GB2453142A

GB2453142A - Temperature control

Info

Publication number: GB2453142A
Application number: GB0718836A
Authority: GB
Inventors: Andrew Beever
Original assignee: Polypipe Building Products Ltd
Current assignee: Polypipe Building Products Ltd
Priority date: 2007-09-26
Filing date: 2007-09-26
Publication date: 2009-04-01
Also published as: GB0718836D0

Abstract

A system 1 for maintaining the temperature of an internal space 2, e.g. an office at a desired level, has a device 3 made up of a phase change material, e.g. a hydrated salt, which absorbs heat from the air to affect a phase change of the material, thereby cooling the internal space 2, and limiting the temperature above which the space 2 will reach. The device 3 may take the form of a number of pouches of material placed in the ceiling void 7 of the space 2. A fan 8 may be provided to aid in cooling the ceiling void 7 to cool the device 3 at times when the device 3 does not need to operate e.g. during the night.

Description

A SYSTEM, DEVICE AND METHOD FOR TEMPERATURE CONTROL The invention relates to a system, device and method, particularly for maintaining ambient temperature of a room at a desired level.

Environments such as rooms of a building, particularly offices, can become uncomfortable as temperature rises. In order to alleviate any discomfort caused by an increase in temperature, air conditioning is often used to maintain the ambient temperature of a room at an acceptable, desired, level. The air conditioning can be provided by a single system operating throughout a whole building with each room being "fed" by the system, or individual air conditioning units can be provided for each room. These systems are expensive to install and to run.

It is accordingly an object of the invention to seek to mitigate these disadvantages.

According to a first aspect of the invention there is provided a system for maintaining ambient temperature of a room at a desired level, comprising a device including a phase change material adapted to absorb heat from the ambient air and effect a phase change of the material whereby to maintain the ambient temperature at the desired level.

Using the invention it is possible to provide a comfortable room temperature during periods of warmer weather without the need to provide air conditioning.

The phase change material may comprise a salt solution such as a hydrated salt which can change from a solid phase to a liquid phase on absorption of heat. It will be understood that any other suitable phase change material may be used, and that the phase change may be any one of solid phase to liquid phase, liquid phase to solid phase, solid phase to gaseous phase, and liquid phase to gas phase.

Preferably the salt solution may change phase from solid to liquid within the range 20°C to 30°C, suitably preferably at substantially 28°C.

In a preferred but not exclusive embodiment, the device may comprise at least one plastic pouch which may contain the phase change material. In a yet further preferred but not limiting embodiment, there may be a plurality of plastic pouches, each containing the phase change material. The pouches may be separate, or individual, pouches.

The system may be such that the device or devices may be positioned in a roof space of a room. The roof space may be defined by a suspended ceiling of the room, and the or each pouch may be mounted on, as by being laid on, ceiling panels of the suspended ceiling.

The system may also comprise means to circulate ambient air over the or each pouch.

This can assist in effecting a reverse phase change, particularly when said means may comprise a fan mounted in a boundary wall of the room. The wall may suitably be an external wall, and the fan may be mounted in the roof space above the or each pouch.

There may also be provided means to control the running period of the fan, which control means may suitably be a timer. This is a simple yet effective, though non-limiting, means for controlling the fan.

Suitably, the timer may be adapted to control the fan to be operative for substantially twelve hours.

According to a second aspect of the invention there is provided a device for maintaining ambient temperature of a room at a desired level, comprising a phase change material.

As disclosed hereinbefore, the device may comprise a plastic pouch containing the phase change material. The plastic is relatively thin so as not to hinder absorption of heat by the phase change material, and also can provide for flexibility of the device in say a liquid phase of the phase change material where the said material may exist in a substantially solid (which could include a paste or gel) phase and a substantially liquid phase.

According to a third aspect of the invention there is provided a method of maintaining ambient temperature of a room at a desired level, comprising providing at least one device including a phase change material in operative thermal communication with the room and extracting heat from the room as external temperature rises by absorption of heat by the device to effect a phase change of the phase change material from one phase to a second phase.

