porcelain with trim strips of polished metal. Fig. 190 shows the interior of the same cabinet. Other models are made with hardwood exteriors in various finishes. The lining is of the one-piece porcelain type. Cabinets are also made with white enamel linings. Corkboard is used to insulate the walls and doors. <Callout type="important" title="Important">Proper insulation ensures consistent temperature control.</Callout> 352 HOUSEHOLD REFRIGERATION Fig. 191 is one of the refrigerators designed for mechanical refrigeration units. This cabinet has a white porcelain interior lining with an exterior case of steel, white lacquer finished. It is cork insulated. The equipment includes hanger bolts and pipe opening in the rear. The different models include side and top icers, grocery and meat refrigerators of ice capacities from 50 to 575 pounds. YX,G. 189— RHINELANDER REFRIGERATOR. HOUSEHOLD REFRIGERATORS 353 FIG. 190.— INTEKIOK OF REFRIGERATOR SHOWN ON OPPOSITE PAGI 354 HOUSEHOLD REFRIGERATION I'lG. 191.— KHINPXAXDEK KEFRKIERATOH DESIGNED FOR MECHANICAL UNIT. HOUSEHOLD REFRIGERATORS 355 Seeger Refrigerator.— Fig. 192 shows a typical refrigerator made by the Seeger Refrigerator Company of Saint Paul, Minnesota, for electrical refrigeration. The exterior and interior are of white porcelain on steel. They are equipped with porcelain defrosting pan and insu- FIG. 192.— SEEGER REFRIGER.^TOR FOR MECHANICAL, UNIT. lated removable porcelain baffle wall. The insulating material used is corkboard. Vegetable storage compartments can be supplied for all models. These are shipped as separate units complete with fittings. The >-egetable storage compartment opens forward like a flour bin. 356 HOUSEHOLD REFRIGERATION The insulation consists of waterproof insulating paper, heavy insulating board and pure sheet corkboard, hydrolene sealed. 2 inches or more in thickness. White Frost. — Fig. 193 shows one of the White Frost re- frigerators manufactured by the Home Products Corporation, Jackson, Michigan, who have been building them for twenty- five vears. FIG. 193.— WHITE FROST REFRIGERATOR. HOUSEHOLD REFRIGERATORS 357 It is built of special rust-resisting steel and insulated with pure granulated cork in sealed air space. Cork is introduced by a special method to prevent settling. The construction is all steel. The seams and joints arc sealed to be permanently air and moistureproof. This cabinet is round with re
ol
ing food shelves, making entire shelf area accessible for storage. Shelves and ice cham- ber lift out for cleaning. Construction makes it easy to maintain correct refrigera- tion temperatures and secure efificicnt circulation of pure, cold, dry air to each part of the food chamber. The illustration shows a water-cooler ty})e. Two sizes are available of 100 and 50-pound ice capacit}'. Kach size is furnished with or without water-cooling system. The cab- inets are finished in laccjuer or white or grey enamel. Wall Construction. — Fig. 194 shows a refrigerator wall using mineral wool insulation and a metal lining. The nir 1(1 m W ' Metal Lmme. Wood. Rosin 5ized Paper. Mineral Wool. Paper, Air SPAC&. Wood Outer Cas^. FIG. 194.— TYPICAL REFRKrER. or WALL COXSTRUCTIOX space is placed well out from the inside lining. With u^ual service conditions, the air space in this position would be effective as a heat insulator. Fig. 195 shows another wall using mineral wool and air spaces. The air spaces are placed near the inside lining. Water vapor in the dead air spaces would condense, collecting on the surface of the lining. This design is ver" poor from an insulation standpoint. 358 HOUSEHOLD REFRIGERATION Fig. 196 shows a solid wall insulated with corkboard. The inside wooden frame strengthens the cabinet and prevents breaking the opal glass lining in shipment. The wooden frame Wood Case. fZ f- Insulating Paper. ll iiiilllll
s?c Mineral Wool ^ — Insulating Paper. Wood. in Insulating Paper. Dead Air Space. Insulating Paper. ' Dead Air Space. - — ___ Porcelain Lining FIG. 195.— TYPICAL REFRIGERATOR WALL CONSTRUCTION also provides a place for the screws necessary to hold the lining in place. This construction is used on some of the best quality cabinets. Fig. 197 shows a wall construction used for a cabinet with a composition lining. The lining must be well supported to '\V%^ ft
