Research On Operation Characteristics Of Wshp Unit Under Condensation Temperature

In recent years, heat pump unit has been widely used in building heating in China. The design of general water source heat pump unit is under the condition of the ground coil and fan coil units as terminal device. That is, water supply temperature of general water source heat pump unit under heating conditions is between 45℃and 50℃. However many terminal device need higher supply temperature in the practical application, for example, water supply temperature is 60℃. In this case, general heat pump unit operating under the condensation temperature of 65℃will exceed the nominal heating conditions range of general heat pump unit,which will affect the operation efficiency and stability of general heat pump unit to a certain extent. Therefore it has practical significance to modify general water-source heat pump unit which operates high efficiently and stable under the condensation temperature of 65℃. The main contents are as follows:(1)Taking R134a as refrigerant, Theoretical calculation is performed for the four style refrigeration cycle which are single stage compression, single stage regeneration, one time throttling with intermediated completely cooling and one time throttling and intermediated incompletely cooling in the design condition which evaporation temperature is 2℃; condensation temperature is 65℃; heat output is 298kW, the performance coefficients under that four style refrigeration cycle are respectively 3.8,3.9345,3.934,4.014. In order to make the system simple, the unit in this paper adopts the refrigeration cycle mode of single stage compression and increases certain superheat and supercooling.(2)Relevant equipments of heat pump unit is selected and design calculated under the condition which evaporation temperature is 2℃; condensation temperature is 65℃; heat output is 298kW, superheat is 10℃;subcooling is 5℃. The power of the screw compressor is 89.7 kW, through calculating we know the heat exchange area of dry type shell and tube evaporator is 28m2, the heat exchange area of horizontal shell and tube condenser is 10.4m2. And the heating performance coefficient of the unit in the design condition is up to 4.5, and it is up to 3.93 if evaporation temperature is 0℃.(3)The performance of the water source heat pump unit is tested on the experiment table. By testing we know heating performance coefficient of the water source heat pump unit is 4 when the unit operates stable under the design condition. In the condition of evaporate temperature is 0℃,condensation temperature is 65℃, the heating performance coefficient of the heat pump unit is 3.55 when the water source heat pump unit operates stable. According to the experimental test analysis of the heat pump unit in full load and part load operating condition, and considering limit working condition of the screw compressor. The high efficient and stable condition of the water source heat pump unit is: lowest evaporation temperature is 0℃, highest condensation temperature is 65℃. In this range condition, the heat pump unit can be used widely.(4)The analysis of economic performance of the MSRB25A water source heat pump unit,MSRB25 water source heat pump unit and 90sh air source heat pump unit is made. The heating performance coefficient of these three heat pump unit under the condition of evaporation temperature is 2℃,condensation temperature is 65℃respectively 4,2.73,3.2. Therefore, the heating performance coefficient of the MSRB25A is the highest; the cost of the MSRB25A and MSRB25 are approximately equal, the cost of the MSRB25A is three million lower than the 90sh.