Interpolation procedures for the effectiveness method to account for the influence of the inlet airflow states on the desiccant wheels performance

The prediction of the dynamic global behaviour of solid-desiccant air conditioning system continues being a complex task. It is still difficult to get access to a simple model representing with enough accuracy the behaviour of commercialized desiccant wheels.The present work is focussed on the investigation of the feasibility of different interpolation procedures based on the effectiveness concept to predict the influence of the inlet states of the process and regeneration airflows on the pair of independent effectiveness parameters and, consequently, on the global behaviour of a desiccant wheel. The interpolation procedures require a relatively low number of reference operating cases, which can be obtained experimentally, provided directly by the manufacture or derived by validated software.A comprehensive set of airflow inlet states is considered, covering the typical range of inlet states in real operating conditions of dehumidification wheels. The output results of the different version of the interpolation procedure are compared with a set of reference data for desiccant wheels having process–regeneration splits of 50–50% and 67–33%. Moreover, the approach is tested using different number of base points to define the interpolation domains for the process and regeneration inlet air states. The results of this study lead to the conclusion that: (i) the version A with only one operating point in each domain, an approach corresponding to the constant effectiveness assumption, is not recommended if it is to cover the whole range of inlet states considered, (ii) good results are obtained if the interpolation is based only on the four basic points defining each domain; (iii) the best agreement is achieved with versions of type B using 6 points in the regeneration air domain, provided that the two additional points refer to the same air temperature and different moisture contents, (iv) the best option is version B1, requiring only a total of 24 operating cases for the interpolation.The approach can be seen as an easy and quick prediction method of the global behaviour of a real desiccant wheel, suitable to be used in dynamic simulation tools for complete HVAC&R systems like TRNSYS or EnergyPlus.

► Investigation of a simplified simulation method based on the effectiveness concept.
► Influence of the inlet states on the effectiveness parameters.
► Test of different interpolation procedures.
► Good accuracy of the results.