GB2061475A

GB2061475A - Refrigerating Apparatus

Info

Publication number: GB2061475A
Application number: GB8031161A
Authority: GB
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1979-10-01
Filing date: 1980-09-26
Publication date: 1981-05-13
Also published as: IT1132895B; IT8025019A0; GB2061475B

Abstract

Refrigerating apparatus includes freezing and refrigerating compartments to be controlled to different temperatures and with respective evaporators. During operation of a compressor (20), liquid refrigerant is always fed to the freezer evaporator (52), but is selectively fed to the refrigerator evaporator (48) by a feed control system including a vapor bubble pump (A), a tank (24) for storing liquid refrigerant prior to feeding it to the respective evaporators, and a conduit for feeding refrigerant to the freezer evaporator (52) by operation of the vapor bubble pump (A) whose continued operation acts to cut off the supply to the refrigerator evaporator (48) by reducing the level in tank (24). A part (38) of the conduit extends through the tank in heat exchange relation with the refrigerant stored in the tank to enhance efficiency of the refrigerating cycle. <IMAGE>

Description

SPECIFICATION Refrigerating Apparatus This invention relates to a refrigerating apparatus and more particularly to an improvement in a refrigerating apparatus in which at least two evaporators are controlled to different temperatures.

Generally, a refrigerator having a freezing compartment and a refrigerating compartment which are controlled to different temperatures has separate evaporators for the freezing compartment and for the refrigerating compartment because separate cooling is necessary for each compartment. Although separate evaporators are provided, it is preferable that a compressor and a condensor are used in common for those separate evaporators.

Accordingly, refrigerant feed control to one or both of the evaporators is necessary. For example, the refrigerant is always fed to the freezing evaporator while the refrigerant is selectively fed to the refrigerating evaporator by a solenoid valve when the compressor is energized. Separate temperature control is thus attained by control of the solenoid valve in conjunction with control of the compressor.

However, such solenoid valve is usually a mechanically movable one which is encased in a heat-insulating material so that it is difficult to maintain or inspect the valve after the refrigerator is assembled. Accordingly, the life and reliability of the refrigerator are not sufficient, and moreover, this structure is too expensive.

Feed control devices or arrangements which employ a vapor bubble pump providing valve action to refrigerant have been developed. Thus, mechanical movable parts can be eliminated from the feed control devices of the refrigerator. Such arrangements are disclosed, for example, in U.S.

Patent No. 2,697,331.

Accordingly, this invention seeks to provide a refrigerating apparatus which has a refrigerant feed control arrangement incorporating a vapor bubble pump of stable and efficient operation.

According to one aspect of the present invention, there is provided apparatus for feeding refrigerant in a refrigerator to a first evaporator and to a second evaporator connected to receive refrigerant from the first evaporator, comprising: tank means for storing refrigerant having an inlet for receiving refrigerant, a first outlet for supplying refrigerant to said first evaporator and a second outlet; conduit means connected to said second outlet for supplying said refrigerant to said second evaporator, at least part of said conduit means extending through said tank so as to exchange heat, in use, with refrigerant therein; and vapor pump means provided in a portion of said conduit means and so arranged that the operation of said pump causes said refrigerant to be supplied to said second evaporator and causes the supply to said first evaporator to be cut off.

According to a further aspect of the invention there is provided refrigerating apparatus comprising: a first evaporator for receiving flow of refrigerant therethrough so as to cool it, in use, to temperatures within a first range; a second evaporator connected to said first evaporator for receiving refrigerant through said first evaporator so as to cool it, in use, to temperatures within a second range; a tank for storing said refrigerant and having a first outlet for supplying refrigerant to said first evaporator, a second outlet and in inlet; a condensor connected to said inlet for supplying said refrigerant to said tank; conduit means connected to said second outlet for supplying refrigerant to said second evaporator and extending at least in part through said tank in heat exchange relation with refrigerant therein; and vapor pump means provided in a portion of said conduit means and so arranged that in operation said refrigerant is supplied to said second evaporator through said conduit means.

