WO1992017101A1

WO1992017101A1 - Heat transfer apparatus and method

Info

Publication number: WO1992017101A1
Application number: PCT/GB1992/000609
Authority: WO
Inventors: Brian William Garn
Original assignee: Brian William Garn
Priority date: 1991-04-04
Filing date: 1992-04-06
Publication date: 1992-10-15
Also published as: GB9107042D0; GB2254532B; EP0583255A1; AU1532192A; GB2254532A; GB9207444D0

Abstract

Heat transfer apparatus comprises nested plastic buckets (12, 14) defining an annular heat transfer zone in which liquid (48) heated by a tubular electric heater (16) entering through the wall (20) of the outer bucket (12) a zone between the two bottom walls (22, 42) of the buckets, effects heating of liquids contained within the inner bucket (14), either directly therein, or in containers placed therein. The abutting interaction of the buckets (12, 14) defines a protected zone for the heater (16) in which it cannot be damaged by impact with articles to be heated.

Description

HEAT TRANSFER APPARATUS AND METHOD

This invention relates to heat transfer apparatus and a corresponding method.

The invention is particularly but not exclusively applicable to the heat treatment or temperature-maintenance of liquids, or setable liquids such as honey, for use in the home brewing and bee keeping fields. The invention also finds application to heat treatment or temperature-maintenance of many other articles and products, but the invention will be described by reference to these two particular applications, by way of example.

In the case of home brewing, there is a well-known need for maintaining the brewing liquor at a suitable temperature for the maintenance of the fermenting action. Likewise, in the case of bee keeping, there is a need for heat treatment of honey with a view to effecting modification of the physical characteristics of the honey after crystallisation or a related change has occurred. This can be effected by maintaining the honey at a fairly well defined temperature for a significant period of time.

Previous proposals in relation to these temperature- maintenance or heat-transfer requirements have included the use of electrical heating bands which are wrapped around containers for the brewing liquor, and electrical heaters which are actually plunged into the brewing liquor, and in the case of honey heating, containers have been proposed in which heaters such as electric light bulbs effect heat transfer to the honey through air within the container.

None of the prior proposals is particularly satisfactory. The direct heating bands are somewhat ineffective and slow, and temperature maintenance is somewhat inaccurate. Moreover, the heating effect is not as gentle as could be desired, and this latter factor is particularly so in the case of heaters which are directly plunged into the liquid. In the case of the heat treatment of honey, the prior apparatus is thermally unstable and very slow in operation.

I have identified a significant need for an improved method and apparatus for heat transfer wherein simple and relatively inexpensive apparatus is able to effect heat transfer in an easily controlled manner, and an object of the present invention is to provide improvements in this regard, or generally.

According to the invention there is provided heat transfer apparatus, and a corresponding method of heat treating, as defined in the accompanying claims.

In a preferred embodiment of the invention there is provided heat transfer apparatus comprising, in the assembled condition thereof, an assembly of two plastic buckets which are nested, one within the other. In their nested condition, the buckets define, between their facing surfaces, an annular chamber within which a heat exchange fluid can be contained. Heating means is provided within the chamber defined between the two nested buckets. The heating means is mounted on a side wall of the outer of the two buckets.

Abutment means is provided which acts between the two nested buckets, to limit the inward movement of the upper of the two buckets, thereby to define the annular chamber between the two, this chamber including a non-annular portion defined between the base of one bucket and the base of the other, and into which portion the heater extends. The heater is of generally elongated form and extends through a mounting opening formed in the side wall of the outer bucket, in fluid- tight sealing engagement therewith, and into the above- mentioned non-annular space between the buckets.

The abutment device acting between the two nested buckets may, for example, be provided by the handle assembly of the inner bucket which abuts structure (such as a closure lid) provided on the outer bucket. In this way, the handle assembly defines a limit to the inward movement of the inner bucket, thereby defining the space between the bases of the two buckets, and thus protecting the heating element between them.

In the preferred embodiment, the outer of the two buckets is provided with a lid member formed with a central opening to slidingly receive the inner bucket, and the lid member being itself in sealing engagement with the outer bucket, in the normal manner for a lid, whereby the lid member acts to connect the two buckets and effectively to seal-off the annular space therebetween (which annular space is, in use, filled with heat exchange fluid) , whereby, for example, loss of fluid from a heated heat exchange fluid is minimised, and likewise loss of heat. The lid member is formed, as indeed the plastic buckets are, as a plastics moulding, for example in polypropylene or polyethylene or another suitable polymer. The central opening to receive the inner bucket may be formed by a cutting operation, or may be pre-moulded therein.

