AU630769B2

AU630769B2 - Cooling control method

Info

Publication number: AU630769B2
Application number: AU67625/90A
Authority: AU
Inventors: Donald George Harding
Original assignee: Alltech Refrigeration Services (australia) Pty Ltd
Current assignee: Alltech Refrigeration Services (australia) Pty Ltd
Priority date: 1990-08-13
Filing date: 1990-11-30
Publication date: 1992-11-05
Anticipated expiration: 2010-11-30
Also published as: AU6762590A

Description

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3q.9O',4:HKS:HJB Form COMMONWEALTH OF AUSTRALIA Patents Act 1952 COMPLETE SPECIFICATION

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FOR OFFICE USE: Class Int. Class Application No Lodged Complete Application No Specification Lodged Published Priority: Related art: 4 1 4 6 $r 44(4 4p (404 O 40 4I 0 4 1 ((44 4 L 6- 4 TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: DONALD GEORGE HARDING -RangeRad-Seuth--Houghton, SState of Soeth-Austratia .mmonw-ealth of Australias Qe-4Z7 Hiahbon G'A- "-Dgg DONALD GEORGE HARDING Care of COLLISON CO., 117 King William Street, Adelaide, South Australia, 5000 Complete Specification for the invention entitled: COOLING CONTROL METHOD The following statement is a full description of this invention, including the best method of performing it known to me: L: I. i This invention relates to a cooling control method.

It is known, in order to cool some forms of produce, that this can be achieved by placing the produce within a closable chamber, closing the chamrnber and reducing the air pressure within the chamber, and causing a condensation of any water vapour drawn from the produce during the evacuation.

Conventionally, the condensation of water vapour is achieved by having heat exchange means within the chamber which are adapted to kept very cold so 1 0 that such water vapour as comes into the vicinity of such heat exchange means will be cooled sufficiently to condense.

A problem to which this invention is specifically directed relates to controlling the temperature of the heat exchange means.

01:5 O 0o 0 64% This may appear superficially to be a very easy task but in point of fact it is 00°' extremely complex for a number of important practical reasons.

a a 0oo The first of these is that the cooling needs for any application will conventionally vary significantly during the cooling process.

It is to be remembered that the predominant purpose of the heat exchange 0000 means is not to cool the produce as such but simply to remove the water .06 0 0 o vapour.

It will be relatively self-evident that if the cooling time is twenty minutes, the 9 o majority of the water vapour will come off in the first very few minutes and it will be a much lesser quantity of water vapour that will be removed during the latter So part of the cooling cycle.

0 0 Accordingly, the cooling and therefore condensing demand on any heat exchange means will change very quickly over a typical twenty minute cooling cycle and the difficulty is that if the cooling effect for an initial part of the cycle is kept for a latter part of the cycle, the heat exchange means which will usually be the evaporator of a refrigeration unit, will cause an icing up of the evaporator heat exchange coils.

li---r~--arn 3 The problem with icing up is that the ice then acts to insulate the heat exchange means from further oncoming water vapour so reducing the efficiency of the cooling process significantly, and furthermore, the ice once formed will take some time to melt away so that by the time a first load is removed and a second load relocated within the chamber for cooling, the evaporator coils are still iced up.

According to a first aspect of this invention therefore there are means to control the cooling effect of the heat exchange means in such an arrangement during 1 0 the cooling cycle.

By substantially matching the cooling effect through the cooling cycle, by not causing excessive cooling of the heat exchange means during the latter part of the cycle, reduces the chance that this will ice up and of course by careful 0°01.5 control will ensure that there is no effective icing up.

o 40l The difficulty now however is how do you achieve in a refrigeration unit over a O: cycle period which can be as small as a few minutes relatively close temperature control of the heat exchange means e.g. the evaporator unit within the chamber.

Conventionally a refrigeration unit comprises the main elements of a closed °o circuit fluid line comprising a compressor, a motor driving the compressor, the co+Q oO: compressor driving a refrigerant gas into a condenser, and there being a connection from the condenser through an expansion valve into the evaporative unit or units and thereafter a return of the refrigerant gas into the compressor.

o os 0 Cooling effect is generally directly related to the draw down pressure effected "3.O by the compressor so that a first technique might be self evidently to reduce the effectiveness of the compressor.

