Title

Central Heating System Based on Heat Pipe Radiators

Field of the Invention The invention relates generally to a heating system that relies on conductive flow of a medium to transport heat energy to or from a centralized location to an area to be heated. In particular the invention is related to a new type of radiator construction to increase the efficiency of heat energy transfer in the radiator.

Background to the Invention

Most heating systems use a fluid with a high specific heat content to conduct heat from a centralized heat source to areas that are required to be heated. For example domestic hot water systems use water to extract the heat from a boiler, and copper pipes to transport the hot water to the required area. So called "radiators" are sealed metal panels that radiate thermal energy when they are heated to a specific temperature by the hot fluid (water). The amount of heat that is transferred to the room is proportional to the difference in temperature of the "radiator" and the ambient temperature of the room. There are several problems with existing heating systems.

A typical hot water system contains about 7501 of water and 350kg of steel. The specific heat capacity, C, of water is large, therefore a significant amount of heat energy must be introduced to the water/radiator system before the system can be heated to a temperature that enables a radiator to radiate heat efficiently. The large amount of energy required to heat the system is the cause of significant latency in the system, which means that accurate temperature control of the area to be heated is problematic.

To ensure adequate heating of the space, the "radiators" in the system must be heated to a specific temperature (generally 80 ⁰ C). The radiator panel will therefore cause 1 ^st degree burns to the skin of a young child, if the child places his hand or arm on a radiator at 8O ⁰ C. Radiators therefore need to be insulated (or run at a cooler temperature) in areas where children are likely to be present and this reduces the efficiency of the radiators at heating the space.

When the system is desired to be switched off, the system still contains a great amount of energy and takes time to cool. This makes quick control of the room temperature difficult, limiting accuracy of room temperature control and wastes a great deal of energy.

Japanese Patent publication number JP62131121 in the name of "Showa Aluminium Corporation" discloses a complicated system of water piping for a radiator heating system. A metallic inner pipe and an aluminium coated pipe to cause the working fluid (i.e. water) to evaporate. The vapour produced thus condenses to provide the latent heat of evaporation to heat the radiator. However, this system of heating a radiator was found to be inefficient due to poor heat exchange from condensation of the working fluid. Also the sealing, set-up and maintenance in such a radiator is extremely difficult and invariably leads to a short life and costly radiator. Further, in order for their radiator to be effective it needs to be plumbed into the hot water conduit so that the inefficiency in the cycling of the fluid is mitigated through better thermal conduct with the hot medium (water).

The present invention attempts to alleviate the above mentioned problems.

Object of the Invention

It is an object of the invention to provide a new and improved heating system.

It is a further object of the invention to provide an improved fluid radiator for use in a heating system, in particular a home heating system.

Summary of the Invention

According to the present invention there is provided, as set out in the appended claims, a heating system using a liquid for heat transmission incorporating a fluid based heat radiator mechanically separated from said liquid.

Preferably the heat radiator is comprises of one or more heat pipes. Suitably, the heat pipe is an evacuated heat pipe with a lining of a material, which allows capillary action.

Ideally the heat radiator is comprises of convective fins.

Preferably the heat pipe is thermally coupled to said liquid conduit to form a thermal joint to provide for thermal heat transfer between said liquid conduit and said heat pipe. The heat radiator can be mouldable or attachable to the liquid conduit to form one mechanical piece.

Preferably the thermal coupling can be adjustable thereby varying the thermal conductivity through the thermal joint formed by the conduit and the heat pipe. Ideally the heating system can incorporate a pre-user or user-set thermostatically operable clamping mechanism, to clamp the heat pipe to the liquid conduit.

In one embodiment the heat radiator is removable. The integrity of said liquid conduit is unaffected. Preferably the heat radiator can be attached in varying positions on the liquid conduit. In a preferred embodiment the liquid in the conduit is water based and the liquid conduit is copper based. In another embodiment the heat pipe fluid is mainly composed of water and/or water vapour.

In another embodiment there is provided a radiator for use in a heating system, comprising: at least one heat pipe, said heat pipe comprising means to be thermally coupled to a separate heat transmitting liquid conduit; wherein said radiator and said liquid conduit are mechanically separated from each other. The thermal coupling allows for thermal transfer of heat from said heat transmitting liquid conduit to said heat pipe to heat said radiator. Ideally, the heat pipe comprises a fluid.

