CHAPTER XI. TESTING OF ICE REFRIGERATORS. (Part 2)

frost accumulation. As one or more of these variables are always present, test results are subject to numerous interpretations. consequentl' the least possible number of \ariation factors that can be included in a test, the more correct Avill be the analyzed results. If comparative tests are to be run, the factors entering into the results need only be considered and held the same for all tests and the resultant values will give a true comparison. When running a comparatix e test on various makes of equipment and boxes, it is a>sumed that each manufacturer has made each part of his a])paratus as efficient as he knows how, commensurate with cost, consequently the "Performance Factor" test api)ears to be the most logical and at the same time, the mcjst acceptable method of true accomplishment. A comparative method for determining compressor effi- ciency and at the same time, a very simple one, is the so called "Pump* up" test. By using the same receiver on the discharge side of the compressor, and finding the inter'al of time neces- sary to pump a pressure of, say, 75 pounds on the receiver, a quick and comparatively accurate comparison is obtained on compressors of the same bore, stroke and r.p.m. This method can be carried somewhat further and by re- ducing the volume of 75 pounds compressed air to 0 pounds or atmospheric intake pressure, assuming the temperature to remain the same, the volumetric efficiency of the compressor can be found by dividing this volume by the actual piston displacement f(^r the "Pump up" time interval. Another method for obtaining approximate compressor efficiencies, is by means of metering the discharge of air through an air meter for atmospheric intake and varying dis- charge pressures, using compression ratios for conversion into an equivalent amount of refrigerant gas. A suggestion for standard conditions of testing for all makes of household refrigerating equipment would be the TESTING OF ICE REFRIGERATORS 411 power consumption of the motor, where an average tempera- ture of 45° is maintained in the food compartment with 80° average outside air temperature. Another test should be made with an average outside temperature of 100". Earlier Research on Refrigeration in the Home. — Research on refrigeration in the home was carried out by John R. Williams, M. D., to obtain data in order to present a paper before the Third International Congress of Refrigeration, on the subject of "A Study of Refrigeration in the Home and the Efificiency of Household Refrigerators." Dr. Williams has obtained some interesting information in reference to the construction of household refrigerators in actual use, the temperatures prevailing in the rooms and in the refrigerators, the relative amounts of ice used, etc. Dr. Williams' paper was as follow^s : A STUDY OF REFRIGERATION IN THE HOME, AND THE EFFICIENCY OF HOUSEHOLD REFRIGERATORS. The problem of preserving fresh food from decomposition is one which every household is called upon to solve. The cheapest, most efficient, and most available agency for this purpose is refrigeration or storage at low temperature. In the home the pantry, cellar or an ice-box is depended upon to furnish the low temperature required for proper food preservation. There is scientific as well as practical basis for this use of cold. It has been demonstrated by laboratory' experts that bacteria, which are the cause of food decomposition, are markedly retarded in their growth by temperature below 45° F., and that temperatures between 45° and 50° inhibit to a slightly less extent the propagation of these organisms. Above 50° F. bacteria multiply prolifically. This means that foods favorable for the growth of bacteria, as milk, meat, etc., undergo very slight decomposition when kept at temperatures rang- ing below 50° F., but above that temperature they spoil very rapidly It follows, therefore that a box or room for the storage of perishable foods, to be at all efficient, must have a temperature n(jt in excess of 50° F., preferably below 45° F. Even the most favored cities in the United States, in the matter of climate, have periods of from 5 to 7 months when the temperature averages above 50° F. Thus the northern city of Rochester for more than six months of the year has a mean monthly- temperature above 50°, as will