Anti-freezing solution self-regeneration control method of heat source tower heat pump system

Abstract

The invention discloses an anti-freezing solution self-regeneration control method for a heat source tower heat pump system, which comprises the following steps of: firstly, acquiring an air enthalpy and humidity diagram in a heating period, and dividing the air enthalpy and humidity diagram into regions according to an outdoor air state point, an isotherm line, an isohumidity line, an isoenthalpy line and a saturation line in the heating period, an area among an isotherm, an isenthalpy line and a saturation line is taken as an area I; taking an isenthalpy line, an ishumidity line and a saturation line as boundaries to divide a region II; taking an isohumidity line and a saturation line as boundaries to divide into a region III; taking an isotherm and a saturation line as boundaries to divide into a region IV; according to the hourly and day-by-day change of the building thermal load Q, building control scene conditions are judged, and building control scenes comprise the large thermal load, the medium thermal load, the small thermal load, the no thermal load and the existence of cold load; during actual operation of the heat pump, the temperature interval of the solution is flexibly controlled, and heat transfer and mass transfer of the solution are controlled, so that self-regeneration concentration of the solution is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concentration and regeneration of antifreeze solution, and particularly to the technical field of concentration and regeneration of antifreeze solution applied to heat source tower heat pump. BACKGROUND

[0002] The heat source tower heat pump system has the characteristics of higher energy efficiency than the traditional water chiller in the cooling mode, and can realize high-efficiency heating in the heating mode by using the heat absorption of the outdoor air by the refrigerant. The heat source tower heat pump system can be used as a replacement for the traditional cold and heat source system of the water chiller plus boiler, and is increasingly applied in building refrigeration and heating in hot summer and cold winter areas. However, when the heat source tower heat pump operates in the heating mode, the water vapor in the air enters the antifreeze solution during the heat and mass exchange in the heat source tower, which reduces the concentration of the antifreeze solution and increases the freezing point of the antifreeze solution, thereby increasing the risk of damage to the heat pump main equipment due to low-temperature icing. Therefore, in the actual application of the heat source tower heat pump system, the concentration of the antifreeze solution during operation needs to be closely monitored, and the antifreeze solution needs to be regenerated or high-concentration antifreeze solution needs to be added when the concentration is lower than the allowable value.

[0003] Currently, there are four main methods for regenerating antifreeze solution: (1) heat-driven separation method, such as mechanical vapor recompression regeneration, heating regeneration, etc., which removes excess water in the solution by evaporation to improve the mass fraction of the antifreeze solution; (2) electrodialysis method, which uses a direct current electric field to drive ions, and through the selective permeability of the selective ion exchange membrane, different ions are directionally migrated, the target ions enter the concentration chamber to realize concentration (increase the concentration), and the corresponding ion concentration in the dilute chamber is reduced, thereby realizing solute separation and antifreeze solution concentration; (3) membrane distillation method, which uses the temperature difference on both sides of the membrane to generate a vapor pressure difference, driving the volatile components (such as water vapor) to diffuse through the membrane pores from the high-temperature side to the low-temperature side, thereby increasing the concentration of the dilute solution; (4) freezing regeneration method, the regeneration device cools the solution to the freezing point, and before the liquid concentration reaches the eutectic point, the water is separated in the form of ice, while the solute remains in the liquid, thereby increasing the concentration of the dilute solution.

[0004] Among the above four methods, the first method requires the system to provide additional heat to meet the energy consumption required for water evaporation, and a higher regeneration temperature is required in various operating environments, which increases the burden on the energy supply system; the second method is complex, high in energy consumption and high in investment cost; the third method must pay special attention to keeping the membrane pores dry, otherwise the efficiency of the membrane distillation process will be reduced, and the membrane will be easily scaled and have a short service life; the fourth method is limited by the volume of the regeneration device, and in the freezing regeneration, the regeneration system usually needs multiple freezing cycles to improve the solution concentration and separation efficiency, which is high in investment cost.

[0005] Therefore, it is very important to develop and propose a simple, low-energy and high-efficiency solution regeneration method. SUMMARY

[0006] In view of the deficiencies of the existing anti-freezing solution regeneration method in the heat source tower heat pump system in the heating condition, the application proposes an anti-freezing solution self-regeneration control method of the heat source tower heat pump system.

[0007] The technical solution adopted by the application is as follows: An anti-freezing solution self-regeneration control method of a heat source tower heat pump system, comprising the following steps: Step 1: Obtain the air enthalpy-humidity diagram in the heating period, and divide the air enthalpy-humidity diagram according to the outdoor air state point in the heating period and the isotherm, isohumidity, isenthalpy and saturation line, wherein the region between the isotherm, isenthalpy and saturation line is region I; the region between the isohumidity and saturation line is region II; the region between the isotherm and saturation line is region III; and the region between the isohumidity and saturation line is region IV; Step 2: According to the hourly and daily changes of the building heat load Q, the building control scene is judged, and the building control scene includes large heat load, medium heat load, small heat load, no heat load and cold load. Step 3: In actual heat pump operation, the temperature range of the solution is flexibly controlled, and the heat transfer and mass transfer of the solution are controlled to realize the self-regeneration concentration of the solution.

