DE29603716U1 - Cooling unit - Google Patents

Description

28 February 1996 96-1549 G-st

Liebherr-Hausgeräte GmbH, 88416 Ochsenhausen

Cooling device

The invention relates to a refrigerator with a normal cooling chamber, preferably with a normal cooling chamber and a freezer compartment, the evaporator of which consists of two evaporator sections connected in series with pipe sections carrying the coolant, of which the section into which the compressor provided with a control device introduces the coolant is assigned to the freezer compartment.

In conventional refrigerators with a standard refrigerator compartment and a 3-star freezer compartment, the connected evaporator system and the insulation of the appliance are basically designed in such a way that at normal ambient temperatures (+16 ⁰ C to +32 ⁰ C) the freezer compartment maintains a temperature of at least -18 ⁰ C at certain positions of the thermostat regulating the temperature in the standard refrigerator compartment, while the standard refrigerator compartment can have temperatures between 0 ⁰ C and +5 ⁰ C depending on the position of the thermostat. For example, at an ambient temperature of 25 ⁰ C and a temperature of 5 ⁰ C in the standard refrigerator compartment, this means a temperature difference of 20 K between the ambient temperature and the standard refrigerator compartment and of 43 K between the 3-star freezer compartment. Due to these values, the thickness of the insulation around the 3-star freezer compartment of the refrigerator is usually thicker than around the normal refrigerator compartment.

Problems in maintaining the minimum temperature of -18 ⁰ C in the freezer compartment arise at lower ambient temperatures because, for example, at an ambient temperature of 10 ⁰ C, the difference between the ambient temperature and the temperature in the normal refrigerator compartment at 5 ⁰ C is only 5 K and the difference between the ambient temperature and the freezer compartment is 28 K.

A refrigerator with a freezer compartment is usually controlled by a thermostat whose temperature sensor is located in the normal refrigerator compartment and preferably on the evaporator plate. The switch-on values of this thermostat are designed so that the evaporator section for the normal refrigerator compartment defrosts each time the compressor is switched off. For this to happen, the temperature on the surface of the evaporator in the normal refrigerator compartment must rise to at least 0 ⁰ C. Normal switch-on values for the thermostat are between 3 ⁰ C and 5 ⁰ C. This means that if the switch-on value of the thermostat is, for example, 5 ⁰ C, if the ambient temperature drops below 5 ⁰ C the thermostat will no longer switch on at all, which will inevitably cause the temperature in the freezer compartment to rise. The goods in the freezer compartment can then heat up to the point of thawing, meaning that the refrigerator is no longer fully functional. Even at ambient temperatures above 5 ⁰ C up to about 9 ⁰ C, there are still considerable problems in maintaining the required minimum temperature in the freezer compartment, since the relative duty cycle of the compressor is too short to provide the cooling capacity required for the evaporator compartment.

In order to ensure that the minimum temperature in the freezer compartment is maintained even when the ambient temperature falls below normal temperature, i.e. below 16 ⁰ C, it is known to adjust the relative duty cycle of the compressor to the minimum required cooling capacity of the freezer compartment. In the case of refrigerators that are heavily insulated for the purpose of saving energy,

The cooling requirement for the cooling part is very small. Since the refrigerator compartment evaporator is connected in series with the freezer compartment evaporator, the refrigerator compartment evaporator also receives a relatively high amount of coolant due to the compressor's relative duty cycle, which is adjusted to the freezer compartment's cooling requirement. In order not to cool the normal refrigerator compartment too much, the refrigerator compartment evaporator is made very small. In addition to its function as a heat exchanger, the refrigerator compartment evaporator also forms the dehumidification plate on which the condensate settles, so that the condensed water can drip off the refrigerator compartment evaporator into collecting channels and be drained via these, for example, to the compressor for the purpose of evaporation.

