EP2265870A1

EP2265870A1 - Method for manufacturing ice pieces

Info

Publication number: EP2265870A1
Application number: EP09722375A
Authority: EP
Inventors: Stefan Holzer
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2008-03-19
Filing date: 2009-03-13
Publication date: 2010-12-29
Also published as: RU2010139990A; DE102008014887A1; US20110011103A1; CN101978231A; WO2009115454A1

Abstract

The invention relates to a method for manufacturing ice pieces, comprising a first step (S1) of filling a mold with water, a second step (S2) of cooling the water by way of a compressor-operated cooler with an initial compression power and a third step (S3) of reducing the compression power at a time after the beginning of freezing of the water. These method steps facilitate the production of ice pieces from water in a more energy-efficient manner. In a preferred embodiment, the method comprises a fourth step (S4) of shutting off the compressor after the ice pieces are produced from the water, a fifth step (S5) of leaving the ice pieces in the mold for a rest period and a sixth step (S6) of heating the mold for thawing the ice pieces to facilitate the release of the ice pieces from the mold at the end of the rest period.

Description

Process for the production of ice pieces

The present invention relates to a method for producing ice pieces.

Ice makers are known for installation in household refrigerators, for example from DE 10 2005 003 237 A1, in which the low temperatures of a freezer compartment of the household refrigerator are used to freeze the water to pieces of ice. For this purpose, a bowl is filled with water and placed in the freezer. In the cold environment of the freezer, the water slowly cools and freezes to pieces of ice. The length of time from which water has become pieces of ice is generally more than 30 minutes.

Another method of producing pieces of ice is to hold water in a container in which by means of a cooling medium actively cooled metal fingers protrude. The pieces of ice are formed by a layer of ice, which grows on the metal fingers immersed in the water. A related device is known for example from WO 03/054458 A1.

The object of the invention is to produce pieces of ice from water energy-efficiently.

The object is achieved by a method having the features of claim 1.

The inventive method for the energy-efficient production of ice pieces, has at least the following steps:

- filling a mold with water;

- Cooling of the water by means of a compressor operated by a refrigerator with an initial compressor power;

- Reduce the compressor power at a time after the start of freezing of the water. With the process steps according to the invention significantly less energy is required for the production of ice pieces, as with the conventional method. Thus, for the production of ice from a mass of 1 kg of water by setting a bowl of water in a freezer compartment of a conventional household refrigeration appliance (eg according to DE 10 2005 003 237 A1) requires an energy of more than 0.4 kWh. For the production of ice from a mass of 1 kg of water by growing an ice layer on cooled metal fingers (eg according to WO 03/054458 A1), an energy of at least 0.27 kWh is required.

The advantage of better energy efficiency according to the invention is particularly evident in connection with a device for the active production of ice in household appliances, which has at least one shape for receiving water to be frozen, whose inner wall facing the water is connected to a cold generator. In such a device, in contrast to the prior art, the heat is dissipated not via cooled metal fingers, but on the cooled mold wall. The device for the active production of ice in household appliances may comprise at least one water dish in which the water to be cooled is stored, the water dish having a wall which is coolable by direct contact with at least one refrigerant channel.

The device can be aptly described as follows. A shell is cooled by at least one coolant channel. In this case, the shell can be an ice tray with internal refrigerant channels, which are determined by drilling or the casting mold. But it can also be a shell having a preferably flat bottom, which is conductively connected to a flat evaporator such as a Rollbond board heat. But it can also be a massive shell with semi-open U-shaped channels on the bottom, in which a refrigerant pipe leading was pressed. Furthermore, the device can have shell intermediate walls which separate the individual pieces of ice from each other. The refrigerant channels are below the shell, and are formed by a U-shaped tube. In principle, the intermediate walls can also be made hollow and carry refrigerants, but this is not necessary due to the high thermal conductivity of the shell. The shell can be made of aluminum, but it is also highly heat-conductive in particular metallic materials, as well as plastics used bar. The high thermal conductivity allows a greater distance between the water and the refrigerant channel. However, the device is also compatible with a material with a poor In this case, it would be useful to provide several, preferably complex, shaped channels, for example in the intermediate walls. The device may have ejectors, so that the shell can, for example, be firmly fixed for safety reasons. If flexible refrigerant pipes are used, the shell can be rotated so that no ejectors are required. The device for the active production of ice ensures a high freezing capacity at the same time effective energy utilization and low space requirements.

