WO2015136296A1

WO2015136296A1 - Improved heater

Info

Publication number: WO2015136296A1
Application number: PCT/GB2015/050730
Authority: WO
Inventors: Ross AITKEN
Original assignee: SA EQUIP LLP
Current assignee: SA EQUIP LLP
Priority date: 2014-03-14
Filing date: 2015-03-12
Publication date: 2015-09-17
Anticipated expiration: 2016-09-14
Also published as: GB2524076A8; GB2524076B8; GB2524076B; GB201404538D0; GB2524076A

Abstract

An improved heater for use in an explosive environment is described. The heater comprises a heating mechanism, the heating mechanism comprising a plurality of resistive heating elements, each resistive heating element defining a surface and an air movement mechanism adapted to move air over the resistive heating element surfaces. In at least one embodiment the heater is a space heater.

Description

IMPROVED HEATER

Field of the Invention

The present invention relates to improved heaters for use in explosive environments.

Background to the Invention

Organisations in the European Union must protect employees from explosion risk in areas with an explosive atmosphere in accordance with the ATEX 95 equipment directive. This directive harmonised the law across the EU and sets out the standards required for equipment intended to be used in potentially explosive atmospheres.

Particularly, equipment has to avoid the possibility of an "effective ignition source" being created. An effective ignition source is an event which, in combination with sufficient oxygen fuel in gas, mist, vapour or dust form, can cause an explosion.

The requirements of this directive make explosive environments difficult to make comfortable for people to work in from a temperature perspective.

Providing heating brings the risk of creating a number of the effective ignition sources listed in the ATEX directive, such as electric sparks and high surface temperatures.

Space heaters which are currently provided for space heating in ATEX environments have numerous safety features to prevent the possibility of electric sparks or high surface temperatures being generated. For example, the control system is often located remotely from heater itself in a non-explosive area to prevent possibility of electric sparks causing an explosion. Similarly, highly effective and efficient heating elements such as resistive heating elements are either not used at all or are used to heat the explosive environment indirectly by, for example, heating an oil filled heat exchanger which is then exposed to the explosive environment as it will not generate temperatures which are sufficiently high to create an effective ignition source.

Factors such as remote location of the control system and use of multiple heating methods make the portability of existing space heaters very poor Summary of the Invention

According to a first aspect of the present invention there is provided an improved heater for use in an explosive environment, the heater comprising: a heating mechanism, the heating mechanism comprising a plurality of resistive heating elements, each resistive heating element defining a surface; and

an air movement mechanism adapted to move air over the resistive heating element surfaces.

In at least one embodiment of the present invention, providing a heater which heats air by direct contact with resistive heating elements has the advantage that the weight of an additional heat transfer mechanism, to which the resistive heating elements are an indirect supplier of heat, is not required. This significantly reduces the weight of the heater with the result that the heater is portable.

The heater may be a space heater.

At least one of the resistive heating elements may be planar. Alternatively or additionally, at least one of the resistive heating elements may be coiled.

In a preferred embodiment, at least one of the resistive heating elements is both coiled and planar.

The/each resistive heating element may be a planar spiral.

Alternatively, the/each resistive heating element may be serpentine. The/each resistive heating element may define an external boundary. The/each resistive heating element external boundary may be

substantially circular, the/each resistive heating element having a resistive heating element diameter.

The resistive heating elements may be arranged in series.

The resistive heating elements may be arranged such that the elements lie perpendicular to a heating element axis.

The air movement mechanism may be adapted to move air in an air flow direction.

The air flow direction may be substantially linear.

In a preferred embodiment the air flow direction may be parallel to the heating element axis.

The air movement mechanism may be adapted to blow air through the heating mechanism.

Alternatively, the air movement mechanism may be adapted to suck air through the heating mechanism.

The air movement mechanism may comprise a rotary section and a drive section, the drive section being adapted to impart rotational movement to the rotary section. The air movement mechanism may be a fan.

During rotation, the rotary section may sweep a rotation diameter.

The rotation diameter may be approximately the same size as the resistive heating element diameter. Having the rotation diameter approximately the same size as the resistive heating element diameter allows for the entire volume of air being moved by the air movement mechanism to pass over the heating elements and ensure that the entire surface area of the resistive heating elements are cooled by the flow of air. Under the ATEX ratings, "effective ignition sources" have to be avoided, this includes high-temperature surfaces which may cause ignition of an explosive vapour or gas. Maximising the utilisation of the flow of air over the resistive heating elements ensures efficient operation of the heater and assists in preventing overheating of resistive heating elements.

