Patent Application
20220404071
The following invention relates to a refrigeration appliance, in particular a household refrigeration appliance, with at least one compartment which can be kept at an operating temperature below or above the ambient temperature according to a user's choice, in order to cool food, for example, or keep it warm for imminent consumption.
This variability of the operating temperature is achieved in a known refrigeration appliance of the applicant by a condenser, a first controllable choke point, a heat exchanger of the variable compartment, a second controllable choke point and a first evaporator of a cooled compartment being connected in series in a refrigerant circuit between an outlet of a compressor. During cooling operation of the variable compartment, the pressure drop at the first controllable choke point high, meaning that condensation only takes place in the condenser and the heat exchanger of the variable compartment also works as an evaporator; during heating operation, the pressure drop substantially takes place at the second choke point, meaning that refrigerant also condenses in the heat exchanger and in doing so releases heat. In order to ensure that sufficient heat reaches the heat exchanger, the condenser undergoes forced ventilation, and the power of a fan of the condenser may be reduced compared to cooling operation, in order to control the amount of refrigerant vapor that reaches the heat exchanger, and therefore to control the heating power of the heat exchanger.
Liquid refrigerant that accrues in the condenser during the heating operation should be kept away from the heat exchanger; for this reason, the conventional refrigeration appliance provides a branching point designed as a separator downstream of the condenser, which separates off the liquid refrigerant in order to use it in a second evaporator arranged in parallel with the heat exchanger.
A line, which supplies the liquid refrigerant to the second evaporator, together with a suction line, which leads from an outlet of the first evaporator to an inlet of the compressor, forms an internal heat exchanger in which the liquid refrigerant in thermal contact with the drawn-in refrigerant vapor cools down. If, as a result of heating operation of the variable compartment, the mass flow rate of the liquid refrigerant is too low, then it may occur that the temperature of the liquid refrigerant lies below its evaporation temperature when reaching the second evaporator and no evaporation takes place at least in part of the second evaporator; in addition, the temperature of the refrigerant vapor when reaching the compressor may still be so low that water vapor condenses on the suction line, which not only impairs the efficiency of the refrigeration, but also may lead to electrical problems and corrosion.
There is therefore a demand for a refrigeration appliance with at least one compartment that can be used in heating or cooling operation, in which the danger of condensation is reduced, and the degree of efficiency is improved.
In order to meet this demand, it is provided that on a refrigeration appliance, in particular household refrigeration appliance, with a compressor, a condenser, at least a first evaporator, a suction line running from the first evaporator to the compressor, at least one heat exchanger that can be switched between condenser and evaporator operation and with a valve arrangement for switching the heat exchanger between an evaporator operating state, in which an inlet of the switchable heat exchanger is connected to the condenser via a first choke point and an outlet of the switchable heat exchanger is connected to the evaporator, and a condenser operating state, in which the outlet of the switchable heat exchanger is connected to the evaporator via a second choke point, the switchable heat exchanger is assigned a first supply line for the supply of refrigerant in the evaporator operating state and a second supply line, which is separate from the first supply line, for the supply of refrigerant in the condenser operating state, and that only the first supply line is connected to the suction line to form an internal heat exchanger.
A precooling of the refrigerant reaching the switchable heat exchanger by way of the internal heat exchanger can thus remain restricted to the case of the evaporator operating state, while in the case of the condenser operating state a liquefaction of the refrigerant remains excluded before reaching the switchable heat exchanger.
In order to be able to vary the pressure drop between the switchable heat exchanger and the first evaporator according to the evaporator and condenser operating state to a great extent, a controlled expansion valve is preferably provided as a second choke point between the two.
In order to avoid a loss of heating power that can be used at the switchable evaporator by way of heat emission via the condenser, it is possible for the switchable evaporator to be connected in parallel with the condenser in the condenser operating state. Thus, refrigerant can be supplied to the switchable evaporator immediately after leaving the compressor, without having the opportunity to emit heat via the condenser.
A frame heater may be connected upstream of the condenser and the switchable heat exchanger together, or it may be arranged in series with the condenser, in parallel with the switchable heat exchanger.
A shut-off valve should be provided at the first supply line in order to enable a blocking of the first supply line in the condenser operating state.
