IL43392A

IL43392A - Transportable refrigeration apparatus

Info

Publication number: IL43392A
Application number: IL43392A
Authority: IL
Original assignee: Thermo King Corp
Priority date: 1972-10-26
Filing date: 1973-10-05
Publication date: 1977-02-28
Also published as: DE2353098A1; ZA737713B; BR7308287D0; AU6116873A; JPS4988344U; IL43392A0; GB1445882A; ES419847A1; FR2204519A1; JPS5037544Y2; US3792595A; FR2204519B1; IT997416B; CA998254A; BE806431A; IN141159B

Description

Transportable refrigeration apparatus THERIIO KING CORPORATION C, 41566 This invention relates to a transportable refrigeration unit or cargo container for perishables.

It is well known in the art of transpor ation refrigeration that the storage and transportation of perishable foodstuffs, such as fresh produce, vegetable and the like, require a rather constant and accurate control of the atmospheric conditions existing in the cargo space or storage compartment containing the perishables as they are being transported from one location to another, sometimes over long distances involving radical changes in climates, and cargo carriers intended for use in transporting perishables usually are specifically designed with a view to meeting this requirement. Thus, the U.S. patent specification No. 3,612,093 discloses a refrigeration arrangement for a vehicle used in transporting foods, particularly meats and vegetables, wherein liquid nitrogen or another cryogenic medium is supplied from tanks to a plurality of heat exchanger and venturi units disposed adjacent the ceiling of the cargo compartment. In each heat exchanger and venturi unit, the liquid nitrogen supplied thereto is vaporized through expansion and with heat extracted from the compartment atmosphere sucked into the units through venturi action therein, as a result of which the portion of the atmosphere thus passing through the respective heat exchanger and venturi unit is . cooled before being returned to the compartment.. The heat exchanger and venturi units are also connected to a duct system for introducing sufficient air from the outside into the cooled gas to maintain the nitrogen- to-air ratio required to prevent spoilage of the cargo, a desired ratio being given i the above-mentioned specification as 95% of nitrogen within the compartment to 5% of air introduced. The supply of air is controlled by means of a mechanicall adjustable shutter arrangement, and the suppl of nitrogen from the tanks to the heat exchanger and venturi units is regulated by means of thermostatically controlled valves. .

. . . . Another refrigeration arrangement for preserving foodstuffs while in transit is described in U.S. patent specification No . 2 , 780 , 923. This conventional system, in-stead of providing, refrigeration through the expansion of nitrogen introduced into the compartment' atmosphere, employs the well-known compression cycle involving the use of a refrigerant compressor, condenser, expansion device, and evaporator, all connected together to form a closed refrigerant-flow circuit. In accordance with- this prior patent specification, air from the cargo space is moved, upon operation of a fan or fans, into a duct and through the evaporator structure where. heat is extracted from the air, and is then returned to the cargo space through ductwork leading from the evaporator structure to re-entry openings located at various points distant therefrom, the flow of air being con-trolled by damper mechanisms, and the refrigeration cycle, in the usual manner, by t he rmos t a t i cally . con t ro lied switches and valves.

One of the problems encountered with transportable refrigeration units of the above-mentioned types used in transporting perishable foodstuffs, especially fresh produce, has become known in the art as "top freezing". Produce and vegetables preferably are kept at temperatures which, are near the freezing point, of the perishables but still above it, since freezing. of fresh produce in transit will hasten spoilage thereof. Top freezing is usually the consequence of thermal stratification due to an uneven distribution of cooling gas in the cargo compartment, and it is most likely to occur in the regions where the cooled gas enters the cargo space, i.e. where it emanates from the heat exchanger and venturi units, as in U.S. specification 3,612,093, or from the re-entrance openings, as according to U.S. specification 2 , 780, 92.3, since, obvious ly ,. the entering gas is coldest and has the highest flow velocity near its points of entry.

It is the principal object of the invention to alleviate the problem of top freezing, and to provide for an even cooling-gas distribution and a more uniform temperature throughout a- cargo space without the need for complex controls and bulky, space-consuming ductwork.

. The invention .accordingly resides broadly in a transportable refrigeration unit for preserving perishables, including. a compartment for storing said perishables, heat exchange means for extracting heat from a gaseous cooling medium to be passed through said compartment, an exit nozzle in communication with said heat exchange means for receiving the gaseous cooling medium therefrom, said exit nozzle having a discharge end from which the cooling medium exits at a relatively high velocity and low temperature, and a conduit disposed to receive the cooling medium from said exit nozzle and having an exit end portion which communicates With said compartment, characterized in that said conduit has a flared inlet end portion which converges toward and is connected to said exit end portion-, and which flared inlet end portion is aligned with said discharge end of the exit nozzle and so spaced therefrom in. the flow direction of the cooling medium as to form therebetween a gap through which gas of lower velocity and higher temperature is. aspirated from said compartment and into said flared inlet end. portion, there to be mixed with the gaseous cooling medium having the relatively high velocity and low temperature, the size of said gap being such. as to caus e gas from the compartment to be aspirated in an amount sufficient to produce tempering. of the resultant mixture of gaseous cooling medium and aspirated gas.