[0008] Further, in step 2, the low load limit Q1 and the high load limit Q2 are set, and Q1 < Q2; according to the building heat load Q, Q1 and Q2, the control scene is divided into: If Q is greater than or equal to Q2, it is determined that the building heat load is large. If Q1 < Q < Q2, it is determined that the building heat load is medium. If Q is less than or equal to Q1, it is determined that the building heat load is small. If Q is equal to 0, it is determined that the building heat load is zero. If there is a cold load demand based on the building function characteristics, it is determined that the building has a cold load.

[0009] Further, the method for setting the low load limit Q1 and the high load limit Q2 is as follows: taking 50% of the rated heating capacity of the heat pump as the low load limit Q1 and 80% of the rated heating capacity of the heat pump as the high load limit Q2.

[0010] Further, based on the building control scene and the solution concentration, the corresponding anti-freezing solution self-regeneration control strategy is adopted, and the specific strategy is as follows: If the heat load is large and the solution concentration is qualified, the temperature region of the solution in the III region is controlled.

[0011] If the heat load is large and the solution concentration is low, the low temperature region of the solution in the III region is controlled.

[0012] If the heat load is large and the solution concentration is high, the extremely low temperature region of the solution in the III region is controlled.

[0013] If the heat load is medium and the solution concentration is qualified, the low temperature region of the solution in the II region or the low temperature region of the solution in the III region close to the dew point temperature is controlled.

[0014] If the heat load is medium and the solution concentration is low, the low temperature region of the solution in the II region is controlled.

[0015] If the heat load is medium and the solution concentration is high, the low temperature region of the solution in the III region is controlled.

[0016] If the heat load is small and the solution concentration is qualified, the temperature region of the solution in the II region is controlled.

[0017] If the heat load is small and the solution concentration is low, the high temperature region of the solution in the II region is controlled.

[0018] If the heat load is small and the solution concentration is high, the low temperature region of the solution in the III region is controlled.

[0019] If there is no heat load and the solution concentration is qualified, the temperature region of the solution in the II region is controlled.

[0020] If there is no heat load and the solution concentration is low, the high temperature region of the solution in the II region is controlled.

[0021] If there is no heat load and the solution concentration is high, the low temperature region of the solution in the II region is controlled.

[0022] If there is a cold load and the solution concentration is qualified, the temperature region of the solution in the IV region is controlled.

[0023] If there is a cold load and the solution concentration is low, the high temperature region of the solution in the IV region is controlled.

[0024] If there is a cold load and the solution concentration is high, the low temperature region of the solution in the IV region is controlled.

[0025] Further, in the air enthalpy humidity chart, O point is assumed to be the outdoor air state point of a certain place in the heating period, the temperatures of A, B and C points are air dry bulb temperature point, wet bulb temperature point and dew point temperature point on the saturation line respectively, A, B and C divide the saturation line into four sections; based on the connecting lines (isotherm, isenthalp, isohumidity and saturation line) between O point and A, B and C, the enthalpy humidity chart is divided into four regions I, II, III and IV.

[0026] Further, the II region is divided into regions according to temperature, and the division basis is: The II region is divided into a low temperature region and a high temperature region according to the midpoint between the wet bulb temperature and the dew point temperature as a demarcation point, above the midpoint, the high temperature region is below the wet bulb temperature, and below the midpoint, the high temperature region is above the dew point temperature; Further, the III region is divided into regions according to temperature, and the division basis is: the III region is divided into an extremely low temperature region and a low temperature region according to a demarcation point of 5 degrees below the dew point temperature, the extremely low temperature region is 5 degrees below the dew point temperature, and the low temperature region is below the dew point temperature and above 5 degrees below the dew point temperature; Further, the IV region is divided into regions according to temperature, and the division basis is: the IV region is divided into a low temperature region and a high temperature region according to a demarcation point of 5 degrees above the dry bulb temperature, the high temperature region is 5 degrees above the dry bulb temperature, and the low temperature region is above the dry bulb temperature and below 5 degrees above the dry bulb temperature.

[0027] Further, based on the meteorological data of the location of the building, the indoor air calculation parameters, the outdoor air calculation parameters, the thermal properties of the building envelope, the operation time of the lighting equipment of the room, the work and rest time of the personnel, and the ventilation frequency parameters, the building load characteristics Q are calculated.

[0028] Further, the building model is established by using the DeST software, the building model is pretreated, the thermal design parameters and the building envelope materials of the building are set, the building load is simulated and calculated, and the hourly heat load of the building in the heating period is output.

