A control method for a transcritical carbon dioxide air source heat pump steam unit

Abstract

The present invention discloses a control method for a transcritical carbon dioxide air source heat pump steam unit, which is applied to the technical field of air source heat pumps. The unit includes a steam generator, a gas cooler 1 and a spray device are provided in the steam generator, and the steam generator is provided with a steam outlet and a circulating water outlet. The unit also includes a heat pump compressor, a four-way reversing valve, a throttling device, a gas-liquid separator, a gas cooler 2, a steam generator, a water pump, a water vapor compressor, a vacuum pump, an evaporator, a regenerator and a monitoring component; the control method is a method for determining the optimal solution of the vacuum pump, the throttling device, the liquid level and the water vapor compressor within the normal working range of the unit to minimize the total input power of the unit; the present invention can utilize the high exhaust temperature of the carbon dioxide heat pump compressor to combine surface heating evaporation with flash evaporation to generate steam. Compared with traditional air source heat pump steam engines, the steam supply is increased, and the energy efficiency of the system is improved, which is more energy-saving.

Description

Technical Field

[0001] The present invention relates to the technical field of air source heat pumps, and in particular to a control method for a transcritical carbon dioxide air source heat pump steam unit. Background Art

[0002] 50% to 70% of my country's industrial energy consumption is consumed in the form of thermal energy, most of which is high-temperature thermal energy demand above 80°C. Traditional high-temperature heating uses coal-fired, oil-fired, gas-fired boilers or electric boilers, which have problems such as low efficiency and high pollution. Air source heat pumps, as an efficient and clean heating method, have been widely used in the field of medium and low temperature heating. However, due to the limitations of refrigerants and refrigeration systems, it is difficult to achieve a large temperature rise, resulting in the production of steam products above 100°C using air source heat pump technology. The existing technology generally uses an air source heat pump to first heat low-temperature water to high-temperature saturated water above 80°C. The high-temperature saturated water enters the low-pressure flash tank directly or after being reduced in pressure by a pressure reducing valve to produce micro-pressure steam, and then is compressed by a water vapor compressor to obtain high-temperature and high-pressure steam that meets user needs. The above-mentioned method of generating steam by using a low-pressure flash tank has a limited amount of steam generated for a flash tank with a fixed vacuum degree. If the steam production is to be increased, the vacuum degree of the flash tank needs to be increased, but the pressure and temperature of the steam generated are lower, which in turn makes the energy consumption of maintaining the negative pressure environment of the flash tank and the water vapor compressor higher, resulting in low energy efficiency of the entire system.

[0003] In view of the above problems, the present invention provides a control method for a transcritical carbon dioxide air source heat pump steam engine. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiency of the limited steam output of the above-mentioned air source heat pump in the prior art, and to provide a control method for a transcritical carbon dioxide air source heat pump steam unit. The method can utilize the high exhaust temperature of the carbon dioxide heat pump compressor to combine surface heating evaporation with flash evaporation to generate steam. Compared with traditional air source heat pump steam engines, the method increases the steam supply, improves the system energy efficiency, and is more energy-saving.

[0005] In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions: a transcritical carbon dioxide air source heat pump steam unit, which includes a steam generator used in an air source heat pump heating system, the top of the steam generator is provided with a steam outlet, the bottom of the steam generator is provided with a circulating water outlet, the internal space of the steam generator is provided with a gas cooler and a spray device, the spray device is installed in the upper part of the internal space, the gas cooler is installed below the spray hole of the spray device, the gas cooler is provided with a gas outlet and a gas inlet at the shell of the steam generator, and the bottom of the internal space is used for liquid storage.

[0006] The internal space of the steam generator is provided with a gas cooler 1 through which carbon dioxide is introduced. Hot water entering the steam generator through a spray device is stored at the bottom of the internal space, wherein carbon dioxide enters the gas cooler 1 through a gas inlet or a gas outlet. High-temperature hot water enters the steam generator through the spray device to produce evaporation in two processes. One is direct flash evaporation to produce steam after entering, and the other is hot water sprayed on the surface of the gas cooler 1 to exchange heat with the high-temperature carbon dioxide in the gas cooler 1. The high-temperature hot water evaporates on the surface of the gas cooler 1 to produce steam, and at the same time, the high-temperature carbon dioxide in the gas cooler 1 is cooled. The high exhaust temperature of the carbon dioxide heat pump compressor can be utilized to combine surface heating evaporation with flash evaporation to produce steam. Compared with traditional air source heat pump steam engines, the steam supply is increased, and the system energy efficiency is improved, which is more energy-saving.

[0007] In a preferred embodiment of the present invention, the above-mentioned unit also includes a gas cooler 2, which is connected to the gas outlet or gas inlet through a pipeline, and the gas cooler 2 is connected to the spray device through a pipeline, the pipeline for water replenishment and circulation is connected to the gas cooler 2, and the pipeline for circulation is connected to the circulating water outlet; the steam generator discharges the relatively cooled water inside through the circulating water outlet, and the carbon dioxide gas cooled by the gas cooler 1 is cooled for the second time through the gas cooler 2, and the high-temperature hot water heated by the gas cooler 2 can also be provided to the spray device for recycling.

