TECHNICAL FIELD The present invention relates to refrigerators, for storing chilled or frozen goods, which are adapted for reduced energy consumption.

BACKGROUND Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.

Figure 1 illustrates a commercial vapor compression refrigerator 30 as may be found in supermarkets and other situations where it is necessary to store refrigerated goods such as frozen or chilled food. The refrigerator 30 includes an insulated cabinet 36 that is fronted by glass display doors 38a,.., 38d, which locate into a surrounding fascia 37. The cabinet 36 contains a brine-to- air heat exchanger 10, or as it is variously referred to in the following "a cabinet exchanger" through which a chilled solution flows. The cabinet exchanger 10 draws heat out of the air within the cabinet 36 thereby keeping the cabinet at a desirably low temperature for storing the chilled or frozen goods. Beneath the cabinet 36 there is located a refrigeration equipment area 40 which provides room for a refrigerant assembly 32 and also for a brine chiller assembly 34. As will be explained further shortly, the brine chiller 34 operates to assist in condensing the refrigerant of the refrigerant assembly 32 and so improves the efficiency of the refrigerant assembly. The actual refrigerant that is used may be selected from any one of a number of commercially available substances. For example R-404A refrigerant might be used though it will be realized from the following that the type of refrigerant that is selected is not critical to the invention. Figure 2 is a block diagram of the refrigerator 30. The refrigerator 30 includes a pump 8 for pumping brine 9a from a container in the form of tank 9 through a first side 1 a of a heat exchanger 1 , wherein the brine is cooled. The cooled brine is then forced through tube 20 into an inlet side 15a of cabinet exchanger 10. Cabinet exchanger 10 draws heat from the air within the cabinet 36 into the brine thereby warming the brine as it passes through the cabinet exchanger 10. The warmed brine leaves the outlet side 15b of cabinet exchanger 10 via tube 21 and is returned to the first brine storage tank 9 from whence the cooling cycle repeats.

In order to remove heat from the brine in heat exchanger 1 there is provided a refrigerant vapor compression system 32. The system 32 consists of a second side 1 b of the heat exchanger 1 , the output of which is coupled to a compressor 2. The compressor 2 acts to elevate the pressure and by doing so also elevates the temperature of the refrigerant. The compressed refrigerant is then passed through a first side 3a of a second heat exchanger 3. The second heat exchanger 3 draws heat from the compressed refrigerant and causes it to condense to a liquid. The pressurized liquid refrigerant leaves the heat exchanger 3 and passes through an expansion valve or "throttle" 5 which causes the refrigerant to vaporize and undergo a drastic temperature drop. The cold refrigerant then passes through the second side 1 b of the first heat exchanger 1 thereby drawing heat from the brine that is passing through the first side 1 a of heat exchanger 1 and then proceeding along line 20.

The cold side 3b of the refrigerant heat exchanger 3 has brine circulating through it by means of a pump 12 that draws cooled brine from a second brine tank 13. As the brine is forced by pump 12 through the second side 3b of second heat exchanger 3 it draws heat from the refrigerant coming from compressor 2 that is passing through the first side 3a of the second heat exchanger 3. The heated brine that emerges from the second side 3b of heat exchanger 3 is cooled to near-ambient air temperature by radiator 14. The cooled brine from the radiator 14 is then transferred via pipe 17 to the second brine tank 13. A problem that occurs with refrigerator freezers and chillers in general and particularly with commercial units is that over time ice builds up on the cabinet exchanger 10. As the ice builds up the efficiency of the cabinet exchanger 10 deteriorates and so the air within the cabinet 36 is no longer cooled to its target temperature. Consequently, it becomes necessary to defrost the cabinet exchanger 10.

A typical arrangement for performing the defrost is an electric heating filament 42. The heating filament 42 is located in proximity to the cabinet exchanger 10 and by passing electric current through the filament it becomes hot and defrosts the cabinet exchanger. However, electrically defrosting the cabinet exchanger 10 consumes a substantial amount of energy and it would be desirable if there were a better way for performing a defrost that did not consume so much energy.

