AU726011B2

AU726011B2 - Cooling method and apparatus

Info

Publication number: AU726011B2
Application number: AU57372/98A
Authority: AU
Inventors: Donald George Harding
Original assignee: Alltech Refrigeration Services (australia) Pty Ltd
Current assignee: Alltech Refrigeration Services (australia) Pty Ltd
Priority date: 1997-03-06
Filing date: 1998-03-06
Publication date: 2000-10-26
Anticipated expiration: 2018-03-06
Also published as: AU5737298A

Description

46967 HKS P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

go Name of Applicant: DONALD GEORGE HARDING Actual Inventor: DONALD GEORGE HARDING Address for Service: COLLISON CO.,117 King William Street, Adelaide, S.A. 5000 Invention Title: COOLING METHOD AND APPARATUS Details of Associated Provisional Applications: Australian Patent Application No. P05496 dated 6th March 1997 The following statement is a full description of this invention, including the best method of performing it known to me:

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2 This invention relates to a means and method for cooling materials and it has particular application to rapid cooling of hot food.

It is however not intended in its broadest sense to be limited to food and it may apply to other materials that may contain moisture and need to be cooled after heating.

One problem associated with the rapid cooling of hot food is well known.

Traditionally, for bulk cooking for commercial purposes or otherwise, hot food, once cooked, for long term avoidance of deterioration, should be cooled to a preservation temperature as quickly as possible.

However, this is somewhat difficult in terms of current techniques.

For instance, if a batch of hot food for instance mashed potatoes is taken and placed within a very cold environment, it can take some hours while heat is dissipated from the material especially from deeper within the mass of the material to a surrounding colder atmosphere.

15 Such a period which can be some hours, both takes up storage space in valuable .cool areas, requires costly substantial cooling mechanisms and in any event results in some deterioration due to either partial spoilage due to bacteria or otherwise during a longer cooling period.

So An excellent solution would be achieved if a process known as vacuum cooling ll could be used for cooling but hitherto, attempts to use such a system for cooling :I have not been successful.

This current invention results from earlier unsuccessful trials.

I have discovered that previous attempts which have included attempting to apply a reduced atmospheric pressure together with condensation of given off vapour, has resulted in such an amount of vapour that the vapour gets to be drawn into any vacuum pump and at least with the types of pumps that I have had available, result in the vacuum pump not being able to cope and no effective cooling would $%7,appear to take place over a reasonable period of time.

r n of ~'V7 O. 4i 2a My discovery in accord with this invention is that by using a relatively simple change in method, cooling of hot materials such as hot foods can be efficiently and economically effected by using substantially the same equipment.

c* e 9 9 4 er 0 e e a reoe re oee It has been hitherto conventional to place the materials to be cooled in a chamber, close the chamber and then commence both a vacuum pump and a refrigeration evaporator within the chamber in order to condense liquid vapours.

In practice, there are control means started by a single activation signal which start at the same time as both the vacuum pump and the refrigeration.

According to this invention, I have found that if the refrigeration is started to have a cooling means to condense water vapour within the chamber effectively cold for a sufficient time before the hot material is placed in the 1 0 chamber or the vacuum pump is commenced, then it is possible to effectively and efficiently cool hot materials such as hot food using this technique.

In practice, I have found that if the refrigeration is commenced and is operating .:for approximately 30 seconds before the hot food is introduced into the chamber and the chamber closed so that the vacuum pump then operates, this is quite sufficient with installations currently being used in order to allow the system to handle the effects of hot food.

The reference to hot food is qualified to the extent that the food will carry accessible moisture where the evaporation of the moisture can be effected to achieve the cooling effect.

20 For other materials which are hot but do not carry moisture, it can be possible to introduce moisture in a way which will be later discussed.

According to one form of this invention then there is proposed a method of effecting evaporative cooling of material where the material is hot to start with where there is a chamber into which the material can be placed for cooling by evaporative cooling, a cooling arrangement including a cooling means within the chamber adapted to condense water vapour within the chamber, and means to withdraw gaseous fluid from the chamber to effect a partial reduction in air pressure within the chamber the method including steps of effecting a cooling of the cooling means within the chamber prior to locating hot materials 3 0 in the chamber and before commencement of withdrawing of gaseous fluid.

In preference, the commencement of cooling of the refrigerant evaporator is such that the refrigerant evaporator will be cold prior to the introduction of the hot material into the chamber.

In preference, the hot material is material carrying with it moisture and arranged so that the moisture is accessible to the atmosphere when placed within the chamber.

In preference the time prior to the hot material being introduced into the chamber, by which the refrigerant evaporator is commenced operating is at least approximately 30 seconds.

