REFRIGERATOR OR FREEZER WITH ENHANCED EFFICIENCY
A refrigerator or a freezer comprises a primary refrigeration system (11) which is augmented with a passive secondary refrigeration loop (15) having a condenser (30) in thermal contact with a primary fluid line (12) at the location between a primary compressor (16) and a primary condenser (18) and preferably placed outside a building so that the passive secondary refrigeration loop (15) provides cooling to the primary refrigeration system (11) when the outside temperature is sufficiently low The condenser (30) of the passive secondary refrigeration loop (15) is positioned above the points where the primary fluid line (12) connects with mlet (32) and outlet (34) lines of the secondary loop condenser (30)
The present application claims the benefit of prior provisional application Ser. No. 601694,134, filed Jun. 27, 2005, the contents of which are hereby incorporated herein by reference.
BACKGROUNDThis invention relates to a refrigerator or freezer and to a method of enhancing the efficiency of a refrigerator or freezer.
Known vapour compression refrigerators, including domestic refrigerators, have a refrigerant filled fluid line which defines a loop incorporating, in fluid flow order, an evaporator, a compressor, a condenser, and an expansion valve. The evaporator is associated with a cavity to be cooled. The condenser has a heat exchanger, typically in the air flow path of a fan, to dissipate heat. The refrigerant may be a low boiling point liquid, such as a hydroflurocarbon. In operation, the compressor draws gaseous refrigerant in the fluid line from the evaporator and pumps the refrigerant toward the condenser. The high pressure in the condenser and the cooling resulting from the heat exchanger and fan liquifies the refrigerant. Cooled liquid refrigerant leaving the condenser passes through the expansion valve and enters the evaporator where it may vaporise by drawing heat from the cavity to be cooled.
A typical domestic refrigerator consumes 390 to 650 kilowatt hours per year and a typical commercial refrigerator consumes considerably more energy than a domestic refrigerator. These refrigerators throw off waste heat into the room in which they are housed. It would be advantageous to reduce the power consumption of refrigerators.
SUMMARY OF INVENTIONThe primary refrigeration system of a refrigerator or freezer is augmented with a passive refrigeration loop or spur which has a condenser that may be placed outside so that the passive loop or spur cools provides cooling to the primary refrigeration system when the outside temperature is sufficiently low.
A refrigerator or freezer may have a primary refrigeration circuit with a circuit condenser, a circuit evaporator, a circuit compressor, and a circuit fluid line defining a loop which fluidly connects the circuit evaporator to the circuit condenser through the circuit compressor such that the circuit compressor draws refrigerant in the circuit fluid line from the circuit evaporator and pumps the refrigerant toward the circuit condenser. In an aspect of the invention, a passive refrigeration loop or spur is added. The loop or spur has a loop or spur condenser and a loop or spur line fluidly communicating with a lower portion of the loop or spur condenser. The loop or spur line is associated with the fluid line of the active circuit between an outlet of the circuit evaporator and an inlet of the circuit condenser at a location below the loop or spur condenser.
According to another aspect of the invention, there is provided a refrigerator or freezer, comprising: a closed primary refrigeration system; a closed secondary, passive, refrigeration circuit; said secondary refrigeration circuit having a heat exchanger in heat exchange relation with said primary refrigeration system, said secondary passive refrigeration circuit being one of a heat pipe loop and a thermosiphon loop.
According to a further aspect of the invention, there is provided a method of enhancing efficiency of a refrigerator or freezer, comprising: positioning a heat exchanger of a passive refrigeration loop having said heat exchanger and a passive loop condenser in heat exchange relation with waste heat bearing element of a primary refrigeration system of said refrigerator or freezer; positioning said passive loop condenser outside a building housing said refrigerator or freezer such that said passive loop condenser is exposed to ambient temperature, said passive loop condenser positioned above said heat exchanger.
Other features and advantages will become apparent from a review of the detailed description in conjunction with the drawings.
