Book - School of Science and Technology

Convective heating 199Figure 7.22 Forced (fan) convector, domestic typesuccess, to study bedrooms in university halls of residence, the fan then being controlledby a time delay switch which isolates supply after, say, a 2-hour running period unlessreset.Unit heatersExcept for individual and special applications, the use of unit heaters for industrialpremises seems to have given way to that of either radiant panels or an induction typehigh temperature plenum arrangement. This change has, no doubt, resulted from arealisation that the alternative methods are more energy economic. The most familiartype of unit heater is as illustrated in Figure 7.23, where the heating medium shown issteam but might equally well be low, medium or high temperature hot water; equipment isalso available as direct oil or gas fired. In addition, downward and horizontal dischargeSteam connectionIsolating valvesCondense mainUnit heaterTrap setFigure 7.23 Suspended type unit heater, recirculating