GB2263539A - An evaporator for a refrigerated cabinet - Google Patents

Abstract

An evaporator (70) of a refrigerated cabinet has leading edges of its parallel fins (71, 72, 73) staggered so as to diminish problems arising from frost build-up on that leading edge. The cabinet includes a cooler (60) to remove moisture circulating in the air flow. <IMAGE>

Description

REFRIGERATED CABINET This invention relates to a refrigerated cabinet having an opening for accessing the interior of the cabinet, which opening is constantly shielded by an air curtain to prevent free air flow between inside and outside the cabinet.

Refrigerated cabinets having an opening for free access to items kept refrigerated inside the cabinets are widely used in, e.g. food shops and supermarkets. The opening of such a cabinet is shielded by an air curtain which is formed by continuously blowing air from one edge of the opening to an opposite edge. Such an air curtain is usually formed by different layers of air flow at different temperatures so that the outer layer of the air curtain may be at ambient temperature while the inner layers may be made colder and colder toward the interior of the cabinet. The different temperatures of these layers are maintained by circulating the air of different layers via different paths. In this way, the temperature inside the cabinet can be kept stable and well below O"C.

Since the innermost layer of the air curtain is formed by an air flow of very low temperature, such as -20 C - 30 C, which needs to be continuously circulated and refrigerated in a separated circulating path to maintain its temperature, during this process of circulating, if no precautions were taken, frost would accumulate which will reduce the efficiency of the system and even block the whole circulating path. A precaution which has been taken is the use of a preliminary cooler in that air flow, to dehumidify it before it reaches subsequent evaporator(s) which are to bring it to its final temperature.However, that cooler is not completely effective.' According to a preferred embodiment of the present invention, there is provided a refrigerated cabinet having means for providing a circulatory air curtain for shielding an access opening of the cabinet; comprising: means for circulating air along a path formed inside the cabinet to provide the air flow forming the air curtain; a cooler for dehumidifying the air of at least an innermost layer of the air flow upstream in the circulating path flow of an evaporator for refrigerating the dehumidified air; wherein the evaporator comprises a plurality Qf heat-exchanger fins arranged parallel with one another to define air flow in a part of the circulating path, and the space between the fins reduces along the direction of the air flow.

Preferably staggered leading ends of the fins form a single or multiple V-shaped formation with the opening of the or each V-shaped formation facing the direction of air flow.

Preferably, the cabinet is an upright one with its access opening formed at one side.

Preferably there is a second refrigerating means defining a second part of the circulating path downstream relative to said refrigerating means. This may have the same conformation as the first one, but will usually be conventional.

More specifically, in operation, when the air flow forming the innermost internal layer of the air curtain enters the circulating path, most of the moisture carried by the air flow will be deposited as frost on the dehumidifying means, (which can be regularly defrosted to get rid of the frost accumulation), and the air will become colder and drier. The dehumidified air will then meet the leading ends of fins formed on the refrigerating means. Since the temperature of the fins is lower than that of the air, the air will be further refrigerated.

During this process, most of the remaining moisture in the air will become frost on the front ends of these fins. Because of the arrangement of the fins, there is more space at the leading ends of the fins which can accommodate the frost formed by moisture in the air flow.

The air can flow through this staggered area and be further refrigerated by the closer-spaced trailing part of the fins. By this arrangement, the efficiency of the system is further improved and the chance of blockage caused by accumulated frost has been significantly reduced.

One embodiment of the invention will be described with accompanying drawings in which: Fig. 1 shows a side elevation view of an embodiment of the present invention; Fig. 2 shows a perspective view of the arrangement of the fins of an evaporator shown in Fig. 1; and Fig. 3 shows a side view of the arrangement of the fins.

Fig. 1 shows an embodiment of the refrigerated cabinet of the present invention. The cabinet 10 has an upright configuration with an opening 20 at one side.

