A graphical procedure for desiccant cooling cycle design

The interest in solid desiccant cooling cycles has been continuously increasing, supported by both the ecological soundness and the cost reduction associated with the low grade thermal energy it requires. As a result, many feasibility studies are conducted considering solar energy or waste heat as thermal sources for the desiccant cooling cycles. Such studies often consider pre-set values for the effectiveness of individual components, such as evaporative coolers, heat and desiccant wheels. Although a great number of works have been devoted to desiccant cooling cycle simulation, the diversity of assumptions underlying each mathematical model often makes it difficult to establish an unbiased comparison between independently obtained results. Moreover, many analyses are conducted disregarding important characteristics of the conditioned space, such as the ratio of the sensible and latent loads, or the minimum ventilation flow rate as required by the given number of occupants per hour. Accordingly, the present work proposes a design methodology for desiccant cooling cycles, which can be easily carried out graphically on a psychrometric chart. The procedure is then exemplified to analyze the influence of design parameters, such as the steepness of the condition line, over the applicability of desiccant systems.