CN106895601A - A kind of steam compression-enhanced refrigeration system occurrence temperature establishing method - Google Patents

Abstract

The invention discloses a method for setting the generation temperature of a vapor pressurization injection refrigeration system. This method is based on the calculation of the design refrigeration coefficient of the vapor booster injection refrigeration system, so as to make the system design COP optimal. In the cooling sub-process, the temperature and mass of the cooled high-temperature and high-pressure steam in the liquid storage tank increase with the increase of the set temperature, which leads to an increase in the wasted heat energy of the steam booster injection refrigeration system, thus making the system design COP With the rise of the setting temperature, it first increases and then decreases, and there is a maximum value. The set occurrence temperature corresponding to the maximum system design COP is defined as the optimum set occurrence temperature. When the optimum setting temperature is within the temperature range allowed by the heat source, the temperature should be set at the optimum setting temperature; when the optimum setting temperature is lower than the temperature allowed by the heat source, the temperature should be set at the temperature allowed by the heat source The lowest temperature; when the optimal setting temperature is higher than the temperature allowed by the heat source, the temperature should be set at the maximum temperature allowed by the heat source.

Description

A method for setting the generation temperature of a steam pressurized injection refrigeration system

technical field

The invention belongs to the technical field of refrigeration, and in particular relates to the setting of the generation temperature during the design of a steam pressurization injection refrigeration system.

Background technique

Cooling energy consumption accounts for about 15% of the total global energy consumption. Reducing cooling energy consumption can effectively alleviate the increasingly severe energy and environmental problems.

The traditional jet refrigeration system (Fig. 1) consists of generator 1, evaporator 2, condenser 3, ejector 4, liquid pump 5, throttle valve 6 and so on. The ejector is the core component of the ejector refrigeration system and is used to replace the compressor in the traditional mechanical compression refrigeration system. In the ejector, the high-temperature and high-pressure working fluid from the generator pressurizes the low-temperature and low-pressure injection fluid from the evaporator to obtain a medium-temperature, medium-pressure mixed fluid for producing cooling capacity. The high temperature and high pressure working fluid is generated by inputting thermal energy into the generator. Therefore, the thermal energy input of the generator in the ejection refrigeration system replaces the electrical energy input of the compressor in the traditional mechanical compression refrigeration system, reducing power consumption by more than 75%.

Compared with the traditional injection refrigeration system, the vapor booster injection refrigeration system is a new type of injection refrigeration system, which can further reduce power consumption. The steam pressurized injection refrigeration system shown in Figure 2 is composed of ejector 13, evaporator 14, throttling element 15, condenser 16, liquid storage tank 17, cooling water jacket 18 and generator 19, and some pipes, valves constituted. Among them, the evaporator 14, the liquid storage tank 17 and the corresponding connecting pipelines and switching valves form a multifunctional generator subsystem, which is used to receive the condensate from the condenser and provide high-temperature and high-pressure steam. The ejector 13, the condenser 16, the throttling element 15, the evaporator 14 and the corresponding connecting pipelines form a refrigeration subsystem, which is driven by the high-temperature and high-pressure steam provided by the multifunctional generator subsystem to generate cooling capacity. Compared with the traditional injection refrigeration system, the vapor booster injection refrigeration system removes the liquid pump 5 . The liquid pump 5 is used in conventional ejector refrigeration systems to compress the condensate from the condenser and deliver it to the generator. The steam pressurized injection refrigeration system uses the high-temperature and high-pressure steam generated by the generator to pressurize the liquid refrigerant stored in the liquid storage tank through heat balance, and is transported back to the generator under the push of high-temperature and high-pressure steam and by gravity. The liquid pump 5 is the only power consumption and moving part in the traditional injection refrigeration system. The vapor booster injection refrigeration system that removes the liquid pump 5 can therefore be completely driven by thermal energy without consuming electric energy, and can reduce maintenance frequency and prolong service life .