be seen by the following tabulation, showing the mean monthly temperature of Rochester, N. Y., from 1872 to 1911, inclusive, for the warm months of the year: 412 HOUSEHOLD REFRIGERATION Degrees F. Degrees F. May 56.7 August 68.9 June 66.2 September 62.8 July 70.9 October 50.0 During these warm months, artificial means must or should be employed to protect fresh foods from decomposition. House tempera- tures, even in the cellar, are rarely much lower than those of the out- side air. The mean temperature for the month of August, 1912, was 68.9°., while the average temperature of 266 cellar bottoms was 63° F. The importance of these facts will be better appreciated when it is understood that nearly half of the homes in Rochester rely upon the cellar for the protection of their perishable foods. In an investigation of more than 5,450 homes, it was discovered that 2,450 families do without ice the year round and depend upon the cellar or pantry to afford the proper temperature conditions for food preservation. Yet in the study of cellar temperatures in several hundred homes not one was found having a temperature below 55° F. Pantries and kitchens were observed to be even warmer, for not one of either was found having a temperature below 60° F. The obvious conclusion from this investigation is that every home should have artificial means of refrigeration. As has just been indicated, about 55 per cent of the homes in Rochester use ice during a part of the year, and most of these homes are provided with some kind of an ice box. The endeavor was made to determine how efficient are these refrigerators, and also to learn with some accuracy to what extent ice is used, its cost, etc. Investi- gation of the problem was undertaken in various sections of the city, each dififering from the others in social or economic conditions. These distinctions are indicated in the accompanying tables. Upwards of 100 homes in each district were studied in the following manner: A trained investigator, equipped with a set of accurate and deli- cate thermometers and other measuring devices, visited the homes and made the observations. Cellar temperatures were taken approxi- mately twelve inches from the cellar bottom; refrigerator tempera- tures were taken in the food chamber. Each temperature observation lasted at least fifteen minutes. In making the test the refrigerator door was opened, the instrument placed inside, and the door closed as quickly as possible. When a box was low in ice, or when condi- tions were discovered which affected the validity of the test, another observation was made on the following day or the questionable data was rejected. In this study of ice boxes, a large number were examined and the data from 300 accepted as trustworthy. Of these, only 123 had tem- peratures below 50° F., the other 177 registered above that tempera- ture and were therefore worthless for preserving food. TESTING OF ICE REFRIGERATORS 413 The main reason for the inefficiency of these refrigerators is to be found in their defective construction and insulation. Most of them are wooden boxes built of half inch lumber, and are lined with tin, galvanized iron, or zinc. The walls vary in thickness from less than two inches to more than four inches. The space between the metal lining and the wooden sides is supposed to contain some insulating material, as felt, mineral wool, vegetable fibre, or some preparation of cork. In many of them nothing more is to be found than a sheet or two of paper. Since the efficiency of a refrigerator depends in large part on the character and thickness of the insulating material, consideration must be given to these factors. It has been proven both experimentally and practically that con- fined air is the best insulator. The property of retarding or resisting the transmission of heat by an insulating agent rests largely in the fact that air is incarcerated within its fibers or cells. The more com- pletely the air is confined, the more efhcient is the insulation. An insulating agent, to be of value, must not permit of the circulation of air, nor must it absorb moisture. Moisture and air currents are fatal enemies to good insulation. A refrigerator wall which contains a space large enough to permit of air circulation, will be found defective because the air then carries the heat by convection. Wood, felt, mineral