Book - School of Science and Technology

Alternative methods of cooling 407Solid slab systemPipe coils embedded in a floor slab have been used with some success in a number ofinstallations, using well-established technology and taking advantage of the good energytransport characteristics of water as the heat transfer medium. In the present context, it isthe means of cooling the water which is of interest, this being either by a dry air cooler orby a closed circuit water cooler, either of which may be operated at night-time when theoutside air temperature is low. The principles of operation of these cooling devices aredescribed under the heading `Free cooling' on p. 544.Such a system for an office block in Switzerland serves a building of 8000 m 2 floor areawith some 60 km of embedded pipe coils operating in conjunction with roof mounted drycooler heat exchangers. The water temperature between 8 a.m. and 10 a.m. is reported tobe 19 C as is the supply air temperature which is, at most periods of the year, not cooledmechanically. Air delivery to the space is through air handling luminaires which raise thetemperature to 1 or 2 K belowroom level.Cooling by ground coilsPipe coils are used in yet another building in Switzerland but in a very different mannersince they are buried nearby in earth, some 6 m belowthe water table, to provide thermalstorage, seasonally regenerated, for pre-cooling ventilating air in summer and preheatingit in winter. The pipes, which appear to be laid in a parallel grid formation, are of 230 mmdiameter plastic and a total length of approaching 1000 m is buried. It would appear thatthis building is by way of being a research project* and available information regardingperformance is meagre as yet.Local plantCentral plantAll airAir/water/refrigUnitarySingle zoneMultiple zone systemsIn roomthrough wallsplit systemfan coilheat pumpHigh velocityV.A.V.Dual ductDual duct+V.A.V.High velocityInductionV.A.V. + coolingLow velocityAll outside airrecirculationLow velocityTerminal reheatmultizone (hot +cold deck)Low velocityFan coilheat pumpchilled ceilingupward air flowV.R.V.Figure 14.32 Principal characteristics of systems in common use* Baumgartner, Th., ErdwaÈrmenutzung fuÈr die Raumklimatisierung. NEFF-Research Report 390/19922.