In the figures which illustrate example embodiments of the invention,
Turning to
The secondary passive refrigeration loop 15 may have a condenser 30 located outside building 50 coupled in parallel to fluid line 12 through a loop inlet line 32 extending from fluid line 12 (through a wall of the building) to an upper portion of the loop's condenser 30 and a loop outlet line 34 extending from a lower portion of the loop's condenser (through a wall of the building) to fluid line 12. Normally the outlet line will be connected to the lowermost part of the loop's condenser which, in the embodiment of
A shield 54 may be disposed around the loop's condenser 30 to shield the heat pipe from the sun.
The refrigerant may be a low boiling point liquid, such as a hydroflurocarbon. The compressor may be a positive displacement compressor such as a compressor with a piston to draw refrigerant in from the evaporator on a down stroke and expel it toward the compressor on an upstroke.
In operation, the compressor draws gaseous refrigerant in the fluid line from the evaporator and pumps the refrigerant toward the condenser. Some of the gaseous refrigerant pumped by the compressor travels through loop inlet line 32 to the upper portion of the loop's condenser 30. If the ambient air outside building 50 is sufficiently cold, this refrigerant will condense to liquid which will be gravity fed down the loop's condenser 30 and down the loop outlet line 34 back to the fluid line 12. In consequence, a portion of the refrigerant in the fluid line between the compressor and the condenser is condensed to liquid. This reduces the pressure at the outlet of the compressor, thereby reducing the back pressure on the compressor and, in consequence, the load on the compressor. Hence the power required by the condenser to operate is reduced.
The cooler refrigerant then enters the condenser. The pressure in the condenser and the cooling resulting from the heat exchanger and fan liquifies remaining gaseous refrigerant. Cooled liquid refrigerant leaving the condenser passes through the expansion valve and enters the evaporator where it may vaporise by drawing heat from the cavity to be cooled.
Refrigerant will travel through the loop 15 whenever the temperature at the loop condenser 30 is less than the refrigerant temperature at the point where the loop inlet line 32 joins fluid line 12. The refrigerant temperature at the outlet 36 of the circuit evaporator 14 will typically be close to the temperature in cavity 22. Consequently, if the outdoor temperature is expected to be less than the temperature in cavity 22, the loop inlet and outlet lines could join to the fluid line 12 between the outlet 36 of the evaporator and the inlet of the compressor 16. However, the efficiency of the passive refrigeration loop 15 is directly proportional to the differential between the temperature of refrigerant where the loop inlet 32 joins fluid line 12 and the temperature at the loop condenser 30. Thus, while the heat pipe inlet may be positioned anywhere between the outlet of the circuit's evaporator and the inlet of the circuit's condenser, it is advantageously positioned at the outlet of the compressor. This is for the reason that this is the location in fluid line 12 where the refrigerant is the hottest (due to the heat of compression, which is about 50° C. in a domestic refrigerator) and so cooling such refrigerant maximizes the reduction in the load on the compressor.
The shield about the loop's condenser reduces solar heating of the loop's condenser.
If the ambient temperature is too high to allow gaseous refrigerant in the loop's condenser 30 to condense, as more gaseous refrigerant enters the loop's condenser, the vapour pressure in the loop's condenser will rise to the pressure in fluid line 12. At this point, no further gaseous refrigerant will migrate into the loop's condenser and refrigerant in line 12 will simply by-pass the loop's condenser. This situation will continue until the ambient temperature drops to a point where refrigerant begins to condense in the loop's condenser. The result is that the loop's condenser acts as a thermal diode, naturally shutting down when ambient temperatures are too high to allow refrigerant to condense, and naturally turning on again whenever ambient temperatures drop sufficiently to result in refrigerant condensing in the loop's condenser. Of course the lower the ambient temperature, the more quickly refrigerant will condense in the loop's condenser and, hence, the greater the efficiency increase provided by the passive refrigeration loop.
