Room-side and Plenum-side Cooling Prediction of Suspended Radiant Ceiling Panels

Abstract

Hydronic radiant ceiling panels use a chilled surface to cool a room, and their cooling capacity is normally measured in a certified test chamber. However, current measurement standards calculate the cooling capacity of a panel based on the heat carried by the circulating water, which is the sum of the heat extraction from the room and plenum. Thus, sizing the radiant system based on the cooling capacity of the panels may result in an undersized system. In this study, a series of test chamber measurements and field measurements were conducted to quantify and empirically predict the proportion of the heat extracted from the room-side to the total heat extracted by the radiant panel. The cooling capacity of suspended radiant ceiling panels was first measured in a certified test chamber, with the temperature difference between the room and plenum as the main parameter. 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. A simplified, empirical approach for estimating the heat extraction at both sides of the panel was proposed based on the obtained results. A field measurement was then conducted to examine the validity of the proposed methodology. Measurements were conducted in an office building located in Japan, which was equipped with radiant ceiling panels of the same type as the ones tested in the chamber measurements. Heat flux sensors were placed at both the room and plenum sides of a single radiant panel to obtain the proportion of heat extraction from the room-side. The measured room and plenum temperatures were used as input for the prediction of the room-side heat extraction ratio, and the average error of the predicted heat flux was 6%, confirming the validity of the proposed methodology.