Determination of thermal performance of hydronic radiant panel heaters for different fluid flow rates, fluid inlet temperatures and room temperatures

An experimental study of a commercially manufactured ceiling type hydronic radiant heating system has been performed in a test room, under controlled temperature conditions. One of the goals was to investigate how the radiant heater, under various operating conditions, affects the temperature distribution inside an occupied room. Another goal was to study the thermal performance of the radiant heating panel for different fluid inlet temperatures, fluid mass flow rates and test room temperatures. In addition, the temperature distribution on top of a surface placed below the heater, representing an actual application, was investigated. From the relevant literature, it was concluded that insufficient knowledge exists about these characteristics. The working fluid was water, and fluid inlet temperatures between 45 °C and 85 °C and mass flow rates of 97 kg/h and 174 kg/h were analyzed. The results showed that an almost linear increase in heat output arises, with the increase in the inlet water temperature. For lower inlet temperatures the heat output is moderately higher for a mass flow rate of m˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\dot{\text{m}}}$$\end{document} = 97 kg/h. The fraction of radiation heat transfer to the total heat transfer increases with decreasing water inlet temperature. It was also observed that, a relatively uniform temperature distribution could be obtained on the plate below the radiant panel. Furthermore, lower vertical temperature differences can be obtained inside the test room, for low water inlet temperature conditions. The obtained results of this study, could give information to manufacturers and building engineers, on the appropriate use and regulation of hydronic radiant systems.