WO2005077713A1

WO2005077713A1 - A reefer with integrated evaporator

Info

Publication number: WO2005077713A1
Application number: PCT/DK2005/000095
Authority: WO
Inventors: Erik Grøndal BECK
Original assignee: Mærsk Container Industri As
Priority date: 2004-02-12
Filing date: 2005-02-11
Publication date: 2005-08-25

Abstract

A cooling system for a freight reefer (1) comprising lateral walls, end walls, a bottom, and a ceiling, said bottom, ceiling and walls defining an interior space and comprising an outer cladding (101), an inner cladding (100) and an insulating layer (102) sandwiched there between, said cooling system comprising a cooling unit (20) having a condensator face and a compressor formed outside said interior space, the cooling system further comprising at least one evaporator face (30) integrated in said inner cladding (100).

Description

A reefer with integrated evaporator

The invention comprises a cooling system for a freight reefer comprising lateral walls, end walls, a bottom and a ceiling, said bottom, ceiling and walls comprising an outer cladding, an inner cladding and an insulating layer sandwiched there between, said cooling system comprising a cooling unit comprising a condensator face and a compressor.

To cool the interior of a freight reefer to enable transport of frozen perishables, eg frozen foodstuffs, such reefers are provided with a cooling/freezer system. Typically such cooling systems are structured as a so-called "forced air cooling" system, comprising a cooling unit arranged within the reefer, typically on the one end wall. The cooling unit of such a system comprises on the inside an evaporator for cooling passing air and a blower/ventilator/fan, and on the outside a condensator, and a compressor . Thus, the cooling system operates in that the ventilator of the cooling unit draws in the heated reefer air at the top, following which the hot air is cooled down by passage of the evaporator, and is blown out at the bottom, typically underneath a floor of T-beams.

This type of cooling system is associated with a number of drawbacks. The ventilator circulating the air within the reefer deposits energy in the form of heat within the reefer. This heat is subsequently to be removed by the cooling arrangement, which reduces the energy efficiency of the cooling system.

Moreover, the distribution of air is not even throughout the reefer length. In the end most proximate to the cooling arrangement, the conditions are more or less like a storm, whereas, at the end most proximate the doors, a faint breeze is an adequate description; this means that to ensure that a sufficient amount of cooling air is admitted to the door end of the reefer, a powerful wind is created in that end where the cooling unit is located. This contributes to the creation of an uneven temperature in the reefer, and therefore the reefer must be loaded to take into account which goods are able to tolerate which temperatures, with ensuing increased costs.

It is a further problem of the prior art cooling systems that they presuppose that the reefer is charged such that free passage of air around the cargo is ensured at all times. Consequently the efficient cargo carrying capacity of the reefer is reduced.

Moreover, the prior art cooling units take up quite a lot of space that could otherwise be used for payload.

A variant of the above mentioned system is known from GB 1 049 945 in which a cooled gas is forced by a fan, a jet or a turbine in the cooling unit through gas channels formed in the insulation material of the walls of a small scale cold store. The cooling unit with the fan for forcing the air through the channels is arranged inside the cooling unit inside the cold store. The cooling effect is delivered from a tank containing carbon dioxide or nitrogen. The gas is passed through the gas channels and allowed to dissipate from the system. The system further comprises an evaporator placed inside the cold store to cool the air inside the cold store. The inner cladding of the cold store is formed in a cement plaster.

This system has the disadvantage that a considerable amount of gas need to be passed through the air channels in order to cool the inside of the cold store. Therefore, the air channels has to take up a good deal of space inside the isolation, and consequently, the isolation thickness must be reduced at least in the area where the channels are formed leading to reduced heat insulation properties, or the wall thickness must be increased thus influencing the effective space for holding the frozen perishables. Further the evaporator formed within the cold store stakes up room that could otherwise be applied for holding frozen perishables. It is highly undesirable that the coolant inside the evaporator escapes to the cold store. Therefore, when packing the cold store a considerable distance must be kept between the evaporator and the payload, thus further decreasing the effective space of the cold store, and further leaving the cooling system rather fragile. Another disadvantage of this system is that heat emitting apparatus in the form of the fan, turbine, or jet needs to be placed inside the cold store, thus decreasing the efficiency of the cooling system. Moreover, this prior art cooling units itself take up quite a lot of space that could otherwise be used for payload. Further, the gas tank will eventually run dry, because the cooling gasses are allowed to escape to the outside of the cold storage. The use of cement plaster as inner cladding is disadvantageous since this does not have good heat conducting properties, and it is not very resistant to impacts.

