Refrigeration beam with a compressible member and refrigeration apparatus incorporating the same

DESCRIPTION

Technical Field

The present invention relates to an improved refrigeration beam that can be used as part of a refrigeration apparatus to cool a space.

Background Art

In a known refrigeration apparatus, an elongate refrigeration beam is located in a space to be cooled. The refrigeration beam typically has a hollow metal or plastic outer casing of rectangular cross-section with metal pipes for carrying a refrigerant gas (such as an HFC or a CFC/HCFC gas) running longitudinally through the interior. The space between the outer surface of the pipes and the inner surface of the outer casing is filled with a phase change material. The phase change material is a freezing mixture that can be formed from a combination of non-toxic salts and organic compounds in an aqueous solution. It can be presented either as a liquid or converted to a gel by using one of a number of different proprietary gelling agents.

An electrically powered condensing unit is used to compress the refrigerant gas which is then passed through the pipes to lower the temperature of the phase change material. Once the temperature of the phase change material has been reduced to below its freezing point the liquid or gel is converted into a solid. Once the flow of refrigerant gas is stopped, the phase change material will eventually start to thaw and return back to a liquid or gel. The temperature of the phase change material will not alter during the change of state (due to the well known principle of latent heat) and the refrigeration beam will therefore remain at a low temperature for a certain period of time during which it will cool the space.

If the refrigeration beam is mounted in the loading space of a transport vehicle, for example, then it is usual for the condensing unit to be operated during the night to reduce the temperature of the phase change material to below its freezing point. The refrigeration beam is then able to cool the loading space when the transport vehicle is used during the daytime. In a typical refrigeration apparatus, a spaced array of refrigeration beams are mounted in the loading space and the metal pipes running longitudinally through the interior of each beam are connected together to form a closed piping network that is connected to the inlet and outlet of the condensing unit.

Summary of the Invention

The present invention provides a refrigeration beam for use with a refrigeration apparatus, the refrigeration beam having an outer casing, a first pipe for carrying cooling fluid, a second pipe for carrying cooling fluid, and wherein the space between the outer surfaces of the first and second pipes and the inner surface of the outer casing contains a phase change material, wherein the outer casing includes a first arcuate section that is shaped to partly enclose a first substantially cylindrical volume and a second arcuate section that is shaped to partly enclose a second substantially cylindrical volume, wherein the first and second sections of the outer casing are joined together by arcuate intermediate sections that extend inwards to reduce the amount of space therebetween (and most preferably to minimise, as far as possible, the amount of space between the outer surfaces of the first and second pipes and the inner surface of the outer casing that lies outside the first and second substantially cylindrical volumes), wherein the first and second substantially cylindrical volumes are substantially tangent, wherein the first and second pipes are located substantially at a centre of the first and second substantially cylindrical volumes, respectively, and wherein the refrigeration beam further comprises a compressible member in the form of a strip of compressible material extending along a longitudinal axis of the refrigeration beam and being located within the space substantially at a centre of the refrigeration beam to accommodate any expansion of the phase change material.

The phase change material will typically expand as it freezes. The incorporation of a compressible strip within the space can therefore help to eliminate the risk of the refrigeration beam being damaged or fractured by the expansion as described further below. The compressible strip can have any convenient size and shape and will typically be large enough to accommodate or absorb most, if not all, of the phase change material expansion. The compressible strip is preferably supported at or near the centre of the refrigeration beam and typically extends along substantially the entire axial length of the refrigeration beam.

The compressible strip may be made of any suitable compressible, resilient material such as rubber, synthetic rubber or the like. The compressible material must be chemically compatible with the phase change material in which it is immersed.

The present invention further provides a refrigeration apparatus comprising at least one refrigeration beam as described above, and a source of cooling fluid (optionally a refrigeration gas) connected to the first and second pipes. The source of cooling fluid can be a condensing unit, for example. In use the refrigeration beam will be located in a space to be cooled.

During operation, cooling fluid is passed through the first and second pipes to lower the temperature of the surrounding phase change material below its freezing point, including any margin for super-freezing. Any expansion of the phase change material is absorbed by the compressible strip to avoid any undue stresses being placed on the outer casing, for example. Once all of the phase change material inside the outer casing is frozen solid, the flow of cooling fluid can be stopped.

