Plate Refrigeration Air System

Abstract

An air distribution system for a vehicle eutectic holdover refrigeration plate unit provides defined air passages with both the air inlets and the air discharge being positioned at the upper end of the plates. The air passages direct the air flowing through the plate construction in such a manner that substantially all of the plate surface is wiped uniformly by the moving air. The resulting design, wherein the holdover plates are contained in a housing open only at the top inlets and top discharge, has many practical operating advantages.

Description

SUMMARY OF THE INVENTION

This invention relates to a vehicle eutectic plate holdover refrigeration system and in particular to a means for moving air through such a system to provide more efficient cooling and more effective operation.

A primary purpose of the present invention is an eutectic plate system which can maintain the material being refrigerated at lower temperatures than heretofore possible.

Another purpose is an eutectic plate system utilizing a lower temperature eutectic for a greater plate-to-air temperature difference and a correspondingly greater cooling capacity.

Another purpose is an eutectic plate system including an improved air distribution means for wiping air more uniformly and at a higher velocity over the surface of refrigeration plates.

Another purpose is an eutectic plate system of the type described in which frost accumulating areas are readily accessible for inspection by the operator.

Another purpose is an eutectic plate system which takes into consideration the fact that the frost tends to accumulate at the inlet areas, leaving the outlet areas relatively frost-free.

Another purpose is an eutectic plate system of the type described in which most of the frost accumulates in those areas which are the first to defrost as frozen eutectic is depleted or as water defrosting is accomplished as taught in U.S. Pat. No. 3,727,422.

Another purpose is an eutectic plate system of the type described utilizing corrugated or extended surfaces to increase the effective heat transfer area for a greater cooling capacity.

Another purpose is an eutectic plate system in which the air discharge and air return are at the top of the plate system, adjacent the warmest air within the space being cooled.

Another purpose is an eutectic refrigeration system of a cold well configuration which prevents gravity air flow down through the unit and out of the bottom when the blower is off, thus eliminating danger of freezing product overnight and precluding waste of holdover refrigeration at a delivery stop when the truck body door is open.

Another purpose is an eutectic plate system utilizing squirrel-cage blowers to provide a high-velocity well-defined cold air stream that will travel the length of a long truck body.

Another purpose is an eutectic plate system of the type described utilizing a lower temperature eutectic and providing substantially colder air without any change in the compressor horsepower and negligible change in the BTU capacity by employing R-502 instead of R-12 refrigerant.

Another purpose is an eutectic plate system with the air inlet at the top instead of at the bottom which allows the space-saving stacking of product against the unit without blocking the air intake.

Another purpose is an eutectic plate system in which defrost water is directed to trapped drains within the confines of the unit.

Other purposes will appear in the ensuing specification, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated diagrammatically in the following drawings wherein:

FIG. 1 is a view of a eutectic holdover refrigeration system of the type described,

FIG. 2 is a section along plane 2--2 of FIG. 1, and

FIG. 3 is a partial vertical section illustrating the attachment of the blower to the plate cover.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates generally to an eutectic plate holdover system of the type shown in U.S. Pat. No. 2,875,595. In particular, the invention relates to an improved means for distributing air over the surface of the plates and to a design which allows the utilization of holdover plates with lower temperature eutectic, for more efficient cooling of the refrigerated space.

The plate structure shown includes an outer cover, generally indicated at 10, having sides 12 and 14, a back 16, a front 18, partially cut away in FIG. 1, and a bottom 20. The cover may conventionally be made out of sheet metal as is common in the refrigeration field. The front portion of the cover 18 may be insulated on the inside to prevent freezing of product that might be stacked in close proximity. The support structure for the plates and cover includes corner supports 22 and a pair of spaced bottom supports, one of which is indicated at 24 in FIG. 1. The support structure also includes generally centrally located upright braces 26, there being four such braces illustrated in FIG. 2.

Positioned within the cover are a plurality, in this case two, eutectic holdover plates indicated at 28 and 30. The plates may be similar to those shown in the above-mentioned patent and are supported on cross braces 27 mounted on bottom supports 24. The plates are positioned within the cover and so arranged relative to one another and to the cover to define vertically extending air passages between the plates and between the outside surfaces of the plates and the cover. As indicated in FIGS. 1 and 2, the central section of each of the plates may have an extended or corrugated area 32, positioned on each side of each plate, and suitably formed of aluminum or a material having suitable heat transfer characteristics. The oppositely-directed extended areas 32 of the plates 28 and 30 are in contact with one another to define a plurality of vertically-extending air passages indicated at 34 and 36. Attached to each of the vertical braces 26 are small seal members 38 which form a seal between the plate outer surfaces and the cover to define the outer air passages within the cover.

