Use of phase change materials in retail display cabinets to reduce the effect of defrosts

Phase change materials (PCMs) have the potential to reduce temperature fluctuations in retail display cabinets. There are several areas where reducing temperature fluctuations may be beneficial, e.g. minimising effects of defrosts and to damp the day/night variation in refrigeration duty. PCMs were placed below the shelves in a closed door multi-deck cabinet with the aim of reducing temperature fluctuations during defrosts. The cabinet was tested in a test room conforming to the EN23953 test standard (climate class 3). The cabinet was tested with and without the PCMs. No measurable effect for the PCMs was found. A finite difference model was used to explain the results and suggest improvements. Predictions showed the problem was due to the limited heat transfer coefficient, surface area and low thermal conductivity of the PCM.