Development of an Adsorption Refrigerator with Regenerative Adsorbent Working at Low Temperature

<p>An adsorption refrigerator is a refrigeration system capable of producing cold water using hot water at a low temperature (between 50 and 80 °C). Because it can utilize solar heat and various types of low-temperature waste heat such as heat generated in production processes and waste heat from fuel cells, great expectations are placed on its effective use. Because an adsorption refrigerator employs two adsorbent-coated heat exchangers that alternatively adsorb and desorb the water, the large fluctuations in the output temperature of the cold water (between 4 and 5 °C) have remained an issue. As a result, directly transferring water produced by the adsorption chiller to air-conditioning heat exchangers or stratified thermal-energy storage tanks requires a buffer tank to be installed in front of it. This additional equipment and space impedes the popularization of adsorption refrigerators.　While typical compression chillers regulate their output by controlling the refrigerant flow rate with an expansion valve and controlling the flow rate of the compressor, no such internal control methods have been established for adsorption refrigerators. In this study, a logical analysis was performed to maintain a constant temperature of the cold water in an adsorption/desorption model by varying the flow rate of the cooling water in the apparatus. The validity of the theoretical formula was confirmed by building a logic circuit to maintain a constant cold-water outlet temperature based on the adsorption isotherm of the adsorbent and the heat transfer within the apparatus as well as by employing experimental values for the stabilized outlet temperature of the water. In addition, it was also confirmed that the experimental values had been substantially optimized. </p>