Intelligent High-performance Dynamic Control for Two-stage Screw High-temperature Heat Pump System

Abstract

In this study, we developed a new type of water-to-water two-stage screw heat pump with a vapor injection flash tank and investigated the performance of the heat pump under various condensation temperatures of the refrigeration cycle. In addition to the flash tank, a floodedtype evaporator and a shell-tube oil cooler for refrigeration oil heat recovery are implemented in the heat pump system. Suitable vapor injection pressures corresponding to different condensation temperatures were found. It was also found in this study, that with a suitable vapor injection pressure for operation, the average coefficient of heating performance can be enhanced by the investigated heat pump system under various condensation temperatures. An intelligent controlling strategy in terms of the subcooled degree was developed to attain the dynamic high performance of the heat pump under different condensation temperatures. From the performance measurements, it can be found that the average heating capacity improvement of 29% and the performance enhancement of 11% can be achieved by the two-stage water-towater heat pump by utilizing the controlling strategy to adjust the vapor injection and the oil heat recovery under different condensation temperatures.

Performance Analysis of High-temperature Two-stage Compression Heat Pump with Vapor Injection Dynamic Control

“…They theoretically showed that increasing the vapor injection pressure increases the amount of vapor injection and the subcooling degree of the refrigeration cycle and enhances the performance of the system. Luo and coworkers (19,20) developed an intelligent strategy for controlling the subcooling degree by sensing the condensation temperature and subcooled refrigerant temperature at the inlet of the expansion valve to dynamically obtain high performance of a heat pump at different condensation temperatures.…”