[0008] In a preferred embodiment of the present invention, the above-mentioned unit also includes a water pump, which is installed on the pipeline between gas cooler 2 and the spray device; water is transported from gas cooler 2 to the spray device through the water pump, providing high-temperature hot water to the steam generator.

[0009] In a preferred embodiment of the present invention, the above-mentioned unit further includes a vacuum pump, which is connected to the steam generator; the vacuum pump is used to evacuate the steam generator to maintain a vacuum environment in the steam generator.

[0010] In a preferred embodiment of the present invention, the above-mentioned unit also includes a water vapor compressor, the inlet of the water vapor compressor is connected to the steam outlet through a pipeline, and the outlet of the water vapor compressor is connected to the user through a pipeline; the water vapor discharged from the steam outlet is pressurized and heated by the water vapor compressor, and high-temperature and high-pressure steam is output to the outside.

[0011] In a preferred embodiment of the present invention, the above-mentioned unit also includes a water supply valve and a circulating water valve. The circulating water valve is installed on the circulation pipe at the circulating water outlet, and the water supply valve is installed on the water supply pipe; the high-temperature hot water entering the steam generator is circulated through the circulating water valve, and then enters the gas cooler 2 to further cool the carbon dioxide gas, and the water supplied to the spraying device is supplemented through the water supply valve.

[0012] In a preferred embodiment of the present invention, the above-mentioned unit also includes a four-way reversing valve, which includes four ports a, b, c, and d. End a is connected to the gas inlet through a pipeline, end b is connected to the heat pump compressor through a pipeline, end c is connected to the gas-liquid separator through a pipeline, the gas-liquid separator is used to separate carbon dioxide gas and return it to the heat pump compressor, and end d is connected to the heat exchange component through a pipeline; when heating, end a and end b are connected, and end c and end d are connected; when defrosting, end a and end c are connected, and end b and end d are connected; through the setting of ends a, b, c, and d of the four-way reversing valve, it can be switched to the heating mode, and the high-temperature and high-pressure gas is introduced into the steam generator to generate steam, and then heat exchange is carried out through the heat exchange device, and finally returned to the heat pump compressor. At the same time, it can also be switched to the defrosting mode, and the high-temperature and high-pressure gas first passes through the heat exchange component and then enters the gas cooler and steam generator, and finally returns to the heat pump compressor.

[0013] In a preferred embodiment of the present invention, the above-mentioned heat exchange component includes an evaporator and a regenerator, the regenerator is connected to the gas cooler 2 through a pipeline, the regenerator is connected to the d end of the four-way reversing valve through a pipeline, the regenerator is connected to the evaporator through a pipeline, and then connected to the regenerator through a pipeline after passing through the evaporator. A throttling device is provided on the pipeline between the regenerator and the evaporator, and a fan is provided at the evaporator; the arrangement of the regenerator and the evaporator can carry out heat exchange, thereby realizing the cooling of the gas discharged from the gas cooler 2 and the heating of the gas after passing through the evaporator.

[0014] In a preferred embodiment of the present invention, the above-mentioned unit also includes a monitoring component, which includes a power collector, a pressure sensor, a liquid level sensor, a temperature sensor 1, a temperature sensor 2 and a temperature sensor 3. The power collector is connected to the heat pump compressor, the fan, the water pump, the water vapor compressor and the vacuum pump respectively. The pressure sensor is connected to the steam generator. The liquid level sensor is placed at the bottom of the internal space and is used to monitor the liquid level of the stored liquid. The temperature sensor 1 is arranged on the outlet pipe of the gas cooler 2 connected to the spray device, the temperature sensor 2 is arranged on the outlet pipe connected to the heat pump compressor, and the temperature sensor 3 is arranged on the outlet pipe connected to the water vapor compressor. The power collector is used to monitor the input power of each device, the pressure sensor is used to monitor the pressure in the steam generator to ensure the vacuum environment in the steam generator, the liquid level sensor is used to monitor the hot water level in the steam generator to ensure that the liquid level fluctuates within the required range, and the temperature sensor 1, the temperature sensor 2 and the temperature sensor 3 are used to monitor the fluid temperature at the outlet of the gas cooler 2, the heat pump compressor and the water vapor compressor to maintain normal operation.