At high ambient temperatures and/or high humidity and/or high door opening frequency, the dehumidification surface formed by the small refrigerator evaporator can become too small, so that condensation can form in other parts of the refrigerator, particularly on the refrigerator compartment ceiling, which can be at a temperature lower than the dew point due to the adjacent freezer compartment, and on the glass panels. If condensation forms in places other than on the refrigerator evaporator panel, the condensed water cannot be drained away in a targeted manner, but instead drips undesirably onto the refrigerated goods.

The problem of unwanted condensate formation in places other than on the refrigerator compartment evaporator plate does not only exist in refrigerators with a normal refrigerator compartment and a freezer compartment, but also in refrigerators that do not have a freezer compartment.

The object of the invention is therefore to provide a cooling device of the type specified at the outset, in which a dripping

Prevents the formation of condensate on parts of the refrigerator compartment other than the refrigerator compartment evaporator.

According to the invention, this object is achieved in a cooling device of the type specified at the outset in that the evaporator or evaporator section assigned to the normal cooling chamber consists of a plate made of a material that conducts heat well, the size of which is designed for the area required for dehumidification, and that the plate is connected to the pipe section carrying the coolant in such a way that the cooling capacity required for the normal cooling chamber is supplied to the latter with essentially the same temperature distribution.

If the cooling capacity is supplied to the normal cold room through a small cooled area, the disadvantage is that the cooling capacity per area is too high. Such a small cooled area with high cooling capacity means that dehumidification only takes place in the area surrounding the cooling area, so that the moisture accumulates in the areas of the normal cold room that are further away from the area supplying the cooling capacity. Supplying the cooling capacity through a small area also has the disadvantage that this area can freeze over, which reduces the cooling capacity.

In the cooling device according to the invention, the cooling capacity per area of the evaporator plate is reduced so that it delivers the required cooling capacity with a reduced surface temperature. According to the invention, the evaporator plate assigned to the normal cooling chamber is thus made large enough to form a sufficiently large dehumidification surface and is also kept at a temperature such that it delivers the required cooling capacity.

The pipe section carrying the coolant can be connected to the cold storage evaporator plate only over part of its length and/or via material that conducts heat poorly, such that only the required cooling capacity is supplied to the normal cold storage despite the enlarged plate due to thermal decoupling.

According to a preferred embodiment of the invention, it is provided that the pipe section connected to the evaporator plate of the normal cooling chamber or running in this plate and carrying the coolant has a length corresponding to the heat output to be transferred. The pipe section can be connected directly to the evaporator plate by clamp connections or connections of a conventional type or can also be integrated into the plate, as is the case with roll or Z-bond evaporator plates.

According to a preferred embodiment of the invention, it is provided that the pipe section carrying the coolant is connected to the plate over at least part of its length or runs in it and that the plate is provided with recesses or window-like openings. These recesses allow the total area that the evaporator plate takes up in terms of its outline to be increased even further, so that the surface area over which the cooling power is supplied is increased even further.

The plate is conveniently provided with rows of recesses, with the pipe sections carrying the refrigerant running between the rows.

It is advisable for the pipe sections carrying the coolant, apart from the edge rows, to run only between

every second row of recesses. In this way, the cold is introduced into each section of the evaporator plate, which is provided with the rows of recesses, from only one side, so that a particularly good, even temperature distribution is achieved across the plate.

Condensed moisture settles on parts whose temperature is below the dew point temperature. When the compressor is switched off, the temperature of the evaporator plate in the cooling chamber rises to over 0 ^° C, which is necessary to defrost the evaporator plate and the pipe section laid on it or the walls of the cooling chamber behind which the evaporator is foamed in. It is therefore possible that, for example, the cooling section ceiling temporarily has a temperature that is below that of the evaporator plate and below the dew point temperature when the compressor is switched off. However, during times when the temperature of the cooling section ceiling is temporarily below that of the evaporator plate, not so much moisture must settle on the cooling section ceiling that it can drip. In a further embodiment of the invention, it is therefore provided that the thermal coupling of the pipe section assigned to the normal cooling chamber to the evaporator plate in the normal cooling chamber is selected so that its temperature is essentially below the dew point temperature. The size of the evaporator plate and its thermal coupling to the pipe section carrying the refrigerant are expediently selected in such a way that condensate temporarily forming on the cooling section ceiling evaporates again and then condenses on the evaporator plate of the normal cooling chamber when its temperature is again below the dew point temperature and the temperature of the cooling section ceiling after the compressor has started up again.

