AU701031B2 - Vacuum cooling foodstuffs - Google Patents

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 4 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

~REG

-o22610 L Name of Applicant: Donald George HARDING Actual Inventor: Donald George HARDING Address for Service: KEN-MADDERNL-PA InTENT-AT%RNEY-T C~o\1~or~ Co. 5th Floor,150GneISet Ki A i Adetiderou Au troli Adlade If~Ch j--jW 8 9 Invention Title: "Vacuum Cooling Foodstuffs" Details of Associated Provisional Application No: PM 4486 dated 15th March, 1994 The following statement is a full description of this invention, including the best method of performing it known to the applicant.

2 This invention relates to both means and method of vacuum cooling foodstuffs.

In my earlier Australian Patent No. 629715 (67713/90) there is described and claimed a device and method whereby foodstuffs such as vegetables can be vacuum cooled at relatively high speed. A much more effective cooling than otherwise known to the Applicant was achieved by utilising the subject matter of that patent and also Patent 630769 (67625190), and cooling equipment made in accordance with those patents has been used commercially and quite successfully. In the aforesaid Patent No. 629715, the condensate was held separate within a cooling chamber which was subjected to cooling by condensing the water vapour and maintaining the vapour in a receptacle when they were condensed, since if they were allow to access a source of heat by substantial thermal contact with the outside case, then such vapour 15 will increase because of increased vapour pressure of the water and this significantly reduces the ability of any vacuum pump to extract air and therefore get the pressure down within the chamber, It is conventionally :i understood that the cooling in these units provided by any evaporator in the chamber is tc condense water vapour.

As a result of the method used in that Patent, a small loss of about 2% of .0:6 weight could be expected for many vegetables, since the cooling effectively 00 took place by evaporation of moisture from the vegetables. In most cases, this 9: 9° *did not constitute a difficult problem, but in some instances very little cooling at all would take place (for example, apples or watermelons) while in other 9 99 25 cases, although cooling took place it did so at the expense of the appearance 0' of the produce, and for example carrots could have a "dried up" appearance of their skin. Notwithstanding these disabilities however, the method and means has been used very successfully in the preparation of vegetables for market.

J~e I 26-NOV-98 THU 16:17 COLLISON CO FAX NO. 61 8 82123988 P. O/ 3 One of the difficulties which has constituted a serious drawback of other vacuum cooling equipment known to the Applicant has been the formation of ice on the refrigeration evaporator coils, one function of which is intended to be to condense vapours and inhibit the passage of ice through a vacuum pump. Thus in the specification 630769, water vapour was drawn from the produce and the temperature of the heat exchange means was controlled in a way to avoid "icing up", wherein compressor size or speed was controlled, or use was made of temperature or pressure detector equipment secured adjacent the refrigerant coils to detect the pressure therein and to effect the abovementioned control, or providing an external refrigerant evaporator coil and using heat from the condenser coils to heat the auxiliary external evaporator coil. Since this latter process of and is a very important aspect of not just the earlier patents but also the invention the subject of this 15 application, it is Incorporated in this specification by way of reference.

.o An object of this invention is to provide improvement in both means and 0. method for cooling of foodstuffs or at the least provide the public with a useful alternative.

9 In one form of this invention, it can be said to reside in vacuum cooling means 20 for vacuum cooling foodstuffs, comprising a cooling chamber having a base sump; walls, and a door or doors defining the chamber, a vacuum pump connected to said chamber for reduction of air pressure within the charber, a refrigerator assembly comprising a motor driven compressor, an evaporator Scoil within the chamber and a condenser located externally of said chamber, 2 5 water distribution means within the chamber, a water circulating pump, and a I conduit extending from said pump to said water distribution means, arranged in a configuration whereby actuation of the pump effects circulation of water to discharge water over foodstuffs when in the chamber, but not discharge water on the evaporator coil and insulation means to keep any such water thermally 3 0 insulated from any external heat source.

It is important to keep the water being circulated thermally separated from any external source of heat, which source of heat can include heat resulting from an energy input such as the energy resulting from a rotor in the water circulating pump, causing the circulation pressures including some turbulence.