[0029] The beneficial effects of the present application are: The anti-freezing solution self-regeneration method provided by the present application is suitable for the use of the heat source tower heat pump in the heating period, based on the building side load change, by regulating the solution temperature, reasonably utilizing the sensible heat and latent heat in the environment air, the concentration regeneration of the anti-freezing solution in the heat source tower can be realized. Compared with the existing anti-freezing solution self-regeneration method, no additional heat source is input, the system is simple, easy to use, environmentally friendly and efficient, the equipment investment is greatly reduced, the problem that the heat source tower heat pump is damaged due to the low temperature icing of the anti-freezing solution is solved, and the problem that the heat pump main equipment is damaged due to the low temperature icing of the anti-freezing solution is solved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is an enthalpy-humidity graph of moist air.

[0031] Figure 2 The diagram shows the heat pump system of the heat source tower. (a) is a schematic diagram of data acquisition for the heating operation of the heat pump system of the heat source tower; (b) is the operating principle of the heating system of the heat pump system of the heat source tower.

[0032] Figure 3 This is a control strategy when the heat load is moderate during the heating season.

[0033] Figure 4 Control strategies during periods of high heat load in the heating season.

[0034] Figure 5 Control strategies when the heat load is low during the heating season.

[0035] Figure 6 Control strategies when there is a demand for cooling load during the heating season.

[0036] Figure 7 The outdoor meteorological parameters for Nanjing City are as follows: (a) hourly dry-bulb temperature, (b) humidity, and (c) dry-bulb temperature.

[0037] Figure 8 In the diagram, (a) is a floor plan of the first floor of a residential building in Nanjing, and (b) is a general model drawing.

[0038] Figure 9 Hourly heat load of a residential building in Nanjing.

[0039] Figure 10 In the image, (a) is a floor plan of an office building in Nanjing, and (b) is a model drawing.

[0040] Figure 11 Hourly heat load of an office building in Nanjing. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0042] Combined with appendix Figures 1 to 8 The present invention proposes a method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower, comprising the following steps: Step 1: Obtain the air enthalpy-humidity chart for the heating season ( Figure 1As shown in the figure, according to the outdoor air state point during the heating period and the isotherm, isohydric line, isenthalpic line and saturation line, the air enthalpy humidity chart is divided into regions, wherein the region between the isotherm, isenthalpic line and saturation line is region I; the isenthalpic line, isohydric line and saturation line are boundaries to divide region II; the isohydric line and saturation line are boundaries to divide region III; and the isotherm and saturation line are boundaries to divide region IV.

[0043] Suppose that the heat and mass transfer of the solution in contact with the air is ideal (water is infinite and contact time is infinite). The heat and mass exchange (or the heat and water vapor transfer direction) between the solution and the air can be described as follows: When the solution temperature is in region I, the enthalpy of the solution is greater than that of the air, the boundary layer gas humidity is greater than that of the air, and the temperature is lower than the dry bulb temperature of the air. The sensible heat transfer is from the air to the solution, the latent heat transfer is from the solution to the air (i.e. water evaporation in the solution, solution concentration), and the total heat transfer is from the solution to the air (i.e. solution temperature reduction).

[0044] When the solution temperature is in region II, the enthalpy of the solution is less than that of the air, the boundary layer gas humidity is greater than that of the air, and the temperature is lower than the dry bulb temperature of the air and greater than the dew point temperature of the air. The sensible heat transfer is from the air to the solution, the latent heat transfer is from the solution to the air (i.e. water evaporation in the solution, solution concentration), and the total heat transfer is from the air to the solution (i.e. solution temperature increase).

[0045] When the solution temperature is in region III, the enthalpy of the solution is less than that of the air, the boundary layer gas humidity is less than that of the air, and the temperature is lower than the dry bulb temperature of the air and the dew point temperature of the air. The sensible heat transfer is from the air to the solution, the latent heat transfer is from the air to the solution (i.e. water vapor condensation in the air, solution dilution), and the total heat transfer is from the air to the solution (i.e. solution temperature increase).

[0046] When the solution temperature is in region IV, the enthalpy of the solution is greater than that of the air, the boundary layer gas humidity is greater than that of the air, and the temperature is higher than the dry bulb temperature of the air. The sensible heat transfer is from the solution to the air, the latent heat transfer is from the solution to the air (i.e. water evaporation in the solution, solution concentration), and the total heat transfer is from the solution to the air (i.e. solution temperature reduction).

[0047] From the above analysis, it can be seen that when the solution temperature is in the II region, the evaporation of the solution will produce a concentration effect, and the total energy is also from the air to the solution. When the solution temperature is in the III region, the evaporation of the solution will produce a dilution effect, and the total energy is also from the air to the solution. When the solution temperature is in the III region, the energy absorbed by the solution from the air will be higher than that in the II region, so it is always desirable to have the solution in the III region to absorb the latent heat of water vapor in the air and improve the energy efficiency of the heat pump for winter heating, but the adverse consequence is that the solution becomes dilute and the freezing point decreases, and the solution needs to be concentrated. When the solution temperature is in the II region, the total energy is also from the air to the solution, but the energy absorbed is limited, which is not conducive to improving the energy efficiency of the heat pump and achieving a large heating capacity, but it is beneficial that the solution concentration will increase and will not be diluted.

