CN107810375B

CN107810375B - Refrigeration device with air humidity monitoring

Info

Publication number: CN107810375B
Application number: CN201680037413.4A
Authority: CN
Inventors: N·利恩戈德; H·科兹勒; A·恩斯特勒
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2015-06-26
Filing date: 2016-06-02
Publication date: 2020-08-14
Anticipated expiration: 2036-06-02
Also published as: DE102015211960A1; US20180187968A1; EP3314181A1; WO2016206938A1; CN107810375A

Abstract

In the context of a refrigeration appliance having a storage compartment (1) and an evaporator (4) cooling the storage compartment (1), a processing unit (8) is provided to mutually assign values of air humidity (r) in the storage compartment (1) and evaporation Temperature (TD) of the evaporator (4) at a given temperature (T) of the storage compartment (1) on the assumption that: the absolute water vapour content of the air of the storage chamber (1) is assumed to be the same as the absolute water vapour content of the air saturated with water vapour at the evaporation Temperature (TD). This assignment makes it possible, on the one hand, to estimate the relative air humidity in the storage compartment (1) on the basis of the temperature and, on the other hand, to control the air output Temperature (TD) at a constant temperature (T) in the storage compartment (1) in order to influence the air humidity (r) in the storage compartment (1).

Description

Refrigeration device with air humidity monitoring

Technical Field

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

Background

The relative air humidity in the storage compartment of a refrigeration appliance is of great importance for the shelf life of the food in the storage compartment. Particularly for storing fresh vegetables, it is desirable to have a high level of air humidity. In refrigeration appliances in which air circulates between a storage compartment and a heat exchanger (commonly referred to as frost-free refrigeration appliances), such a high level of air humidity is difficult to maintain because: when the air is cooled on the surface of the heat exchanger to below its dew point, it loses moisture on the surface of the heat exchanger, which has to be conducted out of the refrigeration appliance and removed. This water loss can cause rapid wilting of the vegetables.

In order to enable long-term storage of vegetables, vegetable compartments have been developed which comprise a container which can be closed with a lid. When the container is sealed, moisture released from the vegetables contained therein cannot escape, while the container can be cooled by cold air circulating on its outer surface. A limited exchange of air between the interior of the container and its surroundings is possible through an adjustable opening in the container, so that different air humidity values can be set in the container based on the size of the opening. Measuring this air humidity and displaying it on the outside of the refrigerator so that it is visible to the user is difficult, because the air humidity sensor has to be positioned in the container and its output signal has to be transmitted from the container, which can be moved in the refrigerator, to the display device of the refrigerator without restricting the freedom of movement of the container.

Thus, the air humidity is typically not measured and the user typically does not know the actual level of air humidity within the container. The user thus essentially only uses his/her own observations to determine the degree of opening of the container that is appropriate for the particular cooled item. However, this observation is complicated because the air humidity inside the container is not only a function of the size of the opening, but is also indirectly influenced by the environmental conditions during the evaporator operation time. This makes it difficult for the user to identify the relationship between the degree of opening of the container and the shelf life of the cooled item.

Disclosure of Invention

It is an object of the present invention to provide a refrigeration appliance and an operating method for a refrigeration appliance which enable a user to more effectively monitor the air humidity in the refrigeration appliance.

The object is achieved on the one hand by a refrigeration appliance having a storage chamber and an evaporator which cools the storage chamber, wherein the processing unit is designed to mutually assign a value of the air humidity in the storage chamber and a value of the evaporation temperature of the evaporator at a defined temperature of the storage chamber on the basis of the following assumptions: it is assumed that the absolute water vapor content of the air in the storage chamber is the same as that of the air saturated with water vapor at the evaporation temperature (i.e., air having a relative humidity of 100%).

This assignment can be made in different directions and can be used for different purposes. In a first embodiment, the sensors are arranged to measure the temperature and the evaporation temperature of the storage compartment, and the processing unit is designed, at the time of attachment, to use the value of the defined evaporation temperature to estimate for this value the corresponding air humidity at the temperature of the storage compartment and to display the air humidity thus estimated on the display device. This enables the user to obtain quantitative results regarding the air humidity in the storage compartment without the need to provide an air humidity sensor directly in the storage compartment, which is problematic especially when the storage compartment is configured as a drawer box (which is often provided in the case of vegetable compartments).

More important than knowing the air humidity in the storage compartment is the ability of the user to specifically set the air humidity in the storage compartment. Thus, in a second embodiment, the assignment is performed in the opposite direction. For this purpose, an operating element is provided to set the air humidity in the storage chamber as a setpoint variable, and the processing unit is connected to the operating element and is designed to estimate, at the time of the assignment, a target value for the evaporation temperature for a defined setpoint value of the air humidity set at the operating element and to bring the actual evaporation temperature of the evaporator into agreement with the target value. When the air in the storage chamber, which is in contact with the evaporator, is cooled to the evaporation temperature, only an amount of water vapor corresponding to 100% of the relative air humidity at the evaporation temperature can be retained in the air. By choosing a suitable evaporation temperature, it is possible to set a desired relative air humidity of the same air after heating to the temperature of the storage compartment.

