Condensation heat transfer and pressure drop of NH3 and NH3/H2O within a plate heat exchanger.

Abstract

The heat transfer coefficients (HTCs) of NH3 are higher than of HFCs and hydrocarbons during the condensation within plate heat exchangers (PHEs) mainly due to its favorable transport properties. NH3/H2O has a large temperature glide, and its heat transfer is dependent on mass transfer. Few models have been specifically developed for NH3 and NH3/H2O condensation in PHEs. This paper presents heat transfer and pressure drop experiments for partial condensation. The calculation method for condensation HTCs and frictional pressure drop is introduced. The working fluids are pure NH3 and NH3/H2O with a weight concentration of 96%. For a mass flux of 62 kgm-2s-1, the HTCs of NH3 increase from 10 to 20 kWm-2K-1 with vapor quality. The apparent HTCs of NH3/H2O are significantly lower than NH3 at high vapor qualities because of mass transfer resistance. Condensation pressure level has a slight influence on HTCs and frictional pressure drop.