Analysis of the adsorption cycles with thermal regeneration based on the entropic mean temperatures

A second-law analysis based on the concept of entropic mean temperatures is developed for adsorption cycles with thermal regeneration. In such processes, temperature is never uniform in the adsorber. As a consequence, profiles of entropic mean temperature are also defined in the adsorber, on one hand for the adsorber itself, on the other hand for the flowing heat transfer fluid. Indeed, considering the entropic cycle of the heat transfer fluid as a whole, it appears that this cycle is a combination of a Carnot engine cycle and a Joule heat pump cycle. The Joule heat pump cycle permits more than simple heat recovery, it permits upgrading heat from the adsorber being cooled down to the adsorber being heated up: this is thermal regeneration. The effects of the cycle time and heat transfer fluid flow rate are analysed. The competition between the efficiency of the adsorption cycle, that of the thermal regeneration process and the irreversibilities in the heat transfer is highlighted. The route towards a complete optimization of the process is open. (C) 1997 Elsevier Science Ltd.