The working principle of the steam booster injection refrigeration system is as follows: a working cycle of the steam booster injection refrigeration system is divided into a cooling stage and a pressurization stage, which are regulated by switching valves, as shown in Table 1. All switching valves are closed until the system is started. In the refrigeration stage, switch valve 7, switch valve 8 and switch valve 12 are opened. The thermal energy is input into the generator 19, and high-temperature and high-pressure steam is generated in the generator 19. The high-temperature and high-pressure steam enters the injector 13 through the switching valve 7 as the working fluid, guides the low-temperature and low-pressure fluid from the evaporator 14 into the injector 13, and obtains a medium-temperature and medium-pressure mixed fluid at the outlet of the injector 13. The mixed fluid enters the condenser 16 for exothermic condensation to obtain liquid refrigerant. A part of the liquid refrigerant evaporates in the evaporator 14 to generate cooling energy after being throttled and depressurized by the throttling element 15 , and the other part of the liquid refrigerant is temporarily stored in the liquid storage tank 17 . The condenser 16 should be arranged slightly vertically higher than the liquid storage tank 17 (such as 0.63m); with the help of gravity, the condensate in the condenser 16 can enter the liquid storage tank 17 smoothly. After the volume ratio of the gaseous refrigerant and the liquid refrigerant in the liquid storage tank 17 reaches the optimal initial boost ratio, the cooling stage is ended by closing the switching valve 7 and the switching valve 8 . The pressurization stage contains three sub-processes, namely pressurization, liquid return and cooling. Open the switching valve 10 to start the sub-process of pressurization. The high-temperature and high-pressure steam enters the liquid storage tank 17 from the generator 19, and the temperature and pressure of the refrigerant in the liquid storage tank 17 are increased until the temperature and pressure of the liquid storage tank 17 are the same as those of the generator 19. Open the switching valve 11 to start the sub-process of returning liquid. Driven by the high-temperature and high-pressure steam from the generator 19, the high-temperature and high-pressure liquid in the liquid storage tank 17 enters the generator 19 until there is no liquid left in the liquid storage tank 17. The liquid storage tank 17 can be arranged to be slightly vertically higher than the generator 19 (such as 0.52m); with the help of gravity, the high-temperature and high-pressure liquid in the liquid storage tank 17 can enter the generator 19 more smoothly. Close the switch valves 10, 11 and 12, and open the switch valve 9 to start the cooling sub-process. Cooling water flows through the cooling water jacket 18, taking away the heat energy of the liquid storage tank 17, reducing the pressure and temperature of the liquid storage tank 17; until the pressure/temperature of the liquid storage tank 17 drops to meet the entry requirements of the condensate of the condenser 16, that is The pressure/temperature of the liquid storage tank 17 is slightly lower than or equal to the pressure/temperature of the condenser 16 . Close the switching valve 9, and one working cycle of the steam booster injection refrigeration system is completed.

Table 1. Regulation of the switching valve in a working cycle of the vapor booster injection refrigeration system

Note: Marks "√" and "×" indicate the state of switching valve "open" and "closed" respectively.

The design COP of the ejector refrigeration system is determined by the state of the fluid at the inlet and outlet of the ejector in the design condition, that is, by the set generation temperature, set evaporation temperature and set condensation temperature. Such as the simplified method of traditional ejector refrigeration system design proposed by Khalil et al. .1684-1698). The set generation temperature, set evaporation temperature, and set condensation temperature are determined according to the heat source, cooling purpose, and cold source, respectively. Typically, the heat source, cooling purpose, and heat sink allow for a temperature range rather than a temperature point. For example, in the prior art, at the set generation temperature of 70°C to 95°C, the set evaporation temperature of 5°C to 15°C, and the set condensation temperature of 25°C to 35°C, the spray refrigeration system using environmentally friendly refrigerants is studied design performance. For traditional jet refrigeration systems, within the allowable temperature range of the heat source, cooling purpose, and cold source, the higher the set generation temperature, the higher the set evaporation temperature, and the lower the set condensation temperature, the greater the system design COP. As for the steam pressurized injection refrigeration system, due to the problem of waste of heat energy (during the cooling sub-process, the high-temperature and high-pressure steam is cooled in the liquid storage tank 17, resulting in waste of heat energy), according to the traditional selection rules for setting the generation temperature, it is possible Resulting in minimal system design COP.

