GB2199744A

GB2199744A - Heat emitting draught screen

Info

Publication number: GB2199744A
Application number: GB08800511A
Authority: GB
Inventors: Archibald William Ker Mcgregor
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-01-10
Filing date: 1988-01-11
Publication date: 1988-07-20
Anticipated expiration: 2008-01-11
Also published as: GB2199744B; GB8800511D0

Abstract

A draught screen consists of several panels 2 hinged together and arranged to partially enclose a person 1 requiring warmth. The inward facing surface 4 of each panel is heated by an electric element so that the said surface radiates infra- red heat towards the said person. A sheet of material which transmits infra-red thermal radiation may be located adjacent to but not touching the said heated surface so that a closed air gap is formed between said sheet and said surface. Alternatively, a layer of fabric material may be bonded to the said heated surfaces. The unheated surface 5 of each panel may be provided with a surface finish or foil which has a high reflectivity for thermal radiation. The screen may be arranged so that the unheated, reflective surfaces face inwards towards the said person. <IMAGE>

Description

HEAT EMITTING DRAUGHT SCREEN This invention relates to the provision of heat for bodily comfort. It is often difficult and expensive to provide adequate bodily warmth for individual persons in large spaces which are cold and draughty such as workshops, warehouses, factories, offices and rooms in old houses. The problem may be specially severe in the case of elderly or infirm persons particularly when they are stationary or sedentary.

Conventional devices for alleviating the problem, such as electric radiator bar fires and electric convector heaters, are not very effective because they provide either intense and unidirectional radiant heat with no protection from draughts in the case of electric radiator bar fires or else a localised stream of warm air which rapidly rises upwards and away from the person being heated in the case of electric convector heaters.

Moreover, such devices are quite expensive to run with a minimum electrical rating normally not less than 1000 Watts. Conventional draught screens cost nothing to run but, thought they reduce cooling by draughts, they provide no heat at all.

The invention is based upon the realisation that for the provision of cheap and effective bodily warmth in cold and draughty spaces it is necessary to reduce body heat loss by simultaneously reducing cold draughts and by providing low intensity radiant heat.

According to one aspect of the present invention there is provided a screen comprising two or more hinged panels which surrounds or partially surrounds the person who requires warmth. The screen reduces body heat loss by reducing draughts. In addition, the inward facing surfaces of the panels are provided with heating elements, electrical or otherwise, which cause the said surfaces to become warm and radiate low intensity infra-red heat towards the said person. The consequent reduction of both convective and radiative heat loss from the body provides a substantial degree of thermal comfort at a low energy cost.

In order to maximise the useful heat output from the inward facing surfaces of the panels, a layer of thermal insulation material is located between the said heated inward facing surfaces and the unheated outward facing surfaces of the panels.

In order to maximise the infra-red radiative proportion of the total heat output from the inward facing heated surfaces of the panels a layer of material with a high transmissivity for infra-red radiation may be located over the said heated surfaces in such a way as to enclose a sealed air gap which will inhibit convective heat output from the said surfaces and thus increase the proportion of total heat output which is in radiative form. This will increase the effectiveness of the invention as a radiant heating device.

Alternatively, if a sealed air gap is not incorporated, the heated surfaces of the panels may be covered with a fabric material bonded to the said surfaces so that the fabric is heated by thermal contact and emits radiant heat to the surroundings. The fabric, having a lower thermal conductivity than that of the surface to which it is bonded, will feel cooler to the touch than the uncovered surface even though its temperature is the same.

In addition, if the fabric has a pile or felt or woven texture then the fabric will better inhibit convective heat trans to the adjacent air thus increasing the radiative proportion of total heat transfer to the surroundings.

The presence of a fabric, preferably of relatively low thermal conductivity and/or preferably having a pile or felt or woven texture is especially advantageous in optimising or enhancing the performance of a heating panel having an electrical heating element of relatively low wattage per unit area. , According to a second aspect of the present invention, there is provided a heat emitting panel incorporating a heating element adapted to operate at a relatively low heat output per unit area, for example below 1500 watts per square metre, and having bonded to the heat-emitting surface of the panel a layer of fabric material of lower thermal conductivity than the underlying material and/or having a pile or felt or woven texture.

In addition, the unheated surfaces of the panels which normally face outwards and away from the person being heated may be provided with a surface finish or layer which has a high reflectivity for thermal radiation.

