final evaporator; 6—the economizer; 7—the economizer throttling device.

Detailed ways

The technical solution of the present invention is to adopt multi-stage series combination to form a heat pump unit, that is, the unit is composed of two or more stages of compressors, condensers, evaporators, throttling devices and the like. The hot water pipes of the condensers at all levels are connected in series, that is, the inlet and outlet pipes used for heat exchange in the condensers at all levels are connected in series to form a connected inlet and outlet circuit, sharing a water system, and the hot water is condensed through n stages in turn. The cold water pipes of the evaporators at all levels are connected in series, that is, the inlet and outlet pipes used for heat exchange in the evaporators of each level are connected in series to form a connected inlet and outlet circuit, sharing a water system. The cold water is sent out after being cooled step by step through n-stage evaporators. The refrigerant pipes of adjacent condensers are connected in series through a throttling device, the last stage condenser is connected with the first stage evaporator through a throttling device, and the refrigerant pipes of adjacent evaporators are also connected in series through a throttling device. The evaporator and the condenser are connected through a compressor to form a refrigerant passage. The refrigerant is cooled and condensed step by step through the condensers of each stage in turn, and finally enters the first stage evaporator through the throttling device, and then evaporates through the evaporators of each stage step by step; the refrigeration evaporated in the evaporators of each stage The agent gas is compressed by the corresponding compressor and enters the corresponding condenser for condensation. Specifically: the saturated or superheated refrigerant vapor from the first-stage evaporator is compressed by the first-stage compressor into the first-stage condenser, and the saturated or superheated refrigerant vapor from the second-stage evaporator is compressed by the second-stage The compressor compresses and enters the second-stage condenser,..., the saturated or superheated refrigerant vapor from the last-stage evaporator is compressed by the last-stage compressor and enters the last-stage condenser; the first-stage condenser The refrigerant condensate that comes out first enters the second-stage condenser through the throttling device, and then enters the third-stage condenser through the throttling device together with the condensate in the second-stage condenser...until the last stage The first-stage condenser, and finally enter the first-stage evaporator through the throttling device, and part of the evaporated liquid is compressed by the first-stage compressor and enters the first-stage condenser, and the unevaporated liquid enters the second-stage evaporator through the throttling device to evaporate , the gas is compressed by the second-stage compressor and enters the second-stage condenser, and the unevaporated liquid enters the third-stage evaporator... until the last-stage evaporator, the refrigerant is completely evaporated and compressed by the last stage compressed into the final condenser.

The specific implementation manner of the present invention will be described below in combination with specific examples.

Example 1: Two-stage series-connected large temperature difference compression heat pump unit

As shown in Figure 1, the heat pump unit has a first-stage evaporator 2a, a first-stage compressor 3a, a first-stage condenser 1a, a refrigerant throttling device 4a at the outlet of the first-stage condenser, and an outlet of the first-stage evaporator. The refrigerant throttling device 5a is composed of the second-stage evaporator 2b, the second-stage compressor 3b, the second-stage condenser 1b, and the outlet refrigerant throttling device 4b of the second-stage condenser. Wherein, the pressure of the first-stage condenser 1a is greater than the pressure of the second-stage condenser 1b, the pressure of the second-stage condenser 1b is greater than the pressure of the first-stage evaporator 2a, and the pressure of the first-stage evaporator 2a is greater than the pressure of the second-stage evaporator 2b. The superheated or saturated refrigerant vapor from the first-stage evaporator 2a is compressed by the first-stage compressor 3a and then enters the first-stage condenser 1a to condense into refrigerant liquid, and the released latent heat of condensation heats the hot water high-temperature section; The superheated or saturated refrigerant vapor in the first-stage evaporator 2b is compressed by the second-stage compressor 3b and then enters the second-stage condenser 1b to condense into a refrigerant liquid, and the released latent heat of condensation heats the low-temperature section of hot water; the first-stage condenser 1a The outflowing refrigerant liquid enters the second-stage condenser 1b after being throttled and depressurized by the refrigerant throttling device 4a at the outlet of the first-stage condenser, and the released heat is also used to heat the low-temperature section of hot water and condense with the second-stage The refrigerant liquid condensed in the condenser flows out after converging, and then enters the first-stage evaporator 2a after throttling and reducing pressure through the outlet refrigerant throttling device 4b of the second-stage condenser. Part of the refrigerant liquid absorbs heat and evaporates from the high-temperature section of the cold water to become It is superheated gas or saturated gas, which is then compressed by the first-stage compressor 3a and enters the first-stage condenser 1a, and another part of the refrigerant liquid flows out of the first-stage evaporator, and further passes through the outlet refrigerant throttling device 5a of the first-stage evaporator. After throttling and depressurization, it enters the second-stage evaporator 2b, absorbs heat and evaporates from the cold water high-temperature section to become superheated gas or saturated gas, and then is compressed by the second-stage compressor 3b and enters the second-stage condenser; this cycle is repeated to complete the process from Cold water absorbs heat and heats hot water. It can be seen that this unit divides the hot water and cold water into two sections respectively. The hot water heats up in steps in the two-stage condensers, and the cold water cools down in steps in the two-stage evaporators. The temperature is adapted, thereby reducing the irreversible heat transfer loss in the evaporator and condenser, so that the system efficiency can be improved.