In practical applications, the temperature allowed by the heat source is wide, such as various solar collectors and various industrial waste heat; that is, the steam pressurized jet refrigeration system can choose to set the generation temperature within a wide temperature range. In the prior art, there is no solution that can guide the precise selection of the set generation temperature within a wide temperature range, so as to ensure the optimal COP of the design of the vapor supercharged ejection refrigeration system.

Contents of the invention

The purpose of the present invention is to solve the problem of setting the temperature during the design of the vapor booster injection refrigeration system when the temperature range of the heat source is wide, so as to make the system design refrigeration coefficient (that is, the system design COP) optimal.

The invention provides a generation temperature setting method used in the design of a steam pressurization injection refrigeration system. The set generation temperature determined according to the method can realize the optimal design COP of the steam pressurization injection refrigeration system.

The technical scheme adopted for realizing the object of the present invention is as follows. A method for setting the generation temperature of a vapor booster injection refrigeration system, the vapor booster injection refrigeration system at least includes a set of multifunctional generator subsystems and a set of refrigeration subsystems; the multifunctional generator subsystem includes A generator of liquid refrigerant, and a liquid storage tank connected to the generator in a closed loop for transfer and recovery of liquid refrigerant; the refrigeration subsystem includes an ejector, a condenser, a throttling element and an evaporator sequentially connected in a closed loop; the multifunctional generator The subsystem and the refrigeration subsystem are connected in the following way: the outlet of the high-temperature and high-pressure steam of the generator is connected with the inlet of the working fluid of the ejector, and the inlet of the condensate of the liquid storage tank is connected with the outlet of the condensate of the condenser; Refrigeration stage and pressurization stage are carried out in turns; the pressurization stage includes three sub-processes of pressurization, liquid return and cooling in sequence; it is characterized in that the set occurrence temperature is determined according to the maximum design COP of the vapor booster injection refrigeration system; The system design COP is the ratio of the output cooling capacity of the system to the input heat energy under the design working conditions, and is calculated according to the following formula:

In the formula, COP is the design refrigeration coefficient of the vapor booster injection refrigeration system (unit: dimensionless);

h ₁₁ is the specific enthalpy of the saturated liquid refrigerant at the set condensation temperature (unit: kJ/kg);

h ₁₂ is the specific enthalpy of the saturated gaseous refrigerant at the set condensation temperature (unit: kJ/kg);

v ₁₁ is the specific volume of saturated liquid refrigerant at the set condensing temperature (unit: m ³ /kg);

v ₁₂ is the specific volume of saturated gaseous refrigerant at the set condensation temperature (unit: m ³ /kg);

h ₂₁ is the specific enthalpy of the saturated liquid refrigerant at the set temperature (unit: kJ/kg);

h ₂₂ is the specific enthalpy of the saturated gaseous refrigerant at the set generation temperature (unit: kJ/kg);

v ₂₁ is the specific volume of saturated liquid refrigerant at the set temperature (unit: m ³ /kg);

v ₂₂ is the specific volume of saturated gaseous refrigerant at the set temperature (unit: m ³ /kg);

h _eG is the specific enthalpy of the saturated gaseous refrigerant at the set evaporation temperature (unit: kJ/kg);

w is the injection ratio of the injector (unit: dimensionless).

The ejector design generation temperature setting method of the steam pressurized injection refrigeration system is characterized in that the highest temperature allowed by the refrigeration purpose is selected as the set evaporation temperature, and the lowest temperature allowed by the cold source temperature is selected as the set condensation temperature. Within the temperature range allowed by the heat source, use the above system design COP calculation formula to calculate the system design COP at different set occurrence temperatures; find the maximum system design COP; the set occurrence temperature value corresponding to the maximum system design COP is the final selected design fixed temperature.

Based on the analysis of the thermodynamic process of the steam pressurized injection refrigeration system, the calculation formula of the system design COP can be derived, as follows.

System design COP is defined as the ratio of system output cooling capacity to input heat energy, such as formula (1).