Preferably, the refrigeration appliance comprises at least two switchable heat exchangers, which can be switched between evaporator operating state and condenser operating state independently of one another. If these are assigned to compartments of the refrigeration appliance with different sizes in each case, a user can choose between various volumes of the region that can be used in the condenser operating state.
Preferably, the volume of one of these compartments amounts to between 150% and 250% of the volume of the other.
In order to control the supplying of the switchable evaporator, the valve arrangement may comprise a directional valve, which in the evaporator operating state is closed and in the condenser operating state of at least one of the switchable heat exchangers connects the inlet of the heat exchanger in question to an outlet of the compressor, at least for a time.
Furthermore—and preferably by means of said directional valve—it can be possible for the valve arrangement to be switched in a clocked manner between a first open position, in which it connects an outlet of the compressor to the inlet of the first heat exchanger, and a second open position, in which it connects the outlet of the compressor to the inlet of the second heat exchanger. A clocked switching is understood here to mean a periodic switching, wherein the period is short enough to enable condensation in both switchable heat exchangers at the same time.
A second evaporator may be connected in series upstream of the first evaporator and connected in parallel with the at least one switchable heat exchanger, in order to be able to cool another compartment at the same time as the operation of the at least one switchable heat exchanger in the condenser operating state.
If the first evaporator and the second evaporator are connected via a third choke point, the temperature of the second evaporator may be set higher than that of the first, in order to keep the compartments of the two evaporators at different operating temperatures. Typically, in this manner a normal refrigeration compartment and a freezer compartment can be implemented; other combinations are of course also possible, such as a normal refrigeration compartment and cold storage compartment or cold storage compartment and freezer compartment.
A connection line between the first evaporator and the second evaporator may be connected to the suction pipe to form a section of the internal heat exchanger, in particular this section may connect immediately to an outlet of the first evaporator, in order to cause a first heating of the refrigerant vapor circulating in the suction line, before it reaches a second section of the internal heat exchanger, in which the heat exchange with the first supply line takes place.
In order to be able to adapt the temperature difference between the compartments of the first and the second evaporator to demand, the third choke point also preferably comprises a controlled expansion valve.
Further features and advantages of the invention will emerge from the description of exemplary embodiments provided below, with reference to the attached drawing.
In a thermally insulating housing, the refrigeration appliance in
A refrigerant line 7, which starts from an outlet 5 of a compressor 6, first reaches a frame heater 9 and a condenser 10 via a branching point 8. A fan 26 may be assigned to the condenser 10 in order to control its power. At a further branching point 11 downstream of the condenser 10, the refrigerant line 7 branches off into three branches 12a-c. In each branch 12a-c, the following follow one another: a valve 13a-c, a supply line 14a-c, which may be embodied as a capillary, a heat exchanger 15a, b or an evaporator 15c and a controlled expansion valve 16a-c. The heat exchangers 15a, b are each in thermal contact with one of the compartments 3, 4; the evaporator 15c is in contact with the compartment 2. There are not necessarily structural differences between the evaporator 15c and the heat exchangers 15a, b; both may be identical or merely different from one another in terms of their dimensions. Typically, the heat exchangers 15a, b and the evaporator 15c are embodied as finned heat exchangers of a per se known construction, in which in each case a large number of mutually parallel fins are merged to form a block, the refrigerant line 7 crosses the fins in a meandering manner and air circulates in the intermediate spaces between the fins, and each finned heat exchanger is assigned a fan 17a-c, which controls the intensity of the air circulation and therefore the thermal power exchanged with the compartment 2, 3 or 4 assigned in each case.
Downstream of the expansion valves 16a-c, the three branches 12a-c merge at a junction 18. The junction 18 may lie upstream of an evaporator 19 that cools the compartment 1; preferably, it is located in the evaporator 19 itself, i.e., the evaporator 19 possesses an inlet for each branch 12a-c. In the same way as the fans 17a-c, the evaporator 19 is also assigned a fan 27.
Starting from an outlet of the evaporator 19, a suction line 20 runs to an inlet 21 of the compressor 6. The suction line 20, together with a connection line 22 of the branch 12c lying downstream of the evaporator 15c as well as with the supply lines 14a-c, forms an internal heat exchanger 23, in which the refrigerant vapor circulating in the suction line 20 is first heated in thermal contact with the connection line 22 and subsequently in thermal contact with the supply lines 14a-c. For this purpose, the connection line 22 and the supply lines 14a-c may be fastened to the surface of the suction line 20 or guided in the interior thereof.