Example 2: Three-stage series-connected large temperature difference compression heat pump unit

As shown in Figure 2, the heat pump unit has a first-stage evaporator 2a, a first-stage compressor 3a, a first-stage condenser 1a, a refrigerant throttling device 4a at the outlet of the first-stage condenser, and an outlet of the first-stage evaporator. Refrigerant throttling device 5a, second-stage evaporator 2b, second-stage compressor 3b, second-stage condenser 1b, second-stage condenser outlet refrigerant throttling device 4b, second-stage evaporator outlet refrigerant section Flow device 5b, third-stage evaporator 2c, third-stage compressor 3c, third-stage condenser 1c, third-stage condenser outlet refrigerant throttling device 4c. Wherein, the pressure of the first-stage condenser 1a is greater than the pressure of the second-stage condenser 1b, the pressure of the second-stage condenser 1b is greater than the pressure of the third-stage evaporator 1c, and the pressure of the third-stage condenser 1c is greater than the pressure of the first-stage evaporator 2a, The pressure of the first-stage evaporator 2a is greater than the pressure of the second-stage evaporator 2b, and the pressure of the second-stage evaporator 2b is greater than the pressure of the third-stage evaporator 2c. The superheated or saturated refrigerant vapor from the first-stage evaporator 2a is compressed by the first-stage compressor 3a and then enters the first-stage condenser 1a to condense into refrigerant liquid, and the released latent heat of condensation heats the hot water high-temperature section; The superheated or saturated refrigerant vapor in the first-stage evaporator 2b is compressed by the second-stage compressor 3b and then enters the second-stage condenser 1b to condense into a refrigerant liquid, and the released latent heat of condensation heats the middle temperature section of hot water; from the third-stage evaporator The superheated or saturated refrigerant vapor in 2c is compressed by the third-stage compressor 3c and then enters the third-stage condenser 1c to condense into refrigerant liquid, and the released latent heat of condensation heats the low-temperature section of hot water; the refrigeration flow out of the first-stage condenser 1a The refrigerant liquid enters the second-stage condenser 1b after being throttled and depressurized by the refrigerant throttling device 4a at the outlet of the first-stage condenser. The refrigerant liquids flow out after converging, and pass through the outlet refrigerant throttling device 4b of the second-stage condenser to reduce the pressure and then enter the third-stage condenser 1c. The refrigerant liquid condensed in the third-stage condenser 1c joins and flows out, and then enters the first-stage evaporator 2a after throttling and reducing pressure through the refrigerant throttling device 4c at the outlet of the third-stage condenser. The stage absorbs heat and evaporates into superheated gas or saturated gas, which is then compressed by the first-stage compressor 3a and enters the first-stage condenser 1a, and another part of the refrigerant liquid flows out of the first-stage evaporator, and the refrigerant is exported through the first-stage evaporator The throttling device 5a further throttles and lowers the pressure and then enters the second-stage evaporator 2b. Part of the refrigerant liquid absorbs heat and evaporates from the cold water temperature section to become superheated gas or saturated gas, and is then compressed by the second-stage compressor 3b to enter the second stage. Condenser; the remaining refrigerant liquid flows out of the second-stage evaporator, and then enters the third-stage evaporator 2c through the second-stage evaporator outlet refrigerant throttling device 5b for further throttling and pressure reduction, and absorbs heat and evaporates from the cold water low-temperature section It becomes superheated gas or saturated gas, and then compressed by the third-stage compressor 3c to enter the third-stage condenser; this cycle repeats to complete the purpose of absorbing heat from cold water and heating hot water. It can be seen that this unit divides the hot water and cold water into three sections respectively. The hot water heats up step by step in the three-stage condenser, and the cold water cools down in steps in the three-stage evaporator. The temperature is adapted, thereby reducing the irreversible heat transfer loss in the evaporator and condenser, so that the system efficiency can be improved.

