Improvements to the cooling capacity measurements of suspended radiant ceiling panels to prevent under-sizing

Abstract

The cooling capacity of a radiant panel is usually measured in a certified test chamber and the value obtained is provided by manufacturers for engineers to use for in calculations. However, current measurement standards calculate the cooling capacity of a panel based on the heat carried by the circulating water, which includes the heat extraction from the plenum. Thus, sizing the radiant system based on the cooling capacity of the panels may result in an undersized system. The aim of this study was to quantify the effect of plenum temperature on the room- and plenum-side cooling of suspended radiant ceiling panels, and to develop a method to measure and predict the cooling at both sides of the panel. A cooling capacity measurement methodology with controlled room and plenum temperatures was thus proposed. The present study comprises three parts: 1) a cooling capacity measurement in a test chamber with different temperature differences between the room and plenum; 2) development of an empirical model based on the measurement data to predict the room-side cooling ratio of the panels; 3) validation of the model with dataset obtained in the field. Test chamber results revealed that an increase in the plenum temperature resulted in an increase in the measured cooling capacity but a decrease in the proportion of heat extracted from the room side. Within the tested temperature range (plenum temperature of 24–28 °C, room temperature of 26 °C), the heat extracted from the room side was 77–92% when the panels were insulated and decreased to 46–71% when they were not insulated. An empirical approach for estimating the heat extraction at both sides of the panel was then proposed. The developed model was validated through field measurements in a newly constructed office building equipped with the same panel as the ones from the chamber measurements. The predicted room-side heat extraction had an average error of 6% (with a standard deviation of 3%) compared with the measured value. The measurement and modeling procedure in this study may thus be used by manufacturers to more accurately document the cooling performance of their panels, which will enable engineers to avoid under-sizing of the cooling system.