[0048] Step 2, for the heating load of the building, it changes hour by hour, and it also changes day by day throughout the heating season. In the design of the heat pump, the heat pump is usually selected according to the maximum heat load, and the heat pump does not need to operate at the maximum load operating point in actual operation. In other words, when the heat load is high, it is expected to absorb as much heat from the air as possible; when the heat load is low, it is not necessary to absorb too much heat from the air.

[0049] Therefore, in this embodiment, the building load characteristic Q is calculated according to the type of the building, and the building control scene is judged, including high heat load, medium heat load, low heat load, no heat load, and cold load.

[0050] Based on the meteorological data of the location of the building, the calculation parameters of indoor air, the calculation parameters of outdoor air, the thermal properties of the building envelope, the operation time of the lighting equipment of the room, the working and resting time of the personnel, and the ventilation frequency parameter, the building load characteristic Q is calculated by referring to the calculation method disclosed in "Heating Ventilation and Air Conditioning", or a building model is established by using DeST software, the building model is pretreated, the thermal design parameters of the building and the building envelope materials are set, the building load is simulated and calculated, and the hourly heat load of the building in the heating period is output.

[0051] In the design of the heat pump, the heat pump is usually selected according to the maximum heat load, the heat pump model is determined, the rated heating capacity of the heat pump is Q0, a plurality of load threshold values are set, the control scene is divided according to the relationship between the building load characteristic Q and the plurality of load threshold values, and the specific conditions are as follows (for example, the value Q1 of 50% of Q0 is taken as the low load limit, and the value Q2 of 80% of Q0 is taken as the high load limit): If Q is greater than Q2, it is determined that the building heat load is high; If Q is greater than Q1 and less than Q2, it is determined that the building heat load is medium; If Q is less than Q1, it is determined that the building heat load is low; If Q is equal to zero, it is determined that the building heat load is zero; If there is a cooling load demand based on the building function characteristics (such as data center), it is determined that the building has a cooling load.

[0052] Step 3, according to the hourly and daily changes of the building heat load, the temperature range of the solution is controlled to realize the control of heat transfer and mass transfer. Combined with the above-mentioned control of the temperature range of the solution, the temperature range of the solution is controlled according to the building heat load, so that the heat pump is controlled to realize the control of heat transfer and mass transfer. Figure 1 As shown in the actual heat pump operation, the temperature of the solution is flexibly controlled according to the building side heat load, so that the self-regeneration concentration of the solution is realized.

[0053] In this embodiment, based on the building control scene and the solution concentration, the corresponding antifreeze self-regeneration control strategy is adopted; specifically as follows: When the heat source tower heat pump is used for heating in the heating period, the solution temperature is always lower than the air wet bulb temperature, so as to ensure that the total energy transfer direction is from the air to the antifreeze, and the antifreeze absorbs the air to realize the heat source tower heat pump heating (in region II and region III). In region II, when the solution temperature is relatively high and close to the air wet bulb temperature, the solution is concentrated more, the heat absorption is less, the evaporation temperature of the heat pump is required to be higher, and the heat pump heating COP is lower. When the solution temperature is relatively low and close to the air dew point temperature, the solution is not concentrated so much, the heat absorption is more, the evaporation temperature of the heat pump is not required to be so high, and the heat pump heating COP is increased. In region III, when the solution temperature is very low, the solution is diluted more, the heat absorption is more, and the evaporation temperature of the heat pump is required to be lower, and the heat pump heating COP is lower. If it is close to the dew point temperature, the dilution will not be so much, the heat absorption will be less, the evaporation temperature of the heat pump will not be too low, and the heat pump heating COP will not be too low. Therefore, by considering the building heat load, the solution concentration, and the heat pump COP, the control logic or strategy shown in Table 1 can be formed to control the operation of the heat source tower heat pump, so as to realize the effective self-regeneration of the antifreeze.

[0054]

[0055] In the above embodiment, the three regions II, III and IV are divided according to the temperature, and the division basis is as follows: Region II divides the temperature into a low temperature region and a high temperature region according to the midpoint of the wet bulb temperature and the dew point temperature as the dividing point. Above the midpoint, the high temperature region is below the wet bulb temperature. Below the midpoint, the high temperature region is above the dew point temperature. Region III divides the temperature into an extremely low temperature region and a low temperature region according to the dew point temperature as the dividing point. Below the dew point temperature by 5 degrees is the extremely low temperature region. Below the dew point temperature, above the dew point temperature by 5 degrees is the low temperature region. Region IV divides the temperature into a low temperature region and a high temperature region according to the dry bulb temperature as the dividing point. Above the dry bulb temperature by 5 degrees is the high temperature region. Above the dry bulb temperature, below the dry bulb temperature by 5 degrees is the low temperature region.

