WO2001055653A1 - Method and apparatus for producing an ice-water mixture - Google Patents

Abstract

A method and apparatus for producing an ice-water mixture, wherein water is supplied along an upper edge, extending in the longitudinal direction of the tubular chamber, of a guiding member with a downwardly inclining surface, such that it runs down the surface of the guiding member in a thin, film-like layer. By adjusting the interior of the housing to a suitable reduced pressure, a part of the water is evaporated, which evaporated water freezes on a cold surface placed in the chamber. Through the evaporation, heat is abstracted from the non-evaporated water, so that this is converted to an ice-water mixture which is discharged from the chamber.

Description

Title: Method and apparatus for producing an ice-water mixture

The invention relates to a method for producing an ice -water mixture by supplying water to a tubular chamber in which a pressure prevails which is so low that water is evaporated, which evaporated water freezes on a cold surface placed in the chamber, while through the evaporation heat is abstracted from the non-evaporated water, so that this is converted into an ice-water mixture, which is discharged from the chamber.

Such a method is known from US-A-4,845,954, wherein use is made of chambers with a water bath, from which the ice-water mixture is discharged via an overflow. On the one hand, this means that the residence time of the water in a chamber is not defined, while the ice formed, floating on the surface of the water, can lead to disturbance of a uniform discharge of the ice-water mixture. Ice can accumulate at the overflow and therefore be pushed over the edge in irregular quantities, which, upon instantaneous release of larger quantities of ice, can lead to clogging of the drain. A further problem is that water preferably boils near solid surfaces, because there, the formation of vapor bubbles takes less energy. This means that most of the ice will be formed near the wall of the housing, which can lead to undesired ice adherence to the wall of the housing. Additionally, ice formed near the wall will have to float on the water surface in the direction of the centrally located drain, which reduces the free water surface and hence the evaporation necessary for the ice formation.

With the invention, a method is contemplated in which the above-discussed problems do not occur.

According to the invention, this is achieved in a method of the type described in the preamble, when the water is supplied along an upper edge, extending in the longitudinal direction of the tubular chamber, of a guiding member having a downwardly inclining surface, such, that it runs downward over the surface of this guiding member in a thin, film-like layer. Through these features, a relatively large film-like wetted surface is obtained, which has a correspondingly high evaporation capacity, i.e. the ratio between the evaporating surface and the water volume present is maximal. Additionally, the residence time in the housing can be set accurately and the spread in residence time is minimal. Also, the guiding member can be disposed within the housing such that it can remain substantially out of contact with the wall of the housing, so that thermal insulation of the housing is not necessary.

The ice-water mixture produced can be used for cooling purposes, and, due to the non-toxic character of water, is particularly suitable as cold carrier in the food and luxury food industry. To that end, it should be possible to produce the ice-water mixture on a large scale and in an economically sound manner, which possibility is offered by the present method proposed by the invention. A possible field of application is on board of ships, which, however, by rolling and pitching as a result of movement of waves, can have an adverse influence on the production process. For instance, in a water bath in a housing, the water and the ice present therein may slosh, which leads to vehement and uncontrolled boiling phenomena. In this respect, the method according to the present invention has an additional advantage. Due to the relatively small mass of the water flowing film-like over the guiding member, this will hardly, if at all, be subject to the above-mentioned effect resulting from movements of a ship. Further, the gradient of the guiding member disposed in the housing is such, or can be chosen such, that the downward flow of the water along the guiding member proceeds continuously in all customary positions of a ship, i.e. deviations up to approximately 15° from the horizontal. For discharge, the ice-water mixture formed can be caught at the lower end and collected in a gutter extending in the longitudinal direction of the housing, connected to a drain. However, this entails that mixture ending up in the gutter very near to the drain has a shorter residence time than mixture ending up in the gutter at a distance from the drain. The gutter also needs to have a certain gradient, which, especially on board of ships, has to be considerable if a correct and continuous discharge is to be ensured at all times. According to a further embodiment of the invention, it is therefore preferred that the water running down along the guiding member and the ice-water mixture thereby formed, is gradually separated, in a lower area of the guiding member, into a number of partial streams, each of which is discharged from the chamber via its own discharge opening. Thus, the inclining guiding member is used in an advantageous manner to bring the ice-water mixture formed to the housing drain, so that a continuous discharge is ensured at all times and differences in residence time are minimized. According to a further embodiment of the invention, it is additionally preferred that the separately discharged partial streams are collected in an inclined discharge pipe and are discharged therefrom via a pump which, by means of a pressure difference measurement, can keep the level in the discharge pipe substantially constant. Thus, the draining conditions from the housing are regulated such that the process conditions in the housing remain constant as much is possible without regulation of the supply. Controlling the process conditions by influencing the water supply to the housing would be less easy because the flow of the film of water over the guiding member would change. An additional disadvantage thereof is a dead time in the control circuit, which makes it more difficult to maintain a constant water level.

