Evaporation heat transfer and pressure drop of ammonia in a mixed configuration chevron plate heat exchanger

Ammonia is a naturally occurring environment friendly refrigerant with attractive thermo-physical properties. Experimental investigation of heat transfer and pressure drop during steady state evaporation of ammonia in a commercial plate heat exchanger has been carried out for an un-symmetric 30°/60°chevron plate configuration. Experiments were conducted for saturation temperatures ranging from -25 °C to -2°C. The heat flux was varied between 21 kW m^-2 and 44 kW m^-2. Experimental results show significant effect of saturation temperature, heat flux and exit vapor quality on heat transfer coefficient and pressure drop. Current mixed plate configuration data are compared with previous studies on the same heat exchanger with symmetric plate configurations. This comparison highlighted importance of optimization in selection of the heat exchangers. Correlations for two phase Nusselt number and friction factor for each chevron plate configuration considered are developed. A Nusselt number correlation generalized for a range of chevron angles is also proposed.