To allow control of the evaporation temperature, the evaporator may be part of a refrigerant circuit, wherein the flow rate of the compressor may be controlled to vary the pressure in the evaporator.

Alternatively or additionally, the evaporation temperature can also be influenced by controlling the opening cross section of at least one throttle valve connected in series upstream or downstream of the evaporator.

When the temperature of the storage chamber is constant, if a high level of air humidity is to be maintained in the storage chamber, the evaporation temperature must be set higher than the evaporation temperature for a low air humidity value.

Particularly, but not exclusively, in the case of a frost-free type refrigeration appliance, where the evaporator chamber is spaced from the storage chamber, a fan with a controllable flow rate may be provided to circulate air between the evaporator and the storage chamber.

The faster the fan is operated, the smaller the temperature difference between the upstream side and the downstream side of the evaporator. When it is running slowly, the heat input at the downstream end of the evaporator is low and a low evaporation temperature can be established at this downstream end, which removes a large amount of moisture from the air flowing through; when the fan is running faster, a large amount of heat reaches the downstream area of the evaporator, so that a higher evaporation temperature results in a constant refrigerant flow rate. Thus, the control circuit may predefine a higher fan speed than when a low level of air humidity is set to maintain a high level of relative air humidity in the storage compartment at a defined temperature.

The object of the present invention is also to provide a method for estimating the relative air humidity in a refrigeration appliance, in particular a refrigeration appliance as described above, having the following steps:

a) the temperature of the storage compartment is measured and,

b) the evaporation temperature of the evaporator is measured and,

c) the relative air humidity at the temperature of the storage chamber is calculated, and the absolute moisture content of the air at the temperature of the storage chamber is the same as the absolute moisture content of the air saturated with water vapor at the evaporation temperature.

The relative humidity thus calculated can be displayed on a display device of the refrigeration appliance as an estimate of the relative air humidity in the storage compartment of the refrigeration appliance.

Another object of the present invention is to provide a method for operating a refrigeration appliance, in particular a refrigeration appliance as described above, having the following steps:

a') determining the nominal temperature of the storage compartment,

b') determining the nominal air humidity of the storage compartment,

c') setting the evaporation temperature of the evaporator such that the absolute moisture content of the air saturated with water vapour at the evaporation temperature is the same as the absolute moisture content of the air having said nominal air humidity at said nominal temperature.

Drawings

Other features and advantages of the present invention will appear from the following description of exemplary embodiments with reference to the accompanying drawings, in which:

fig. 1 shows a block diagram of a refrigeration appliance of the invention;

figure 2 shows a schematic cross-sectional view through a portion of a housing of a refrigeration appliance; and

fig. 3 shows a diagram of the relationship between the evaporation temperature and the relative air humidity in the vegetable compartment of a refrigeration device.

Detailed Description

Fig. 1 shows a block diagram of a refrigeration appliance having a plurality of

storage chambers

1, 2, 3, each of which is cooled by an

evaporator

4, 5 or 6. The

evaporators

4, 5, 6 are connected to each other in series in the refrigerant circuit. Fig. 1 shows three storage chambers and an evaporator, but the principles of the invention set forth below can also be applied to refrigeration appliances having any number of storage chambers, including only one storage chamber.

The variable speed compressor 7 is connected to the suction inlet connection of the last evaporator 6 of the series-connected evaporators. The control circuit 8 controls the speed of the compressor 7 to such a value based on the temperatures measured in the

storage chambers

1, 2, 3 by the temperature sensors 9 to 11: at this value, the output of the compressor 7 is sufficient to meet the cooling requirements of the storage chambers 1 to 3. In the simplest case, this adjustment can be based on the following: the compressor speed is increased when the temperature in one of the

storage chambers

1, 2, 3 deviates from the nominal interval in the upward direction and the speed is decreased when the temperature in one of the

storage chambers

1, 2, 3 deviates from the interval in the downward direction.

The refrigerant, which has been compressed in the compressor 7 and is adiabatically warmed in the process, outputs its heat to the surroundings via the condenser 12 and from there back to the

evaporators

4, 5, 6.

Upstream of each evaporator connected in series is a

throttle valve

13, 14 or 15 which can be controlled by the control circuit 8. The successively connected

throttles

13, 14, 15 form a flow resistance, which determines the mass flow rate of the refrigerant circuit. The way in which the flow resistance is assigned to the

individual throttles

13, 14, 15 is variable, in other words when one of the throttles is narrowed, the other can be widened, so that the mass flow rate remains constant. Thus, the pressure in the evaporator 4 and thus the evaporation temperature in the evaporator 4 can be increased, for example, by reducing the flow resistance of the throttle valve 13 and at the same time increasing the flow resistance of the throttle valve 14, without affecting the pressure and temperature in the downstream evaporators 5, 6.