In the formula, COP is the design refrigeration coefficient of the vapor _{booster injection} refrigeration system (unit: dimensionless); w is the injection ratio of the _ejector (unit: dimensionless); , the pressurization sub-process is used to pressurize the condensate from the condenser 16 in the liquid storage tank 17, and the liquid return sub-process is used to push the pressurized liquid in the liquid storage tank 17 to flow back into the generator 19 from the generator 19 The mass of high-temperature and high-pressure steam (unit: kg); h _eG is the specific enthalpy of saturated gas refrigerant at the set evaporation temperature (unit: kJ/kg); h ₁₁ is the specific enthalpy of saturated liquid refrigerant at the set condensing temperature (unit: kJ/kg); h ₂₁ is the specific enthalpy of saturated liquid refrigerant at the set generation temperature (unit: kJ/kg); h ₂₂ is the specific enthalpy of saturated gaseous refrigerant at the set generation temperature (unit: kJ /kg).

According to the law of mass conservation, at the end of the refrigeration phase, the quality of the refrigerant in the liquid storage tank 17 was equal to the quality of the refrigerant entering the liquid storage tank 17 from the condenser 16 and the amount left in the liquid storage tank 17 in the cooling sub-process of the last working cycle. The sum of the quality of the lower refrigerant; the quality of the refrigerant entering the liquid storage tank 17 from the condenser 16 is equal to the quality of the high-temperature and high-pressure steam as the working fluid in the refrigeration stage; the liquid storage tank 17 is left in the cooling sub-process of the last working cycle The mass of the refrigerant is the mass of the gaseous refrigerant in the liquid storage tank 17 at the end of the liquid return sub-process (formula (2)). When the liquid return sub-process ends, the entire liquid storage tank 17 is filled with gaseous refrigerant (formula (3)).

m _1G +m _1L =M _g1 +m _3G (2)

m _3G ×v ₂₂ = Vol _ev (3)

In the formula, m _1L and m _1G are the masses of liquid refrigerant and gaseous refrigerant in the liquid storage tank 17 at the end of the refrigeration stage respectively (unit: kg); m _3G is the mass of the liquid refrigerant in the liquid storage tank 17 at the end of the liquid return sub-process The mass of the refrigerant (unit: kg); Vol _ev is the volume of the liquid storage tank 17 (unit: m ³ ); v ₂₂ is the specific volume of the saturated gaseous refrigerant at the set generation temperature (unit: m ³ /kg).

According to the law of conservation of mass, the sum of the mass of the high-temperature and high-pressure steam produced by the generator 19 for the above three functions should be equal to the mass of the liquid refrigerant entering the generator 19 from the liquid storage tank 17 during the liquid return sub-process. The volume of the liquid refrigerant entering the generator 19 during the liquid return sub-process is equal to the volume of the liquid storage tank 17 (formula (4)). If the volume of the liquid refrigerant entering the generator 19 in the liquid return sub-process is less than the volume of the liquid storage tank 17, the quality of the liquid refrigerant entering the liquid storage tank 17 from the condenser 16 in the refrigeration stage is relatively small, that is, the cooling stage works The quality of the fluid is too small, resulting in a small cooling capacity and poor system performance; but the volume of liquid refrigerant entering the generator 19 during the liquid return process cannot be greater than the volume of the liquid storage tank 17, because the liquid return sub process The liquid refrigerant entering the generator 19 is stored in the liquid storage tank 17 first.

(M _g1 +M _g2 +M _g3 )×v ₂₁ ＝Vol _ev (4)

In the formula, v ₂₁ is the specific volume of the saturated liquid refrigerant at the set generation temperature (unit: m ³ /kg).

Since the liquid return sub-process starts, the liquid storage tank 17 is full of liquid refrigerant, and when the liquid return sub-process ends, the liquid storage tank 17 is full of gaseous refrigerant, so the liquid return sub-process is used to promote the return of liquid in the liquid storage tank 17 The quality of the high-temperature and high-pressure steam produced by the generator 19 is equal to the quality of the high-temperature and high-pressure steam of the volume liquid storage tank 17 (formula (5)).

