US2178020A

US2178020A - Refrigeration

Info

Publication number: US2178020A
Application number: US599239A
Authority: US
Inventors: Andrew A Kucher
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1932-03-16
Filing date: 1932-03-16
Publication date: 1939-10-31
Anticipated expiration: 1956-10-31

Description

A. A. KUCHER Oct. 3l, 1939.

REFRIGERATION Filed March 16, 1932 6 Sheets-Sheet 1 A. A. Kucl-IER Oct. 3l, 1939.

REFRIGERATION Filed March 16, 1932 6 SheetS-Sheet 2 HHH Oct. 31, 1939. A, A KUCHER 2,178,020

REFRIGERATION Filed March 16, 1932 6 Sheets-Sheet 3 A. KUCHER REFRIGERATION Oct. 31, 1939.

Filed March 16I l1932 6 Sheets-Sheet 4 9mm. .3P Sh. Q

\\wh.n m

Oct. 31, 1939. A. A. KUCHER REFnIGEnATmN' Filed March 16, 1932 6 Sheets-Sheet 5 Oct. 3l, 1939. A, A KUCHER 2,178,020

REFRIGERATION Filed March 16, 193'2v e sheets-sheet e Patented Oct. 31, 1939 kUNITED STATES y 2,178,020 REFRIGERATION Andrew A. Kucher, Dayton, Ohio, assg'nor, by mesne assignments, to General Motors Corporation, a corporation of Delaware Application March 16,

10 Claims.

This'invention relates to refrigeration.

It is among the objects of this invention to provide an improved method of, and apparatus for, mechanical refrigeration of household or 5 commercial food preserving cabinets and other objects to be cooled, by which method a substantially uniform cabinet temperature is maintained in a varying environmental or room temperature by a greatly simplified automatic' temperature control and by a refrigerant liquefying unit of materially reduced size and cost.

Heretofore it has been customary to provide household. and other refrigerator cabinets with mechanical refrigerating systems having automatic controls for maintaining desired temperatures in the cabinet. Usually the controls involve an intermittent operation of the refrigerant liquefying unit, and are generally constructed with the view that the best type of control for a modern electric motor, which drives the liquefying unit,is the type which intermittently stops the motor,.and causes, alternately, periods of idleness and periods of operation at full speed.

While such a type of control permits the use of a modern constant speed electric motor for driving the liquefying unit, it also necessitates a liquefying unit of excessive size and cost, capable of compensating for theA loss of heat dissipating powerl in the liquefying unit during periods of idleness, and it also requires control mechanism which is relatively complicated in character and costly to manufacture.

According to this invention, on .the other hand,

I use a constant speed continuously running d liquefying unit driven by an electric motor as a factor in reducing the size and cost of the system. The temperature' control of the cabinet is effected by causing the liquefying unit to ybe operated continuously at a constant speed, and by coordinating the remainder of the refrigerating system with the liquefying unit and with the cabinet in such a manner that a practically constant, or food preserving temperature is maintained in the cabinet regardless of changes in the surrounding or room temperature. In applying my invention to a household or similar` cabif net, the cabinet and therefrigerating capacity of the system are properly coordinated in such av manner that the system removes heat from the cabinet and dissipates it continuously into the surrounding air or other medium substantially as fast and in the same quantity as the heat leaks into the cabinet from the surrounding atmosphere. In the preferred embodiment, a yclosed cycle, compressor-ondenser-evaporator 1932, Seria.l No. 599,239

`refrigerating system is provided in which the compressor, driven by a'constant speed motor, compresses and evaporates refrigerant continuously; and thus removes heat continuously from the evaporator which is cooling the cabinet. The 5 capacity of the evaporator to absorb heat from the interior of the cabinet is modied in proportion with the heat leakage into the cabinet to compensate for changes in the room temperature. Accordingly, the evaporator is made of sucient area to cool the cabinet during the highest room temperatures likely to be encolintered and a refrigerant expanding control is interposed between the evaporator and the condenser capable of varying the quantity of refrigerant supplied to the evaporator, andI thereby varyingv the effective refrigerating area of the evaporator `and its refrigerant temperature so that the evaporator absorbs heat from the cabinet substantially as fast and at the same rate, as the heat leaks into the cabinet.

Wherethe condenser of the system is cooled by the air surrounding the cabinet, or where it is cooled vby some other medium and the condenser pressure still remains a function of the room temperature, I use the condenser pressure as one of several methods of modifying the heat absorbing capacity of the evaporator. To

` this end, I interpose a refrigerant expander or restricter between the condenser and the evaporator, which is responsive,l in part, to condenser pressure and controls the entrance of refrigerant into the evaporator in such a manner that the quantity of refrigerant, the effective refrigerating area, and the refrigerant pressure, and 'therefore temperature, of thel evaporator are correctly proportioned at all times under varying room temperatures to maintain the cabinet temperature substantially constant, or within proper food preservingtemperature limits.

I contemplate many other forms of my inventinembodying one or more of its phases and coming within the scope of the invention; but for a clearer understanding of the principles I describe hereafter, in more detail, the application of its principles to the form which utilizes,` in part, the condenser pressure or ternperature as thefactor for compensating for the varying refrigeration requirements of the cabi-l net. i

Further objects 'and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form 0 f the present invention is clearly shown.

. my invention;

Fig. 5 is another vertical cross-sectional view taken along the line 5-5 of Fig. 4;

Fig. 6 is a topplan view of the evaporator shown in Fig. 4;

Fig. 7 is a cross-sectional View similar to Fig. 5, of a slightly modified form of evaporator;

Fig. 8 is a cross-sectional view of one form of refrigerant expanding device which may be used in connection with my invention; and

Figs. 9 to 11 show charts used in further explanation of my invention.

In applying the principles of this invention to the condenser pressure control form, the heat leakage into a cabinet is coordinated with the refrigerating capacity of a closed cycle, compressor-condenser-evaporator refrigerating. system. The compressor is driven continuously at a constant speed by a constant speed electric motor. The condenser is cooled by air having temperature variations corresponding to those of the air surrounding the cabinet, and preferably the condenser is mounted on the cabinet in a position to be cooled by the air surrounding the cabinet. The evaporator is placed in thermal exchange relation with the interior of the cabinet, such as by placing it inside the cabinet.

The cabinet and the refrigerating system are coordinated by the following steps which will be more fully described after the following brief enumeration:

1. 'I'he heat leak from the surrounding atmosphere into the cabinet is determined and reduced to a working coeiiicient, conveniently, in terms of B. t. u.s per hour per degree 'of temperature difference between the surrounding atmosphere andthe interior of the cabinet.

