Design and simulation of a solar assisted desiccant-based air handling unit

Abstract

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.

Desiccant-based Air Handling Units (AHU) can guarantee significant technical and energy/environmental advantages related to the use of traditional ones (with dehumidification by cooling). For these reasons, a test facility has been located in Benevento (Southern Italy), in which a silica-gel desiccant wheel is inserted in an AHU which treats outside air only. For this wheel, the regeneration temperature can be as low as 65 °C, therefore energy savings and emissions reductions are more consistent when the regeneration of the desiccant material is obtained by means of available low grade thermal energy, such as that from solar collectors or cogenerators. In the actual configuration, regeneration is obtained by means of thermal energy recovered from a micro-cogenerator (MCHP, Micro Combined Heat and Power) based on a natural gas-fired reciprocating internal combustion engine, eventually integrated through a natural gas-fired boiler. Future activity aims to reduce the regeneration fossil energy requirements by introducing a solar collector system that substitutes or integrates thermal energy supplied by the MHCP. To this aim, a commercial software has been used to design the solar collector system (collectors type, absorber area, water flow rate…) considering the thermal power and temperature requirements of the regeneration process. The existing AHU and the designed solar collector system have been successively simulated by means of TRNSYS software, in order to evaluate operational data and performance parameters of the system in a typical week of operation, e.g. thermal-hygrometric conditions of air in the mean sections of the AHU, solar collectors efficiency and solar fraction.