L~-p 4 IWhat has been discovered then is that in accord with the principle disclosed in my earlier Australian Patent 629715, that it is useful to have means to circulate water which can be used to douse foodstuffs with the water.

This has the additional advantage then that the water itself will act as a medium to transfer heat from direct contact with the foodstuffs or adjacent packages or the like.

If there is an external source of heat, water will produce significant amounts of 1 0 water vapour because of the low air pressure, and it is then very difficult to keep an adequately low pressure in the chamber. A rise in temperature from 0.6°C to 10C can be sufficient in one preferred example to significantly reduce the ability of a vacuum pump to keep a sufficiently low pressure in the chamber.

:1 5 In another form, the invention can be said to reside in a method of vacuum cooling foodstuffs by placing said foodstuffs in a vacuum chamber, actuating a vacuum pump to ieduce pressure in the vacuum chamber, circulating water :,within said vacuum chamber and discharging said water above said foodstuffs, and cooling air and water vapour in the chamber to condense water vapour in the air by passing refrigerant through a chamber evaporator of a refrigerator assembly, said chamber evaporator being located within said chamber, and keeping any said circulating water thermally insulated from any external source of heating, While the invention need not necessarily include the abovementioned details, an embodiment is described in some further detail with reference to and is illustrated in the accompanying sketches in which: Fig 1 is a perspective view showing a relatively small chamber carried on a trailer, with the chamber door open; Fig 2 is a diagrammatic cross-section which illustrates the water cooling of the load of foodstuffs carried in an open crate and positioned within the chamber; Fig 3 is a fragmentary section through an end of the door when open; and Fig 4 is a graph of temperature against time of fruit and circulating water RAL_ in one example of use of an embodiment of the invention;

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r 0r*44 r 4a In this embodiment, a cooling chamber 10 is carried on a trailer 11 so it can be moved from place to place as required, and comprises an outer wall 12 and inner wall 13 spaced therefrom, defining a cooling chamber 14, which is opened or closed by a sliding door 15 which can be moved across a loading mouth of the cooling chamber or opened as illustrated in Fig 1. The outer walls 12 are reinforced by reinforcing ribs 16 and the sliding door by reinforcing ribs 17, and the normally open mouth of the chamber 14 is closed by a removable panel 18 which forms portion of the inner wall 13. The panel 18 may be hinged, but as shown, is simply lifted out from its position shown when access is required to the interior of the cooling chamber 14. The function of panel 18 is to inhibit contact of cold water with outer surfaces, and use is also made of insulation material 19 so as to maintain thermal separation of water within the chamber from any heat source outside the 15 chamber 14. Such heat source as described in my earlier patent can simply be anything that can transmit heat and is at a higher temperature than the water. Accordingly, such thermal insulation relates to any member containing the water including external pipes and pumps, To keep heat input from the pump to a minimum it is arranged that the agitation from a pump rotor which will result in energy input being converted to heat, is kept as low as possible.

This means that the pump is operated as slow as possible with a minimum of water pressurisation.

As in both my earlier patents, there is provided a refrigerator assembly which comprises a compressor 21 coupled to a single condenser coil complex 22 which itself is located beneath fans 23. The refrigerant is condensed and expands through a first TX valve 24 into a main evaporating coil 25 within the top of the cooling chamber 14. A vacuum pump 26 is operable to maintain a very low pressure within the chamber 14.

In earlier prior art cooling chambers, refrigeration evaporator coils within cooling chambers have been limited in their effectiveness in condensing water vapour by "icing up", that is, being insulated by a covering of frozen water vapour. Since this invention utilises a water shower to provide water to be evaporated to thereby be cooled to thereby cool produce, and a vacuum pump to maintain very low pressure within a chamber, if, within the chamber,

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the gas is predominantly the ability of the evaporator coil to condense this water vapour, then the icing up problem reduces.

When water is placed in chamber 10, produce is placed in chamber 10, panel i 5 18 positioned, door 15 closed, and the refrigeration commenced, there is a heavy refrigeration load, and if the produce is required to be quickly chilled, a multi-horse power motor is usually requiied. There is a six cylinder compressor 21 with its cylinders divided into three pairs. Solenoid valves V1, V2 and V3 are all open, and all refrigerant passes through the first evaporator coil 25. However, as the temperature lowers, valve V3 is closed and this reduces the cooling. Meanwhile vacuum pump 26 is continuing to reduce pressure within the chamber, evaporating some of the water and thereby assisting in lowering temperature.