It is an object of the invention to provide a cooling system for a freight reefer that overcomes the disadvantages of the prior art, and which is more efficient from an energy point of view. It is also an object of the invention to provide a cooling system which yields a more even distribution of air and in particular distribution of temperature in the freight reefer. It is a further object of the invention to provide a cooling system that enables improved utilisation of the cargo space of the freight reefer. It is a further object of the invention to provide a cooling system in which the cooling unit can be considerably decreased in size. It is a further object to provide a cooling system that is durable and resistant to the impacts that inevitably occurs during loading and unloading of the reefer container. It is a further object of the invention to provide a cooling system that provides an effective cold shield for preventing heat from the outside to enter the reefer through the walls. It is a further object to provide an alternative cooling system and an alternative reefer. The object of the invention is accomplished by a cooling system as featured in the preamble to claim 1, which cooling system comprises at least one evaporator face integrated in said inner cladding.

The cooling system preferably comprises liquid coolant-conveying passages in close connection with at least portions of said inner cladding, said inner cladding being configured from a heat-conducting material, and said passages being connected to said cooling unit.

Hereby it is accomplished that the heat-emitting parts of the cooling unit can be omitted and that the inner cladding of the reefer is caused to serve as an efficient cold shield against the heat coming from the outside, whereby a more energy-efficient cooling system is accomplished. By avoiding forced circulation of the air contained in the freight reefer, a considerably more even temperature distribution is accomplished throughout the length of the reefer. Consequently it is no longer necessary to load the cargo such that air passages are formed between the cargo and the inner cladding. Hereby more efficient packing of the load is accomplished. Moreover, the cooling system according to the invention takes up less space, which also increases the cargo-carrying capacity, and has considerably resistance to unintended impacts.

It has moreover been found that it is considerably easier to control the temperature in a reefer with a cooling system according to the invention, and therefore it is accomplished that simpler and more cost-effective parts can be used in the temperature control arrangement.

The inner cladding of the cooling system is preferably made of aluminium.

Aluminium is a good heat conductor that allows the area around the passages to serve as evaporator faces, whereby the above-mentioned cold shield can be formed. Moreover, aluminium is a light and strong material which means that good strength can be accomplished against impacts and the like during the loading of goods to the freight reefer without simultaneously increasing the weight of the reefer.

The cooling system may have one or more evaporator faces formed in the ceiling or in one or more lateral walls, preferably in the upper half of the lateral wall. By arranging the evaporator faces high up the most efficient cooling of the reefer is accomplished. Moreover the high position means that the channels are not damaged since experience has shown that most of the damage in connection with the loading or unloading of the reefer occurs at the bottom of the inner cladding.

According to a particularly preferred embodiment of the invention, the passages of the cooling system are integrated in at least portions of the inner cladding. Hereby the closest possible contact between the liquid coolant and the inner cladding is accomplished. Moreover, a robust cooling system which is easy to maintain is accomplished. The passages being formed in an extruded aluminium plate that partakes in the inner cladding, the invention is configured in a particularly convenient way, since portions of the inner cladding of reefers according to the prior art already comprise extruded profiles/plate elements. Thus there will not be any particular technical difficulties or costs associated with the production or mounting of profiles of inner claddings with integrated passages. From an overall point of view it becomes both simpler and more cost-effective to manufacture and maintain a cooling reefer with the cooling system according to the invention.