. The advantages of this arrangement are twofold.

First, the aspiration of gas from the compartment induces gas flow and, thus, enhances gas circulation within the compartment which, of course, is conducive to an even gas distribution and a uniform temperature therein; second, the tempering of the cooling medium about to .be discharged into the compartment minimizes the risk of so-called top freezing of the transported perishables, especially in the regions of gas discharge into. the compartment.

The general concept of mixing two fluids at differr ent temperatures and flow velocities through aspiration ' is not new per se, of course, and. is. shown applied, for instance, in U.S. patent specification No. 1,296,968 according to which, heated or cooled air is mixed with aspirated air from a room prior to being blown into -the room, the purpose of such intermingling of different air streams in this latter disclosure being the protection of people occupying the room from any undue discomfort otherwise experienced if hot or cooled air were blasted into the occupied space-. Yet, while the -above concept was taught, in the last-mentioned specif cation, for use in. offices, hospitals, schools, workshops and similar buildings as early as 1919, nobody apparently has found it obvious to adapt this concept for use in alleviating the problem of top freezing encountered, as set forth above, in the field of transportation refrigeration in which there are still employed such systems as disclosed i the aforesaid U.S.. specification 2,780,923 wherein air chilled in the evaporator unit is simply ducted into a space between the outer container, shell and inner walls thereof provided with openings for directing the chilled air into the cargo space, or as disclosed in the aforesaid U.. S . specification 3,612,093 wherein .gas from within the cargo chamber is sucked into the stream of supplied cooling medium but only for the purpose of supplying the heat necessary to enable evaporation of the liquid cooling medium, e.g. nitrogen, to take place, and wherein outside air is introduced into the cooling medium for no other purpose but to maintain the desired nitrogen-to-air ratio, and is introduced in a proportion insufficient to produce any perceptible tempering of the gas mixture obtained..

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- 43392/2 Figure 1 is a fragmentary side elevation, partly in section, of a transportable refrigeration unit embodying the invention; Figure 2 is an isometric view of the interior or cargo space of the transportable refrigeration unit; Figures 3 and ^ are partially broken-away cross-sectional views of the novel exit nozzle and discharge conduit structure according to the invention; and Figure 5 is a detailed Isometric view of the structure shown in Figs. 3 and k.

Referring to Figures 1 and 2 of the drawings, the invention is shown therein embodied in a refrigeration vehicle 1 intended primarily for use in transporting perishable foodstuffs. The vehicle body consists of an outer J shell having a top wall 2, a bottom wall 4, end walls 6 and 8, and side walls 10 and 12, each wall being provided with an intermediate layer of thermal insulation 10. Within the vehicle 1 there is a cargo chamber 50 wherein the perishables may be stored and preserved. The cargo chamber 50 has a floor rack 13 which is compose^ o a plurality of spaced grate members 14 and raised above the bottom wall 4 so as to form a channel 18 between the floor rack 13 and the bottom wall 4. A partition 16 separates the chamber 50 from the end wall 6, and is suitably spaced therefrom so as to form between the partition and the end wall 6 a compartment or air space 25 which communicates at its lower end with the channel 18 and, as will be described later herein, communicates at its upper end with the cargo chamber 50. Within the compartment 25 there is disposed a refrigerant evaporator or heat exchange unit 30 of a refrigeration system, the remaining components of which have been omitted from the drawings as unnecessary for a clear understanding of the -invention proper.

The heat exchange unit 30, when in operation, causes a gaseous cooling medium, such as chilled air, to flow through the cargo chamber 50 at a relatively high velocity and low temperature. In communication with the discharge aide of the heat exchange unit 30 is a tapering exit nozzle 32 having a truncated base and a discharge end 33.

In accordance with the instant invention, a conduit 34 is disposed within the chamber 50 to receive the cooling medium discharged from the exit nozzle discharge end 33· end portion 36 which communicates with the cargo chamber 50, and a flared inlet end portion 35 which converges with and is connected to the exit end ^portion 36 through an intermediate throat 37 of reduced cross section. The flared inlet end 35 is aligned with the exit nozzle discharge end 33 and is so spaced therefrom in the flow direction of the cooling medium as to form a predetermined, gap 60 between the inlet end 35 of the conduit and the discharge end 33 of the exit nozzle 32, the advantages of which- gap 60 will shortly become apparent.

