IE20160086A1 - Liquid heating component - Google Patents

Abstract

A heating component 71, for use in a liquid heating apparatus, having a liquid contact surface shaped to assist convection in the liquid being heated to achieve even heat distribution through the heating process and avoid excess steam generation. The heating component may have a tapering aspect to part of its form and part of its form may be conical. The water contact surface may form one or more protrusions 74 and those protrusions may form peaks or ridges 77. The heating component may be used for heating any liquid such as water and may be used in any liquid heating device such as a kettle or saucepan. <Figure 7a>

Description

Background of the present invention Conventional electric kettles typically heat water using an electric element at or near the base of the interior of the water containing part of the kettle. The base is commonly flat and circular. This arrangement is designed to ensure the surfaces of the electric element are covered by water even when only small volumes of water are to be heated. The heating of small volumes of water is commonly encouraged as users are advised to only boil the volume of water that is required in the interests of energy efficiency.

The above described arrangement of a flat interior base is an inherently inefficient arrangement in its use of energy. This inefficiency is due to the mechanism of heat transfer from the electric element to the water that is to be heated. The conditions for creating heat transfer by convection is minimal. Without significant convection, there is no significant flow of water past or around the heating element. This results in water in the proximity of the heating element being heated significantly and commonly boiling before the majority of the volume of water is near boiling point. Boiling water near to the heating element forms bubbles of steam and those bubbles then travel upwards through the body of water. As the bubbles of steam pass through the cooler water, some of the heat of the steam is transferred to the water, causing the temperature of the water generally to rise and eventually reach the desired boiling point. This mechanism does not however deliver all the available heat energy from the steam bubbles to the water and a significant proportion of the steam in the bubbles reaches the surface of the water. The steam that does reach the surface is lost to the atmosphere and so consequently is the heat energy it carries with it. Steam condensate is commonly observed in significant volumes emanating from the spout of the kettle during the heating process. Any steam and consequent water vapour lost by the kettle during the heating process indicates an inefficiency in the heating mechanism. The purpose of an efficient kettle is to heat water to boiling point, not to create large amounts of steam.

Apart from the inefficient use of energy, the creation of steam can also have a detrimental effect on the environment in which the kettle is used. The loss of steam into the atmosphere of an environment such as that of a kitchen where commonly used creates a damp atmosphere. A damp atmosphere contributes to the growth of mold and the damage it causes, and associated health effects. Kettles are also commonly placed under fitted kitchen cabinets and the steam generated by kettles can cause damage to them.

Aim of the present invention The present invention aims to provide a more efficient means of heating water to boiling point than is currently achieved. To achieve this a means is required that minimises the creation of steam during the heating process. In order to minimise the creation of steam, heat delivered to the water must be mixed evenly so the temperature of all regions of the body of water held within the kettle is kept roughly the same and rises together. The water in proximity to the heating component must be caused to flow away from the component before it boils. This flow must ultimately circulate around the entire body of water in order to distribute the heat evenly. As the water reaches boiling point, there will inevitably be some boiling and creation of steam but this will occur at the end of the heating process and will be kept to a minimum. A kettle including such an invention will also be quieter in operation as the noise created by kettles is caused by bubble formation.

Summary of the present invention The present invention provides a heating component and a liquid heating apparatus as defined by the appended claims.

Brief description of the drawings Figures la to lc are dimetric, side and top views respectively of a heat transfer plate having a circular based, straight sided conical projection.

Figures 2a to 2c are dimetric, side and top views respectively of a heat transfer plate having a circular based, curved sided conical projection.

Figures 3a to 3c are dimetric, side and top views respectively of a heat transfer plate having a hexagonal based, curved and straight sided conical projection.

Figures 4a to 4d are dimetric, sides and top views respectively of a heat transfer plate having a flat sided projection forming a single, level ridge.

Figures 5a to 5c are dimetric, side and top views respectively of a heat transfer plate having a flat sided projection forming three level ridges orientated radially from the centre of the plate.