[0056] Taking the scenario of using heat source tower heat pump in buildings in hot summer and cold winter regions as an example, the specific description of the control logic or strategy in Table 1 is as follows: (1) Based on the cold weather in the heating period of hot summer and cold winter regions, the required heat load of the building side is large, and only using air sensible heat cannot meet the demand, and it is necessary to absorb the heat released by water vapor condensation in the air. At this time, the solution temperature is controlled to be lower than the air dew point (i.e. region III), and the air sensible heat and latent heat are used to meet the building load demand. The solution temperature in the heat source tower is monitored in real time. If the solution concentration is qualified, the solution temperature in region III can be controlled to absorb as much air energy as possible to meet the building heat load demand and take into account the COP; if the solution concentration is low, the solution temperature in the low temperature region of region III can be controlled to absorb air energy to meet the building heat load demand, reduce the solution moisture absorption amount, prevent freezing due to too low concentration, or add concentrated solution, and take into account the COP; if the solution concentration is high, the solution temperature in the very low temperature region of region III can be controlled to absorb as much air energy as possible to meet the building heat load demand and take into account the COP.

[0057] (2) In the relatively warm weather in the heating period of hot summer and cold winter regions, the building heat load is small, and the solution temperature is controlled to be between the air dew point and the wet bulb temperature (i.e. region II). The air sensible heat is transferred to the solution, and the water vapor in the solution evaporates to realize concentration and regeneration and increase the concentration; although the water in the solution evaporates in this process, the total energy is still transferred from the air to the solution, and the building heat load demand is met. The solution temperature in the heat source tower is monitored in real time. If the solution concentration is qualified, the solution temperature in region II can be controlled to absorb as much air energy as possible to meet the building heat load demand and take into account the COP; if the solution concentration is low, the solution temperature in the high temperature region of region II can be controlled to absorb air energy to meet the building load demand, increase the water evaporation amount in the solution, prevent freezing due to too low concentration, or add concentrated solution, and take into account the COP; if the solution concentration is high, the solution temperature in the low temperature region of region II can be controlled to absorb air energy to meet the building load demand and take into account the COP.

[0058] (3) In the heating period of hot summer and cold winter regions, when there is no heat load in the building period, the heat source tower heat pump system is controlled to operate in heating mode, and the solution temperature is adjusted to be higher than the air dew point and lower than the wet bulb temperature (i.e. region II). At this time, the water vapor in the solution evaporates to store heat in the heat storage device. The solution temperature in the heat source tower is monitored in real time. If the solution concentration is qualified, the solution temperature in region II can be controlled to absorb air energy and store the absorbed heat in the heat storage device, and take into account the COP; if the solution concentration is low, the solution temperature in the high temperature region of region II can be controlled to absorb air energy and store the absorbed heat in the heat storage device, and increase the water evaporation amount in the solution to prevent freezing due to too low concentration, or add concentrated solution, and take into account the COP; if the solution concentration is high, the solution temperature in the low temperature region of region II can be controlled to absorb air energy and store the absorbed heat in the heat storage device, and take into account the COP.

[0059] (4) In the heating period of hot summer and cold winter region, when the building has no heat load but has cold load, the heat source tower heat pump system is controlled to operate in refrigeration mode. At this time, the heat source tower has the function of cooling tower, and the solution temperature is regulated to be much higher than the dry bulb temperature of air (i.e. region IV), and refrigeration is realized by evaporation of water in the solution to release heat to the atmosphere, and the solution concentration increases. The solution temperature in the heat source tower is monitored in real time. If the solution concentration is qualified, the solution temperature in region IV can be controlled to release energy to meet the building cold load demand, and the COP is considered; if the solution concentration is low, the solution temperature in the high temperature region of region IV can be controlled to release energy to meet the building cold load demand, increase the water evaporation amount in the solution, prevent freezing due to too low concentration, or add concentrated solution, and the COP is considered; if the solution concentration is high, the solution temperature in the low temperature region of region IV can be controlled to release energy to meet the building cold load demand, and the COP is considered.

[0060] In combination with Figures 7 to 9 , a residential building and an office building in Nanjing are taken as examples to illustrate the implementation method of the present application. The climate in Nanjing is a typical hot summer and cold winter climate, which is also a typical city suitable for using heat source tower heat pump for cooling and heating.

[0061] Example 1:

[0062] A residential building in Nanjing has a building area of 3457.44m 2 , which needs to be heated all day during the heating period. The hourly meteorological parameters of Nanjing during the heating period are shown in Figure 7 , and the heating period is from December 8 to February 18, a total of 73 days. Based on the hourly meteorological parameters and building data parameters of Nanjing, the hourly heat load of the building during the heating period is calculated as shown in Figure 9 . It can be seen from Figure 9 that the maximum heat load during the heating period is 180.3kW, and the heat source tower heat pump system is selected based on the maximum heat load as the design heat load.

