CN112648733A - Graded partial pressure modular heat energy lifting system and control method thereof - Google Patents
Graded partial pressure modular heat energy lifting system and control method thereof Download PDFInfo
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- CN112648733A CN112648733A CN202011485879.5A CN202011485879A CN112648733A CN 112648733 A CN112648733 A CN 112648733A CN 202011485879 A CN202011485879 A CN 202011485879A CN 112648733 A CN112648733 A CN 112648733A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H4/00—Fluid heaters characterised by the use of heat pumps
- F24H4/02—Water heaters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H9/00—Details
- F24H9/20—Arrangement or mounting of control or safety devices
- F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B30/00—Heat pumps
- F25B30/02—Heat pumps of the compression type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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Abstract
The invention provides a graded compression modular heat energy lifting system and a control method thereof, and the system comprises a plurality of parallel multistage heat pump modules, wherein each heat pump module comprises an evaporator, a compressor, a condenser and a throttle valve; the evaporator comprises a waste hot water heat exchange pipe and a first refrigerant heat exchange channel; the condenser comprises a second refrigerant heat exchange channel and a hot water supply heat exchange tube; the first refrigerant heat exchange channel, the compressor, the second refrigerant heat exchange channel and the throttling valve are connected end to realize closed circulation; the waste hot water heat exchange pipes of the adjacent heat pump modules are communicated; the hot water supply heat exchange pipes of the adjacent heat pump modules are communicated. The invention realizes the grading and partial pressure operation of the heat pump modules by using the parallel connection of the multi-stage heat pump modules. Through carrying out modular processing to single-stage heat pump, can be according to actual conditions, like operating condition, cost etc. the heat pump module quantity of control operation, it is convenient to make up, and the suitability is wider.
Description
Technical Field
The invention relates to the field of heat pump control, in particular to a grading modular heat energy lifting system and a control method thereof.
Background
China is the first major manufacturing country around the world, and industries such as coke, ferrous metal smelting (steel), non-ferrous metal smelting, non-metal manufacturing, chemical industry and the like are in large quantity, and the product yield is high. The industrial energy consumption accounts for more than 70% of the total energy consumption in China, at least 50% of the industrial energy consumption is converted into industrial waste heat with different carriers and different temperatures, the recovery rate of the industrial waste heat in China is only about 30%, and the rest of the industrial waste heat is discharged into the atmosphere or water in the form of waste heat, so that the energy utilization efficiency is low. The heat pump is an effective technology for improving the grade of heat energy, is particularly suitable for absorbing heat from air or industrial waste heat, is widely applied to the fields of industrial drying, heating, regional centralized heat supply and the like, and is used for replacing the traditional coal-fired and gas-fired boilers to achieve the purposes of improving the utilization rate of energy and saving energy and reducing emission.
For example, patent document CN110645710A discloses a heat pump water heater capable of recovering waste heat, which is characterized in that: it includes the heat pump body, the inboard of heat pump body is provided with evaporation fin, one side of heat pump body is provided with cold water inlet, one side of cold water inlet is provided with the hot water export, the upside of hot water export is provided with the manometer, the upside of heat pump body is provided with air inlet department, its characterized in that: the downside of heat pump body is provided with removes the wheel, the inboard upper end that is close to the evaporation fin of heat pump body is provided with the shower, the upside of air inlet department is provided with protection machanism, one side of air inlet department is provided with the storage water tank, the one end of storage water tank is provided with the connecting pipe, the storage water tank carries out inside intercommunication through the connecting pipe with the shower, one side of storage water tank is provided with clean water inlet, the opposite side of heat pump body is provided with clean outlet, one side of heat pump body is close to the manometer and is provided with the installation piece, one side of installation piece is provided with.
Namely, the compression type heat pump system for recovering the low-grade waste heat and outputting the hot water is equipment with great significance in energy saving, and has good application market. At present, a plurality of mature small-sized medium-low temperature heat pump products with the heating temperature below 80 ℃ exist, but a large-capacity, large-temperature-rise and high-efficiency heat pump still has market blank, and the heat pump is beneficial to meeting the large-capacity regional or industrial heating demand by recovering industrial waste heat. Generally, a large-temperature-rise heat pump is difficult to maintain a high system coefficient of performance (COP), and is mainly limited by component efficiency and a system circulation form, so that a heat pump system needs to be reasonably designed and optimized to meet the requirements, and the capacity, the heating temperature and the system performance of an industrial heat pump are further improved.