By roviding the main structural components of the heat exchange apparatus in the form of moulded plastic buckets, very significant cost and availability advantages are provided. The use of such apparatus for heat exchange purposes is unconventional since heat exchange vessels are conventionally metallic or of glassware, or other conventionally heat resistant materials. By adopting a nested configuration of two readily available moulded plastic containers, it has been possible to define an annular heat exchange chamber in which a .heat exchange fluid provides effective heat transfer between the two vessels. The location of the heating element in the non-annular chamber between the bases of the two vessels provides for the heater a protected location in which the heat generated can have a maximum effect by means of convection currents generated in the heat exchange fluid and flowing from the non-annular portion into the annular portion, and thus to the wall of the inner vessel.

By adopting the use of a heating element mounted in a wall of the outer bucket, a convenient and safe location is thereby provided for this otherwise vulnerable and relatively high cost component of the heat exchange system. It has been discovered that the mounting of such a heater directly in the wall .of a plastic bucket can be accepted, from the point of view of heat resistance purposes. The mounting of the heating element may be through a fluid and heat-sealing collar. This collar may be of a resilient material.

In use, the preferred embodiment may be arranged so that in the nested condition of the two buckets, the volume of heat transfer fluid provided in the outer of the two buckets results, upon insertion of the inner one thereof, in a depth of fluid in the annular chamber causing a maximum of heat transfer between the buckets. Visible marking means may be provided on or in the outer bucket to define the depth of liquid to be provided therein before insertion of the inner bucket, in order to produce the necessary depth of fluid in the annular chamber upon assembly.

Also in the preferred embodiment, the heating element incorporates thermosta ic control means whereby the temperature of the heat transfer fluid in the chamber between the two buckets is selectively controlled. Suitable markers are provided to prevent the use of a temperature higher than 80 degrees celsius for polyethylene buckets, and 95 degrees Celsius for polypropylene buckets.

In an embodiment in which the heat transfer apparatus is to effect a controlled temperature maintenance operation with respect to brewing liquor in a home-brew beer-brewing operation, the inner bucket of the heat transfer apparatus provides a brewing vessel to contain the brewing liquor, and heat transfer to it maintains the brewing liquor at the desired temperature.

In another embodiment, the heat transfer from the heater between the two buckets is effected not only by conduction through the walls of the inner bucket, but also by convection through the apertures in a screen opening provided in the bottom of the inner bucket, the heat exchange fluid thus entering the inner bucket, and effecting heat transfer by direct contact with articles located therein. For example. such an article may be a glass fermenting vessel, as used in home wine making, or jars of honey may for example be heat treated in this manner to effect controlled changes in the physical form of the honey.

In a further embodiment, again in which the base of the inner bucket is provided with a screen, in use the arrangement is such that the heat transfer liquid does not rise through the screen, and heat is transferred to a material initially placed on top of the screen in the inner bucket. For example, in the case of re-processing frying fat, solid fat may be thus placed in the inner bucket, melted by heat from the heat transfer liquid, and the melted fat passes through the screen and into that liquid, which is constituted by water. The fat is thereby cleaned or scrubbed by the water, and separates as a molten layer thereon which can be separated from the water by means of a tap provided in the wall of the outer bucket at a suitable height therein, thereby enabling separation of processed and purified fat.

One important aspect of the preferred embodiment relates to the provision of support means to support an article to be heated within the fluid. The support means abuts the outer bucket and defines a space within it, within which the heating means is located during use. In the preferred embodiment, the support means is provided by the inner bucket, which nests inside the outer bucket, and is supported on the latter through the modified lid assembly of the latter. The inner bucket provides, at its base, support means for individual containers to be heated. Alternatively, a liquid to be heated can be simply poured into the inner bucket. In a modification, alternative support means could be provided which, instead of deriving support from the upper region of the outer bucket, could rest directly on the base of the outer bucket, while still defining a zone within which the heater is located and protected. For example, ^' this latter support means might be in the form of a metallic stand having legs through which the heating element extends. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which :-

Fig 1 shows a vertical section through a first embodiment of the invention; and

Fig 2 shows a similar section through a second embodiment.

As shown in Fig 1, heat transfer apparatus 10 comprises an outer chamber 12 in the form of a plastics bucket, an inner chamber 14, likewise in the form of a plastics bucket, and heating means 16 in the form of a tubular heater mounted in an aperture 18 in the downwardly tapering side wall 20 of bucket 12, near the base wall 22 thereof. A support member 24 clips on to the tubular glass body 26 of heating means 16 and acts between the latter and base wall 22, to support the heater. The heater comprises a coiled heating element 28 and^: a thermostatic control system 30 having an external temperature setting knob 32. A rubber gasket 34 seals heating means 16 to the wall 20 of outer bucket 12.

Inner bucket 14 is connected to outer bucket 12 through the plastics material lid 36 of the latter. This lid clips to an annular flange 38 on the outer bucket. The flat main body portion of the lid 36 has its central portion removed to receive inner bucket 14, and the latter is welded or bonded thereto or merely oldged thereon at 40 so as to provide a secure mounting for the inner bucket at the height shown in Fig 1 with the indicated gap or space between the bucket bottom walls 22 and 42, within which heating means 16 is located, and is likewise protected.

