Document XRXaYv2ea4zYZ3KbpjN5r2V8w

638 CHAPTER 60 except for footings a low-cost roof supported by the cooler. This has been found to be an economical way to conserve interior space. A further advantage results from the high degree of engineering skill applied in the design and construc tion of the factory-built which is subject to close inspection of proper materials and vapor-sealing techniques. Sizes The size of the sectional walk-in cooler may be readily expanded in increments of standard wail sections, usually four feet. It has been found that coolers with 17 ft tops can be spanned successfully without posts. Sizes larger than this require top and bottom sections to be made in sections in length, supported on an I-beam in the center of the refrigera tor. The height of the cooler depends on its use, and the type of the evaporator selected. A cooler with gravity coils is usu ally about 10 ft high; a cooler with forced convection coils is usually about 8 ft high. Types Sectional walk-in coolers are made under two main classi fications: normal temperature, 32 to 45 F, And low tempera ture, 15 F and below. These refrigerators can be adapted through proper refrigeration application to store any com modity. Special care must be taken in the field erection of low temperature walk-in coolers to insure tight joints with no vapor Iftfl-kn- Combination low and normal temperature coolers are available. Condensation problems that may arise on par titions between compartments are easily corrected by the application of low-wattage electric heaters. The normal tem perature compartment acts as a vestibule for the low tem perature compartment, and reduces frost build-up in the latter. Normal temperature walk-in coolers are also used in com bination self-service display and storage refrigerators. Usually one wall of the refrigerator is equipped with multi light glass doors and is brilliantly illuminated. Commodities are displayed and dispensed through these doors and stored in tiie remainder of the refrigerator. These combination refrig erators are most commonly used with dairy products, bottle goods, and flowers. At the present tim<> many low tempera ture walk-in refrigerators are being manufactured for display and storage of frozen foods. A recent innovation in walk-in cooler design is a self-service display-dispensing compart ment in one wall, protected by an air curtain, thereby com bining some of the open type display features with the storage advantages of the walk-in cooler. Sectional walk-in coolers are also being adapted for use in laboratories and industrial controlled-condition rooms in which, with proper equipment, high and low temperature and humidity conditions are main tained. Doors Because walk-in coolers usually receive heavy and rough usage, the doors and hardware must be able to stand up under this usage. The hinges should be heavy enough to allow the doors to swing with minimum effort. The fastener on the door must be easily openable from the inside or the outside, and is usually arranged so that it is impossible to lock the door without being able to open it from the inside Increased costs of handling the stored enmnwiit-jpg en courage a greater use of conveyors and trucks. Walk-in coolers constructed with conveyor doors and overhead track doors enable items to be moved from the delivery truck to the 1962 Guide And Data cooler at minimum cost. Solid or glazed reach-in aery*, J; Sy doors, opening onto shelves, tray racks, or meat racks small items more accessible. Sliding or swinging multi-gkjl doors are provided for self-service and display uses. Freezer doors are usually of the overlapping type, with sponge rubber gaskets, and closing on a non-cooducth, door frame. Low-wattage electric heaters around the do^ jambs on low temperature coolers are being employed b* many manufacturers to prevent the accumulation of and ice. Breathers are sometimes installed on the inside of tl* freezer door face to insure the escape of any vapor that might infiltrate the door. Mechanical door openers are available to facilitate the use of power trucks when hftndling food lnda ia and out of the cooler. Insulation Three or four inches of insulation have been generally ac cepted for storage temperatures from 35 to 40 F. For far temperature applications such as frozen food storage, five inches or more of insulation should be used. Proper vapor seal should be provided. See Chapter 22, 1961 Guide As Data Book. Installation of walk-in coolers of the sectional type without insulated floors is being used in some large chain store opera tions. This facilitates trucking into and out of the cooler. This will doubtless increase the refrigeration load on such <w>i*n of the sizes being discussed here--whereas it might not too much difference for a large cold storage warehouse room. The relation of the total floor area to the floor area immedi ately around the walls of the cooler apparently is the de termining factor in this relation. Reliable data for calftiiMfrm of refrigeration loads is not available based on experimental evidence. Heat gain factors varying from 0.045 to 2.0 Btu per (sq ft) (F deg) (hr) have been suggested. Ground temperature is assumed to be the average annual atmospheric temperature. One large storage warehouse has been built ing this method and is reported as successful. The use of this method for bv temperature coolers of the size being HtamiBseH in this chapter is questionable, however, for 35 F and up it is reported as satisfactory. Considerable difficulty h been reported with low-tem perature rooms having imml&t<*I floors built directly on the ground due to moisture in the ground freezing and causing the floor to heave and crack. Research is now under way on this problem. Good drainage, use of piping under the floor with a circulating warm non-freezing liquid, warmed enough to keep the ground above 32 F, has been tried. Electric beaten and tiling laid under the floor through which warm air can be circulated has also been suggested. This problem has been ob served at room temperatures of 15 F and below. It should al ways be considered when designing rooms with floors on the ground and walls below ground. Refrigerating Methods Each cooler installation must be carefully engineered. Air circulation is of prime importance. If gravity circulation s used, cooling units, haffipg and cooling unit decks must be so placed as to assure adequate air movement to or from aH parts of the cooler. The trend in recent years has been for the use of forced-air circulating units, especially for low-eediS coolers. When such units are employed, care must be exercised .to see that air movement is not too rapid and that direct drafts from the cooling unit do not strike stored products n these are subject to dehydration. Plug-in assemblies are ootr available consisting of an evaporator mounted on one side on general Commercial Refrigeration 639 insulated plug and a condensing unit mounted on the `"TitT. ksijdjae. Thins assembly is opluegeged into an opening in the "rfhe cooler. for fixture temperatures of 35 F and above, finned gravity forced-*1, evaporators may be used with low-pressure 01 Soiled temperature and off-cycle defrosting. For fixture ^oeratures below 35 F, plates, finned gravity or forced-air !