Disclosure of Invention
In view of the defects in the prior art, the present invention provides a fractional modular thermal energy lifting system and a control method thereof.
The invention provides a fractional compression modular thermal energy lifting system, which comprises a plurality of parallel multistage heat pump modules 2, wherein each heat pump module 2 comprises an evaporator 9, a compressor 11, a condenser 13 and a throttle valve 15;
the evaporator 9 comprises a waste hot water heat exchange tube 8 and a first refrigerant heat exchange channel 10;
the condenser 13 comprises a second refrigerant heat exchange channel 12 and a hot water supply heat exchange tube 14;
the first refrigerant heat exchange channel 10, the compressor 11, the second refrigerant heat exchange channel 12 and the throttle valve 15 are connected end to realize closed circulation;
the waste hot water heat exchange pipes 8 of the adjacent heat pump modules 2 are communicated;
the hot water supply heat exchange pipes 14 of the adjacent heat pump modules 2 are communicated.
Preferably, the waste hot water heat exchange pipes 8 of the adjacent heat pump modules 2 are communicated through the waste hot water connection pipe 3.
Preferably, the hot water supply heat exchange pipes 14 of the adjacent heat pump modules 2 are communicated through the hot water supply connecting pipe 6.
Preferably, the waste hot water enters from the waste hot water heat exchange tube 8 of the last stage heat pump module and flows out from the waste hot water heat exchange tube 8 of the first stage heat pump module;
hot water enters from the hot water supply heat exchange tube 14 of the first-stage heat pump module and flows out from the last-stage hot water supply heat exchange tube 14.
Preferably, in the waste hot water circulation direction, the pressure of the evaporator 9 of the heat pump module decreases and the pressure of the condenser 13 of the hot die module decreases.
Preferably, the evaporator and condenser employ falling film or flooded heat exchangers.
Preferably, the heat pump module adopts an inverter compressor.
Preferably, the number of stages of the heat pump module is 4 to 9 stages.
The invention provides a control method based on the hierarchical partial pressure modular heat energy lifting system, which comprises the following steps:
a set temperature input step: inputting a desired output temperature T7;
a detection step: measuring the current heat source temperature Ts and the cooling water temperature Th;
a rotating speed determining step: detecting heat pump module evaporator inlet temperature Ti,NAnd condenser outlet temperature To,NAccording to Ti,NAnd To,NDetermining the rotating speed of the compressor corresponding to the saturation pressure;
a temperature judgment step: after the rotating speed of the compressor reaches the stability, whether the evaporation temperature of the heat pump module is the inlet temperature T or not is detectedi,N-x ℃, detecting whether the condensing temperature is the outlet temperature T of the condensero,NAt the temperature of-x ℃, if the judgment result is yes, entering a next-stage heat pump module, and entering a rotating speed determining step; if the judgment result is no, the inlet temperature T of the evaporator at the moment is detected againi,NTemperature T at the outlet of the condensero,NThe rotating speed of the compressor is regulated again until the minimum heat exchange temperature difference of the heat exchanger is maintained at x ℃;
an output step: outputting a final temperature T7, judging whether the required output temperature T7 is reached, and if so, maintaining the state operation; if the judgment result is negative, the last stage of heat pump module starts to adjust again until the required output temperature is reached, and each heat pump module is kept to operate stably to obtain stable output.
Preferably, x is the minimum heat exchange temperature difference.
Compared with the prior art, the invention has the following beneficial effects:
the large temperature rise is realized, the high efficiency is ensured, and the irreversible loss generated by heat transfer is reduced.
1. According to the invention, the multi-stage heat pump modules are connected in parallel, so that heat energy is absorbed from waste heat, the grade of the heat energy is improved through the compressor, and high-grade heat energy is output to hot water to heat the hot water. In the safe operation range of each heat pump, the multi-stage parallel connection can greatly improve the temperature of hot water which can be output, improve the utilization rate of energy, reduce the consumption of energy and achieve the effect of saving energy.
2. According to the invention, the multi-stage heat pump modules are connected in parallel, the corresponding evaporation and condensation temperatures are determined according to the minimum heat exchange temperature difference, the heat exchange temperature difference in each heat pump heat exchanger is reduced, the purpose of absorbing waste heat energy in a gradient manner and outputting heat energy in a gradient manner is effectively realized, the irreversible loss in the heat exchange process is reduced, and the system energy efficiency is further improved.