[0015] A control method for a transcritical carbon dioxide air source heat pump steam unit adopts the above-mentioned transcritical carbon dioxide air source heat pump steam unit, and the control method includes the following steps: S1, establishing a system input total power function W of each device, the devices including a water pump, a vacuum pump, a heat pump compressor, a water vapor compressor and a fan; S2, starting each of the above-mentioned devices, setting the maximum liquid level Hws (max) and minimum liquid level Hws (min) of the steam generator, setting the outlet target steam temperature Tss and the return temperature ΔTs of the water vapor compressor, setting the pressure Ps and the return pressure ΔP of the internal space of the steam generator, setting the exhaust return temperature ΔTp of the heat pump compressor, the outlet hot water return temperature ΔTw of the gas cooler 2, and the difference ΔTwp between the target exhaust temperature Tps of the heat pump compressor and the target water temperature Tws of the gas cooler 2; S3, setting the target pressure Ps of the internal space of the steam generator, dividing the setting range into multiple controllable target pressure points Ps1, Ps2, Ps3, ..., Psi, ..., Psn from high to low. (1≤i≤n), where Ps1=0.1 Mpa, Psn=0.05MPa; S4, set the outlet target water temperature Tws of the gas cooler 2 to the saturated steam temperature corresponding to Ps; S5, calculate the target exhaust temperature Tps of the heat pump compressor according to the outlet target water temperature Tws of the gas cooler 2, Tps= Tws+ΔTwp; S6, monitor the temperature of each location through temperature sensor 1, temperature sensor 2, and temperature sensor 3, monitor the internal space pressure P of the steam generator through the pressure sensor, and monitor the power of each device through the power collector; S7, determine whether the internal pressure P of the steam generator reaches the target pressure Ps, if Ps≥P+ΔP, load through the vacuum pump, if Ps≤P-ΔP, reduce the load through the vacuum pump, otherwise maintain the current state; S8, determine whether the exhaust temperature Tp reaches the target exhaust temperature Tps, if Tp≥Tps+ΔT p, then increase the opening of the throttling device; if Tp ≤ Tps-ΔTp, then reduce the opening of the throttling device; otherwise, maintain the current state; S9, determine whether the liquid level height Hw reaches the target liquid level maximum value Hws(max) or minimum value Hws(min); if Hw ≥ Hws(max), then reduce the opening of the water supply valve; if Hw ≤ Hws(min), then increase the opening of the water supply valve; if it does not reach Hws(max) or Hws(min), then determine whether the gas cooler second outlet water temperature Tw reaches the target water temperature Tws; if Tw ≥ Tws+ΔTw, then increase the opening of the water supply valve; if Tw ≤ If Tws-ΔTw, reduce the opening of the water supply valve, otherwise maintain the current state; S10, determine whether the steam temperature Ts at the outlet of the water vapor compressor reaches the target steam temperature Tss, if Ts≥Tss+ΔTs, reduce the load of the water vapor compressor, if Ts≤Tss-ΔTs, load the water vapor compressor, otherwise maintain the current state; S11, after the unit is running stably, calculate the total system input power W (Psi) corresponding to the current Psi; S12, determine whether i>1 is satisfied, if not, set For i=i+1 and Ps=Psi, repeat steps S4-S11 until i>1. If W(Psi)>W(Ps(i-1)), then determine Ps(i-1) as the optimal target pressure for the steam generator, minimizing the total system input power. Otherwise, set i=i+1 and Ps=Psi, and repeat steps S4-S11 until W(Psi)>W(Ps(i-1)). Then determine Ps(i-1) as the optimal target pressure for the steam generator, minimizing the total system input power W.

[0016] Through S1, a function of the total input power of the system is established. Since the steam generator has an optimal pressure to minimize the function value, it is easy to obtain the optimal solution. Through the setting of S2, the unit can maintain normal operation within a certain range. Through S3 to limit the boundary conditions, the amount of calculation is also reduced. Through S4 and S5, it is easy to calculate the target water temperature and target exhaust temperature. Through S6, the temperature and power of each monitoring position are monitored. Through S7, the optimal efficiency of the vacuum pump is adjusted. Through S8, the optimal efficiency of the throttling device is adjusted. Through S9, the optimal position of the liquid level in the steam generator is adjusted. Through S10, the optimal efficiency of the water vapor compressor is adjusted. Through S11-S12, the optimal solution of the total input power of the system is obtained, the optimal power of each device is determined, and the lowest energy consumption is achieved.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This transcritical CO2 air source heat pump steam unit can utilize the high exhaust temperature of the CO2 heat pump compressor to combine surface heating evaporation with flash evaporation to generate steam. Compared with traditional air source heat pump steam engines, it increases the steam supply and improves the system energy efficiency, making it more energy-efficient.

[0019] 2. This control method starts by establishing a function of the total system input power. Then, based on the target steam temperature, target water temperature, and target exhaust temperature, combined with real-time monitored temperature, power, and liquid level data, the optimal solutions for the vacuum pump, throttling device, steam generator, and water vapor compressor are determined in sequence, thereby determining the optimal power of each device, achieving minimum energy consumption, and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a system schematic diagram of the transcritical carbon dioxide air source heat pump steam unit of the present invention;

[0021] Figure 2 Schematic diagram of the structure of the steam generator of the present invention; Figure 3 This is a flow chart of the control method of the transcritical carbon dioxide air source heat pump steam unit of the present invention.

[0022] Markings in the figure:

[0023] 1-heat pump compressor, 2-four-way reversing valve, 3-regenerator, 4-throttling device, 5-evaporator, 6-fan, 7-gas-liquid separator, 8-gas cooler 2, 9-steam generator, 10-water pump, 11-vapor compressor, 12-water supply valve, 13-circulating water valve, 14-vacuum pump, 15-power collector, 16-temperature sensor 1, 17-temperature sensor 2, 18-temperature sensor 3, 91-gas cooler 1, 92-circulating water outlet, 93-liquid level sensor, 94-spray device, 95-steam outlet, 96-pressure sensor. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, this should not be understood as limiting the scope of the present invention to the following embodiments, and all technologies implemented based on the present invention fall within the scope of the present invention.