In. Wood. WATERPRoor Paper. Corkboard. Waterproof Papelr. Wood. I N SULATING FELT. Opal Glass, FIG 196.— TYPICAL REFRIGERATOR WALL CONSTRUCTION prevent breakage in shipment. This type lining because of its large heat holding capacity, tends to keep the food com- partment temperature uniform. Fig. 198 shows a wall using fiber board insulation. This type cabinet is easily assembled at the expense of being poorly insulated. The dead air space near the lining would condense HOUSEHOLD REFRIGERATORS 359 ^U CpMP05mON_J_iNiN^. Wood. FIG. 197.~TYP]CAL REFRIGERATOR WALL CONSTRUCTION Wood Sheathing. Waterproof Paper. JVoolFelt Paper. Air Space:. Vegetable Fibre. FIG, 198,— TYPICAL REFRIGERATOR WALL CONSTRUCTION 360 HOUSEHOLD REFRIGERATION water vapor which would, in time, wet the insulation, thus lowering its efficiency. The solid wooden corners produce large heat losses by conduction from the outside case to the lining. Linings. — The lining is a very important part of the house- hold refrigerator. It represents from 10 to 25 per cent of the total cost of the refrigerator. The lining material should have a smooth, hard, and pref- erably white surface. The surface should be stain and acid- proof and must not chip, crack, discolor, peel or craze. The surface should be such that dirt or grease will not adhere to it. The material itself should be free from joints and cracks, non-porous and should not absorb moisture or odors. It is also desirable to have a material suitable for making rounded corners. Following is a list of the different linings in common use in refrigerator construction : Baked white porcelain on sheet iron. Solid porcelain. Solid stone. White opal glass. Galvanized iron. Enamel on steel. Wood spruce, oak,
. Ceramic tile (floor). Rust resisting meta!. Cement. Porcelain on Iron Lining. — The standard lining for refrig- erators is porcelain on iron. The sheet iron for the base is carefull}- selected, otherwise blisters may result. The sheet is cut. punched, and formed. The necessary welding is per- formed. It is then treated with acid to remove all grease and dirt. Sometimes other "pickling" baths are used. The lining is then dipped into a bath of blue porcelain. This porcelain composition usually consists of feldspar, borax, china clay, and other chemicals, in accordance with carefully prepared and tested formulas. These materials are fused or melted in a smelting furnace. The melted mass is drawn off into a tank partly filled with HOUSEHOLD REFRIGERATORS 361 water. When it comes in contact with the water, it is in- stantly cooled and broken into small pieces of porcelain grit. This is placed in a revolving mill and ground as fine as flour. When taken from the mill it is thinned to cream-like consist- ency, and then taken to the dipping room where it is poured into metal vats. The steel linings are first dipped into dark blue liquid, both inside and outside being covered with this first coat. This blue coat renders the surface impervious to rust and disintegration. After the linings are dipped they are placed in drying chambers of high temperature where they remain for several hours to remove the moisture. If the moisture is not re- mioved, the coating would run off when the lining is placed in the furnace. After drying, these linings are placed on compressed air machinery in front of the furnace. The operator, who is forced by the intense heat to stand some distance from the furnace, by means of compressed air levers, raises the furnace doors and sends the linings forward in the furnace, where the porcelain is melted and fused onto the steel at a temperature of about 2000° F. Two more coats of white porcelain are usually applied to the interior of the lining, the second being dried and melted on as ?bove described before the third is applied. This type lining gWes a very good surface which fulfills most of all the various requirements. The surfaces, however, are not flat, as the baking process causes the metal to expand and warp. Considerable difficulty is experienced by the porce- lain cracking at corners and welded joints. Solid Porcelain Linings. — Solid porcelain linings are used in some of the better grade refrigerators. They are very heavy and require a solidly constructed cabinet to prevent breaking the lining in shipment. Most of the refrigerators using solid porcelain linings have an extra frame work of wood to make a rigid construction necessary with this type of lining. The walls are more than one inch thick. The manufacture of solid porcelain linings is an art to which modern machinery has given very little assistance. The 362 HOUSEHOLD REFRIGERATION clay is very carefully selected and is molded by hand in a form. These are placed in drying rooms for weeks where the temperature is gradually increased. The enamel is then ap- plied with a brush ; many coats are required with a period for drying between each coat, then several coats of glaze are applied. The linings are placed in the kiln and each one must be completely enclosed with fire brick. The baking lasts for about one week and a temperature of 2500° F. is reached. This entire process requires several months, so that this type lining is expensive to make, and is not well suited to quantity production. The solid porcelain lining has a rather large heat storage capacity and the temperature in the food compartment will not change quickly wdth an increase or decrease in the amount of ice. These linings have an irregular surface on the insula- tion side so that it is necessary to apply a loose insulating material to fill up these irregularities. White Opal Glass. — White opal glass lining has extensive use in refrigerators. The usual construction is to use the white opal glass lining on the sides, ceiling and doors. It is not suitable for the floor. A'itreous tile is usually used for lining the floors as it stands the rather severe service much better. Opal glass in common use is /« inch or ^% inch thick. This type of lining presents a flat surface on both sides and this lessens insulation troubles. The corners and joints are usually covered with strips of metal. Other manufacturers use cement and in some cases wooden strips are used to cover the joints. White opal glass is used to line the doors in cabinets having solid porcelain linings. Galvanized Iron.