Suitably the thermal coupling means comprises adjusting means, thereby allowing the varying of the thermal conductivity between said heat pipe and heat transmitting liquid conduit when said heat pipe is coupled to said heat transmitting liquid conduit.

Preferably said adjusting means comprises a clamp element to clamp said heat pipe to said heat transmitting liquid conduit. The thermal coupling means can comprise a thermal block to couple said heat pipe and heat transmitting liquid conduit.

It will be further appreciated that the new radiator design is lightweight and does not require connection to the working fluid. Therefore these radiators can be made easily detachable from the heating system. This would allow removal from the wall for decorating or to move radiators to different parts of the room for aesthetic reasons, or to enable room functionality to be changed, i.e. converting from sitting room to a bedroom, to provide a user with additional flexibility, without requiring isolation and draining of the heating system.

Brief Description of the Drawings The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which: -

Figure 1 illustrates a conventional heating system;

Figure 2 illustrates an embodiment of the inventive heating system;

Figure 3 illustrates one embodiment of the thermal coupling according to the present invention; and

Figure 4 illustrates a second embodiment of the thermal coupling according to the present invention.

Detailed Description of the Drawings Referring to figure 1 a conventional hot water heating system is illustrated, generally indicated by the reference numeral 1. Hot water from a boiler (not shown) flows in via a hot water pipe 2 and through a radiator 3. The radiator 3 is heated by allowing convective heating from the hot water supplied from the pipe 2. Cold water exits the radiator 3 and returns via the cold return pipe 4 to the boiler (not shown). This type of heating system is known.

Referring to figure 2 a heating system according to the present invention is illustrated generally indicated by the reference numeral 10. In this new heating system the hot

water from the boiler (not shown) does not flow through the radiator 3 via the pipe 2. Instead a radiator 6 is provided and comprises at least one or more heat pipes 7. The heat pipe 7 is clamped to the hot water pipe 2 so that heat is transmitted to the radiator 6 from the not water pipe 2 via the heat pipes 7 effectively and efficiently. The heat pipe 7 can be clamped onto the hot water pipe 2 using any suitable type of coupling or means 8.

It will be appreciated that the water based radiator 3 is replaced with a mechanically separated radiator 6 using the heat pipes, that are mechanically separated from the hot and/or cold water pipes 2, 4. The radiator 6 does not use any liquid from the boiler (not shown) to heat, i.e. no water from the heating system enters the heat pipe radiator. This allows the heat pipe based radiator 6 to be clipped onto an existing hot water conduit (such as a copper pipe). In addition, since the heat pipes are mainly evacuated the amount of water in the system drops dramatically and the inertia of the heating system is reduced thereby improving the temperature control and efficiency of the system. It will be appreciated that the radiator 6 can be easily moved when decorating a room or area or if changes in the position of the radiator in the room are required.

The heat pipes 7 are typically evacuated pipes with a lining of a material, which allows capillary action, filled with a small amount of fluid, which will evaporate at the temperature required. When there is a temperature gradient across the heat pipe 7, i.e. one end is hotter than the other, the fluid evaporates absorbing enormous amounts of heat because of the high latent heat of vaporisation. This evaporant then flows down the tube towards the cooler end where condenses. At the condensation point this heat is deposited thereby efficiently removing the heat from the hot end of the pipe. The condensated fluid is pulled back to the hot end of the pipe by capillary action by the inserted lining. When correctly designed for the temperature of interest these heat pipes respond instantaneously. For more information on the general principle of heat pipe devices please refer to Grover, G.M., T. P. Cotter, and G. F. Erickson (1964). "Structures of Very High Thermal Conductance". Journal of Applied Physics 35 (6).

Typically a heat pipe can dissipate 20 W through an area of 1 cm ² , so a large radiator of 2 KW would require heat pipes to be in contact with 100 cm ² or roughly 1 meter by 1 cm of pipe. This does not sound unreasonable. Greater efficiencies are possible with

heat pipes and there is great potential of being able to design much smaller heat pipe based radiators. It will be appreciated that the heat pipe material can be designed to have a thermal conductivity a 1000 times higher than copper. These designs are known in the art of improved thermal properties of materials, for example Thermacore International, www.thermacore.com and CRS Engineering, www.heatpipes.com.