3. The invention realizes the grading and partial pressure operation of the heat pump modules by using the parallel connection of the multi-stage heat pump modules, and the operation pressure ratio of the compressor in each heat pump module is approximate, so that the compressors of the same type can be used, the unit cost is reduced, and the operation and the maintenance are convenient.
4. According to the invention, by performing modular processing on the single-stage heat pump, the number of the heat pump modules can be controlled according to actual conditions, such as operation conditions, cost and the like, the combination is convenient and fast, and the applicability is wider.
5. The invention adopts water as heat exchange medium, the evaporator and the condenser all adopt falling film or flooded heat exchangers, water flows in the tubes, and refrigerant is outside the tubes, the heat exchanger can reduce heat exchange temperature difference, the minimum heat exchange temperature difference is only 2 ℃, and irreversible loss of heat exchange can be further reduced. And water is used as a heat exchange medium, so that the heat exchange coefficient is high, the heat exchange efficiency can be obviously improved, the heat exchange area is reduced, and the occupied space of a unit is saved.
6. According to the invention, each heat pump unit adopts the variable frequency compressor, the evaporation pressure is gradually increased aiming at the dynamic change in the starting process, namely the suction pressure of the compressor is gradually increased, and the variable frequency compressor can automatically adjust the rotating speed to adapt to the change of the suction pressure, so that the energy-saving operation is realized. Furthermore, when the system load changes, the variable frequency compressor can adapt to the load change from the self-adjusting rotating speed, the compressor is not required to be controlled to start and stop, the heat pump unit is always operated in the optimal state, and more energy is saved.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic view of a staged partial pressure modular thermal energy lifting system.
Fig. 2(a) is a heat exchange curve diagram of the evaporation and condensation process of the parallel system of the first-stage heat pump modules.
Fig. 2(b) is a heat exchange curve diagram of the evaporation and condensation process of the parallel system of the two-stage heat pump modules.
Fig. 2(c) is a heat exchange curve diagram of the evaporation and condensation process of the parallel system of the three-stage heat pump modules.
Fig. 3 is a pressure-enthalpy diagram of a single-stage heat pump system.
FIG. 4 is a graph illustrating the change in system performance with increasing number of parallel stages.
Fig. 5 is a flow chart of a control method of the graded partial pressure modular thermal energy lifting system.
The figures show that:
waste heat inlet pipe 1
Waste hot water connecting pipe 3
Waste heat water outlet pipe 4
Heat supply water inlet pipe 5
Hot water supply connecting pipe 6
Hot water supply outlet pipe 7
Waste hot water heat exchange pipe 8
Evaporator 9
First refrigerant heat exchange channel 10
Second refrigerant heat exchange channel 12
Hot water supply heat exchange pipe 14
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1 to 5, the present invention provides a fractional pressure modularized heat energy lifting system and a control method thereof, the fractional pressure modularized heat energy lifting system comprises a plurality of single-stage heat pump units, each single-stage heat pump unit is a heat pump module, evaporators of the single-stage heat pump modules are communicated through a waste hot water side connecting pipe to realize step absorption of waste heat (cold water) heat, condensers of the single-stage heat pump units are communicated through a hot water supply side connecting pipe to realize step heating of hot water (hot water), and hot water supply sides and waste hot water sides of the evaporators of the plurality of single-stage heat pump units are respectively connected in series through communicating pipes to realize parallel operation of a plurality of single-stage heat; each single-stage heat pump module consists of an evaporator, a compressor, a condenser and a throttle valve, and is connected by a connecting pipe, so that heat absorption from cold water in the evaporator is realized, the heat energy grade is improved by the compressor, heat is released from the condenser to hot water, and the circulation is repeated after the temperature and the pressure of the hot water are reduced by the throttle valve.
