WO1999018400A1

WO1999018400A1 - Device for producing ice

Info

Publication number: WO1999018400A1
Application number: PCT/NL1998/000552
Authority: WO
Inventors: Herman Johan Oonk; Johannes Martinus Ten Siethof; Willem Frederik Jense
Original assignee: Omega Engineering BV
Current assignee: Omega Engineering BV
Priority date: 1997-10-08
Filing date: 1998-09-23
Publication date: 1999-04-15
Anticipated expiration: 2000-04-08
Also published as: AU9190698A; NL1007221C2

Abstract

A device for producing a mass of ice in successive cycles comprises: a hollow panel (1) through which can flow a first heat transfer medium and which is placed in a position varying substantially from the horizontal position; means for causing water to flow over at least a part of the outer surface of the panel (1) such that due to through-flow of first heat transfer medium with a temperature below 0 °C at least a part of the liquid flowing along freezes and forms an ice crust (21) adhering to said outer surface; and heating means for heating said outer surface to above 0 °C such that the formed ice crust (21) becomes detached from the surface and slides or falls downward; and has the characteristic that the heating means comprise a heating element (20) which is placed in the cavity present in the panel (1) and which can be activated from outside.

Description

DEVICE FOR PRODUCING ICE

The invention relates to a device for producing a mass of ice in successive cycles, which device comprises: a hollow panel through which can flow a first heat transfer medium and which is placed in a position varying substantially from the horizontal position; means for causing a liquid, for instance water, an aqueous salt solution or a mixture of water with for instance alcohol, such as glycol, to flow over at least a part of the outer surface of the panel such that due to through-flow of first heat transfer medium with a temperature below freezing point or below or in the freezing range of the liquid, for instance 0°C for water, at least a part of the liquid flowing along freezes and forms an ice crust adhering to said outer surface; and heating means for heating said outer surface to above said temperature such that the formed ice crust becomes detached from the surface and slides or falls downward .

Such a device is known in diverse embodiments. The device usually comprises automatically operating control means which ensure that, after the formation of an ice crust for a certain time, the relevant outer surface is heated to above freezing point, whereby the ice crust loses its adhesion to that outer surface and slides or falls down under the influence of the force of gravity to be collected in a tray, on a conveyor belt or the like . The growth of the ice crust can for instance take place for 10 to 15 minutes, whereafter the subsequent heating lasts until the grown ice crust has fallen from the plate. This can take for instance 30 to 60 seconds .

A known device makes use of an injection of heated ammonia, for instance at a temperature of approximately 40°C, into the space enclosed by the panel. The drawback of this technique is that considerable pressure changes occur in the Oanel, for instance between 2.5 and 8 bar. This can, after many cycles, result in fatigue in the panel material. Such fatigue can cause hair cracks, leakage and rupture, while the temperature reached on the surface is moreover difficult to control. This latter will mean in practice that operation always takes place with an excess of supplied heat, which is undesirable for economic reasons .

The invention now has for its object to embody a device of the described type such that said pressure changes occur to a lesser degree and that furthermore the quantity of supplied heat can be properly controlled.

In respect of these objectives the device according to the invention has the feature that the heating means comprise a heating element which is placed in the cavity present in the panel and which can be activated from outside. During activation of the heating element the through-flow of first heat transfer medium will be temporarily interrupted.

It is noted that by using a freezing point-depress- ing agent in co-action with water a liquid is obtained of which the freezing temperature lies below 0°C. This may mean that the "cold content" per unit of volume of the ice formed on the basis thereof can be considerably larger than that of water ice. By optionally grinding or otherwise reducing in size this ice with very high density an ice can be obtained which can be pumped and has a very large cold content .

A specific embodiment has the feature that the first heat transfer medium in the cavity is partly in the liquid phase and partly in the gas or vapour phase and that the heating element is situated in the lower zone of the cavity.

The heating element can in principle be of any suitable type, for instance electric. A preferred embodiment has the special feature that the heating element comprises a heat exchanger through which can flow a heated second heat transfer medium.

Very simple but nevertheless effective is the em- ' bodiment in which the heat exchanger is a tube. In order to prevent the second heat transfer medium freezing in the environment at low temperature inside the panel, the device preferably has the feature that the second heat transfer medium is of a type which only freezes at a temperature which is lower than the lowest temperature of the first heat transfer medium.

An example of such a device has the feature that the second heat transfer medium contains a glycol . Use can for instance be made of an ethylene glycol which is diluted with water with a concentration of 20%. Such a mixture only freezes at about -10°C. At a panel temperature of roughly -8°C an ice crust is obtained with a temperature in the order of about -4°C. It is preferably ensured that the water flowing along has a temperature of just above 0°C.

