23 September 2011

RESEARCH ON EXPANDER OF CO2 TRANSCRITICAL WATER-TO-WATER HEAT PUMP


To improve the efficiency of CO2 transcritical heat pump system, the fundamental
measure is using expander to replace throttle. In the present paper, the internal expansion
phase change mechanism of expander has been carried out and the simulation test of the
phase transition in expander and the experimental study of CO2 transcritical water to water
heat pump system with expander have been conducted. The results revealed that a more
reasonable explanation to CO2 expansion phase transition could be obtained with nonequilibrium thermodynamic fluctuation theory. During the process of rapid decompression,
the pressure and temperature of the working medium declined into the concave curve. At the
same time, the mixture of CO2 and lubricating oil were boiling tempestuously, which caused
the obvious bubble growth process. In addition, after analyzing the experimental data, we
found that the system flow rate was increased with the increasing of the rotating speed and
the inlet conditions of expander, and so was the change of expander recover work.