| Problems remains during the run of air-source heat pump in cold northern regions,such as exhaust temperature, attenuation of refrigerating capacity, frequent defrosting and low system coefficient of performance. Based on these problems, this thesis has analyzed the advantages and disadvantages of various types of heat transfer firstly. After choosing the appropriate super-cooling system, the work of the selection for critical parts, including compressor, expansion valve and heat transfer, has been finished.Finally, the Air Source Heat Pump units(ASHP) were designed. The operating performance of the system was tested in different operating conditions. And the operation energy consumption and running cost of the system can be simulated by using transient simulation software. Then the operating characteristics of the system and the factors which influence the energy efficiency of the designed units in low-temperature operating condition were analyzed.The simulation model of Air Source Heat Pump units and mathematical models of different modules of the unit, such as compressor, evaporator, expansion valve and capillary, were established. And the simulation program of the entire system was created.This thesis analyzed the meteorological data in Southern Liaoning by using software.And with the premises that to satisfy the supply and demand of hot water for slaughterhouse, the operation plans of air-source heat pump hot water system and solar-assisted electrically aided heat system were designed respectively to satisfy the hot-water supply of slaughterhouse. Then the transient simulation software can be used to simulate the operation plans and analyze the energy consumption, Thus the annual operation energy consumption and running cost of the system can be obtained through integration. Finally, after the comparison and optimization of the two plans, the economic analysis and environmental effect analysis of the plans above, as well as hot-water plan of gas-fired boiler, were completed.The operation performance of the designed.Air Source Heat Pump units was tested and the parameters which influence the operation of the system were analyzed. In the test, under different operating conditions, the change and correlative discipline of different parameters of Air Source Heat Pump units, such as evaporation temperature,condensation temperature, discharge temperature of compressor, heat capacity, energy consumption and energy efficiency ratio, were compared with the simulation results.The compare results showed that Air Source Heat Pump units are more sensitive to low temperature, and under low temperature, the heat capacity and the operating stability of system reduce. Height capacity zone of unit during running is the focus of improvement in the future and plays a critical role in the overall performance improvement of the unit.Finally, this thesis proposed several improvement methods of Air Source Heat Pump units in low temperature condition: in winter, the auxiliary heat equipment in the extreme weather is used to reduce the operation pressure of units, and combines the comprehensive performance of units throughout the year and the reduction of the initial costs; for engineering with large changes of energy consumption, modular units parallel design is adopted and the number of units started depends on the temperature outside to improve the comprehensive performance of units throughout the year; the technology such as multistage compression techniques and gas enthalpy increasing technology is used to improve the heat capacity under low temperature.Air source heat pump hot water system is an energy-saving equipment that integrates the Air source heat pumps units into hot water units,and it can not only provide hot water but also supply heating. Comparing with the other two hot program,Air Source Heat Pump units are superior to the solar-heated water systems in energy efficiency, and it is more energy-saving; it conforms with the policy of energy saving and emission reduction; at initial parts it has a better chance than the solar-heated water systems. Air Source Heat Pump units are designed and optimized to improve the performance of low temperature adaption of air source heat pumps, which distributes to the application of air source heat pump in the northern cold region. |
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