Exploratory investigation of return air temperature sensor measurement errors in refrigerated display cabinets

Abstract

By introducing doors on refrigerated display cabinets, the energy demand is substantially decreased. However, there exist significant discrepancies in temperature readings between visually identical refrigerated display cabinets equipped with doors. This study explores the cause and consequences of these differences. The exploratory methodology used within the study has used CFD simulations combined with laboratory experiments to conclude that there exists a thermal gradient in the area of the return air temperature sensor causing these discrepancies to occur. Thus, the temperature sensors position within the thermal gradient affects the perceived temperature of the control system and thereby the refrigeration strategy adopted by it. To follow up on the consequences of this observed issue, two field studies were performed to investigate the effects and occurrence of temperature sensors within the thermal gradient. Through this, it was concluded that by moving the return air sensors away from the thermal gradient, the refrigerated display cabinets were performing more uniformly as well as with a reduced heat extraction demand. Additionally, from the field study investigating the occurrence, it was found that 80.5% of the 221 reviewed refrigerated display cabinets had sensors placed in a zone where a thermal gradient exists.