Figures 6a to 6c are dimetric, side and top views respectively of a heat transfer plate having a flat and curved sided projection forming six inclined and curved ridges oriented radially from the center of the plate.

Figures 7a to 7c are dimetric, side and top views respectively of a heat transfer plate having three separate flat and curved sided projections forming three level ridges oriented radially from the center of the plate.

Figures 8a to 8c are dimetric, side and top views respectively of a heat transfer plate having a circular curved sided projection forming a level circular ridge centered on the center of the plate.

Figures 9a to 9c are dimetric, side and top views respectively of a conical, helical heating component.

Figures 10a to 10c are dimetric, side and top views respectively of a heat transfer plate as shown in figure 2 having a flat, annular heating element attached to the underside. Figures 11a to 11c are dimetric, side and bottom views respectively of a heat transfer plate as shown in figure 4 having two flat, straight heating elements and two insulation panels attached to the underside.

Figure 12 is a dimetric view of a kettle incorporating a heat transfer plate as shown in figure 4.

Figure 13 is a section view of a kettle incorporating a heat transfer plate as shown in figure 8.

Figure 14 is a cross-section view of a kettle incorporating a heat transfer plate as shown in figure 4 including convection flow vectors according to flow simulation results.

Figure 15 is a cross-section view of a kettle incorporating a heat transfer plate according to an embodiment of the present invention including water temperature shading according to flow simulation results.

Figure 16 is a side view of a kettle incorporating a conical, helical heating component as shown in figure 9.

Detailed description of the present invention Figures 1 to 8 show various embodiments of heat transfer plates according to an aspect of the present invention. In the embodiments each plate forms at least part of the lower boundary of a water containing space within a water heating apparatus such as a kettle. In use, water comes into contact with the upper surface of the heat transfer plate. One or more heating elements of a type known in the art are attached to the underside of the plate by known means. The plate is formed from a thermally conductive material such as steel or other metal or ceramic. Heat generated by the heating elements is conducted through the plate to water in contact with the water contact surface. Heated water then moves by convection. The angled surfaces of protrusions from the heat transfer plate encourage heated water to rise in the water volume. Cold water is consequently drawn in from the outer regions of the water volume across the hot surfaces of the heat transfer plate. This continuous flow helps to evenly distribute heat delivered to the water volume. The temperature therefore rises much more evenly than in a conventional water heating arrangement. The continuous flow also helps to prevent water from boiling until the temperature of the water volume as a whole is close to boiling point. This has the effect of reducing heat lost by steam through the water heating process and consequently provides better energy efficiency over conventional technologies. The operation is also quieter due to minimising the formation of bubbles.

The thickness of the plate will be determined by the skilled person. A thinner plate saves materials cost in production. A thicker plate distributes heat more evenly over the water contact surface reducing hot spots and consequently premature boiling. The thickness may be variable. The protrusion or protrusions may be hollow or non-hollow i'e' filled in. A heating element may be moulded into the hollow of the protrusion to at least partially fill it in.

The plate may be formed by techniques known in the art such as machining, lost wax casting, pressing etc'.

The perimeter of the plate in each embodiment is circular however may be any shape e'g' oval, elliptical, triangular, square, pentagonal, hexagonal etc'. The diameter of the plate may be any size suited to the application. The perimeter might not be limited to a single plane i'e' it may be saddle shaped. The height of the protrusion may be any height. The height of the protrusion will depend on the application and expected modes of use. The skilled person will appreciate a larger protrusion will encourage greater convection flow within the water when heated and therefore will be more efficient. However the skilled person will also appreciate that the heated parts of the heat transfer plate must be covered by water whenever heating is taking place to avoid overheating. This must therefore be taken into account when only a small amount of water is heated.

The diameter of the heat transfer plates may be for example 5 (127mm). The protrusion may project to a height of 0.5 (12.7mm) above the flat part for example. For these dimension, a minimum volume of water of 5.6 floz (160ml) would be required to cover the heated parts of the heating component. This is less than the minimum typically needed i'e' one mug. The protrusion would therefore typically be covered with water in use.