[0063] The heat load below 80kW is set as the low load period, which accounts for about 50% of the entire heating period; 80-110kW is set as the medium load period, which accounts for about 30% of the entire heating period; and 110-180kW is set as the high load period, which accounts for about 20% of the entire heating period.

[0064] When the building is in the high load period, the heat source tower heat pump is operated to generate heat, and the solution only uses the sensible heat of air, which cannot meet the heat load demand of the building, and needs to consider absorbing the heat released by the condensation of water vapor in the air. At this time, the solution temperature is controlled to be lower than the dew point temperature of air, and both the sensible heat and latent heat of air are utilized to utilize as much energy in the air as possible to meet the heat load demand of the building, i.e. the solution temperature is controlled to be Figure 1zone III. Meanwhile, the solution concentration is monitored. If the solution concentration is qualified, the solution temperature can be controlled in the temperature zone of zone III to absorb as much air energy as possible to meet the building heat load demand and to take into account the COP. If the solution concentration is low, the solution temperature can be controlled in the low temperature zone of zone III to absorb air energy to meet the building heat load demand, to reduce the solution moisture absorption amount, to prevent freezing due to too low concentration, or to add concentrated solution to take into account the COP. If the solution concentration is high, the solution temperature can be controlled in the very low temperature zone of zone III to absorb as much air energy as possible to meet the building heat load demand and to take into account the COP.

[0065] When the building is in the medium load period, the heat source tower heat pump is operated to generate heat. Meanwhile, the solution concentration is monitored. If the solution concentration is qualified, the solution temperature can be controlled in the low temperature zone of zone II or in the low temperature zone of zone III to absorb air energy to meet the building load demand and to take into account the COP. The solution temperature can be controlled in the low temperature zone of zone II to absorb air energy to meet the building load demand, to increase the water evaporation amount in the solution, and to prevent freezing due to too low concentration. Concentrated solution can be added. If the solution concentration is high, the solution temperature can be controlled in the low temperature zone of zone III to absorb air energy to meet the building load demand and to take into account the COP. Figure 1 When the building is in the low load period, the heat source tower heat pump is operated to generate heat. Not only can the solution temperature be controlled to be lower than the air wet-bulb temperature to transfer sensible heat in the air to the solution, but also the solution temperature can be controlled to be higher than the air dew-point temperature to evaporate water vapor in the solution to increase the solution concentration to achieve solution concentration and regeneration. Although water vapor evaporation absorbs heat, the enthalpy of the solution is lower than the enthalpy of the air, and the total energy is still transferred from the air to the solution to meet the building heat load demand, i.e., the solution temperature is in zone II. Meanwhile, the solution concentration is monitored. If the solution concentration is qualified, the solution temperature can be controlled in the temperature zone of zone II to absorb as much air energy as possible to meet the building heat load demand and to take into account the COP. If the solution concentration is low, the solution temperature can be controlled in the high temperature zone of zone II to absorb air energy to meet the building load demand, to increase the water evaporation amount in the solution, and to prevent freezing due to too low concentration. Concentrated solution can be added to take into account the COP. If the solution concentration is high, the solution temperature can be controlled in the low temperature zone of zone II to absorb air energy to meet the building load demand and to take into account the COP.

[0066] The low load period accounts for about 50% of the entire heating period, the medium load period accounts for about 30% of the entire heating period, and the high load period accounts for about 20% of the entire heating period. From the long-term interests of an entire heating period, not only is the building heating demand met, but also solution concentration and regeneration are achieved.

[0067]

[0068] Example 2:

[0069] In combination with Figures 10 to 11 ​, a certain office building in Nanjing, with a building area of 4194.4m 2 The building needs to be heated during the time period of 6:00~22:00 during the heating period, and there is no heat load demand at night from 22:00 to 6:00, so there is no need to run the heat source tower heat pump for heating. The meteorological parameters in Nanjing during the heating period are as shown in Figure 7 The heating period is from December 8th to February 18th, a total of 73 days. Based on the hourly meteorological parameters and building data parameters in Nanjing, the hourly heat load of the building during the heating period is calculated as shown in Figure 11 The maximum heat load during the heating period is 274.44kW, and the heat source tower heat pump system is selected based on the maximum heat load as the design heat load.

[0070] 0kW is set as the no-load period, which accounts for about 30% of the entire heating period; greater than 0kW and less than 100kW is the low-load period, which accounts for about 40% of the entire heating period; 100~150kW is set as the medium-load period, which accounts for about 20% of the entire heating period; and 150~274.44kW is the high-load period, which accounts for about 10% of the entire heating period.

