Paper No 424 – Boiling Heat Transfer of Ammonia in a Flooded Evaporator of Adsorption Heat Pumps – 14th IEA Heat Pump Conference, Chicago, USA
Adsorption heat pumps can provide process heat to the industry by converting wasted heat from the plants to more useful heat of high temperature. Ammonia is suitable for a working fluid of the adsorption heat pump for decarbonization since it has zero global warming potential (GWP) and ozone depletion potential (ODP). Thermal performance of the ammonia adsorption heat pump is closely related to the boiling heat transfer in a flooded evaporator of the heat pump. Boiling heat transfer of ammonia on the plain stainless steel tube with an outer diameter of 15.87 mm was investigated at three different saturation pressures of 6.15, 8.57, and 11.7 bar (corresponding saturation temperatures of 10, 20, and 30 ?). Considerable hysteresis between increasing heat flux and decreasing heat flux cases was observed. Measured boiling heat transfer coefficients were compared with previous correlations, and Stephan-Abdelsalam’s correlation showed best agreement with the measurement. Boiling heat transfer on the enhanced tube with low fins was also examined, which exhibited large enhancement of the boiling heat transfer coefficient.