The device just described has a larger contact area between the cooling device and water compared to the cooling by means of fingers immersed in the water, so that the heat transfer from the water to the mold is improved. As a form is understood according to the invention, each recording for the water, which receives a certain amount of water to be frozen to ice. Depending on the desired contour shape for the piece of ice, the shape can be designed differently. The mold may in particular be cup-shaped, e.g. be hemispherical or kreisscheibenabschnittsförmig. The cooling takes place via the cup-shaped wall of the receptacle for the water.

In an exemplary arrangement of such a device, the required electrical power necessary to freeze 100 grams of water to ice was determined. The device comprises, in addition to the form, ie shell which receives the water, an electric refrigerator, which has a compressor whose evaporator side is connected to the mold or the shell. The device was initially operated by a conventional method. In the actively cooled shell, the freezing process begins on the shell surface, ie the pieces of ice freeze from outside to inside. At maximum compressor power, the freezing process starts approx. 3 minutes after filling the water. The initial temperature of the water is 20 ° Celsius. In order to achieve the fastest possible freezing, a strong electric compressor is needed. In the exemplary arrangement, a compressor of the type VEM Z 5C was used, which provides a cooling capacity of 146 watts at its maximum speed at a liquefaction temperature of 45 ° Celsius and an evaporator temperature of minus 20 ° Celsius. The coefficient of performance of this refrigerating machine (COP) is 1.81 at its operating point. The COP, ie the ratio of cooling capacity to applied electrical power, describes the energy efficiency of the system. This figure of merit, assuming a certain quality of the technical equipment, is mainly a function of the temperature rise between the useful cooling provided by the evaporator and the released waste heat at the condenser. The higher the COP the better the energy efficiency. A COP of 3.6 or greater corresponds, for example, to refrigerators of energy efficiency class A.

At maximum power, the exemplary full cycle cycle requires freezing of 100 grams of water to ice, followed by steaming and ejection of the ice cubes for about 15 minutes. This consumes approx. 0.02 kilowatt hours (kWh) of elec- trical energy. Based on 1 kilogram of water or ice, this is 0.2 kWh / kg. The exemplary arrangement thus requires compared to the known setting a bowl of water in a freezer compartment with about 0.4 kWh / kg and cooling by means of metal fingers with about 0.27 kWh / kg already significantly less energy.

An estimate shows, however, that for this system at best only about 0.15 kWh / kg would be required, i. compared to the calculated 0.2 kWh / kg, another 0.05 kWh / kg could be saved, which corresponds to an energy saving of 25%. From the parameters of the exemplary arrangement, the theoretically required minimum amount of energy can be calculated:

Material Mass TSTART TEND ssppeezziiffiisscche Heat Heat quantity or process [g] [° C] [° C] [Y / g] or gK] Q [J] Q [Wh]

Alutray and evaporator 800 4 -10 0.896 10035 2.8

Water 100 20 0 4.18 8360 2.3

Solidification 100 0 0 335.00 33500 9.3

Supercooling ice 100 0 -10 2.10 2100 0.6

Sum of theoretically required energy for 100g water / ice: 15.0 [Wh] The efficiency of the freezing process is thus 0.15 kWh / kg. Theoretically, the consumption of electrical energy could be even lower if the cooling capacity generated by the compressor with a COP greater than 1 loss could be introduced in the form of the aluminum shell (Alutray). In real design, however, at least a small part of the cooling capacity will always be lost to the environment.

In the above consideration, however, the energy for the thawing of the pieces of ice is still disregarded, i. the energy required to heat the mold (alutray and evaporator) from minus 10 degrees Celsius to a temperature above zero degrees Celsius so that the pieces of ice can thaw and be released from the mold.

The method according to the invention is based on the knowledge described below. In the actively cooled shell, freezing begins on the shell surface, i. the pieces of ice freeze from outside to inside. At maximum compressor power, the freezing process starts approx. 3 minutes after filling the water. The initial temperature of the water is 20 ° Celsius. The heat transfer from the solidification front to the evaporator surface (mold wall) is increasingly hindered by the forming ice layer. This is due, on the one hand, to the lower thermal conductivity of the ice and, on the other hand, to the fact that the effective surface for the transport of heat out of the water, i. the surface of the solidification front decreases steadily due to the increasing thickness of the ice layer. Therefore, the evaporation temperature of the refrigerant and the available refrigerating capacity, i.e. the coefficient of performance (COP) of the compressor decreases. After another 8 to 9 minutes, ie at cycle 11 to 12, more than 90% of the water is already frozen. At this point, the evaporator is already colder than minus 15 degrees Celsius. Only after another 2 to 3 minutes, ie at minute 13 to 15 minutes, the remaining water in the middle of the ice is frozen. Due to the very low temperature, the mold or aluminum dish must be warmed from minus 15 degrees Celsius to over zero degrees Celsius when the ice is finally melting. This process requires about 2 to 3 additional minutes, in particular because of the limited power of hot gas defrosting. Overall, the freezing process extends only slightly, taking into account the significantly reduced energy consumption.