As reductions in temperature and pressure occur, icing up is likely to occur.

Valves VI and V4 open but valves V1 and V2 close in the final stage and some refrigerant is bypassed into auxiliary evaporator coil 29, but even this may not be sufficient to avoid icing up. It is partly for this reason that the coil 29 is located close to and above coil 22, so that heat emanating from :condenser coil 22 raises the refrigerant temperature. Although TX valves 31 and 32 are used, control of solenoid valves V1, V2, V3 and V4 is effected by refrigerant pressure. This provides a much closer temperature range within chamber 10, and temperature of water in chamber 10 (and therefore of at least outer surfaces of produce) can be maintained between 0' and 4 In some embodiments valve marked V1 can be dispensed with (since it would otherwise be continuously open).

The second (auxiliary) evaporator coil 29 is coupled to output of condenser coil 22 through TX valve 30. TX valves 24 and 30 are controlled by separate temperature sensors respectively designated 31 and 32, which sense the downstream temperatures of the evaporator coils, and can also be adjusted to provide the maximum cooling effect of the first evaporator coil 25 without ice formation. Locations of sensors 31 and 32 may be varied from those shown in Figure 2, However, the main control is by pr,-sure, as said above,

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6 The main advantage of this invention is achieved by enabling produce, which of itself cannot provide water to enable vacuum assisted evaporation of this to cool the produce, to be now cooled by adding water where however this is kept thermally insulated.

Fig. 2 shows a perforate container 36 (being a crate), and containing produce 37 (carrots being illustrated). Container 36 is supported by a grid base 38 located above a shallow V-shaped sump 39. Sump 39 contains water which is circulated by a pump 41 to a central header tube 42 from which a plurality of distribution tubes 43 extend, the tubes 43 having between them a large number of water outlets. The pump 41 operates continuously in use, and continuously douses the produce 37 with water which drains back into the sump 39. Vacuum pump 26 rapidly evaporates water 40 and thereby effects chilling it to the desired low temperature.

Although the carrots 37 have been previously washed, further washing is 4 effected by the passage of water over them, and if grit settles in the base of sump 39, it may be sluiced by opening drain valve 46.

:Fig 3 illustrates some constructional details to a larger scale, It shows an end oIof door 15 when open, the door 15 being supported by rollers 50 which run in 20 tracks 57 which are aligned, but their ends 52 (right hand as shown) bend towards the chamber 10 so that door 15 is drawn into contact with resilient seal 53. Once a low pressure is induced in chamber 10, atmospheric pressure on the outside of door 18 assists in forcing it onto seal 53.

The extraordinary efficiency achieved with this invention can be gauged from the following experiment which was conducted upon completion of the small machine illustrated: The following results are from a test subsequently conducted by the bepartmnent of Agriculture in South Australia, Australia.

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*5 4 A5 94 4 9 7 litres of water were introduced into the chamber, and a load of 150 kilograms of sugar plums loaded onto the platform. The interior panel (18) was placed into the chamber, the chamber closed, and the vacuum pump and refrigeration equipment energised.

Fruit temperature was 36.600, water temperature 12.700, and after 40 minutes both fruit and water temperatures were the same, namely 2.900.

The accompanying chart in Fig 4 plots the fruit and water temperature against time.

1 0 The electrical power expended was 6 kWHI from 4 horse power motor.

A check of the products indicated that there was no gain or loss of weight, so it was assumed that the products were not adversely affected by the rapid cooling.

In a second trial, 450 kg of carrots were loaded into chamber 10 and 80 litres 1 5 of water 40 placed in sump 39. The water temperature was lowered from 22.3"C to 400 in forty minutes. Development of water spray was avoided because of the extra energy input required (about one horse power).

Another interesting feature of the invention is that the closest art known, apart from that cited above, is the so-~called "hydrocool" process, wherein cold water 20 is allowed to dribble at slow speed over produce held at atmospheric pressure, and the time taken to cool 100 kg would be about I hour.

