Exergetic Performance Assessment of a Ground Source Heat Pump Drying System

Abstract

In evaluating the efficiency of heat pump (HP) systems, the most commonly used measure is the energy (or first law) efficiency, which is modified to a coefficient of performance (COP) for HP systems. However, for indicating the possibilities for thermodynamic improvement, energy analysis is inadequate and exergy analysis is needed. This study presents an exergetic assessment of a ground-source (or geothermal) HP (GSHP) drying system. This system was designed, constructed and tested in the Solar Energy Institute of Ege University, Izmir, Turkey. The exergy destructions in each of the components of the overall system are determined for average values of experimentally measured parameters. Exergy efficiencies of the system components are determined to assess their performances and to elucidate potentials for improvement. COP values for the GSHP unit, and overall GSHP drying system are found to range between 1.63-2.88 and 1.45-2.65, respectively, while corresponding exergy efficiency values on a product/fuel basis are found to be 21.1 and 15.5% at a dead state temperature of 27oC, respectively. Specific moisture extraction rate (SMER) on the system basis is obtained to be 0.122 kg/kWh.