US 3456452 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
July 22, 1969 G. s. HlLBERT 3,456,452
METHOD AND lAPPRATUS FOR COOLING WITH ICE WATER Filed June 28, 1957 .2 SheotsfShcot l INVENTOR.
Gnter Siegfried Hilbert July 22, 1969 i G. s. HILBERT 3,456,452
METHOD AND APPARATUS FOR COOLING WITH CE WATER Filed June 28, 1967 l 2 Sheets-Sheet 2 Fig. 3
United States Patent 3,456,452 METHOD AND APPARATUS FUR CULING WITH ICE WATER Gunter Siegfried Hilbert, Reinbek, Germany, assigner to Alfa-Laval AB, Tumba, Sweden, a corporation of Sweden Filed `'lune 28, 1967, Ser. No. 649,639 Claims priority, application Grrnany, .luly 13, i966, 37,98 Int. Cl. F25d 17/02; B67d 5/62; FZSlJ 41/00 US. Cl. 62-59 9 Claims ABSTRACT F THE DISCLOSURE In the cooling of a liquid such as milk by heat exchange with ice water, a body of ice water is maintained in a collecting zone and, during a cooling period, ice water is circulated from this zone into heat exchange relation to the milk or other liquid, thence downwardly across a succession of horizontal evaporation-cooled surfaces spaced vertically from ea-ch other, and then through a stock of ice and back to the collecting zone. During a cold accumulation period, ice water is circulated from the collecting zone by way of said cooled surfaces and ice stock and back to the zone while forming ice on those surfaces; and the ice thus formed is intermittently thawed to release ice from such surfaces, the stock of ice being replenished by the ice thus released. This formation of ice and concurrent circulation of ice water may be interrupted in response to a predetermined low level of ice water in the collecting zone, to effect said thawing, and resumed in response to a predetermined high level of ice water in the collecting zone. The thawing may also be effected periodically under control of a timer so as to limit the ice formation on said surfaces to strings of ice sufficiently fragile to be broken into a large number of pieces when they are released and fall into the ice stock.
This invention relates to a method and ,apparatus for cold accumulation and cooling of liquids, such as milk from cow barns, by means of a vertically disposed evaporator plate having horizontal internal channels for passage of a cooling agent, a stock of ice, an ice water container, and means including a pump for passing ice water from the container through a circuit including a heat exchanger for cooling the milk or other liquid.
It is known to produce ice by means of evaporator plates or tubes submerged in a body of ice water in a collection container, and to feed the ice water thus cooled to a consumption point where it extracts heat and then back to the collection container. Such systems have the disadvantage that the evaporator plate or tube becomes covered with a skin of ice, which appreciably impairs the heat conduction as the thickness of the ice skin increases. Thus, the ice formation and consequently the cold accumulation are limited and uneconomical. Furthermore, only one side of the ice is in contact with the ice water, thus retarding the thawing process and preventing a suffe ciently rapid release of the accumulated cold to accommodate short periods of high demand.
In order to avoid these disadvantages, a method has been proposed by which ice pieces are frozen in the ice water container and mixed with the ice water. However, it has been found that these ice pieces tend to grow together into lumps, with the result that their surface area Where melting occurs is greatly reduced and the accumulated cold is not available without a correspondingly long thawing period.
The present invention has for its principal object to provide a method and system for cold accumulation and lCC cooling which avoids the abovenoted disadvantages encountered heretofore and by which high cold demand peaks can be satisfied without increasing the capacity of the system. Such cold demand peaks occur more and more frequently, particularly in connection with milk cooling as the practice of pasture milking is increased. Before the milk thus recovered arrives at the farm yard, a large part of the period of incubation has elapsed, so that the cooling must be greatly accelerated in order to prevent the milk from being damaged.
According to the present invention, the ice water is cooled in two successive steps by flowing it first across the cooling surfaces of the evaporator plate or plates and then through a stock of ice, before it is collected in the ice water container. This circuit flow is also maintained during the cold accumulation period in which ice is formed on the evaporator plate or plates, the ice thus formed from the circulating ice water being intermittently thawed and thus released to replenish the ice stock.
In other words, according to the invention, the evaporator plate (or plates) has two functions, namely, the function of direct cooling of ice water during the cooling period and the function of producing ice during a cold accumulation period. In this way, the ice water which has been warmed by heat exchange with the milk or other liquid to be cooled is pre-cooled during the cooling period and before it flows through the ice stock, so that high cold demand peaks can be satisfied, without any prewarming of the ice water which would risk impairment of the desired cooling effect. On the other hand, during the cold accumulation period, the start of the ice formation is advanced by a two step cooling carried out in the same way, and the ice formation itself is made economical by the intermittent thawing, since the energy consumption necessary when freezing thin layers is smaller to such a degree, as compared with freezing thick layers, that the energy loss due to warming of the evaporator in the thawing process is at least compensated.