According to the invention, the evaporator plate assigned to the normal cooling chamber is designed to be large enough to form a sufficiently large dehumidification surface and is thermally coupled to the pipe section carrying the coolant or, in the case of a complete heat-conducting connection with the evaporator plate, is only long enough so that the surface temperature of the evaporator plate is only just below the dew point. This means that an evaporator plate with a significantly larger surface area that forms a heat exchanger can be arranged in the normal cooling chamber or the cooling capacity can be supplied through a much larger wall surface of the normal cooling chamber if the evaporator is foamed in behind the cooling chamber wall, without the cooling capacity for the normal cooling chamber becoming too large and the cooling chamber temperature thereby falling too far.

If the evaporator plate with openings is foamed in behind a cooling chamber wall, the wall area through which the cooling power is supplied to the normal cooling chamber can be significantly increased. The recesses themselves are closed by the wall of the normal cooling chamber, which consists of a plastic plate, so that the temperature gradually decreases from the edges of the recesses to their middle areas during the compressor switch-on phases, so that the recessed areas also participate in the transfer of the cooling power.

The arrangement of the recesses in the evaporator plate enables the direct connection of the pipe section carrying the coolant to the plate or the integration of this section into the plate, so that the reproducibility of the transfer of the cooling capacity to the evaporator plate is more favourable than with only point-based connection or connection only over short distances or insulating materials to the evaporator plate. The arrangement of the recesses in the evaporator plate enables the pipe section carrying the coolant to be directly connected to the plate or to the evaporator plate.

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ferplatte, this can be stretched over a desired larger area of the normal refrigerator interior wall.

The type of thermal coupling of the pipe section to the evaporator plate or the length of the pipe section connected to the evaporator plate and the size of the evaporator plate can be calculated for the different types of cooling device or determined empirically. In any case, the area of the evaporator plate of the standard cooling room must be chosen to be large enough to fulfil its function as a dehumidification plate, whereby the thermal coupling of the dehumidification and evaporator plate to the pipe section carrying the coolant or its length must be carried out and selected in such a way that the cooling capacity is not too high and the temperature still falls below the dew point during the compressor switch-on phases.

The liquefied refrigerant is fed to the evaporator via a capillary tube, which forms a throttle element. Since the liquefied refrigerant has a relatively high temperature, the line leading the liquefied refrigerant to the capillary tube is laid in the suction line through which the compressor sucks in the evaporated refrigerant from the evaporator. This cools the liquefied refrigerant, since the refrigerant vapor in the suction pipe is still at a relatively low temperature. Nevertheless, the refrigerant expanded in the capillary tube is still at a higher temperature before it, so that the residual heat of the refrigerant must also be dissipated, which worsens the energy balance.

In order to make favorable use of the residual heat of the liquefied coolant, according to a preferred embodiment of the invention, for which independent protection is claimed, a section of the liquefied coolant is supplied to the

Capillary tube is in heat-conducting connection with the normal cold room evaporator plate. This design leads to part of the residual heat being removed from the liquefied coolant, which has energy advantages and leads to an improvement in efficiency, and to heat being supplied to the cold room evaporator plate, so that its cooling capacity is reduced in the desired way. This supply of heat to the cold room evaporator plate is not only useful for the evaporator plate according to the invention, which is only connected to the pipe section carrying the coolant with reduced heat conduction, but also for conventional cooling devices with a 3-star compartment. It is known that, when the ambient temperature in refrigerators is below normal, a heating device can be installed in the normal refrigerator compartment or behind the wall of the normal refrigerator compartment, which supplies heat to the normal refrigerator compartment if the temperature difference between the temperature in the normal refrigerator compartment and the ambient temperature is too small to ensure that the compressor is switched on for a relative period of time that ensures the target temperature in the freezer compartment is no longer achieved. The supply of heat to the refrigerator compartment evaporator through a section of the line carrying the liquefied coolant can therefore make an additional heating device in the normal refrigerator compartment superfluous.