The operation is similar to what has been described in conjunction with
Turning to
In this embodiment, the loop inlet line 232, loop condenser 30, heat pipe outlet line 234 and heat exchanger/evaporator 260 form a closed heat pipe loop 211 which is isolated from refrigeration circuit 11. The isolated refrigeration loop 211 may be partially filled with any suitable phase change refrigerant, such as a hydroflurocarbon refrigerant. The refrigerant in circuit 211 may be termed the second refrigerant.
In operation, hot refrigerant in fluid line 12 at the outlet of compressor passes through heat exchanger/evaporator 260. The cool second refrigerant in heat exchanger/evaporator 260 absorbs heat from the hot refrigerant in the fluid line 12 and, in consequence, is heated. The heating of the second refrigerant causes it to vaporise and migrate into loop condenser 30. In the loop condenser, the second refrigerant is cooled and condenses. The condensed refrigerant flows back down to the heat exchanger 260.
As is apparent from
Where a closed passive refrigeration loop is employed, rather than partially filling the passive circuit with a liquid phase change refrigerant, the circuit can be completely filled with a liquid refrigerant, which may or may not be a phase change refrigerant. With the circuit completely filled with refrigerant, the circuit acts as a thermosiphon loop rather than as a heat pipe loop. More specifically, when the second refrigerant is heated in heat exchanger 260, it become less dense and convectively flows upwardly along line 232 toward condenser 30. In condenser 30, the refrigerant cools, becomes more dense and flows downwardly along line 234 back to the heat exchanger. An exemplary non-phase change refrigerant is ethanol.
The condenser 30 of any of the embodiments may simply be a hollow pipe which is vertically oriented, or which declines at an acute angle from the vertical. Alternatively, the hollow pipe condenser, the loop outlet line and the evaporator/heat exchanger may be lined with wicks. In such instance, and where these elements are part of an isolated refrigerant loop (as, for example, in either of the embodiments of
To increase the heat transfer rate of the condenser 30 or 330, it could be provided with heat exchange fins.
With the embodiments of any of
While in the example embodiments the primary refrigeration cycle is a vapour compression cycle, it will be apparent to those skilled in the art that the teachings of this invention have application to refrigeration systems where the primary refrigeration cycle is of some other type. More specifically, the isolated refrigeration loops described in conjunction with
While the example embodiments have been described in conjunction with a refrigerator, equally the refrigerator may be a freezer.
Other variations will be apparent to those skilled in the art and, therefore, the invention is defined in the claims.
Claims
1. A refrigerator or freezer comprising:
- a primary refrigeration circuit having a circuit condenser, a circuit evaporator, a circuit compressor, and a circuit fluid line defining a loop which fluidly connects said circuit evaporator to said circuit condenser through said circuit compressor such that said circuit compressor draws refrigerant in said circuit fluid line from said circuit evaporator and pumps said refrigerant toward said circuit condenser;
- a passive refrigeration loop or spur comprising a loop or spur condenser;
- a loop or spur line fluidly communicating with a lower portion of said loop or spur condenser;
- said loop or spur line associated with said fluid line between an outlet of said evaporator and an inlet of said condenser at a location below said loop or spur condenser.
2. The refrigerator or freezer of claim 1 wherein said loop or spur line is associated with said circuit line between said circuit compressor and said circuit condenser.
3. The refrigerator or freezer of claim 1 wherein said loop or spur line is associated with said circuit line at an outlet of said circuit compressor.
4. The refrigerator or freezer of claim 1 wherein said passive refrigeration loop or spur is a loop, said loop or spur condenser is a loop condenser, and said loop or spur line is a loop outlet line and further comprising a loop inlet line extending to an upper portion of said loop condenser, said loop inlet line associated with said circuit line between an outlet of said circuit evaporator and an inlet of said circuit condenser, said loop outlet line associated with said circuit line downstream of said loop inlet line.
5. The refrigerator or freezer of claim 4 wherein said loop inlet line is associated with said circuit line between said circuit compressor and said circuit condenser.
6. The refrigerator or freezer of claim 4 wherein said loop inlet line is associated with said circuit line at an outlet of said circuit compressor.
