Experimental validation of constant efficiency models for the subsystems of an unconventional desiccant-based Air Handling Unit and investigation of its performance

Desiccant-based Air Handling Units, thermally activated by solar collectors or cogenerators, are without any doubt an interesting alternative for solving problems of electrical over-consumption in traditional vapour compression air conditioning. In this paper, theoretical existing models for the operation of the main subsystems of a desiccant air-conditioning system are experimentally calibrated and validated through a wide number of measurements in the typical summer operating range for these systems. The operation of each subsystem is described by a specific efficiency factor. In particular, the validity of the assumption for efficiency factors presenting constant values is experimentally investigated. For each subsystem, the average value of the selected efficiency factor is calculated. The values of standard deviations are rather low (lower than 0.092), suggesting that the constant efficiency hypothesis is reasonable within the range of operating conditions investigated. The validity of the assumed models has been confirmed by the evaluation of the Root Mean Standard Error (RMSE), that compares experimental and simulated values for each subsystem. RMSE lower than 1.3 degrees C and 0.30 g/kg, respectively for temperature and humidity ratio, has been calculated. The desiccant wheel model has been used to evaluate its performance, e.g. in terms of Moisture Removal Capacity (ranging from 2.6 to 4.8 kg/h). Finally, a model of the whole system has been developed to estimate its performance, e.g. the Coefficient of Performance (ranging from 0.50 to 0.92). The results obtained with the experimentally validated models are in good agreement with the scientific literature. (C) 2011 Elsevier Ltd. All rights reserved.