— Galvanized iron is not used to any great extent for linings except on a few of the cheaper boxes. It has been found that this material does not resist corrosion and rust as well as the other linings. Some manufacturers use galvanized iron for lining the ice compartments ; however, it is losing favor even for this service. Wood Linings. — Wood linings are being used more ex- tensively even on some high-grade cabinets. An odorless HOUSEHOLD REFRIGERATORS 363 wood is used. The surface keeps dry. The wood lining must be carefully made to avoid crevices between the boards. Some manufacturers use a white enamel paint over the wood, while others use varnish. General Considerations. — The one-piece porcelain or steel lining is gradually losing favor with the refrigerator manu- facturers. This is probably due to the difficulty of making and handling these linings. When the porcelain coating cracks or chips at corners it cannot be repaired satisfactorily. An additional disadvantage is experienced in assembling cabinets with the single-piece lining. The insulation and outer walls of the cabinet must be built around the lining. Sheet porcelain is now being used extensively for lining cabinets. Metal strips are used to hold the sheets in place and to seal around the corners. With this method of con- struction, it is possible to make the various cabinet walls on benches in quantities. The final assembly of the cabinet is then a simple process, requiring very little labor. This method of construction is preferable for quantity production. Outer Case Construction. — The outer wall of most refrig- erators is of wood. The best wood for this purpose is ash. Oak, fir, spruce, and pine are also used to some extent. Most manufacturers use a panel wood construction for the outer case. These panels have a clearance at the edges great enough to allow for expansion and contraction, due to tem- perature and humidity changes. A careful study of these panels in service will show that they actually expand or con- tract, frequently breaking the paint or finish around the edge of the panel. Some advantages of panel construction are : 1. Constructed of short pieces of light boards reducing waste lumber. 2. Less weight. 3. Heavy wall at corners where it is needed for structural strength. 4. Panels properly proportioned give an attractive appearance. 5. Reduces warping troubles. 364 HOUSEHOLD REFRIGERATION Some of the more expensive cabinets use a veneer panel which it is claimed eliminates warping. Metal outer cases are used, such as porcelain enamel on steel, baked white enamel on steel, sheet steel zinc plated with a white baked enamel surface, white opal glass and monel metal. Some troubles are experienced with the metal boxes in joining the lining with the outer case at the doors. There is usually a large heat loss here, and trouble with the moisture collecting on the outer metal case around the doors. Sheet steel is being used extensively for the outer case, the usual finish is white duco enamel. Doors. — ^The door construction is a very important part of refrigerator design. The frame for the door and the door opening is usually of wood several inches thick. This double wooden frame has a poor heat insulating property, which is less than half that of corkboard. Figs. 199, 200, 201, and 202 shew methods of refrigerator door construction in common use. Wood. Door. FIG. 199.— TYPICAL REFRIGERATOR WALL AND DOOR CONSTRUCTION The insulation is usually less on the front of a refrigerator than on any other side. This has been determined by tests using thermo-couples on the outside surface of the cabinet to obtain the surface temperature. Another indication of insuf- HOUSEHOLD REFRIGERATORS 365 ficicnt insulation around the doors is the fact that moisture condenses on these parts first when there is a high room humidity. The door heat loss is especially large when metal is used to line the door frame or the edges of the door itself. There is need for a new material to make the door opening frame and the door frame. Wood does not have sufficient heat Wood. W<kTCgPROOr PikPEg. iNSULWirSS Mw£giM. Jua_SR^c^ —Door.— FIG. 200.