It is an object of the present invention to provide a refrigerator with improved energy efficiency.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a refrigerator including:

a cabinet for storage of goods to be chilled or frozen;

a cabinet exchanger located within the cabinet and coupled to a refrigeration assembly having a number of valves, the valves being arranged to switch the refrigeration assembly between a cooling configuration and a defrost configuration;

wherein in the cooling configuration the valves place a chilling fluid in fluid communication with the cabinet exchanger for passage therethrough and wherein in the defrost configuration the valves place a warming fluid in fluid communication with the cabinet exchanger for passage therethrough for defrosting the cabinet exchanger. Preferably the refrigeration assembly includes a first container for storing the chilling fluid therein and a second container for storing the warming fluid therein. It is preferable that at least some of said valves are arranged to divert fluid exiting the cabinet exchanger to either the first container or the second container.

In a preferred embodiment of the invention the refrigerator includes a controller wherein at least some of the valves are responsive to the controller for diverting cool fluid from the cabinet exchanger to the first container and warmer fluid from the cabinet exchanger to the second container.

Preferably the controller comprises a temperature sensor arranged to sense temperature of fluid at an outlet side of the cabinet exchanger and wherein the at least some valves responsive to the temperature sensor are arranged to divert the fluid to the second tank upon the temperature sensor indicating the fluid at the outlet side exceeding a predetermined threshold. Alternatively the controller may comprise a time delay or timer assembly that diverts the fluid to the second tank after a delay sufficient to flush cold fluid from the cabinet exchanger and prior to warmer defrosting fluid leaving the cabinet exchanger. In a preferred embodiment of the invention the refrigerator includes:

the first container;

a first heat exchanger;

a first pump arranged to pump cooling fluid from the first container, through a first side of the first heat exchanger;

a first tube for conveying fluid from an outlet of the first side of the first heat exchanger to an inlet of the cabinet exchanger;

a first valve of the number of valves arranged to selectively open and close the first tube; a second tube connected between the outlet of the first side of the first heat exchanger and the first container;

a second valve of the number of valves arranged to selectively open and close the second tube;

whereby upon opening the first valve and closing the second valve, cooling fluid is transferred to the inlet of the cabinet exchanger and whereby upon closing the first valve and opening the second valve cooling fluid is returned from the outlet of the first side of the first heat exchanger to the first container.

Preferably the refrigeration assembly includes;

a second heat exchanger having a first side that is coupled to a second side of the first heat exchanger for drawing heat from the first side of the first heat exchanger.

The refrigeration assembly preferably includes;

the second container;

a second pump arranged to pump fluid from the second container through a second side of the second heat exchanger;

a radiator having a fluid inlet side coupled to an outlet of the second side of the second heat exchanger by a third valve of the number of valves, the radiator having a fluid outlet side coupled to the second container; and a fourth valve of the number of valves coupled between a point between the outlet of the second side of the second heat exchanger and a point between the first valve and the inlet of the cabinet exchanger;

wherein closing the third valve and opening the fourth valve diverts warming fluid from the second container through the second side of the second heat exchanger and thence to the inlet of the cabinet exchanger for defrosting thereof.

In a preferred embodiment of the invention the refrigerator includes a fifth valve of the number of valves and a sixth valve of the number of valves in parallel with an outlet of the cabinet exchanger; wherein the sixth valve is disposed between the outlet and the second container and wherein the fifth valve is disposed between the outlet and the first container whereby alternative opening and closing of the fifth and sixth valves diverts fluid from the outlet to either the second container or the first container. It is preferred that the fifth valve and the sixth valve are responsive to a temperature sensor for the outlet of the cabinet exchanger.

In the preferred embodiment of the invention the refrigerator includes a second heat exchanger in fluid communication with the second tank via a pump wherein in the defrost configuration the valves divert fluid from the second heat exchanger to an inlet side of the cabinet exchanger.

Preferably the refrigerator includes a container to collect condensation from components of the refrigerator and tubing located for heat exchange with condensation collected in the container, wherein the tubing is in fluid communication with a hot side of the second heat exchanger for heat exchange between condensation collected in the tray and the fluid from said heat exchanger to thereby cool the fluid from the second heat exchanger. The refrigerator may include tubing arranged to circulate fluid from the second heat exchanger around a fascia of the refrigerator to thereby reduce condensation forming thereon.