If it is desired to use the screen as a simple draught screen without energising the heating elements, the whole screen may be reversed. The reflective surfaces, which now face inwards, will improve the heating effectiveness of a conventional radiative heater such as an electric bar fire or open solid-fuel fire by reflecting thermal radiation on to the back and sides of a person who is facing the fire.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows in plan view a typical arrangement of the heat emitting draught screen relative to a seated person requiring warmth; Figure 2 shows a section through a panel of the heat emitting draught screen according to a first embodiment of the invention; Figure 3 shows in plan view a typical arrangement of the draught screen in the reversed position, relative to the person requiring warmth and an external source of radiative heat such as an electric bar fire; and Figure 4 shows a section through a panel of the heat emitting draught screen according to a second embodiment of the invention.

Referring to the drawing the heat emitting draught screen comprises three panels 2 connected by hinges 3. The panels are arranged round the person 1 requiring warmth.

The panels rest on the floor and extend to about head height. Each panel comprises a simple rectangular frame (not shown) to which sheets 4 and 5 of an electrically insulating material, such as plywood, are affixed round the edges. An electrical resistance heating element, in flat sheet form 6 is locked adjacent to the inner surface of sheet 4 and may be bonded to the said inner surface. The element covers most of the area of the said inner surface. A layer of thermal insulation material 7 is located between the element and the sheet 5.

The element heats sheet 4.

A thin layer 8 of material which has a high transmissivity to infra-red thermal radiation, such as polyethylene, may be attached round the edges to the frame of the panel to form a sealed air gap 9 adjacent to the outer surface of sheet 4.

Alternatively, instead of layer 8, a layer of fabric material 12 may be bonded to the heated surface of the panels, as shown in Figure 4. The fabric material is a felt or a woven hairy fabric of relatively low thermal conductivity.

A surface finish or foil with a high reflectivity for thermal radiation 10 may be applied or attached to the outer surface of sheet 5.

In Figure 1 is shown a typical arrangement of the heat emitting draught screen relative to the person requiring warmth. The electrical heating elements in all three panels are energised and sheet 4 warms up and radiates infra-red thermal energy towards the said person.

At the same time the screen provides shelter from draughts.

In Figure 3 is shown in alternative arrangement where an external source of radiative heat such as an electric bar fire or open coal fire 11 is available. The screen is now reversed so that the high reflectivity surfaces of the panels face inwards towards the person 1 requiring warmth. Radiation from the said fire is thus reflected towards the sides and back of the said person thereby increasing the heating effectiveness of the said fire.

At the same time the screen provides shelter from draughts.

In this alternative arrangement the electrical heating elements in the screen are not normally energised.

A heat emitting draught screen similar to that described herein has been tested and was found to provide adequate thermal comfort for a sedentary person in an unheated room with an air temperature of about 70C.

The screen had a heat-emitting surface of approximately 1 square metre area and the rate of consumption of electricity was about 300 watts. Thus, the present invention envisages heat outputs in the range up to 1500 watts per square metre.

In a modification within the scope of the present invention, a single panel of low wattage has a fabric surface for optimising the radiative heat output.

Claims

1. A heat emitting draught screen comprising mutually hinged panels in each of which heating elements are incorporated so that inward facing surfaces of the said panels emit radiant heat towards a person requiring warmth.

2. A heat emitting draught screen according to claim 1, wherein a layer of material with high transmissivity to infra-red thermal radiation is located adjacent to the radiant heat emitting surfaces of the panels in such a way as to reduce convective heat transfer from said surfaces to the surrounding air.

3. A heat emitting draught screen according to claim 1 wherein a fabric material is bonded to the heated surfaces of the panels so that, for a given total heat emission, convective heat transfer is reduced, radiative heat transfer is increased and the panels feel cooler to the touch.

4. A heat emitting draught screen according to claim 1 or claim 2 or claim 3, wherein the surfaces of the panels which are not heated are provided with a surface finish which has a high reflectivity for thermal radiation.

5. A heat emitting panel incorporating a heating element adapted to operate at a relatively low heat output per unit area, for example below 1500 watts per square metre, and having bonded to the heat-emitting surface of the panel a layer of fabric material of lower thermal conductivity than the underlying material and/or having a pile or felt or woven texture.

6. A heat emitting panel according to claim 5 wherein the heating element is an electrical element in sheet form.

7. A heat emitting draught screen substantially as described herein with reference to the accompanying drawings.