Design And Simulation Of Two Rolling Piston Expander Replacing Throttle Valve In Reverse Cycle

In conventional reverse cycle, all parts including compressor, heat exchanger and system control etc., have been got a more perfect development. Just throttle part is an exception with many reasons. But what have to see is that the recoverable work is substantial when a expander, in a medium or large refrigeration and heat pump units, has been used to replace the throttle in a conventional reverse cycle. And the key to its prospects and promote its application is to develop a highly efficient expander. To the two rolling piston expander which been used to replace throttle in conventional reverse cycle, through theoretical analysis and numerical calculation, the paper have discussed the design elements of the expander, analysed the phase transition mechanism during its expansion process and the irreversible loss of energy and related simulation.Based on our work group'experience of CO₂ rolling piston expander, this paper have carried out the design of conventional two rolling piston expander which been used to replace throttle, analyzed the corresponding focus in rotor expander of different working refrigerants, given the design basis of the structure size of expander, and discussed the motion discipline of the expander.During the work process of expander of which replace throttle, the recoverable useful energy is mainly the phase transition work in expansion process. Maximize the recovery of this work is the key to improving the efficiency of expander. To this end, the paper have discussed in detail the related phase change mechanism in the work process of expander. What is more important during the phase transition process is the limit of liquid superheat, the formation of the vaporization core and the model of vaporization bubble growth, particularly the formation of the vaporization core is the key to the smoothly run of phase transition. Basing on the existing theoretical research, thesis has been proposed the formation of the vaporization core,as well as, analyzed and summarized the limit of liquid superheat and the growth model of bubble in the case of pure refrigerant.In order to optimize the design of conventional two rolling piston expander which would replace throttle, under the design and analysis of the structure and movement of expander, modeling analysis have been conducted and the analysis of friction and leakage is the main work. The forces between various components have been analysed and a reasonable explanation of the effect related to each force have been given to facilitate understanding. The main leakage channel and leakage model of working fluid was discussed. Then the friction loss model and leakage loss model was established. The results show that the friction loss has a greater impact on the expander efficiency and is key problems to be solved to improve the efficiency of expander.Finally, the realisable testing of expander has been discussed. As the too much trouble when carry out a direct test in large systems, triangular model has been proposed.