Other objects and advantages of this invention will be apparent from the following detailed description of the presently preferred exemplary embodiments taken in conjunction with the accompanying drawings, in which: Figure 1 shows a schematic view of a refrigerant flow circuit of this invention; Figure 2 is a schematic cross-sectional view of the feed control device incorporated in the circuit shown in Figure 1, showing the bubble pump not in operation; Figure 3 is a schematic cross-sectional view of the feed control device incorporated in the circuit shown in Figure 1, showing the vapor pump in operation; Figure 4 is an enlarged view, partly in section of the vapor bubble pump shown in Figures 1,2, and 3; Figure 5 shows a wiring diagram for the apparatus of this invention; Figure 6 is a schematic planar view of assembled feed control device of this invention;; Figures 7 to 10 are schematic cross-sectional views of modified feed control device incorporatable in the circuit shown in Figure 1; Figure 11 is a schematic plan view of the feed control device shown in Figure 7; and Figure 12 is an enlarged view, partly in section of the feed control device shown in Figure 10.

Referring to Figure 1, high temperature gas of a refrigerant which is compressed by a compressor 20 is condensed by a condensor 22 and supplied to a liquid tank 24 of a feed control device 26 through a pressure regulator such as a capillary tube 28 and a conduit 30. One end of conduit 30 is extended through a top wall 32 of tank 24 and located in tank 24 at a predetermined height as indicated by L in Figure 1.

Feed control device 26 includes a conduit 34 which is formed with a first body 36 and a second body 38. First body 36 is located almost entirely outside of tank 24 while second body 38 is located almost entirely in tank 24.

First body 36 includes a generally U-shaped portion 40 at a lower end thereof. One leg end 40a of generally U-shaped portion 40 is extended through the bottom 42 of tank 24 to form a tank outlet. First body 36 also includes an inverted generally U-shaped portion 44 at an upper end thereof. One leg end 44a of inverted generally Ushaped portion 44 is extended through top wall 32 and is inserted or connected to second body 38. Body 38 has a diameter larger than that of inverted generally U-shaped portion 44 so that gaseous pressures developed in tank 24 and conduit body 34 are equalized.

One end of conduit 46 which forms an inlet is extended through top wall 32 of tank 24 and is located at a higher position than L as indicated by M in Figure 1 so as not to draw the refrigerant before storing in tank 24. The other end of conduit 46 is connected to a refrigerator evaporator 48 through a capillary tube 50.

Refrigerator evaporator 48 is connected to a freezer evaporator 52 by a connecting conduit 54 to which one end of second body 38 is connected through a capillary tube 56. Freezer evaporator 52 is connected to compressor 20 to form a closed refrigerating cycle.

A heater 58 is provided at the other leg end or rising portion 40b of generally U-shaped tube 40.

As shown in Figure 4, tube 40 has irregularly formed portions 60 with alternate concave surfaces 60a and convex surfaces 60b in the lower end with heater 58 extending there about and about a portion of tube 40 above surfaces 60a and 60b. First conduit body 36, specifically irregularly formed portions 60 and heater 56 form a vapor bubble pump A. A 5 watt electrical heater would be sufficient for this purpose. Each leg end 40a and 40b of tube 40 is spaced from each other at a sufficient distance, such as 80 mm, so that heater 56 can be easily wound around leg end 40b.

Figure 5 is a wiring diagram of this embodiment. Generally, compressor 20 operates within a given temperature range of a freezing compartment 61, as shown in Figure 6, except when defrosting operation is not selected. During the operation of compressor 20, refrigerant is always fed to freezer evaporator 52, but refrigerant flow caused by condensor 22 is selectively fed to refrigerator evaporator 48 depending on the temperature of the refrigerating compartment (not: shown) for preventing the same from being overcooled.

