WO1997034117A1

WO1997034117A1 - Device for making ice

Info

Publication number: WO1997034117A1
Application number: PCT/NL1997/000111
Authority: WO
Inventors: Herman Johan Oonk; Johannes Martinus Ten Siethof; Willem Frederik Jense
Original assignee: Omega Engineering B.V.
Priority date: 1996-03-05
Filing date: 1997-03-05
Publication date: 1997-09-18
Also published as: NL1002528C2; ZA971857B; AU2236697A; NL1002528A1

Abstract

A device for making 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 (3, 4, 5, 6, 7) 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 adhering to said outer surface; and heating means (8, 17, 18, 19, 20, 21, 118) for heating said outer surface to above 0 °C such that the formed ice crust becomes detached from the surface and slides or falls downward; and has the characteristic that the heating means (8, 17, 18, 19, 20, 21, 118) 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 making ice

The invention relates to a device for making 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 panel, 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- depressing 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 embodiment 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. 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 making ice; and figure 5 shows an operational situation of the device in which water is cooled.

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 figures 3 and 4 because the medium flow in question is not operating in these phases.

Panel 1 is placed in substantially vertical position and held in this position by positioning means

(not drawn) . Situated above panel 1 is a liquid conduit 3 with nozzles 4 from which can flow in this case water. This water is fed to conduit 3 by a pump 5 and comes in this embodiment from a collecting tray 6 which is connected to a water feed conduit 7. The circuit 2 comprises a heat exchanger 8 which co-acts with a condenser 9 placed at the outlet and a compressor 10 placed at the inlet. With this configuration an effective cooling of panel 1 can be effected in per se known manner. In the conduit 11, which connects the outlet 12 of panel 1 to compressor 10, is arranged a valve 13 which c n be moved between an opened and a closed position? A similar valve 16 is likewise placed in conduit 14 between the outlet of condenser 9 and the inlet 15 of panel 1. Connected to the heat exchanger 8 are a drain conduit 17 and a return conduit 18. The drain conduit 17 can guide heated medium via a selectively energizable pump 18 to the inlet 19 of a heating tube 20, which tube 20 is situated in the cavity of hollow panel 1 in the lower zone thereof. The outlet 21 of this tube 20 connects to the return conduit 18.

In the starting phase shown in figure 1, the panel 1 is cooled by the first heat transfer medium designated with arrows 2. The valves 13 and 16 are in their opened position. The tray 6 is kept filled at all times with a small quantity of water, optionally by replenishing via conduit 7. This water is pumped by pump 5 via conduit 3 to the nozzles 4. Water hereby flows over the outer surfaces of hollow panel 1. A part of the water will freeze due to extraction of heat by panel 1 and adhere to said outer surfaces. A remaining part of the water is collected by tray 6 and guided once again over the panel via conduit 3 and through the action of pump 5. A throttle valve 26 is arranged in the conduit 14.

Figure 2 shows the situation in which an ice crust is forming. In the phase according to figure 2 the device is still in exactly the same operational situation as in figure 1.

It is noted that the 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 the 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 wcϊter. 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 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.

The drawn form of the panel 1 is in principle completely random. The profiled structure has the advantage of an effective enlargement of the surface area, which serves for a good heat transfer. Other profiled structures can also be used for this purpose.

Figure 5 shows an operational situation in which the device is not used, at least not in essence, for preparation of ice but for the cooling of water. This operational situation corresponds by and large with that of figures 1 and 2 but, at variance with the ice-making operational situation, the water collected by tray 6 and cooled by panel l is drained via drain conduit 22. In this operational situation the supply conduit 27 can therefore preferably not debouch in tray 6 but connect directly to the infeed 27 of pump 5.

In order to enable the switch-over from the ice-making as according to figures 1-4 and the making of cooled water as according to figure 5, use can be made of a switching valve which as required causes the conduit 27 to debouch in tray 6 or connects it directly to the infeed 27 of pump 5. A valve which can be opened and closed can also be arranged in the drain 22. An important advantage of the structure according to the invention over the described prior art is that, owing to the fact that use is no longer made of injection of hot gas under pressure in the cavity of the panel, the panel walls can be thinner. Not only can the panel thereby be manufactured at lower cost, but the heat capacity of the panel is correspondingly smaller, whereby less energy is required to effect the required changes in temperature during respectively cooling and heating.

The said control means for alternately causing the first heat transfer medium to flow and activating a heating element can be adapted to interrupt the flow of a first heat transfer medium at the moment when the ice crust has reached a certain thickness. It can also be established on the basis of experience that the relevant thickness is reached approximately in a certain time. After exceeding of this time the flow of the first heat transfer medium can be interrupted and the heating element can be activated for a certain time which is for instance also empirically determined.

When 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.

Claims

l. Device for making 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.

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