The invention also relates to an apparatus for producing an ice-water mixture. According to the invention, such an apparatus is provided with a tubular housing in which a guiding member is disposed with an upper edge extending in the longitudinal direction of the tubular housing and a downward inclining surface, over which guiding member a cooling body is arranged, the tubular housing being provided with means for generating therein a reduced pressure, and supply means for water and discharge means for ice-water mixture, the supply means comprising a distribution unit extending along the upper edge of the guiding member. Thus, in an efficient manner, a film of water running down the guiding member can be created, from which, due to the reduced pressure, water evaporates which freezes on the cooling body. As is known, the housing will further be provided with additional provisions, for instance for periodically defrosting and discharging the water vapor precipitated on the cooling body in the form of ice, and, if so desired, means for discharging non-condensable gases from the housing.

In order to maintain the desired discharge of the ice -water mixture under all conditions, and thus to keep the process conditions equal, it is preferred, according to a further embodiment of the invention, that the guiding member comprises a lower area, provided with at least one outflow section with converging edges and connected to discharge means in the form of a drain pipe. It will then be preferred, determined typically by the desired dimensions of the apparatus for producing ice-water mixture on a large scale, that the guiding member comprises several outflow sections each connected to a drain pipe, the pipes ending up in a collecting pipe which is arranged at a gradient. In this manner, as it were, a modularly designed apparatus is obtained, having the extra advantage that it can be enlarged in a relatively simple manner, as desired.

In order to reduce the chance of adherence of ice as much as possible, it can be provided, according to a further embodiment of the invention, that the parts susceptible to adherence of ice, such as the drain pipes and the guiding member, are covered with an anti-adhesion coating.

When, according to a further embodiment of the invention, in the collecting pipe, a pump is included, which is connected to a control unit which can be controlled by pressure measuring means with which the level of the ice-water mixture in the discharge pipe can be determined, the process conditions can be regulated, and more specifically, kept constant in an effective manner, the film of water over the guiding member being influenced as little as possible, i.e. the water supply being interfered with as little as possible. It has already been noted that with a modular structure, the capacity of the apparatus can be relatively easily adapted as required. A relatively simple enlargement of the capacity is also possible by disposing two guiding members in the housing in a mirror symmetrical manner, while, from a constructional point of view it can be preferred that the outflow sections of the two guiding members are mirror symmetrical and that in each case, two mirror symmetrically disposed outflow sections connect to one drain pipe.

With reference to exemplary embodiments schematically represented in the drawing, the method and apparatus for producing an ice-water mixture according to the invention will, though exclusively by way of example, be further elucidated. In the drawing:

Fig. 1 shows the apparatus in side view; Fig. 2 shows the guiding member in front view; Fig. 3 shows the guiding member in side view; and Fig. 4 shows an apparatus with two mirror symmetrically disposed guiding members.

The apparatus represented in Figs. 1 - 3 is provided with a housing 1, in which by means not shown a reduced pressure can be created and in which a cooling body 2 is disposed above a guiding member 3, which, as is schematically represented in Fig. 3, is disposed at an inclination in the housing 1. Along the upper side of the guiding member 3 extends a supply conduit for water, which, via a number of stubs 4a, can feed a distribution unit 5. The distribution unit 5 is provided with a delivery slot 5a, which provides for the supply of a uniform water film, which can flow downwards along the guiding member 3. To that end, the guiding member 3 is provided with a flat, plate shaped part 3a with plate side edges 3b. To the plate-shaped part 3a connect four outflow sections 3c, having a downwardly converging shape and side edges 3d which gradually increase in height and are bent towards each other, so that the lower extremities of the side edges have a continuous circular configuration and can therefore smoothly connect to a drain pipe 6, which is composed of two knees 6a, 6b, and a contiguous, vertically extending stub 6c, ending in a discharge pipe 7. Beyond the last stub 6c, in the discharge pipe 7, a pump 8 is included, which is operated by a control unit 9, which receives its control signals from pressure measuring means, such as a pressure sensor 10.

For producing, with such an apparatus, an ice-water mixture, which is, for instance, suitable as cold-carrier for cooling products and processes at a temperature level of -15° to 0°C, the following steps can be taken.

Before supplying water via the supply pipe 4, the interior of the housing 1 is adjusted to a reduced pressure of 6 mbars. At that pressure and a temperature of approximately 0°C, the so-called triple point of water is reached, i.e. under those conditions the water can be solid, liquid or vaporous. Water at 0°C brought from the supply pipe 4 via the stubs 4a into the distribution unit 5 leaves this distribution unit 5 through the delivery slot 5a, which enables the water to run downwards as a relatively thin film over the guiding member 3. Due to the conditions prevailing in the housing 1, a part of the water flowing down will evaporate. This evaporating water precipitates on the cooling body 2 and freezes there. The heat abstracted through evaporation from the water flowing down along the guiding member 3 causes the formation of ice in the non-evaporated part of the water and thus the formation of the ice-water mixture. This treatment of the water is extremely effective in view of the maximum ratio between evaporating surface and the volume of the water led in the form of a film over that surface.