M _g3 ×v ₂₂ = Vol _ev (5)

In addition, the pressurization sub-process obeys the law of energy conservation and mass conservation (Equation (6) and Equation (7)). At the end of pressurization, the liquid refrigerant just fills the entire liquid storage tank 17; that is, no liquid refrigerant overflows the liquid storage tank 17 during the pressurization process, otherwise it will cause pressure disturbance in the generator 19, which is not conducive to the stable operation of the system.

In the formula, h ₁₂ is the specific enthalpy of the saturated gaseous refrigerant at the set condensation temperature (unit: kJ/kg).

In order to correlate the volume of the liquid storage tank 17 in the pressurization stage, formulas (8)-(10) can be obtained from the physical properties of the refrigerant.

m _1L ×v ₁₁ ＝Vol _evL (8)

m _1G ×v ₁₂ = Vol _evG (9)

Vol _evL + Vol _evG = Vol _ev (10)

In the formula, Vol _evL and Vol _evG are respectively the volumes occupied by the liquid refrigerant and the gas refrigerant in the liquid storage tank 17 at the end of the cooling phase.

Integrating formulas (1)-(10), the design COP of the vapor booster jet refrigeration system can be obtained as formula (11).

From the COP calculation formula (11), it can be seen that the design COP of the vapor booster injection refrigeration system is only determined by the specific enthalpy and specific volume of the refrigerant at the set generation temperature, set evaporation temperature, and set condensation temperature, and the injection ratio of the ejector. Decision: The design COP of the vapor booster injection refrigeration system has nothing to do with the cooling capacity and the configuration of the multifunctional generator (such as the volume of the liquid storage tank 17). The specific enthalpy and specific volume of the refrigerant can be easily obtained from professional software. There are different methods to accurately calculate the injection ratio of the injector, such as the existing one-dimensional model of the injector. Therefore, the system design COP calculation formula (Equation (11)) can simplify the calculation of the design COP of the vapor booster injection refrigeration system, and easily obtain the influence of the set temperature on the system design COP.

The design COP of the traditional ejector refrigeration system increases monotonically with the increase of the set temperature. However, the design COP of the vapor booster injection refrigeration system can first increase and then decrease with the increase of the set temperature, that is, there is a maximum value, and the reasons are as follows. Raising the set point temperature exerts both positive and negative effects on the design COP of a vapor booster ejection refrigeration system. Among them, the positive impact: the injection ratio increases with the increase of the set temperature, which reduces the heat energy input required for the unit cooling capacity, which is beneficial to the improvement of the system design COP. Negative impact: In one working cycle of the steam pressurization injection refrigeration system, after the pressurization sub-process is completed, the liquid storage tank 17 is filled with high-temperature and high-pressure steam; this part of high-temperature and high-pressure steam is directly absorbed by the cooling water jacket 18 The cooling of the cooling water causes the heat energy contained in it to be wasted; the waste of heat energy leads to the need to input more heat energy for the production unit cooling capacity; with the increase of the set temperature, the temperature and quality of the high-temperature and high-pressure steam in the liquid storage tank Both increase (because the density of gaseous refrigerant increases with the increase of temperature), resulting in more waste of heat energy, thus hindering the improvement of system design COP. When the set temperature is low, there is not much heat energy wasted, and the positive effect dominates, that is, the system design COP increases with the increase of the set temperature. When the set temperature is higher, more and more heat energy is wasted, and the negative effect dominates, that is, the system design COP decreases with the increase of the set temperature. When the positive effect and the negative effect are just in balance, the system design COP has the maximum value. The set occurrence temperature corresponding to the maximum system design COP is defined as the optimum set occurrence temperature.

It is worth noting that, "within the allowable temperature range of the heat source", there are three situations in which the system design COP changes with the set temperature. First, the temperature of the heat source is appropriate, and the COP of the system design can first increase and then decrease with the increase of the set generation temperature, that is, the optimal set generation temperature is within the temperature range allowed by the heat source; the generation temperature should be set at the optimum set generation temperature temperature. Second, if the temperature of the heat source is too high, the system design COP will decrease with the increase of the set temperature, that is, the optimal set temperature is lower than the temperature range allowed by the heat source; the temperature should be set at the lowest temperature allowed by the heat source. Third, the temperature of the heat source is too low, and the system design COP increases with the increase of the set generation temperature, that is, the optimal set generation temperature is higher than the temperature range allowed by the heat source; the generation temperature should be set at the maximum temperature allowed by the heat source.