A motor 70 of compressor 20 is driven when the contacts (a-c) of a defrost switch 72 are closed (i.e., defrosting operation is now chosen) upon the closure of a control switch 74, which is closed when the temperature of freezing compartment 60 reaches an upper end of a predetermined operating range. Heater 58 of vapor bubble pump A, a connecting pipe heater 76 and a drain gutter 78 are energized when the temperature of the refrigerating compartment falls below a predetermined value so that a refrigerating control switch 80 is turned on. When freezing compartment 60 exceeds the lower end of its predetermined operating range, motor 70 is stopped and control switch 74 is opened. The defrosting cycle, which is conventional, is attained.

by closing contacts (bye) of defrost switch 72 to energize a defrost heater 82 for heating freezer evaporator 52 and a defrost sensor heater for obtaining stable operation of defrost heater 82.

The defrost sensor includes a bimetal switch 86 which opens when the defrosting cycle is finished.

A door switch 88 is closed when the door of the refrigerating compartment is opened and a lamp 90 which is located in the refrigerating compartment is turned on. A drain heater 92 prevents the drain opening of the freezing compartment from freezing, a heater 94 heats control switch 74 for ensuring stable operation thereof, and a fuse 96 is connected in series with heater 58 of vapor bubble pump A.

The operation will now be explained. When the temperature of the refrigerating compartment and the freezing compartment are higher than respective predetermined values, control switch 74 is kept closed and refrigerating control switch 80 is kept open. The motor 70 of compressor 20 is driven while heater 58 is kept de-energized.

The refrigerant which is compressed by compressor 20 is stored in liquid tank 24. The liquid refrigerant flows into conduit 46 when the liquid level in tank 24 rises higher than the level M, as easily understood from Figure 2.

The liquid refrigerant goes to refrigerator evaporator 48 through conduit 46 and capillary tube 50, and to freezer evaporator 52 through conduit 54 so that both compartments are cooled. In this condition, it is expected that the liquid refrigerant will not flow in second body 38 of conduit body 34 through generally U-shaped tube 44 because the inner gaseous pressures developed in liquid tank 24, first body 36 and second body 38 are kept equal by loosely connecting leg end 44a and second body 38 in tank 24 and liquid levels in tank 24 and first body 36 are kept equal.

Heater 58 is energized when control switch 80 turns on due to the fact that the refrigerator compartment has been cooled to a predetermined temperature. Vapor bubbles of liquid refrigerant are produced by heating leg end or rising portion 40b with heater 58. The liquid refrigerant is pumped up by the bubbles and overflows from leg end 44a into body 38, as easily understood from Figure 3. At this time the liquid refrigerant level in tank 24 is reduced because the liquid refrigerant flows into freezing evaporator 52 through capillary tube 56. It is expected that liquid refrigerant will not flow to refrigerator evaporator 48 through conduit 46 and capillary tube 50 because the liquid level in tank 24 is lower than the level indicated by M. The inlet of conduit 46 is in a higher position than the top level of stored refrigerant in tank 24. The cooling of the refrigerating compartment is, thus, interrupted because of no flow of refrigerant to refrigerator evaporator 48. This condition continues until the temperature of the refrigerator compartment reaches the upper end of its predetermined operating temperature range at which time heater 58 is automatically de-energized, restoring the normal flow of liquid refrigerant through the refrigerating compartment to the freezer compartment.

Heater 58 is wound around the outer surface of irregularly formed portions 60 so that the bubbles are produced relatively quickly at irregularly formed portions 60. Bubbles are also produced at non-irregular portions above irregular portions 60; however, they are smoothly produced and the resistance against the flow of liquid refrigerant including the bubbles produced at lower level is small. The bubbles can go up smoothly and pumping action for pushing up the' refrigerant begins relatively quickly. The pumping efficiency is, thus, improved. As leg end 40a of tube 40 is spaced from heater 58, the liquid refrigerant in leg end 40a is prevented from producing bubbles.

It will be observed that as shown in Figures 1 to 3, a part of conduit body 36, specifically second body 38, is disposed in heat exchange relation with refrigerant stored in tank 24. This heat exchange arrangement provides for transfer of heat from warmer overflow refrigerant in second body 38 to colder liquid refrigerant in tank 24. Accordingly, cooled and almost liquified refrigerant is fed to freezer evaporator 52 while the warmed refrigerant is fed to conduit body 34 so that the bubbles can be quickly produced by heater 58. This heat exchange arrangement enhances the efficiency of the refrigerating cycle.