[0025] Example 1

[0026] Please refer to Figure 1 The present embodiment provides a transcritical carbon dioxide air source heat pump steam unit, which includes a heat pump compressor 1, a four-way reversing valve 2, a throttling device 4, a gas-liquid separator 7, a gas cooler 2 8, a steam generator 9, a water pump 10, a water vapor compressor 11, a water supply valve 12, a circulating water valve 13, a vacuum pump 14 and a heat exchange component and a monitoring component. The heat exchange component includes an evaporator 5 and a regenerator 3. The evaporator 5 is also provided with a fan 6. The monitoring component includes a power collector 15, a pressure sensor 96, a liquid level sensor 93, a temperature sensor 16, a temperature sensor 2 17 and a temperature sensor 3 18. The above components of the present embodiment are all devices or equipment currently used in air source heat pumps; the steam generator 9 of the unit combines the surface evaporation of high-temperature hot water with flash evaporation internally, and can utilize the high exhaust temperature of the carbon dioxide heat pump compressor 1 to combine surface heating evaporation with flash evaporation to generate steam. Compared with traditional air source heat pump steam engines, the steam supply is increased, and the system energy efficiency is improved, which is more energy-saving.

[0027] In this embodiment, the four-way reversing valve 2 includes four ports a, b, c, and d. End a, end b, end c, and end d can be connected through the interior of the four-way reversing valve 2. The heat pump compressor 1 is connected to end b of the four-way reversing valve 2 through a pipeline. The gas inlet of the steam generator 9 is connected to end a of the four-way reversing valve 2 through a pipeline. The gas outlet of the steam generator 9 is connected to the gas cooler 2 8 through a pipeline. The gas cooler 2 8 is also connected to three other pipes, one of which is connected to the regenerator 3 as a gas channel, and the other two pipes are used as pipes for water replenishment and circulation and pipes for supplying water to the spray device 94 respectively. The pipe for water replenishment and circulation includes a section of pipe connected to the gas cooler 2 8, and the pipe branched out into two, one is connected to the circulating water outlet 92 and serves as a pipe for circulation. The pipe for circulation is provided with a circulating water valve 13, and the other is connected to the water source and serves as a pipe for water replenishment. The pipe for water replenishment is provided with a water replenishment valve 12, and the water supplied to the spray device 94 is replenished through the water replenishment valve 12. The last pipe for water supply is connected to the spray device 94, and the carbon dioxide gas cooled by the gas cooler 1 91 is cooled for a second time by the gas cooler 2 8. The high-temperature hot water heated by the gas cooler 2 8 can also be provided to the spray device 94 for recycling. Regenerator 3 is equipped with four pipes, of which pipe 1 is connected to gas cooler 2 8. After passing through regenerator 3, gas enters evaporator 5 through pipe 2. Pipe 2 is equipped with a throttling device 4, which is a throttle valve. Evaporator 5 is equipped with a fan 6 for dissipating heat from evaporator 5. Evaporator 5 is connected to regenerator 3 via pipe 3. The arrangement of regenerator 3 and evaporator 5 enables heat exchange, cooling the gas exiting gas cooler 2 8 and heating the gas after passing through evaporator 5. Regenerator 3 is connected to end d of four-way reversing valve 2 via pipe 4. End c of four-way reversing valve 2 is connected to gas-liquid separator 7 via a pipe. Gas-liquid separator 7 is connected to heat pump compressor 1 via a pipe. The carbon dioxide separated by gas-liquid separator 7 is returned to heat pump compressor 1 through the pipe connected to heat pump compressor 1 for further heating and pressurization.

[0028] In this embodiment, since the four-way reversing valve 2 can be used for reversing connection of the internal interface, when used for heating, the a end and the b end are connected, and the c end and the d end are connected. At this time, the ab channel and the cd channel are formed inside the four-way reversing valve 2 respectively. The high-temperature and high-pressure carbon dioxide enters the gas inlet of the steam generator 9 after passing through the four-way reversing valve 2, and the carbon dioxide passing through the evaporator 5 and the regenerator 3 enters the gas-liquid separator 7 after passing through the four-way reversing valve 2; when used for defrosting, the a end and the c end are connected, and the b end and the d end are connected. At this time, the ac channel and the bd channel are formed inside the four-way reversing valve 2 respectively. The gas inlet and the gas inlet of the steam generator 9 are connected. The functions of the outlets are interchanged. The high-temperature and high-pressure carbon dioxide passes through the four-way reversing valve 2 and then passes through the regenerator 3 and the evaporator 5. The carbon dioxide discharged from the steam generator 9 passes through the four-way reversing valve 2 and then enters the gas-liquid separator 7. Through the settings of the a, b, c, and d ends of the four-way reversing valve 2, it can be switched to the heating mode, and the high-temperature and high-pressure gas is introduced into the steam generator 9 to generate steam, and then heat exchange is performed through the heat exchange device, and finally flows back to the heat pump compressor 1. At the same time, it can also be switched to the defrosting mode, and the high-temperature and high-pressure gas first undergoes heat exchange and then enters the gas cooler and steam generator 9, and finally flows back to the heat pump compressor 1.

