Experimental investigation on the heat transfer coefficients of radiant heating systems: Wall, ceiling and wall-ceiling integration

In recent years, radiant heating systems have been catching more observation under favor of the advantages in energy saving and thermal comfort. Radiant ceiling systems are preferred over radiant wall systems due to the easier application and less space constraint compared to wall systems. However in cold climates ceiling surface may not be enough to cover all heating loads. In this case radiant wall systems can be integrated to ceiling systems to cover the peak loads. In order to properly address calculation and design issues dealing with these systems, accurate estimation of the heat transfer phenomena is required for various types of applications. This paper evaluates the heat transfer characteristics of the hydronic heated radiant wall and ceiling systems, as well as their integrated configuration. A series of experiments were performed in which the main objective was to evaluate the heat transfer characteristics of the three different radiant panel arrangements. For this purpose, a climatic test chamber was built and values of total, radiant and convective HTCs were obtained and discussed. To calculate the heat transfer coefficients, tests were carried out using different supply water temperatures in the case of each arrangement. The HTCs were calculated by means of the characteristic temperatures. For the heated radiant wall, the approximate average values 8.57, 5.74 and 2.44 W m⁻² K⁻¹ were obtained respectively for the total, radiant and convective HTCs. On the other hand, corresponding values for heated radiant ceiling cases are: 7.28, 5.70 and 0.82 W m⁻² K⁻¹. Additionally for the radiant wall-ceiling integrated cases, HTC values were obtained for the wall and ceiling panels separately. When the wall is integrated to the ceiling, total and radiant HTCs decreased in both ceiling and wall, convective heat transfer coefficient also decreased in wall but increased in ceiling cases.