EP3314181A1

EP3314181A1 - Refrigeration unit with air humidity monitoring

Info

Publication number: EP3314181A1
Application number: EP16726335.9A
Authority: EP
Inventors: Niels Liengaard; Hanna KÖZLE; Antje ENGSTLER
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2015-06-26
Filing date: 2016-06-02
Publication date: 2018-05-02
Also published as: CN107810375A; DE102015211960A1; US20180187968A1; WO2016206938A1; CN107810375B

Abstract

In the context of a refrigeration unit having a storage chamber (1) and an evaporator (4) that cools the storage chamber (1), a processing unit (8) is set up, at a given temperature (T) of the storage chamber (1), to assign values of the air humidity (r) in the storage chamber (1) and an evaporation temperature (TD) of the evaporator (4) to one another with the assumption that the absolute water vapor content of the air of the storage chamber (1) is the same as that of water-vapor-saturated air at the evaporation temperature (TD). This assignation makes it possible on one hand to estimate the relative air humidity in the storage chamber (1) on the basis of the temperatures, and on the other hand to control the air output temperature (TD), at constant temperature (T) in the storage chamber (1), in order to influence the air humidity (r) therein.

Description

Refrigeration unit with humidity monitoring

The present invention relates to a refrigerator, in particular a household refrigerator.

The relative humidity that prevails in a storage chamber of a refrigerator is of high importance for the shelf life of food therein. Especially for the storage of fresh vegetables, a high humidity is desirable. In refrigerators in which air is circulated between the storage chamber and a heat exchanger, typically in the so-called NoFrost refrigerators, such high humidity is difficult to maintain because the air, when cooled below its dew point on a surface of the heat exchanger, There loses moisture that must be removed from the refrigerator and eliminated. This water loss leads to a rapid wilting of the vegetables.

In order to be able to store vegetables longer, vegetable compartments have been developed, which contain a container that can be closed with a lid. When the container is sealed, the moisture released from vegetables contained therein can not escape, and at the same time the container can be cooled by circulating cold air over its outer surfaces. By an adjustable opening of the container, a limited exchange of air between the container interior and the environment can be made possible, so that depending on the size of the opening different values of humidity in the container can be adjusted. It is difficult to measure this humidity and to display it visibly to a user on the outside of the refrigeration device, since the humidity sensor would have to be mounted in the container and its output signal would have to be transmitted from the refrigeration device movable container to a display device of the refrigeration device, without the freedom of movement of the container limit.

Therefore, it is usually dispensed with a humidity measurement, and how high the humidity in the container is in fact, the user is not known in the rule. Therefore, he can essentially find out only on the basis of his own observations, which opening degree of the container is appropriate for which refrigerated goods. However, such observations are complicated by the fact that the humidity in the Interior of the container not only depends on the size of the opening, but indirectly, over the operating times of the evaporator, is also influenced by the ambient climate. This makes it difficult to detect a relationship between the opening degree of the container and the shelf life of the refrigerated goods for the user. The object of the invention is to provide a refrigeration device or a Betrie bsverfahren for a refrigerator, which give the user improved control over the humidity in the refrigerator.

The object is achieved on the one hand by a refrigeration device with a storage chamber and a storage chamber cooling evaporator, wherein a processing unit is set to assign at a given temperature of the storage chamber values of humidity in the storage chamber and a vaporization temperature of the evaporator each other assuming that the absolute water vapor content of the air in the storage chamber is the same as that of water vapor saturated air, i. H. Air with 100% relative humidity, at the evaporation temperature.

The assignment can be made in different directions and serve different purposes. According to a first aspect, there are provided sensors for measuring the temperature of the storage chamber and the evaporation temperature, and the processing unit is arranged to assume a value of the evaporation temperature when given, to estimate the humidity corresponding to the temperature of the storage chamber, and the like to display estimated air humidity on a display instrument. In this way, a user can obtain quantitative information about the humidity in the storage chamber, without directly in this an air humidity sensor must be provided, which is particularly difficult if the storage chamber, as usual for vegetables compartments, designed as a pull-out box.

