Background
The distributed energy supply system mainly adopts clean energy sources, such as natural gas, solar energy, wind energy, geothermal energy and the like, and improves the energy supply efficiency and reduces pollution and emission by coupling various energy sources together and utilizing the cascade utilization principle of energy. Distributed energy systems are used primarily in remote small towns, large commercial complexes, and large industrial parks. In recent years, as the manufacturing industry of China is upgraded, the construction of a supply chain is often concentrated on a large-scale industrial park and an incubation base. The development of distributed energy supply systems has also been driven by the fact that related industries often have similar energy usage requirements, especially high-grade energy requirements. The distributed energy supply system can provide different types and quality of energy forms such as electric energy, heat energy, cold energy, steam and the like for related industries, and can greatly reduce the initial investment and the operation cost of each enterprise in an industrial park.
As the supply efficiency of the distributed energy supply system requiring the maximum heat energy, there is often a significant influence on the energy utilization rate of the entire distributed energy supply system. The industry generally adopts an absorption heat pump to supply heat, and particularly adopts a large-scale heating system, and the energy supply mode has large heating capacity and is driven by heat energy, so the absorption heat pump is considered to be energy-saving and environment-friendly. However, the absorption heat pump often needs to use high-quality steam to drive, which aggravates the problem of thermoelectric coupling and also often causes the reduction of energy utilization efficiency. The steam compression type heat pump energy supply system is driven by electric energy, is more flexible to apply, and can greatly improve the waste heat utilization level by adopting high-efficiency environment-friendly working media, reduce the complexity of the energy supply system and improve the energy supply efficiency.
For a vapor compression type heat pump energy supply system, the thermodynamic property of a working medium plays a key role in the energy conversion efficiency of the heat pump system. Considering that the temperature of a common commercial or residential heat source is about 70-80 ℃, the critical temperature of the working medium of the heat pump cannot be lower than 90 ℃ so as to prevent larger throttling and heat exchange losses. The existing heat pump working media such as R134a, R161 and the like and mixtures thereof often have the problems of large greenhouse effect potential GWP, large phase change slip temperature and low efficiency, and especially the problem of flammability limits the filling amount of the working media in the system, thus preventing the working media from being applied to a large-scale compression heat pump system. Therefore, the need for developing a heat pump working medium with a higher heating coefficient and more environmental protection and safety is particularly urgent.
Disclosure of Invention
The invention aims to provide a mixed working medium which is used for providing a heat source of 70-80 ℃ in a heat pump system, has lower GWP, higher heat supply coefficient and larger heat production quantity per unit volume, is suitable for the pressure ratio of a high-capacity centrifugal compressor and smaller comparative slip temperature, and is a heat pump mixed working medium with low replacement cost because a common refrigerant is adopted as a principal element.
The invention provides a ternary mixed working medium for a heat supply heat pump in a distributed energy system, which comprises the following raw materials in percentage by mass:
trifluoroiodomethane CF3I:90% ~ 96%;
Propane R290+ propene R1270: 4% -10%; wherein the mass percent of the propane is 1-9%, and the mass percent of the propylene is 1-9%;
wherein the sum of the mass percentages of all the components is 100 percent;
the ozone destruction potential of the obtained mixed working medium is 0, and the greenhouse effect potential is less than 20.
The mixed working medium comprises the following raw materials in percentage by mass:
trifluoroiodomethane CF3I:92%;
Propane R290: 2 percent;
propylene R1270: 6 percent;
wherein the sum of the mass percentages of all the components is 100 percent.
The mixed working medium is prepared by mixing CF3And I, R290 and R1270 are physically mixed in a liquid phase according to the corresponding mass ratio.
The invention provides application of a ternary mixed working medium of a heat supply heat pump in the distributed energy system in a high-capacity heat supply heat pump system.
In the application, the high-capacity heat supply heat pump system comprises a heat pump system for commercial and residential hot water at 70-80 ℃; the GWP of the mixed working medium is lower than 20, and the coefficient of heat supply COPhThe heat production per unit volume is 4300 kJ · m at 4.612-4.745-3~ 4901kJ·m-3The method is suitable for the conditions that the pressure ratio of the centrifugal compressor is 3.25-3.31 and the comparative slip temperature is 1.63-3.26 ℃.