In order to discharge the ice-water mixture thus formed in a manner which is as smooth and uniform as possible, the flat, plate shaped part 3a of the guiding member 3 merges into four outflow sections 3c, converging triangularly downwards, which, gradually, in cooperation with the side edges 3d, merge from a flat surface into a tubular passage, and hence smoothly change the initially flat film of water into ice-water jets which enter the drain pipes 6 and onto which, through the knees 6a and 6b, the desired flowing conditions are imposed. Via the stubs 6c, the ice-water mixture ends up in the discharge pipe 7, while the pump 8, being controlled by the control unit 9 and the pressure sensors 10, keeps the ice-water mixture at a certain level, so that, without adjusting the water supply via the supply pipe 4, the process conditions can be kept constant.

Through the pump 8, the ice-water mixture can be transported to a storage tank (not shown) from which ice-water mixture for cooling purposes can be drawn as desired. Then, it can be returned to the storage tank from which water can be drawn again to be subsequently fed to an apparatus for producing the ice- water mixture.

It is noted that in Figs. 1 - 3, although they are present, no supply and discharge conduits for the cooling body 2 are depicted. The same goes for further provisions, such as means for periodically defrosting the cooling body 2 to strip it of adherent ice and discharging water thereby formed. In Fig. 4, in a very schematic manner, a variant of an apparatus for producing an ice-water mixture is represented, with which variant the capacity of the apparatus can be increased without having to proportionally increase the dimensions of the apparatus. To that end, in a housing 11, under a cooling body 12, two guiding members 13 are mirror symmetrically arranged. The guiding members 13 are provided with mirror symmetrically disposed discharge sections 13c which collectively connect to one single drain pipe 16, which, in turn, ends in a discharge pipe (not shown). Thus, in comparison to the embodiment according to Figs. 1 - 3, the evaporating surface can be considerably enlarged without modifying the overall dimensions of the housing.

It is self-evident that within the scope of the invention as set forth in the following claims, many changes and variants are possible. A guiding member, for instance, could continue in an uninterrupted manner, i.e. without outflow sections, into a collecting gutter under the housing, from where the ice-water mixture formed can be discharged.

Claims

Claims

1. A method for producing an ice-water mixture by supplying water to a tubular chamber in which the pressure prevailing is so low that water is evaporated, which evaporated water freezes on a cold surface disposed in the chamber, while through the evaporation heat is abstracted from the non-evaporated water, so that this is converted into an ice-water mixture, which is discharged from the chamber, characterized in that the water is supplied along an upper edge, extending in the longitudinal direction of the tubular chamber, of a guiding member with a downward inclining surface, such that the water runs down over the surface of the guiding member in a thin, film-like layer.

2. A method according to claim 1, characterized in that the water running down the guiding member and ice-water mixture thereby formed is gradually separated in a lower area of the guiding member into a number of partial streams, which are each discharged from the chamber via their own discharge opening.

3. A method according to claim 2, characterized in that the separately discharged partial streams are collected in a discharge pipe disposed at an inclination and are discharged therefrom via a pump which, by means of a pressure difference measurement, can keep the level in the discharge pipe substantially constant.

4. An apparatus for producing an ice-water mixture and provided with a tubular housing in which a guiding member is disposed having an upper edge extending in the longitudinal direction of the tubular chamber and a downwardly inclining surface, above which guiding member a cooling body is disposed, the tubular housing being provided with means for generating a reduced pressure therein as well as supply means for water and discharge means for an ice-water mixture, the supply means comprising a distribution unit extending along the upper edge of the guiding member.

5. An apparatus according to claim 4, characterized in that the guiding member comprises a lower area, provided with at least one outflow section. with converging edges and connected to discharge means in the form of a drain pipe.

6. An apparatus according to claim 5, characterized in that the guiding member comprises several outflow sections each connecting to a drain pipe, the pipes terminating in a collecting pipe disposed at a gradient.

7. An apparatus according to claim 6, characterized in that in the collecting pipe a pump is included, connected to a control unit controllable through pressure measuring means with which the level of the ice-water mixture in the discharge pipe can be determined.

8. An apparatus according to any one of claims 4 - 7, characterized in that in the housing, two guiding members are disposed mirror symmetrically.

9. An apparatus according to claim 8, characterized in that the outflow sections of the two guiding members are mirror symmetrical and in each case two mirror symmetrically disposed outflow sections connect to one drain pipe.

10. An apparatus according to any one of claims 4 - 9, characterized in that the parts susceptible to adhesion of ice, such as the drain pipes and the guiding member, are covered with an anti-adhesion coating.