2. The capacity required of the refrigerating system to maintain the cabinet at a predetermined temperature in an average room temperature is computed from the value found under heading 1, also conveniently in terms of B. t. u.s per hour.

3. The requirements, in B. t. u.s of refrigeration by the cabinet to maintain a constant cabinet temperature at various representative room temperatures is determined from the value obtained in 1.

4. A complete continuously running refriger-` ating system is designed and constructed to produce the capacity found to be required under heading 2.

v5. A-series of calorimeter tests are performed on the system to determine its head pressure, back pressure and refrigeration capacity characteristics under various room temperatures.

6. Charts are drawn from the data obtained above, which indicate the evaporator and condenser pressures required to be maintained by the system at various room temperatures in order to maintain a constant cabinet temperature.

7. A suitable refrigerant expanding' device or restricter, to be placed between the condenserI and evaporator, is designed to maintain the condenser and the evaporator pressures indicated to be necessary by points on the charts made in accordance with heading 6.

The above procedure is now more fully described (1) THE DETERMINATION or THE HEAT LEAK Enom THE SUanoUNnrNo ATMOSPHERE rNTo THE CABINET Any suitable method of determining this factor may be used. According to one method, the cabinet is placed in a relatively low temperature room, such as one at 50 F. Heat is applied to the inside of the cabinet in known quantity, for example, by an electrical heater of known current consumption. Electrical units consumed by the heater are converted into heat units, such as B. t. u.s per hour. The temperature diierence between the inside of the cabinet and the outside room temperature is measured. The total number of B. t. u.s per hour expended in the electric heater is divided by the number of degrees differential between the inside and the outside of the cabinet, and the result is taken as a constant coefficient representing the number of B. t. u.s heat leakage per degree difference between room and cabinet temperature, per hour. Within the normal room temperature range likely to be encountered by the apparatus, it can be assumed that the result thus obtained holds true for any temperautre differential likely to be encountered, although it is to be understood'that under more rigorous 4requirements than those prevailing in the usual household refrigerator cabinet, a more accurate determination of the heat leak into the cabinet may be made.

For the purpose of a concrete illustration, it is assumed that, in a representative cabinet, 3.4 B. t. u.s per degree, per hour of refrigeration are required to maintain the cabinet interior one degree colder than the exterior, this example being an actual value obtained in one ofthe many experiments which I have performed, this particular cabinet having an internal displacement of approximately 5 cu. ft.

(2) CoMPUTATIoN oF CAPACITY REQUmEn oF THE REERIoEaATIoN SYSTEM To MAINTAIN THE CABINET AT PBEDETEEMINED TEMPERATURE AT AN AVERAGE Roon TEMPERATURE amount of refrigeration required'to maintain the f cabinet at the temperature selected (36 F.) in average room temperature is the product of the temperature diierential (-36 F.) Abetween the inside and the outside of the cabinet times the unit heat leak\ per degree per hour obtained under heading 1 (3.4 B. t. u.). From the values above selected, the computation (ao- 36) X3.4=149.6

indicates that refrigeration equivalent to 149.6 B. t. u.s perl hour is necessary to maintain an internal box temperature of 36 F. with a room temperature of 80 F. `This value of 149.6 B. t. u. per hour is made the basis of further design and construction of the refrigeration system.

(3) CoMPU'rArIoN or THE CABINET RErRIeEnA'rIoN REQUIREMENTS Fon VABIoUs RooM TEMPERATURES The requirements of any particular cabinet in order to maintain a substantially constant cabinet interior 'temperature under varying room temperatures are computed from data obtained under heading 1. Since the B. t. u. requirements per degree of interior and exterior temperature differences pez` hour of any particular cabinet can be determined in accordance with the teaching of heading 1, the value thus obtained (3.4 B t. u.s per hour) is multiplied by the total temperature differential between -the constant cabinet temperature and each ofthe varying

room temperatures

60, 70,- 80, 90, 100 and 110. A table to show the proper computation is constructed a as follows:

c= e= a b (a-b) d (cXd) Room Cabinet Temp. Unit v Total temp. temp. dierenheat leak cabinet tial heat leak The above table shows that the particular cabito be maintained with no substantial deviation.

net being investigated requires 81.6 B. t. u.s per hour of refrigeration in order to maintain an internaltemperature of 36 F.'at a 60 room temperature. Likewise it indicates that 115.6 B.- t. u., 149.6 B. t. u., 183.6 B. t. u., 217.6 B. t. u. and

v251.6 B. t. u., of refrigeration are required to maintain this cabinet temperature at room teinperatures, respectively, of 70` F., 80 F., 90 F..

However, it. is to be understood that in the usual household refrigerator, the box temperature can vary or deviate somewhat from any particular temperature so long as the temperature does not drop much below 32 F. or rise much above 50F. for any extended period of time. Therefore, in the design of a refrigeration system, the requirements for household refrigeration do not make it necessary for the box temperature to be maintained without the slightest deviation from the value selected. j

Accordingly it is within the contemplation of this invention that the values under columns b "Cabinet temperature", c Temperature differential and e Total cabinet heat leak may be expressed inA terms of upper and lower limits rather than xed temperatures, and that, in the 'plotting of lines C and D hereinafter described, bands instead of lines are formed on the charts, these bands indicating zones of permissible operation rather than inflexible lines from which no deviation can be made. However, this invention can be, and preferably is, practiced withsuch refinement that box temperatures can be maintained within much narrower temperature limits than above indicated.

(4) THE DESIGN oF A REFRIGERATING SYSTEM To PRODUCE THE REQUIRED AVERAGE CAPACITY WHILE RUNNING CoNTINUoUsLY y A refrigerating system is designed to produce the amount of refrigeration found to be necessary underheading 2 which, for the particular values aumed, was' found to be 149.6 B. t. u.s o1' refrigeration per hour under a room temperature of 80 F. while running continuously at a constant speed. It is deemed unnecessary, under the present development cf the refrigeration art, to describe fully the necessary steps and computations to design such a system. As well known, it is necessary to provide a compressor of proper volumetric capacity when used in v`,combination with a selected refrigerant; condenser and evaporator. Any. refrigeration engineer, u sing known methods and ,values can readily'determine the requirements.

