The present invention relates to a refrigeration appliance comprising a zero degree (0°C) compartment with channels via which cool air is supplied to the zero degree compartment, where the dimensions of said channels and said zero degree compartment are optimized to ensure energy efficient cooling. It is well-known that a refrigerating appliance, such as a refrigerator operates based on the principles of the vapor-compression refrigeration cycle. Namely, cooling is performed by the refrigerant fluid, which is circulated between an evaporator, a compressor, a condenser and a tube expander (throttling device). While passing through the evaporator, the refrigerant fluid undergoes a phase transition from liquid phase into gas phase by way of absorbing the ambient heat of the refrigeration compartment. The cooled air around the evaporator is circulated back to the compartments where food items are preserved via a fan and cooling ports placed on the compartment's wall. A refrigeration appliance has a plurality of shelves and compartments for preserving food items. Two main compartments found in refrigerators are a freezing compartment (at -18°C) and a refrigerating compartment (at or below 4°C). Food items can decompose enzymatically, biochemically, microbiologically and/or physically. The speed and mechanism of decomposition is closely related to the temperature of the preservation environment. Especially perishables such as meat need to be preserved at near freezing temperatures. For this purpose current refrigerators comprise an additional compartment, referred to as a zero-degree compartment, which is kept at 0°C. High average temperatures (around 2.5°C to 3.5°C) and high heat release in zero- degree compartments are detrimental to the shelf lives of food items preserved in these compartments. Ensuring maintenance of 0°C conditions can extend the shelf life of food items two-fold and increase food safety and quality. To achieve sufficient cooling, zero degree compartments are generally placed below the compartment with the coolest air supply and are cooled by cool air flow directly into the compartment. Direct air flow causes higher heat release within the compartment and also causes food items to come in contact with dry air. It is necessary to close air outlets at the back of the compartment and direct air flow in such a way that it is only in contact with the outside walls of the compartment and cools the compartment indirectly to overcome this disadvantage. Among others, a prior art publication in the technical field of the invention may be referred to as EP1811251A2, which discloses a system and method for a refrigeration appliance comprising two or more compartments, where one compartment is a sub storage compartment, which is situated above the crisper compartment. The temperature of the sub storage compartment can be controlled independently from the other compartments and can be cooler or warmer than said other compartments. The sub storage compartment is indirectly cooled by cold air supply from evaporator via air ducts controlled by a damper and indirectly warmed by a heater. Heat transfer between the sub storage compartment and the other compartments is prevented by insulating member surrounding the sub storage compartment.

The present invention, on the other hand, addresses the situation where the shape and dimensions of the zero-degree compartment are optimized to ensure ideal storage conditions. To this end, the present invention provides a refrigeration appliance operating based on the principles of the vapor-compression refrigeration cycle; where said refrigeration appliance comprises at least two compartments and where at least one of said compartments is used as a zero-degree compartment. The zero-degree compartment comprises channels through which indirect cooling of the zero-degree compartment is achieved by cool air flow supplied to these channels from the evaporator. Cool air flow is regulated by adjusting evaporator fan speed according to evaporator surface temperature, thereby lowering heat release and preventing formation of condensation on the roof of the zero-degree compartment due to moisture release. Channel dimensions are optimized to ensure energy efficient cooling of the zero degree compartment.

The present invention provides a refrigeration appliance comprising a zero-degree compartment, the dimensions of which are optimized to ensure energy efficient cooling as provided by the characterizing features defined in Claim 1.

Primary object of the present invention is to provide a refrigeration appliance comprising a zero-degree compartment possessing channels via which cool air is supplied to the zero degree compartment from an evaporator, where the dimensions of said channels and said zero degree compartment are optimized to ensure energy efficient cooling.

Accompanying drawings are given solely for the purpose of exemplifying a refrigeration appliance with a zero-degree compartment, whose advantages over prior art were outlined above and will be explained in brief hereinafter.