Centrally positioned at the top of the cover is an air discharge assembly 40, mounted at the upper end of the upright braces 26. On opposite sides of the discharge assembly 40, the top of the cover is open to provide air inlets or air intake openings indicated at 42. The air to be cooled will be drawn in through the openings 42, and will pass downwardly as indicated by arrows 44 in the space between the plates and the cover, indicated at 46 in FIG. 2, and in the space 48 between the plates, again as indicated in FIG. 2. Once the air has reached the bottom of the cover it will follow the paths of arrows 50 and will pass between the bottom of the plates and the bottom of the cover, and then start its upward path in the direction of arrows 52. When the air is moving upwardly toward the discharge assembly 40, it will be confined to the various small air passages 34 and 36 described above. When the air has reached the top of the cover, it will be discharged from the discharge assembly 40. In effect, the air has been confined to follow a predetermined path, from the air intake at the top, down the sides of the plates, and then up the center of the plates to the air discharge at the top. Of particular importance is the fact that both the air intake and the air discharge are at the upper surface of the plates and also that substantially the entire surfaces of the plates are wiped uniformly by the moving air.

The discharge assembly 40 includes a housing 54, having a hinged front door 56. The door 56 has a pair of discharge openings 58 positioned in front of squirrel cage blowers 59 and on opposite sides of dual shaft blower motor 60. The blower may be operated by suitable electric power, the details of which are not shown. However, it is important to note that a blower is used as the means for moving air through the plate system, rather than a propeller or fan-type blade.

In operation, air will be drawn in through the upper air inlets 42, and will be moved downwardly across the plate surfaces, as indicated by the arrows 44. Note that the air will be drawn generally directly down into the plates and thus will uniformly wipe substantial portions of the plates and will leave only rather minute areas at the lower outside corners of the plates in contact with slower moving air. When the air has reached the bottom, it will follow the paths of arrows 50 and will then flow upwardly with increased velocity across the extended areas 32, along the paths of arrows 52, and then outwardly through the air discharge openings 58, positioned at the top of the plate.

Prior holdover eutectic plate systems were so constructed that the air inlet was at the bottom and the air discharge was at the top. This was advantageous in that the cold air was discharged in the area of the warmest air, at the top of a truck body. However, a major disadvantage of such a system was that during periods when the blower was shut off by a thermostat, for example when the truck was sitting overnight with a full load, the cold air within the plate system flowed by gravity out of the bottom air inlet openings and oftentimes would freeze the product being stored adjacent the bottom openings. The present invention overcomes this disadvantage by having the air inlets at the top in alignment with the air discharge, thus creating a cold air trap within the cover. A major advantage which is obtained by the present arrangement, beyond overcoming the disadvantage described above, is that the air inlets pull in air from the warm strata adjacent the upper surface of the body being cooled, rather than pulling in the cool air at the bottom. In addition, by having the air inlets on opposite sides of the centrally positioned air discharge, as contrasted to the previous construction in which the air intake was at the bottom beneath the air discharge, the air is forced into the particular pattern shown in the drawings and thus almost the entire area of the plate surface is wiped uniformly by the moving air. In prior constructions in which the air intake was at the bottom, there could be substantial areas of the plate which received little or no moving air and thus were much less effective in the heat transfer process.

Of importance in the invention is the fact that the areas which initially receive the moist air to be cooled, the upper areas of the plates will accumulate most of the frost and are the areas which are easily visible to the operator. Thus, the operator can quickly determine when defrosting is necessary. In prior constructions the air inlet was adjacent hidden areas of the plate and hence the operator did not know when it was necessary to defrost the plates and thus could only guess. The moist air which is brought into the plate system will deposit most of its moisture where it first strikes the plates. Thus it is highly advantageous to have the air inlets in areas which are readily accessible to the operator so he can determine when it is necessary to start a defrosting operation. Also, defrosting begins at the top of the plates, thus the areas to be defrosted are the areas which will primarily receive defrosting liquid, if that is the process being used. In addition, the extended areas 32 will be relatively frost-free at all times because the air will be substantially dry when it reaches this portion of the plate. Thus, the last part of the air passages will be relatively frost-free and there will be a high degree of heat transfer as the air passes over the extended areas 32. It is advantageous to have such extended areas as they provide substantially increased surface for transfer of heat between the air and the plate surface. Although the extended surfaces are shown here in a corrugated configuration, it is understood that other configurations could be used for providing additional heat transfer surface.

The closed bottom provides a convenient trap for the defrosting liquid so that it may be removed in a suitable manner, and not out on the truck body floor.