(5) CALORIMETER Tas'rs oN THE SYSTEM A series of calorimeter tests are then performed on the system, in order to determine the refrigeration f capacity at various evaporator pressures and corresponding condenser pressures in variweighing the amount 'of refrigerant'introduced and removed from the receptacle I4. A by-pass line I6 is provided, so that the system may be operated without disturbing the receptacle I4 or its setting. For this purpose, valves I-'|, I8 and I9 are provided. 'I'he discharge from the ref ceptacle I4, or from the by-pass I6, enters an automatic expansion valve.20 which in turn discharges to an evaporator 2| which in turn is connected with an intake of the compressor I0 through the medium of an evaporated refrig erant, line 22. The automatic expansion valve is of the type which automatically maintains a constant pressure within the evaporator and is provided with a suitable manual adjustment, so that it may be set to maintain any desired constant evaporator pressure. Valves of this type are well-known in the art and it is therefore deemed unnecessary to describe them further. The evaporator 2| is provided with any suitable means for applying heat thereto, such 'as a surrounding water tank 23 ingood thermal contact with the evaporator 2|. 'Ihe compressor and condenser are placed in a position with respect to the cabinet 24 substantially identical with the positions which they are to occupy in the finished product. pansion valve of the calorimeter system is displaced, in the finished product, by a different refrigerant expander and evaporator, this in no way altering the results obtained from the tests..

tion is reached in the system. When this stable condition has-been reached, the valve I8 is ma- -4 nipulated so that a quantity of liquidfrefrigerant is introduced into the receptacle I4.

The scales are balanced, and then a balancing weight of arbitrary value is removed from the The heat absorbing element and exscales pan 15a. The valve i1 is then closed and valves i8 and I9 opened with a simultaneous time reading. The system is operated until it withdraws refrigerant from the receptacle I4 until the scales are again balanced, thus indicating that a weight of refrigerant has been used equal to that ofthe weight removed from the scales. A second time reading when the scales are so balanced permits a determination of the length of time during which the system was consuming the known weight of refrigerant from the receptacle I4. A refrigerant whose physical constants are well known is used in the system and thus with the readings above indicated, showing a known weight of refrigerant evaporated in a known period of time, the number of B. t. u.s of refrigeration per unit of time produced by the system is calculated. Careful tests are made'at various evaporator or back pressures, so that the charts hereinafter to be described can be properly plotted. During the calorimeter tests the head, or condenser pressure is read or recorded. The head and back pressure can be read, or recorded for example, by means of the recording gauges 25 and 26. With one of the systems which I have tested, calorimeter tests were performed at various back pressures between 5 inches and 25 inches, mercury column, at each of the 'following room temperatures: 60 F., 70 F., 80 F., 90 F., 100 F. and 110 F.

(6) THE` PLo'rTINc oF Tnt: CHARTS Chart A With the system on calorimeter test, at a back pressure of 20 inches,` and at a room temperature of 80 F. the'system testedby me, using C2ClzF4 as a refrigerant, wasl found to produce substantially 110 B. t. u.s per hour. This determined one point on the 80 F. line to be plotted on Chart `A, the point being. indicated at 30. With the room temperature still at 80 F. and with a back pressure changed to 15 inches vacuum, the system produced substantially 180 B. t. u.s per hour and thus another point, indicated at 3l, of the 80 F. room temperature line of Chart A was determined. With 10 inches vacuum back pressure and still with 80 F. room temperature the system produced 252 B. t. u.s per hour and thus point 32 of the 80 F, room temperature line was determined. With 5 inches vacuum back pressure, with 80 F. room temperature the system produced 325 B. t. u.s per hour and thus point 33 of the 80" F. -room temperature line was established. The lines correspondingto 60 F., 70 F.,'90 F., 100 F. and 110 F. were similarly established, the system being operated at each of these room temperatures withlback pressures of 5, 10, and 20 inches.

Chart B The data.y taken during the testswhich have *y values forrpoint of Chart AY also gave a condenser pressure of. 25 lbs. Thus the point 40 is established on Chart B which forms a part of the 80 F. room temperature line of this chart. Similarly the data which established points 3|, 32

and 33 on Chart A also gave condenser pressures.

respectively of 26.5, 28 and. 29 which established respectively points 4|, 42 and 43 of the 80 F. room temperature line of Chart B. Similar condenser pressure readings at the F., '70 F., 90 F., 100 F. and 110 F. room temperatures furnished the data for establishing the other room temperature lines of Chart B in the same manner as for Chart A. For properly designing a system so that it is capable of producing the resuits of this invention, the head and back pressures which produce a constant box temperature under heading 3, '70 F. room temperature indicates that 115.6 B. t. u.s are required by the cabinet and thus the intersection of the F. line with the vertical line from the 115.6 B. t. u. point establishes the point 5i of the line C. Similarly the computation under heading 3 indicates that the cabinet requires 149.6; 183.6; 217.6 and 251.6 B, t. u.s at F., 90 F., 100 F. and 110 F. room temperatures respectively, and thus the intersections of the 80 F., 90 F., 100 F. and

110 F. lines with the vei'ticals from these B. t. u.

values respectively establish the

points

52, 53. 54 and 55 of the line C. The line C therefore can be used to indicate the various back pressures necessary in the evaporator in order to'maintain a constant box temperature of 36 F. at any varying room temperature between 60 F. and 110 F. by laterally projecting to the evaporator pressure scale the intersections of the line C with each of the room temperatures desired.

The plotting of the line D on Chart B establishes the condenser pressures required under varying room temperatures to establish constant box temperature. The plotting of line D is based on the fact that the construction of the Charts A and B indicates corresponding head and back pressures where a horizontal line intersects corresponding room temperature lines on these two charts. A horizontal line drawn from point 50 on the 60 line of Chart A until it intersects the 60 F. line on Chart B establishes'a point 56 on the 60 F. line of Chart B, which, when projected vertically downward shows the head pressure which is to be maintained in the system at that particular room temperature to produce the required B. t. u.s in order to maintain the box at the constant temperature selected. Similarly a horizontal line drawn from the point 5I on the line 70 F. of Chart A until it intersects the '10 F. line of Chart B establishes point 51 of the line D. In the same manner intersections of horizon# tal lines from the

points

53, 54 and 55 respectively with the- F., 100 F. and 110 F. lines of Chart B establish the

points

58, 59 and 60 of line D which, when projected vertically downward establish the respective head pressures required to maintain the cabinet temperature constant.

The back and head pressure projections from lines C and D as above indicated show the pressures which must be maintained in the evapora- .f

tor and the condenser in order to maintain av constant boxtemperature of 36 F. in room tem lan peratures varying from F. to 110 F.