Furthermore, the cooling would be much less constant than with this process.

The above embodiment is not intended to be limited and, for example, use can be made of mechanical equivalents of r.2 the disclosed components. For example, a pump 26 could be replaced by a pump actuated ejector, the pump 34 could be any one of several types but it should be noted must be provided with seals which will not allow leakage under vacuum, the tubes 35 and 36 could be replaced by ushower roses" and the compressor 21 could be of any type, not necessarily of the type shown. However, these and other similar variations lie within the specification.

Claims (7)

1. Vacuum cooling means for vacuum cooling foodstuffs, comprising a coolin' chamber having a base sump; walls, and a door or doors defining the chamber, a vacuum pump connected to said chamber for reduction of air pressure within the chamber, a refrigerator assembly comprising a motor driven compressor, an evaporator coil within the chamber and a condenser located externally of said chamber; S0 water distribution means within the chamber, a water circulating pump, and a conduit extending from said pump to said water distribution means, arranged in a configuration whereby actuation of the pump effects circulation of water to discharge water over foodstuffs when in the chamber, but not discharge water onto the evaporator coil and insulation means to keep 15 any such water thermally insulated from any external heat source. .99. .9c99*

2. Vacuum cooling means according to claim 1 wherein said water distribution means comprises a header tube and a plurality of distribution tubes, each distribution tube having a plurality of downwardly directed water outlets, said h!ader tube joining each distribution tube to said conduit, such 20 that foodstuffs are doused with streams of water discharging through said water outlets.

3. Vacuum cooling means according to either claim 1 or claim 2 further comprising an auxiliary evaporator coil located externally of chamber, and above and close to said condenser at a location where it will be heated by waste heat from the condenser.

4. Vacuum cooling means according to claim 3 wherein said refrigerator assembly further comprises a pressure actuated solenoid valv. in a refrigerant line joining said auxiliary evaporator coil to said compressor, arranged to open upon-drop in pressure within said r'efrigerant line to thereby place said auxiliary evaporator into circuit. 1- I L I fr 9 Vacuum cooling means according to claim 3 wherein said compressor comprises at least three separate compression segments, each having a separate refrigerant line joining it to said chamber evaporator, at least two pressure actuated solenoid valves in circuit of respective said refrigerant lines,' said pressure actuated solenoid valves being sequentially closed upon drop in pressure within said refrigerant line to thereby place respective said compressor segments out of circuit.

6. Vacuum cooling means according to claim 5 comprising a further 1. 0 pressure actuated solenoid valve joining said chamber evaporator and auxiliary evaporator when opened upon further drop in pressure after said sequential closure of said at least two solenoid valves.

7. A method of vacuum cooling foodstuffs by placing said foodstuffs in a vacuum chamber, actuating a vacuum pump to reduce pressure in the vacuum chamber, circulating water within said vacuum chamber and discharging said water above said foodstuffs to douse said foodstuffs with streams of downwardly flowing water, and cooling air and water vapour in the chamber to condense water vapour by passing refrigerant through a chamber evaporator of a refrigerator assembly, said chamber evaporator being located within said chamber, and keeping any said circulating water thermally insulated from any external source of heating.

8. A method of vacuum cooling foodstuffs accord,.; to claim 7 further comprising sensing refrigerant pressure after its said passage through the u chamber evaporator, and reducing output of a compressor which forms part of 25 said refrigerator assembly, upon reduction of said refrigerant pressure. d U SI• 9. A method of vacuum cooling foodstuffs according to claim 8 further comprising effecting said reduction of compressor output by closing a solenoid valve in the refrigerant circuit of said refrigerator assembly upon said reduction of refrigerant pressure and thereby isolate a segment of said l: 30 compressor. C C'i C ,L 4 C~ ABSTRACT Produce is chilled without dehydration by circulating water through a chamber (10) in a dispersed form to evenly pass the water through the produce contained in the chamber (10) while maintaining a very low pressure and cooling the water both by evaporation and also by an evaporator (25) of a refrigerator (21) contained within the chamber while at the same time preventing formation of ice by heating refrigerant in a second evaporator (29) external of the chamber (10) by waste heat from the refrigerator condenser (22). o .000 C C C I