In the method according to the invention, the compressor power is reduced from the beginning of freezing. This has the consequence that the shape, ie the inclusion of the water or Alutray is not cooled unnecessarily deep. In the exemplary arrangement is By reducing the compressor capacity at a time after the start of freezing of the water, a drop in the temperature of the mold or trays below minus 15 degrees Celsius prevented. It has been found that, despite reduced compressor performance, the freezing of the water to ice is not appreciably delayed or worsened. At the same time, in the subsequent thawing of the ice cubes, the mold or the tray is only to be heated to above zero degrees Celsius from a less deep temperature (about minus 12 degrees Celsius instead of minus 22 Frad Celsius), so that less energy is needed for heating or cooling ., the Antauen the ice pieces is required.

The compressor performance can be reduced immediately after the start of freezing of the water. Preferably, the compressor power is at least as long to operate under a high and in particular maximum initial compressor power until the solidification heat is dissipated. The greatest energy savings will therefore result if immediately after the compressor power is reduced. However, some energy savings can be achieved even if the compressor power is reduced only a certain time later. This is also within the scope of the invention, wherein in such, less energy-efficient embodiment nevertheless Gebrach of the teaching of the invention, the reduction of the compressor power is made.

The compressor capacity can be reduced to a minimum compressor capacity of the compressor used in each case of the refrigerator. Thus, in the example described (compressor type VEM Z 5C), the compressor capacity can be reduced from 146 watts of cooling capacity to 74 watts, with an evaporation temperature of minus 15 degrees Celsius and a condenser temperature of 35 degrees Celsius with a COP of 2.75. Due to a reduced temperature difference and the COP of the compressor is improved.

The compressor performance can be defined in general so reduced to about 50% of the initial compressor power. Deviating from exactly 50%, the reduction of the compressor power can take place in a frame which continues to ensure the advantages according to the invention, ie in particular be chosen between 40% and 60% or even beyond.

The timing of the reduction of the compressor capacity may vary depending on the type of apparatus for producing pieces of ice, in particular from an empirical one Determination, fixed. For this purpose, the time at which the water begins to freeze can be determined in experiments with the respective device. This time, ie the period of time from the beginning of a process according to the cycle can then be implemented in a particular electrical control of an apparatus for producing pieces of ice.

Alternatively, however, it is also possible to generate a signal during the method which, in particular, causes the electrical control of the device for producing pieces of ice to reduce the compressor power. The beginning of the reduction of the compressor power may in particular be due to a measurement of the temperature of the mold i. the shell in which the water is frozen to pieces of ice, are determined or controlled. However, other sensors that can determine a solidification start of the water are also conceivable.

For example, the reduction in compressor power may occur when the measured temperature of the mold, i. of the tray has reached a predetermined setpoint temperature. In particular, a temperature below -10 degrees Celsius, in particular of -12 degrees Celsius, can be specified as the setpoint temperature.

The shape or the tray is cooled even with reduced compressor performance continues well below the freezing point of the water of zero degrees Celsius, and typically down to minus 15 degrees Celsius. In order not to have to heat too long when Antauen the ice cubes, is proposed in a further development of the invention, at the end of the freezing process, so when the desired Eisstücke are produced from the water, turn off the compressor and wait for a period of time before heating the mold or . of the tray is begun to thaw the pieces of ice.

Such a method would follow the method steps of claim 1 and include the following further steps: shut-off of the compressor after the pieces of ice have been produced from the water, leaving the pieces of ice in the mold for a rest period, - Heating the mold to Antauen the ice cubes for easier release of the ice cubes from the mold, after the end of the rest period.

The rest period can be between 1 and 3 minutes, in particular 2 minutes.