1 0 In preference, the material placed within the chamber is food of a type which incorporates moisture therein and the temperature is substantially above ambient temperature. Obviously this can vary and of course it will vary through the mass of any food that might be provided. For instance, if mashed potatoes have been cooked, the mass of potatoes will be hotter within the body of the potatoes as compared to the outer surface.

In practice, it has been found preferable to extend the mashed potato into layers of perhaps 5 10 centimetres in thickness and have these exposed to the reducing atmosphere within the chamber.

So One of the features of this cooling system is that most of the air is removed from the chamber so that a fairly high degree of vacuum is achieved within the chamber to effect the efficient cooling.

A further discovery has then been made that if the food items are placed in the chamber for cooling within closable packages, then if instead of releasing atmosphere back into the chamber after the cooling has been effected, a gas other than air is allowed to replace the vacuum, then the packages will be effectively refilled with such replacement gas. If this gas is an inert gas or an appropriate mixture of say nitrogen or carbon dioxide or any other combination of gasses, then if the packages are closed after such gas is introduced, then the effect is that such inert gas or preservation gas is 3 0 captured within the container or pack providing for substantial keeping effect.

One further feature that has been discovered relates to the situation where material placed within the chamber does not of itself have moisture which can be used to effect the evaporative cooling or if the moisture of the material itself is not used, then the material can be graded in both quality or appearance or otherwise.

In accord with a further feature of this invention then, there is proposed that there be water within the chamber and that there be means to provide inundation of the materials during the cooling process.

Several specific problems however have to be addressed.

1 0 The first of these is that if the water to be used for inundation within the chamber, connects through heat transfer means to an outside source of higher temperature, then the efficiency of the cooling effect will be significantly reduced.

Accordingly, in a preferred arrangement, the chamber is arranged so that its walls are kept thermally separated from outside the chamber that is to ambient temperatures and any water used for inundation of products to be cooled is recirculated within the chamber and handled in such a way that at all times there is substantial thermal insulation or separation from any external to the chamber heat source.

S2 0 This is especially applicable if the product to be cooled is heated in the first instance so that inundation will result in immediate evaporation of large quantities of moisture which again causes the problem that was previously discussed and requires preliminary cooling of the condensing means in the chamber.

In preference the water should be arranged so that any inundation will not pass onto a cooling condenser.

In a preferred arrangement then where the cooling means are a refrigerant evaporator as a unit is located at an uppermost place within the chamber, and means to distribute water for inundation below this water are all provided immediately below the refrigerant evaporator.

It is understood throughout that the inventive concepts and improvements can all be used in conjunction with my earlier developed technology as has been set out for instance in Australian Patent No. 629715 (67713/90) and also in relation to Australian Patent No. 630769 (67625/90).

The invention may be better understood when described with respect to a preferred embodiment and as such an example will be described it being emphasised that it is not intended that the invention should be necessarily limited any of the specific details described with respect to the preferred embodiment.

In the preferred embodiment, there is provided a chamber having a refrigerant evaporator located adjacent a roof of the chamber, and means to seal a chamber with respect to a vacuum within the chamber and also means to effect a withdrawal of gasses within the chamber to effect a high level of vacuum. In addition, there are provided means to effect a sealing of containers 15 holding food which has been cooled within the chamber and finally there is a S:source of inert gas which can be released to fill the chamber.

In accord with this invention, it is arranged that as a first step, a refrigerator system in accord with my previous descriptions in my previous referred to 2 patents in Australia, are operated for a sufficient period of time to ensure that the refrigerant evaporator has been substantially chilled. Such a temperature would be just above 00 Centigrade and in the preferred embodiment, this would be held at approximately 20 Centigrade.

Subsequent to bringing the refrigerant evaporator within the chamber to the Centigrade, hot food, in this case mashed potato that has just been cooked, is placed within the chamber and such that it is laid in layers which are approximately 4 cm in thickness and each batch is within its own sterile bag the top of which is left open to atmosphere and in this case to the effect of the withdrawing of a vacuum and effecting evaporation of moisture within the chamber.

3 0 Upon the hot food and in this case hot would mean temperatures of approximately 850 Centigrade in the centre of the mass of the material, is placed in the chamber, the doors are closed and immediately air and vapour is pumped from within the chamber.

The vacuum is continued to be pulled until the internal pressure is approximately 5 mm of mercury.

This has the effect of causing evaporation of moisture from the mashed potatoes both from the surface and from within the mass and as the water vapour is released, this is caused to be condensed by the refrigerant evaporator being at such a cold temperature, and the condensed water vapour is then retained below the refrigerant evaporator so that this will not be communicating with substantial thermal conducting means to outside the chamber.

1 0 As the previously hot food reaches a selected minimum temperature and in this case the target temperature is 40 Centigrade in the mass of the material, then the vacuum pump is stopped and a supply of inert gas being nitrogen and 30% carbon dioxide is released into the chamber so as to refill *.the chamber back up to atmosphere which at the same time will fill the 1 5 otherwise open areas within the bags containing the previously hot food.

