Experimental investigation of evaporation heat transfer and pressure drop of ammonia in a 30° chevron plate heat exchanger

Ammonia, an environment friendly natural refrigerant with attractive thermo-physical properties is a potential replacement of the synthetic refrigerants with high ozone depletion and global warming potentials. Experimental heat transfer and pressure drop data are obtained for two phase evaporation of ammonia in a commercial plate heat exchanger for symmetric 30°/30° chevron plates. The plate heat exchanger was configured in a single pass U-type counter flow arrangement with liquid ammonia evaporating in upward flow direction and glycol/water solution simulating the heat load in counter flow. Experiments were carried out 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 and exit vapor quality on heat transfer coefficient and pressure drop. Two phase Nusselt number and friction factor correlations are proposed.

► Thermo-hydraulic performance of a 30° chevron plate heat exchanger with ammonia as refrigerant. ► Experiments performed to study heat transfer and pressure drop for ammonia evaporation. ► Saturation temperature and heat flux varied from −25 to −2°C and 21 to 44 kW m−2. ► Empirical correlations for two phase Nusselt number and friction factor are proposed. ► Data compared with published evaporation data of ammonia in plate heat exchangers.