[0029] In this embodiment, the steam generator 9 has a device shell, which contains the internal space of the steam generator 9. A gas cooler 91 and a spray device 94 are provided in the shell. An interface is provided on the top of the shell and serves as a steam outlet 95 for discharging steam. The interface is connected to the water vapor compressor 11 through a pipeline. The outlet of the water vapor compressor 11 is connected to the user through a pipeline. The water vapor discharged from the steam outlet 95 is pressurized and heated by the water vapor compressor 11, and high-temperature and high-pressure steam is output to the outside. A vacuum pump 14 is also provided on the top of the shell. The vacuum pump 14 is used to evacuate the steam generator 9 to make the steam generator 9 To maintain a vacuum environment, a pressure sensor 96 is provided on the top of the shell. The pressure in the steam generator 9 is monitored by the pressure sensor 96 to ensure the vacuum environment in the steam generator 9. An interface is provided at the bottom of the shell and serves as a circulating water outlet 92 for cooled water. The interface is connected to a pipe for replenishing water through a drainage pipe. The relatively cooled water in the steam generator 9 is collected through the circulating water outlet 92. A circulating water valve 13 is provided on the drainage pipe. The high-temperature hot water entering the steam generator 9 is recycled through the circulating water valve 13 and then enters the gas cooler 8 to further cool the carbon dioxide gas.

[0030] Please refer to Figure 2In this embodiment, the spray device 94 is an existing device with multiple groups of spray holes. The spray device 94 is installed in the upper part of the internal space of the steam generator 9, and the gas cooler 91 is installed below the spray holes of the spray device 94. The high-temperature hot water sprayed from the spray device 94 can be directly sprayed on the surface of the gas cooler 91. The high-temperature hot water enters the steam generator 9 through the spray device 94 and evaporates in two processes. One is that the hot water directly flashes to generate steam after entering, and the other is that the hot water is sprayed on the surface of the gas cooler 91 to exchange heat with the high-temperature carbon dioxide in the gas cooler 91. The high-temperature hot water evaporates on the surface of the gas cooler 91 to generate steam, and at the same time, the high-temperature carbon dioxide in the gas cooler 91 is cooled. Gas cooler 1 91 is equipped with two interfaces on the shell of steam generator 9, one serving as a gas outlet and the other as a gas inlet. The gas outlet and gas inlet can be switched between the heating and defrosting operating modes. The bottom of the internal space of steam generator 9 is used for liquid storage. The liquid level of the stored liquid is always located below gas cooler 1 91. An existing liquid level sensor 93 is used, which is placed at the bottom of the internal space and used to monitor the liquid level of the stored liquid. The liquid level sensor 93 is used to monitor the hot water level in steam generator 9 to ensure that the liquid level fluctuates within the required range. Gas cooler 2 8 is connected to a spray device 94 via a pipeline. A water pump 10 is installed on the pipeline. Water is transported from gas cooler 2 8 to the spray device 94 by water pump 10, providing high-temperature hot water to the steam generator 9.

[0031] In this embodiment, the monitoring component also includes a power collector 15, a temperature sensor 16, a temperature sensor 2 17 and a temperature sensor 3 18. The power collector 15 is electrically connected to the heat pump compressor 1, the fan 6, the water pump 10, the water vapor compressor 11 and the vacuum pump 14 through wiring, and the input power of each device is monitored through the power collector 15; the temperature sensor 16 is arranged on the outlet pipe of the gas cooler 2 8 connected to the spray device 94, and the water temperature at the outlet of the gas cooler 2 8 is monitored by the temperature sensor 16, the temperature sensor 2 17 is arranged on the outlet pipe connected to the heat pump compressor 1, and the carbon dioxide temperature at the outlet of the heat pump compressor 1 is monitored by the temperature sensor 2 17, the temperature sensor 3 18 is arranged on the outlet pipe connected to the water vapor compressor 11, and the steam temperature output by the water vapor compressor 11 is monitored by the temperature sensor 3 18 to maintain normal operation.

[0032] The following describes the operating principle of the unit in this embodiment, including the normal heating principle of the system and the defrosting principle of the system.

[0033] The refrigerant cycle process for the normal heating system is as follows: Ends a and b of four-way reversing valve 2 are connected, and ends c and d are connected. Low-temperature, low-pressure carbon dioxide is compressed by heat pump compressor 1 to produce high-temperature, high-pressure carbon dioxide. This carbon dioxide enters gas cooler 1 91 through channels ab of four-way reversing valve 2, where it is cooled by heat exchange with high-temperature hot water sprayed by spray device 94. It then exchanges heat with low-temperature water in gas cooler 2 8 for further cooling. It then enters regenerator 3 and exchanges heat with the carbon dioxide at the outlet of evaporator 5 for further cooling. The cooled carbon dioxide then enters throttling device 4 for throttling and pressure reduction, before entering evaporator 5 to exchange heat with air for evaporation. It then flows through regenerator 3 and exchanges heat with the carbon dioxide at the outlet of gas cooler 2 8, where it is heated to increase the return gas superheat. It then enters heat pump compressor 1 through channels cd of four-way reversing valve 2 and gas-liquid separator 7, completing a heating cycle.