In addition to glycol, thermal oil or steam for instance may also be considered suitable as second heat transfer medium. Steam can have the drawback that it may possibly result in freezing during the cooling period. A particular embodiment is characterized by control means for alternately

(a) causing the first heat transfer medium to flow; and

(b) activating the heating element. A high efficiency is obtained with an embodiment which is provided with cooling means for cooling the first heat transfer medium, which cooling means also serve to heat the second heat transfer medium.

An important embodiment of the device consists of an assembly of two devices provided with control means for alternately causing the first heat transfer medium to flow and activating the heating element respectively, while cooling means are present for cooling the first heat transfer medium, which cooling means also serve to heat the second heat transfer medium. The assembly of the two devices comprises one joint compressor and one joint condenser, wherein the control means are adapted to alternately cause flow of (a) cold heat transfer medium through the panel of the one device and hot heat transfer medium through the heat exchanger of the other device; and

(b) cold heat transfer medium through the panel of the other device and hot heat transfer medium through the heat exchanger of the one device .

This important embodiment makes very efficient use of available energy. In alternating manner the one device can serve to form ice while the other device is defrost- ed. The whole assembly makes use of only one heat transfer medium but is adapted such that by means of controllable valves, for instance under the control of a central control unit, respectively cold or hot heat transfer medium is carried through the relevant respective compo- nents . These components are respectively the hollow panel and the heat exchanger of the two devices which is arranged therein.

Any two-phase medium is suitable as first heat transfer medium, such that the panel can function as evaporator plate. As examples can be mentioned ammonia, a suitable Freon, propane, R22, R134A, R404A, etc.

The invention will now be elucidated with reference to the annexed drawings. In the drawings all the figures show a highly schematic partly broken-away perspective view of a device according to the invention.

Figures 1, 2, 3 and 4 show four successive phases of a cycle for producing ice; figure 5 shows an operational situation of the device in which water is cooled; figure 6 shows a view corresponding with figures 1-5 of an assembly of two devices; and figures 7, 8, 9 and 10 show schematic drawings of the device of figure 6 in successive operational situations during one full freezing/defrosting cycle. Figure 1 shows a hollow panel 1 through which can flow a first heat transfer medium. This panel forms part of a circuit designated with arrows 2 in which the first cooled and cooling heat transfer medium flows. It is pointed out here that the arrows 2 are not drawn in

device is still in exactly the same operational situation as in figure 1.

It is noted that tray 6 also has a drain 22. This serves on the one hand to empty the tray and can on the other hand also have the function of draining cooled water, as will be discussed with reference to figure 5. Figure 3 shows a subsequent phase of an ice-making cycle. In this phase the forming of the ice crusts is completed and the ice has to be released from the outer surfaces of panel 1. Energizing of pump 5 has meanwhile been discontinued, which is expressed in figure 3 by the absence of arrows 23 which designate the flow of water. Valves 13 and 16 are both closed and pump 18 is set into operation, whereby the second heat transfer medium, the flow of which is designated with arrows 24, is able to flow through heating tube 20 in the lower zone of hollow panel 1. From this lower zone a gradual warming in upward direction hereby takes place of the first heat transfer medium present in the hollow panel, whereby the walls are also subject to warming. The boundary layer with which ice crust 21 adheres to an outer surface of panel 1 will hereby melt, whereby the ice crust will be released and drop downward, as shown very schematically in figure 4 with arrows 25 and the inclining position of ice crusts 21. The ice crusts can be collected, reduced in size and for instance used for industrial cooling.

Particularly in the case in which the ice crust is formed on the basis of a mixture of water with freezing point-depressing agents, the obtained ice can have a very large cold content. By reducing in size or "crushing" the ice it can acquire a substance such that it can be pumped.

Figures 3 and 4 show the same operational situation of the device. It is noted that collecting means for collecting, optionally reducing in size and further transporting the ice are not drawn.

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hen a heat exchanger is used for the through-flow of heated second heat transfer medium, the heat exchanger can be equipped with provisions which enlarge the heat exchanging surface area, such as wires, ribs and the like.

The invention is not limited to the described embodiments. A hollow panel can for instance take a form varying from the flat form and have for instance a general tubular form. Such tubes or pipes can be grouped as a bundle.

No extreme demands are made of the heat conduction of the walls of the panel. The thermal conduction coefficient of steel, for instance stainless steel, is sufficiently high to ensure a good operation of the device according to the invention. Use of materials with even better heat conduction, such as copper, aluminium or the like, is not essential.

The invention also relates to a hollow panel with means for through-flow of a heat transfer medium. This panel is characterized according to the invention by a heating element which is placed in the cavity present in the panel and which can be activated from outside.

Figure 6 shows an assembly of two devices of the type shown in figures 1-5. For a proper understanding, components corresponding with components drawn in figures 1-5 are designated with the same reference numeral as therein, with the understanding that for the left-hand device these reference numerals have an "a" added, while for the right-hand device these reference numerals have a "b" added.