An insulating material may be provided on an underside of the heat transfer plate. Alternatively insulating material may be provided on the underside of an otherwise conventional heat transfer plate.

Figures la to lc show a heat transfer plate 11 according to a first embodiment of the present invention. The upper surface of the heat transfer plate 11 has a flat part 12, bounded by a circular perimeter 13, and a conical protrusion 14. The upper surface appears uppermost in figure la and is the surface which is uppermost when in use. The conical protrusion 14 protrudes upwards from the flat part 12 and tapers upwards. The sides of the conical protrusion 14 are straight i'e' the sides appear straight in crosssection. The conical protrusion 14 is hollow i'e' the thickness of the heat transfer plate is substantially continuous over the flat part 12 and the conical protrusion 14. The conical protrusion 14 may be truncated, chamfered or filleted at the apex. The conical protrusion 14 has a circular base but may have a base of any shape. Alternatively there may be any number of protrusions distributed across the heat transfer plate.

Figures 2a to 2c show a heat transfer plate 21 according to a second embodiment of the present invention. The upper surface of the heat transfer plate 21 has a flat part 22, bounded by a circular perimeter 23, and a conical protrusion 24. The upper surface appears uppermost in figure 2a and is the surface which is uppermost when in use. The conical protrusion 24 protrudes upwards from the flat part 22 and tapers upwards. The sides of the conical protrusion 24 are curved i'e' the sides appear curved in cross-section and that curvature is concave. The conical protrusion 24 is hollow i'e' the thickness of the heat transfer plate is substantially continuous over the flat part 22 and conical protrusion 24. The conical protrusion 24 may be truncated, chamfered or filleted at the apex. The conical protrusion 24 has a circular base but may have a base of any shape e'g' oval, elliptical etc'.

Figures 3a to 3c show a heat transfer plate 31 according to a third embodiment of the present invention. The upper surface of the heat transfer plate 31 has a flat part 32, bounded by a circular perimeter 33, and a pyramidal protrusion 34. The upper surface appears uppermost in figure 3a and is the surface which is uppermost when in use. The pyramidal protrusion 34 protrudes upwards from the flat part 32 and tapers upwards. The sides of the pyramidal protrusion 34 are curved, i'e' the sides appear curved in cross-section and that curvature is concave, in the lower section 35 and flat in the upper section 36. The pyramidal protrusion 34 is hollow i'e' the thickness of the heat transfer plate is substantially continuous over the flat part 32 and pyramidal protrusion 34. The pyramidal protrusion 34 may be truncated, chamfered or filleted at the apex. The pyramidal protrusion 34 has a hexagonal base but may have a base of any shape i'e' triangular, square, pentagonal etc'.

Figures 4a to 4d show a heat transfer plate 41 according to a fourth embodiment of the present invention. The upper surface of the heat transfer plate 41 has a flat part 42, bounded by a circular perimeter 43, and a ridged protrusion 44. The upper surface appears uppermost in figure 4a and is the surface which is uppermost when in use. The ridged protrusion 44 projects upwards from the flat part 42 and tapers upwards. The ridged protrusion 44 is formed from flat surfaces in the form of two equal isosceles triangles 45 and two equal isosceles trapezia 46. Preferably each surface is angled 45 degrees from horizontal but may make any suitable angle. The long parallel edges of the isosceles trapezia 46 lie parallel to each other and together with the bases of the isosceles triangles 45 form the rectangular base of the protrusion 44. The short parallel edges of the isosceles trapezia 46 lie coincident with each other and form the ridge 47 of the protrusion 44. The apexes of the isosceles triangles 45 meet respective ends of the ridge 47. The ridged protrusion 44 is hollow i'e' the thickness of the heat transfer plate is substantially continuous over the flat part 42 and ridged protrusion 44. The ridged protrusion 44 may be truncated, chamfered or filleted at the ridge. The ridge 47 lies parallel to the flat part 42. The centerpoint of the ridge 47 lies above the center of the plate 41.

