Document Q2LeK0o85BKZEoj8QaG8Qxd5

Heating Ventilating Air Conditioning Guide 1939 ENCLOSED RADIATORS The general effect of an enclosure placed about a direct radiator is to restrict the air flow, diminish the radiation and, when properly designed improve the heating effect. Recent investigations7 indicate that in the design of the enclosure three things should be considered: 1. There should be better distribution of the heat below the breathing line level to produce greater heating comfort and lowered ceiling temperatures. 2. The lessened steam consumption may not materially change the radiator heating performance. v 3. The enclosed radiator may inadequately heat the space. 0 K iS A comparison between a bare or exposed radiator (A) and the same radiator with a well-designed enclosure (23), with a poorly-designed enclosure (C), and with a cloth cover (D) will illustrate the relative 'f r." 'Jr f; S( i .'5 i I i Fig. 4. Steam Consumption of Exposed and Concealed Radiators I| i-i ; heating effects. In Fig. 4 the curve (23) reveals that the enclosed radiator } f used less steam than the exposed radiator, but gave a satisfactory heating | | performance. A well-designed shield placed over a radiator gives about \ \ the same heating effect. Curve (C) shows the unsatisfactory, effects ] \ produced by improperly designed enclosures. Curve (D) shows that the i \ effect of a cloth cover extending downward 6 in, from the top of the { j radiator was to make the performance unsatisfactory and inadequate, f , Practically all commercial enclosures and shields for use on direct radiators are equipped with water pans for the purpose of adding moisture to the air in the room. Tests8 show that an average evaporative rate of about 0.235 lb per square foot of water surface per hour may be obtained from such pans, when the radiator is steam hot and the relative humidity f; }i |\ \! j- j 'University of Illinois, Engineering Experiment Station Bulletins Nos. 192 and 223, and Investigation of Heating .Rooms with Direct Steam Radiators Equipped with Enclosures and Shields, by-A.. C. Willard, A.-P.Kratz, M. K.-Fahnestock'and S; Konzo (A.S.H.V.E. Transactions, Vol. 35, 1929, p. 77). University of Illinois, Engineering Experiment Station Bulletin No. 230, p. 20. 274 m 11 Chapter 14. Radiators and Gravity Convectors the room is between 25 and 40 per cent. This source of supply of m ' ture alone is not adequate to maintain a relative humidity above 25 per cent on a zero day. CONVECTORS OR CONCEALED HEATERS Although any standard radiator may be concealed in a cabinet or ther enclosure so that the greater percentage of heat is conveyed to the room by convection thereby resulting in a form of gravity convector, generally better results are obtained with specially designed units which permit a free circulation of a larger volume of air at moderate tempera- Fig. 5. Typical Concealed Convector Using Specially Designed Heating Unit tures. Since air stratifies according to temperature, moderate delivery temperatures at the outlet of the enclosure reduce the temperature dif ferential between the floor and ceiling arid accordingly accomplish the desired heating effect in the living zone. .: Fig. 5 shows a typical built-in convector. The heating element con sisting of a large percentage of fin surface is usually shallow in depth and placed low in the enclosure in order, to produce maximum chimney effect in the enclosure. The air enters the enclosure near the floor line just below the heating element, is moderately heated in passing through the core and delivered to the room through an opening near the .top of en closure. Since the air can only enter the enclosure at the floor line, the cooler air in the room which always lies at this level, is constantly being 275