Trial Production of a Simple Expander-Compressor Type Heat Pump

点击翻译按钮获取中文摘要

The purpose of this research is to develop a new expander-compressor type heat pump system incorporated with an inertial type free piston. The system is simply composed of one cylinder, one free piston in it and three pairs of valves at the cylinder ends. The system converts an energy in high pressure working fluid to kinetic energy of the piston, then it is used to compress the low pressure fluid. While the cycle runs, high pressure and low pressure fluids are supplied in the cylinder and medium pressure fluid is exhausted through the right and left valves in turns. The low pressure fluid draws heat out of a room for cooling, or the medium pressure fluid is used for heating. Since this system does not include conversion process form high temperature heat to electricity, it can use energy resources more effectively than conventional power generation system.The theoretical research was conducted using the numerical simulation called the multi node model, then the free piston expander-compressor was manufactured. In the theoretical part, the piston mass, pressure level of suction and exhaust fluid, flow and heat transfer in the cylinder, friction between the piston and the cylinder and properties of the working fluid were examined and the estimated performance coefficient showed this system is sufficient for practical use.In experimental part, the flow resistance of valves and the fluid leakage between rooms divided by the piston were very important. After improvement of them, two operation mode was investigated. In one mode named forced operation the timing of valve operation was externally controlled, while in the other mode named a feedback operation the valve was operated as following a signal from sensors which detected a piston motion. Through the experiment the basic operation characteristics like exhaust pressure, flow rate, piston motion and optimum condition were measured.