This paper presents the design and heat transfer calculations of a new psychrometric environmental control climate chamber for heat pump and refrigeration systems testing. First, the standards for rating air conditioning and refrigeration systems are used to determine layout and floor area of the chamber. Then, a heat transfer model is developed to estimate the heat gain from the surrounding into the climate control chamber when the interior conditioned space is at temperature below freezing. The model, which was validated with data from the literature, also computes the wall thickness that would prevent water vapor condensation and subsequent accumulation on the outside walls of the facility. The results show that if the interior room temperature is below –20°F (–28.9°C), the thickness of the walls of the chamber ranges between 4 to 5 inches (10.2 to 12.7 cm), depending upon the thermal conductivity of the insulation panels. The outcomes of this paper also suggest that the cooling capacity of the conditioning system should be slightly oversized with respect to the capacity of the testing equipment inside the chamber. The additional capacity compensates for the heat transfer gained from the surrounding to the interior of the chamber, which is driven by the large temperature difference during testing at temperature below –
20°F (–28.9°C).

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