Book - School of Science and Technology

Combined radiant and convective heating 187But this restriction only serves to re-emphasise the comment made previously to the effectthat this technique should only be adopted for those applications to which it is best suited,circulation spaces in commercial buildings, shopping malls, changing rooms and swimmingpool surrounds, a variety of domestic areas and certain specialised industrial enclosures.Combined radiant and convective heatingA classic paper by Peach* might well have been headed `What's in a name' but in manyrespects the title chosen highlights the dichotomy which is enshrined in the language, toowell established to be denied. The equipment which falls under this heading, althoughdiverse in size shape and pattern, therefore consists very largely of what the publicidentifies as `radiators'.PipeworkThe exception to that bulk inclusion is the earliest form of heat emitting equipment. Boilermanufacturers' catalogues, as recently as 1947, rated equipment in terms of unit emissionfrom `4 inch pipe'! As a form of heating surface, exposed piping is rarely used in currentpractice but, in any system of distribution, main and branch piping running through thespace to be heated will make a contribution. It is but one of the skills of the designer thathe is able to make use of an output which might otherwise be wasted. Two examples willsuffice to illustrate this point: in a factory mains pipework supplying either radiant panelsor unit heaters will, if run below north light glazing, serve a more useful purpose than ifrouted elsewhere; sub-circuit pipe runs to radiators in, say, a school will contribute moreusefully if routed on the surface than if buried in a water-logged trench outside thebuilding.Tables 6.12±6.17 provide extensive data regarding heat emission from both bare andinsulated pipes. It remains only to note that where pipes are exposed in coil formation,vertically one above another, the reduction in emission will be:2 pipes 5% reduction.4 pipes 15% reduction.6 pipes 25% reduction.Cast iron radiatorsThe earliest point source heater which could, however loosely, be called a radiator wasprobably the double close-wound coil of the Perkins system: Billington y notes however thatthe first cast iron sectional radiator was produced in the USA in 1877 and that James Keithtook out the first English patent in 1882. It is a matter for regret that, 100 years later, castiron radiators were no longer manufactured in the British Isles and particularly so since, inEuropean practice, there is a discernible trend, perhaps resultant from an increasing level offailure in other materials, to the use of cast iron. In contrast, a recent Product Profileproduced by BSRIA states that, in 1987, aluminium and cast iron radiators represented lessthan 4% of the total sold in the home market.* Peach, J., `Radiators and other convectors', JIHVE, 1972, 39, 239.y Billington, N. S., `A historical review of the art of heating and ventilating'. JIHVE, 1955, 23, 259.