[0034] Water circulation process: Turn on the water pump 10 and the vacuum pump 14, and the water stored at the bottom of the steam generator 9 enters the system's make-up water through the circulating water outlet 92, the circulating water valve 13 and the make-up water valve 12 to mix, flow through the gas cooler 2 8, exchange heat with carbon dioxide and be heated to produce high-temperature hot water, and the water pump 10 transports the high-temperature hot water to the spray device 94, and the spray device 94 sprays and atomizes the high-temperature hot water. Part of the hot water directly flashes to produce steam, and the rest falls on the surface of the gas cooler 1 91, exchanges heat with the high-temperature carbon dioxide at the outlet of the heat pump compressor 1, and part of the high-temperature hot water is heated and evaporated to produce steam. The steam enters the water vapor compressor 11 through the steam outlet 95 on the upper part of the steam generator 9 and is compressed to increase the temperature and pressure of the steam to meet the needs of users; the remaining unevaporated liquid water flows into the bottom of the steam generator 9.

[0035] System defrosting principle: When the unit is operating in heating mode and meets defrost conditions, ends a and c, and ends b and d, of four-way reversing valve 2 are connected. Low-temperature, low-pressure carbon dioxide is compressed by heat pump compressor 1 to produce high-temperature, high-pressure carbon dioxide. This high-temperature, high-pressure carbon dioxide enters regenerator 3 through channels bd of four-way reversing valve 2, exchanges heat with the carbon dioxide at the outlet of throttling device 4, and then enters evaporator 5 for heat exchange and cooling, providing the heat required for defrosting evaporator 5. The cooled carbon dioxide is throttled and depressurized by throttling device 4, then enters regenerator 3 for heat exchange and heating with the carbon dioxide at the outlet of the heat pump compressor. It then passes through gas cooler 2 8 and gas cooler 1 91 in sequence to absorb heat, and finally enters heat pump compressor 1 through channels ac of four-way reversing valve 2 and gas-liquid separator 7, completing a defrost cycle.

[0036] Example 2

[0037] Please refer to Figure 3This embodiment provides a control method for a transcritical carbon dioxide air-source heat pump steam unit. Using the transcritical carbon dioxide air-source heat pump steam unit of Example 1, the control method includes the following steps: S1. For the above-mentioned transcritical carbon dioxide air-source heat pump steam unit system, if the circulating water flow rate is constant and steam of a certain temperature is generated at the outlet of the water vapor compressor 11, the lower the pressure in the steam generator 9, the lower the corresponding saturated steam temperature, the lower the input power of the heat pump compressor 1 and the fan 6, and the higher the input power of the vacuum pump 14 and the water vapor compressor 11. Conversely, the higher the pressure in the steam generator 9, the higher the corresponding saturated steam temperature, the higher the input power of the heat pump compressor 1 and the fan 6, and the lower the input power of the vacuum pump 14 and the water vapor compressor 11. Therefore, there is an optimal pressure in the steam generator 9, which makes the system input power the lowest. Based on this, the system control objective function is: minW=W1+W2+W3+W4+W5, where W is the total input power of the system, W1 is the input power of the heat pump compressor 1, W2 is the input power of the fan 6, W3 is the input power of the water pump 10, W4 is the input power of the water vapor compressor 11, and W5 is the input power of the vacuum pump 14; the function of the total input power of the system is established through S1, and since the steam generator 9 has an optimal pressure, the function value is minimized, which makes it easy to obtain the optimal solution.

[0038] S2. After the system is started, set the maximum value Hws(max) and minimum value Hws(min) of the target liquid level height at the bottom of the steam generator 9, set the target steam temperature Tss (settable range 100~150℃) and the hysteresis temperature ΔTs (settable range 2~5℃) at the outlet of the water vapor compressor 11, set the target pressure Ps (settable range 0.05~0.1 MPa) and the hysteresis pressure ΔP (set to 0.005 MPa) of the internal space of the steam generator 9, set the exhaust hysteresis temperature ΔTp (settable range 2~5℃) of the heat pump compressor 1, set the hot water hysteresis temperature ΔTw (settable range 2~5℃) at the outlet of the gas cooler 2 8, and set the difference ΔTwp between the target exhaust temperature Tps of the heat pump compressor 1 and the target water temperature Tws at the outlet of the gas cooler 2 8 (settable range 5~15℃); through the settings of S2, the unit can maintain normal operation within a certain range.

[0039] S3. Divide the target pressure Ps of the internal space of the steam generator 9 into multiple controllable target pressure points Ps1, Ps2, Ps3, ..., Psi, ..., Psn (1≤i≤n) from high to low within the setting range, where Ps1=0.1 MPa, Psn=0.05 MPa, and set the initial Ps=Ps1; by limiting the boundary conditions in S3, the amount of calculation is also reduced.

[0040] S4. Set the target water temperature Tws at the outlet of the gas cooler 2 8 to the saturated steam temperature corresponding to Ps. The calculation formula is the formula used in the industry: S5. Calculate the target exhaust temperature Tps = Tws + ΔTwp of the heat pump compressor 1 based on Tws. Through S4 and S5, it is easy to calculate the target water temperature and target exhaust temperature.

[0041] S6. Temperature sensor 1 detects the outlet water temperature Tw of gas cooler 2 8 via temperature sensor 16, the exhaust temperature Tp of heat pump compressor 1 via temperature sensor 2 17, the steam temperature Ts of vapor compressor 11 via temperature sensor 3 18, the liquid level Hw at the bottom of steam generator 9 via liquid level sensor 93, and the pressure P within steam generator 9 via pressure sensor 96. Power collector 15 collects the input power W1 of heat pump compressor 1, the input power W2 of fan 6, the input power W3 of water pump 10, the input power W4 of vapor compressor 11, and the input power W5 of vacuum pump 14. Temperature and power monitoring at each monitoring location is achieved through S6.