The invention will be described more detailed in the following with reference to the figures, wherein:

Fig. 1A is an explanatory sketch of the cooling system in a freight reefer according to the prior art; - Fig. 1B is an explanatory sketch of a section B of a cooling unit for a cooling system as shown in Figure 1A; - Fig. 2A shows an explanatory sketch of a cooling system for a freight reefer according to the invention;

- Fig. 2B is a sectional view through the outer and inner cladding of a freight reefer along section B-B of Figure 2A, showing an embodiment of the tubing of the cooling system;

- Fig. 2C is a sectional view through the outer and inner cladding of a freight reefer along section B-B of Figure 2A, showing another embodiment of the tubing of the cooling system; and

- Fig. 3 shows the arrangement of the passages in another embodiment of the invention.

In a cooled freight reefer 1 according to the prior art and as illustrated in Figure 1 A, a principle of forced circulation is used for the cooling system-

The freight reefer 1 typically comprises a frame, between which side and lateral walls, a bottom and a ceiling are arranged. The frame consists of upper and lower longerons at each side; upper and lower transverse girders at each end, and vertically arranged corner posts. To that frame the lateral walls, ceiling and bottom of the reefer are arranged. In particular in connection with cooling reefers, the walls, the bottom and ceiling are configured as double walls, ie as a sandwich structure of two metal plates, ie an inner cladding and an outer cladding; and an interposed insulating layer. Moreover, the bottom is most often provided internally with a floor of T- beams. Those T-beams are connected to the inner cladding of the bottom and form longitudinally extending passages. Between the T-beams there is a small space that allows the pair to pass upwards and into the reefer space as such. The one end wall of such reefer is typically provided with doors (not shown) that allow access to the reefer.

Internally in the freight reefer 1 and typically at the opposite end of said doors, a cooling unit 2 is arranged. A section A of the cooling unit 2 is shown in Figure 1B. The cooling unit 2 comprises an evaporator 3 typically consisting of a coolant-conveying system of winding tubes for forming an evaporator face, and a fan 4. The evaporator 3 is in conventional manner connected with a compressor/pump (not shown) and a condenser/cooler (not shown) on the outside of the freight reefer 1. The fan 4 is intended for circulating the air internally in the freight reefer 1. That circulation is indicated by the arrows in Figures 1A and 1 B. In Figure 1A, the arrows show that hot air is drawn into the cooling unit 2 at the top and cold air is blown out at the bottom of the freight reefer 1. In Figure 1 B the arrows show how the hot air is drawn in at the ceiling of the cooling unit 2 by the fan 4 and forced past the evaporator 3, whereby the air is cooled prior to being blown back in at the bottom of the reefer.

In Figure 2A a freight reefer 1 is shown that has a cooling system according to the invention. The freight reefer 1 comprises an inner cladding 100, an outer cladding 101 , and an insulating material 102 there between. The walls, bottom and ceiling defines an interior space, suitable for holding a payload. The cooling system of the freight reefer 1 also comprises a cooling unit 20. In a usual manner, the cooling unit 20 comprises a compressor (not shown) and a condenser/cooler (not shown) on the outside of the freight reefer 1.

The cooling unit 10 is in fluid connection with a system of passages 31 connected to at least portions of the plating partaking in the inner cladding

100 of the walls, ceiling or bottom of the freight reefer 1. The passages 31 are configured for conveying a liquid coolant. The liquid coolant is conveyed around the passages 31 by the compressor/pump configured in the cooling unit 20. The inner cladding 100 is configured from a heat-conducting material, preferably aluminium. Thereby the passages 31 and inner cladding 100 constitute evaporator faces 30 thus being integrated in the inner cladding 100. Thereby an efficient cold shield is formed in the walls that will minimize the heat passage through the surfaces defining the reefer container.

In Fig. 2A the passages 31 are only schematically outlined. The passages 31 of course forms looped passageways such that the coolant is recycled through the cooling unit 20.

The passages 31 are formed in close contact with the inner cladding 100 to achieve the best possible heat conduction between inner cladding 100 and the coolant in the passages 31. For instance, the passages can be formed in a tubular system connected in close contact with the inner cladding, eg secured by clips or soldered thereto. Thereby the inner cladding 100 provides support for the tubing, making it more resistant to the incidental, but unavoidable impacts from cargo being loading or unloaded. Preferably, such tubing is disposed in grooves formed in the plating, partaking in the inner cladding 100 on the side of the cladding facing the interior space of the reefer container, as shown in Fig. 2C. Thereby the tubing is further protected from the incidental but unavoidable impacts from cargo being loading or unloaded.