Figures 5a to 5c show a heat transfer plate 51 according to a fifth embodiment of the present invention. The upper surface of the heat transfer plate 51 has a flat part, 52 bounded by a circular perimeter 53, and a ridged protrusion 54. The upper surface appears uppermost in figure 5a and is the surface which is uppermost when in use. The ridged protrusion 54 projects upwards from the flat part 52. The ridged protrusion 54 is formed from three halves of the protrusion 44 seen in the fourth embodiment. Each half is arranged radially from the center of the plate 54 and are merged into a solid form.

The surface of the protrusion 54 is therefore formed from three isosceles triangles 55 and six rhomboids 56. The protrusion 54 therefore has three ridges 57 of equal length lying in a common plane, that plane being parallel to the flat part 52, and radiating from a point above the center of the plate 51. The ridged protrusion 54 is hollow i'e' the thickness of the heat transfer plate is substantially continuous over the flat part 52 and ridged protrusion 54. The ridged protrusion 54 may be truncated, chamfered or filleted at the ridge 57.

Figures 6a to 6c show a heat transfer plate 61 according to a sixth embodiment of the present invention. The upper surface of the heat transfer plate 61 has a flat part 62, bounded by a circular perimeter 63, and a ridged protrusion 64. The upper surface appears uppermost in figure 6a and is the surface which is uppermost when in use. The ridged protrusion 64 projects upwards from the flat part 62. The ridged protrusion 64 forms six ridges 67 which radiate from an apex 68 of the protrusion 64. The ridges 67 are radially equally spaced and are curved. The ridges 67 are inclined downwards from the central apex of the protrusion and meet the flat part 62 at their radially distal ends. The surfaces forming the ridges 67 are consequently curved and have a variable radius fillet with the flat part 62. The protrusion 64 therefore has the appearance of a starfish. The ridged protrusion 64 is hollow i'e' the thickness of the heat transfer plate is substantially continuous over the flat part 62 and ridged protrusion 64, but may be solid. If the ridged protrusion is hollow, heating elements may be moulded into the hollows. If the ridged protrusion is solid, flat heating elements of a suitable shape are attached to the undersurface of the plate.

Alternatively the ridges 67 may be truncated, chamfered or filleted. The ridges 67 may be straight or curved or a mixture of both. All the surfaces may be flat, curved or a mixture of both. The ridges may be the same or different lengths.

The curvature of the ridges in the sixth embodiment of the heat transfer plate cause a circumferential impulse to water being drawn by convection across the flat part 62 and towards the center of the protrusion 64. This combined with the upward flow caused by the water being heated results in a helical upward flow which aids mixing of hot and cold water. This further achieves even heating of the body of water. This principle may be applied to any embodiment.

Figures 7a to 7c show a heat transfer plate 71 according to a seventh embodiment of the present invention. The upper surface of the heat transfer plate 71 has a flat part 72, bounded by a circular perimeter 73, and three ridged protrusions 74. The upper surface appears uppermost in figure 7a and is the surface which is uppermost when in use. The ridged protrusions 74 project upwards from the flat part 72. The ridged protrusions 74 form ridges 77 which are arranged radially aligned to the center of the plate, but do not extend to the center of the plate such that three distinct and unconnected protrusions 74 are formed. The ridges 77 are radially equally spaced. The ridges 77 are parallel with the flat part 72. The surfaces forming the ridges 77 are flat near the apex of the ridge and have a concave curvature lower down to meet the flat part 72 tangentially. The ridged protrusions 74 are hollow, the hollows having the same or different shape to the upper surface of the protrusion 74, but may be solid. If the ridged protrusions are hollow, heating elements may be moulded into the hollows or flat heating elements may be attached to the inside surfaces of the protrusions. The flat parts of the surfaces forming the protrusions 74 may be made larger than the curved parts of the surfaces to ease attachment of the heating elements. If the ridged protrusions 77 are solid, flat heating elements of a suitable shape are attached to the undersurface of the plate beneath the protrusions.