According to a further aspect of the present invention there is provided a refrigerator that includes fascia tubing arranged to circulate fluid warmed by a heat exchanger of the refrigerator about a fascia of the refrigerator to thereby reduce condensation forming thereon.

For example, in a preferred embodiment of the invention the the fascia tubing is connected between an outlet of a first side of the heat exchanger of the refrigeration assembly and an inlet of a radiator of the refrigeration assembly. BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

Figure 1 shows a refrigerator which includes a prior art defrosting assembly.

Figure 2 is a block diagram of the refrigerator of Figure 1 .

Figure 3 is a block diagram of a refrigerator according to a preferred embodiment of an aspect of the present invention.

Figure 4 is a block diagram corresponding to that of the refrigerator of Figure 3 in a defrosting configuration.

Figure 5 is a block diagram of a refrigerator according to a further embodiment of the present invention.

Figure 6 is a block diagram of a refrigerator according to a further embodiment of the invention wherein heated fluid is passed through tubing of a fascia of the refrigerator cabinet to reduce condensation forming on glass doors of the refrigerator.

Figure 7 depicts a further embodiment of the invention which incorporates features of the embodiments of Figures 3 and 6. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to Figure 3, there is depicted a block diagram of a refrigerator 50 according to a preferred embodiment of the present invention. The refrigerator 50 has some components in common with the system illustrated in Figure 2, and so like item numbers will be used in the Figures where appropriate. The refrigerator 50 includes an insulated cabinet 36 that is fronted by glass display doors 38a,..,38e, which locate into a surrounding fascia 37. Refrigerator 50 includes a brine tank equalization tube 33, which ensures that the levels in the first and second brine tanks 9 and 1 3 are equal and prevents either of them from overfilling or running dry. The refrigerator 50 also includes a number of solenoid actuated flow valves S1 , ... ,S6 which are under the control of a suitably programmed Programmable Logic Controller (PLC) and user interface 52. Whilst a PLC is used in the presently described embodiment of the invention other controllers such as microprocessor or even a Field Programmable Gate Array (FPGA) might be used and the invention is not limited to the use of a PLC. As will be explained, the solenoid valves S1 , ... ,S6 may be operated by the PLC 52 to change the configuration of the refrigerator 50 from a cooling configuration, such as as illustrated in Figure 2, to a defrost configuration, as illustrated in Figure 4. It is also conceivable, though less desirable that a manual system be provided wherein the valves are manually operated. In the defrost configuration the solenoid valves S1 , ... ,S6 are variously opened and closed to pump fluid, namely warmed brine from the second side 3b of heat exchanger 3 through the cabinet exchanger 1 0, thereby causing it to defrost.

Referring again to Figure 3, the states of the solenoid valves during the normal cooling cycle and during the defrost cycle may be summarised as follows in Table 1 :

Table 1

In addition, the PLC 52 may be programmed to control S1 and S2 to alternatively open and close during the cooling cycle in order to keep cooling the fluid that is stored in tank 9. For example, when S1 is closed and s2 is opened then cooled fluid is returned from the output of first side 1 a of heat exchanger 1 via tube 22b to tank 9. Alternatively, when S1 is opened and S2 is closed then cooled fluid proceeds through S1 , through tube 22a to the inlet 15a of cabinet exchanger 10.

When it is determined that defrosting is required then S3 is closed and S4 is opened. Closing S3 and opening S4 allows the warm fluid exiting the second side 3b of heat exchanger 3 to enter the inlet side 15a of the cabinet exchanger 10 and pass therethrough, thereby warming and defrosting the cabinet exchanger 10. The fluid then exits the outlet side 15b of the cabinet exchanger 10 through tube 21 .