The drawings are not meant to delimit the scope of protection as identified in the Claims, nor should they be referred to alone in an effort to interpret the scope identified in said Claims without recourse to the technical disclosure in the description of the present invention.

Fig. 1 demonstrates a refrigeration appliance with a zero-degree compartment according to the present invention. Fig. 2 demonstrates a lateral cross-sectional view of the refrigeration appliance according to the present invention.

Fig. 3 demonstrates a lateral cross-sectional view of the zero-degree compartment according to the present invention.

The following numerals are assigned to different part number used in the detailed description: 1) Refrigeration appliance

2) Storage cabin

3) Shelf

4) Zero-degree compartment

5) Extractable division

6) Extractable division cover

7) Top cover

8) Bottom cover

9) Top channel

10) Bottom channel

11) Rear channel

12) Shelf distance

13) Air flow port

14) Door shelf

The present invention proposes a refrigeration appliance (1) having a generally rectangular cross-sectional storage cabin (2). The refrigeration appliance (1) conventionally operates based on the principles of the vapor-compression refrigeration cycle such that cooling is achieved by circulation of a refrigerant through a compressor, a condenser, a tube expander and an evaporator, where said refrigeration appliance (1) comprises a plurality of shelves (3) and compartments and where at least one of said compartments is used as a zero-degree compartment (4). Said zero-degree compartment (4) is placed within the storage cabin (2) to be positioned below the lowermost portion of the evaporator level in the proximity thereof. As is known to the skilled reader, the evaporator (not shown) extends in perpendicular to the base of the refrigeration appliance (1) in parallel with the rear surface of the cabin. More particularly, the zero-degree compartment (4) is configured to be at the lower portion of the fresh food compartment below several shelves (3) and below the evaporator's lowermost tubes. In this configuration, there still exist additional space for an extractable division (5) for fruits and vegetable at the lowermost portion of the storage cabin (2) below said zero-degree compartment (4). The extractable division (5) has an extractable division cover (6) and said zero- degree compartment (4) is enclosed by top and bottom covers (7, 8) at both vertical sides thereof. During compressor ON/OFF and fresh food defrost cycles, the temperature of said zero-degree compartment (4) is regulated by adjusting evaporator fan speed according to evaporator surface temperature, thereby lowering heat release and preventing unwanted heating of the storage cabin (2). Zero-degree compartment (4) is indirectly cooled from its bottom, rear and side walls by cool air flowing into channels placed along said walls supplied from evaporator. The dimensions of said channels, i.e. top channel (9), bottom channel (10), rear channel (11) as well as shelf distance (12, (d)), height (H) of zero-degree compartment (4) and height (h) and width (w) of air flow port (13) and ratios thereof are optimized to prevent formation of condensation on the roof of the zero-degree compartment (4) and ensure energy efficient cooling of the same. The shelf distance (12, (d)) is defined as the distance between a door shelf (14) and the zero-degree compartment (4). Within the context of the present invention, cool air leak refers to cool air flow to top channel (9) and directly into zero-degree compartment (4). Direct air flow trough said top channel (9) causes food items to come in contact with dry air. Therefore, the vertical dimension c of the top channel (9) should be kept at a substantially reduced amount only to allow cool air leak to prevent condensation on the top cover (7). According to the present invention, it is established that keeping h:H ratio constant, different d values have a negligible effect on cool air leak flowrate. It is found that as d is increased, cool air leak flowrate is decreased. For this reason, d:a is configured to be greater than 1: 1. Here, a is defined as the distance between the zero-degree compartment (4) and the inner rear wall of the storage cabin (2), where said air flow port (13) is present. As air flow port (13) is level with bottom channel (10) for h:H ratios up to 1:5, cool air flows straight through rear channel (11) and cool air leak flowrate decreases in this interval. Cool air leak flowrate is constant for h:H between 1:5 and 1: 1.25. For h:H ratios above 1: 1.25 cool air leak flowrate increases as air flow port becomes level with top channel (9) and a serious amount of cool air flow is directed into said top channel (9) to come in contact with food items stored therein. For these reasons h:H ratio is configured to be smaller than 1:3.