One technique that has been attempted is to control the drive speed of an electric motor driving compressor but the practical problems with this are firstly that in order to effect a substantial speed control of a motor of a size that is sufficient for the type of application that is being discussed, the cost becomes extremely substantial albeit a first solution.

i A second technique is to have a multiple system within the compressor such as perhaps three cylinders providing the compressing effect so that one can decouple one or two cylinders from a third thereby again reducing the effect but unfortunately only by a major proportion and not by an easily controlled smaller amount.

Despite quite extensive searching, there does not appear to be any effective pressure reduction valve system which can provide the control required, and there is also a difficulty in altering the pressure relationships within the closed 1 0 circuit pathway of the refrigerant, there might be caused flow of liquid refrigerant into the compressor which of course being substantially incompressible, can cause unreasonable pressure restraints within the apparatus.

1 5 The problem therefore has been to find an arrangement or a technique by which during relatively small time periods, very large refrigeration units can be controlled to provide either relatively negligible cooling effect or substantial cooling effect and all of this without the cost being unduly high or being unacceptable in terms of equipment characteristics.

According to one form of this invention there is provided a cooling apparatus including: a refrigerant; at least one internal refrigerant evaporator coil located within a cooling S 25 chamber; ~at least one external refrigerant evaporator coil located outside the o cooling chamber; at least one refrigerant condenser coil located outside the cooling 3 chamber; 30 a refrigerant circulating means communicating with the internal and external refrigerant evaporator coils and the refrigerant condenser coil or o. coils, the refrigerant circulating means being adapted to pump the refrigerant through the internal and external refrigerant evaporator coils and the ref.gerant condenser coil or coils; and a refrigerant flow control means adapted to effect increase or reduction .of communication between the refrigerant circulating means and the internal or external refrigerant evaporator coil or coils, wherein the refrigerant flow control means is adapted to limit ice forming upon the internal refrigerant evaporator coil or coils of condensed vapour within the cooling chamber.

In preference the cooling chamber is adapted to provide a low pressure cooling environment.

In preference the cooling apparatus includes a detection means for detecting the cooling effect of the internal refrigerant evaporator coil or coils within the cooling chamber, wherein the detection means is adapted to communicate with the refrigerant flow control means to limit ice forming upon the internal refrigerant evaporator coil or coils of condensed vapour within the cooling chamber.

In preference, the detection means is a pressure detector adapted to detect the pressure of the refrigerant, wherein the pressure of the refrigerant is related to the cooling effect and the pressure detector is positioned in close proximity to the internal refrigerant evaporator coil or coils such that it is adapted to detect the pressure of the refrigerant after the refrigerant has passed through the internal refrigerant evaporator coil or coils.

In preference, the external refrigerant evaporator coil or coils are located adjacent to the refrigerant condenser coil or coils, the external refrigerant evaporator coil or coils being in thermal communication with the external refrigerant condenser coil or coils.

In preference, the thermal communication is provided by fluid movement Someans adapted to draw a fluid across the external refrigerant condenser coil 0 or coils and then across the adjacent external refrigerant evaporator coil or coils.

In preference, the fluid is air and the fluid movement means is an eletric fan.

0 00 In a further preferred form the fluid is water or oil suitable to be used as a thermal carrier.

In another further prefenrred form the thermal communication is provided by a metallic material in physical contact with the external refrigerant evaporator coil or coils and the external refrigerant condenser coil or coils.

6 Alternatively, in another form of this invention there is provided a method for effecting a cooling within a cooling chamber including the steps of: effecting a flow of refrigerant about a closed refrigeration circuit, wherein the closed refrigeration circuit includes at least one internal refrigerant evaporator coil located within the cooling chamber and one external refrigerant evaporator coil located outside the cooling chamber; and controlling of the flow of refrigerant to increase or reduce the flow of refrigerant through the internal refrigerant evaporator coil or coils and external refrigerant evaporator coil or coils, wherein the controlling limits ice 1 0 forming upon the internal refrigerant evaporator coil or coils of condensed vapour within the cooling chamber.

In preference, the method is further charactertised by the step of reducing the pressure within the cooling chamber.

In preference, the method is further characterised by detecting the cooling effect of the evaporator coil or coils within the cooling chamber, wherein the detecting effects the controlling of the refrigerant.

In preference, the method is further characterised by the detecting being provided by measuring of the pressure of the refrigerant, wherein the pressure of the refrigerant is related to the cooling effect.

In preference, the method is further characterised by heat from a condenser io:°0 25 coil being used to heat the external refrigerant evaporator coil or coils.

o .o In preference, the method is further characterised by a fluid being passed over the condenser coil or coils and onto the external evaporator coil or coils.