It will be appreciated that the thermal coupling of the heat pipe 7 to the hot water pipe or conduit (and/or the cold water pipe or conduit for return flow) is critical to efficient operation of the present invention. The invention can utilise an adjustable clamping mechanism in order to control the thermal transfer between the hot water pipe 2 and the heat pipe 7. The adjustability of the clamping mechanism allows the temperature of the heat pipe 7 to be adjusted, and thus control the temperature of the radiator. This can even be done thermostatically using methods based on expansion of dissimilar metals. To improve the thermal heat transfer from the water feed pipe 2 to the heat pipe 7 designs based around flowing that water around the heat pipe could be possible. However this would involve breaking into the water feed and would not be ideal.

Referring to figure 3 illustrates an example of the thermal coupling between the heat pipe 7 and the hot water pipe 2. One end of the heat pipe 7 is adapted to be clamped to the hot water pipe 2 by a clamping element 11. The clamping element 11 can be adjusted by clamping screws 12 and 13, which can vary the thermal contact area and the tightness of the joint formed between the heat pipe 7 and the hot water conduit 2. In addition a thermal paste can be used to improve the thermal conductivity of the joint. By changing the thermal contact area or for a given thermal conduct area the tightness or level of fit better the contacting surfaces, i.e. between the heat pipe and the hot conduit. For instance, a metallic, for example copper, plate of area 1 cm ² , will allow up to 2OW of heat to pass through in either direction. For the same fit, and thermal circumstances (i.e. same thermal gradient) there is a linear dependence between contact area and the thermal transmission, hence a 2 cm ² will be able to transmit 4OW. Clearly, by mechanically changing the area of contact by the adjustable clamp 11 between the heat pipe and the heat conduit, thermal variability in the heat dissipated by the heat pipes, and hence the radiator can be achieved. It will be appreciated that other adjusting means can be provided to vary the thermal conductivity of the joint. It will be appreciated that

the clamping allows for the expansion of dissimilar materials (in the main metals) to control either the thermal contact area or the tightness of the thermal coupling (in a similar way as described above).

Referring to figure 4 illustrates an alternative thermal coupling arrangement between the heat pipe 7 and the hot water pipe 2. The heat pipe 7 can move sideways so that contact area can be varied. Fixing of the heat pipe can be achieved by screwing the heat pipe to a thermal block 14 via slotted elements (not shown) that slot (or screwed) into the base of the heat pipe 7. Essentially the thermal block 14 acts like a cap to thermally couple the heat pipe 7 with the hot water pipe 2. The thermal block 14 can be composed partially of thermal material (such as plastic) so as to enhance thermal variation induced by translation of the heat pipe 7. Also the thermal block 14 can be composed of one or more heat pipes that are separate from the main heat pipe. This would allow effective heat transfer from all sides of the heat conduit pipe 2.

As can be seen from the figures the inventive radiator basically has one or more heat pipes 7 of similar or dissimilar dimensions (round, square etc) in contact with the water feed. This or these heat pipes 7 can be designed to have thermal radiators (such as heat sinks) attached. The heat pipes 7 can be designed to maximise the heat transfer and maybe constructed diagonally across the heat radiator.

In another embodiment it is envisaged that a section of the pipes/conduit itself, if not all the pipes/conduits, could be replaced with heat pipe conduits. This would not be practical today because of cost and efficiency (because of the heat flux through heat pipe for given diameter pipe). If so the amount of water and latency of the system would dramatically drop and efficiency could be improved even further.

It will be appreciated that by significantly reducing the liquid, i.e. water, in a water based central heating system, the amount of energy required to heat at the start, and control during operation is significantly reduced thereby increasing the heating efficiency of the system. Also because the radiators do not form part of the hot fluid flow, i.e. hot water from the heater boiler does will not flow directly through these radiators, the induced back pressure on the water pump will be greatly reduced, hence

further reducing pump energy consumption and wear and tear pump life of a pump will be greatly improved.

The words "comprises/comprising" and the words "having/including" when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.