NEW DEC OPEN CYCLE FOR AIR CONDITIONING BASED ON FIXED COOLED ADSORPTION BEDS AND WET HEAT EXCHANGERS

Abstract

In this work, a new solar Desiccant Evaporative Cooling (DEC) concept is presented. In the proposed system, two fixed packed desiccant beds of silica gel, operating in a batch process, are used as an alternative solution to the common adsorption rotor for dehumidifying outside air. As well known, adsorption heat due to water condensation considerably reduces the dehumidification capacity of the desiccant material, causing inefficiencies in performance. The aim of the work is to overcome the mentioned intrinsic thermodynamic limit of the adsorption rotor technology. The proposed core component is a fin and tube heat exchanger, commonly used in several air conditioning applications, wherein the spaces between the fins are filled with silica gel grains. Therefore, the adsorption material is cooled through a water loop in connection with a cooling tower. An important feature of the system is the adsorption storage capacity, this is due to the high amount of desiccant material available. An indirect cooling process of the air is then realized by means of two wet evaporative heat exchangers connected in series, with continuous humidification of the secondary side. The thermodynamic cycle is first presented and simulation results are shown and discussed. Possible applications may concern compact roof-top units as well as common AHUs.