GB2432411A

GB2432411A - Refrigeration beam

Info

Publication number: GB2432411A
Application number: GB0523405A
Authority: GB
Inventors: Peter Maitland Jackson
Original assignee: L E JACKSON
Current assignee: L E JACKSON
Priority date: 2005-11-16
Filing date: 2005-11-16
Publication date: 2007-05-23
Anticipated expiration: 2025-11-16
Also published as: GB0523405D0; GB2432411B; WO2007057642A1

Abstract

The present invention provides a refrigeration beam for use with a refrigeration apparatus. The refrigeration beam includes an outer casing 2 and a pair of pipes 8 and 10 for carrying cooling fluid. The space between the outer surfaces of the pipes 8 and 10 and the inner surface of the outer casing 2 contains a phase change material in the form of a freezing material. The invention is characterised in that the outer casing 2 is shaped to enclose a first substantially cylindrical volume and a second substantially cylindrical volume and where the first and second cylindrical volumes are adjacent, tangent or overlapping. The source of cooling fluid may be a condensing unit, and the phase change material may be a combination of non-toxic salts and organic compounds in an aqueous solution.

Description

TITLE

Refrigeration beam 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 horn 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 (including any margin for super-freezing) 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.

Unless the entire volume of the phase change material is converted into a solid then its capability to act as a refrigerant is vastly reduced, almost to the point of being destroyed completely. This is clearly illustrated in Figure 1, which is graph of temperature versus time. It shows how the temperature of the refrigeration beam can rise relatively quickly if only 90% of the phase change material is frozen solid when the condensing unit is turned off. The period of time (marked "A") when the temperature of the refrigeration beam remains substantially constant as the phase change material thaws is shorter than would be the case if all of the phase change material were frozen solid. This equates to a significant reduction in the effective refrigeration power of the refrigeration beam. If 100% of the phase change material is frozen solid when the condensing unit is turned off then the temperature of the refrigeration beam will remain substantially constant for a long period of time (marked "B") while the phase change material returns back to a liquid or gel. It is therefore important to make sure that the refrigeration beam is cooled for a sufficiently long period of time so that none of the phase change material remains in the liquid or gel state.

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.

In a commercial situation, there is clearly a finite amount of time that can be allowed for converting the phase change material to a solid but if this is not sufficient then the temperature of the refrigeration beam will rise too quickly to provide useful cooling.

Accordingly, there is a need for a refrigeration beam that gives improved confidence that all of the phase change material has been frozen solid in the time available.

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, characterised in that the outer casing is shaped to enclose a first substantially cylindrical volume and a second substantially cylindrical volume and wherein the first and second substantially cylindrical volumes are adjacent, tangent or overlapping.

The cooling fluid is preferably a refrigerant gas such as an HFC or a CFC/I-ICFC gas.

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.

Specific examples would include sodium chloride (NaCl) or potassium bromide (KBr) in water. 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 most preferably 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 outer casing preferably includes a first arcuate section that defines the first volume and a second arcuate section that defines the second volume. The first pipe is preferably located in the first volume such that the passage of cooling fluid through the first pipe will lower the temperature of the phase change material in the first volume and the second pipe is preferably located in the second volume such that the passage of cooling fluid through the second pipe will lower the temperature of the phase change material in the second volume.

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.

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 cross-section of the outer casing as a whole therefore takes the form of two conjoined circles.

The distance between the centre of the first circle and the centre of the second circle can be (i) more than the sum of the first radius and the second radius such that the first volume and the second volume are adjacent, (ii) the same as the sum of the first radius and the second radius such that the first volume and the second volume are tangent, or (iii) less than the sum of the first radius and the second radius such that the first volume and the second volume are overlapping.

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. The refrigeration apparatus can include two or more of such refrigeration beams, optionally with their first and second pipes connected together to form a closed piping network. 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 phase change material in the surrounding first and second volumes and in any additional volume(s) enclosed within the outer casing (i.e. any volumes adjacent the region where the first and second arcuate sections are joined together) below its freezing point (including any margin for super-freezing). Once all of the phase change material inside the outer casing is frozen solid, the flow of cooling fluid can be stopped. The shape of the outer casing of the refrigeration beam means that the time taken for all of the phase change material inside the outer casing to be frozen solid is less than would normally be the case for a conventional refrigeration beam with a substantially rectangular cross-section (assuming a constant volume of phase change material). This is because the shape of the outer casing is a better match to the pattern of radial cooling that is provided by the cooling fluid passing through the first and second pipes.

Drawings Figure 1 is a graph of temperature versus time comparing the situation where only 90% of the phase change material is frozen solid with the situation where 100% of the phase change material is frozen solid; Figure 2 is a cross-section through a first refrigeration beam according to the present invention; and Figure 3 is a cross-section view through a second refrigeration beam according to the present invention.

With reference to Figure 2, a first refrigeration beam includes a metal or plastic outer casing 2 having two distinct rounded lobes or sections 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 defines a substantially cylindrical volume 4a and 4b the respective outer surfaces of which are represented by the relevant parts of the outer casing 2 and the dashed lines 6a and 6b.

When considered in cross-section, it can be seen that the section 2a is formed to follow an arc of a first circle (represented by the relevant part of the outer casing 2 and the dashed line 6a) and the section 2b is formed to follow an arc of a second circle (represented by the relevant part of the outer casing and the dashed line 6b). 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 R1 of the first circle and the radius R2 of the second circle. However, as mentioned in more detail below, it will be readily appreciated that the first and second circles do not have to be tangent to each other and the distance between their centres can be more or less than the sum of the radius R1 of the first circle and the radius R2 of the second circle.

A first pipe 8 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 10 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 8 and 10 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 8 and 10 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 8 and 10 from the condensing unit (not shown). The first and second pipes 8 and 10 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.