In the case of refrigerators with a normal refrigerator compartment and a deep-freeze compartment, the evaporators of which consist of two evaporator sections connected in series, the transition area of the evaporator between the deep-freeze evaporator section and the normal refrigerator compartment evaporator section, which is located in the area of the normal refrigerator compartment, is critical because this transition area is at a lower temperature than the main surface of the freezer compartment evaporator, so that this transition part has an undesirable tendency to freeze up. In order to prevent this critical area from freezing up,

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According to another preferred embodiment of the invention, for which independent protection is claimed, a section of the line leading the liquefied coolant to the capillary tube is laid in the transition area between the two evaporator sections in or near the normal cooling chamber. This section of the line leading the liquefied coolant is expediently located in a heat-conducting connection with the transition area, so that it is guaranteed that this critical transition area also defrosts during the compressor downtimes.

An embodiment of the invention is explained in more detail below with reference to the drawing.

Fig. 1 is a perspective view of a cooling device,

partly in section, which is provided with the dehumidification evaporator plate enlarged according to the invention,

Fig. 2 a top view of an evaporator plate foamed in behind the rear wall of the normal cooling chamber and provided with recesses,

Fig. 3 a rear view of a conventional refrigerator with a normal refrigerator compartment and a freezer compartment and

Fig. 4 is a section through the cooling device along the line H-II in Fig. 3.

The conventional cooling device shown schematically in Fig. 3 and 4 consists of a housing 1 with an outer shell and an inner shell, whereby the space between the shells serves to

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Thermal insulation is foamed with polyurethane foam. The U-shaped evaporator section 3 assigned to the freezer compartment 2 is arranged and foamed behind the shell of the freezer compartment. The evaporator section 5 assigned to the normal refrigerator compartment 4 is also foamed behind the inner normal refrigerator compartment shell. Both evaporator sections 3, 5 are bent out of a common roll or Z-bond evaporator board and connected to one another by a narrow board strip 6 in which the lines are arranged through which the two evaporator sections are connected in series.

The condenser 7 is arranged in the usual way behind the rear wall of the refrigerator and the compressor 8 is located in a niche in the refrigerator housing. A thermostat 9 is arranged on the refrigerator evaporator section, which controls the switching-on frequency of the compressor.

In the known refrigerator shown in Figs. 3 and 4, only a very small dehumidification surface is provided, which is formed by the area of the rear wall of the normal refrigerator compartment, behind which the normal refrigerator compartment evaporator section is located. In a refrigerator of this type, condensate can therefore form on the refrigerator compartment ceiling below the freezer compartment or on glass panels at high ambient temperatures and/or high humidity and/or high door opening frequencies, so that water can drip off.

Fig. 1 shows a refrigerator in which an evaporator plate 10, reduced in size in accordance with the low cooling requirement of the normal cooling chamber, is arranged in the normal cooling chamber, the lower edge of which is indicated by the dashed line 11. Although in the case of an evaporator plate arranged freely hanging in the normal cooling chamber, the front and the

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rear side are effective as dehumidification surfaces, the total size of the dehumidification surface is not sufficient to completely dehumidify the normal cold room due to the reduced standard cold room evaporator and to prevent condensation from forming, for example, on the normal cold room ceiling.

In order to ensure sufficient dehumidification of the normal cold room under all conditions, the normal cold room evaporator plate 10 is enlarged by the evaporator plate 12 marked with a dashed line, which is integrally connected to the lower edge of the evaporator plate 10 marked with a dashed line. In order not to increase the cooling capacity for the normal cold room unacceptably by enlarging the evaporator plate in this way, the evaporator plate 10, 12 is only connected to the evaporator plate at the points marked with crosses 13.