Figure 6 shows the assembled feed control device.

To prevent unwanted flow of liquid refrigerant to refrigerator evaporator 48 when vapor bubble pump A is operating and to prevent the liquid refrigerant flowing back to compressor 20 due to excessive supply of liquid refrigerant to freezer evaporator 52 when vapor bubble pump A begins to operate, the volume of tank 24 must properly be determined. The effective volume measured between inlets of conduits 34 and 46 would usually be selected to be 10-50 cc. If the effective volume is less than such preferable values, unwanted flow of liquid refrigerant to refrigerator evaporator 48 is likely to occur when vapor bubble pump A is operating and unwanted flow of refrigerant in liquid form back to compressor 20 is likely to occur when vapor bubble pump A starts to operate.

Obviously, the effective volumes are closely related to the dimensions of tank 24 and second body 38. Accordingly, the design of tank 24 and second body 38 must take into consideration the outer diameter of second body 38. It also should be borne in mind that if maximum equalisation of gaseous pressure developed in tank 24 and conduit body 34 is expected, a passage or an opening should communicate tank 24 to conduit body 34 with a cross-sectional area more than 10 mm2.

Figure 7 shows a modified feed controller 26 which has a narrowed outlet on leg end 44a of generally inverted U-shaped tube 44. With a narrowed outlet end on leg end 44a, second body 38 may have a relatively small outer diameter whilst maintaining an adequate equalizing effect.

Such a narrowed end may be formed by squeezing. However, the narrowed end must have a certain minimum inner diameter to prevent the liquid refrigerant from being retained at the end.

Experimental results on this embodiment reveal that the minimum inner cross-sectional area is about 3 mm2. Instead of leg end 44a being narrow, an enlarged end may be provided on the end of second body 38.

As shown in Figure 8, the liquid refrigerant may be supplied to tank 24 from condensor 22 and to refrigerator evaporator 48 from tank 24 by using capillary tubes 28 and 50, respectively, instead of conduits 30 and 46. A pipe 100 in which capillary tubes 28 and 50 are bundled is extended through top wall 32 of tank 24. One end of pipe 100 is located in tank 24 while the other end thereof is outside of tank 24 and tightly sealed. The end of each capillary tube 28, 50 is placed at a predetermined height in tank 24 in the same manner as conduits 30 and 46 in Figures 1 to 3.

This embodiment has the advantage of simplifying assembly of feed controller 26 in comparison with embodiment shown in Figures 1 to 3. Two attaching operations are required at top wall 32 in this embodiment while three attaching operations are required in the embodiment shown in Figures 1 to 3.

As shown in Figure 9, conduit body 34 may be formed in one piece. In such instance, at least one opening 102 must be provided at a predetermined height for equalizing gaseous pressure developed in tank 24 and cdnduit body 34 as in the embodiment shown in Figures 1 to 3.

Figure 10 shows another embodiment of which conduit body 34 which is formed in one piece is extended through both walls 32 and 42 and is almost entirely contained in tank 24 except for U-shaped section 40. The liquid refrigerant flowing up the conduit body is supplied to freezer evaporator 52 through capillary tube 56 without using conduits. As clearly shown in Figure 12, capillary tube 56 is inserted in conduit body 34 and its end is located lower than an opening 102 provided on conduit body 34.

As mentioned above, the preferred embodiments of this invention provide a conduit for feeding the refrigerant to one of the evaporators when a vapor bubble pump is operating. One part of the conduit extends in the tank in heat exchange relation with the liquid refrigerant therein so that the warmed refrigerant including bubbles is cooled and is almost liquified before being fed to one of the evaporators while the liquid refrigerant stored in the tank is slightly warmed before being fed to the vapor bubble pump. Accordingly, the efficiency of the refrigerating cycle is enhanced.

Further, as the conduit provides a passage or an opening in a liquid tank so as to put the tank and conduit in communication with each other and equalize a gaseous pressure developed in the tank and the conduit, an additional pipe connecting the tank and the conduit body for equalizing purposes is not required. Accordingly, the feed control arrangement can be simplified.