According to one embodiment of the invention, the relationship between the opening cross sections set at the

valves

13, 14 for varying the pressure in the evaporator 4 while keeping the pressure in the evaporators 5, 6 constant is preprogrammed in the control circuit 8. In the second embodiment, after the throttle 13 has been adjusted, the throttle 14 is set to restore the operating point of the compressor 7, characterized by the speed and the power consumption, ensuring that the mass flow rate of the refrigerant circuit remains constant.

Fig. 2 shows a schematic cross-sectional view of that part of the housing of the refrigeration appliance which has the storage compartment 1. The storage compartment 1 is here shown as the lowest storage compartment of the housing, but it may also be located at other positions. Since the storage compartment 1 is located in the lower region of the housing near the base, the drawer 16 facilitates access to the cooled items stored in the drawer 16. Unlike conventional refrigeration appliances, the drawer 16 is not closed and does not need to be closed in order to protect its contents from drying out. In order to protect the cooled items from contact with the collected water, a mesh or grid may advantageously be used as a substrate for the cooled items instead of the drawer box 16.

The evaporator 4 is a frost-free evaporator housed in an evaporator chamber 18, said evaporator chamber 18 being separated from the rest of the storage chamber 1 by a wall 17. Also included is a fan 19 which can be operated at variable speed by the control circuit 8 to draw air through the evaporator 4 and direct the air thus cooled through the rear wall channel 20 back to the storage compartment 1 and around the drawer box 16.

The temperature sensor 9 is located at a point of the storage compartment 1 where it is protected from the direct flow of air flowing out of the rear wall channel 20, in this case for example in a side wall of the refrigeration appliance housing which is arranged opposite to the side of the drawer box 16.

A further temperature sensor 21 is provided in the evaporator chamber 18 and may be located directly in the evaporator 4 itself; fig. 2 shows that the further temperature sensor 21 is located downstream of the evaporator 4 at the following points: at this point, the further temperature sensor is directly exposed to the air flow cooled to the evaporation temperature in the evaporator 4.

Under normal operating conditions, the evaporator is always a few degrees celsius lower than the air in the storage compartment 1. When the air cools below its dew point as it passes through the evaporator 4, part of the water carried by the air condenses on the evaporator 4 and the relative humidity of the air leaving the evaporator 4 is 100%. When this air is returned to the storage chamber 1 and heated to the temperature in the storage chamber 1, its relative humidity decreases accordingly according to the following formula:

where T is the air temperature in the storage compartment 1 measured by the temperature sensor 9, TD is the evaporation temperature measured by the temperature sensor 21, and the constants a, b may have different values according to the type of phase change occurring at the evaporator 4. At evaporation temperatures above 0 ℃, a-7.5 and b-237.3 for the phase transition from steam to water, and below 0 ℃, a-9.5 and b-265.5 for the phase transition from steam to ice. An evaporation temperature > 0 c is sufficient for the storage compartment 1 to be used as a vegetable compartment.

The control circuit 8 outputs the estimated value of the air humidity inside the storage room 1 calculated according to the above formula (1) on the display device 22, which display device 22 may be disposed on the outside of the housing of the appliance as shown in the figure or may be mounted at the following places adjacent to the inside of the storage room 1: this portion is visible only when the door 23 is open.

Obviously, the above formula is not simply applicable to estimating the humidity of the air in the storage compartment 1 knowing the values measured by the temperature sensors 9, 21; it is also possible, conversely, to determine a temperature for a defined nominal temperature of the storage compartment 1 and a nominal air humidity of the storage compartment 1 set by the user on the operating element 24, which temperature, if measured by the sensor 21, gives the desired air humidity in the storage compartment 1. Fig. 3 shows a schematic diagram of the relationship between the evaporation temperature TD, the storage chamber temperature T, and the relative humidity r. If the evaporation temperature TD is equal to the lattice temperature T, condensation does not occur at the evaporator 4, so no moisture is precipitated from the storage chamber 1, and the air humidity r can reach a value of 100%. Since the evaporator 4 has to be lower in temperature than the storage chamber 1 in order to cool the storage chamber 1, TD is smaller than T and the air humidity r is lower than 100% in practice. In practice, the evaporation temperature TD is always a few degrees celsius lower than the room temperature T, for example at a nominal temperature of the storage chamber of +3 ℃, the temperature TD of the evaporator 4 can be adjusted to +1 ℃, which means that the moisture precipitation from the air at the evaporator 4 is minimal and that the relative air humidity r established in the storage chamber 1 is slightly lower than 100%. At a lower evaporation temperature TD, for example-5 ℃, significantly more moisture is removed at the evaporator 4, thereby establishing a lower relative air humidity r in the storage chamber 1. The control circuit 8 is thus able to establish in the storage compartment 1, based on the values measured by the temperature sensors 9, 21, a relative air humidity predefined by the user at the operating element 24. Thus, no cover is required on the drawer 16 to keep the air humidity inside the drawer high. The refrigeration device according to the invention can thus keep items to be cooled which are sensitive to evaporation fresh for a long time without the need to provide a cover which obstructs access to the items to be cooled.

