Runaround coils as a way to improve the efficiency of heat pumps for the dehumidification of nordic greenhouses

Abstract

Greenhouses generate greenhouse gas from the combustion of fossil fuel for heating and dehumidification. Heat pumps can use electricity generated from renewable to do both, but the heat pump performance might be improved by optimizing the cycle for the specific requirements of a greenhouse. In this work, runaround coils are added to a single-speed R-134a heat pump. A Dymola heat pump example model is used with the addition of an air cycle and additional water coils. Results demonstrated that runaround coils are an efficient way to increase simultaneously and significantly the heating Coefficient of Performance, the condensate flowrate and the exergy efficiency of the system, by 8.5%, 16.3% and 13.1%, respectively, for interior conditions typical of Nordic greenhouses.