The connection of the pipe coil 14 carrying the coolant to the dehumidification evaporator plate 10, 12, either at specific points or in sections, can be carried out in the usual way by spot welding, crimping, gluing or by clamping connections.

Under the dehumidification evaporator plate 10, 12, channels are provided in the usual way to collect and drain the dripping water.

Fig. 2 shows a schematic top view of an evaporator plate 15 foamed in behind the rear wall of a normal cold room. This consists of a so-called roll or Z-bond evaporator plate, in which the pipe section 16 carrying the coolant is arranged in an approximately rectangular shape. The plate is provided with four rows of adjacent rectangular recesses 17. The horizontal

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right branches of the pipe sections 16 between the rows of recesses 17 in such a way that each row is supplied with cooling power from only one horizontal branch of the pipe section 16. The influence of the vertical branches of the pipe section is neglected here. This could also be reduced by lateral, gap-shaped recesses enclosing them. In order to ensure that each row of recesses 17 receives its cooling power essentially only from one horizontal branch of the pipe section, these run in a board with four rows of recesses between the first and second rows and between the third and fourth rows, so that they are each at a distance of a from the upper and lower edge and a distance of aa from each other.

Claims (10)

28 February 1996 96-1549 G-st Liebherr-Hausgeräte GmbH, 88416 Ochsenhausen Refrigeration appliance Protection claims: 1. Refrigeration appliance with a normal refrigeration chamber, preferably with a normal refrigeration chamber and a freezer compartment, the evaporator of which consists of two evaporator sections connected in series with pipe sections carrying the coolant, of which the section into which the compressor provided with a control device introduces the coolant is assigned to the freezer compartment, characterized:, that the evaporator or evaporator section assigned to the normal cooling room consists of a plate made of good heat-conducting material, the size of which is designed for the area required for dehumidification, and that the plate is connected to the pipe section carrying the coolant in such a way that the cooling capacity required for the normal cold room is supplied to it with essentially the same temperature distribution. 2. Cooling device according to claim 1, characterized in that the pipe section carrying the coolant is connected to the cooling chamber evaporator plate only over part of its length and/or via material that conducts heat poorly, such that only the required cooling capacity is supplied to the normal cooling chamber despite the enlarged plate due to thermal decoupling. 3. Cooling device according to claim 1, characterized in that the pipe section connected to the cooling chamber evaporator plate or running in this plate has a length corresponding to the cooling capacity to be transferred. 4. Cooling device according to claim 1, characterized in that the pipe section carrying the coolant is connected to the cooling chamber evaporator plate at least over part of its length or runs in it and that the plate is provided with recesses or window-like openings. 5. Cooling device according to claim 3 or 4, characterized in that the cooling chamber evaporator plate is provided with rows of recesses and parts of the pipe section connected to it run between the rows. 6. Cooling device according to claim 5, characterized in that parts of the pipe sections, apart from the edge rows, only run between every second row. 7. Cooling device according to one of claims 1 to 6, characterized in that the evaporator plate is foamed behind at least one wall of the normal cooling chamber, preferably behind the rear wall. 4 · ■· 8. Cooling device according to one of claims 1 to 7, characterized in that the thermal coupling of the pipe section assigned to the normal cooling chamber to the normal cooling chamber evaporator plate
or its associated length so
is selected so that the temperature of the normal cold room evaporator plate or the temperature of the normal cold room wall, behind
in which the evaporator plate is foamed, essentially
is below the dew point temperature. 9. Cooling device, in particular according to one of the preceding claims,
characterized in that a section of the line leading liquefied refrigerant to the capillary tube is in heat-conducting connection with the normal cold room evaporator plate. 10. Cooling device, in particular according to one of the preceding claims, characterized in that a section of the line leading liquefied coolant to the capillary tube in the transition region between the two evaporator sections
is laid in or near the cold storage room and is in heat-conducting connection with this transition area.