The intermediate sections of the outer casing are considered to be important to the operation of the refrigeration beam. As the cooling fluid is passed through the first and second pipes radial cooling occurs working outwardly from the outer surface of the pipes. After a finite amount of time has passed it can be assumed that the radial cooling has frozen solid the phase change material within the first and second substantially cylindrical volumes and only the phase change material that lies in the space outside the first and second substantially cylindrical volumes remains in the liquid or gel state. The refrigeration beam will only operate correctly if all of the phase change material is frozen solid. The susceptibility of the refrigeration beam to complete freezing is therefore improved by minimising the space that lies outside the first and second substantially cylindrical volumes and this is achieved by the configuration of the intermediate sections of the outer casing which extend inwardly to reduce the space therebetween. The configuration of the intermediate sections or the 'waisting' of the outer casing must not compromise the strength or rigidity of the refrigeration beam. Positioning the strip of compressible material at or near to the centre of the refrigeration beam means that it undergoes compression at the critical time when substantially all of the phase change material in the first and second substantially cylindrical volumes is frozen solid and when only the phase change material in the space between the intermediate sections of the outer casing remains in the liquid or gel state. The 'waisting' of the outer casing that is provided by the intermediate sections means that the refrigeration beam is at its narrowest at the point where the compressible strip is located and where it would otherwise suffer significant stresses as the final part of the phase change material expands as it freezes solid. The addition of the compressible strip therefore allows the refrigeration beam to maximise the technical benefit that comes from minimising the amount of space that lies outside the first and second substantially cylindrical volumes and results in a refrigeration beam that provides significantly better cooling performance while maintaining its strength and rigidity.

The phase change material is a freezing mixture that can be formed from a combination of non-toxic salts and organic compounds in an aqueous solution. Before being cooled to below its freezing point, the phase change material can be a liquid but in some cases improved results have been obtained using a gel.

Although the first and second volumes are most preferably perfectly cylindrical such that they receive uniform radial cooling from cooling fluid passing through the first and second pipes, which are centrally located within the first and second volumes, respectively, it will be readily appreciated that the benefits of the present invention can still be realised if the first and second volumes are a reasonable deviation from perfectly cylindrical, or if the first and second pipes are not perfectly located at the centre of the first and second volumes. The cross-section of the first arcuate section preferably defines the arc of a first circle having a centre and a first radius and more uniform freezing of the phase change material in the first volume can be obtained if the first pipe is located substantially at the centre of the first circle. Similarly, the cross-section of the second arcuate section preferably defines the arc of a second circle having a centre and a first radius and more uniform freezing of the phase change material in the second volume can be obtained if the second pipe is located substantially at the centre of the second circle.

The first and second pipes are preferably substantially parallel to each other and to a longitudinal axis of the outer casing along at least a significant proportion of the total length of the refrigeration beam. It will be readily appreciated that the first and second pipes may be two separate pipes connected independently to a source of cooling fluid. However, it is generally preferred that the so-called first and second pipes are in fact extensions of a single pipe that passes through the one of the volumes of the outer casing before being reversed so that it passes through the other one of the volumes of the outer casing.

Drawings

Figure 1 is a cross-section through a refrigeration beam according to the present invention.

A refrigeration beam includes a metal or plastics outer casing 2 having two distinct rounded sections or 'lobes' 2a and 2b that are joined together by rounded intermediate sections 2c. When considered along the length of the refrigeration beam, each of the sections 2a and 2b partly encloses and defines a substantially cylindrical volume 4a and 4b.

When considered in cross-section, it can be seen that the section 2a is formed to follow an arc of a first circle and the section 2b is formed to follow an arc of a second circle. The first and second circles are tangent to each other so that the distance between their centres is equal to the sum of the radius Ri of the first circle and the radius R ₂ of the second circle. A first pipe 6 for carrying refrigerant gas supplied by a condensing unit (not shown) is located in the cylindrical volume 4a at the centre of the first circle. Similarly, a second pipe 8 for carrying refrigerant gas supplied by the same or a different condensing unit (not shown) is located in the cylindrical volume 4b at the centre of the second circle. The first and second pipes 6, 8 are therefore positioned parallel to each other and to a longitudinal axis of the outer casing 2 along the length of the refrigeration beam.

The volume between the outer surfaces of the first and second pipes 6, 8 and the inner surface of the outer casing 2 is filled with a phase change material such as a combination of non-toxic salts and organic compounds in an aqueous solution.

Compressed refrigerant gas is passed through the first and second pipes 6, 8 from the condensing unit (not shown). The first and second pipes 6, 8 have good thermal conductivity and by a process of conduction they lower the temperature of the phase change material working radially outwards from the outer surfaces of the pipes.

The refrigeration beam of the present invention provides a much more uniform freezing of the phase change material as compared to a conventional refrigeration beam.

Forming the outer casing 2 with two distinct rounded sections 2a and 2b and a 'waisted' part defined by the intermediate sections 2c has the additional beneficial effect of increasing the surface area of the refrigeration beam that is available for cooling as well as minimising the space that lies outside the first and second cylindrical volumes 4a and 4b.

A strip 10 of compressible, resilient material such as rubber is supported at the centre of the refrigeration beam. The strip 10 extends along substantially the entire axial length of the refrigeration beam. Positioning the strip 10 at the centre of the refrigeration beam means that it is at the meeting point of the two cooling zones which originate at the first and second pipes 6, 8 and can undergo compression at the critical time when substantially all of the phase change material in the cylindrical volumes 4a and 4b is frozen and only the phase change material in the intervening regions adjacent the strip 10 remains in the liquid or gel state. The refrigeration beam is also at its narrowest at this point and may suffer significant stresses as the phase change material expands. These stresses are substantially eliminated by the addition of the strip 10 which is compressed as the surrounding phase change material expands as it freezes.