Within the chamber and therefore maintained with the inert atmosphere, are closure means such as heat sealing closure device and mechanical means are used to bring each bag mouth into the closure jaws to effect a sealing ~while being maintained in the inert atmosphere.

The result of the process is to very significantly improve the cooling speed with which hot foods can be then cooled and by proceeding through the further processes of inundating the opened bags in which the food is cooled, with inert and sterile gasses, and then closing the bags in airtight manner, provides a very significant improvement in food handling processes.

In the event that the hot food does not of itself contain moisture or the amount of moisture is restricted so that if this was evaporated, the food quality would be reduced, then it is possible in this invention to provide a further feature which is to say that water can be introduced onto the food items in such a way as to provide a cooling effect this being achieved by firstly ensuring that any 3 0 water introduced into the chamber is kept within the chamber and such that while it is being used to effect cooling, it is kept separated from a source of heat externally from the chamber.

8 This implicitly means that the water should be recirculated while being maintained within the chamber and that the distribution of the water can be so that the water will not directly impinge upon the refrigerant evaporator.

Such features can be achieved by fully insulating the chamber either by having an external insulating skin or any other means of maintaining effective insulation can be used.

Claims

1. A method of effecting evaporative cooling of material where the material is hot to start with where there is a chamber into which the material can be placed for cooling by evaporative cooling, a cooling arrangement including a cooling means within the chamber adapted to condense water vapour within the chamber, and means to withdraw gaseous fluid from the chamber to effect a partial reduction in air pressure within the chamber the method including steps of effecting a cooling of the cooling means within the chamber prior to locating hot materials in the chamber and before commencement of withdrawing of gaseous fluid.

2. A method of effecting evaporative cooling of material where the material is hot to start with as in preceding claim 1 further characterised in that the cooling means within the chamber are cooled for approximately 30 seconds before the hot material is introduced into the chamber. A method of effecting evaporative cooling of material where the material 15 is hot to start with as in either of the preceding claims further characterised in that the reference hot material is a reference to hot food which carries accessible moisture whereby the evaporation of the moisture can be effected to achieve an evaporative cooling effect.

4. A method of effecting evaporative cooling of material where the material is hot to start with as in any one of the preceding claims where the cooling means is a refrigerant evaporator to provide for the cooling effect. S i

5. A method in effecting cooling of material where the material is hot to start with as with any one of the preceding claims the method being further characterised in that the hot material is mashed potato.

6. A method of effecting evaporative cooling of material where the material is hot to start with as in any one of the preceding claims further characterised in that a gas other than air is allowed to replace the partially evacuated area within the chamber so that packages holding the cooled materials will be effectively refilled with such replacement gas and where such gas is selected to provide a substantial keeping effect.

7. A method of effecting evaporative cooling of material where the material is hot to start with as in the immediately preceding claim further characterised in that the gas is an inert gas being a mixture of nitrogen or carbon dioxide.

8. A method in effecting cooling of material where the material is hot to start with as in any one of the preceding claims the method being characterised in that there is water within the chamber and that there are means to provide inundation of the materials during the cooling process.

9. A cooling apparatus for use in the method of any one of claims 1 to 8 including a chamber into which hot material can be placed for cooling by evaporative cooling, a cooling arrangement including a cooling means within the chamber adapted to condense water vapour within the chamber, and means to withdraw gaseous fluid from the chamber to effect a partial reduction in air pressure within the chamber, the chamber arranged so that its walls are kept thermally separated from outside the chamber ambient temperatures and arranged so that any water used for inundation of products to be cooled is recirculated within the chamber and in such a way that at all times there is substantial thermal insulation or separation of such water from any external heat source. A cooling apparatus as in the preceding claim further characterised in that the water is arranged so that any inundation will not pass onto or through the cooling means. S11. A cooling apparatus for use in the method of any one of claims 1 to 8 for cooling hot materials characterised in that it includes a chamber having a refrigerant evaporator located adjacent a roof of the chamber, and means to seal the chamber with respect to a partial evacuation of gaseous fluid from within the chamber and S• 25 also means to effect a withdrawal of gasses within the chamber to effect a high level of vacuum, means to'effect a sealing of containers holding food which has been cooled within the chamber and a source of inert gas which can be released to fill the chamber.

12. A cooling apparatus substantially as described in the specification.

13. A method of cooling hot to start with materials substantially as described in the specification. Dated this 23rd day of August 2000 DONALD GEORGE HARDING By his Patent Attorneys, COLLISON CO. 9. 9. 9!9 .9 .9 9 9 9 9.. 9 9 9 9 9 9 *99~ 9 *9.9 9. 9 9 .9 i 9.9. *9 99 9 9 9 999 9 99 9 99 9.