In the period of waiting after the compressor is turned off, i. during the rest period, the tray or tray is self-heating, i. in particular by the influence of the ambient temperature, for example to about minus 5 degrees Celsius. During the heating of the mold from about minus 15 degrees Celsius to minus 5 degrees Celsius, the freezing process in the middle of the piece of ice continues to progress, so that, for example, the compressor could be switched off even slightly before reaching the freezing of the pieces. Since the mold is no longer so cold at the beginning of the heating process, the duration of the fade is considerably shortened, i. for example, about 1 minute. In addition, less heating energy is required for Antauen. Despite reduced compressor performance and the compressor pause, the cycle time is only slightly longer overall, for example, from about 15 minutes to only about 17 to 18 minutes. The cycle includes both the filling of water, the freezing to pieces of ice, the Antauen and evaluating the finished pieces of ice.

In the overall result, the required amount of energy decreases from approx. 0.2 kWh / kg to approx. 0.15 kWh / kg, which means a saving of 25%. Compared to the significant energy savings is to accept only a small loss of throughput. Instead of about 9.6 kg of ice per day can still be produced about 8.0 kg of ice per day. Advantageously, the much quieter operation due to the reduced compressor performance and the introduction of rest periods. Lower compressor and fan speeds are required and a switching noise at the beginning of the defrost reduced. As a side effect, fewer cracks occur in the pieces of ice produced because the thawing to release the pieces of ice from the mold is made more gradual. Due to the more gradual thawing with the upstream resting time, the materials are also protected, ie, without a sudden increase in temperature from maximum cooling capacity to maximum heating power for thawing, in particular the connection between evaporator and mold, ie Alutray, is less mechanically loaded with temperature-related material stresses. An exemplary embodiment of an apparatus for the energy-efficient production of ice pieces is illustrated in the following detailed description, and the temperature profiles of an exemplary cycle of ice production with this apparatus are explained in order to demonstrate the effect of the method according to the invention. From the detailed description of this specific embodiment, there are also other general features and advantages of the present invention.

Show it:

Figure 1 is a schematic representation of the method according to claim 1;

Figure 2 is a schematic representation of the method of claim 9;

FIG. 3 shows a sectional view through an exemplary apparatus for the energy-efficient production of ice pieces according to one of the methods according to the invention;

FIG. 4 shows a diagram of the time course of the temperatures during a cycle according to the invention.

Fig. 1 illustrates a method for energy-efficient production of ice pieces according to claim 1. The method starts after the start with a first step S1 of

Filling a mold with water. This is followed in a second step S2, the cooling of the water by means of a compressor operated by a refrigerator with a

Beginning compressor capacity. The process ends with a third step S3 of reducing the compressor power at a time after the start of freezing of the water. After the step S3, the method of claim 1 is completed.

Fig. 2 illustrates a method for the energy-efficient production of pieces of ice according to claim 9. The method begins again after the start with the first step S1 of filling a mold with water. Thereafter, in the second step S2, the cooling of the water by means of a compressor operated by a compressor with an initial compressor power and in the third step S3, the reduction of the compressor power at a time after the start of freezing of the water. At this third Step S3 is then followed by a fourth step S4 of switching off the compressor after the pieces of ice have been produced from the water. In a fifth step S5, the pieces of ice are left in the mold for a rest period, and in a sixth step S6, the ice pieces are heated to facilitate loosening of the pieces of ice from the mold after the end of the period of rest in step S5. After the step S6, the method according to claim 9 is completed.

In Fig. 3 is a mold 1 for producing a piece of ice is shown schematically in section. An exemplary apparatus for the energy-efficient production of ice pieces according to one of the methods of the invention may in particular have a plurality of such forms 1, which are arranged in a spatially ordered proximity to one another analogously to an ice cube tray, in particular can be combined in one unit. The mold 1 is exemplified as an aluminum shell, with a base body 2 of aluminum and a half-shell-shaped inner wall 3. In the mold 1 adjacent to the inner wall 3, an ice layer 4 is shown, which is in formation and ends adjacent to a momentarily remaining amount of water 5 , There is a solidification front 6 at the boundary between the ice layer 4 and the amount of water 5. From the amount of water 5 flows a heat flow, shown as arrow 7, to an evaporator plate 8, which is connected to a cold generator, not shown. The heat from the amount of water 5 is discharged along the heat flow (arrow 7) into the evaporator plate 8, so that the solidification front 6 continues to increase upward as the cooling progresses in FIG. 3 until the water quantity 5 has completely solidified into ice.