(7) THE CONSTRUCTION '0F A REFRIGEBANTEXPANDER CAPABLE 0E MAINTAINING THE REQUIRED HEAD AND BACK PaEssUREs 'ro MAINTAIN A CONSTANT Box TEMPERATURE UNDER VARUNG ROOM TEMPERA- TUREs Charts A and B have established a series of head and back pressures which must be maintained in the refrigerating system in order to maintain a constant cabinet temperature at various room temperatures. An expander is therefore made which is capable of maintaining the head and back pressures indicated to be necessary by Charts A and B, which, with this particular system and cabinet, are as follows:v In a 60 F. room, the head pressure should be 15 lbs. as indicated vby projecting point 56 on the 60 F. line vertically downward to the head pressure scale, and the back pressure should be 23 inches as indicated by projecting point 50 on the 60' F. line horizontally to the evaporator or back pressure scale. In a 110 F. room, the head pressure should be 52.5 lbs. as similarly indicated by point 6D, and the back pressure should be 7 inches as similarly indicated by point 55A. When the expander is constructed to'maintain a head pressure of 15 lbs. and a back pressure of 223 inches in a 60 F. room, and a head -pressure of 56.5 lbs. against a back pressure of inches in a 110 F. room, then it automatically maintains substantially the proper head and back pressures forV intermediate room temperature conditions indicated to be required by the charts. Therefore a condition is established in which the cabinet temperature is maintained substantially at 36 F. throughout the range of room temperatures between 60 F. and 110 F.

Various types of restricters are contemplated for use between the condenser and the evaporator which are capable of maintaining the condenser and evaporator pressures herein indicated to be required, and in fact, many expanders now in use, when properly designed and coordinated -in accordance with my invention, are adaptable for use for this purpose. A properly designed elongated orifice having the proper length and crosssectional area, gives excellent results. Preferably the orifice is of triangular cross-section and is designed with such cross-sectional area and length that it maintains the proper head and back pressures in the system to produce a constant cabinet temperature under varying room temperatures. While elongated orices have been previously used to expand refrigerant between the condenser and evaporator, such orifices havek vbeen utterly lacking in characteristics capable f maintaining a constant cabinet temperature in varying room temperatures in combination with a constant speed constantly running compressor. One method of constructing a proper elongated orifice is to place an orifice of any arbitrary length, cross-sectional area and contour in the refrigerating system, all of the parts being in their normal operating position on the cabinet, and then to calibrate the orifice by varying its length and cross-sectional area under various conditions of operation until the calibration produces an orifice of proper length and area' to produce the pressure characteristics which have been previously established: f

The calibration of the elongated orifice, hereafter referred to as restricter, may be performed In either case, after the calibration has been completed, a restricter of definite length 'and cross-sectional area has been established which can be duplicated for quantity production in this finished form.

For the purpose of this invention it is not necessary to give a highly technical description of the laws of flow of an expanding refrigerant through an elongated orifice. On the contrary, only such principles relating to this subject are here described which are necessary to aid a person skilled in the art to properly calibrate an elongated orice to obtain the results required.

With these requirements in view, the following general principles and procedure may be used for calibration of the restricter: During calibration, lengthening the restricter or reducing its cross-sectional area has the effect of lowering the back pressure, and/or decreasing the condenser pressure, whereas'reducing the length or increasing the area of the restricter has a tendency to increase the evaporator or back pressure and/or raise the condenser pressure.

In View of this inherent characteristic, a restricter of a practical initial Alength and crosssectional area is connected in the particular refrigerating system being developed. Calibration begins by changing its length or area o1 both, in any constant room temperature (such as the minimum room temperature likely to be encountered) until it maintains the desired cabinet temperature by maintaining the head and back pressures indicated, in Charts A and B, to be necessary at this room temperature. This calibration, however, is quite likely to be insufiicient to enable the restricter to maintain the same cabinet temperature in the maximum room temperature likely to be encountered, since entirely different head and back pressures are required under this condition. Further calibration is therefore conducted at this high room temperature, and thereafter at alternate low and high roomY temmsctures. Each calibration brings the restricter nearer final form, until the desired result is obtained.

It is necessary i' lr the restricter to maintain proper head and 'tack pressures, and it may be expedient attimes to calibrate the restricter by takinginto account its effect on both head and back pressures. However, under ordinary conditions, calibration can be simplied by using, as a. guide for calibration, only the effect of the orice on the back pressure of the system, permitting the head pressures to adjust themselves automatically to their proper values.

Fig. 9 shows a diagram similar to Chart A of Fig. 1 on which have been placed certain guides for calibration, using the back pressure of the ref frigerating system as the determining factor. In this figure, all points on the area to the left of the line C designate pressure conditions producing warmer cabinet temperatures than those desired. All of the points on the right of the line C designate colder cabinet temperatures. In reading apoint on this chart it must be read with reference not only to the back pressuresV but also with reference to room temperature. Thus the points m and n, being on the same horizontal line indicate identical back pressure conditions (10 inches) in the system; but when these same points are read with reference to the room temperature lines, the point m indicates that a back pressure of 10 inches in a 110 F. room temperature produces a warmer cabinet temperature than is desired, whereas the same'back pressure of l0 inches in a 60 F. room temperature produces a colder temperature than is desired.

The Calibrating rule, as indicated on Fig. 9, is that when a point falls on the left of line C' the cross-sectional area of the restricter is increased, and that when it falls on the right of line C', the restricter length is increased.

With these rules of calibration in mind, a restricter of practical length and cross-sectional area, arbitrarily selected, is placed in the system' and cabinet and is operated in the coldest room temperature (60 F.) likely to be encountered. The result obtained, in terms of back pressure and room temperature is quite likely to be diirerent from the correct requirements of point 50. Instead, the result obtained will occur on the 60F. room temperature line either on the right or left of line C'. For the purpose of a concrete illustration, it is assumed that such a point will fall at the left and can be designated as the point V. In accordance with the Calibrating rule, the cross-sectional area of the orice is increased until the intersection of back pressure room tcmperature ordinates occur at point 50'. However, if the proportions of the restricter are such that an excessive amount of refrigeration occurs within the restricter itself, then ra restricter of less initial length and cross-sectional area should be used as a starting point in calibration.

