Document Oz75reN6EKdNxodZnD0ELnVQ1

556 CHAPTER 31 ' 1946 Guide parts of the room, or they may be cast into panels to imitate oak or other wood designs. With fiat plate panels it is common practice to use a frame of plaster, wood, metal or composition to allow for expansion. These plates may be heated with either hot water or steam and connected as in an ordinary radiator system. See Figs. 5 and 6. 5. By electric heated metal plates or panels. These plates or panels are either placed in insulated recesses of walls or ceilings or fastened to the construction, as.found desirable. They should not have a surface temperature much above 200 F. Some have a much higher surface temperature but a lower temperature gives a more comfortable condition and is more efficient. ' 6. By electrically heated tapestry mounted on screens and on the wall. For. this purpose the screen is woven with an electric continuous conductor. Such screens are useful to plug in at any position for emergency local heating without taking care of a large room or office. Panel Heating and Radiant Heating 557 heating systems should, in general, be operated continuously since the panels have large thermal capacities. Where panels are heated by high temperature radiation from a heat source directed toward them, this qualification does not apply. * 1. Assume tfie location and the approximate size of the heating panel. Heating panels may be located in ceilings or floors or walls. Ceiling panels have the advantage that their heat emission is not affected by tapestry or furniture and that they can be used, to a limited extent, as cooling panels during the summer months. If used in low rooms, however, they may produce an undesirable heating effect upon the head. Floor panels have the advantage that they can be easily installed and that much of the radiated heat is delivered to the lower portions of the walls; they have the disadvantage that their heat emission is rather uncertain, since it may be affected by rugs, carpets, furniture, machinery, etc. It is best to make the panels as large as practicable; for example, if the floor or ceiling is used as the heating panel, it is best to use the entire floor or the entire ceiling, or both. Heating a room by means of panels is very similar to lighting a room. Heat radiation is exactly like light radiation, except that it has a longer wave length. If a room is lighted Fig. 5. Pillar Type Radiant Heat Panel Fig. 6. Flat Type Panel Installed in Wall. Recess Note. If all of a heating panel is installed at one end of a large room there may be a marked difference between the equivalent temperature on the two sides of the body. It is usually desirable, therefore, that the heat be distributed at different parts of the walls and ceilings so that no uncomfortable effect will be felt from unequal heating. CALCULATION PRINCIPLES Part I--Panel Heating The term panel healings involving both radiatio'n and convection, is applied in this chapter to a system in which the heat is transmitted from pane! surfaces to both air and surrounding surfaces, as is the case under indoor conditions. Panel heating systems for buildings may be designed as illustrated and described in the following design of a panel heating system , for the room shown in Fig* 7. The design is based on continuous heating.- Panel Fig. 7. Room Plan Used forIllustration of Method of Designing a Panel Heating System by means of a large number of small units distributed uniformly over the ceiling, the room is lighted moreuniformly than if it is lighted by means of a-single unit of equal capacity. Similarly, if the entire ceiling is the heating panel, the room is heated more uniformly than if only a fractional part of the ceiling is used as the heating panel. - In the following example, the entire ceiling will be used as the heating Panel. v 2. Select the desired mean temperature of the air in the room. In a panel-heated room, the mean air temperature is a few degrees lower than the mean temperature of the surfaces of the enclosing walls, floor, and ceiling. In a room heated by introduction of warm air or by means of radiators, convectors, or other similar heating appliances, located within the room, the mean temperature of the air'is a few degrees higher than the mean temperature of the surfaces of the enclosing walls, floor, and ceiling. Under ordinary conditions, in a panel-heated room, the mean tem perature of the air ranges from approximately 65 F to 72 F. In the following example, 68 F is selected as the mean air temperature. 3. Determine as accurately as practicable, the mean temperature of the inside surfaces of the enclosing walls, floor, and ceiling. '. The two inside walls are assumed to separate rooms, which are filled with 68 F air, so that both surfaces of each wall are in close contact with 68-F air. ' The surface tern-