Keywords: Air source heat pump , process
1, overview
Air source heat pump has the advantages of wide application range, can be used all year round, high energy efficiency, it can save about 70% of energy, is environmentally friendly and harmless, has no combustion emissions, will not cause damage to our health, is easy to use, and has small space occupancy. Extremely suitable for large central heating.
The working principle of the air source heat pump is based on the "Inverse Kano Cycle". The organic working fluid continuously exchanges heat with water, throttling, absorbs air heat, and pressurizes and heats up the compressor to complete the working fluid cycle, absorbs air heat + the injected energy of the compressor is much greater than the heat obtained by electric heating. Based on process calculation, this paper explores the technical economy of the air source heat pump process.
2, circulating working fluid
The following are the physical properties parameters of several circulating working fluids suitable for air source heat pumps used in the north.
3, air source heat pump process flow
low-pressure and low-temperature gas phase working fluid is pressurized and heated by the compressor to become a high-pressure and high-temperature gas phase working fluid. The high-pressure and high-temperature gas phase working fluid is heat exchanged with cold water in the condenser /hot water tank and condensed into a high-pressure medium-temperature liquid working fluid. The high-pressure and medium-temperature liquid working fluid is reduced to a low-pressure and low-temperature two-phase working fluid after passing through the throttle valve . The low-pressure and low-temperature two-phase working fluid is heat exchanged with the air (absorbing heat from the air) and becomes a low-pressure and low-temperature gas phase working fluid, and the working fluid completes a complete closed cycle.
4, process simulation calculation
l According to the brief description of the air source heat pump process in Section 3, establish the process simulation calculation process of this process.
low-pressure and low-temperature gas phase working fluid R10 is pressurized and heated by compressor C1A/C1B. The high-pressure and high-temperature gas phase working fluid R12 is heat exchanged with cold water R20 in the condenser/hot water tank E11 and condensed into high-pressure medium-temperature liquid working fluid R13. After the cold water R20 is heated, R21 goes to the water use place. The high-pressure medium-temperature liquid working fluid R13 is reduced to low-pressure and low-temperature two-phase working fluid R14 through the throttle valve V1. The low-pressure and low-temperature two-phase working fluid R14 is then absorbed from the heat exchanger E12 and then becomes low-pressure and low-temperature gas phase working fluid R15/R10. The working fluid completes a complete closed cycle.
Below are the basic process parameters used by an air source heat pump.
5. Analysis of process parameters affecting the air source heat pump when the circulating working fluid is R115
Process parameter value is shown in item 4.2, and the corresponding relationship between heat pump power and working fluid flow, hot water yield, air circulation, and compressor theoretical power is examined.
The relationship between heat pump power and circulating working fluid R115 flow rate conforms to the linear relationship formula, and the regression calculation result is as follows.
where: PR115-heat pump power, KW; LR115-working fluid flow, kg/h; A0R115=-0.00048; A1R115=0.02396
where: LWR115-hot water yield, kg/h; B0R115=-2.70667; B1R115=55.26430
Where: PCR115-compressor theoretical power, KW; C0R115=0.00481; C1R115=3.58930
Where: D0R115=-2.44246; D1R115=198.36004
6. Analysis of process parameters affecting the air source heat pump when the circulating working fluid is R22
Process parameter value is shown in item 4.2, and the corresponding relationship between heat pump power and working fluid flow, hot water yield, air circulation, and compressor theoretical power is examined.
The relationship between heat pump power and circulating working fluid R22 flow rate conforms to the linear relationship formula, and the regression calculation result is as follows.
Where: PR22-heat pump power, KW; LR22-working fluid flow, kg/h; A0R22=1.95436; A1R22=0.05420
Where: LWR22-hot water yield, kg/h; B0R22=2.62667; B1R22=55.27879
Where: PCR22-compressor theoretical power, KW; C0R22=0.02152; C1R22=4.05537
Where: D0R22=3.82207; D1R22=222.51705
7. Analysis of process parameters affecting the air source heat pump when the circulating working fluid is R143
. The process parameter value is shown in item 4.2. The corresponding relationship between heat pump power and working fluid flow, hot water yield, air circulation, and compressor theoretical power is examined.
The relationship between heat pump power and circulating working fluid R143 flow rate conforms to the linear relationship formula, and the regression calculation result is as follows.
Where: PR143-heat pump power, KW; LR143-working fluid flow, kg/h; A0R143=0.00059; A1R143=0.04401
Where: LWR143-hot water yield, kg/h; B0R143=2.6600; B1R143=55.19945
Where: PCR143-compressor theoretical power, KW; C0R143=-0.02388; C1R143=3.58462
Where: D0R143=1.34345; D1R143=197.86883
8. Analysis of process parameters affecting the air source heat pump when the circulating working fluid is R125
The relationship between heat pump power and circulating working fluid R125 flow rate conforms to the linear relationship formula, and the regression calculation result is as follows.
Where: PR125-heat pump power, KW; LR125-working fluid R125 flow, kg/h; A0R125=0.00000; A1R125=0.02739
Where: LWR125-hot water yield, kg/h; B0R125=9.06667; B1R125=55.03352
Where: PCR125-compressor theoretical power, KW; C0R125=0.00002; C1R125=3.26526
Where: D0R125=9.03207; D1R125=179.70007
9. Analysis of process parameters that affect the power of the air source heat pump when the circulating working fluid is R32
Process parameter value is shown in item 4.2, and the corresponding relationship between heat pump power and working fluid flow, hot water yield, air circulation, and compressor theoretical power is examined.
The relationship between heat pump power and circulating working fluid R32 flow rate conforms to the linear relationship formula, and the regression calculation result is as follows.
Where: PR32-heat pump power, KW; LR32-working fluid flow, kg/h; A0R32=0.00291; A1R32=0.08737
Where: LWR32-hot water yield, kg/h; B0R32=-0.14000; B1R32=55.28582
Where: PCR32-compressor theoretical power, KW; C0R32=0.01017; C1R32=3.80447
Where: D0R32=0.42254; D1R32=210.33330
10. Analysis of the process parameters of heat pumps in different working fluids air sources
The theoretical power ratio of heat pumps of different working fluids and compressors is shown in the table below. The larger the ratio, the more heat the system absorbs from the air, and the higher the efficiency of the heat pump system.
The hot water yield and the theoretical power ratio of the compressor of different working fluids are shown in the table below. The larger the ratio, the more hot water is produced by the system and the higher the efficiency of the heat pump system.
As can be seen from the above table, for the northern region, according to the principle of maximizing the efficiency of the heat pump system, the priority order of the working fluid used by the air source heat pump is R22R32R115R143R125.
Next, consider factors such as the usage volume and service life of the circulating working fluid to comprehensively evaluate the circulating working fluid used.
11, Conclusion
This paper establishes a generalized model for air source heat pump process calculation, and analyzes the influencing factors of several circulating working fluids suitable for use in northern regions on the process parameters of air source heat pumps.
The calculation method in this paper is broad-spectrum adaptability and can be used as a reference for air source heat pump process calculation.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-