Alternatively the ridged protrusions 74 may be truncated, chamfered or filleted at the ridge. The ridges may be straight or curved or a mixture of both. All the surfaces of the protrusions 74 may be flat, curved or a mixture of both. The ridges may be the same or different lengths. The ridges may not be aligned with the center of the plate or may not be parallel with the flat part 72. There may be any number of ridges.

Figures 8a to 8c show a heat transfer plate 81 according to an eighth embodiment of the present invention. The upper surface of the heat transfer plate 81 has an inner flat part 82a, an outer flat part 82b and a ridged protrusion 84 situated between them. The outer flat part 82b is bounded by a circular perimeter 83. The upper surface appears uppermost in figure 8a and is the surface which is uppermost when in use. The ridged protrusion 84 projects upwards from the flat parts 82a, 82b. The ridged protrusion 84 forms a single circular ridge 87. The ridge 87 is radially equidistant from the center of the plate. The radially inner surface 85a and radially outer surface 85b forming the ridge 87 have a concave curvature and curve to meet the inner and outer flat parts respectively tangentially, as can be seen from section H-H of figure 8c. The ridged protrusion 84 is hollow i'e' the thickness of the heat transfer plate is substantially continuous over the flat parts 82a, 82b and ridged protrusion 84, but may be solid. If the ridged protrusion is hollow, a heating element may be moulded into the hollows, or a heating element of a suitable form may be attached within. If the ridged protrusion is solid, a flat circular heating element is attached to the undersurface of the plate below the protrusion.

Figures 9a to 9c show a heating component 91 according to an alternate embodiment of the present invention. The heating component 91 is formed from conventional materials by conventional manufacturing techniques as known for conventional spiral shaped heating components. The main section 92 of the heating component adopts a taped helical form. The effect is to form a heating component with an overall conical form i'e' the heating component would fit into an imaginary cone. The shape could therefore be described as a conical helix. The ends of the heating component are shown extending into a base 94 but may equally extend into a sidewall connection as known in the majority of spiral heating component kettles. The helical form gives a large surface area for transferring heat to water. It concentrates heating at the center of the volume of water particularly due to the vertical section 93 connecting the base 94 to the top of the helix 92. The component 91 contains an integral electric heating element within.

When placed above the center of the base of a water heating apparatus, particularly one with steep curving walls coming into the base as shown in figure 16, the heating component 91 establishes strong convection flow in the body of water as the heating is concentrated below the center of the body of water. This causes a strong upward flow of hot water in the center of the body of water and permits cooler water to flow down in the periphery of the body of water and inwards across the base to the heating component 91 thus assisting in effective mixing and even heat distribution and consequently efficient heating. A narrow base combined with curved walls creates a small volume around the heating component 71 thus a small volume of water is required to cover the heating component. This satisfies the requirement for effective heating of a small volume of water without risking damage to the heating element.

Figures 10a to 10c show a heating assembly having a heat transfer plate 21 according to the second embodiment with a flat annular heating element 8 attached to the underside. Such heating elements are known. The heating element 8 is attached by means known in the art. Heat is conducted to the heat transfer plate. As the heat transfer plate 21 is formed from a thermally conductive material, heat is transferred through the plate to water in contact with the upper surface when in use. Heat will also spread out over the plate, depending on the material used and the thickness of the plate, and into the protrusion. Water in contact with the heated angled surfaces will rise and drive convection in the body of water.

Figures 11a to 11c show a heating assembly having a heat transfer plate 41 according to the fourth embodiment with two flat straight heating elements 9 attached to the underside of the protrusion. Such heating elements are known. The heating elements 9 are attached by means known in the art. Heat is conducted to the heat transfer plate 41.