In the practice of the present invention, the freezing and thawing during the cold accumulation period can be effected automatically, as by means of an adjustable timer, at intervals dependent upon the vertical spacing of the cooling agent channels in the evaporator plate and on the height of fall of the ice from the plate. In this way, the ice formation can be limited to the regions of the cooling agent channels where ice strings will be formed which are sufficiently fragile to be broken into a large number of small pieces when these strings are subjected to shocks incident to their release from the evaporator plate. Thus, not only is the moistened surface of the ice formation increased but also the flow path of the ice water through the ice stock is lengthened.
The ice water circulating pump as well as the means for inducing flow of cooling agent through the evaporator plate may be controlled automatically, as by means of a switch responsive to different levels of the ice water in the collecting container. When this level reaches a predetermined low level, the circulating pump and the flowinducing means for the cooling agent passing to the evaporator plate can be switched olf; and when a predetermined high level of the ice water is attained in the collecting container, the circulating pump and flow inducing means can be switched back on, thereby resuming the formation of ice on the evaporator plate and consequently lowering the level of ice water in the container.
An essential feature of the present invention is that the ice water descends across a succession of horizontal evaporation-cooled surfaces formed by the evaporator plate (or plates) outside its vertically spaced horizontal channels for ow of the cooling agent, and the descending ice water drips from the lower edge of the evaporator plate onto the ice stock from which it is collected in the usual manner in a collecting zone outside the ice stock. In order to provide a ne distribution of the ice water over the ice stock, perforated guide sheets may be interposed below the evaporator plate (or plates) and above the ice stock, these sheets being movable from their water-guiding positions to positions in which they are out of the path of falling ice pieces during the cold accumulation periods. The ice stock may be maintained in a receptacle having a at bottom provided with vertical bai-lies for directing the ice water to an outlet opening which leads to the ice water collecting container, so that part of the ice water flows through the ice stock vertically as well as horizontally.
The invention is described in further detail below, reference being made to the accompanying drawings in which:
FIG. l is a vertical sectional view of a preferred form of the new system;
FIG. 2 is a sectional view on the line I-I in FIG. l, and
FIG. 3 is a schematic view of one form of control means associated with an evaporator plate and the ice water circulating pump.
Referring to the drawings, an insulated container 1 is provided with a flat false bottom 2 which divides the container into an upper receptacle 1a for ice stock and a lower container 1b forming a zone for collecting ice water. The bottom 2 is provided on its upper surface with vertical deflection sheets or bailles 3 for directing ice water in a tortuous flow toward a bottom outlet 4 which opens downwardly into the ice water container 1b. Water guiding sheets 5 are mounted near the upper edge of container 1 and are provided with holes and/ or slots through which water is distributed from the upper surfaces of sheets 5 onto the ice stock 13 in receptacle 1a. The sheets 5 are hinged, as shown at 6, so that each sheet can be swung from a water distributing position (the position of the right-hand sheet in FIG. l) to a position Where it clears the upper part of container 1 (the position of the lefthand sheet in FIG. l). Evaporator plates 7 are mounted vertically above the container 1 and are provided with a series of horizontal channels 8 spaced vertically from each other. The evaporator plates 7 are suspended from a preow vessel 9 having bottom outlets 10 for directing water from the vessel 9 onto both sides of each evaporator plate 7 at its upper portion.
During the cooling period in the practice of the present invention, ice water from container 1b is fed by means of a circulating pump 11 through a heat exchanger 12 and then to the pre-ow vessel 9. By indirect heat exchange in the exchanger 12, the ice water cools the mill: or other liquid which enters the exchanger from line 16 and is discharged from the exchanger through line 16a. From the pre-ow vessel 9, the water descends in thin lms across the opposite outer surfaces of each evaporator plate 7, where a part of the heat acquired in the heat exchanger 12 is removed from the water. This heat removal takes place in an economical manner because the evaporator plates 7 remain free from ice during the cooling period. It will be apparent that each evaporator plate 7 forms a succession of horizontal evaporation-cooled surfaces spaced vertically from each other and located outside the respective horizontal channels 8 for the cooling agent. The ice water drips from the lower edge of each evaporator plate 7 onto the perforated guiding sheets 5, which effect a tine distribution of the water onto the ice stock 13. The latter consists of small, thin ice akes, so that the ice water can pass slowly through the stock while being repeatedly deflected. In this way, an intense heat exchange with the ice stock is effected. A further increase in the heat exchange is accomplished by the fact that a large part of the ice water is moved past the ice stock horizontally in a tortuous path due to the battles or deflection sheets 3, before the water ows through the opening 4 into the body of ice water 14 in container 1b.
The ice water circulation previously described is also maintained during the cold accumulation period, the heat exchanger 12 `being short-circuited by means of a shunt pipeline 15 and an associated valve 15a. Since the ice water now has a lower temperature when it reaches the evaporator plates 7, ice strings 7a are formed on the outer surfaces of each plate in the regions of the cooling agent channels 8; and these strings are removed by periodic thawing before they grow together. The thawing can be started by an automatic control device, such as an adjustable timer 23 (FIG. 3), and terminated by operation of the automatic device. Such intermittent thawing causes the ice strings 7a to be released from the evaporator plates 7; and since the water guiding sheets 5 have been swung upward at the start of the cold accumulation period, the released ice strings fall onto the ice stock 13 where they are split into small flakes. When the ice stock 13 has been replenished in this way so that it acquires a predetermined volume, the level of the ic'e water 14 in container 1b has decreased a corresponding amount. This drop in the level of the ice water 14 may be u'sed to actuate a level-responsive switch 24 (FIG. 3) so as to stop the ice water circulating pump 11 and the ow of the cooling medium to each evaporator plate 7, whereby the entire cold accumulation operation is arrested.
