Book - School of Science and Technology

Cylinders, indirect cylinders and calorifiers 583C.W.feedH.W. outletCoilsCondenseheaderControlelementC.W.bypassOrificeC.W.feedControlDrain valveFigure 20.23 Angelery hot water generatorSteaminletinstantaneous heater in the normally accepted sense, it is possible in many applications todispense with bulk storage completely, the small volume of hot water retained in the shellbeingadequate to meet an initial demand for a minute or two only. In instances wherebatch or surge loads occur, storage in an `accumulator' may be required but, for variationsin a normal load, the generator draws on surplus boiler capacity rather than storage.Success in operation depends largely upon the performance of the temperature controlvalve, the sensingelement of which is so mounted as to take account of both temperatureand rate of demand.Plate type heatersFor process applications and for use in hotels and similar institutional buildings such ashospitals, where large quantities of hot water at a constant temperature are required, anapplication may exist for a true instantaneous heater such as the plate type equipmentshown in Figure 20.24. The components of this package include the heat exchanger, aprimary circulatingpump, a motorised valve and the pipework interconnections. Thevalve is controlled thermostatically from the secondary side to maintain a constanttemperature output at 60 C with a primary water input at 82 C.ControlunitPrimary4 portmotorisedvalveThermostatHeatexchangerSecondaryPrimarypumpPrimarySecondaryFigure 20.24 Plate type water heater