The method may also suitably comprise the step of reversing the phase change to return the material to the one phase.

The method may also include the step of laying the at least one device in a cavity above a suspended ceiling of a room.

A system, device, and method for maintaining ambient temperature of a room at a desired level.

The Figure shows schematically an office in vertical cross-section incorporating a system, device and method according to the invention.

Referring to the drawing, there is shown a system 1 for maintaining ambient temperature of a room, in the embodiment an office 2, at a desired level, comprising a device 3 including a phase change material such as a hydrated salt adapted to absorb heat from the ambient air and effect a phase change of the material, whereby to maintain the ambient air temperature at the desired level.

As shown in the drawing, the office 2 of the particular embodiment shown has an external boundary wall 4 (a cavity wall in the embodiment) and a suspended ceiling 5 which creates with the wall 4 the office space 6 and also a roof or ceiling space 7 above (as viewed) the suspended ceiling 5.

The device 3 is in the embodiment comprised of a plurality of individual, separate, plastic pouches, each pouch containing a phase change material. Each pouch is sealed to provide a self-contained unit of substantially pillow or meniscus configuration. The pouches are mounted as by being laid on the upper (as viewed) surface of the suspended ceiling 5 so the pouches lie in the roof or ceiling space 7. The pouches 3 are in touching engagement, and there may be as many as is or are required.

There is also in the system a means 8 to extract air from the roof or ceiling space. This is an air circulating or extraction fan which is mounted in the boundary wall 4 for extracting air from the roof or ceiling space 7 to the outside 9 of the building. There is a timer, not shown, for controlling the fan 8 to be on for a certain period and off for a certain period. In the embodiment the timer is operative to switch the fan 8 on for twelve hours and off for twelve hours. The "on" period is in the embodiment, at night.

In use the system I using the device and method described with reference to the drawing maintains a comfortable room temperature for the office during periods of warm, or wanner than usual, weather without the need for air conditioning.

The devices 3 are assumed to be in the solid phase when they are installed in the roof or ceiling space 7. The salt solution used in the embodiment changes phase from solid to liquid at substantially 28°C. In order to achieve this phase change a significant absorption of heat takes place (which heat energy is subsequently released when the material returns to the solid phase from the liquid phase).

With the devices 3 in place on the suspended ceiling 5, if the external temperature rises so that the office space 6 becomes warmer, the phase change material warms up too, and at about 28°C, phase change from solid to liquid is effected. However, in order to achieve this the devices 3 need to absorb much more energy than that provided by a simple temperature rise. Therefore, the devices 3 absorb heat energy from the air of the office space 6, to complete the phase change. This in turn has the effect of lowering the temperature of the ambient air in the office space to a desired, comfortable level and moreover, to maintain the material in the liquid phase, heat is continuously absorbed from the office space 6 ambient air. There is therefore not sufficient thermal energy available to increase the ambient air temperature of the office space.

Stated in another way, the temperature of the matenal rises as it absorbs heat. Unlike conventional storage materials, however, when the material reaches the temperature at which it changes phase (its melting point) it absorbs large amounts of heat without a significant rise in temperature.

At the end of the (working) day, the office 2 is usually vacated and the external air temperature begins to fall, so that the temperature of the office space 6 also falls. The timer then actuates the circulation fan 8. This draws air from throughout the building, which is generally at a temperature which is lower than the warmest air within the roof or ceiling space 7. The fan 8, controlled by the timer, runs throughout the night to extract heat from the roof or ceiling space 7 and exhaust it to the outside 9 of the building. During this time, the phase change material releases the thermal energy previously stored so that it reverts to the solid phase from the liquid phase. The system I is then ready for repeating the cycle during the next working day.

Thus, again stated in another way, when the ambient temperature around the liquid material falls, it solidifies, releasing its stored latent heat.