As the heat transfer plate 41 is formed from a thermally conductive material, heat is transferred through the plate to water in contact with the upper surface when in use. Water in contact with the heated angled surfaces will rise and drive convection in the body of water. Two insulation sheets 10 are attached to the underside of the heat transfer plate 41. The insulation sheets are part-disk shaped but may be any shape, thickness or material suitable for the purpose of reducing heat loss from the lower surface of a heat transfer plate.

Figure 12 is a perspective view of a kettle 100 comprising a heating assembly shown in figures Ila to 11c. The kettle comprises a body 101 forming a water containing space 102. The kettle 100 stands on a base 104 and has a lid 105. In use, the base 104 is lowermost and the lid 105 is uppermost. The heating elements 9 and insulation sheets 10 of the heating assembly are not shown. As can be seen from the drawing, a heat transfer plate 41 is disposed at the bottom of the kettle. The heat transfer plate 41 forms part of the lower boundary of a water containing space 102. The remainder of the water containing space 102 is formed by the inner walls 103 of the body 102 of the kettle 100. A water tight seal is formed between the heat transfer plate 41 and inner walls 103 by conventional means. The inner walls 103 are curved such that the crosssectional area of the water containing space 102 as measured in the horizontal plane increases with height above the heating component, at least initially. In other words, the inner walls curve outwards with height above the base 104. Higher up, the walls then start to curve inwards towards the lid 105. The inner walls may follow a partly or substantially conical, spherical or ellipsoidal form.

In use, water is placed in the water containing space and heat is supplied to the water through the heat transfer plate 41. The shape of the heat transfer plate assists convection flow in the water and thus even heating of the water as discussed above.

The curvature of the inner walls 103 also assists convection flow. As hot water rises in the centre of the water volume, cooler water is drawn down from the sides of the water volume. The curvature of the inner walls directs this cooler water to flow across the surface of the heat transfer plate thus assisting even heating of the water volume. This flow helps prevent premature boiling and therefore reduces the steam lost during the heating process.

The remaining details of the kettle 100 such as other aspects of its shape, handle, lid, spout, material type, thickness and other components etc' are all conventional and those details represented in the drawings are representations by way of example only.

Alternately, the kettle 100 may be used with a conventional heating component.

Figure 13 is a section view of a kettle comprising a heat transfer plate according to the eighth embodiment.

Figure 14 shows a cross section view of a kettle as shown in figure 12. Arrows represent results from flow simulation. The results are derived from a flow simulation having a body of water contained within the kettle starting at room temperature. Heat is supplied via the heating elements and transferred through the heat transfer plate. Heat is then transferred to the water primarily through the angled surfaces of the protrusion of the heat transfer plate. As a normal gravity condition is applied to the simulation, the difference in water density caused by the heating causes a convection flow to form. The heated water therefore rises and cooler water is drawn in towards the heat transfer plate. The arrows indicate the direction of flow at various points within the body of water. The length of the arrows indicate the speed of flow at the various points. As can be seen in the figure, a strong upward flow is established above the protrusion resulting in a downward flow along the inner walls. A circulating motion is also seen in the periphery of the body of water, indicating strong mixing and therefore distribution of the heat around the body of water.

Figure 15 shows the temperature distribution, represented by shading, for the same results as described for figure 14. The protrusion of the heat transfer plate is very hot. The temperature of the heat transfer plate reduces gradually away from the center, indicating thermal conduction within the plate. The temperature of the plate drops off towards the edge indicating little thermal challenge to the integrity of the seal. The temperature of the water indicates a mushroom shaped hot plume from the protrusion. Warm water being drawn down near to the inner walls and circulating within the volume can also be seen. The results are captured half way through the heating process and at this stage, no significant variation in water temperature is seen. The desired effect is therefore achieved.

Figure 16 shows a kettle incorporating a conical, helical heating component as shown in figure 9. The inner walls of the kettle curve inwards towards the base of the heating component. The shape of the walls encourage convection within the body of water and reduce the volume of water required to cover the heating component.