The single-stage heat pump module is a heat pump module, the heat pump module 2 consists of an evaporator 9, a compressor 11, a condenser 13 and a throttle valve 15, an outlet of a first refrigerant heat exchange channel 10 is connected with an inlet of the compressor 11 through a refrigerant connecting pipe, an outlet of the compressor 11 is connected with a second refrigerant heat exchange channel 12, an outlet of the second refrigerant heat exchange channel 12 is connected with an inlet of the throttle valve 15, and an outlet of the throttle valve 15 is connected with an inlet of the first refrigerant heat exchange channel 10, so that closed circulation is realized. Waste hot water enters from the waste heat inlet pipe 1, and a waste hot water heat exchange pipe 8 in the evaporator of the heat pump module is communicated through a waste hot water connecting pipe 3. Hot water enters from a heat supply water inlet pipe 5, and a hot water heat exchange pipe 14 in a condenser of the heat pump module is communicated through a hot water supply connecting pipe 6. Refrigerant liquid absorbs heat from cold water in the evaporator, is evaporated into superheated gas, enters the compressor to be compressed into high-temperature and high-pressure superheated gas, enters the condenser, is cooled and condensed to release heat to hot water, is condensed into liquid refrigerant with a certain supercooling degree, enters the throttle valve to be cooled and decompressed to two-phase refrigerant, enters the evaporator again to continuously absorb the heat of the cold water, and the process is repeated, so that continuous waste heat absorption, heat energy grade improvement and high-grade heat energy release are realized.
The cascade absorbs heat of a heat source, waste hot water enters from an inlet of a waste heat inlet pipe at the side of the last-stage evaporator (nth stage), absorbs heat through n-stage, n-1-stage … 2-stage and 1-stage evaporators, and flows out from an outlet at the side of the waste hot water of the first-stage evaporator, so that the cascade can be used as cold water for supplying water. The n-th to 1-stage evaporators are connected in series by waste hot water connecting pipes to form a communicated water path, so that the heat pump system absorbs heat of a heat source in a cascade manner, the heat exchange temperature difference in each stage of evaporator is reduced, and the irreversible loss of heat exchange is reduced. The pressure of the nth stage evaporator is greater than the pressure of the (n-1) th stage evaporator, …, greater than the pressure of the 2 nd stage evaporator and greater than the pressure of the 1 st stage evaporator, so that classification and partial pressure are realized.
The invention is used for heating hot water in a cascade way, hot water enters from the inlet of a hot water supply pipe at the side of a first-stage condenser, sequentially enters into a 1-stage, a 2-stage … n-1-stage and an n-stage condenser, is heated, and flows out from the outlet of the hot water supply side of a last-stage condenser, so that the hot water can be used as hot water for heating. The 1 st to n-th grade condensers are connected in series by a heat supply hot water connecting pipe to form a communicated water path, so that the heat pump system heats hot water in a stepped manner, the heat exchange temperature difference in each grade of condenser is reduced, and the irreversible loss of heat exchange is reduced. The nth stage condenser pressure is greater than the nth-1 stage condenser pressure, …, the 2 nd stage condenser pressure and the 1 st stage condenser pressure, so that graded partial pressure is realized.
The more detailed description is as follows:
when the system integrally operates, each heat pump module independently operates, high-temperature waste hot water from waste heat flows into a waste hot water heat exchange tube 8 in an evaporator through a waste heat inlet tube 1, the high-temperature waste hot water releases heat to a refrigerant in the evaporator 9 through a heat exchange tube wall, two-phase refrigerants in a first refrigerant heat exchange channel 10 absorb heat through evaporation, the temperature of the refrigerant is unchanged, the waste hot water is reduced in heat release temperature, the minimum temperature difference of heat exchange occurs in a waste hot water connecting tube 8 or a waste heat outlet tube 4 at the inlet of the evaporator, generated refrigerant steam enters a compressor 11 and is compressed into high-temperature high-pressure superheated steam, the high-temperature high-pressure superheated steam enters a second refrigerant heat exchange channel 12 to exchange heat with a hot water heat exchange tube 14 in a condenser, the high-temperature high-pressure superheated steam releases heat to hot water through the tube wall of the heat exchange, the hot water absorbs heat to raise the temperature, the minimum temperature difference of heat exchange occurs in a hot water supply connecting pipe 14 or a hot water supply outlet pipe 7 at the outlet of the condenser, the condensed liquid refrigerant has certain supercooling degree, flows out of the condenser 13 and enters a throttle valve 15, the liquid refrigerant is cooled and depressurized through the throttle valve 15 to become a two-phase refrigerant, the two-phase refrigerant enters a first refrigerant heat exchange channel 8 to absorb the heat of the waste hot water again, and the process is repeated.