[0042] S7. Determine whether the pressure P of the internal space of the steam generator 9 reaches the target pressure Ps. If Ps≥P+ΔP, the vacuum pump 14 is loaded. If Ps≤P-ΔP, the vacuum pump 14 is unloaded. Otherwise, the vacuum pump 14 maintains the current state. The vacuum pump 14 is adjusted to achieve optimal efficiency through S7.

[0043] S8. Determine whether the exhaust temperature Tp reaches the target exhaust temperature Tps. If Tp ≥ Tps + ΔTp, increase the opening of the throttling device 4. If Tp ≤ Tps - ΔTp, reduce the opening of the throttling device 4. Otherwise, maintain the opening of the throttling device 4. Adjust the throttling device 4 to achieve optimal efficiency through S8.

[0044] S9. Determine whether the liquid level height Hw has reached the target maximum liquid level height Hws(max) or minimum liquid level Hws(min). If Hw ≥ Hws(max), reduce the opening of the water supply valve 12; if Hw ≤ Hws(min), increase the opening of the water supply valve 12. Otherwise, determine whether the outlet water temperature Tw of the gas cooler 2 8 has reached the target water temperature Tws. If Tw ≥ Tws+ΔTw, increase the opening of the water supply valve 12; if Tw ≤ Tws-ΔTw, reduce the opening of the water supply valve 12; otherwise, maintain the opening of the water supply valve 12. Adjustment of the optimal liquid level position in the steam generator 9 is achieved through S9.

[0045] S10. Determine whether the outlet steam temperature Ts of the water vapor compressor 11 reaches the target steam temperature Tss. If Ts≥Tss+ΔTs, the water vapor compressor 11 is unloaded. If Ts≤Tss-ΔTs, the water vapor compressor 11 is loaded. Otherwise, the water vapor compressor 11 maintains the current state. The optimal efficiency adjustment of the water vapor compressor 11 is achieved through S10.

[0046] S11. After the system runs stably, calculate the total system input power W(Psi) corresponding to the current Psi = W1(Psi)+W2(Psi)+W3(Psi)+W4(Psi)+W5(Psi).

