Book - School of Science and Technology

182 Heat emitting equipmentHeated gridalso supportingceiling panelsExpansionloopUnheated gridprovided tosupport panelsonlyCirculating mainsFigure 7.6 Application of metal plate radiant ceilingin contrast, originates from a relatively wide area and may thus operate at ratherlowerfacetemperatures. Such a ceiling will probably combine acoustical treatment witha radiant heat output and, in one proprietary make, consists of thin aluminium pans about600 mm square having regular perforations. The pans are clipped to a piping grid attheir junctions, and support a blanket layer of insulation material spread above them,as in Figure 7.5.It is usual to arrange that the whole surface of the ceiling is so treated; those parts of thecoil which are necessary for heating being supplied with a hot water circulation and theremainder used only as a means of suspension. This aspect is illustrated in Figure 7.6which is a typical application layout serving a number of rooms. The total heat emissionfrom a ceiling of this type, for a mean water temperature of 70 C and a room temperatureof 20 C, would be about 160 W/m 2 downwards and 15 W/m 2 upwards to a heated roomover. Two-thirds of the downward emission would be radiant.Fibrous plaster radiant ceilingsIn this case, an alternative form of suspended ceiling to that described above, a continuouslow or medium temperature hot water pipe coil is supported above and independently ofthe fibrous plaster panels which provide the acoustical treatment and radiant surface, as inFigure 7.7. Above the pipe coil an insulating blanket is supported on wire mesh to containthe heat output. The extent and temperature of the pipe coil determine the level of heatoutput which, in round terms, is similar to that of the metal type described previously.