Thus the embodiment of the invention described with reference to the drawing can provide a lower office temperature without expensive running of air conditioning system, the cost being reduced to the running of the low power circulation fan for say a 12 hour period.

It will be understood that the expression "phase change material" (PCM) used herein with particular reference to the drawing is a substance with a high heat of fusion which, melting and solidifying at certain temperatures, is capable of storing or releasing large amounts of energy. In general and in preferred usage as with the invention herein, the most practical PCM is one which utilises a solid-liquid change, for example hydrated salt(s). It will also be understood that PCMs can be broadly grouped into two categories; "Organic Compounds" (such as waxes, vegetable extract, polyethylene

A

glycol) and "Salt-based Products" (such as Glauber's salt). The most commonly used PCMs are salt hydrates, fatty acids and esters, and various paraffins (such as octadecane).

Claims

CLAIMS: 1. A system for maintaining ambient temperature of a room at a desired level, comprising a device including a phase change material adapted to absorb heat from the ambient air and effect a phase change of the material whereby to maintain the ambient temperature at the desired level.
2. A system according to Claim I, the phase change material comprising a salt solution which changes from a solid phase to a liquid phase on absorption of heat.
3. A system according to Claim 2, comprising a hydrated salt.
4. A system according to Claim 3, the salt solution changing phase from solid to liquid within the range 20°C to 30°C.
5. A system according to Claim 4, the phase change temperature being substantially 2 8°C.
6. A system according to any preceding claim, the device comprising at least one plastic pouch containing the phase change material.
7. A system according to Claim 6, there being a plurality of plastic pouches each containing the phase change material.
8. A system according to Claim 7, the plastic pouches being separate.
9. A system according to Claim 7 or Claim 8, in a roof space of a room.
10. A system according to Claim 9, comprising a suspended ceiling of a room, the said plastic pouches being mounted on ceiling panels of the suspended ceiling.
11. A system according to Claim 10, the said pouches being laid on the ceiling panels of the suspended ceiling.
12. A system according to Claim 10 or Claim 11, comprising means to circulate ambient air over the or each pouch.
13. A system according to Claim 12, the air circulation means comprising a fan mounted in a boundary wall of the room.
14. A system according to Claim 13, the boundary wall being an external boundary wall.
15. A system according to Claim 14, comprising a means to control the running period of the fan.
16. A system according to Claim 15, the control means comprising a timer.
17. A system according to Claim 16, the timer being adapted to control the fan to be operative for substantially twelve hours.
18. A system for maintaining ambient temperature of a room at a desired level, substantially as hereinbefore described with reference to the accompanying drawing.
19. A device for maintaining ambient temperature of a room at a desired level, comprising a phase change material.
20. A device according to Claim 19, comprising a plastic pouch containing the phase change material.
21. A device according to Claim 20, the pouch being flexible in one phase of the phase change material.
22. A device according to any of Claims 19 to 21, the phase change material having a substantially solid phase and a substantially liquid phase.
23. A device according to Claim 22, the material comprising a salt solution which effects a phase change from a solid phase to a liquid phase within the temperature range 26°C to 3 0°C.
24. A device according to Claim 23, the material having a phase change temperature of substantially 28°C.
25. A device for maintaining ambient temperature of a room at a desired level, substantially as hereinbefore described with reference to the accompanying drawing.
26. A method of maintaining ambient temperature of a room at a desired level, comprising providing at least one device including a phase change material in operative thermal communication with the room and extracting heat from the room as external temperature rises by absorption of heat by the device to effect a phase change of the phase change material from one phase to a second phase.
27. A method according to Claim 26, including the step of reversing the phase change to return the material to the one phase.
28. A method according to Claim 26 or Claim 27, the phase change being effected within the range 26°C-30°C.
29. A method according to Claim 28, the phase change being effected at substantially 2 8°C.
30. A method according to any of Claim 26 to 29, comprising laying the at least one device in a cavity above a suspended ceiling of the room.
31. A method of maintaining ambient temperature of a room at a desired level, substantially as hereinbefore described.