A conventional refrigeration beam with a rectangular cross-section is represented in Figure 2 by the dashed line 12. After a finite amount of time has passed, it can be assumed that the radial cooling has reached the limits represented by the dashed lines 6a and 6b. At this point, all of the phase change material in the substantially cylindrical volumes 4a and 4b should be in the solid state with only the phase change material in the volumes l4a and 14b remaining in the liquid or gel state. A further finite amount of time would obviously be needed to lower the temperature of the phase change material in the volumes 14a and 14b to below its freezing point (including any margin for super-freezing) such that all of the liquid or gel inside the outer casing 2 is converted into a solid. However, it is clear that this further finite amount of time is considerably less than the time that would be needed to convert the phase change material in the volumes I 6a to 1 6f of the conventional refrigeration beam 12. One of the reasons for this is that unlike the outlying volumes l6a to 16f which must be individually cooled, the phase change material in the volumes 1 4a and 14b is effectively cooled from both sides as the radial cooling provided by the first pipe 8 overlaps with the radial cooling provided by the second pipe 10.

The refrigeration beam of the present invention provides a much more uniform freezing of the phase change material as compared to the conventional refrigeration beam 12 and as a result of this: (i) either the time taken to freeze the same volume of phase change material is 25% less than would normally be the case; or (ii) the volume of the phase change material can be increased by 57% and frozen solid in the same time.

If this is looked at in purely commercial terms then it can seen that if a transport vehicle having an array of twenty conventional refrigeration beams mounted in a loading space arrives back at a depot at 6.00 pm and it takes twelve hours to freeze solid all of the phase change material then the vehicle is not available for use until at least 6.00 am. However, if the conventional refrigeration beams are replaced by those manufactured in accordance with the present invention then the time taken to freeze solid the same volume of phase change material will be reduced by 25% and the vehicle will be available for use from 3.00 am. This is obviously quite a significant improvement and allows for much greater flexibility if a vehicle is late arriving back at the depot, for example.

If the time needed to freeze all of the phase change material can remain the same then the volume of phase change material in each of the refrigeration beams can be increased by up to 57%. This can result in a reduction in the total number of refrigeration beams that are required to achieve the same amount of cooling, leading to substantial savings in the cost of installing and maintaining the refrigeration apparatus.

Forming the outer casing 2 with two distinct rounded sections 2a and 2b has the additional beneficial effect of increasing the surface area of the refrigeration beam that is available for cooling.

Figure 3 shows a second refrigeration beam that is generally similar the refrigeration beam of Figure 2 and like parts have been given the same reference numerals. The only difference is that the first and second circles are not tangent to each other but are overlapping, in other words the distance between their centres is less than the sum of the radius R1 of the first circle and the radius R2 of the second circle. Although Figure 3 shows the distinct rounded sections 2a and 2b coming together along a sharp join line without the need for the rounded intermediate sections 2c, it will be readily appreciated that in practice the join can still have a slight radius. Overlapping the first and second circles in this way eliminates the volumes 14a and 14b and has the effect of reducing the time taken for all of the phase change material to change from the liquid or gel state to the solid state. however, it also reduces the surface area of the outer casing 2 that is available for cooling.

Although not shown, it will be readily appreciated that making the distance between the centres of the first and second circles more than the sum of the radius R1 of the first circle and the radius R2 of the second circle has the opposite effect of increasing the time taken for all of the phase change material to change from the liquid or gel state to the solid state (because of an increase in the volumes l4a and 14h) but it also increases the surface area of the outer casing 2 that is available for cooling. As long as the intermediate sections 2c joining the sections 2a and 2b are indented relative to the dashed line 12 of Figure 2, the refrigeration beam of the present invention will always demonstrate a technical advantage over the conventional refrigeration beam having a rectangular cross-section.

The above-mentioned comparison of surface area and time assume that the radius R1 of the first circle and the radius R2 of the second circle remain unchanged. -10-

Claims

CLAIMS

I. 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, characterised in that the outer casing is shaped to enclose a first substantially cylindrical volume and a second substantially cylindrical volume and wherein the first and second substantially cylindrical volumes are adjacent, tangent or overlapping.

2. A refrigeration beam according to claim 1, wherein the outer casing includes a first arcuate section that defines the first volume and a second arcuate section that defines the second volume, and wherein the first pipe is located in the first volume and the second pipe is located in the second volume.

3. A refrigeration beam according to claim 2, wherein the first and second pipes are substantially parallel to each other and to a longitudinal axis of the outer casing.

4. A refrigeration beam according to claim 3, wherein the cross-section of the first arcuate section defines the arc of a first circle having a centre and a first radius and the first pipe is located substantially at the centre of the first circle, and the cross-section second arcuate section defines the arc of a second circle having a centre and a first radius and the second pipe is located substantially at the centre of the second circle.

5. A refrigeration beam according to claim 4, wherein the distance between the centre of the first circle and the centre of the second circle is more than the sum of the first radius and the second radius such that the first volume and the second volume are adjacent.

6. A refrigeration beam according to claim 4, wherein the distance between the centre of the first circle and the centre of the second circle is the same as the sum of the first radius and the second radius such that the first volume and the second volume are tangent.

7. A refrigeration beam according to claim 4, wherein the distance between the centre of the first circle and the centre of the second circle is less than the sum of the first radius and the second radius such that the first volume and the second volume are overlapping.

8. A refrigeration apparatus comprising at least one refrigeration beam according to any preceding claim, and a source of cooling fluid connected to the first and second pipes.

9. A refrigeration apparatus according to claim 8, wherein the source of cooling fluid is a condensing unit.

10. A refrigeration beam substantially as herein described and with reference to the drawings.