The invention has the beneficial effects that:
(1) the environment performance is excellent, the ozone destruction potential ODP value is 0, and the greenhouse effect potential GWP is lower than 20;
(2) the temperature slippage is small, the COP value of the heat supply coefficient and the unit volume heating capacity are high, and the system volume can be reduced;
(3) the components are common refrigerants, and the refrigerant is low in price and easy to obtain.
Detailed Description
The invention provides a refrigerant, and the preparation method is that CF is prepared3I, R290 and R1270 according to their phasesThe required mass ratio is physically mixed in a liquid phase state. The individual component properties are listed in table 1.
The following examples are provided to illustrate the practice of the present invention, but the present invention is not limited to the following examples, and all the concepts of the present invention including the components, the proportions, and the mixed refrigerant screening concept of the present invention are within the scope of the present invention.
The following 24-ratio example was performed, and the optimum performance point sought was calculated:
example 1: the ratio of CF3I/R1270/R290 is as follows: 90%/1%/9%;
example 2: the ratio of CF3I/R1270/R290 is as follows: 90%/2%/8%;
example 3: the ratio of CF3I/R1270/R290 is as follows: 90%/3%/7%;
example 4: the ratio of CF3I/R1270/R290 is as follows: 90%/4%/6%;
example 5: the ratio of CF3I/R1270/R290 is as follows: 90%/5%/5%;
example 6: the ratio of CF3I/R1270/R290 is as follows: 90%/6%/4%;
example 7: the ratio of CF3I/R1270/R290 is as follows: 90%/7%/3%;
example 8: the ratio of CF3I/R1270/R290 is as follows: 90%/8%/1%;
example 9: the ratio of CF3I/R1270/R290 is as follows: 90%/9%/1%;
example 10: the ratio of CF3I/R1270/R290 is as follows: 92%/1%/7%;
example 11: the ratio of CF3I/R1270/R290 is as follows: 92%/2%/6%;
example 12: the ratio of CF3I/R1270/R290 is as follows: 92%/3%/5%;
example 13: the ratio of CF3I/R1270/R290 is as follows: 92%/4%/4%;
example 14: the ratio of CF3I/R1270/R290 is as follows: 92%/5%/3%;
example 15: the ratio of CF3I/R1270/R290 is as follows: 92%/6%/2%;
example 16: the ratio of CF3I/R1270/R290 is as follows: 92%/7%/1%;
example 17: the ratio of CF3I/R1270/R290 is as follows: 94%/1%/5%;
example 18: the ratio of CF3I/R1270/R290 is as follows: 94%/2%/4%;
example 19: the ratio of CF3I/R1270/R290 is as follows: 94%/3%/3%;
example 20: the ratio of CF3I/R1270/R290 is as follows: 94%/4%/2%;
example 21: the ratio of CF3I/R1270/R290 is as follows: 94%/5%/1%;
example 22: the ratio of CF3I/R1270/R290 is as follows: 96%/1%/3%;
example 23: the ratio of CF3I/R1270/R290 is as follows: 96%/2%/2%;
example 24: the ratio of CF3I/R1270/R290 is as follows: 96%/3%/1%;
calculating the working condition: the condensation temperature is 85 ℃, the evaporation temperature is 25 ℃, and the polytropic index is 1.09. The ratio of the clearance volume of the cylinder to the working volume is 0.08, the mechanical efficiency is 0.95, the motor efficiency is 0.78, the temperature coefficient is 0.9, and the leakage coefficient is 0.8. The degree of superheat on the evaporator side was taken to be 3 ℃ and the degree of supercooling on the condenser side was taken to be 5 ℃. The thermodynamic cycle employs a theoretical cycle with losses, with superheating and subcooling. The environmental, safety and cycling performance of each component is listed in table 1.
TABLE 1 component Properties and cycle Performance
As can be seen from Table 1, the vapor pressurep evThe air pressure is higher than the atmospheric pressure, so that the air is prevented from leaking into the working medium circulating system; condensing pressurep coThe lower the cost; corresponding pressure ratio of (π =p co / p ev) About 3, a large-flow centrifugal compressor can be adopted; refrigerating capacity per unit massq hAnd volumetric cooling capacityq hvThe difference is obvious, and R1270 has obvious advantages, so that the heating capacity, especially the volume heating capacity, of the mixed working medium can be obviously improved by containing the component, and the area and the investment of a heat exchanger are reduced; coefficient of heat supply COPhThe three working media are all higher; the global warming index GWP is small, and the environment performance is obvious; the three working media have lower toxicity, and the safety is the highest grade A; in the flammability aspect, the CF3I is rated at the highest 1 grade and is not flammable; r1270 and R290 are both combustible working media.