Keeping cool air flowrate constant, changing h:H from 1:4 to 1:2 causes heat transfer along rear channel (11) to drop 5.5 W. Upon entering rear channel (11) from air flow port (13), cool air flow makes direct contact with rear wall of the zero-degree compartment (4) and heat exchange takes place between the two. As cool air flow entering rear channel (11) from air flow port (13) placed at h:H ratio of 1:2 has a greater surface of rear wall to come into contact with before being directed to bottom channel (10) than h:H ratio of 1:4, it is observable that a higher amount of heat transfer occurs between cool air flow and rear wall for h:H ratio of 1:2 than h:H ratio of 1:4.

Experimental results show that h:H ratio of 1:4 provides better cooling from bottom wall and promotes temperature uniformity between bottom wall and rear and front walls. Since flowrate along rear channel (11) is decreased, bottom wall must be cooled more efficiently. According to these results, h:H is configured to be between 1: 10 and 1:3 for most efficient cooling from bottom channel (10).

Assuming laminar flow, volumetric flowrate of cool air is dependent on height (H) of zero-degree compartment (4) and width (w) of air flow port such that:

If w:H is between 0.15 and 0.25, then h:H is configured to be between 0.1 and 0.8; If w:H is between 0.25 and 0.35, then h:H is configured to be between 0.2 and 0.7.

To ensure the cool air aimed at rear wall of zero-degree compartment (4) by air flow port (13) is directed towards bottom channel (10), a is configured to be greater than b. b is defined as the vertical dimension of the bottom channel (10). In addition, c:d ratio is configured to be greater than a:b ratio to ensure natural flow. In the present invention, a:b ratio must be between or equal to 3: 1 and 1: 1.

Since d is greater than a and a is greater than b, it follows that d is greater than b.

In one embodiment of the present invention, a refrigeration appliance (1) comprising a storage cabin (2), a compressor, a condenser, a tube expander and an evaporator such that cooling of said storage cabin (2) is effectuated by circulation of a refrigerant through said compressor, condenser, tube expander and evaporator, said refrigeration appliance (1) further comprising a zero-degree compartment (4) with a top channel (9), a bottom channel (10) and a rear channel (11) in said storage cabin (2). said zero-degree compartment (4) is indirectly cooled from its bottom, rear and side walls by cool air supplied from said evaporator flowing into said top channel (9), bottom channel (10) and rear channel (11) placed along said walls in the manner that the ratio of a shelf distance (12) over the distance between the zero-degree compartment (4) and an inner rear wall neighboring said rear channel (11) is greater than 1, said shelf distance (12) being defined as the distance between a door shelf (14) and the zero-degree compartment (4).

In a further embodiment of the present invention, the ratio of the height of an air flow port (13) over the height of said zero-degree compartment (4) is configured to be smaller than 1:3, said air flow port (13) being disposed on said inner rear wall of the storage cabin (2).

In a further embodiment of the present invention, the ratio of the height of the air flow port (13) over the height of said zero-degree compartment (4) is configured to be between 1: 10 and 1:3.

In a further embodiment of the present invention, if the ratio of width over height of the air flow port (13) is between 0.15 and 0.25, the ratio of the height of the air flow port (13) over the height of said zero-degree compartment (4) is configured to be between 0.1 and 0.8.

In a further embodiment of the present invention, if the ratio of width over height of the air flow port (13) is between 0.25 and 0.35, the ratio of the height of the air flow port (13) over the height of said zero-degree compartment (4) is configured to be between 0.2 and 0.7.

In a further embodiment of the present invention, said zero-degree compartment (4) is placed within the storage cabin (2) to be positioned below the lowermost portion of the evaporator level in the proximity thereof.

Therefore, a refrigeration appliance (1) comprising a zero-degree compartment (4) is proposed such that channels via which cool air is supplied to the zero-degree compartment (4) have dimensions and ratios thereof optimized to ensure energy efficient cooling.