Radiant Heati
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r Big Garages
How Economies in Fuel of up to 40 per. cent. Can be Achieved by the Use of Radiant Units : A Good System for Buildings of Large Cubic Capacity
By Frank H. Slade, A.M.I.Mech,E. THE chief problem associated with warming garages of the , type used by London Transport and other big operators, where the working space is large and the headroom high, is mainly that of providing equable working conditions without avoidable expenditure of heat. An important factor in space warming is to provide a source of radiant heat.
An area treated in this way becomes a low-temperature >radiating surface from which gentle warmth is directed on to the occupant and contents of the space. Air being practically transparent to Such radiation, it is not appreciably warmed by it, but the human body, building structure and the contents of the working space partly absorb and partly reflect it, the relative degree of absorption and reflection depending largely on the type and texture of the absorbing surface.
The feeling of comfort imparted by , a building warmed by radiant panels is thus largely independent of the.air temperature. Stuffiness is naturally absent, and as the air is not the medium of heat transmission, as in the case of convectors or exposedpipe surfaces, a reasonable amount of air movement for ventilation can be maintained without serious loss of heat. Moreover, as the radiant warmth is partly, absorbed by surrounding objects, the cold-starting of engines is assisted.
Whilst the primary purpose of o4 . radiant panels is to provide comfortable warmth, they also show substantial economies in fuel. The -quantity of heat required to impart individual comfort in a given space is much less if the heat reaches the space by radiation, as against having to raise the air temperature.
Within certain limits, too, air filtration does not reduce comfort and has not to be accounted for in the overall heat supply. These factors, allied with a temperature gradient that never exceeds a maximum of 3° R at different levels in the warmed space, are responsible for savings in fuel assessed at 20-40 per cent, as compared with other methods of warming.
Radiant warming of a garage may be carried out by floor warming, or by the use of Sunzway or Sun strip radiant units. Alternately, Sunzway and Sunstrip radiant units may be incorporated in the same system. Infloor warming, low-temperature heating coils are embedded in the floor over the entire area of the gara space.
In this system, the position of t heating coils calls for careful cafe lation. For instance, the depth of t coils beneath the surface and the d tance between centres has to determined to suit the conditions. areas where it is customary f garage hands to stand, the ternpei ture must not be allowed to exec 70° F.
Slight convection currents wat the lower strata of air and t radiant rays which travel upwar are reflected into the warm space roof lights. If the rest of the ro is of galvanized steel, this also as a heat-ray reflector. It is usual incorporate high-temperature rad; tors at large door openings in ord to counteract local exposure loss'
Sunzway radiant units can advantageously employed in existi, buildings where the installation embedded. panels would be impra ticable.
These units are of steel constru tion and are built in standard siz measuring 8 ft. by 4 ft., and 6 ft. I 3 ft. They are fixed horizontally the, roofby .special brackets, or th. may be arranged. vertically .on. wa or . stanchions.
• If desired, double-sided units m be employedto radiate in opposi .directions to warm a workshop each side of a dividing line: "1 facilitate temperature control, altf nate units may be . connected separate return pipes in which thermostatically controlled valve inserted. •
This valve should preferably I of the magnetic or distant-contr type, the operating thermostat, beit -fiied irk-. the: most',effetive..positk for determining the average ter perature of the section.
In cases where the heating units Ln be more conveniently arranged horizontal runs or at a slight angle orn the horizontal, the Sunstrip stem may be employed. The diant units are fixed at a high level id extend continuously through the agth of the garage or workshop. Two strips are normally found lequate for each bay of a garage, it if the bays are unusually wide,
c Sunstrip may be widened or the .Imber of strips increased. Using gh-pressure hot water as the heatg medium, the surface temperature both Sunzway and Sunstrip units tries from 3000 F. down to about i0° F. using low-pressure hot water. steam be employed, the temperare is proportionate to that of the .turated steam at the operating -essure.
Sunzway and Sunstrip panels, sulated on that side exposed to the are used in the warming system npIoyed at the Norbiton docking trage of the London Transport xecutive. The installation was by ichard Crittall and Co., Ltd.,
Great Portland Street, London, 'A. The work carried out included e space heating of docking areas. ores spaces and workshops, the tingof Ideal radiators in the fices, arid embodying a hot-water ipply by indirect cylinders arranged ir a Secondary floyv at 150° F.
These heating services are maintained by three boilers made by the Brockbouse Heater Co., Ltd. Two of these are of the No. 0W14, self. stoke, automatic gravity-feed type, each rated at 820,000 B.Th.U.s and complete with thermostatic control. These cover all the winter requirements for heating and hot-water services.
The third boiler, a No. BW.8, also of the self-stoke, automatic gravityfeed type and rated , at 224,000 B.Th.U.s, supplies the hot-water services and the heating in the old store during the summer. Circulation of the hot water is by a large and a small pump to cover the respective requirements of winter and summer. These pumps are made by Holden and Brooks, Ltd.
One flow-main supplying hot water to the radiant warming units at a temperature of 180° F. is equipped with a modulating device arranged to adjust the heat supply according to changes in the outside temperature. It is located in the boiler house and is thermostatically controlled.
Maximum operating efficiency throughout the installation is secured by means of automatic controls made and supplied by The Rheostatic Co., Ltd.