When the system integrally operates, the parallel multi-stage heat pump modules simultaneously work, and the waste hot water step cooling process is described as that waste hot water with reduced temperature after flowing through the nth stage heat pump module flows into the evaporator 9 of the nth-1 stage single-stage heat pump module through the waste hot water connecting pipe 3, the evaporation temperature of the refrigerant can be correspondingly reduced at the moment due to the reduction of the temperature of the waste hot water, the temperature difference between the inlet temperature of the waste hot water in the n-1 stage heat pump evaporator 9 and the evaporation temperature of the n-1 stage heat pump is not larger than the minimum heat exchange temperature difference, the waste hot water after heat exchange and cooling of the n-1 stage evaporator 9 continuously enters the n-2 stage heat pump evaporator 9 through the waste hot water connecting pipe 3 until reaching the 1 st stage heat pump module, and the waste hot water realizes step cooling in the process and finally flows out from the waste hot water outlet. The evaporation temperature of the refrigerant in the first refrigerant heat exchange channel 8 and the temperature of the corresponding waste hot water at the inlet of the evaporator 9 are maintained to be not more than the minimum heat exchange temperature difference, so that the whole system has a plurality of evaporation temperatures, namely, fractional pressure.
When the system integrally operates, the parallel multi-stage heat pump modules simultaneously work, and the heating process of the hot water flows into the condenser 13 of the 2 nd stage single-stage heat pump module through the hot water supply connecting pipe 6, wherein the temperature of the hot water is increased, the condensing temperature of the refrigerant can be correspondingly increased at the moment, so that the temperature difference between the outlet temperature and the condensing temperature of the hot water in the 2 nd stage heat pump condenser 13 is not more than the minimum heat exchange temperature difference, the hot water after heat exchange and temperature increase in the 2 nd stage condenser 13 continues to enter the 3 rd stage heat pump condenser 13 through the hot water supply connecting pipe 6 until the nth stage heat pump unit, the heating of the hot water is realized in a step manner in the process, the heat energy grade is gradually increased, and finally the hot water flows out from the hot water supply outlet pipe 7 and flows into a user side. The condensing temperature of the refrigerant in the second refrigerant heat exchange channel 12 and the temperature of the corresponding hot water at the outlet of the condenser 13 are maintained to be not more than the minimum heat exchange temperature difference, so that the whole heat pump system has a plurality of condensing temperatures, namely, fractional pressure.
The plurality of single-stage heat pump modules are operated in parallel, and each single-stage heat pump module is independently controlled and does not influence each other. The more the parallel stages are, the more the heat exchange temperature difference between the evaporator and cold water and the heat exchange temperature difference between the condenser and hot water can be reduced, the smaller the heat transfer irreversible loss is, and the higher the energy efficiency of the system is.
Most of the existing heat pump units only have one evaporation temperature and one condensation temperature, and compared with the prior art, the invention has the following performance improvement:
to illustrate the performance improvement more specifically, the conditions of the cold water inlet temperature at the evaporator side of 55 ℃, cooling to the outlet of 50 ℃, and the hot water inlet temperature at the condenser side of 90 ℃, and heating to the outlet of 100 ℃ are taken as examples for explanation. The minimum heat exchange temperature difference between the evaporator and the condenser and water is set to be 2 ℃, the minimum heat exchange temperature difference appears at the water side outlets of the evaporator and the condenser, and a step heat exchange curve chart shown in figure 2 is obtained according to the setting, wherein a solid line represents the temperature change of water, a dotted line represents the refrigerant evaporation temperature, a dotted line represents the refrigerant condensation temperature, and a shaded part in the figure represents the irreversible loss of heat exchange. Fig. 2(a) shows the heat exchange process of the refrigerant and the water in one single-stage heat pump module, fig. 2(b) shows the heat exchange process of the refrigerant and the water in parallel connection of two single-stage heat pump modules, and fig. 2(c) shows the heat exchange process of the refrigerant and the water in parallel connection of three single-stage heat pump modules. Comparing the areas of the shaded portions shown in fig. 2(a), fig. 2(b), and fig. 2(c), it can be seen that as the number of parallel stages increases, the average heat exchange temperature difference between the evaporator, the condenser, and the water at each stage is reduced, and the shaded area decreases, that is, the irreversible loss of heat exchange decreases.