The feed control device may be changed to allow refrigerant flow both to refrigerator and freezer evaporators when the vapor bubble pump operates, although according to the above embodiments the refrigerant is fed only to the freezer evaporator when the vapor pump operates. This invention can be applied to freezing apparatus having more than two evaporators controlled to different temperatures.

Claims

1. Apparatus for feeding refrigerant in a refrigerator to a first evaporator and to a second evaporator connoted to receive refrigerant from the first evaporator, comprising: tank means for storing refrigerant having an inlet for receiving refrigerant, a first outlet for supplying refrigerant to said first evaporator and a second outlet; conduit means connected to said second outlet for supplying said refrigerant to said second evaporator, at least part of said conduit means extending through said tank so as to exchange heat, in use, with refrigerant therein; and vapor pump means provided in a portion of said conduit means and so arranged that the operation of said pump causes said refrigerant to be supplied to said second evaporator and causes the supply to said first evaporator to be cut off.

2. Apparatus as in Claim 1, wherein said conduit means is connected to the interior of said tank so as to equalise gaseous pressures developed in said tank.

3. Apparatus as in Claim 2, wherein said conduit means includes a generally U-shaped tube provided at a lower part thereof, one leg end of said generally U-shaped tube extending into said tank means to collect the refrigerant.

4. Apparatus as in Claim 3, wherein said conduit means includes an inverted generally Ushaped tube provided at an upper part thereof, one leg end of said inverted generally Ushaped tube extending downwardly into said tank means, and a heat exchange tube communicating with said one leg end and extending through said tank means, to feed refrigerant to said second evaporator.

5. Apparatus as claimed in Claim 4, wherein said one upper leg of the inverted generally Ushaped tube is so connected to said heat exchange tube that the refrigerant fed by said vapor pump means can be fed to said heat exchange tube without leakage.

6. Apparatus as in Claim 5, wherein a space is provided between the said leg and the tube for equalizing pressure.

7. Apparatus as in Claim 2, wherein a portion of said conduit means in said tank is provided with an opening for equalizing pressure.

8. Apparatus as in Claim 1, including a pipe extending into said tank means and defining said inlet and first outlet.

9. Apparatus as in Claim 8, including a first capillary tube extending through said pipe means for supplying refrigerant to said tank means and a second capillary tube for supplying refrigerant to said first evaporator.

10. Refrigerating apparatus comprising: a first evaporator for receiving flow of refrigerant therethrough so as to cool it, in use, to temperatures within a first range; a second evaporator connected to said first evaporator for receiving refrigerant through said first evaporator so as to cool it, in use, to temperatures within a second range; a tank for storing said refrigerant and having a first outlet for supplying refrigerant to said first evaporator, a second outlet and an inlet; a condensor connected to said inlet for supplying said refrigerant to said tank; conduit means connected to said second outlet for supplying refrigerant to said second evaporator and extending at least in part through said tank in heat exchange relation with refrigerant therein; and vapor pump means provided in a portion of said conduit means and so arranged that in operation said refrigerant is supplied to said second evaporator through said conduit means.

11. A refrigerator apparatus as in Claim 10, wherein said conduit means is connected to the interior of said tank means to equalise gaseous pressures developed in said tank means.

12. Refrigerator apparatus as in Claim 11, wherein said conduit means includes a generally U-shaped tube provided at a lower part thereof, one leg end of said generally U-shaped tube being extended into said tank to collect the refrigerant.

1 3. Refrigerator apparatus as in Claim 12, wherein said conduit means includes an inverted generally U-shaped tube provided at upper part thereof, one leg end of said inverted generally Ushaped tube extending into said tank to feed refrigerant from said vapor bubble pump means.

14. Refrigerator apparatus as in Claim 13, wherein said one leg end of inverted generally Ushaped tube is so connected to said second body that the refrigerant fed by said vapor bubble pump means can be fed to said second evaporator without leakage.

1 5. Refrigerator apparatus as in Claim 12, 13, or 14, wherein the vapor bubble pump is provided in the other leg end portion of said generally Ushaped tube.

1 6. Refrigerator apparatus substantially as herein described with reference to the accompanying drawings.