The initial calibration, described above, satisiies the requirements at the 60 F. room temperature, but is probably not suiilcient to provide/an oriiice capable of maintaining the required back pressure in the 110 F. room. Therefore a second step in calibration is performed in the 110 F. room. The result obtained probably will not coincide with the conditions indicated by the point 55', but may occur at a point either to the right or to the left of point 55 on the 110 F. room temperature line. For the purpose of a concrete illustration, it is assumed that the result can be plotted as the point a: on the left of the point 55 along the 110 F. line. The rule for calibration under this condition is to increase the cross-sectional area until it produces back pressure room temperature conditions substantially the same as those indicated by the point 55. This completes the second step in calibration as indicated in Fig. 9 by the line |02, the point s: and the arrow pointing to 55.

This second step in calibration has distorted the first 60 F. room calibration. -Therefore a third step in calibration is taken. The system is again operated in the 60 F. room and the result observed. The back pressure produced will, under these conditions probably fall to the right .of line C', and' the result can be indicated by the The rule for calibration for resultsl point V'. falling to the right of line C is that the restricter length should be increased. Therefore the length of the orifice is increased until the back pressure room temperature conditions are again substantially equal to the point 50'. This completes the third step in calibration and has been indicated by line |03, point V' and the arrow pointing to 50'.

A fourth step in calibration is performed in the '110 F. room if necessary. The result obtained is plotted on the 110 F. room temperature line and will lie between the point :c and the point 55. Thus it 'may be indicated by the point 3;', and following the rule of calibration, the cross-sectional area is increased until the back pressure, room temperature conditions of point 55' are obtained. This fourth step in calibration is indicated by the line |04, point x' and the arrow pointing to 55.

alternate calibration at high and low room temperatures produces a result nearer in accord with the line C. Thus, if necessary, further steps in calibration may be taken. For instance, a iiith step in calibration includes a chang'efrom the 110 F. room temperature to the 60 F. temperature in which the back pressure obtained in the 60 F. room temperature is represented by the point V intermediate between V and 50. Since point V" falls on the right of line C', the length of the restricter is increased until the back pressure, room temperaturerequirements of point 50 are reestablished. This procedure is indicated by line |05, point V" and the arrow pointing to 50. It will be 'observed that the line |05 very nearly coincides with line C', and that calibration can be continued until results substantially identical with line C are obtained.

THE DRAWINGS The method of refrigeration herein disclosed is applicable to many types of refrigerating apparatus. For a clearer understanding of the invention, and not with the intention of limiting its scope, its application to one particular form, shown in the drawings, is now described. The refrigerating apparatus includes a cabinet `50 provided with the usual food preserving space 50a. A compresser 0, a condenser and an evaporator 5| are mounted on, or unitarily assembled with the cabinet. The compressor discharges refrigerant through the pipe 52 to the condenser where the refrigerant is condensed and is discharged into a receiver 53 which has now been substituted for the receiver I2 used in the calorimeter tests. The condensed refrigerant then passes through the pipe 54 to the evaporator 5|, but before being discharged into said evaporator it passes through a heat interchanger 55 While still under condenser pressure and then through a refrigerant expander or restricter 56. The refrigerant, after having been expanded in the restricter 56, passes through the pipe 51 to the inlet end' of the relatively long,' narrow refrigerant space 5|a of the evaporator 5|. The refrigerant inlet .of the evaporator is placed at the upper end 58 of the arm 58a of the evaporator. The evaporator is in the form of a U and is formed of two

sheet metal plates

59 and 50, the plate 60 having corrugations or dimples 60a formed thereon spaced sufdciently frequently so that the two plates 5S and 60 may be spot-welded together at said dimples to form the refrigerant space 5|a. The refrigerant flows between the

plates

59 and 60 down the arm 58a, around the curved bottom 6|, and' thence up the arm 62. At the top of the arm 62 a semi-cylindrical channel 63 is made in the plate 59', and this forms the outer casing of the interchanger 55 and at the same time' forms the refrigerant outlet of the evaporator 5| to which is connected the pipe 64 leading to the compressor |0. In this structure the effective refrigerating area of the evaporator extends from the inlet 58 at the upper portion of an arm 58a and extends at various distances under lvarying conditions downthe arm 58 minates at some point intermediate inlet 58 and outlet 63 of the evaporator.

In this form an ice cube freezing space is provided by placing

shelves

65 and 66 on lugs 61 and.

68 formed on the plate 59. Since this part of the evaporator is shielded by the top plate69 and end plates 69a and 69h from the circulating air in the food preserving space 50a of the cabinet, this portion of the evaporator is cold enough to freeze ice cubes within a reasonable time. The end plate 69a. is provided with openings 69o for the reception of ice cube freezing trays 69d.

The restricter or expander 56 is of any suitable construction which provides a long orifice through which the refrigerant expands before being delivered to the evaporator. One form which has been found satisfactory includes an outer cylindrical shell 10 placed over a bolt-like cylindrical member 1I which is provided with a triangular thread 12, this thread forming a long continuous passage for the expansion of refrigerant. In one method of assembly, the shell 10 is heated to a relatively high temperature, and is placed over the member 1| so that it contacts tightly in fixed position on said member 16. If desired a screen 13 is placed within the inner cavity 14 of the boltlike member 1I and its end contacts with the boltlike member 1| at the point 15. The other end of lthe screen 13 is secured at the point 16 to the cylindrical member 1 0. The refrigerant from the condenser passing through the pipe 54 enters the restricter or expander at the point 11, passes through the screen 13, and then enters the end 18 of the refrigerant passage formed by the thread 12, finally discharging through the radial passage 19 into the outlet end 80 connected to the pipe 51 which leads to the inlet of the evaporator. The interior of the shell 10 and the exterior of the bolt-like member 1l are preferably chrome-plated and given a smooth nish. In the form shown, the capillary passage formed by the thread 12 is neither adjustable as to length or area.J This form of expander is preferably used in thevnished product after all preliminary calibrations have been terminated. If this type of expander is to be used for calibration purposes several of these expanders are made having different dimensions, so that they may be substituted during calibration until one of the proper length and cross-sectional area is constructed.

If quicker freezing is desired than is provided bythe evaporator shown in Figs. 4 to 6, the modiflcation shown in Fig.7 may be used. In this modification the refrigerant, after having passed through the heat exchanger 80, corresponding to the exchanger 56, passes through the refrigerant restricter or expande;` 8l corresponding to the restricter 56. Thereafter the refrigerant contacts first with the ice freezingmeans by passing through a pipe 82 downwardly and in contact with the bottom of the ice tray shelf 83. The contact is preferably in the form of sinuous loops 82a, the pipe being attached or soldered to the plate 83. Thereafter the refrigerant passes through the portion 84 of the pipe 82 and enters the refrigerant inlet 85, which corresponds to the refrigerant inlet 58 heretofore described. Thereafter the re.

frigerant ows down the arm 86 and continues around thejevaporator substantially in the same manner as'fdescribed with respect to Figs. 4 to 6. The pipe 82 is shown as contacting only lwith the tact with the second or remaining shelves. The shelves 83 are thermally insulated from the outer surface of the evaporator, by being spaced as shown at 88 from the outer shell of the evaporator. Small lugs are used for supporting the shelves, but the lugs are made as small as possible, so as to provide the least possible thermal contact.

