Heat transfer study of novel cross vane expander-compressor unit
Chong, Yue Kin
Date of Issue2016-06-01
School of Mechanical and Aerospace Engineering
With the growing concern of global warming, substantial efforts were made to improve energy efficiency and environmental friendliness of refrigeration systems. In 2014, a new type of expander-compressor unit called Cross Vane Expander-Compressor (CVEC) has been invented by Yap et al. . A mathematical model that comprises of geometrical model, thermodynamics model and etc. is developed and simulated to study the working performance of CVEC. However, it is noticed that heat transfer is yet not taken into account of the mathematical model. In this project, a heat transfer model is developed and integrated into the mathematical model of CVEC to study the effect of heat transfer on CVEC performance. The theoretical simulation results shows that a specific suction valve angle of the expander fits only a particular operating condition. Failure to design the suction valve opening angle according to the operating condition would result in under or over-expansion of the expander discharge fluid. Some suggestions are then given to overcome this problem. Moreover, it is found out that the heat transfer rate increases significantly as the thermal conductivity of the expander-compressor unit increases but the COP is not greatly affected. This result suggests that the effects of heat transfer to the performance of CVEC may not be so significant. It is observed that when the operating speed increases, the heat transfer effect becomes less significant but the COP drops significantly. Additionally, it is found out that when the slender ratio increases, the heat transfer effect becomes greater but the COP drops significantly. Lastly, it can be concluded that the effect of slender ratio and operating speed on the performance of CVEC is more significant than that of heat transfer.
Final Year Project (FYP)
Nanyang Technological University