The rotary section may rotate around a rotation axis.

In a preferred embodiment, the rotation axis and the resistive heating element axis are parallel and, preferably, coincidental. Providing a rotary section which is aligned with the resistive heating element axis and of similar dimensions to the resistive heating elements helps maintain an even flow of air over the resistive heating elements, helping to prevent the resistive heating elements from overheating.

The rotary section may be adapted to rotate within a frame.

The frame may define an aperture adapted to receive the rotary section.

The provision of a rotary section frame assists in directing the air flow generated by the air movement mechanism towards the heating mechanism. The heating mechanism may have an inlet end and an outlet end, the inlet end and the outlet end being connected by a heating mechanism air flow path.

The heating mechanism air flow path may be defined by the resistive heating elements.

The heating mechanism air flow path may be convoluted.

The heating mechanism air flow path may be serpentine.

The heater may further comprise a housing.

The housing may be adapted to receive at least one of the resistive heating elements.

The housing may extend from the heating mechanism inlet to the heating mechanism outlet.

The housing may define an air flow path boundary.

The housing may define an internal profile complimentary to at least part of the resistive heating element external profile.

In one embodiment the housing may define an at least partially curved internal profile, the curve having a diameter slightly larger than the resistive heating element diameter.

The housing may further be adapted to receive the air movement device.

Such an arrangement permits the air movement mechanism to move air through the heating elements in the most efficient fashion as the housing keeps all the air that is flowing adjacent the resistive heating elements. This, again, helps to ensure that all the air that has been generated is used to take heat from the resistive heating elements, increasing the efficiency of the heater and preventing overheating. The heater may further comprise a control system, the control system being adapted to supply power to the heating mechanism and the air movement mechanism.

The control system may further be adapted to monitor the operation of the heating mechanism and the air movement mechanism.

The control system may comprise at least one temperature measurement device.

The/each temperature measurement device may be adapted to measure the surface temperature of the heating mechanism.

The control system may be adapted to alter the power supplied to the heating mechanism and the/or the air movement mechanism in response to a temperature measured by at least one of said temperature measurement devices. The control system may be adapted to reduce the power to the heating mechanism, partially switch off heating mechanism, fully switch off the heating mechanism, or increase the fan speed in response to a high-temperature reading obtained from the temperature measurement devices and vice versa. This allows for surface temperatures to be monitored such that the surface

temperatures do not reach a high enough level to exceed the maximum allowable surface temperature stipulated in the ATEX regulations and further, in some embodiments, allows for the control system to maintain the temperature of the air within an optimum band.

At least one temperature measurement device may be adapted to measure the surface temperature of heating mechanism distal the air movement mechanism. Locating the temperature measurement device as far away or as close to as far away from the air movement mechanism is advantageous as the cutting effect of the air on heating mechanism is lowest at this point, the air having absorbed heat from the earlier stages of the heating mechanism.

The control system may be adapted to switch off the heating mechanism should the heating mechanism surface temperature exceed 40 °C.

The control system may be further adapted to switch off the heating mechanism should the air movement mechanism fail.

The control system may be mounted to the heating mechanism or the air movement mechanism or, where provided, the housing.

In one embodiment, the control mechanism may be adapted to operate from 3-phase mains power.

In this embodiment there may three, six or nine resistive heating elements. Providing heating elements in multiples of three in a 3-phase mains power system keeps a substantially even load across the three phases.

In a preferred embodiment, there are nine resistive heating elements. Nine elements provides a large surface area over a number of elements, permitting each element to be relatively shorter than would be the case if three longer elements were used. Shorter or smaller heating elements gives a more constant heat through each element and more regular heating during start-up.

In other embodiments, the control mechanism may be adapted to operate 230 volts, or any suitable power supply.

The heater may further comprise structural members, the structural members being provided to support the mechanism and the air movement mechanism.

The structure members may include first and second end plates. The ends may be located perpendicular to the resistive heating element axis. Additionally, the ends may be located perpendicular to the rotary section rotation axis.

The first end plate may define a space heater inlet aperture permitting air to be drawn in to the space heater.

The second end plate may define a space heater outlet aperture, the outlet aperture adapted to allow heated air to leave the space heater.

The end plates may be arranged such that the inlet aperture and the outlet aperture are aligned with the heater element axis and/or the rotary section rotation axis.

The first and/or second end plate may be adapted to receive a flexible duct. A flexible duct can be used to allow, for example, cold air to be brought in from a specific location or hot air to be delivered to a specific location.