Even more important than knowing the humidity in the storage chamber is the ability for a user to adjust the humidity in the storage chamber. Therefore, according to a second embodiment, the assignment takes place in the opposite direction. For this purpose, a control element is provided to adjust the humidity in the storage chamber as a target size, and the processing unit is with the Control connected and set up, when assigning to a set on the control, given target value of the humidity estimate a target value of the evaporation temperature and to match the real evaporating temperature of the evaporator to the target value. When the air of the storage chamber is cooled down to the evaporating temperature in contact with the evaporator, it can hold only as much water vapor as corresponds to 100% relative humidity at the evaporating temperature. By choosing this evaporation temperature appropriately, a desired relative humidity can be set for the same air after heating to the temperature of the storage chamber. In order to allow control of the evaporation temperature, the evaporator may be part of a refrigerant circuit in which the flow rate of a compressor is controllable to vary the pressure in the evaporator.

Alternatively or additionally, an influencing of the evaporation temperature is also possible by controlling the opening cross-section of at least one throttle valve connected in series with the evaporator, upstream or downstream.

If the temperature of the storage chamber remains the same, if a high humidity in the storage chamber is to be maintained, the evaporation temperature must be set higher than for a low value of the humidity.

In particular, but not only, in a refrigeration device in NoFrost design, with a partitioned from the storage chamber evaporator chamber, a fan with controllable throughput may be provided to circulate air between the evaporator and the storage chamber.

The faster the fan runs, the lower the temperature difference between the upstream and downstream sides of the evaporator. During slow running, the heat input at the downstream end of the evaporator is low, and it can set a low evaporation temperature, through which the air flowing through is strongly dehumidified; When the fan is running at high speed, a lot of heat gets into the downstream area of the evaporator, resulting in a higher evaporation temperature with the same refrigerant throughput. Therefore, the Control circuit to maintain at a given temperature, a high relative humidity in the storage chamber, specify a higher speed of the fan than when a low humidity is set.

The invention further relates to a method for estimating the relative humidity in a refrigeration appliance, in particular a refrigeration appliance as described above, with the steps

a) measuring the temperature of the storage chamber,

b) measuring an evaporation temperature of the evaporator,

c) Calculating the relative humidity of air at the temperature of the storage chamber, the absolute moisture content of which is the same as that of water vapor-saturated air at the evaporation temperature.

The relative humidity calculated in this way can be displayed as an estimated value for the relative humidity in the storage chamber of the refrigerating appliance on a display instrument of the refrigerating appliance.

Another subject of the invention is a method for operating a refrigeration device, in particular a refrigeration device as described above, with the steps

a ^' ) setting a target temperature of a storage chamber,

b ^' ) setting a desired air humidity of the storage chamber,

c ^' ) setting an evaporation temperature of the evaporator so that the absolute moisture content of water vapor-saturated air at the evaporation temperature is the same as that of air with the target air humidity at the target temperature. Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. Show it:

Fig. 1 is a block diagram of a refrigerator according to the invention;

Fig. 2 is a schematic cross-section through part of the housing of

Refrigeration unit; and Fig. 3 is a diagram of the relationship between evaporation temperature and relative humidity in the vegetable compartment of the refrigerator.

Fig. 1 shows a block diagram of a household refrigerator with a plurality of storage chambers 1, 2, 3 which are cooled by a respective evaporator 4, 5 and 6 respectively. The evaporators 4, 5, 6 are connected to each other in series in a refrigerant circuit. In Fig. 1, three storage chambers and evaporators are shown, but the principle of the invention explained below is applicable to refrigerators with any number of storage chambers including a single. To a suction port of the last, 6, the series-connected evaporator, a variable speed compressor 7 is connected. A control circuit 8 controls the speed of the compressor 7 on the basis of measured by means of temperature sensors 9 to 1 1 in the storage chambers 1, 2, 3 temperatures to a value at which the power of the compressor 7 just enough to the cooling needs of the storage chambers 1 to 3 cover. In the simplest case, such a regulation can be based on the fact that when the temperature in one of the storage chambers 1, 2, 3 leaves a set interval, the compressor speed is increased and, when the interval is left, this speed is decremented. The compressed in the compressor 7 and thereby adiabatically heated refrigerant releases its heat via a condenser 12 to the environment and passes from there back to the evaporators 4, 5, 6.

Each evaporator is preceded by a controllable by the control circuit 8 throttle valve 13, 14 and 15 in series. The series-connected throttle valves 13, 14, 15 form a flow resistance, which sets the mass flow rate of the refrigerant circuit. How the flow resistance is distributed to the individual throttle valves 13, 14, 15 is variable, ie if one of the throttle valves is narrowed, another can simultaneously be expanded so that the mass flow rate remains unchanged. For example, by reducing the flow resistance of the throttle valve 13 and simultaneously increasing the flow resistance of the throttle valve 14, it is possible to increase the pressure and thus the vaporization temperature in the evaporator 4 increase, without this on pressure and temperature in the downstream evaporators 5, 6 effects.

