Numerical analysis on the geometrical aspects of novel cross vane expander-compressor unit
Siang, Xuan Yu
Date of Issue2016
School of Mechanical and Aerospace Engineering
In this 21st century, the world is plagued by numerous environmental problems such as ozone depletion and global warming. In search of a green refrigerant, Carbon Dioxide (CO2) was recommended as one of the ideal refrigerants. Unfortunately, as the expansion process experienced high throttling loss in a traditional vapour compression refrigeration system, the CO2 refrigeration system’s performance is inferior to the existing normal refrigeration system. To solve the problem of high throttling loss experienced during the expansion procession, it has been suggested to replace the expansion valve used in the refrigeration system with an expander. Hence, an integrated expander-compressor combined unit, named Cross Vane Expander-Compressor (CVEC) was invented. It was discovered that CVEC was environmentally-friendly. In addition, its simple design and reduced physical size, which have brought more advantages such as space saving. To analyse the effect of varying parameters on the performance of the expander-compressor unit, a parametric study was conducted. The parameters studied are: port dimensions, slender factor, end-face clearance, radial clearance of the expander and radial clearance of the compressor. The performance of the CVEC due to the effects of varying parameters is evaluated using the system’s COP and mechanical efficiency of the CVEC. In general, an increase in port diameter and end-face clearance helps to reduce the mechanical losses of CVEC, therefore resulting in higher mechanical efficiency, while a longer and thinner expander-compressor unit is preferred as this also reduces the mechanical losses of CVEC.
Final Year Project (FYP)
Nanyang Technological University