The first end plate may be connected to a first end of the housing, and the second end plate may be connected to the second end of the housing.

The first and second end plates may be adapted to support the housing and space the housing away from the surface upon which the heater, in use, is to be mounted.

The heater may further comprise connecting elements. The connecting elements may connect the first end plate and the second end plate.

The connecting elements may be adapted to protect the housing from impact damage.

The connecting elements may define handles.

The handles may include a strap. A strap may be provided to act as a support for a power supply cable The connecting elements may be a removable.

According to a second aspect of the present invention there is provided an improved heater for use in an explosive environment, the heater comprising: a heating mechanism;

an air movement mechanism adapted to move air over the heating mechanism; and

a heating mechanism housing, the heating mechanism housing adapted to channel air generated by the air movement mechanism over the heating mechanism.

According to a third aspect of the present invention there is provided a method of heating air in an explosive environment, the method comprising the steps of:

providing a heating mechanism comprising a plurality of resistive heating elements, each resistive heating element defining a surface; and

moving air directly over the resistive heating element surfaces.

It will be understood that preferred and alternative features associated with one aspect of the invention may be equally applicable to other aspects and have not been repeated for brevity.

Brief Description of the Drawings

An embodiment of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a portable space heater for use in an explosive environment according to an embodiment of the present invention;

Figure 2 is a section of the portable space heater of Figure 1 ; and Figure 3 is an end view of the housing of Figure 1 and showing one of the nine coiled resistive heating elements;

Detailed Description of the Drawings

Reference is first made to Figure 1 , a perspective view of a portable space heater, generally indicated by reference numeral 10, for use in an explosive environment, according to an embodiment of the present invention, and Figure 2, a section of the portable space heater 10 of Figure 1 .

The portable space heater 10 comprises a heating mechanism 12 and an air movement mechanism 14.

The heating mechanism 12 comprises nine coiled resistive heating elements 38 arranged in series along a heating element axis 16.

The air movement mechanism 14 comprises a fan 18 having a rotor 20 having a rotor diameter indicated by "RD" on Figure 2. The rotor 20 is adapted to rotate around a rotation axis 22; the heating element axis 16 and the rotation axis 22 being the same. Rotation of the rotor 20 moves air over the surface 40 of each of the nine coiled resistive heating elements 38, heat transferring from the heating elements 38 to the flow of air, heating the air.

The space heater 10 further comprises first and second end plates 24, 26. The first end plate 24 defines an inlet aperture 28 and the second end plate 26 defines an outlet aperture 30. The inlet aperture 28 and the outlet aperture 30 are defined particularly by connecting flanges 32, 34, the purpose of which will be discussed in due course.

Mounted between the first and second end plates 24, 26 is an internal housing 36. The housing 36 has an essentially horseshoe cross-section, best seen in Figure 3; an end view of the housing 36 of Figure 1 and showing one of the nine coiled resistive heating elements 38 for context.

As is shown in Figure 3, each coiled resistive heating element 38 is circular, having a coil diameter, indicated on the drawings as "CD". The housing 36 defines a curved section 60, the curved section 60 having a housing diameter, indicated on the drawings as "DD", the housing diameter DD being slightly larger than the coil diameter CD. This allows for a snug fit between the resistive heating elements38 and the housing 36. This will be discussed in due course.

The housing 36 as an open top 42 defined by a housing flange 44, and referring to Figure 2, mounted to the housing flange 44 are resistive heating coil support 46 and a control box 48.

The control box 48 contains a control system 50 which receives three- phase electric power from an external source and utilises this electric power to drive the fan 18 and the nine resistive heating coils 38.

As can be seen from Figure 2, the housing 36 extends between, and is connected to, the first end plate 24 to the second end plate 26. Particularly the housing 36 is aligned with first end plate inlet and the second end plate. The housing 36 and a control box underside surface 52 and a resistive heating coil support underside surface 54 defining a flowpath 56 between the inlet aperture 28 and the outlet aperture 30. As this flowpath 56 is sized to the dimensions of the coil diameter CD and the rotor diameter RD, contact is maximised between the air being moved by the fan 18 and the resistive heating elements 38. This arrangement maximises the efficiency of the space heater 10 as the air being moved is directed towards the surfaces 40 of the resistive heating elements 38 maximising the heat transfer opportunity which, in addition, minimises the possibility of the resistive heating coils 38 overheating.