In alternative variations of the preceding embodiments, there may be no flat part of the water contact surface of the heat transfer plate. The protrusion of the heat transfer plate may occupy the entirety of the water contact surface or part of the water contact surface may have another shape such as saddle shaped.

The apparatus may be used in heating liquids other than water. In which case the materials used will be materials suitable for use with those liquids for example materials which do not react when in contact with the liquid.

The invention may be used with apparatuses other than kettles. The invention may be used with other water heating apparatuses. Heat transfer plates of the invention may be incorporated into the base of saucepans. In such application, the protrusions would preferably not be hollow. The protrusions would be solid thereby forming a flat underside for heat to be applied to. A hollow protrusion may however be suitable for use on a gas hob. Such saucepans may be used for boiling vegetables, pasta, rice etc'.

Any feature or alternative feature of any embodiment may be used with any other embodiment.

Definitions relating to the present invention For the purposes of this invention, cone is understood to mean a geometric shape having a flat base and tapering to an apex. The base may be circular, forming a circular cone, elliptical, forming an elliptical cone, or polygonal, forming a pyramid. The polygonal base of a pyramid may have any number of sides greater than or equal to 3. The apex may be situated directly above the centre of the base i'e' a line from the center of the base to the apex makes a right angle to the plane of the base thus making a symmetrical cone. The apex may be situated offset from directly above the base making an oblique cone. The invention refers specifically to the surface or surfaces of such cones excluding the base.

A heating element generates heat when an electric current is passed through it. etc' is a contraction of et cetera e'g' is a contraction of exempli gratia i'e' is a contraction of id est

Claims (21)

Claims

1. A heating component, suitable for use in heating a liquid, wherein at least part of a surface of the heating component comes into contact with liquid when in use, and characterised by at least part of the contact surface being shaped to assist convection within the liquid when heated.

2. A heating component as claimed in claim 1 wherein the contact surface has a tapering aspect to at least part of its form.

3. A heating component as claimed in claim 2 wherein the tapering aspect is tapering in the vertical direction when in use.

4. A heating component as claimed in any preceding claim wherein the contact surface has a conical aspect to at least part of its form.

5. A heating component as claimed in any preceding claim wherein the component delivers heat to the liquid when in use through at least part of the contact surface.

6. A heating component as claimed in any preceding claim wherein the shape of the contact surface is substantially a conical helix.

7. A heating component as claimed in any preceding claim comprising a heat transfer plate wherein the contact surface is a surface of the heat transfer plate.

8. A heating component as claimed in any preceding claim wherein the contact surface comprises at least one protrusion which protrudes vertically upwards when in use.

9. A heating component as claimed in claim 8 wherein at least one protrusion forms one or more peaks or ridges.

10. A heating component as claimed in claim 8 or claim 9 wherein at least one protrusion is substantially conical.

11. A heating component as claimed in any of claims 8 to 10 wherein at least one protrusion forms a concave sided cone.

12. A heating component as claimed any of claims 8 to 11 wherein at least one protrusion is substantially pyramidal.

13. A heating component as claimed in claim 12 wherein at least one surface of at least one pyramid has concave curvature.

14. A heating component as claimed in claim 8 or claim 9 wherein at least one protrusion forms a plurality of ridges radiating from a central point.

15. A heating component as claimed in claim 9 or claim 14 wherein at least one ridge is straight.

16. A heating component as claimed in claim 9 or claim 14 wherein at least one ridge is curved.

17. A heating component as claimed in any of claims 8 to 16 wherein at least one protrusion is hollow.

18. A heating component as claimed in any preceding claim comprising an electric heating element.

19. A heating component as claimed in any of claims 1 to 4 wherein the contact surface is the inner wall of a liquid heating apparatus.

20. A heating component as claimed in claim 19 wherein the liquid heating apparatus 5 comprises a heating element disposed in a lower part of the apparatus and the inner wall is shaped such that the horizontal cross-sectional area of the space defined by the inner wall increases with height above the heating element.

21. A liquid heating apparatus comprising a heating component as claimed in any 10 preceding claim.