— TYPICAL REFRIGERATOR WALL AND DOOR CONSTRUCTION. insulating property. Following are some of the more impor- tant points to be considered in door design : 1. Increased heat loss by conduction through solid or metal framework. 2. Heat loss due to doors not closing tightly causing too rapid ventilation with outside air. This loss is especially large if the door does not fit properly at the top and bottom and varies according to the room or environment humidity, being greater with higher humidity. 3. Damage to the finish and the exterior surface around the doors caused by the condensation of moisture. 4. Warped doors due to constant changes in moisture, tempera- ture and humidity, and the difference in these conditions on the out- side and inside surfaces of the door. 5. Heat loss due to improper design of angle and clearance allowing large air wedge between edge of door and frame. 366 HOUSEHOLD REFRIGERATION The refrigerator door has to stand a severe surface con- dition of humidity and temperature. The humidity frequently attains such conditions as 90 per cent on one side and 40 per cent on the other. The temperature usually has a differential of from 20 to 40 degrees on the outside and inside of the box. Ash is one of the best woods to use for this severe service. Various kinds of gaskets are available for making a tight seal around the door. Some of the materials for this purpose are rubber, felt, rubberized cotton, and thin copper metal strips. The high grade boxes do not depend upon gaskets for a close fit. Most gaskets are afifected by moisture or lose their resiliency after a few months of service. Gaskets are used very efi'ectively on large cold storage doors where it is not practical or necessary to make a good wood-to-wood fit. When a well-made door is fitted properly it will close tightly on all four sides against a strip of ordinary writing paper. Some manufacturers use a series of steps in the door and Wood. vyATERpRoor Paper. Hnsulating Matepial As 1 ' ■ r| Granulated Cork, Air Space. | -i^
! '^Mineral Wool. Corkbqard P-gj I wATERPRoor Paper fWOOD. — Door. — FIG. 201.— TYPICAL REFRIGERATOR WALL AND DOOR CONSTRUCTION. the door frame. The better boxes have only one or two steps and fit well against the outside surface of the box. No at- tempt is made to fit closely between any of the other surfaces. The door-facing strip should have a slope on the side of the door opposite the hinges. This slope is usually applied to HOUSEHOLD REFRIGERATORS 367 the other three sides of the door and door opening, although this is entirely unnecessary except for symmetry. The angle of this slope is easily determined by the radius from the center of the hinge to the inside of the door stop on the opposite side. Wood. Loose Insulating Material Aal Granulated Cork. HiNERAL Wool E''-. Wood. Loose Insulating Material. Solid Porcel/vih. ; '' Composition Lining g., ''' I Wood. '' r Loose Insulating Material . [TIWOOD. Door. FIG. 202.— TYPICAL KEFRIGERATOR WALL AND DOOR CONSTRUCTION. The door construction is one of the most difficult problems encountered in making an all-metal box. Even at a room humidity of 50 or 60 per cent, condensation will probably form around the doors of an all-metal box. This may damage tlic exterior finish of the metal. The door to the ice compartment
Key Takeaways
- Proper insulation is crucial for maintaining consistent temperature control in refrigerators.
- Porcelain lining on iron is a standard but challenging method, while white opal glass and wood linings are more common.
- Wood panels with clearance gaps provide better expansion and contraction management.
Practical Tips
- Use high-quality insulation materials like corkboard to minimize heat loss in the refrigerator walls.
- Ensure that doors fit tightly to prevent moisture condensation and maintain temperature control.
- Regularly check and replace gaskets to maintain a tight seal around the door edges.
Warnings & Risks
- Metal linings can be prone to rust and corrosion, making them less durable over time.
- Improper insulation can lead to significant heat loss, reducing energy efficiency and food preservation effectiveness.
Modern Application
While modern refrigerators have advanced significantly in terms of technology and efficiency, the principles of proper insulation and door sealing remain crucial for maintaining optimal temperature control. Understanding these historical techniques provides valuable insights into the core mechanics of refrigerator operation, which can be applied to troubleshooting and maintenance.
Frequently Asked Questions
Q: What are the main types of linings used in refrigerators according to this chapter?
The main types of linings include porcelain on iron, solid porcelain, white opal glass, galvanized iron, and wood. Each type has its own advantages and disadvantages, such as cost, durability, and heat storage capacity.
Q: Why is proper insulation important in refrigerator construction?
Proper insulation is crucial because it helps maintain consistent temperature control within the