Referring further to Figure 2, the coil 38a furthest from the fan 18 further includes a temperature sensor 70. The temperature sensor 70 feeds back the surface temperature of the coil 38A to the control system 50. As this coil 30 8A is furthest from the fan 18, the cooling effect of the air flow generated by the fan 18 is reduced at this location because the air generated by the fan 18 has been heated by its passage through the preceding coils 38. Therefore, the surface of the coil 38a furthest from the fan 18 is the most likely point for the surface temperature to exceed the limits set by the ATEX regulations, and creating a potential safety hazard. In response to a high reading from this temperature sensor 70, the control system can reduce the power to or switch off the heating coils 38, immediately reducing the risk of explosion.

The end plates 24, 26 space the housing 36 away from a surface upon which the space heater 10 is to be rested. Further protection for the housing 36 is provided by first and second frames 74, 76. These frames 74, 76 comprise a series of tubular members 78 which, in addition to protecting the housing 36 also serve as carrying handles to assist in the portability of the space heater 10.

Although the space heater 10 is portable, it may not was be convenient to locate it where heat is required or in a location were sufficiently cool there can be utilised by the air movement mechanism 14. To accommodate this, the end plate flanges 34, 36 are provided to permit flexible ducting (not shown) to bring cold air into the space heater 10 from a cold location and/or transfer heated air from the space heater 10 to different cold location. Various modifications and improvements may be made to the above described embodiment without departing from the scope of the invention. For example, although the space heater 10 is shown as having first and second frame 74, 76, these are not necessarily required for the space heater 10 to function effectively. They provide handles and protection but they add to the weight of the space heater 10 and can be removed.

Furthermore, although the space heater 10 is described as having nine heating coils, any number of heating coils can be used depending on the nature of the power supply and compliance with the ATEX regulations.

Claims

1 An improved heater for use in an explosive environment, the heater comprising:

a heating mechanism, the heating mechanism comprising a plurality of resistive heating elements, each resistive heating element defining a surface; and

2 The heater of claim 2, wherein the heater is a space heater.

3 The heater of either of claims 1 or 2, wherein at least one of the resistive heating elements is planar.

4 The heater of any preceding claim, wherein at least one of the resistive heating elements are coiled.

5 The heater of any preceding claim, wherein at least one of the resistive heating elements is both coiled and planar.

6 The heater of claim 5, wherein the/each resistive heating element is a planar spiral.

7 The heater of any of claims 1 to 3, wherein the/each resistive heating element is serpentine.

8 The heater of any preceding claim, wherein the/each resistive heating element defines an external boundary.

9 The heater of claim 8, wherein the/each resistive heating element external boundary is substantially circular, the/each resistive heating element having a resistive heating element diameter. 10 The heater of any preceding claim, wherein the resistive heating elements are arranged in series.

1 1 The heater of claim 10, wherein the resistive heating elements are arranged such that the elements lie perpendicular to a heating element axis. 12 The heater of any preceding claim, wherein the air movement mechanism is adapted to move air in an air flow direction.

13 The heater of claim 12, wherein the air flow direction is substantially linear.

14 The heater of either of claims 12 or 13, wherein the air flow direction is parallel to the heating element axis.

15 The heater of any preceding claim, wherein the air movement mechanism is adapted to blow air through the heating mechanism.

16 The heater of any of claims 1 to 14, wherein the air movement mechanism is adapted to suck air through the heating mechanism.

17 The heater of any preceding claim, wherein the air movement mechanism comprises a rotary section and a drive section, the drive section being adapted to impart rotational movement to the rotary section.

18 The heater of claim 17, wherein the air movement mechanism is a fan.

19 The heater of either of claims 17 or 18, wherein during rotation, the rotary section sweeps a rotation diameter.

20 The heater of claim 19, wherein the rotation diameter is approximately the same size as the resistive heating element diameter.

21 The heater of any of claims 17 to 20, wherein the rotary section rotates around a rotation axis. 22 The heater of claim 21 , wherein the rotation axis and the resistive heating element axis are parallel and coincidental.

23 The heater of any preceding claim, wherein the rotary section is adapted to rotate within a frame.

24 The heater of claim 23, wherein the frame defines an aperture adapted to receive the rotary section.

25 The heater of either of claims 23 or 24, wherein the provision of a rotary section frame assists in directing the air flow generated by the air movement mechanism towards the heating mechanism.

26 The heater of any preceding claim, wherein the heating mechanism has an inlet end and an outlet end, the inlet end and the outlet end being connected by a heating mechanism air flow path.

