Experimental study of water vaporization occurring inside the channel of a smooth-plate type heat exchanger connected to an adsorber and comparison with trends observed in absorption configuration

Due to the lack of knowledge about water behavior in conditions that might occur in sorption chillers using water as refrigerant, designing compact heat exchangers remains mainly empirical. The objective of this paper is to gain further understanding of phenomena occurring in compact plate-type evaporator in order to be able to design them properly. In that goal, experiments were conducted under various operating conditions during adsorption cycles. Although interactions take place between the adsorber and the evaporator due to coupling phenomena, the present study focuses only on the evaporator. The vaporization of water occurring inside the channel of a smooth plate-type evaporator during these cycles is observed. Two main distinct phenomena observed along the time of the adsorption cycle are identified, described and discussed. Time-averaged cooling capacity and instantaneous cooling capacity for given operating conditions are plotted. A parallel with result obtained with the same experimental apparatus but in absorption configuration (mimicked by a thermosiphon loop) is done. Model developed in absorption configuration is tested. It is shown that, except during the beginning of the cycle, for the major part of running conditions tested, this model is able to well predict the instantaneous cooling capacity obtained during the adsorption cycle as long as the variation of the height of liquid level and the equilibrium pressure is known. The evolution of the cooling capacity measured in adsorption configuration with dimensionless number developed in absorption configuration is plotted for comparison. These dimensionless numbers were developed in order to optimize the design of compact evaporator used in sorption chillers. It is shown that the same trend could be observed for the two configurations.