wool, charcoal, sawdust, etc., are fairly efficient when they are dry, but as soon as they absorb moisture, as most of them do, their efficiency markedly declines. When there is inferior or inade- quate insulation in the wall of the refrigerator, the heat percolates through, warms the air next to the metal lining and thus favors the condensation of moisture on the metal within the wall. The poorer the insulation, the greater is the precipitation of moisture. This damp- ness not only serves to corrode the metal lining, but also becomes the medium for the growth of germs and filth. If the insulation has the property of absorbing moisture, as have most of the cheap insulating agents, this water of condensation is soaked up and the efficienc- of the insulation is correspondingly lowered. Furthermore, this absorbed moisture serves to warp and rot the wood casing, with the result that doors become ill fitting, permitting warm air to leak into the box, still further lowering the efficiency of the refrigerator, besides uselessly melting the ice. Some manufacturers avoid the corrosion of the metal lining by the use of glass, tile, or vitreous enameled metal. The manu- facturers of shoddy boxes are imitating these by coating the cheap metal linings with white paint. Such refrigerators usually have little or no insulation, and are worthless for food protection. The conditions just described were commonly noted in the exam- ination of refrigerators, particularly in the cheap boxes found in the homes of working people. Many w^ere discovered where the door could not be closed tightlv. The eflfect of these evils is evidenced in 414 HOUSEHOLD REFRIGERATION Tables LXXVII and LXXVIII. The average temperature inside of the food chamber in practically all of the cheap boxes was above 50° I-., and the lowest temperatures noted, taken usually soon after icing and under the most favorable conditions, were not low enough to be of dependable value. A properly constructed and operated ice box, with reasonable ice consumption, should constantly maintain a differ- ence of at least 25 degrees between the temperature of the food chamber and that of the outside air when the latter is 70° F. or thereabout. As the outside temperature goes down, this difference will diminish. A box which will not maintain an average difference of more than 20 degrees is not much good, and those with even smaller differences. TABLE LXXVII.— SHOVVIAG TEMPERATURE OF REFRIGERATORS, LINING ROOMS AND CELLLARS DURING MONTH OF AUGUST, 1912. ROCHESTER, N. Y. Refrigerators | Living Rooms | Cellars Section o a c Well-to-do American 29 43 62 4 0 64 61 0 6 78 American laboring 3 17 19 10 0 24 21 0 22 31 Jewish laboring 9 20 47 8 0 28 63 0 0 75 German-American laborincr 1 0 49 2 0 4 18 0 4 29 Italian laboring 01 600 0 700 10 Totals 42 81 153 24 0 120 170 0 32 253 Since the writer undertook to study the problem of home refrig- eration, he has been deluged with inquiries as to the best makes of ice boxes and how it can be determined whether or not a given box is a good one. The answer is neither easy nor simple because the prob- lem deals with the combined complexities of economies and the physics of refrigeration. It seems worth while, however, to discuss simply and briefly the technical questions involved. The amount of money a family can afford to pay for a refriger- ator or for proper insulation depends largely upon the cost of ice. If ice can be procured Tor nothing, then there is little need to pay much to prevent it from wasting. If, however, it is costly, then it will be found economical to pay for good refrigerator construction. The average retail price of ice in Rochester is $8.50 per ton, and this will be used as a basis of calculation in the following discussion. Next in order of importance to the cost of ice, is the cost and efficiency of the insulating agent used in the wall of the box. The purpose of the insulation is to prevent the passage of heat from the outside to TESTING OF ICE REFRIGERATORS 415 the inside of the box. As said before, the chief value of an insulator depends upon the amount of air entrapped within its cellular struc- ture, and upon its freedom from moisture. If an insulator disin- tegrates so as to lose its cellular character or air spaces, its efficiency correspondingly declines. If it becomes wet, its value is almost cut in two. In the study of an ideal refrigerator for the home, two factors must be seriously considered, the cost of ice and the cost and efficiency of insulation. TABLE LXXVIII.