[0047] S12. Determine whether i>1 is satisfied. If not, let i=i+1 and Ps=Psi, and repeat steps (4) to (11) until i>1. If W(Psi)>W(Ps(i-1)), then determine Ps(i-1) as the optimal target pressure of the steam generator 9 so that the total input power of the system is the lowest. Otherwise, let i=i+1 and Ps=Psi, and repeat steps (4) to (11) until W(Psi)>W(Ps(i-1)), then determine Ps(i-1) as the optimal target pressure of the steam generator 9 so that the total input power of the system is the lowest. Obtain the optimal solution of the total input power of the system through S11-S12, determine the optimal power of each device, and achieve the lowest energy consumption.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A control method for a transcritical carbon dioxide air source heat pump steam unit, characterized in that: A transcritical carbon dioxide air source heat pump steam unit is used, comprising a steam generator (9) used in an air source heat pump heating system, wherein the top of the steam generator (9) is provided with a steam outlet (95), the bottom of the steam generator (9) is provided with a circulating water outlet (92), the internal space of the steam generator (9) is provided with a gas cooler (91) and a spray device (94), the spray device (94) is installed at the upper part of the internal space, and the gas cooler (91) is installed below the spray hole of the spray device (94). The gas cooler 1 (91) is provided with a gas outlet and a gas inlet at the shell of the steam generator (9), and the bottom of the internal space is used for liquid storage. The gas cooler 2 (8) is connected to the gas outlet or the gas inlet through a pipeline, and the gas cooler 2 (8) is connected to the spray device (94) through a pipeline. The pipeline for water replenishment and circulation is connected to the gas cooler 2 (8), and the other end of the pipeline for circulation is connected to the circulating water outlet (92). The gas cooler 1 (91) also includes a water pump (10), and the water pump (10) is provided on the pipeline between the gas cooler 2 (8) and the spray device (94). The gas cooler 1 (91) also includes a vacuum pump (14), and the vacuum pump (14) is connected to the steam generator (9). The gas cooler 1 (91) also includes a water vapor compressor (11), and the inlet of the water vapor compressor (11) is connected to the steam outlet (95) through a pipeline. The outlet of the water vapor compressor (11) is connected to the user through a pipeline. The gas cooler 2 (8) also includes a water replenishment valve (12) and a circulating water valve (13). The circulating water valve (13) is installed at the circulating water outlet. The water supply valve (12) is installed on the pipe at the port (92), and the four-way reversing valve includes four ports a, b, c, and d. The a end is connected to the gas inlet of the steam generator (9) through a pipe, the b end is connected to the heat pump compressor (1) through a pipe, the c end is connected to the gas-liquid separator (7) through a pipe, the gas-liquid separator (7) is used to separate the carbon dioxide gas and return it to the heat pump compressor (1), and the d end is connected to the heat exchange component through a pipe. When heating, the a end is connected to the b end, and the c end is connected to the d end.During defrosting, the end a is connected to the end c, and the end b is connected to the end d. The heat exchange component includes an evaporator (5) and a regenerator (3). The regenerator (3) is connected to the gas cooler 2 (8) through a pipeline. The regenerator (3) is connected to the end d of the four-way reversing valve (2) through a pipeline. The regenerator (3) is connected to the evaporator (5) through a pipeline, and is connected to the regenerator (3) through a pipeline after passing through the evaporator (5). A throttling device (4) is provided on the pipeline between the regenerator (3) and the evaporator (5). A fan (6) is provided at the evaporator (5). The monitoring component also includes a power collector (15), a pressure sensor (96), a liquid level sensor (93), a temperature sensor 1 (16), a temperature sensor 2 (17 ) and temperature sensor three (18), the power collector (15) is connected to the heat pump compressor (1), the fan (6), the water pump (10), the water vapor compressor (11) and the vacuum pump (14) respectively, the pressure sensor (96) is connected to the steam generator (9), the liquid level sensor (93) is placed at the bottom of the internal space and is used to monitor the liquid level of the stored liquid, the temperature sensor one (16) is provided on the outlet pipe of the gas cooler two (8) connected to the spray device (94), that is, installed at the outer wall of the starting position of the pipe, the temperature sensor two (17) is provided on the outlet pipe connected to the heat pump compressor (1), and the temperature sensor three (18) is provided on the outlet pipe connected to the water vapor compressor (11); The control method comprises the following steps: S1. Establishing the total system input power function W of each device, including the water pump (10), vacuum pump (14), heat pump compressor (1), water vapor compressor (11) and fan (6); S2. Start the above-mentioned equipment, set the maximum value Hws(max) and minimum value Hws(min) of the liquid level of the steam generator (9), set the outlet target steam temperature Tss and the return temperature ΔTs of the water vapor compressor (11), set the pressure Ps and the return pressure ΔP of the internal space of the steam generator (9), set the exhaust return temperature ΔTp of the heat pump compressor (1), the outlet hot water return temperature ΔTw of the gas cooler 2 (8), and the difference ΔTwp between the target exhaust temperature Tps of the heat pump compressor (1) and the outlet target water temperature Tws of the gas cooler 2 (8); S3, setting the target pressure Ps of the internal space of the steam generator (9), dividing the setting range into a plurality of controllable target pressure points Ps1, Ps2, Ps3, ..., Psi, ..., Psn (1≤i≤n), where Ps1=0.1 MPa, Psn=0.05 MPa; S4. Set the target water temperature Tws at the outlet of the second gas cooler (8) to the saturated steam temperature corresponding to Ps; S5. Calculate the target exhaust temperature Tps of the heat pump compressor (1) based on the target water temperature Tws at the outlet of the second gas cooler (8), Tps = Tws + ΔTwp; S6. Monitor the temperature at each location through temperature sensor 1 (16), temperature sensor 2 (17), and temperature sensor 3 (18), monitor the internal space pressure P of the steam generator (9) through pressure sensor (96), and monitor the power of each device through power collector (15); S7, judging whether the internal pressure P of the steam generator (9) reaches the target pressure Ps, if Ps ≥ P + ΔP, loading is performed by the vacuum pump (14), if Ps ≤ P - ΔP, unloading is performed by the vacuum pump (14), otherwise maintaining the current state; S8, judging whether the exhaust temperature Tp reaches the target exhaust temperature Tps, if Tp ≥ Tps + ΔTp, then increasing the opening of the throttling device (4), if Tp ≤ Tps - ΔTp, then reducing the opening of the throttling device (4), otherwise maintaining the current state; S9, determine whether the liquid level height Hw reaches the target liquid level maximum value Hws(max) or minimum value Hws(min), if Hw ≥ Hws(max), then reduce the opening of the water supply valve (12), if Hw ≤ Hws(min), then increase the opening of the water supply valve (12); if Hw does not reach Hws(max) or Hws(min), then determine whether the outlet water temperature Tw of the gas cooler 2 (8) reaches the target water temperature Tws, if Tw ≥ Tws+ΔTw, then increase the opening of the water supply valve (12), if Tw ≤ Tws-ΔTw, then reduce the opening of the water supply valve (12), otherwise maintain the current state; S10, judging whether the outlet steam temperature Ts of the water vapor compressor (11) reaches the target steam temperature Tss, if Ts≥Tss+ΔTs, the water vapor compressor (11) is unloaded, if Ts≤Tss-ΔTs, the water vapor compressor (11) is loaded, otherwise the current state is maintained; S11. After the standby group runs stably, calculate the total system input power W (Psi) corresponding to the current Psi; S12. Determine whether i>1 is satisfied. If not, let i=i+1 and Ps=Psi, and repeat steps S4 to S11 until i>1. If W(Psi)>W(Ps(i-1)), then determine Ps(i-1) as the optimal target pressure of the steam generator (9) so that the total input power of the system is minimized. Otherwise, let i=i+1 and Ps=Psi, and repeat steps S4 to S11 until W(Psi)>W(Ps(i-1)), then determine Ps(i-1) as the optimal target pressure of the steam generator (9) so that the total input power W of the system is minimized.

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