A critical review on heat transfer coefficients between heated and cooled horizontal and vertical surfaces and the room

Since radiant heating and cooling systems have become more and more popular, it is crucial to correctly predict their performance in different operating conditions. Currently, different convective heat transfer coefficients between the surfaces (floor, ceiling and walls) and the room are used. Various equations can be found in literature, based on measurement procedures or on detailed calculations, but there is no general agreement on which values should be used. In this paper a critical review on convective heat transfer coefficients is presented and available expressions for calculating these coefficients are listed. A general agreement has been found between plates and three-dimensional enclosure relations, nonetheless convective coefficients resulting from real or simulated rooms should be preferred. Based on literature studies involving measurements in three-dimensional enclosures, an equation has been proposed. For this equation, also the influence of the chosen reference temperature (air temperature or operative temperature) has been considered.