The description heretofore made with respect to the proper design of the refrigerating system and the expander, is not altered by the ice freezing means described. The system and the expander are designed as though no ice freezing is to be provided, and the system automatically increases its capacity when the ice trays with water are introduced into theevaporator. When the ice trays are introduced, the back pressure and vhead pressure automatically increase for a short period of time, thus materially increasing the capacity of the system temporarily, and thereafter the pressures tend to restore to the normal conditions. In the cabinet constructed by me, of substantially 5 cu. ft. internal dimension, ice trays having a total capacity of 4 lbs. of ice were provided in an evaporator similarto that shown in Fig. '7 and it was found that ice was frozen in about four hours at the 60 F. room temperature and in a relatively longer period of time in the 110 room.

The evaporator should have sufficient area to provide sufficient heat exchange with the atmosphere in the food preserving space 50a of the cabinet under the heaviest load conditions. In the preferred form, the evaporator is constructed to provide a long surface contact and the refrigerant is introduced at one end and is removed at the other. The effective refrigerating area extends in varying lengths from the intake of the evaporator according to refrigeration conditions. This area is more or less clearly indicated by the formation of frost on the evaporator, the point of its termination indicating the place where the 7 l plate 83 at the loop 82a, but the pipe may also continue downwardly after this contact and conlast substantial traces of liquid refrigerant have been converted into gas. This effective refrigerating area increases as the outside or room temperature increases because of the increased amount of refrigerant liquid entering the evaporator. The temperature. of the refrigerant within the evaporator also increases Withrise in outside temperature. However, the increase in re'- frigerating area, imposed by the greater quantity of liquid refrigerant, is relatively greater inproportion than the increase in refrigerant temperature, so that the air cooling effect Within the cabinet is increased notwithstanding the rise in evaporator temperature.

l The evaporator may be of any shape which permits proper compensation between air cooling capacity and heat inltration, such as a straight hollow vertical plate, and ice freezing means may Lbe isolated from the main evaporator, the refrigerant rst passing through the ice freezing means, but it is preferred to construct the same in the forms shown and described.

The compressor is started by a hand switch 90 which includes a starting circuit control and an overload control. This switch is intended to be used only when the system is originally started after installation, and thereafter only when the evaporator is to be defrosted or when the system is to be inspected or repaired.

Other forms of refrigerant expanders or restricters may be used. For example, an expander may be used in which a pressure responsive flexible member or bellows automatically varies the refrigerant passage or passages, the bellows being connected to a thermostatic bulb placed in thermal contact with the air surrounding the cabinet or in thermal contact with the condenser, the control being such that when the room temperature rises, the expander is opened more to permit a greater flow of refrigerant into the evaporator and thus cause an increase in evaporator temperature and effective refrigerating area substantially in the same manner and to the same degree of variation as the capillary restricter heretofore described. Another type of expander which may be used is one in which a pressure responsiveiiexible member or bellows automatically varies the refrigerant passage or passages,

the bellows being connected with a thermostatic bulb placed in thermal contact with the interior of the cabinet, preferably at a place suiiciently removed from the evaporator so that it is responsive only to cabinet food preserving compartment temperature rather than evaporator temperature. In this construction the arrangement is such that with a slight rise in cabinet temperature (but still within food preserving temperature limits) due to a rise in room temperature the expander is opened more to permit a greater flow of refrigerant into the evaporator with a consequent increase in evaporator temperature and effective refrigerating area, also substantially in the same manner and substantially to the same degree as the capillary restricter heretofore described; Still another type of expander may have pressure responsive flexible member or members for varying the refrigerant passage or passages, the pressure responsive member or members being responsive to condenser and evaporator pressures in such a manner that the expander automatically increases the evaporator temperature and effective crosssectional area in accordance with arise in condenser pressure (a function of the room temperature) in an amount sufcient to maintain food preserving cabinet temperatures under varying room temperatures. Some of these types of expanders or restricters are, of themselves, Well known in the art; but they have not been used in a cabinet and refrigrating systems which have been coordinated as herein disclosed.

mately 32 F. to approximately 50 F. which is suitable for preserving the ordinary foods used in a household and at the same time it is desired to provide a relatively small compartment of lower temperature suitable for freezing water, desserts and the like. These further coordinating steps are now described.

FURTHER CQORDINATING S'rnrs Fon HOUSEHOLDl RE FRIGERATION WITH Ion Pomzfcino.v MEANS When applying the principles of this invention to a household refrigerator the relationship of the refrigeration capacity of the system, the lieat leakage into the cabinet, and the evaporator pressures are coordinated with regard to the freezing temperature of water so that the ice-I making compartment of the evaporator operates at all times below the freezing temperature of. water; and so that the system has sufiicient reserve refrigerating capacity to freeze the water. The parts are so coordinated that the restricter varies the capacity of the system throughout the normal room temperature range (60-110) in an amount suillcient to produce the required quantity of ice and to maintain the cabinet Within the food preserving temperature zone.

The cabinet temperature, normally to be maintained, is selected sufficiently below the highest acceptable food preserving temperature (approximately 50) so that when a heavy unusual refrigeration load is placed on the system (such as that due to ice making) the cabinet temperature can rise temporarily several degrees and still be below the upper accepted food preserving limit. This permissible rise in cabinet temperature reduces temporarily the refrigeration requirements of the cabinet and makes available a certain portion of the refrigeration capacity of the system for making ice. The rise in cabinet temperature also makes available or releases a certain amount of refrigeration due to the holdove'r capacity of the cabinet and its food content. Moreover, when any extra refrigeration load is placed on the system, such as when the cabinet must be initially cooled, or when food is introduced into the cabinet, or when Water for ice making is introduced in an evaporator constructed as herein disclosed, the refrigeration capacity of the system automatically increases a certain amount to meet the increased load, so that this excess capacity is made available for ice-making in addition to the gains in refrigeration caused by the rise in cabinet temperature.