In addition, if the temperature difference between cold water and hot water is large, or the capacity of the unit is large, in order to further improve the performance coefficient of the unit, it can be considered to use a unit with more stages. As shown in Figure 3, there are n groups of condensers and evaporators in total. , compressor and corresponding throttling device and connecting pipeline. The hot water pipes of the condensers at all levels are connected in series, that is, the inlet and outlet pipes used for heat exchange in the condensers at all levels are connected in series to form a connected inlet and outlet circuit, sharing a water system, and the hot water is condensed through n stages in turn. The cold water pipes of the evaporators at all levels are connected in series, that is, the inlet and outlet pipes used for heat exchange in the evaporators of each level are connected in series to form a connected inlet and outlet circuit, sharing a water system. The cold water is sent out after being cooled step by step through n-stage evaporators. The refrigerant sides of the condensers are connected in series through a throttling device, the last stage condenser is connected with the first stage evaporator through a throttling device; the refrigerant sides of the evaporators are also connected in series through a throttling device; the evaporator and the condenser The compressors are connected to each other to form a refrigerant passage. The refrigerant passes through the condensers of each stage step by step to cool down and condense step by step, and finally enters the first stage evaporator through the throttling device, and then passes through the evaporators of each stage step by step to evaporate. , the pressure of the previous stage condenser is greater than the pressure of the next stage condenser, among the evaporators of each stage, the pressure of the previous stage evaporator is greater than the pressure of the next stage evaporator, and the pressure of the last stage condenser is greater than the pressure of the first stage evaporator; The refrigerant gas evaporated in the stage evaporator is compressed by the corresponding compressor and enters the corresponding condenser for condensation. Specifically: the saturated or superheated refrigerant vapor from the first-stage evaporator is compressed by the first-stage compressor into the first-stage condenser, and the saturated or superheated refrigerant vapor from the second-stage evaporator is compressed by the second-stage The compressor compresses and enters the second-stage condenser,..., the saturated or superheated refrigerant vapor from the n-stage evaporator is compressed by the n-stage compressor and enters the n-stage condenser; the first-stage condenser The refrigerant condensate that comes out first enters the second-stage condenser through the throttling device, and then enters the third-stage condenser through the throttling device together with the condensate in the second-stage condenser...until the last stage The first-stage condenser, and finally enter the first-stage evaporator through the throttling device, and part of the evaporated liquid is compressed by the first-stage compressor and enters the first-stage condenser, and the unevaporated liquid enters the second-stage evaporator through the throttling device to evaporate , the gas is compressed by the second-stage compressor and enters the second-stage condenser, and the unevaporated liquid enters the third-stage evaporator... until the last-stage evaporator, the refrigerant is completely evaporated and compressed by the last stage compressed into the final condenser.

In order to further improve the energy utilization efficiency of the heat pump unit, an economizer 6 can be provided at the final stage, and the economizer can be an open economizer or a closed economizer. Figure 4 shows a multi-stage series series large temperature difference compression heat pump unit with an open economizer at the final stage, connecting the flash gas passage pipeline with the intermediate stage of the final compressor. The liquid refrigerant flowing out from the final stage condenser flows into the economizer cavity through the economizer flow device 7, and the gas flashed during the throttling process enters the intermediate stage of the final stage compressor 3n through the pipeline, as an intermediate gas addition and For cooling, the remaining liquid refrigerant is cooled to the saturation temperature under the intermediate pressure, and then enters the first-stage evaporator 2a after throttling through the last throttling device 4n for the second time. Other circulation processes are the same as above. Figure 5 shows a multi-stage series series large temperature difference compression heat pump unit with a closed economizer at the final stage, connecting the flash gas passage pipeline with the intermediate stage of the final compressor. Part of the liquid refrigerant flowing out of the final stage condenser passes through the economizer throttling device 7 to flash evaporate the rest of the refrigerant, and the evaporated refrigerant gas enters the intermediate stage of the final stage compressor 3n for recompression, and the supercooled Refrigerant liquid enters the first-stage evaporator 2a through the last throttling device 4n. Other circulation processes are the same as above.

Claims (2)

1. A multi-stage series series large temperature difference compression heat pump unit, characterized in that: the unit is composed of two or more stages of condensers, evaporators, compressors and corresponding throttling devices and connecting pipelines; The hot water pipes of the condensers are connected in series, that is, the inlet and outlet pipes used for heat exchange in the condensers at all levels are connected in series to form a connected inlet and outlet circuit, sharing a water system; the cold water pipes of the evaporators at all levels are connected in series , that is, the inlet and outlet pipes used for heat exchange in the evaporators at all levels are connected in series to form a connected inlet and outlet circuit, sharing a water system; the refrigerant pipes of adjacent condensers are connected in series through throttling devices, The last-stage condenser is connected to the first-stage evaporator through a throttling device; the refrigerant pipelines of adjacent evaporators are also connected in series through a throttling device; the same-stage evaporator and condenser are connected through a compressor to form a Refrigerant passage. 2. A multi-stage series series large temperature difference compression heat pump unit according to claim 1, characterized in that: an economizer is installed between the final condenser and the first evaporator, and the flash gas passage pipe is connected to the final evaporator. The intermediate stages of the stage compressor are connected, and the economizer adopts an open economizer or a closed economizer.

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