27 The heater of claim 26, wherein the heating mechanism air flow path is defined by the resistive heating elements.

28 The heater of either of claims 26 or 27, wherein the heating mechanism air flow path is convoluted.

29 The heater of claim 28, wherein the heating mechanism air flow path is serpentine.

30 The heater of any preceding claim, wherein the heater further comprises a housing.

31 The heater of claim 30, wherein the housing is adapted to receive at least one of the resistive heating elements.

32 The heater of any preceding claim, when dependent on claim 26 wherein the housing extends from the heating mechanism inlet to the heating mechanism outlet. 33 The heater of any of claims 30 to 32, wherein the housing defines an air flow path boundary.

34 The heater of any of claims 30 to 33, wherein the housing defines an internal profile complimentary to at least part of the resistive heating element external profile.

35 The heater of claim 34, wherein the housing defines an at least partially curved internal profile, the curve having a diameter slightly larger than the resistive heating element diameter.

36 The heater of any of claims 30 to 35, wherein the housing is further adapted to receive the air movement device.

37 The heater of any preceding claim, wherein the heater further comprises a control system, the control system being adapted to supply power to the heating mechanism and the air movement mechanism.

38 The heater of claim 37, wherein the control system is further adapted to monitor the operation of the heating mechanism and the air movement mechanism.

39 The heater of claim 38, wherein the control system comprises at least one temperature measurement device.

40 The heater of claim 39, wherein the/each temperature measurement device is adapted to measure the surface temperature of the heating

mechanism.

41 The heater of claim 40, wherein the control system is adapted to alter the power supplied to the heating mechanism and the/or the air movement mechanism in response to a temperature measured by at least one of said temperature measurement devices. 42 The heater of claim 42, wherein at least one temperature measurement device is adapted to measure the surface temperature of heating mechanism distal the air movement mechanism.

43 The heater of any of claims 40 to 42, wherein the control system is adapted to switch off the heating mechanism should the heating mechanism surface temperature exceed 40 °C.

44 The heater of any of claims 37 to 43, wherein the control system is further adapted to switch off the heating mechanism should the air movement mechanism fail.

45 The heater of any of claims 37 to 44, wherein the control system is mounted to the heating mechanism or the air movement mechanism or, where provided, the housing.

46 The heater of any of claims 37 to 45, wherein the control mechanism is adapted to operate from 3-phase mains power.

47 The heater of any preceding claim, wherein there are three, six or nine resistive heating elements.

48 The heater of claim 47, wherein there are nine resistive heating elements.

49 The heater of any of claims 37 to 45, wherein the control mechanism is adapted to operate 230 volts, or any suitable power supply.

50 The heater of any preceding claim, wherein the heater further comprises structural members, the structural members being provided to support the mechanism and the air movement mechanism.

51 The heater of claim 50, wherein the structure members includes first and second end plates. 52 The heater of claim 51 , wherein the end plates are located perpendicular to the resistive heating element axis.

53 The heater of either of claims 51 or 52, wherein the end plates are located perpendicular to the rotary section rotation axis.

54 The heater of any of claims 51 to 53, wherein the first end plate defines a space heater inlet aperture permitting air to be drawn in to the space heater. 55 The heater of any of claims 51 to 54, wherein the second end plate defines a space heater outlet aperture, the outlet aperture adapted to allow heated air to leave the space heater.

56 The heater of any of claims 50 to 55, wherein the end plates are arranged such that the inlet aperture and the outlet aperture are aligned with the heater element axis and/or the rotary section rotation axis.

57 The heater of any of claims 50 to 56, wherein the first and/or second end plate is adapted to receive a flexible duct.

58 The heater of any of claims 51 to 57, wherein the first end plate is connected to a first end of the housing, and the second end plate is connected to the second end of the housing.

59 The heater of any of claims 51 to 59, wherein the first and second end plates is adapted to support the housing and space the housing away from the surface upon which the heater, in use, is to be mounted.

60 The heater of any preceding claim, wherein the heater further comprises connecting elements.

61 The heater of claim 60, wherein the connecting elements connects the first end plate and the second end plate. 62 The heater of either of claims 60 or 61 , wherein the connecting elements are adapted to protect the housing from impact damage.

63 The heater of any of claims 60 to 62, wherein the connecting elements define handles.

64 The heater of any of claims 60 to 63, wherein the connecting elements are a removable.

65 An improved heater for use in an explosive environment, the heater comprising:

a heating mechanism;

an air movement mechanism adapted to move air over the heating mechanism; and

a heating mechanism housing, the heating mechanism housing adapted to channel our generated by the air movement mechanism over the heating mechanism.

66 A method of heating air in an explosive environment, the method comprising the steps of:

moving air directly over the resistive heating element surfaces.