The air circulation pattern within the truck body to be cooled will be at the particular strata where the warmest air is located. Thus, the air from the discharge openings 58 will be directed outwardly and by using a squirrel cage blower rather than a propeller fan, there will be a very carefully defined high velocity stream of cold air moving down the center of the body to be cooled. There will be an air circulation pattern in a horizontal strata with the cold air coming out of the center and the warm air being drawn along the sides toward the air intakes 42. It has been found that there is only about an 8.degree. dispersion with the use of a squirrel cage blower, as contrasted to the rather wide angle cone-shaped air pattern when a propeller is used to move air out of the plate unit. Thus, there is provided a confined high velocity stream of cold air moving out into the area to be cooled which will force warmer air along the sides of the body toward the air inlets 42.

Within the plate system, the velocity of the air is relatively constant in the downward flow air passages and increases in the upward flow air passage, as there are not obstructions and the air is rapidly moved over the entire plate surface.

The present invention has enabled the use of a substantially lower temperature eutectic than that previously used. For example, a zero degree eutectic is now possible and it is also advantageous to now use an R-502 low temperature condensing unit rather than the previously-used R-12 medium temperature condensing unit. This change in condensing units enables the operator to freeze the eutectic, to a lower temperature, in approximately the same length of time as was possible with a higher temperature eutectic, with no significant change in the BTU capacity and no change in the horsepower of the condensing unit.

The air discharge assembly 40 will normally be positioned at the top of the truck body being cooled. As shown in the drawings, it is positioned directly at the upper end of the plates, but this will not always be true. If there is sufficient space between the top of the plates and the top of the body being cooled, the discharge unit 40 may be connected by a suitable sheet metal conduit or the like so that it is positioned directly at the top of the body. In this way, the cold air will not be obstructed by any product being stored within the body and the very warmest air, that at the top of the body, will be drawn into the air inlets as it is moved aside by the cold air discharge.

It has been found that with the present invention it is possible to maintain the temperature of milk, as an example, in a truck body for a long delivery day at a maximum temperature of 40.degree., which is the temperature that at least one state is now prescribing as the maximum permissible milk delivery temperature. Delivery trucks, with constant opening of the truck door, create many problems for refrigeration systems. However, it has been found that the present system will maintain the milk temperature at a maximum fo 40.degree., and of will permit the refrigeration unit to be operated in an efficient manner.

With the use of a blower and carefully defined air passages, the velocity of air through the plate system is greatly increased, thus permitting the plate system to quickly reduce body temperature after a door opening. In addition, by having the cold air trapped within the cover, when the truck body door is opened and the blower is off, there will be no loss of cold air out the bottom and hence no waste of the stored refrigeration capacity.

Whereas the preferred form of the invention has been shown and described herein, it should be realized that there may be many modifications, substitutions and alterations thereto.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a vehicle eutectic plate refrigeration system, a cover, at least one eutectic plate positioned within said cover, said cover being closed on the bottom, sides, front and rear, an air inlet and an air discharge adjacent the upper end of said cover, power means positioned to force air out of said air discharge, and air passage means within said cover and associated with said plate defining air passages which extend from said air inlet adjacent the top of said cover, down along a portion of the plate to the bottom of the plate and then upwardly along a different portion of the plate to the air discharge, said air passage means being substantially coextensive with said plate whereby substantially all of the plate surface is wiped by air moving in said air passage means and the moving air is in contact with said plate through substantially its entire path from said air inlet to said discharge.

2. The structure of claim 1 further characterized in that the air discharge is located generally centrally with air inlets on either side of the air discharge.

3. The structure of claim 2 further characterized in that the downwardly and upwardly air passages within the cover are generally parallel.

4. The structure of claim 1 further characterized by and including a space beneath the plate and above the bottom of the cover forming a portion of said defined air passages.

5. The structure of claim 1 further characterized in that the air passage area directly below the air discharge is formed by generally parallel extended areas on said plate surface.

6. The structure of claim 1 further characterized in that there are a plurality of plates positioned within the cover, the air discharge being located generally centrally of the cover, and the plate portions directly below the air discharge having extended areas.

7. The structure of claim 6 further characterized in that the extended areas of adjacent plates are in contact with each other, with said contacting portions defining a plurality of generally parallel air passages directly below the air discharge.

8. The structure of claim 7 further characterized by and including seal means between the cover and the plates for defining a portion of said air passage means.

9. The structure of claim 1 further characterized in that said cover includes a discharge plate, forming said discharge opening, said power means including a blower attached to the back side of said discharge plate.

10. The structure of claim 9 further characterized in that said discharge plate is hinged to the cover.

11. The structure of claim 1 further characterized in that there are a pair of air inlets on opposite sides of the air discharge, said air discharge being positioned generally midway between said air inlets, and seal means positioned between the plate and cover dividing the space between the plate and cover into a plurality of separate parallel air passages.

12. The structure of claim 11 further characterized in that said seal means extend vertically from adjacent the plate bottom to adjacent the plate top.

13. The structure of claim 12 further characterized in that said seal means are generally in alignment with the inner portion of said air inlets.