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30 In preference, the method is further characterised by the fluid being air blown across the condenser coil or coils and onto the external evaporator coil or o 0coils.

a o 0 0 o'*p In order to better understand the invention it will now be described in relation to a preferred embodiment with the assistance of a drawing which is attached hereto and marked Figure 1 wherein an arrangement according to the S"invention is shown in schematic block outline.

7 Referring in detail to the drawing, the chamber schematically outlined in 1 includes a plurality of evaporative units 2 which are located within the chamber 1 so that when a vacuum is drawn within the chamber, air vapour will be condensed by reason of cooling effect over the evaporative coils 2.

The conventional condenser is shown at 3 which is external to the chamber so that compressor 4 driven by electric motor 5 will in the conventional way effect a compression of refrigerant forcing this as a vapour through conduit 6 into the 1 0 condensers 3 so that the refrigerant as a liquid is directed through conduit 7 into liquid storage receiver 8 from whence it is driven through drier 9 and then through solenoid controlled valve 10 and then finally through the respective Tx valves back into the evaporators 2.

1 5 In accord with this invention however there are a first pressure detector and a second pressure detector respectively 11 and 12 which detect the vapour pressure of the returning refrigerant and these are adjustable so that as the refrigerant varies from selected pressures, the pressure detectors are adapted to effect a control of variously means within the compressor 4 whereby this can be decoupled from three cylinders to one but the second of the detectors operates through a different pressure range so that upon the pressure reaching a further selected range, this will effect variously an opening or closing of the electrically operable solenoid valve 13. To reduce variations affecting the pressure detector by the pressure detected they are preferably 25 located in close proximity to the evaporative units 2.

0 oe° In this way, condensed refrigerant can be directed variously to either the coils or to the externally located evaporator coil 14 which is located in the 0 0adjacent vicinity to the condenser coils 3 and such that fan 15 can be caused to draw air through the expected to be heated condenser coils 3 thus causing and providing a heat source for offsetting the refrigerant effect and of course S00 ensuring that the refrigerant will be evaporated and maintain its evaporated 0 state after passing through the expansion valve Tx.

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8 It will of course now be understood the way in which the elements operate is that the setting of the pressure detection device will be such that during a first part of a cooling cycle a maximum of cooling effect will be directed to the cooling coils 2 so that check valve 10 is open and of course check valve 13 is closed.

As the temperature decreases however indicating that more of the water vapour in the chamber has been condensed, a period will be reached where 1 0 a first reduction in compression effect will be caused but thereafter it will get to the state that further reduction in cooling effect will be required at which stage check valve 13 will be opened thereby diverting a proportion of the refrigerant and of course this can be operated on a cyclic or time period basis so as to regulate the temperature within closely controlled limits of the evaporator coils 2.

If necessary, all of the refrigerant can be then diverted to the external evaporative coil but as will be seen by providing such a diversion this then allows for a very easily and indeed safely and also economic control of refrigerant effect for the purposes described.

In practice, the arrangement broadly as shown has proved to be of significant advantage in the application.

In accord with a previous invention, it is noted that it is important not to allow 5 condensed water vapour to be returned to an area of the chamber from whence it will be able to recover heat perhaps from conduction from an outside source and thereby revapourise into the chamber.

t S54 30 It will be appreciated that there are a number of variations to the configuration of the refrigerant circuit and the control circuit used to control the flow of the refrigerant. For example, the valve 13 and the solenoid valve 10 could be

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Ot 4swapped about. With this arrangement the valve 10, in this new arrangement, a. would be opened to a selected value and the solenoid valve 10 would be opened when cooling in the cooling chamber is required.

(I St,'/ 9 it will be appreciated that the means to detect the cooling effect of the evaporator coil or coils in effect acts as a temperature sensor means. Whilst in a preferred form a pressure sensor is used other types of temperature sensor means could be employed if desired.

It is understood that this present invention is a further advance in achieving economic cooling efficiency for the purposes described and can be operated in conjunction and indeed is cognative in effect in that one of the difficulties is to ensure that if the water has to be kept in storage separate from an external heat source, then it will often will be in the close vicinity of the coils so that this is further reason why the coils should be held at a controlled temperature so as to not cause icing of these.