4 shows a diagram of the time profile of the temperatures during a cycle according to the invention for an apparatus according to FIG. 3 by way of example. The time course of the temperatures is designed for 100 grams of water. The two upper temperature lines, which are located predominantly in the region of plus degrees, represent the temperature profiles in the water. The temperature curve shown to the top represents the temperature profile over the time of the water to be frozen, without the method according to the invention, ie without reducing the compressor output. Just below and partially congruent, the temperature profile over the time of the water to be frozen with the inventive method is shown. The temperatures of the water were determined in the center of the water, ie at a point at which the last time freezing occurs. Both temperature profiles of the water start at the minute 0 with a starting temperature of about 20 to 21 degrees Celsius. Significantly, in the following minutes, both temperature curves run in almost identical fashion. Only at about minute 1 1, 5, the two temperature gradients differ. The temperature profile with ongoing maximum compressor power tilts at this time below the zero degrees Celsius limit, ie the ice is completely frozen through at this time. With a reduction of the compressor capacity according to the invention, here by about 50%, the temperature profile tilts only at about 13.5 minutes below the zero degree Celsius limit, ie the ice is completely frozen through to this later date. This course illustrates the manufacturing process of the ice pieces and shows that completely frozen ice pieces are completed only slightly later with the inventive method of reducing the compressor capacity. The delay is only about 2 minutes of a total of about 15 to 17 minutes Gesamtherstelldauer.

In the two lower temperature lines, predominantly in the region of minus degrees, of FIG. 4, the curves of the temperatures over time in the mold, i. presented in an aluminum tray. First, start both temperature curves, with and without inventive reduction of the compressor power, at about 12 to 13 degrees Celsius of the mold. By adding water from a temperature of approx. 20 to 21 degrees Celsius, the mold temperature initially increases to approx. 15 to 16 degrees Celsius for a short time before dropping rapidly in both temperature curves due to the maximum compressor capacity up to 6.5 minutes , From the minute 6.5, the essential difference between the state of the art and the method according to the invention is evident in the two temperature profiles. While according to the state of the art even after the minute 6.5 cooling continues with full compressor power, the compressor power is reduced according to the invention at this time, in the example by about 50%. This has the consequence that the temperature of the mold in a period between minutes 12 and 13 does not drop to a value of about minus 20 degrees Celsius, but settles only at about minus 10 degrees Celsius. The area between the temperature curves of maximum compressor power and reduced compressor power represents a proportion of energy savings. In the course of the temperature of the maximum compressor capacity results in about 13 minutes a kink by the complete shutdown of the compressor. In the course of the reduced compressor speed, a compressor pause according to the invention closes between minute 13.5 and 15.5 before the mold is heated.

Claims

claims

1 . Process for the production of ice pieces, comprising the following steps: - filling (S1) a mold with water;

- cooling (S2) the water by means of a compressor operated by a refrigerator with an initial compressor power;

- Reduce the compressor capacity (S3) at a time after the start of freezing of the water.

2. The method according to claim 1, characterized in that the compressor power is reduced immediately after the start of freezing of the water.

3. The method according to claim 1 or 2, characterized in that the compressor power is reduced to a minimum compressor power of the compressor used in each case of the refrigerator.

4. The method according to claim 1 to 3, characterized in that the compressor power is reduced to about 50% of the initial compressor power.

5. The method according to claim 1 to 4, characterized in that the time of reducing the compressor power depending on the type of a device for the production of ice pieces, in particular from an empirical determination, fixed fixed.

6. The method according to claim 1 to 4, characterized in that the beginning of the reduction of the compressor power is determined or controlled on the basis of a measurement of the temperature of the mold.

7. The method according to claim 6, characterized in that the reduction of

Compressor power then takes place when the measured temperature of the mold has reached a predetermined target temperature.

8. The method according to claim 7, characterized in that as the target temperature, a temperature below -10 degrees Celsius, in particular of -12 degrees Celsius is specified.

9. The method according to claim 1 to 8, characterized by the further steps:

Switching off the compressor (S4) after the pieces of ice have been produced from the water,

- Leaving the pieces of ice in the mold (S5) for a rest period, - Heating the mold (S6) for thawing the ice pieces for a facilitated release of the ice cubes from the mold, after the end of the rest period.

10. The method according to claim 9, characterized in that the rest period is between 1 and 3 minutes, in particular 2 minutes.