Book - School of Science and Technology

Alternative methods of cooling 405use of mechanical cooling plant. There are three obvious routes to followin pursuit of asolution to the problem of over-heating:. Examination of the source of the problem with intent to reduce heat gains through thestructure and from internal sources such as office equipment and lighting.. Investigation of methods to improve the use and effectiveness of natural ventilation.. Consideration of the use of unorthodox cooling techniques.*Since the first two of these headings have been touched upon in earlier chapters, thefollowing notes relate to remaining items and are to some extent anecdotal.Unorthodox cooling techniquesStrictly speaking, such methods may be categorised as either active or passive, the formerusing some minimum amount of energy and the latter none at all. As might be appreciated,the distinction between the two, in practice, is a matter of degree.Active (or perhaps passive!) cooling may be achieved, but not exclusively, by one or acombination of the following methods:. Night ventilation, coupled with high thermal mass: low temperature night-time air ispassed through the building to cool the structure which, next day, then acts to offsetheat gains. (Unfortunately, in modern office buildings with lightweight partitions, falseceilings and carpeted floors, the mass of the actual structure is degraded thermally to`lightweight' and thus no longer functions well as a store.). Ground cooling, using stable year-round ground temperature, normally 8±12 C, as acooling source for circulated water, air or other transfer media.. Evaporative cooling of air streams: passed through a water spray, the temperature of theair may be reduced by 3±4 K. The quite significant associated increase in humidity maynot be tolerated in summer.To achieve optimum conditions for effective cooling by such means, detailed examinationof the thermal performance of the building fabric and any engineering systemsacting together must be carried out through the whole range of coincident external andinternal conditions within which the building will function. Means for analysis on thisscale are not only available but commonplace.Hollow floor systemA proprietary arrangement, using a combination of night-time ventilation and structuralmass, has been developed in Sweden, supply air being passed through the cores in hollowconcrete floor planks before being introduced into the space. To be most effective, both theceiling soffit and the floor surface should remain `hard' and uncovered in order not to diluteheat transfer by any covering which might act as an insulating layer. The air, supplied atconstant volume to meet the ventilation requirement, is further treated when necessary at aconventional central air handling plant providing filtration and heating or cooling.The planks, each up to 18 m in length and normally about 1.2 m wide, are pre-cast withfive smooth faced cores, 180 mm diameter, per plank. These are modified on site, by coredrilling, to provide holes for air inlet and outlet to cores 2 and 4 and cross passagesbetween these and the central core 3. The end holes are plugged by back-filling with* International Energy Agency. Energy conservation in buildings and community systems. InnovativeCooling Systems. Workshop Report, 1992.