The relationship between opening cross-sections, which are to be adjusted at the valves 13, 14 in order to vary the pressure in the evaporator 4 and at the same time to keep the pressures in the evaporators 5, 6 constant, according to an embodiment of the invention in the control circuit 8 preprogrammed. According to a second embodiment, after an adjustment of the throttle valve 13, the throttle valve 14 is adjusted so that a characterized by speed and electrical power consumption of the compressor 7 is restored and kept constant in this way the mass flow rate of the refrigerant circuit.

Fig. 2 shows a schematic cross section through part of the housing of the refrigerator with the storage chamber l. The storage chamber 1 is shown here as the lowest storage chamber of the housing, but can also be located in other positions. Due to the position of the storage chamber 1 in the lower region of the housing, near a floor, a drawer 16 can facilitate access to refrigerated goods stored therein. Unlike conventional refrigerators, the drawer 16 is not closed and does not need to be so to protect its contents from drying out. In order to protect the refrigerated goods from contact with waterlogging, instead of the pull-out box 16, even a grid or grid may be advantageous as a support for the refrigerated goods.

The evaporator 4 is housed as a NoFrost evaporator in an evaporator chamber 18 separated from the rest of the storage chamber 1 by a wall 17. It also includes a fan 19 which is operable by the variable speed control circuit 8 to draw air through the evaporator 4 and to guide the air thus cooled back into the storage chamber 1 and around the drawer 16 via a back wall duct 20. The temperature sensor 9 is mounted at a location of the storage chamber 1, where it is protected from direct flow with exiting the rear wall duct 20 air, here, for example, in a side wall of the refrigerator housing, a flank of the pull-out box 16 opposite. Another temperature sensor 21 is provided in the evaporator chamber 18, it may be mounted directly on the evaporator 4 itself; Fig. 2 shows it downstream of the evaporator 4 at a position where it is directly exposed to the flow of cooled in the evaporator 4 to the evaporation temperature air.

Under normal operating conditions, the evaporator 4 is always a few ° C colder than the air in the storage chamber l. When this air cools below its dew point as it passes through the evaporator 4, a portion of the entrained moisture condenses on the evaporator 4, and the air exiting the evaporator 4 has a relative humidity of 100%. When this air returns to the storage chamber 1 and heats up to the temperature prevailing there, its relative humidity accordingly decreases according to the formula

aTD aT

r = 100-10 * ⁺ ™ ^~ M, (1) where T is the temperature measured by the temperature sensor 9 air temperature in the storage chamber l and TD measured by the temperature sensor 21 evaporation temperature, and the constants a, b for depending on the nature of the phase transition of the most Evaporator 4 takes place, may have different values. At an evaporation temperature above 0 ° C, with a phase transition from steam to water, a = 7.5, b = 237.3, at an evaporation temperature below 0 ° C and a phase transition from steam to ice, the values a = 9, 5 and b = 265.5. To use the storage chamber 1 as a vegetable compartment, an evaporation temperature> 0 ° C is sufficient.

A display instrument 22, on which the control circuit 8 outputs the estimated value of the air humidity in the storage chamber 1 calculated according to the above formula (1), can be arranged on the outside of the housing of the appliance, as shown in the figure, or it can be inside, adjacent to the storage chamber 1 to be mounted at a location where it is visible only after opening the door 23.

Obviously, the above formula is not only suitable for estimating the air humidity in the storage chamber 1, knowing the measured values of the temperature sensors 9, 21; Conversely, for a given target temperature of the storage chamber 1 and set by a user to a control element 24 desired air humidity of the Storage chamber l a temperature can be determined, which, if measured by the sensor 21, would give the desired humidity in the storage chamber 1. Fig. 3 shows schematically the relationship between evaporation temperature TD, storage chamber temperature T and relative humidity r. If the evaporation temperature TD were equal to the compartment temperature T, condensation would not occur at the evaporator 4, the storage chamber 1 would thus be deprived of moisture and the humidity r could reach a value of 100%. Since the evaporator 4 in order to cool the chamber 1, must be colder than this, in practice, the case occurs that TD is less than T and an air humidity r of less than 100% is achieved. In practice, the evaporation temperature TD is always a few ° C lower than the compartment temperature T, for example, at a set temperature of the storage chamber of + 3 ° C, the evaporator 4 may be controlled to a temperature TD of +1 ° C, then the dehumidification The air at the evaporator 4 minimal, and the relative humidity r, which is set in the storage chamber l, is just below 100%. At a lower evaporation temperature TD of, for example, -5 ° C significantly more moisture is deposited on the evaporator 4, so that sets in the storage chamber 1, a lower relative humidity r. Thus, based on the measured values of the temperature sensors 9, 21, the control circuit 8 is able to produce a relative humidity in the storage chamber 1 specified by the user on the operating element 24. As a result, no lid on the pull-out box 16 is required to keep the humidity high inside the pull-out box. Therefore, with the refrigeration appliance according to the invention against evaporation sensitive refrigerated goods can be kept fresh for a long time without a lid would impede access to the refrigerated goods.