[0071] When the building is in the no-load period, there is no need to run the heat source tower heat pump for heating, but the heat source tower heat pump system can be controlled to run in heating mode, control the solution temperature to be greater than the air dew point temperature and less than the air wet bulb temperature, and the heat generated can be stored in the heat storage device. The water vapor in the solution evaporates, and the solution is regenerated by concentration. At the same time, the solution temperature is monitored. If the solution concentration is qualified, the solution can be controlled in the temperature region of region II to absorb air energy and store the absorbed heat in the heat storage device, taking into account the COP; if the solution concentration is low, the solution can be controlled in the high temperature region of region II to absorb air energy and store the absorbed heat in the heat storage device, increase the water evaporation amount in the solution, prevent the concentration from being too low and freezing, or add concentrated solution, and take into account the COP; if the solution concentration is high, the solution can be controlled in the low temperature region of region II to absorb air energy and store the absorbed heat in the heat storage device, taking into account the COP.

[0072] When the building is in the high load period, the heat source tower heat pump is operated to produce heat. The solution only uses the sensible heat of the air and cannot meet the demand of the building heat load. The heat released by the condensation of water vapor in the air needs to be considered. At this time, the solution temperature is controlled to be lower than the air dew point temperature. The sensible heat and latent heat in the air are both utilized. As much as possible, the energy in the air is utilized to meet the demand of the building heat load, that is, the solution temperature is in the III region. At the same time, the solution concentration is monitored. If the solution concentration is qualified, the solution temperature in the III region is controlled. As much as possible, the energy in the air is absorbed to meet the demand of the building heat load, and the COP is considered. If the solution concentration is low, the solution temperature in the low temperature region of the III region is controlled. The energy in the air is absorbed to meet the demand of the building heat load, the moisture absorption amount of the solution is reduced, the concentration is prevented from being too low to freeze, or the concentrated solution is added, and the COP is considered. If the solution concentration is high, the solution temperature in the very low temperature region of the III region is controlled. As much as possible, the energy in the air is absorbed to meet the demand of the building heat load, and the COP is considered.

[0073] When the building is in the medium load period, the heat source tower heat pump is operated to produce heat. At the same time, the solution concentration is monitored. If the solution concentration is qualified, the solution temperature in the low temperature region of the II region or in the low temperature region of the III region close to the dew point temperature is controlled. The energy in the air is absorbed to meet the demand of the building load, and the COP is considered. The solution temperature in the low temperature region of the II region is controlled. The energy in the air is absorbed to meet the demand of the building load, the evaporation amount of the water in the solution is increased, the concentration is prevented from being too low to freeze, or the concentrated solution is added. If the solution concentration is high, the solution temperature in the low temperature region of the III region is controlled. The energy in the air is absorbed to meet the demand of the building load, and the COP is considered.

[0074] When the building is in the low load period, the heat source tower heat pump is operated to produce heat. Not only can the solution temperature be controlled to be lower than the air wet bulb temperature, and the sensible heat in the air is transferred to the solution, but also the solution temperature can be controlled to be greater than the air dew point temperature. The water vapor in the solution evaporates, the solution concentration is increased, the solution is regenerated, although the water vapor evaporation absorbs heat, but the enthalpy value of the solution is lower than the enthalpy value of the air, the total energy is still transferred from the air to the solution, and the demand of the building heat load is met, that is, the solution temperature is in the II region. At the same time, the solution concentration is detected. If the solution concentration is qualified, the solution temperature in the temperature region of the II region is controlled. As much as possible, the energy in the air is absorbed to meet the demand of the building heat load, and the COP is considered. If the solution concentration is low, the solution temperature in the high temperature region of the II region is controlled. The energy in the air is absorbed to meet the demand of the building load, the evaporation amount of the water in the solution is increased, the concentration is prevented from being too low to freeze, or the concentrated solution is added, and the COP is considered. If the solution concentration is high, the solution temperature in the low temperature region of the II region is controlled. The energy in the air is absorbed to meet the demand of the building load, and the COP is considered.

[0075] The no-load period accounts for about 30% of the whole heating period, the low-load period accounts for about 40% of the whole heating period, the medium-load period accounts for about 20% of the whole heating period, and the high-load period accounts for about 10% of the whole heating period. Moreover, the no-load period is at night, and the operation of the heat source tower heat pump system is at the valley price stage at night, so the energy consumption is low. In the long-term interests of the whole heating period, not only the heating demand of the building is met, but also the concentration and regeneration of the solution are realized.

[0076] The above examples are only used to illustrate the design idea and characteristics of the present application, and its purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and the protection scope of the present application is not limited to the above examples. Therefore, any equivalent changes or modifications made according to the principles and design ideas disclosed by the present application are within the protection scope of the present application.

