Document 06nN5vvmBarrb47LQVry4GOvk

636 CHAPTER 36 1946 Guide- The standard rating conditions for self-contained unit air conditioners, as given in the code, are set forth in Table 1. The standard rating of a self-contained unit for the conditions specified in Table 1 includes all items which apply to the function of a unit as: (1) name of unit, (2) functions which unit performs, (3) data on cooling, (4) data on heating, (5) data on air flow, and (6) data on humidification. ' The standard rating conditions for unit air conditioners, other than the self-contained type, are identical to those in Table 1 except the entering V wet-bulb temperature for cooling is expressed as 50 per cent relative Vhumidity (66.7 F wet-bulb) instead of 67 F wet-bulb temperature. In addition, the saturated suction refrigerant temperature for comfort cooling is specified at 40 F. This condition is omitted from Table 1 for *. Unit Air Conditioners, Unit Air Coolers, Attic Fans 637 coils, the designer is able to produce a wide range of performances and to offer many desirable features not obtainable with the coil and bunker method. More uniform temperatures, high relative humidity, moderate first cost, and a minimum of installation expense are likewise factors in their development. . New uses have appeared for unit air cooler application in industrial and commercial processes involving both the raw materials and finished product, where the maintenance of low temperatures is a necessary part of these processes. Of particular interest is the new field, of extreme low self-contained units as immaterial in the rating of a unit that includes the evaporator and condensing unit. UNIT AIR COOLERS This type of unit is primarily intended to perform the main function of cooling air, with humidity control a secondary function within the limita tions of the design, The main application of this equipment is in process and product refrigeration such as cold storage warehousing, fruit and vegetable packing, in breweriespand in wholesale and retail food market's; although some comfort cooling may be obtained by' the use of a unit similar in design to this type of unit as previously explained and as illustrated by Fig. 6. '\ 'Application of the unit method of air cooling with mechanical circu lation is comparatively recent, being an improvement over the pipe or finned coil, which depended on gravity for circulation. Bunkers were sometimes constructed around the coils to direct the air flow- and sometimes fans were used for forcing air over the coils. The location of the unit air cooler is usually within the refrigerated area, but the larger, blower type models may be remotely located. Design and Performance Greater application and use of commercial refrigeration have resulted from the'development of the unit air cooler: Flexibility of design has permitted almost any condition to be met. By varying such physical features as the method of introducing the refrigerant into the coils; , the - depth of coil rows and area of their surfaces, and the air volume over the Fig. 9. Surface Type Cooling Unit Fig. 10. Brine.Spray Type .Cooling Unit temperature application where many new uses for refrigeration are being found. Types of Units The two standard types are the suspended or ceiling type, and the vertical or floor mounted type. There are variations of this such as the panel type which is wall mounted and arranged to take in air from the . lower section and discharge it from the upper section. The ceiling type has the appearance of a unit heater, with its propeller type fan blowing air through a bank of coils as shown in Fig. 8. Singly or in combination, they are easily installed and occupy little or no useful space. Alterations may be accomplished with little cost by relocating - units or adding additional ones for increased capacity. The floor mounted types employ blower type fans, as their air deliveries are higher and their locations may be remote from the space to be refrig erated. This type of unit is illustrated by Fig. 9. Air velocities and volumes must be designed for the individual application. This type of unit may employ a pump to spray a eutectic solution over the coils for the purpose of avoiding frosting as shown in Fig, 10.