The cycle performance parameters of the three cycles under the given calculation condition are given in table 1, and the calculation results under the selected ternary mixed working medium proportion are listed in table 2.
TABLE 2 ternary mixed working medium CF3I/PROPANE/PROPYLEN calculation result
As can be seen from Table 2, the vapor pressure of the mixed working fluidp evThe air pressure is higher than the atmospheric pressure, so that the air is prevented from leaking into the working medium circulating system; condensing pressurep coThe lower the cost; corresponding pressure ratio of (π =p co / p ev) 3.25-3.31, a large-flow centrifugal compressor can be adopted; refrigerating capacity per unit massq hAnd volumetric cooling capacityq hvThe heat quantity, especially the volume heat quantity, of the mixed working medium is obviously improved, and the area and the investment of a heat exchanger are reduced; coefficient of heat supply COPhThe three working media are all higher; the global warming index GWP is small, and the environment performance is obvious; the three working media have lower toxicity, and the safety is the highest grade A; flammability aspect, CF3The grade I is the highest grade 1 and is non-combustible; r1270 and R290 are both combustible working media, so that the combustible working media and CF3The safety performance of the working medium can be obviously improved by mixing I.
CF3When the percentage content of I is 90 percent:
(1) the condensing pressure and the unit volume heating capacity are increased along with the increase of the PROPYLEN proportion, the requirement of the condensing pressure can be met when the PROPYLEN proportion is 0.01, and the unit volume heating capacity is 4695 kJ.m-3。
(2) The pressure ratio and the heating coefficient are basically unchanged, the pressure ratio is about 3.26, and the COPhThe temperature is kept at about 4.61-4.62.
CF3When the percentage content of I is 92 percent:
(1) condensing pressure and unit volume systemThe heat quantity is increased along with the increase of the PROPYLEN proportion, the requirement of condensation pressure can be met when the PROPYLEN proportion is 0.01-0.06, and the unit volume heating quantity is 4596-4749 kJ.m-3。
(2) The pressure ratio and the heating coefficient are basically unchanged, the pressure ratio is 3.27, and the COPhThe temperature is kept at about 4.65-4.66.
CF3When the percentage content of I is 94 percent:
(1) the condensing pressure and the unit volume heating capacity are increased along with the increase of the PROPYLEN proportion, the requirement of the condensing pressure can be met when the PROPYLEN proportion is 0.01-0.05, and the unit volume heating capacity at the moment is 4483-4609 kJ.m-3。
(2) The pressure ratio and the heating coefficient are basically unchanged, the pressure ratio is 3.29, and the COPhThe temperature is kept at about 4.69-4.7.
CF3When the percentage content of I is 96 percent:
(1) the condensing pressure and the unit volume heating capacity are increased along with the increase of the PROPYLEN proportion, the requirement of the condensing pressure can be met when the PROPYLEN proportion is 0.01-0.03, and the unit volume heating capacity is 4351-4417 kJ.m-3。
(2) The pressure ratio and the heating coefficient are basically unchanged, the pressure ratio is 3.3, and the COPhAnd remains at about 4.74.
In conclusion, the pressure ratio of the selected refrigerant is 3.1-3.3, the refrigerant is suitable for the pressure ratio range of a high-capacity centrifugal compressor, the temperature slippage in an evaporator and a condenser is 2-3.5, the refrigerant can be regarded as a near azeotropic working medium, the component change in the actual heat exchange process is not large, and therefore the cycle performance can be kept stable. The unit volume heating capacity is 4600-4900 kJ/m-3The heat supply coefficient is 4.6-4.7, and the economical efficiency is better. The optimal mixture ratio is as follows: trifluoroiodomethane (CF)3I) The method comprises the following steps 92%, propane (R290): 2%, propylene (R1270): 6% and the performance parameters are given in Table 2, example 11.