Research on Dynamic Modeling of a High Temperature Steam Heat Pump

In order to improve industrial energy efficiency, a high temperature heat pump using R245fa as refrigerant is investigated in this artical. The system model contains two cycles, i.e., vapor compression cycle and steam generation cycle. Seven sub-models representing two condensers, evaporator, flash tank, scroll compressor, water injected screw compressor and two thermal expansion valves (TEV) are included in this system. A moving boundary (MB) approach based on mass and energy balance principles is implemented for the heat-exchangers and flash evaporation dynamic models, while the compressors and TEVs adopt steady models because of their much smaller thermal inertia compared with the heat-exchangers. The system has three control variables, including the valve opening, scroll compressor operation frequency and rotation speed of screw compressor. Steady state performance of the system is first analyzed and then the dynamic characteristics of the system are simulated and analyzed in order to better control it.