Since the selection of the set evaporating temperature and the set condensing temperature can affect the system design COP and the optimal set generating temperature, the appropriate set evaporating temperature and set Set the condensation temperature.

Increasing the set evaporating temperature is beneficial to increase the design COP of the vapor booster injection refrigeration system and reduce the optimal set occurrence temperature for the following reasons. Raising the set evaporating temperature has no effect on the supercharging stage, that is, it has no effect on the waste of heat energy, but it increases the injection ratio, thereby reducing the heat energy input to produce unit cooling capacity, so the system design COP increases. Due to the reduction of heat energy input required to produce a unit of cooling capacity, the positive impact of increasing the set generation temperature on the system design COP is weakened, so that the negative impact of increasing the set generation temperature on the system design COP is more likely to dominate. That is, the balance of positive influence and negative influence occurs at a lower setting occurrence temperature, so the optimal setting occurrence temperature decreases. Lowering the optimal set-off temperature is beneficial to the use of lower-grade heat sources. Therefore, when selecting the set temperature of the steam booster injection refrigeration system, the evaporation temperature should be set at the highest temperature allowed by the cooling purpose.

Lowering the set condensing temperature is beneficial to increase the design COP of the vapor booster injection refrigeration system and lower the optimum set temperature for the following reasons. Lowering the set condensing temperature simultaneously reduces the thermal energy required in the refrigeration stage and increases the thermal energy required in the pressurization stage, but the former is more significant than the latter, so the system design COP increases. Due to the decrease of thermal energy required in the cooling stage (i.e., the reduction of thermal energy input required to produce a unit of cooling capacity) and the increase in the thermal energy required in the pressurization phase (i.e., the increase in wasted heat energy of producing a unit of cooling capacity), the increase setting occurs. The positive impact of temperature on the system design COP is weakened but the negative impact is enhanced, so that the negative impact is more likely to dominate, that is, the balance of positive impact and negative impact occurs at a lower set occurrence temperature, so the optimum set occurrence temperature decreases . Therefore, when selecting the set temperature of the steam pressurized injection refrigeration system, the condensation temperature should be set at the lowest temperature allowed by the purpose of the cold source.

In summary, the set generation temperature selected according to the method of the present invention can maximize the design COP of the vapor booster injection refrigeration system.

Further, the set generation temperature is used for the size design of the ejector of the non-circulation pump type vapor booster refrigeration system.

Description of drawings

Figure 1 is a schematic diagram of a traditional jet refrigeration system;

Fig. 2 Schematic diagram of steam pressurized injection refrigeration system;

Fig. 3 is the change graph of the density of saturated gaseous state R134a with temperature;

Figure 4 is a graph showing the variation of the design COP of the vapor booster injection refrigeration system with the set temperature at different set evaporation temperatures (R134a is the refrigerant, and the set condensation temperature is 30°C);

Figure 5 is a graph showing the variation of the design COP of the vapor booster injection refrigeration system with the set temperature at different set condensation temperatures (R134a is the refrigerant, and the set evaporation temperature is 10°C).

detailed description

The present invention will be further described below in conjunction with the examples, but it should not be understood that the scope of the subject of the present invention is limited to the following examples. Under the situation of not departing from above-mentioned technical thought of the present invention, according to common technical knowledge and conventional means in this field, make various replacements and changes (as adopting different refrigerants, R1234yf, R1234ze (E), R290, R161, R152a and R600a, etc.), should be included in the protection scope of the present invention.