According to a another embodiment the passages 31 are integrated in plating partaking in the inner cladding 100. Such inner cladding 100 can be constituted of an extruded aluminium plate, which is illustrated in Figure 2B.

Passages 31 extend essentially throughout the entire length of the freight reefer 1 and are preferably formed from predominantly straight elements in order to reduce the friction between the inner wall of the passages 31 and the liquid coolant.

As shown in figures 2A the evaporator faces 30 consisting of passages 31 and inner cladding 100 can be arranged in the uppermost corners of the freight reefer 1. However such evaporator faces 30 can be arranged anywhere in the inner cladding 100 of the freight reefer, in lateral or end walls, in the ceiling or in the floor.

However, in a preferred embodiment passages 31 are formed over the entire surface of the lateral walls, such that the evaporator faces 30 constitute essentially the entire inner cladding 100 of the lateral walls, as shown in Fig. 3.

As will appear the operation of the cooling system according to the invention is based on natural circulation of air inside the interior space. There is no forced circulation of air, and therefore a more uniform distribution of temperature is accomplished. Moreover, the drying effect is avoided which may in some cases occur where circulating air is concerned.

A cooling system for a freight reefer 1 configured as taught above is particularly advantageous in connection with freight reefers that are intended in particular for the transport of frozen goods. When the cargo contained in the freight reefer 1 is frozen, the only heat to be disposed of is the incident heat entering through the reefer walls, bottom and ceiling. By configuration of the inner cladding 100 of the reefer from a highly heat conveying material and integration of the evaporator face 30 in the inner cladding 100, the inner cladding 100 of the reefer is caused to serve as a cold shield against the heat coming from the outside. By configuration of the evaporator faces 30 in close connection with or integrated in the plating of the inner cladding 100, space is saved relative to the systems that use "forced air cooling", since it is not necessary to allocate space within the cooling unit 20 for fan 4 or evaporator 3.

Herein the invention is aimed at freight reefers intended for freight of goods by ship. However, the cooling system is equally applicable for use in connection with trailers for trucks or the like or trucks or the like with permanent refrigerated storages.

Claims

C l a i m s

1. A cooling system for a freight reefer (1) comprising lateral walls, end walls, a bottom, and a ceiling, said bottom, ceiling and walls defining an interior space and comprising an outer cladding (101 ), an inner cladding (100) and an insulating layer (102) sandwiched there between, said cooling system comprising a cooling unit (20) having a condensator face and a compressor formed outside said interior space, characterised in that the cooling system further comprises at least one evaporator face (30) integrated in said inner cladding (100).

2. A cooling system according to claim 1 , characterised in that said evaporator face (30) comprises liquid coolant-conveying passages (31 ) formed in close connection with at least portions of said inner cladding (100), said inner cladding (100) being configured from a heat-conducting material, and said passages (31) being connected to said cooling unit 20.

3. A cooling system according to claim 1 or 2, characterised in that said inner cladding (100) is configured from aluminium.

4. A cooling system according to any one of claims 1-3, characterised in that one or more evaporator faces (30) is/are formed in the ceiling.

5. A cooling system according to any one of claims 1-4, characterised in that one or more evaporator face (30) is/are formed in a lateral wall.

6. A cooling system according to claim 5, characterised in that one or more evaporator faces (30) is/are configured in the top half of the lateral wall.

7. A cooling system according to any one of the preceding claims, characterised in that the passages (31 ) formed integrally with the plating that partakes in the inner cladding (100).

8. A cooling system according to claim 7, characterised in that the passages (31 ) are configured in an extruded aluminium plate.

9. A cooling system according to any one of claims 1-6, characterised in that the passages (31) are formed by a tubing disposed in close contact with the inner cladding (100).

10. A cooling system according to claim 7, characterised in that the tubing is disposed in grooves formed in the plating, that partakes in the inner cladding (100).