7. The refrigerator or freezer of any one of claim 4 to claim 6 claim 4 wherein said loop inlet line and said loop outlet line are fluidly connected at said circuit line through a loop heat exchanger in heat exchange relation with said circuit line.
8. The refrigerator or freezer of claim 7 wherein said loop heat exchanger is a spiral tube, one end of which is in fluid communication with said loop outlet line and another end of which is in fluid communication with said loop inlet line, said spiral tube being wound around said circuit line.
9. The refrigerator or freezer of claim 4 wherein said loop inlet line is tapped into said circuit line and wherein said loop outlet line is tapped into said fluid line downstream of said loop inlet line.
10. The refrigerator or freezer of claim 1 wherein said compressor is a positive displacement compressor.
11. The refrigerator or freezer of claim 1 further comprising a shield positioned for shading said loop or spur condenser from sun.
12. The refrigerator or freezer of claim 4 further comprising a shield positioned for shading said loop condenser from sun.
13. The refrigerator or freezer of claim 1 further comprising a circuit expansion valve between an outlet of said circuit condenser and an inlet of said circuit evaporator.
14. The refrigerator or freezer of claim 1 wherein said loop or spur line functions as a loop or spur inlet line and a loop or spur outlet line.
15. A refrigerator or freezer, comprising:
- a closed primary refrigeration system;
- a closed secondary, passive, refrigeration circuit;
- said secondary refrigeration circuit having a heat exchanger in heat exchange relation with said primary refrigeration system, said secondary passive refrigeration circuit being one of a heat pipe loop and a thermosiphon loop.
16. A method of enhancing efficiency of a refrigerator or freezer, comprising:
- positioning a heat exchanger of a passive refrigeration loop having said heat exchanger and a passive loop condenser in heat exchange relation with a waste heat bearing element of a primary refrigeration system of said refrigerator or freezer;
- positioning said passive loop condenser outside a building housing said refrigerator or freezer such that said passive loop condenser is exposed to ambient temperature, said passive loop condenser positioned above said heat exchanger.
17. The method of claim 16 wherein said passive refrigeration loop is one of a heat pipe loop and a thermosiphon loop.
18. The method of claim 16 wherein said passive refrigeration loop is a heat pipe loop, said heat pipe loop comprising a heat pipe line fluidly connecting said heat exchanger with a lower portion of said passive loop condenser.
19. The method of claim 18 wherein said heat pipe line is a heat pipe outlet line and further comprising a heat pipe inlet line fluidly connected to said heat pipe outlet line through said heat exchanger, said heat pipe inlet line in fluid communication with said passive loop condenser.
20. The method of claim 16 wherein said heat exchanger is a tube and wherein said positioning said heat exchanger comprises winding said tube around said waste heat bearing element.
21. The method of claim 16 wherein said primary refrigeration system comprises a primary circuit condenser, a primary circuit evaporator, a primary circuit compressor, and a fluid line defining a loop which fluidly connects said primary circuit evaporator to said primary circuit condenser through said primary circuit compressor such that said primary circuit compressor draws refrigerant in said fluid line from said primary circuit evaporator and pumps said refrigerant toward said primary circuit condenser, said positioning said heat exchanger comprising positioning said heat exchanger at said fluid line between an outlet of said primary circuit evaporator and an inlet of said primary circuit condenser.
22. The method of claim 21 wherein said positioning said heat exchanger comprises positioning said heat exchanger at said fluid line between said primary circuit compressor and said primary circuit condenser.
23. The method of claim 22 wherein said positioning said heat exchanger comprises positioning said heat exchanger at said fluid line at an outlet of said primary circuit compressor.
24. The method of claim 16 further comprising shielding said passive loop condenser from sun.
Type: Application
Filed: Jun 22, 2006
Publication Date: Feb 25, 2010
Inventors: Mark A. Fleming (Toronto), Alfred P. Brunger (Waterloo)
Application Number: 11/993,147
International Classification: F25B 41/00 (20060101); F25B 1/00 (20060101);