These coordinating steps are now more fully described with reference to Figs. 10 and l1. Fig. 10 has a chart substantially similar to Chart A of Fig. l, with additional information placed thereon illustrating some of these coordinating steps introduced by these ice-making requirements. In Fig. 11 Chart F corresponds with Chart A of Fig. 1 and shows characteristics of a system of proper capacity for the particular cabinet used. Chart C, Fig. 11, is representative of a refrigerating system which has too great a capacity to use to the full extent all of the advantages of this invention, when such a system is used with a cabinet of the heat leak under consideration, Chart H is representative of a refrigerating system of a capacity to small to provide ice-making temperatures in the evaporator when used with a cabinet of the heat leak under consideration.

Fig. 10 shows a refrgerating system substantially of the same character as that shown in Fig. l and in Chart F of Fig. l1, but there has been superimposed on the room temperature lines of Fig. 10 two lines, llpand Ill which represent respectively constant cabinet temperatures of 32 and 50 and are plotted from results obtained by multiplying the heat leak coeincient (3.4) times the heat differential between the cabinet and room temperatures. The space between these two lines represents the food preserving temperature zone in which the cabinet may be satsfactorily maintained. The refrigerant expander may be calibrated to maintain the cabinet temperature anywhere within this zone, and therefore .may maintain'cabinet temperatures corresponding to lines,'C", |12 or |13 or any other line which may be drawn within the zone, so that some of the advantages of this invention may be attained even if the cabinet temperature varies slightly but still lies within the acceptable food preserving temperature zone. The food preserving zone indicated is the one which is generally accepted for domestic household refrigerators. It is to be understood that different zones may be established where conditions are different from those in a domestic refrigerator, and where this invention is applied to cabinets in which other articles are refrigerated which have special refrigeration requirements, then the permissible zone of cabinet temperature may be adjusted to the particular requirements of the articles being cooled.

The line C" lies very nearthe lower limit line |10, and corresponds to line C, C of Figs. 1 and 9. The cabinet temperature of a refrigerator operating in accordance with line C can rise considerably before it passes the upper limit of the food preserving zone. The ice-making capacity of the system is preferably limited to an amount such that, while it may temporarily cause a slight risevin cabinet temperature, still it does not cause the-cabinet temperature to rise above A system of refrigerating capacity is used such that the point (the normal operation evaporator pressure at the highest room temperature) is a suicient distance below line |20 (which corresponds to the freezing temperature of water) to provide a vcold enough temperature and reserve refrigerating capacity for the ice-making capacity desired. The point |15 (204 B t. u.s) is the vertical reading from point |16 (50 cabinet temperature in 110 room) while the point |11 (251.6 B. t. u.s) is the vertical reading of point |55 (the normal cabinet temperature in 110 room). and |11 (bracket |80) represents the residual refrigerating capacity available for ice-making when the cabinet temperature rises to the highest permissible limit (50 F.). The holdover capacity of the cabinet and its contents also becomes available for ice-making since it releases refrigeration in warming from 36 (normal operation) to 50 by absorbing heat, thus making a further amount-of refrigeration available for ice- `making. The heat thus absorbed is indicated, for

convenience, as bracket X in Fig. 10. In addition, the capacity of the system automatically and inherently increases slightly when Water to be frozen is placed in the evaporator. Instead of operating at point 55, the system operates at slightly increased capacity indicated by the point |18. Its vertical reading |19 indicates the total B. t. 1.1.s produced by the system under this abnormal load, of which the ice-making capacity of the system is represented by brackets X and |8|. The heat exchange capacity between the evaporator and the ice trays is sovproportioned that the ice trays cannot transfer heat at a rate faster than is represented by the brackets X and |8| for any extensive period of time. When the evaporator is so proportioned or constructed, the cabinet temperature will not rise above the highest permissible limit (50 F.) while ice is being produced. Since substantially the same or more favorable conditions prevail throughout the entire room temperature range, this provision for ice-making is automatically correct for all other room temperatures. With the particular cabinet herein described, and with an evaporator substantially as shown in Fig. 7, with two shelves refrigerated by pipe 82a, and two ice trays totalling 4 lbs. of water were frozen in ve hours in a 110 room. From the aboveit will be seen that the system is provided with means for maintaining l The distance between points |15 tures in the ice-making space throughout the normal room temperature range notwithstanding the continuous operation of the compressor.

Chart F, Fig. 1l shows a system of desirable capacity for ice-making facilities in'the cabinet under consideration. This chart shows the same system'heretofore described with respect to Figs. 1, 9 and 10, the room temperature lines and the cabinet line C of Chart F showing the same values as the corresponding lines in Figs. 1', 9 and 10, but is shown on a reduced scale so that the system may be shown in its relation to systems having less desirable refrigeration capacities. Chart F considered with Fig. l0, yillustrates the proper coordination ofthe capacity of a refrigerating system with a household cabinet equipped for making ice cubes.

Chart G is representative of a system having more refrigerating capacity than is required for the particular cabinet under consideration. The system is capable of producing more than twice the number of B. t. u.s per hour in a F. room at the same back pressure than is produced by the system corresponding to Chart F. The system of Chart G when coordinated with the 'particular cabinet operates at unnecessarily low evaporator refrigerant temperatures, the theo- .retical vapor temperature in the evaporator actually being below 0 F. in the maximum normal room temperature of 110 F. Because of this,l such a system takes only partial advantage of the features of this invention, since it operates at undesirably low efficiencies, and, unless extremely low temperatures or extremely fast freezingcapacities are desired, a system of vless capacity is more advantageous. -The line C shows the back pressures at which such a system must operate in order to maintain cabinet temperatures equivalent to those of lines C, C' and C in the particular cabinet being investigated.

Chart H is representative of a system which .does not have suicient capacity to freeze ice.

or maintain food preserving cabinet temperatures at the higher room temperatures. The

line C" shows the back pressures necessary in is not below 32 F., and is incapable of freezing l ice at these higher room temperatures. Furthermore, the points |92 and |93 occur above the line |2| (corresponding to evaporator vapor temperature of 50 F.) and therefore the system is incapable of producing low enough temperatures in the evaporator to maintain a food preserving temperature in the cabinet. It is therefore undesirable to utilize a system of the capacity shown in Chart H where ice freezing is necessary at the higher room temperatures.