*?Zorators may be used. These must be designed for low ^perature application with heated drain pans. Applications' jfforted air units must also be made at higher refrigerant jLmeratures t-han those used with gravity circulation. Below provisions for positive defrosting must be also made. With plat* coils, manual scraping, complete shutdowns, or defrost is commonly used to remove frost. Properly forced-air unite are usually defrosted with hot gas, Metric heaters, or water. gnee most low temperature walk-in refrigerators are mwhere an operating engineer is not always present, it is ^-gested that two complete refrigeration systems be used in jjrger low-temperature walk-in coolers, so that if one fails, tbe other will continue to operate, thus preventing a major les of the products stored. Many installations are made where a variety of products are stored in the same refrigerated jpsce. Compromised selections of evaporators and operating conditions will then be required. Bottled beverages and keg beer are usually stored in walk-in equipped with large capacity forced-air coils for quick mKng Since air velocity, direction of circulation and humidity are not factors, forced-air coils blowing directly on tbe bottles or kegs are quite effective. If keg beer, delivered edd, is kept in a cooler, normal heat load requirements are otisfactory unless the turnover is high. However, if bottled beer or other beverages are stored in the cooler, the additional bat of the number of bottles loaded per day must be Frozen food low-temperature walk-in coolers may be equipped with overhead plate-coil banks, plates or coils on tbe side walls, (if the plates and coils are on the side walls only, a circulating fan must be installed in the refrigerator to prevent heavy condensation on the ceiling) or blower coils equipped with water, electric or hot gas defrost. Blower coils ue usually specified at not more than a 10 F temperature dif ferential in order to provide for quick defrost and rapid pull down after defrost. The condensing unit should be specified to have sufficient capacity at these suction pressures. If there b to be a freezing load, this should be added to the heat load of the refrigerator when specifying the cooling unit and con densing unit. If food is to be frozen, contact freezing on plates or by blast from forced-air units, or a combination of the two, produce the best results. Frozen food should never be stored in contact with floors or walls of storage rooms. Allow at least 3 in. from the floors by using floor racks, and 12 in. from the out ride walls, except in *m*H coolers, where not less than 4 in. b recommended. Walk-io coolers are used for many other refrigerated space loquiremente than those outlined here. The nature of the Product to be stored, the range to which the product is to be 'ooled, if product cooling is involved, the moisture conditions required, the size of the cooler, the thickness of insulation and the differential between ambient and interior cooling temf^r^tures are factors in the selection of equipment required. SPECIAL-PURPOSE REFRIGERATORS This title is perhaps a misnomer because any given refrigenclosure which is capable of performing a particular function more suitably than it would a less exacting require ment, belongs in this category, which obviously is much broader than the items to be enumerated here indicate. How ever, the purpose is to invite attention to a variety of adapta tions of the basic principle of the commercial refrigerator as applied in meeting specific needs that are less frequently encountered in the field than, for example, a refrigerated dis play case. It is possible, of course, to cover only some of the more familiar types in this classification. Florist Refrigerators Bascially, a florist is a dealer in flowers and plants. More specifically, the florist is an arranger and designer of floral pieces for various and special occasions. A sale for the retail floral shop may range from a single blossom corsage to an elaborate funeral piece, or from a table decoration for a home to a complete floral setting for a wedding. Flowers are living plants, and after being cut must be refrigerated the game as other perishable items. Experience has taught that flowers keep best at a moderate refrigerated temperature with a high relative humidity. Ferns or foliage used in floral back ground decoration must also be held at a cool temperature. Flowers maturing in the fall and those grown in cooler rlimfttra can stand more cold than others. For the general range of flowers in their refrigerator, most retail florists have found that best results are obtained at temperatures from 40 to 45 F. Many wholesalers operate their storage coolers at 33 to 38 F. Refrigerators for the display and storage of flowers are required by the retail florist while large walk-in storage coolers are required by the wholesale florist. The dis play refrigerator located in the sales area at the front of the shop usually includes a picture window display front, and is provided with one or more display-type access doors, either swinging or sliding. Usually these refrigerators are the step-in type. In the backroom work area of the retail shop, a walk-in cooler is used for storage and to supply make-up. In smaller hnpai a combination of display and storage can be worked out in one refrigerator. Although there are a few floral refrigerator designs con sidered conventional in the trade, the majority are custombuilt to the operator's needs and wishes. The exterior of the refrigerator is usually steel with baked enamel finish, stain less steel or wood. In the latter, the interior, decor of the shop may be continued on the front of refrigerator, so that it be comes a part of the walls of the room. Interiors are usually done in black satin enamel on steel or wood. Display windows end doors are glazed with two- or three-light sealed glass pa-nela. Illumination in display refrigerators is usually ob tained by means of warm white fluorescent tubes to bring out the color-of. the flowers. Colored spotlights are added in some ingtanraa to compliment certain flowers, such as a pink spotlight to enhance the beauty of red roses. To aid preserva tion, florists sometimes use a small motor-driven charcoal air purifier in their refrigerators. In floral cases and coolers, high relative humidity is desir able and, therefore, the refrigeration coil and condensing unit should be selected to accomplish this. Some florists favor a gravity type cooling coil because of low velocity of air cir culation, but many are now choosing forced-air cooling coils which set up a positive but gentle air flow through the re frigerator. Tire forced-air coil has an advantage in the display refrigerator in which the in-and-out service is especially heavy, as it provides quick temperature recovery during these peak local conditions. The refrigeration system for floral refrigerators may be a