This embodiment is directed to the vapor booster injection refrigeration system shown in FIG. 2 as an example, and R134a [(1,1,1,2-tetrafluoroethane)] is used as the refrigerant. Assume that the allowable temperature range of the heat source is 75°C to 90°C. R134a is a commonly used refrigerant in jet refrigeration systems, and 75°C to 90°C is the common heat source temperature range for jet refrigeration systems. Because the density of saturated gaseous state R134a increases with the rise of temperature (as shown in Figure 3), the quality of the cooled high-temperature and high-pressure steam in the liquid storage tank 17 increases with the rise of the set generation temperature, so that it is wasted The thermal energy increases with the increase of the set temperature, resulting in the maximum design COP and the optimal set temperature of the vapor booster injection refrigeration system. With the help of Engineering Equation Solver and the ejector ratio calculation method proposed by Khalil et al. (see Khalil A, Fatouh M, Elgendy E. Ejector design and theoretical study of R134a ejector refrigeration cycle [J]. International Journal of refrigeration, 2011, 34(7): 1684-1698.), according to the calculation formula (11) of the design COP of the steam pressurized injection refrigeration system, the change of the system design COP with the set occurrence temperature under different set evaporation temperatures and set condensation temperatures can be obtained. As shown in Figure 4, when the cold source allows the lowest temperature T _c = 30°C, that is, the set condensation temperature is 30°C, and the maximum temperature T _e allowed by the cooling purpose is 13°C, 12°C, 11°C, 10°C, 9°C and At 8°C (that is, the set evaporation temperatures are 13°C, 12°C, 11°C, 10°C, 9°C, and 8°C), the optimal set generation temperatures T _{vg_opt} of the vapor booster injection refrigeration system are 82.0°C, 82.2°C, 82.4°C, 82.7°C, 83.0°C, and 83.3°C, the system design COPs corresponding to the optimal setting temperature are 0.237, 0.216, 0.197, 0.178, 0.159, and 0.141, respectively. Compared with the generation temperature setting method of the traditional injection refrigeration system (the generation temperature is set to the maximum temperature allowed by the heat source, that is, 90°C), the optimal setting of the generation temperature increases the system design COP by 23.35%, 22.42%, and 21.66% respectively. , 20.75%, 19.80% and 18.52%. As shown in Figure 5, when the maximum temperature T _e allowed for cooling purposes = 10°C (that is, the set evaporation temperature is 10°C), and the minimum temperature _Tc allowed by the cold source is 28°C, 29°C, 30°C, and 31°C, respectively , 32°C and 33°C (that is, the set condensing temperatures are 28°C, 29°C, 30°C, 31°C, 32°C and 33°C respectively), the optimal set generation temperature T _{vg_opt} of the vapor booster injection refrigeration system is respectively 81.5°C, 82.1°C, 82.7°C, 83.4°C, 84.0°C and 84.9°C. The system design COPs corresponding to the optimal setting temperature are 0.227, 0.202, 0.178, 0.155, 0.133 and 0.113, respectively. Compared with the traditional method of setting the generation temperature of the ejection refrigeration system, the optimum setting of the generation temperature increases the system design COP by 26.15%, 23.52%, 20.75%, 18.08%, 14.95% and 12.19%, respectively. In order to reduce the number of calculations, the above-mentioned optimal set occurrence temperature is obtained by using the cubic regression method on the basis of the system design COP and the change diagram of the set occurrence temperature; the R2 of the regression equation is greater ^than 99%, and the regression results are reliable.

It can be seen from Table 2 that when the set evaporating temperature (i.e. the maximum temperature allowed for refrigeration purpose) is higher and the set condensation temperature (i.e. the minimum temperature allowed by the cold source) is lower, the optimal setting temperature of the system is lower, and the maximum The greater the system design COP corresponding to the optimal setting temperature, the greater the increase percentage of the system design COP. The system design COP increase percentage refers to the increase percentage of the system design COP corresponding to the optimal set occurrence temperature relative to the system design COP corresponding to the set occurrence temperature (ie 90°C) selected by the traditional method. Therefore, the optimal setting of the generation temperature can effectively improve the design COP of the vapor booster injection refrigeration system, and the required heat source temperature is lower.

Table 2. The optimal set temperature of the steam pressurized injection refrigeration system under different set evaporation temperatures and set condensation temperatures, the system design COP corresponding to the optimal set temperature and the improvement percentage of the system design COP

Note: The system design COP increase percentage refers to the increase percentage of the system design COP corresponding to the optimal set occurrence temperature relative to the system design COP corresponding to the set occurrence temperature (ie 90°C) selected by the traditional method.

