C. Bongs1*, H.-M. Henning1, A. Morgenstern1

1 Fraunhofer ISE, Dept. Thermal Systems and Buildings, Heidenhofstr. 2, 79110 Freiburg, Germany
* Corresponding Author: constanze. bongs@ise. fraunhofer. de

Abstract

A numerical, dynamic model of a counter-flow parallel plate sorptive heat exchanger was implemented in the modelling language Modelica. Simulation results showing the transient evolution of supply air temperature and humidity ratio are presented. A framework for the 2nd law assessment of sorptive heat exchanger evaluation is presented based on exergy analysis. Simulation results with respect to varying fresh air conditions and regeneration temperature are analyzed under this framework. The exergetic efficiency reaches a maximum at specific fresh air conditions and is highest at low regeneration temperatures. An improved system configuration is finally presented.

Keywords: sorptive heat exchanger, simulation, Modelica, exergy

1 Introduction

A rising demand for active cooling and the need to provide desired rates of ventilation leads to an increase in the energy consumption for air conditioning in buildings. Thermally activated cooling technologies may utilize solar energy as the driving heat source and thus contribute to covering the rising energy demand in buildings via renewable energy sources. The thermally driven desiccant evaporative cooling cycles using desiccant rotors are a well known technology for solar air­conditioning in large applications. A concept of a novel desiccant evaporative cooling cycle for the application in residential buildings and small offices was developed at the Fraunhofer Institute for Solar Energy Systems. In the course of a collaborative research project with partners from industry which is funded by the German Federal Ministry of Economics and Technology a ventilation unit for air dehumidification and cooling will be developed which realizes this novel concept.