REFERENCE NUMBERS

1 storage room

2 storage room

3 storage chamber

4 evaporators

5 evaporators

6 evaporator

7 compressors

8 control circuit

9 temperature sensor

10 temperature sensor

1 1 temperature sensor

12 liquefier

13 throttle valve

14 throttle valve

15 throttle valve

16 pull-out box

17 wall

18 evaporator chamber

19 fans

20 back wall channel

21 temperature sensor

22 indicating instrument

23 door

24 control element

Claims

Refrigerating appliance with a storage chamber (1) and an evaporator (4) which cools the storage chamber (1), characterized in that a processing unit (8) is set up for a given temperature (T) of the storage chamber (1) values of the air humidity (r) in the storage chamber (1) and an evaporation temperature (TD) of the evaporator (4) assuming that the absolute water vapor content of the air of the storage chamber (1) is the same as that of water vapor saturated air at the evaporation temperature (TD).

Refrigeration appliance according to claim 1, characterized in that sensors (9, 21) for measuring the temperature (T) of the storage chamber (1) and the evaporation temperature (TD) are provided, that the processing unit (8) is arranged, when assigned to a given Value of the evaporation temperature (TD) to estimate the humidity (r), and the processing unit (8) is connected to a meter (22) to display the estimated humidity (r).

Refrigerating appliance according to claim 1, characterized in that an operating element (24) for adjusting the air humidity (r) in the storage chamber (1) is provided as a desired size, that the processing unit (8) with the operating element (24) is connected and set up during Assign to a given value of the humidity (r) to estimate a target value of the evaporation temperature (TD) and to match the real evaporating temperature of the evaporator (4) to the target value.

Refrigerating appliance according to claim 3, characterized in that the evaporation temperature (TD) of the evaporator (4) is controllable via the mass flow rate of a compressor (7) or over the opening cross-section of at least one with the evaporator (4) connected in series throttle valve (13, 14, 15).

5. Refrigerating appliance according to one of the preceding claims, characterized in that at a given temperature (T) of the storage chamber (1) the evaporation temperature (TD) at a high given value of the humidity (r) is higher than at a low given value.

6. Refrigerating appliance according to one of the preceding claims, characterized in that a fan (19) is provided with controllable throughput to circulate air between the evaporator (4) and the storage chamber (1).

7. Refrigerating appliance according to claim 6, characterized in that it is a NoFrost device.

8. Refrigerating appliance according to claim 6 or 7, characterized in that at a given temperature (T) of the storage chamber (1) the throughput of the fan (19) at a high given value of the humidity (r) is higher than at a low given value of the humidity ( r).

9. A method for estimating the relative humidity (r) in a refrigeration appliance, in particular a domestic refrigeration appliance, with a storage chamber (1) and a storage chamber (1) cooling evaporator (4), comprising the steps of: a) measuring the temperature (T) the storage chamber (1), b) measuring an evaporation temperature (TD) of the evaporator (4); c) calculating the relative humidity (r) of air at the temperature (T) of the storage chamber (1), the absolute moisture content of which is the same as that of water vapor saturated air at the evaporation temperature (TD).

10. A method for operating a refrigerating appliance, in particular a household refrigerating appliance, with a storage chamber (1) and a storage chamber (1) cooling evaporator (4), with the steps: a ') setting a target temperature (T) of the storage chamber (1), b ') setting a desired air humidity (r) of the storage chamber (1); c ') setting an evaporation temperature (TD) of the heat exchanger (25) so that the absolute moisture content of water vapor-saturated air at the evaporation temperature (TD) is the same as that of air with the target humidity (r) at the set temperature (T).