Inner bucket 14 has a lid 44 which seals to a flange 46 in a manner similar to that of the outer bucket.

In use, the volume of liquid 48 within outer bucket 12 is chosen so that when the inner bucket 14 is fitted therein, the level rises to the position indicated in Fig 1.

Heater means 16 is powered through supply cable 50 and raises the temperature of the liquid 48. Heat is transferred to the liquid (for example brewing liquor) 52 within inner bucket 14 by heat transfer in the annular zone between the nested buckets, and likewise through the base wall 42 of inner bucket 14. Thermostat 30 maintains the temperature at the selected level for whatever period of time is required. As indicated at 54, probe thermometers show the maintenance of a common temperature in both bodies of liquid, and this temperature stability can be readily maintained for any desired length of time.

In the embodiment of Fig 2, the apparatus is otherwise as described above, but the base wall 60 of the inner bucket is largely constituted by a circular area 62 of gauze through which the heat transfer liquid 64 can readily pass, and thus adopts a common level 66 in both buckets. Heat transfer is effected by direct movement of liquid under the influence of convection currents through the gauze and hence to the demijohn of brewing liquor 68 supported within the inner bucket 70.

Interestingly, the above embodiments provide simple and inexpensive and conveniently-used apparatus for effec ing heat transfer. The apparatus is easy to use, reliable and effective.

An example of a potentially important application of the invention in the temperature maintenance field relates to the incubation of reptile or other eggs. For example, the embodiment of Fig 1 above could be used as an incubator by providing within bucket 14 a suitable quantity of a medium to surround the egg or eggs, for example a partiσulate material such as sand or vermiculite, or a mixture thereof. The eggs would be buried in this material within the inner bucket and the required incubation temperature would be very readily maintained by means of thermostat 30.

Amongst other modifications which could be made in the above embodiments are the use in place of inner bucket 14 of support means adapted to be carried directly from the inner surface of outer bucket 12, for example a stand of metal or plastics material which could be located on the base 22 of the outer bucket, thereby to provide a support, for example, for demijohn 68 while nevertheless protecting heater 16.

Claims

1 Heat transfer apparatus comprising : a) chamber to contain a heat transfer fluid; and b) heating means locatable within said chamber to heat said fluid so as to transfer heat to an article, through said fluid; characterised by c) said chamber being a bucket of a plastics material; d) said heating means being mountable in the region of the bottom of said bucket; e) support means being provided to support an article to be heated within said fluid in said bucket; and f) said support means abutting said bucket and defining with the bottom wall of said bucket a space within which said heating means is located in use, and in which space heating of said fluid is effected, and within which space said heating means is protected from contact with an article to be heated.

2 Heat transfer apparatus comprising a bucket of a plastics material, heating means mountable therein, and support means for an article to be heated, said support means defining a space within which said heating means is located in use.

3 Apparatus according to claim 1 or claim 2 characterised by said heating means extending through an opening in the wall of said bucket.

4 Apparatus according to claim 3 characterised by a support member for said heating means to act between said heating means and the bottom wall of said bucket.

5 Apparatus according to any one of the preceding claims characterised by said support means being in the form of an inner bucket which nests inside said outer bucket and defines 1° therewith an annular heat transfer chamber.

6 Apparatus according to claim 5 characterised by said inner bucket being connected to said outer bucket at the upper edge of said outer bucket and through a modified lid of said outer bucket, with said inner bucket extending through a central opening formed in said lid.

7 Apparatus according to claim 6 characterised by handle means on said inner bucket being arranged to abut said lid.

8 Apparatus according to any one of claims 5 to 7 characterised by said inner bucket having one or more apertures therein permitting said fluid to enter the inner bucket from the outer bucket to effect heat transfer direct.

9 Apparatus according to claim 8 characterised by said apertures being provided by an area of gauze provided in the base of said inner bucket.

10 Heat transfer apparatus substantially as describedherein with reference to the accompanying drawings.

11 A method of heat treating a liquid such as honey or a beverage com.pris.ing standing one or more containers of said liquid in apparatus according to any one of the preceding claims and raising the temperature of the liquid in said container by effecting heat transfer thereto.

12 A method of brewing fermented beverages comprising standing one or more containers of said beverages in apparatus according to any one of claims 1 to 10 and raising or maintaining the temperature of said beverage by use of said heating means.

13 A method according to claim 11 or claim 12 characterised by said container which is stood in said apparatus being provided by said inner bucket of the apparatus.

14 A method of incubating eggs comprising maintaining said eggs at an incubation temperature in apparatus according to any one of claims l to 10.