While I have indicated that a system having the characteristics shown in Fig. 10 and Chart F utilizes to the greatest extent the features and advantages of my invention when used in a household refrigerator equipped for ice-making, it is to be understood that many systems having greater or less relative refrigerating capacities may be used in the practice of my invention, v

and that such systems embody many features of my invention and attain its many advantages 1. A refrigerating apparatus consisting of a` household refrigerator' cabinet having a food preserving space and an ice-making space, a com- .pressor-condenser-evaporator refrigerator system 4 assembled with said cabinet, said compressor operating continuously at constant speed and circulating refrigerant continuously throughout the system andthroughout the normal room temperature range without stopping for cabinet temperature adjustments, a fixed passage restricter of proper cross-sectional area and length for varying the capacity of the system throughout the normal room temperature range in an amount sulcientto produce the required quantity of -ice andto maintain the cabinet within the food preserving temperature zone, said system being of sufficient capacity 'so that the effective vapor temperature in the evaporator is below 32 F. and being of sufficiently small capacity that the effective Vapor temperature in the evaporator is `above 0 F. while the system operates in the maxlmumnormal room temperature.

2. A refrigerating apparatus consisting of a household refrigerator cabinet having a food preserving space and an ice-making space, a compressor-condenser-evaporator refrigerator system assembled with said cabinet, said compressor operating continuously at constant speed and circulating refrigerant continuously throughout the system and throughout the normal room temperature range without stopping for cabinet temperature adjustments, said evaporator having a relatively long refrigerant passage between its inlet and outlet in thermal contact with an ice-making space and means shielding said icemaking space from the food preserving space of the cabinet, and an elongated orifice between said condenser and the inlet of said evaporator having a length and cross-sectional areancoordinated with the heat leak`into' the cabinet un-` der varying room temperatures so that the evaporator maintains the cabinet temperature within food preserving limits and the ice-making space below 32 F, notwithstanding the continuous operation of the compressor and the variations in room temperature.

3. A refrigerating apparatus consisting of adomestic refrigerator cabinet having a food preserving space and a freezing space shielded from said food preserving space, a compressor-condenser-evaporator refrigerator system assembled and transportable with said cabinetias a unit, said system being of a capacity not substantially in excess of the maximum normal refrigeration requirements of said cabinet under continuous compression operation. said compressor operating continuously at constant speed and circulating refrigerant continuously throughout the system during the entire refrigeration requirements of the cabinet without stopping for cabinet temperature adjustments, an evaporator in said cabinet having a relatively long refrigerant passage between its inlet and outlet in thermal contact -with said fr'eezing space and said food preserving space of the cabinet. and a refrigerant expander between said condenser and the inlet of said evaporator having a fixed length and crosssection of a size which varies the cooling capacity of said evaporator in an amount sufficient to lmaintain the cabinet temperature within food l v domestic refrigerator cabinethaving a food preserving space, a compressor-condenser-evaporator refrigerator system assembled and transportable with said cabinet as aunit, vsaid system being of a capacity not substantially in excess of the maximum normal refrigeration requirements of said cabinet under continuous compression operation, continuously at constant speed and circulating refrigerant continuously throughout the system said evaporator having a length and cross-sectional area coordinated with the heat leak into the cabinet'under varying room temperatures so that it varies the evaporator cooling capacity said compressor operating .during the entire refrigeration requirements of the cabinet without stopping for cabinet tem-A in an amount suflicient to maintain the cabinet food preserving space temperature within food preserving limits notwithstanding the continuous operation of the compressor and the variations in room temperature.

5. A refrigerating apparatus consisting of a household refrigerator cabinet having a food preserving space and an ice-making space, a compressor condenser evaporator refrigerator system assembled with said cabinet, said compresser operating continuously at constant speed and circulating refrigerant continuously throughout the system and throughout the normal room temperature range without stopping for cabinet temperature adjustments, and an elongated orifice of a length and cross-sectional area sufficient for varying the capacity of the system throughout the normal room temperature range in an amount sufficient to produce the required quantity of ice and to maintain the cabinet within the food preserving temperature zone.

6. A refrigerating apparatus consisting of a household refrigerator cabinet having a food preserving space andan ice-making space, a compressor condenser evaporator refrigerator system assembledwitnsaid cabinet, said compressor operating continuously at constant speed .l

and circulating refrigerant continuously throughout the system and, throughout the normal room temperature range without stopping for cabinet temperature adjustments, an elongated orifice of a length Aand cross-sectional area sufficient forl `varying the capacity of the 4preserving space and an ice-making space, a

compressor condenser evaporator refrigerator system assembled with said cabinet, said cornpressor operating continuouslyy at constant speed and circulating refrigerant continuously throughout the system and throughout the normal room temperature range, an elongated orifice -of a length and cross-sectional area sumcient for varying the capacity of the system throughout the normal room temperature range in an amount suicient to produce the required quantity of ice and to maintain the cabinet within the food preserving temperature zone, said system being not more than twice the refrigeration capacity required to maintain the cabinet within the food preserving temperature zone and to produce the required quantity of ice in the maximum room temperature.

8. A refrigerating apparatus consisting of a household refrigerator cabinet having a food preserving space and an ice-making space, a compressor condenser evaporator refrigerator `system assembled with said cabinet, lsaid compressor operating continuously at constant speed and circulating refrigerant continuously throughout the system and throughout the normal temperature range without stopping for cabinet ,temperature adjustments, 'an elongated orice of a length and cross-sectional area sufficient for varying the capacity of the system throughout the normal room temperature range in an amount suiiicient to produce the 'required quantity of ice and to maintain the cabinet within the food preserving temperature zone,.said system being of sumcient capacityV so that the eiective vapor temperature in the evaporator is below 32 F. while the system operates in the maximum normal room temperature, and said system being not more thanv twice the refrigeration capacity required to maintain the cabinet within the food preserving temperature zone and to produce the required quantity of ice in the maximum room temperature,

9. A refrigerating apparatus consisting of a household refrigerator cabinet having a. food preserving space and an ice-making space, a compressor condenser evaporator refrigerator system assembled with said' cabinet, said com- .cabinet having a food preserving zone, a refrigerating system therefor of a capacity not substantially in excess of the maximum normal refrigeration requirements of said cabinet, said system comprising a compressor, a condenser, a xed restriction and an evaporator provided with a freezing zone, all having passages and being connected in series to form a closed refrigerant circuit, the relative proportion of the parts of the system being such that the rate of heat absorption at the evaporator is automatically varied to maintain the temperature of said food preserving zone above 32 F. and within food preserving temperatures and the freezing zone below 32v F. while the compressor runs continuously at constant speed and the size of every passage in the system is maintained unchanged.

ANDREW A. KUCHER.