List of reference numerals

1 storage room

2 storage room

3 storage room

4 evaporator

5 evaporator

6 evaporator

7 compressor

8 control circuit

9 temperature sensor

10 temperature sensor

11 temperature sensor

12 condenser

13 throttle valve

14 throttle valve

15 throttle valve

16 drawing box

17 wall

18 evaporator chamber

19 blower fan

20 rear wall channel

21 temperature sensor

22 display device

23 door

24 operating element

Claims

1. A refrigeration appliance having a storage compartment (1) and an evaporator (4) cooling the storage compartment (1), characterized in that a processing unit (8) is provided to mutually assign a value of the air humidity (r) in the storage compartment (1) and a value of the evaporation Temperature (TD) of the evaporator (4) at a defined temperature (T) of the storage compartment (1) on the basis of the following assumptions: the absolute water vapour content of the air in the storage chamber (1) is assumed to be the same as the absolute water vapour content of the water vapour saturated air at the evaporation Temperature (TD).

2. The refrigerator appliance according to claim 1, characterized in that sensors (9, 21) are provided to measure the temperature (T) of the storage compartment (1) and the evaporation Temperature (TD), the processing unit (8) is designed to estimate the air humidity (r) at the time of assignment for a defined value of the evaporation Temperature (TD) and the processing unit (8) is connected to a display device (22) to display the estimated air humidity (r).

3. The refrigeration appliance according to claim 1, characterized in that an operating element (24) is provided to set the air humidity (r) in the storage compartment (1) to a nominal variable, the processing unit (8) being connected to the operating element (24), the processing unit (8) being designed to estimate a target value of the evaporation Temperature (TD) for a defined value of the air humidity (r) at the time of assignment and also to bring the actual evaporation temperature of the evaporator (4) into agreement with the target value.

4. The refrigeration appliance according to claim 3, characterized in that the evaporation Temperature (TD) of the evaporator (4) can be controlled by the mass flow rate of a compressor (7) or by the opening cross section of at least one throttle valve (13, 14, 15) connected in series to the evaporator (4).

5. The refrigeration appliance according to any of the preceding claims, characterized in that at a defined temperature (T) of the storage compartment (1), the evaporation Temperature (TD) with a higher defined value of the air humidity (r) is higher than the evaporation Temperature (TD) with a lower defined value of the air humidity (r).

6. The refrigeration appliance according to any of the claims 1 to 4, characterized in that a fan (19) with a controllable flow rate is provided to circulate air between the evaporator (4) and the storage compartment (1).

7. A refrigerator appliance as claimed in claim 6, characterized in that the refrigerator appliance is a frost-free appliance.

8. The refrigerator appliance according to claim 6, wherein the flow rate of the fan (19) is higher at a defined temperature (T) of the storage compartment (1) at a defined value of the air humidity than the flow rate of the fan (19) at a lower value of the air humidity.

9. A method for estimating the relative air humidity (r) in a refrigeration appliance having a storage compartment (1) and an evaporator (4) cooling the storage compartment (1), the method having the steps of:

a) measuring the temperature (T) of the storage chamber (1)

b) Measuring the evaporation Temperature (TD) of the evaporator (4)

c) Calculating the relative humidity (r) of the air at the temperature (T) of the storage chamber (1), wherein the absolute moisture content of the air at the temperature (T) of the storage chamber (1) is the same as the absolute moisture content of the water vapour saturated air at the evaporation Temperature (TD).

10. The method of claim 9, wherein the refrigeration appliance is a domestic refrigeration appliance.

11. A method for operating a refrigeration appliance having a storage compartment (1) and an evaporator (4) cooling the storage compartment (1), the method having the steps of:

a') determining the nominal temperature (T) of the storage chamber (1)

b') determining a nominal air humidity (r) of the storage chamber (1),

c') setting the evaporation Temperature (TD) of the heat exchanger (25) such that the absolute moisture content of the air saturated with water vapor at the evaporation Temperature (TD) is the same as the absolute moisture content of the air having the nominal air humidity (r) at the nominal temperature (T).

12. The method of claim 11, wherein the refrigeration appliance is a domestic refrigeration appliance.