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Claims

1. A cooling apparatus including: a refrigerant; at least one internal refrigerant evaporator coil located within a cooling chamber; at least one external refrigerant evaporator coil located outside the cooling chamber; at least one refrigerant condenser coil located outside the cooling chamber; a refrigerant circulating means communicating with the internal and external refrigerant evaporator coils and the refrigerant condenser coil or coils, the refrigerant circulating means being adapted to pump the refrigerant through the internal and external refrigerant evaporator coils and the refrigerant condenser coil or coils; and a refrigerant flow control means adapted to effect increase or reduction of communication between the refrigerant circulating means and the internal or external refrigerant evaporator coil or coils, wherein the refrigerant flow control means is adapted to limit ice forming upon the internal refrigerant evaporator coil or coils due to condensed vapour within the cooling chamber.

2. A cooling apparatus as in claim 1 in which the cooling chamber is adapted to provide a low pressure cooling environment.

3. A cooling apparatus as in any previous claim including: detection means for detecting the cooling effect of the internal refrigerant evaporator coil or coils within the cooling chamber, wherein the ,detection means is adapted to communicate with the refrigerant flow control means to limit ice forming upon the internal refrigerant evaporator coil or coils due to condensed vapour within the cooling chamber.

4. A cooling apparatus as in claim 3 in which the detection means is a 0 pressure detector adapted to detect the pressure of the refrigerant after it has passed through the internal refrigerant evaporation coil or coils, wherein the pressure of the refrigerant is related to the cooling effect and the pressure detector is positioned in close proximity to the internal refrigerant evaporation coil or coils such that it is adapted to detect the pressure of the refrigerant after 11 the refrigerant has passed through the internal refrigerant evaporator coil or coils.

A cooling apparatus, as in any previous claim, in which the external refrigerant evaporator coil or coils are located adjacent to the refrigerant condenser coil or coils, the external refrigerant evaporator coil or coils being in thermal communication with the external refrigerant condenser coil or coils.

6. A cooling apparatus as in claim 5, in which the thermal communication 1 0 is provided by fluid movement means adapted to draw a fluid across the external refrigerant condenser coil or coil, .Ind then across the adjacent external refrigerant evaporator coil or coils.

7. A cooling apparatus as in claim 6, in which the fluid is air and the fluid 1 5 movement means is an electric fan.

8. A cooling apparatus as in claim 6, in which the fluid is water or oil suitable to be used as a thermal carrier.

9. A cooling apparatus as in claim 6, in which the thermal communication is provided by a metallic material in physical contact with the external refrigerant evaporator coil or coils and the external refrigerant condenser coil no or coils. o me 25

10. A method for effecting a cooling within a cooling chamber including the steps of: effecting a flow of refrigerant about a closed refrigeration circuit, wherein the closed refrigeration circuit includes at least one internal refrigerant evaporator coil located within the cooling chamber, one external 3 0 refrigerant evaporator coil located outside the cooling chamber and at least one condenser coil located outside the cooling chamber; and controlling of the flow of refrigerant to increase or reduce the flow of refrigerant through the internal refrigerant evaporator coil or coils and external refrigerant evaporator coil or coils, wherein the controlling limits ice forming upon the internal refrigerant evaporator coil or coils due to condensed vapour within the cooling chamber. '1~ 12

11. A method of effecting a cooling within a cooling chamber as in claim including the step of: reducing the pressure within the cooling chamber.

12. A method for effecting a cooling within a cooling chamber as in claims or 11 including the step of detecting the cooling effect of the evaporator coil or coils within the cooling chamber, wherein the detecting effects the controlling of the refrigerant.

13. A method for effecting a cooling within a cooling chamber as in claim 12, wherein the detecting is provided by measuring the pressure of the refrigerant, wherein the pressure of the refrigerant is related to the cooling effect.

14. A method for effecting a cooling within a cooling chamber as inLclaims to 13, in which heat generated from the condenser coil is used to heat the external refrigerant evaporator coil or coils.

A method for effecting a cooling within a cooling chamber as in claim 14 in which a fluid is passed over the condenser coil or coils and onto the oo° external refrigerant evaporator coil or coils.

16. A method for effecting a cooling within a cooling chamber as in claim °"in which the fluid is air and this is blown across the condenser coil or coils and onto the external refrigerant evaporator coil or coils. i

17. A method for effecting a cooling within a cooling chamber substantially as described herein with reference to the accompanying Figure. (Ct 0

18. A Va.. cooling apparatus substantially as described herein with reference to the accompanying Figure. Dated this 3rd day of September 1992 DONALD GEORGE HARDING By his Patent Attorneys, COLLISON CO. r