Claims

1. A method for controlling the self-regeneration of antifreeze in a heat pump system with a heat source tower, characterized in that, Includes the following steps: Step 1: Obtain the air enthalpy-humidity map for the heating season. Based on the outdoor air state points during the heating season, as well as isotherms, isohumidities, isenthalpicities, and saturation lines, divide the air enthalpy-humidity map into regions. Region I is defined as the area between the isotherms, isenthalpicities, and saturation lines; Region II is defined as the area bounded by the isenthalpicities, isohumidities, and saturation lines; Region III is defined as the area bounded by the isohumidities and saturation lines; and Region IV is defined as the area bounded by the isotherms and saturation lines. Step 2: Based on the hourly and daily changes of the building heat load Q, determine the building control scenario. The building control scenarios include high heat load, medium heat load, low heat load, no heat load, and with cooling load. Step 3: During actual heat pump operation, flexibly control the temperature range of the solution to control the heat transfer and mass transfer of the solution, so as to achieve self-regeneration and concentration of the solution.

2. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, In step 2, a low load limit Q1 and a high load limit Q2 are set. <Q2; Based on the building heat loads Q, Q1, and Q2, the control scenarios are divided into: If Q ≥ Q2, the building's heat load is considered large. If Q1 < Q < Q2, then the building heat load is considered to be within the range; If Q≤Q1, the building's heat load is considered small; If Q=0, it is assumed that there is no building heat load; If a building has a cooling load requirement based on its functional characteristics, then the building is considered to have a cooling load.

3. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 2, characterized in that, The method for setting the low load limit Q1 and the high load limit Q2 is as follows: if the rated heating capacity of the heat pump is Q0, take 50% of Q0 as the low load limit Q1 and 80% of Q0 as the high load limit Q2.

4. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, Based on the building control scenario and solution concentration, a corresponding antifreeze self-regeneration control strategy is adopted; the details are as follows: If the heat load is high and the solution concentration is qualified, control the temperature range of the solution in Zone III. If the heat load is high and the solution concentration is low, control the solution in the low-temperature region of zone III; If the heat load is large and the solution concentration is high, control the solution in the extremely low temperature region of Zone III. If the heat load is within acceptable limits and the solution concentration is within acceptable limits, control the solution to be in the low-temperature region of Zone II or the low-temperature region of Zone III, close to the dew point temperature. If the heat load is high and the solution concentration is low, control the solution in the low-temperature region of Zone II. If the heat load is high and the solution concentration is high, control the solution in the low-temperature region of zone III; If the heat load is small and the solution concentration is qualified, control the temperature range of the solution in Zone II. If the heat load is small and the solution concentration is low, control the solution in the high-temperature region of zone II; If the heat load is small and the solution concentration is high, the solution should be prepared in the low-temperature region of zone III. If there is no heat load and the solution concentration is qualified, control the temperature range of the solution in Zone II. If there is no heat load and the solution concentration is low, control the solution in the high-temperature region of Zone II; If there is no heat load and the solution concentration is high, control the solution in the low temperature region of zone II; If there is a cooling load and the solution concentration is qualified, control the temperature range of the solution in zone IV. If there is a cooling load and the solution concentration is low, control the solution in the high-temperature region of zone IV; If there is a cooling load and the solution concentration is high, control the solution in the low temperature region of zone IV.

5. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, In the enthalpy-humidity diagram, point O is assumed to be the outdoor air state point during the heating season in a certain area. The temperatures of points A, B, and C are the dry-bulb temperature, wet-bulb temperature, and dew point temperature of the air located on the saturation line, respectively. A, B, and C divide the saturation line into four segments. Based on the lines connecting point O with A, B, and C, the enthalpy-humidity diagram is divided into four regions: I, II, III, and IV.

6. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, Region II is divided into zones based on temperature. The division is based on the midpoint between wet-bulb temperature and dew point temperature. The temperature is divided into low-temperature zones and high-temperature zones. The area above the midpoint and below the wet-bulb temperature is the high-temperature zone, and the area below the midpoint and above the dew point temperature is the high-temperature zone.

7. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, The III region is divided according to temperature. The division is based on the following criteria: the temperature in the III region is divided into extremely low temperature region and low temperature region, with 5 degrees below the dew point temperature as the dividing point. The extremely low temperature region is 5 degrees below the dew point temperature, and the low temperature region is below the dew point temperature but above 5 degrees below the dew point temperature.

8. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, Region IV is divided into zones based on temperature. The division is based on the following criteria: Region IV is divided into low-temperature zones and high-temperature zones based on the dividing point of 5 degrees above the dry-bulb temperature. Zones 5 degrees above the dry-bulb temperature are considered high-temperature zones, while zones above the dry-bulb temperature but below 5 degrees above the dry-bulb temperature are considered low-temperature zones.

9. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, Based on meteorological data of the building location, indoor air calculation parameters, outdoor air calculation parameters, thermal properties of the building envelope, operating time of room lighting equipment, working and rest time of personnel, and ventilation frequency parameters, the building load characteristic Q is calculated.

10. The method for controlling the self-regeneration of antifreeze in a heat pump system of a heat source tower according to claim 1, characterized in that, The DeST software is used to build a building model, which is then preprocessed to set the building's thermal design parameters and building envelope materials. The building load is then simulated and calculated, and the hourly heat load of the building during the heating season is output.

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