Referring to FIG. 3, each evaporator plate 7 is shown with its cooling agent outlet connected through a pipe 17 to a compressor 18 driven by a motor 18a. The compressed cooling agent passes from compressor 18 through the usual cooling coil 19 to the inlet of the evaporator plate. Due to expansion and evaporation of the cooling agent, it acts in the horizontal channels 8 to cool the surfaces of the evaporator plate adjacent those channels. It will be understood that the cooling cycle, including expansion of the cooling agent and its subsequent compression by the compressor 18, is effected in the manner well known in connection with evaporator plates.
The compressor motor 18a is connected across a source of electrical current 20 by wires 21, one of which includes a switch 22 operated by the timer 23. At regular intervals, switch 22 is opened by its timer 23 so as to de-energize the compressor motor 18a and allow the ice strings 7a to thaw suiciently to fall from each evaporator plate, after which the switch 22 is again closed to freeze new strings of ice on the evaporator plates from the circulating ice water. The motor 11a for driving the ice water circulating pump 11 is also connected across the power line 20, and one side of the latter is provided with the switch 24 which is opened and closed under control of a oat 25. rlfhe latter floats on the surface of the body of ice water 14 in container 1b and is connected through suitable linkage to a collar 26 adapted to move up and down between stops 27 and 28 on the shaft of switch 24. When the level of the ice water body 14 drops to a predetermined value, due to accumulation of ice in the ice stock 13, the collar 26 engages the lower stop 23 and opens switch 24, thereby de-energizing the motors 11a and 18a for driving the ice water circulating pump 11 and the cooling agent compressor 18, respectively. When the `body of ice water 14 rises to a predetermined upper level, due to thawing of ice in the system, the collar 26 engages the upper stop 27 so as to reclose the switch 24, thereby resuming the freezing operation.
I. In the cooling of a liquid such as milk by heat exchange with ice water, the method which comprises maintaining a body of ice water in a collecting zone, cooling said liquid during a cooling period by circulating ice water from said zone through said heat exchange, thence downwardly across a succession of horizontal evaporation-cooled surfaces spaced vertically from each other, and then through a stock of ice and back to the collecting zone; and, during a cold accumulation period, circulating ice water from said zone by way of said surfaces and ice stock and back to the zone while forming ice on said surfaces, intermittently thawing the ice formed on said surfaces, and replenishing said stock with ice released from said surfaces by the thawing.
2. The method according to claim 1, in which the ice release from said surfaces falls into said ice stock, the thawing being effected periodically to limit said ice formation to strings of ice suiciently fragile to be broken into a large number of small pieces by said fall.
3. The method according to claim 1, in which said circulation and forming of ice are interrupted in response to a predetermined low level of the ice water in said zone and are resumed in response to a predetermined high level of the ice water in said zone.
4. In combination with a heat exchanger for cooling a liquid with ice water, a receptacle for a stock of ice, an ice water container communicating with said receptacle for collecting ice water therefrom, a vertically disposed evaporator plate mounted above said receptacle and having outer cooling surfaces and internal channels for flow of a cooling agent, means :for circulating ice Water from said container through said heat exchanger and thence to the upper portion of said evaporator plate for gravity flow across said cooling surfaces, whereby the ice Water descends from the lower edge of the plate into said receptacle and then returns to the container by way of said ice stock, means for inducing ow of a cooling agent through said channels to cool said surfaces of the plate, and means for interrupting said flow of cooling agent to thaw ice formed on said surfaces, whereby said thawed ice is released yfrom said surfaces and falls into said ice receptacle.
5. The combination according to claim 4, in which said channels in the evaporator plate extend horizontally and are spaced vertically from each other.
6. The combination according to claim 4, comprising also perforated sheet means disposed in the path of ice water descending from the evaporator plate to the ice stock in said receptacle, said sheet means being operable to distribute the descending ice water over said ice stock, said sheet means being movable from said path to permit fall of said thawed ice into the ice stock.
7. The combination according to claim 4, in which said ice stock receptacle has a flat bottom and an outlet leading downward into the ice water container, the combination also comprising vertical baffles on said bottom for directing ice water owing to said outlet.
8. The combination according to claim 4, in which said interrupting means include a timer.
9. The combination according to claim 4, in which said interrupting means include control means responsive to a predetermined low level of ice water in said container for effecting said interruption, said control means being responsive to a predetermined high level of ice water in the container for resuming said flow of cooling agent.
References Cited UNITED STATES PATENTS 2,056,970 10/ 1936 Leopold 62-434 2,184,380 l2/l939 Deibel 62-396 2,538,015 1/1951 Kleist 62-434 3,053,060 9/ 1962 Morrison 62-435 WILLIAM I. WYE, Primary Examiner U.S. C1. X.R.