High Efficiency Medium Temperature Display Case

A new generation of high efficiency display cases has recently been marketed by three of the leading U.S. case manufacturers. This new high efficiency display case requires roughly 40% less cooling load compared to a standard medium-temperature open vertical display case (900 Btu/hr/ft vs. 1,448 Btu/hr/ft). A lab evaluation will commence to determine efficiency.

This Emerging Technology project was conducted to quantify and compare the key performance attributes of a new generation of high efficiency medium-temperature open vertical refrigerated display cases. The objective of this laboratory assessment was to determine the power and energy implications of using the latest commercially available energy efficient medium-temperature display cases. The benefits of using these high efficiency display cases was evaluated by measuring key performance parameters such as cooling load, product temperatures, and compressor power and energy requirements. This project evaluated three high efficiency medium-temperature open vertical refrigerated display cases from three leading U.S. display case manufacturers, namely Hill Phoenix, Hussmann, and Tyler. The primary selection criterion was the classification, the similarities in physical characteristics, and the application of these cases. All three acquired display cases were standard high efficiency models without any extra options or features. The tested display case manufacturers and their corresponding product specifications are detailed in this report. A comprehensive monitoring plan was developed to ensure all critical data points were captured. The monitoring involved measuring cooling load, product temperatures, and power and energy usage of end-use components, to name a few. The monitoring also involved measuring and tracking control variables like discharge air temperature, saturated evaporating temperature, and saturated condensing temperature. After data was screened and sanitized, data analysis took place. Data analysis included refrigeration cycle and heat transfer analysis. After the collected data was analyzed, the findings were shared and discussed with the manufacturer representatives. This was an important step in the project to ensure the findings were in line with the manufacturer’s expectations. The results of this study indicated that the total cooling load of the open vertical refrigerated display case with the lowest vertical distance between the discharge and return air grille was 22% lower than the other two display cases. Because the infiltration load contributed to more than 80% of the total cooling load of these cases, the variations in total cooling load was attributed to variations in infiltration load. In fact, the infiltration load of the Hussmann case was 26% lower than the Hill Phoenix case and 12% lower than the Tyler case. Due to a larger surface area of the case walls, the Hill Phoenix case had the highest conduction load (637 Btu/hr) when compared to the Hussmann (551 Btu/hr) and Tyler case (496 Btu/hr). The radiation load, however, remained fairly unchanged around 1,000 Btu/hr for all three display cases. The internal load, which was comprised of heat generated by the case lighting system and evaporator fan motors, was higher for the Hussmann case (730 Btu/hr) when compared to the Hill Phoenix (592 Btu/hr) and Tyler case (476 Btu/hr). This was attributed mainly to an increase in evaporator fan motor power of the Hussmann case prior to initiation of defrosts.