Abstract
M.Ing.
The objective of this study is to analytically evaluate the heat transfer and area requirements of a plate heat exchanger, in which the refrigerant exits the heat exchanger as a saturated vapour; a superheated vapour, under variable inlet conditions, through application of the experimental results obtained by Yan and Lin (1999) on the evaporation heat transfer and pressure drop of refrigerant R134a in a plate heat exchanger. Through the analytical evaluation it will firstly be shown that for the instance in which the refrigerant enters the heat exchanger at different inlet qualities and exits the heat exchanger as a saturated vapour that the amount of heat transferred and area requirement reduces as the inlet quality of the refrigerant increases. Secondly, when the refrigerant enters the heat exchanger as a saturated vapour and exits at different values of superheated vapour that the amount of heat transferred from the water to the refrigerant increases as the
amount by which the refrigerant is superheated increases, combined with an increased area requirement in order to realise a certain amount of heat transfer. All evaluations are conducted at fixed mass flow rates. Through comparison of the two evaluations it will be shown that the area requirement in the superheated region is significantly larger than in the evaporation region of the heat exchanger whilst obtaining significantly less heat
transfer.