— SHOWING THE COMPARATIVE TEMPERATURE OF DIFFERENT MAKES OF REFRIGERATORS IN USE IN ROCHESTER, N. T., AUGUST, 1912. o. o va e« B- ^t.- H « 3 bi Insulation. <u s .5 hoc til Mn hcQ O ^ >. h '" ^3 ^C \y2-\n. mineral wool, I'/^-in- Aax and paper, 3-in. board. 1-in. mineral wool, 3-%-in. boards, ^-in. felt. 1-in. vegetable fiber, 2-^8-in. boards, felt sheathing. U-^-in. board, M-i"- vegetable fiber. Paper, 2-%-in. boards. Paper, air space, ?^-in. boards. Paper, and board. Paper, and board. Air space. Paper, air space. Paper, air space. Paper, air space. Home-made boxes, built-in boxes and those unnamed. Miscellaneous boxes, more than 70 different makes. The average working man who uses a refrigerator spends between $5.00 and $10.00 for the ice he uses during the four or five warm months of the year. See Table LXXIX showing the amount spent for ice by various classes of people. Well-to-do families spend between $15.00 and $40.00 a year for ice. The cost to families in moderate circumstances varies between these extremes. Refrigerators in the homes of working people cost, at retail, between $10.00 and $20.00. In the homes of those in better circum- stances, ice boxes costing from $25.00 to $150.00 are to be found. Most of the low-priced boxes are built more with regard to appear- 39 48.4 70.9 22.5 P.cst 9 46.3 69() 22.7 Best 7 45.5 69.1 23.6 Best 6 47.6 69.7 22.1 Best 7 52.2 69.7 17..^ Medium 13 51.7 70.4 18.7 Medium 13 52.7 72.3 19.6 Medium 11 54.5 73.6 191 Medium 21 53.7 73 1 19.4 Cheap 6 54.9 70.0 15.1 Cheap 8 52.6 73.8 21.2 Cheap 9 52.2 68.9 16.7 Cheap 6 57.0 74.4 17.4 Cheap 7 56.6 71.5 14.9 Cheap 7 50.9 66.5 15.6 Cheap 22 510 71.3 20.3 Mixed 104 53.3 71.3 18. Mixed 416 HOUSEHOLD REFRIGERATION ance than efficiency. The majority of them contain practically no insulation. It is not within the province of this paper, nor has the writer the qualifications which would enable him to intelligently dis- cuss the cost of making refrigerators, but it is within the scope of this discussion to consider the economic value to the consumer of improving the quality of the boxes now in use. TABLE LXXIX.— SHOWING PRICE PAID FOR ICE PER YEAR. DATA FROM 321 FAMILIES. Under $5.00 $10 to $15 to $20.00 Section $5.00 to $10.00 $15.00 $20.00 and ovei Well-to-do 6 36 ZZ 13 34 American laboring 34 16 5 1 4 Jewish laboring 22 72 10 6 1 German-American laboring 8 14 1 1 0 Italian laboring 4 0 0 0 0 Total 74 138 49 21 39 NOTE: By this table it will be seen that working people spend from less than $5.00 to $10.00 or more for ice in the four or five months of the year in which they use it. Those in better circumstances spend correspondingly more. At least 60 per cent of this money is wasted and lost in the inefficient and uneconom- ical refrigerators in use. Were this loss applied to the purchase of a good ice box, these families in a short time would have adequate and economical refrigeration, in pl.ici> of the present wasteful and unsanitary methods. This point can best be illustrated by considering a specific exam- ple. In Table LXXX is shown the relation between the amount of insulation, ice consumption, and cost of operation. The refrigerator is of medium size (42x30x18), of good make, and, as ice boxes go, is well insulated. It retails for about $20.00, more or less, depending upon the trimmings. To be efficient, this box should maintain a fairly constant temperature of 45° F. within the food chamber. To do this, it must maintain an average dif?erence of 20 degrees temperature between the inside and outside of the box. To overcome the heat radiation from a box of this size, and with the kind of insulation within its walls, it would require an ice meltage of approximately 158 pounds per week, or 3,400 for the five warm months. This ice would cost the consumer, at current prices, $14.45. If one inch of high grade insulation were added to the walls (corkboard is used as an illustration and is the basis of calculation), it would reduce the quantity of ice necessary to maintain this tem- perature difference to 90 pounds weekly, or 1,950 pounds for the sum- mer. This would mean a saving of 1,450 pounds in ice and $6.15 in cost of operation. This added insulation