Anything kept inside the cabinet 10 is readily visible and accessible via this opening 20. The temperature inside the cabinet is kept well below 0 C by an air curtain 30 which is formed by three layers 31, 32 and 33 of continuous air flow. The three air flow layers represented by arrows 31, 32 and 33 follow different routes or paths so that they are kept at different temperatures. The first air layer 31 is of ambient air driven by a fan 51 via a path 41, and it flows to the lower edge 21 of the opening 20 outside the cabinet. The second layer 32 is driven by a fan 52 to circulate in a path 42 within the cabinet and the temperature of the air is reduced by its contact with outer walls of the Inner part of the cabinet. The innermost air layer 33 is circulated via a path 43.The air flow of this layer enters the body of the cabinet at the lower edge 21 of the opening 20. Along this path 43 from the entrance position at the edge 21, there are arranged a cooler 60, a fan 53, a first refrigerating evaporator 70 and a second refrigerating evaporator 80. The air from the layer 33 is cooled by the cooler 60. At this point, most of the moisture picked up by the air flow will become frost deposited on the cooler 60. The dried and cooled air is driven by the fan 53 to the first evaporator 70 and then the second evaporator 80. The temperature of the air is further reduced by the heat exchange between the air and fins fixed to the evaporators 70 and 80; the arrangement of the fins on the evaporator 70 will be fully described below.After the air has passed through the evaporator 80, its temperature is fully reduced and then it is blown out from the top edge of the opening 20 to form the innermost layer 33 of the air curtain 30.

During the operation of the cabinet, the cooler 60 is regularly defrosted so as to avoid any blocking of the system and to keep the system working efficiently.

However, there will still be some moisture in the air stream after the cooler, and this will tend to deposit as frost on the leading edge of the first evaporator 70; Fig. 2 shows the arrangement of the fins 71, 72 and 73 on the evaporator 70 shown in Fig. 1. The evaporator 70 has a plurality of heat-exchange fins arranged parallel with one another and with the air flow; the spaces between the fins form part of the air circulating path 43 shown in Fig. 1. The front ends of the fins are staggered so that there are three groups of fins 71, 72 and 73 of different lengths. As shown in Fig. 3, the space between the two fins 71 is much larger than that between fins 72, while at the downstream ends of the fins 71, 72 and 73, the spaces between them are least.In this arrangement, the air from the cooler 60 shown in Fig. 1 is first introduced and refrigerated at the comparatively wide space between the leading ends of fins 71. As the temperature of the air is further reduced, the remaining moisture carried by the air will become frost and the air will become drier. Then the air flows to the space between the fins 71 and 72 and farther down to the even narrower space defined by the fins 73. As the space between the fins becomes smaller and smaller, the heat-exchange efficiency is increased. On the other hand, since the moisture in the air has become frost in the early stages of its passage through the evaporator, there is little chance for any frost to block the space between the fins, at their downstream portions. By this arrangement of the fins in which the spacing between them reduces in the direction of air flow, the system can work at higher efficiency with reduced risk of blocking by frost.

Another evaporator 80 may be arranged downstream the evaporator 70. Since the air leaving the evaporator 70 has been dried, the arrangement of the fins of evaporator 80 can be conventional, without loss of heat-exchange efficiency.

Claims (7)

1. A refrigerated cabinet having means for providing a circulatory air curtain for shielding an access opening of the cabinet; comprising: means for circulating air along a path formed inside the cabinet to provide the air flow forming the air curtain; a cooler for dehumidifying the air of at least an innermost layer of the air flow upstream in the circulating path flow of an evaporator for refrigerating the dehumidified air; wherein the evaporator comprises a plurality of heat-exchanger fins arranged parallel with one another to define air flow in a part of the circulating path, and the space between the fins reduces along the direction of the air flow.

2. A refrigerated cabinet according to claim 1 wherein the reduction in space is achieved by staggering the leading ends of the fins in the direction of air flow.

3. A refrigerated cabinet according to claim 2 wherein the leading ends are in a repeated V-shaped formation.

4. A refrigerated cabinet according to any one of the preceding claims wherein the said evaporator is a first evaporator and there is a second evaporator in the air path downstream of the first.

5. A refrigerated cabinet according to claim 4 wherein the second evaporator is also a said evaporator.

6. A refrigerated cabinet according to any one of the preceding claims which is one with its access opening at a side.

7. A refrigerated cabinet substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.