It is essential that compressor 10 and condenser 9 are shared by both devices. It is further noted that several embodiment features, such as water conduit 7, are not drawn in figures 6-10. The assembly comprises a number of controllable valves which can be placed in an open and closed position. In the case of the left-hand device these are suction valve 31, hot gas valve 32 and liquid valve 33; ^ in the right-hand device these are suction valve 34, hot gas valve 35 and liquid valve 36, in addition to the communal valve 37.

In figures 7, 8, 9 and 10 the conduits indicated with a single thick line are the conduits which are charged with through-flowing heat transfer medium. Flowing medium is indicated locally with arrows .

Figure 7 shows the situation in which hot heat transfer medium flows through heating tube or heat exchanger 20a, while cold heat transfer medium flows through panel lb. In this situation the valves 31, 33, 35 and 37 are closed, while valves 32, 34 and 36 are opened. It will be apparent that compressor 10 and condenser 9 in co-action provide through-flow of said heat transfer media. In the situation of figure 7 a defrosting of panel la takes place, while panel lb is subjected to a freezing process .

Figure 8 shows a situation in which valves 31, 32, 33 and 35 are closed, while valves 34, 36, 37 are opened. In this situation defrosting of panel la is complete and only freezing onto panel lb takes place.

In the situation according to figure 9 the operation of the left-hand device and that of the right-hand device is reversed relative to the situation of figure 7. It will be apparent without further explanation that cold medium flows through panel la to cause freezing of water flowing by, while hot heat transfer medium flows through heating tube 20b, whereby panel lb is defrosted. In this situation the valves 32, 34, 36, 37 are closed, while valves 31, 33 and 35 are opened.

Figure 10 shows a situation varying from that of figure 8. In this situation cold heat transfer medium flows through panel la so that freezing takes place. The right-hand device is wholly passive after heat transfer medium flows through heating tube 20b as according to figure 9. In this situation the valves 32, 34 and 35 and 36 are closed, while valves 31, 33 and 37 are open.

After the situation shown in figure 10, the system" returns to the situation shown in figure 7. The respec- tive figures 7, 8, 9 and 10 thus describe four successive stages of one operating cycle.

*****

Claims

1. Device for producing a mass of ice in successive cycles, which device comprises: a hollow panel through which can flow a first heat transfer medium and which is placed in a position varying substantially from the horizontal position,- means for causing a liquid, for instance water, an aqueous salt solution or a mixture of water with for instance alcohol, such as glycol, to flow over at least a part of the outer surface of the panel such that due to through-flow of first heat transfer medium with a temperature below freezing point or below or in the freezing range of the liquid, for instance 0°C for water, at least a part of the liquid flowing along freezes and forms an ice crust adhering to said outer surface; and heating means for heating said outer surface to above said temperature such that the formed ice crust becomes detached from the surface and slides or falls downward; characterized in that the heating means comprise a heating element which is placed in the cavity present in the panel and which can be activated from outside.

2. Device as claimed in claim 1, characterized in that the first heat transfer medium in the cavity is partly in the liquid phase and partly in the gas or vapour phase and that the heating element is situated in the lower zone of the cavity.

3. Device as claimed in claim 1, characterized in that the heating element comprises a heat exchanger through which can flow a heated second heat transfer medium.

4. Device as claimed in claim 3, characterized in that the heat exchanger is a tube.

5. Device as claimed in claim 3, characterized in ' that the second heat transfer medium is of a type which only freezes at a temperature which is lower than the lowest temperature of the first heat transfer medium.

6. Device as claimed in claim 5, characterized in that the second heat transfer medium contains a glycol.

7. Device as claimed in claim 5, characterized in that the second heat transfer medium is a gas, for instance steam.

8. Device as claimed in claim 7, characterized in that the gas comes from a cooling device which serves to cool the first heat transfer medium, for instance ammonia, propane gas, R22, R134A, R404A.

9. Device as claimed in claim 5, characterized in that the second heat transfer medium is a thermal oil.

10. Device as claimed in claim 1, characterized by control means for alternately

(a) causing the first heat transfer medium to flow; and

(b) activating the heating element.

11. Device as claimed in claim 3, characterized by cooling means for cooling the first heat transfer medium, which cooling means also serve to heat the second heat transfer medium.

12. Hollow panel with means for through-flow of a heat transfer medium, characterized by a heating element which is placed in the cavity present in the panel and which can be activated from outside.

13. Assembly of two devices as claimed in claims 10 and 11, with one joint compressor and one joint condenser, wherein the control means are adapted to alternately cause flow of

(a) cold heat transfer medium through the panel of the one device and hot heat transfer medium through the heat exchanger of the other device; and

(b) cold heat transfer medium through the panel of the other device and hot heat transfer medium through the heat exchanger of the one device.

14. Assembly as claimed in claim 13, as shown in the appended figure 6.

15. Assembly as claimed in claim 14, wherein the control means are adapted to perform successive operating cycles, each comprising four phases, which are shown in cyclic succession in the respective figures 7, 8, 9, 10, 7 , 8 , and so on.