Meanwhile, the multistage heat pump modules are connected in parallel to realize graded partial pressure operation, so that the ratio of the condensing pressure to the evaporating pressure of each heat pump module is similar, namely the operation pressure ratio of the compressor is similar, therefore, the heat pump modules can adopt the compressors of the same model, the cost of the compressor is saved, and the operation and maintenance are convenient.
Further comparing the change condition of the system energy efficiency along with the increase of the parallel series of the heat pumps, wherein the system energy efficiency is defined as COP (coefficient of performance), and the calculation formula is as follows:
wherein Q represents the total heat generated by the heat pump, Q1、Q2…Qn-1、QnThe unit of the heat generated by a single heat pump module is kW; w represents the total power consumed by the heat pump, W1、W2…Wn-1、WnAnd the unit of the power consumption of a single heat pump module is kW.
The system cycle pressure enthalpy diagram of each heat pump module is shown in fig. 3, wherein 1 represents the evaporator inlet, i.e., the compressor inlet, 2 represents the compressor outlet, i.e., the condenser inlet, 3 represents the condenser outlet, i.e., the throttle inlet, and 4 represents the throttle outlet, i.e., the evaporator inlet.
Heat generation Q of each heat pump modulenThe calculation formula is as follows, wherein mnWhen the n-stage heat pump modules are connected in parallel, the unit of the mass flow of the refrigerant in a single heat pump is kg/s, and the mass flow is set to be 10 kg/s. h is2And h3The enthalpy of the refrigerant at the inlet and outlet, respectively, in the condenser is kJ/kg.
Qn＝mn·(h2-h3)
Heat generation W of each heat pump modulenThe calculation formula is as follows, wherein h2And h1The enthalpy of the refrigerant at the inlet and outlet of the compressor, respectively, is expressed in kJ/kg.
Wn＝mn·(h2-h1)
The working medium filled in the heat pump is R1233zd (E), and a change curve of COP along with parallel stages shown in FIG. 4 is obtained through calculation. Compared with a system with two parallel heat pump modules, the COP of the two-stage heat pump module is improved by 8.5%, compared with a system with two parallel heat pump modules, the COP of the three-stage heat pump module is improved by 2.9%, compared with a system with three parallel heat pump modules, the COP of the four-stage heat pump module is improved by 1.4%, compared with a system with four parallel heat pump modules, the COP of the six-stage heat pump module is improved by 0.9%, compared with a system with five-stage heat pump module, the COP of the seven-stage heat pump module is improved by 0.4%, compared with a system with six-stage heat pump module, the COP of the eight-stage heat pump module is improved by 0.33%, and compared with a system with eight-stage heat pump module, the COP of the. After the parallel stage number is greater than 4, more heat pump modules are connected in parallel, and the system performance cannot be obviously improved, namely the parallel stage number is increased to a certain degree, so that the significance of improving the system energy efficiency is not great, and therefore, the appropriate parallel stage number is calculated in advance in practical application.
Fig. 5 shows a control method of the present invention: the user firstly inputs required output temperature T7, the unit measures current heat source temperature Ts and cooling water temperature Th through temperature sensors arranged at the inlet and the outlet of the heat exchanger, further refines the operation control of each heat pump unit, detects the temperature at the minimum heat exchange temperature difference of the heat exchanger in the last stage (Nth stage) heat pump module when starting up, namely the inlet temperature Ti and N of the evaporator and the outlet temperature To and N of the condenser, determines the rotating speed of the compressor according To the saturation pressure corresponding To Ti, N and To and N, detects whether the evaporation temperature of the heat pump module is the inlet temperature Ti and N-2 ℃ after the rotating speed of the compressor reaches the stability, detects whether the condensation temperature is the outlet temperature To and N-2 ℃ of the condenser, if not, detects the inlet temperature Ti and N of the evaporator and the outlet temperature To and N again, and adjusts the rotating speed of the compressor again, until reaching the minimum heat exchange temperature difference of the heat exchanger, the temperature is maintained at 2 ℃. And sequentially starting the compressors of the N-1 and … 1 th-stage heat pump modules, wherein the adjustment methods are the same, after all the parallel-stage heat pump units are started, detecting the final output temperature T7, judging whether the required output temperature T7 is reached, if not, starting readjustment from the N-stage heat pump module until the required output temperature is reached, and keeping each heat pump module to stably operate to obtain stable output. When the load changes, the required output temperature T7 is input again, and the control logic shown in the figure is repeated to realize the dynamic matching of the load. The invention discloses a control method for controlling the operation of a unit, which comprises starting control and load conversion control, wherein the control method comprises the steps of detecting the minimum heat exchange temperature difference of each heat pump module heat exchanger in real time, namely whether the minimum heat exchange temperature difference is reached at the inlet of an evaporator and the outlet of a condenser, feeding back a variable frequency compressor to change the rotating speed, adjusting the evaporation temperature and the condensation temperature until the minimum heat exchange temperature difference is reached, realizing the step heat absorption and the step heat release of the heat pump unit, and ensuring the same pressure ratio of the inlet and the outlet of the compressor of each stage of heat.