At the same time that S3 is closed and S4 is opened, S1 is closed and S2 is opened, thereby recirculating brine from brine tank 9, through pump 8, through the first side 1 a of the first heat exchanger 1 and then back to the first brine tank 9. PLC 52 is responsive to a temperature sensor 27 that is mounted adjacent the outlet side of the cabinet exchanger 10 for monitoring the temperature of fluid leaving the cabinet exchanger 10 through tube 21 . Once the temperature sensor 27 has detected that the brine exiting the cabinet exchanger 10 is above a threshold level then PLC 35 closes s5 and opens s6. This ensures that the cooler brine that was initially in the cabinet exchanger 10 prior to commencement of the defrost cycle is saved to the first brine tank 9 and the subsequent warmer brine is conveyed to the second tank 13. The first brine tank 9 contains brine that is substantially cooler than the brine that is collected in the second brine tank 13 during defrost. Alternatively, rather than monitor the temperature the PLC 52 may be programmed to implement a time delay or timer that operates the solenoid valves to divert the fluid to the second tank only after a delay sufficient to flush cold fluid from the cabinet exchanger 10 and prior to warmer defrosting fluid leaving the cabinet exchanger 10.

By saving the cooler brine in tank 9, and ensuring that the following warmer defrost brine is diverted to second tank 13, there is an energy saving since when the cooling cycle recommences the brine in tank 9 will not have to be cooled as much as would be the case if it were simply dumped to the second tank 13 or if warmer defrosting fluid had been allowed to enter the first tank 9. In one embodiment the volume of fluid in the cabinet exchanger 10 is about six litres which is a considerable amount to cool or heat. Once s5 has closed and s6 opened the warmer brine exiting during defrost is returned to the second brine tank 13. It will then be returned by pipe 18 to pump 12 from whence it is discharged through pipe 19 back into the second side 3b of heat exchanger 3 where it is recirculated to the inlet side 15a of the cabinet exchanger 10 so that the defrost cycle continues.

It will be realised that the defrost system that is illustrated in Figure 3 makes use of heat from the heat exchanger 3 for defrosting so that waste heat, rather than electrical heating is used. Referring now to Figure 5, there is shown a further embodiment of the refrigerator 50 wherein a tray 7 is provided. Although not illustrated in Figure 5, the embodiment of Figure 5 includes the cabinet 36 that is shown in Figures 3 and 4. The chilled brine pump 8, primary heat exchanger 1 , compressor 2, second heat exchanger 3 and cooling fluid pump 12 may be mounted upon the tray 7. The tray 7 is arranged for heat conduction with a serpentine copper tube 58. For example, the copper tube may be located adjacent a base of the tray. The serpentine tray tube 58 is coupled by tubes 56 and 60 between the hot output of the second side 3b of the second heat exchanger 3 and the inlet side of the radiator 14 via solenoid valve S3. During the normal cooling cycle condensation drips into the tray 7 from the cabinet heat exchanger 10 via collection tube 62. Condensation may also drip into the tray from the cold sides of the primary heat exchanger 1 and the second heat exchanger 3 and from the expansion device 5 and associated tubing. Accordingly, during the cold cycle the tray 7 tends to collect cool condensate which cools the serpentine tray tube 58 and so assists in cooling the hot fluid from the second heat exchanger 3 prior to it entering radiator 14 via solenoid valve S3. Furthermore, the hot fluid flowing through the tray tube 58 may assist in evaporating off the condensation that is collected in the tray 7. In this way energy consumption is further reduced as the radiator 14 need not work as hard as it would otherwise have to if cool condensate were not collected in tray 7. Referring now to Figure 6, there is depicted a further embodiment of an aspect of the invention wherein heated fluid leaving the second heat exchanger 3 is diverted through tubing 50 prior to entering the radiator 14.

The tubing 50 is disposed about fascia 37 of the cabinet so that in use it distributes the warmed fluid from heat exchanger 3 and warms the fascia. The warming of the fascia assists in reducing condensation forming. The formation of condensation is undesirable. The tubing 50 may be provided in conjunction with the electrically defrosted system of Figure 2. Alternatively, Figure 7 shows the fascia warming arrangement in combination with the embodiment of the invention that is illustrated in Figure 3. The fascia warming arrangement may also be provide in combination with the tray arrangement that is illustrated in Figure 5.

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. The term "comprises" and its variations, such as "comprising" and "comprised of" is used throughout in an inclusive sense and not to the exclusion of any additional features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect.

The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

Throughout the specification and claims (if present), unless the context requires otherwise, the term "substantially" or "about" will be understood to not be limited to the value for the range qualified by the terms. Any embodiment of the invention is meant to be illustrative only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.