Patent Application
20100050657
The present invention relates to a refrigerator and/or freezer with a magnetic cooler, comprising a cold heat exchanger for cooling the cooling and/or freezing space of the appliance and means for detecting a value representative of the temperature of the cold heat exchanger.
Refrigerators and/or freezers with magnetic cooling operate according to the principle of the so-called magnetocaloric effect. It is known from the prior art that the magnetic cooler includes heat exchanger units which are made of a material or include a material that is heated upon magnetization and undergoes a decrease in temperature upon demagnetization. When a heat transfer medium, such as brine or an alcohol mixture, is passed through the heat exchanger unit heated in this way, it undergoes an increase in temperature. On the other hand, when it is passed through the cold heat exchanger unit, it correspondingly undergoes a decrease in temperature. The heat transfer medium cooled in this way then is passed through the so-called cold heat exchanger, which is arranged inside or in the vicinity of the cooling and/or freezing space and serves for cooling the same.
In prior art refrigerators and/or freezers it is common practice that the magnetic cooler with pump is switched off when a temperature switch-off value is reached. This means that the magnetic cooler and the pump are switched off when the heat exchanger or the space to be cooled has reached a specified lower temperature value. With the magnetic cooler and pump switched off, heating of the cooling and/or freezing space and of the cold heat exchanger then is effected. Switching on the magnetic cooler with pump only will be effected again when the cold heat exchanger has been defrosted completely. Switching on again can for instance be effected at a temperature of the cold heat exchanger of +5° C.
This procedure is disadvantageous in so far as the energy consumption of the appliance is comparatively high and in addition temperature fluctuations exist due to the periodic operation of the magnetic cooler and the pump.
Therefore, it is the object underlying the present invention to develop a refrigerator and/or freezer as mentioned above such that the same is improved in terms of energy consumption, and in which temperature fluctuations are avoided or reduced to a minimum.
This object is solved by a refrigerator and/or freezer with the features of claim 1. Accordingly, it is provided that the appliance includes a control or adjusting unit by means of which the temperature and/or the amount of the heat transfer medium supplied to the cold heat exchanger is adjustable such that in cooling operation the temperature of the cold heat exchanger does not go below +0° C. This means that the control or adjusting unit adjusts the refrigerating capacity such that the cold heat exchanger does not adopt a temperature of below 0° C., whereby icing of the same can effectively be prevented. Due to the reduced refrigerating capacity, the cold heat exchanger must be designed comparatively large corresponding to the size of the cooling and/or freezing space, in order to be able to provide the required cooling in general.
The appliance can include a pump for delivering the heat transfer medium, and the control or adjusting unit can be configured such that it acts upon the delivery volume of the pump. It thus is conceivable, for instance, to reduce the delivery volume of the pump, i.e. the rate of delivery of the heat transfer medium delivered by the pump, in order to ensure that the cold heat exchanger does not reach temperatures of below 0° C.
It is likewise conceivable that the control or adjusting unit is configured such that it acts upon the strength and/or position of the magnetic field present in the magnetic cooler. Thus, it is furthermore conceivable to reduce the refrigerating capacity for instance by reducing the magnetic field. If a weaker magnetic field is present, the magnetocaloric effect is reduced correspondingly and the heat transfer medium flowing through the magnetic cooler is heated or cooled to a reduced extent, so that the refrigerating capacity of the cold heat exchanger is reduced correspondingly.
In a further aspect of the invention it is provided that the control or adjusting unit is configured such that the delivery volume of the pump and/or the magnetization in the magnetic cooler is effected in dependence on a control deviation, i.e. the deviation of the measured value from a desired value or a range of desired values. If the measured temperature already lies within the range of the desired temperature value, a change in the delivery volume of the pump or in the magnetization in the magnetic cooler may not be required, or an increase or reduction of the delivery volume of the pump or of the strength of the magnetic field is considered in dependence on the control deviation.
Thus, it is conceivable to employ the delivery volume of the pump and/or the strength or position of the magnetic field as control variables of a control circuit, whose setpoint represents a temperature value or also a temperature range.
One advantage of the present invention consists in that the magnetic cooler and/or the pump for delivering the heat transfer medium can be configured such that they are running in continuous operation. This is due to the fact that a defrosting cycle is not required in accordance with the invention, since the cold heat exchanger is not, or at best for a short period, operated at temperatures below 0° C. If the temperature of the cold heat exchanger nevertheless falls below 0° C., it can be provided that a defrosting cycle is employed acyclically, if this is necessary. The advantages of the invention consist in that due to the uniform and constant operation of the magnetic cooler and/or the pump, the energy consumption of the appliance is reduced as compared to prior art appliances, and that temperature fluctuations do not occur or only to a reduced extent.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2006 018 265.9 | Dec 2006 | DE | national |
| 20 2007 003 576.4 | Mar 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/009947 | 11/16/2007 | WO | 00 | 5/29/2009 |