It is desirable that the flared inlet portion 35 be of a larger cross section than that of the exit nozzle discharge end 33· Thus, the proper dimensioning of the discharge end 33 relative to the inlet portion 35 will cause an aspiration effect within the area of the flared inlet portion, whereby the gaseous cooling medium, having a relatively high velocity and low temperature, and gas of a relatively lower velocity and higher temperature, which is ambient to the cargo chamber atmosphere and to the perishables contained therein, are mixed to form a tempered mixture of gases, which mixture is discharged through the exit end portion 36 of conduit 3** into the cargo chamber 50.

It has been found that with an arrangement as disclosed above, a gaseous cooling medium having a temperature of about 51°P upon discharge from the heat exchange unit 30 can be tempered to obtain both a more moderate cooling medium discharge temperature and a more even distribution of the tempered gas mixture throughout the vehicle mixture has been exhausted from the duct end portion 36 with a resultant temperature of generally between 55°F and 57°F. A further consequence of the aspiration effect is to more evenly distribute the tempered mixture by inducting a path of continuous circulation throughout the cargo chamber 50 and down through the floor rack 13 (shown by Pig. 1) to the forward end of the chamber by way of channel 18 where the major portion of the air will flow upward through the compartment 25 and into the heat exchange unit 30 for recirculation.

By maintaining a predetermined gap 60 between the axially aligned flared inlet end 35 and exit nozzle discharge end 33» the temperature and volume of the gases entering the inlet end 35 can be regulated, depending upon the chosen size of the gap, and accordingly, the temperature of the mixture being exhausted from conduit exit end 3 can be controlled, as desired, without the need of complex regulating equipment.

The tempered mixture of gases may be exhausted through the conduit 3* directly into the cargo chamber, as illustrated in Figures' 3 to 5» or the exit end portion 3 may be suitably modified as part of the conduit assembly.

It is also within the scope of this invention to extend the conduit exit end 36 longitudinally across a major portion of the chamber 50 such that the tempered mixture may be exhausted at a point near the vehicle end wall 8. Or, still another arrangement, as shown in Figs. 1 and 2, would be to affix to exit end 36 a separate, elongated, 40 and the vehicle top wall 2 , thereby providing a wider distribution of the mixture throughout the cargo air space.

As an alternative embodiment of the invention, the. flared inlet end portion 35 of conduit 3 and the discharge end 33 of the heat exchanger exit nozzle 32 may be enclosed by a hollow duct 38 having both its front and rear ends 2 and 44 open and exposed to the cargo space which is ambient to the perishables. With the addition of a duct such as duct 38 , it has been found that an aspiration effect may occur, not only in the area of the conduit inlet end portion 35» as described hereinbefore, but also at the front and rear ends 42 and 44 of the duct 38. Thus, air ambient to the cargo space is supplied to the conduit inlet end 35 for mixing with the chilled cooling medium therein from different regions of the cargo space so that a better circulation of the tempered mixture is induced throughout the cargo space. The positioning of duct 38 relative to the gap 60 can also provide further means for regulating the temperature of the tempered gas mixture exhausted from the conduit exit end 36 , without the need of complex control equipment. Thus, the invention provides relatively simple and inexpensive means for regulating the cooling of a transportable refrigeration cargo chamber to preserve perishables which will also help to reduce the cost of the perishables to the ultimate user.

Claims

WHAT WE CLAIM IS:-

1. A transportable refrigeration unit for preserving perishables, including a compartment for storing said perishables, heat exchange means for extracting heat from a gaseous cooling medium to be passed through said compartment, an exit nozzle in communication with said heat exchange means for receiving the gaseous cooling medium therefrom, said exit nozzle having a discharge end from which the cooling medium exits at a - relatively high velocity and lo temperature, and a conduit disposed to receive the cooling medium from said exit nozzle and having, an exit end portion which communicates with said compartment, characterized in that said conduit has a flared inlet end portion which converges toward and is connected to said exit end portion, and which flared inlet end portion is aligned with said discharge end of the exit nozzle and so spaced therefrom in the flow direction of the cooling medium as to form therebe^ tween a gap through which gas of lower velocity and higher temperature is aspirated from said compartment and into said flared inlet end portion, therein to be mixed with the gaseous cooling medium having the relatively high velocity and low temperature, the size of said gap being such as to cause gas from the compartment to be aspirated in an amount sufficient to produce tempering of the resultant mixture of gaseous cooling medium and aspirated gas.

2. A transportable refrigeration unit according to claim 1, characterized by a hollow duct enclosing said flared inlet end portion, the discharge end of said exit nozzle, and said gap in spaced relationship with respect thereto, said duct

3. A transportable refrigeration unit for preserving perishables according to claim 1 or 2, characterized by an elongated gas distributing means connected to the exit end portion of said conduit and having a plurality of gas distributing openings formed therein.

4. A transportable' refrigeration unit for preserving perishables apcc?r,ding to claim 1, 2 or 3 characterized in that said exit nozzle tapers towards the discharge end thereof.

5. A transportable refrigeration unit for preserving perishables, substantially as hereinbefore described ith reference to, and as illustrated in, the accompanying drawings.