Claims (3)

1. a kind of steam compression-enhanced refrigeration system occurrence temperature establishing method, the steam compression-enhanced refrigeration system is at least wrapped Include a set of multifunction generato subsystem and a set of refrigeration subsystem；Multifunction generato subsystem is included for the liquid that gasifies The generator of state refrigerant and the fluid reservoir for transfer recovering liquid refrigerant that is connected with generator closed loop；Refrigeration subsystem System includes the injector, condenser, restricting element and the evaporator that are sequentially connected in a closed loop mode；Multifunction generato subsystem and refrigeration System is connected in the following manner：The outlet of generator high pressure high temperature vapor is connected with injector Working-fluid intaking, and fluid reservoir is cold Lime set entrance is connected with condenser condensate outlet；The steam compression-enhanced refrigeration system operation includes that circulation is carried out in turn Cooling stages and pressurization stages；Pressurization stages include the pressurization for carrying out successively, return three subprocess of liquid and cooling；Its feature exists According to the design coefficient of refrigerating performance (COP) that steam compression-enhanced refrigeration system is maximum, it is determined that setting occurrence temperature.System design COP is calculated according to equation below：

$\begin{array}{c}COP\\ =\frac{\left(\right(v_{22}-v_{12})v_{21}{h}_{11}-(v_{22}-v_{11})v_{21}{h}_{12}+(v_{12}-v_{11})v_{22}{h}_{21}-(v_{12}-v_{11}\left)\right(v_{22}-v_{21}\left)h_{22}\right)(h_{eG}-h_{11})w}{\left(v_{11}{v}_{22}\right(h_{22}-h_{12})-v_{12}{v}_{22}(h_{22}-h_{11}\left)\right)(h_{22}-h_{21})}\end{array}$

In formula, COP is that steam compression-enhanced refrigeration system designs coefficient of refrigerating performance, is defined as the cold of system output under design conditions With the ratio (unit of the heat energy of input：Dimensionless)；

h₁₁It is the specific enthalpy (unit of saturation liquid refrigerant under setting condensation temperature：kJ/kg)；

h₁₂It is the specific enthalpy (unit of saturation gaseous refrigerant under setting condensation temperature：kJ/kg)；

v₁₁It is the specific volume (unit of saturation liquid refrigerant under setting condensation temperature：m³/kg)；

v₁₂It is the specific volume (unit of saturation gaseous refrigerant under setting condensation temperature：m³/kg)；

h₂₁It is the specific enthalpy (unit of saturation liquid refrigerant under setting occurrence temperature：kJ/kg)；

h₂₂It is the specific enthalpy (unit of saturation gaseous refrigerant under setting occurrence temperature：kJ/kg)；

v₂₁It is the specific volume (unit of saturation liquid refrigerant under setting occurrence temperature：m³/kg)；

v₂₂It is the specific volume (unit of saturation gaseous refrigerant under setting occurrence temperature：m³/kg)；

h_eGIt is the specific enthalpy (unit of saturation gaseous refrigerant under setting evaporating temperature：kJ/kg)；

W is the injection ratio (unit of injector：Dimensionless).

2. steam compression-enhanced refrigeration system as claimed in claim 1 designs occurrence temperature establishing method, it is characterised in that choosing The maximum temperature of refrigeration purpose permission is taken as setting evaporating temperature, the minimum temperature for choosing sink temperature permission is cold as setting Solidifying temperature, within the temperature range of thermal source permission, calculates different using the system design COP computing formula described in claim 1 System design COP under setting occurrence temperature；Find maximum system design COP；The corresponding setting hairs of maximum system design COP Raw temperature value is the setting occurrence temperature of final choice.

3. steam compression-enhanced refrigeration system as claimed in claim 1 or 2 designs occurrence temperature establishing method, and its feature exists In：The setting occurrence temperature is used to be pressurized without circulating pump type steam the injector size design of refrigeration system.