In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (10)
1. A fractional modular thermal energy lifting system, comprising a plurality of heat pump modules (2) connected in parallel, the heat pump modules (2) comprising an evaporator (9), a compressor (11), a condenser (13), a throttle valve (15);
the evaporator (9) comprises a waste hot water heat exchange pipe (8) and a first refrigerant heat exchange channel (10);
the condenser (13) comprises a second refrigerant heat exchange channel (12) and a hot water supply heat exchange tube (14);
the first refrigerant heat exchange channel (10), the compressor (11), the second refrigerant heat exchange channel (12) and the throttle valve (15) are connected end to realize closed circulation;
the waste hot water heat exchange pipes (8) of the adjacent heat pump modules (2) are communicated;
the hot water supply heat exchange pipes (14) of the adjacent heat pump modules (2) are communicated.
2. A staged partial pressure modular thermal energy lifting system according to claim 1, characterized in that the waste hot water heat exchange tubes (8) of adjacent heat pump modules (2) are connected by a waste hot water connection tube (3).
3. A staged partial pressure modular thermal energy lifting system according to claim 1, wherein the hot water heat exchange tubes (14) of adjacent heat pump modules (2) are in communication by means of hot water connecting tubes (6).
4. The staged partial pressure modular thermal energy lifting system of claim 1,
waste hot water enters from a waste hot water heat exchange tube (8) of the last stage heat pump module and flows out from the waste hot water heat exchange tube (8) of the first stage heat pump module;
hot water enters from a hot water supply heat exchange pipe (14) of the first-stage heat pump module and flows out from the last-stage hot water supply heat exchange pipe (14).
5. The staged partial pressure modular thermal energy lifting system according to claim 4, wherein in the waste hot water circulation direction, the pressure of the evaporator (9) of the heat pump module decreases and the pressure of the condenser (13) of the heat module decreases.
6. The staged partial pressure modular thermal energy lifting system of claim 1, wherein the evaporator and condenser employ falling film or flooded heat exchangers.
7. The staged partial pressure modular thermal energy boosting system of claim 1, wherein the heat pump modules employ inverter compressors.
8. The staged partial pressure modular thermal energy boosting system of claim 1, wherein the number of heat pump modules is from 4 to 9 stages.
9. A control method for a graded partial pressure modular thermal energy lifting system based on any one of claims 1-8, characterized by comprising the following steps:
a set temperature input step: inputting a desired output temperature T7;
a detection step: measuring the current heat source temperature Ts and the cooling water temperature Th;
a rotating speed determining step: detecting heat pump module evaporator inlet temperature Ti,NAnd condenser outlet temperature To,NAccording to Ti,NAnd To,NDetermining the rotating speed of the compressor corresponding to the saturation pressure;
a temperature judgment step: after the rotating speed of the compressor reaches the stability, whether the evaporation temperature of the heat pump module is the inlet temperature T or not is detectedi,N-x ℃, detecting whether the condensing temperature is the outlet temperature T of the condensero,NAt the temperature of-x ℃, if the judgment result is yes, entering a next-stage heat pump module, and entering a rotating speed determining step; if the judgment result is no, the inlet temperature T of the evaporator at the moment is detected againi,NTemperature T at the outlet of the condensero,NThe rotating speed of the compressor is regulated again until the minimum heat exchange temperature difference of the heat exchanger is maintained at x ℃;
an output step: outputting a final temperature T7, judging whether the required output temperature T7 is reached, and if so, maintaining the state operation; if the judgment result is negative, the last stage of heat pump module starts to adjust again until the required output temperature is reached, and each heat pump module is kept to operate stably to obtain stable output.
10. The control method of claim 9, wherein x is a minimum heat exchange temperature difference.
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