An inlet of a directional valve 24 is connected to the branching point 8. The directional valve 24 has an outlet in each case, which is connected to the inlet of the heat exchanger 15a or 15b via a supply line 25a or 25b in each case, and can be switched between the closed position, a position open toward the heat exchanger 15a and a position open toward the heat exchanger 15b.
With the construction described above, a large number of operating states can be realized:
In a first operating state, the position open toward the heat exchanger 15a and the closed position of the directional valve 24 alternate with one another, the valve 13a is closed, and the expansion valve 16a is controlled, in order to maintain a high-pressure difference between the heat exchanger 15a and the evaporator 19. Thus, in each open phase of the directional valve 24, warm, dense refrigerant from the compressor 6 is applied to the heat exchanger 15a, and the condensation taking place in the heat exchanger 15a heats the compartment 3. This means that the first operating state is a condenser operating state of the heat exchanger 15a.
In this context, refrigerant liquefied in the heat exchanger 15a reaches the evaporator 19 via the expansion valve 16a, evaporates again at the evaporator 19 and thus cools the compartment 1.
In each closed phase of the directional valve 24, dense refrigerant vapor reaches the condenser 10, where it condenses. The liquid refrigerant obtained in this way is distributed via the valves 13b, 13c to the supply lines 14b, 14c or the heat exchanger 15b and the evaporator 15c, meaning that evaporation takes place there and the compartments 2, 4 are cooled, i.e. the first operating state is an evaporator operating state for the heat exchanger 15b. Liquid refrigerant not consumed in the heat exchanger 15b or evaporator 15c reaches the evaporator 19 via one of the expansion valves 16b, 16c, thus contributing to the cooling of the compartment 1.
The level of the heating power (or its operating temperature) released in compartment 3 is determined on the one hand by the duty factor of the position of the valve 13a in which it is open toward the heat exchanger 15a, and on the other hand by the rotational speed of the fan 17a; the slower this runs, the slower the condensation, and the less refrigerant vapor can flow into the heat exchanger 15a, despite the open valve 13a, and the more refrigerant vapor therefore has to take the path via the condenser 10.
The mass flow rate via the compressor 10 is therefore variable over time, and with it also the pressure drop at the supply lines 14b, 14c. In order to still be able to keep the heat exchanger 15b and the evaporator 15c at a desired evaporation pressure, it is recommended to use controlled expansion valves as valves 13a-c, which are not only able to shut off their branch 12a-c on demand, but also maintain a predefined pressure difference in the open state.
It is also conceivable, however, to tolerate fluctuations in the evaporation pressure in heat exchanger 15b and evaporator 15c associated with the variable mass flow rate and to keep an operating temperature of the compartments 2, 4 constant by reducing the rotational speed of the fans 17b, c when the evaporation temperature drops or increasing it when the evaporation temperature rises.
Thus, in the first operating state, different operating temperatures below the ambient temperature can be maintained in the compartments 1, 2, 4, wherein the operating temperature of the compartment 2 may be higher or lower than that of the compartment 4. Both the refrigerant flowing toward the evaporator 15c and flowing away from it run through the internal heat exchanger 23; likewise, the refrigerant on the way to the heat exchanger 15b, meaning that all refrigerant, the heat of which is not needed to heat a compartment, runs through the internal heat exchanger 23.
The same applies for a second operating state, in which the position open toward the heat exchanger 15b and the closed position of the directional valve 24 alternate with one another and the valve 13b is closed, meaning that the compartment 4 is heated and the compartment 3 is cooled, i.e., the second operating state is an evaporator operating state for the heat exchanger 15a and a condenser operating state for the heat exchanger 15b.
The compartments 3, 4 have different sizes, thus a user can make the selection between the first and the second operating state on the basis of the space requirement of the item to be kept warm. This means that the volume of the compartment 3 may amount to between 150 and 250% of the volume of the compartment 4, or vice versa.
In a third operating state, the position open toward the heat exchanger 15a, the position open toward the heat exchanger 15b and the closed position of the directional valve 24 alternate with one another. Both compartments 2, 3 are heated, i.e., both heat exchangers 15a, 15b are in the condenser operating state. As both valves 13a, 13b are closed, no heat exchange takes place via the supply lines 14a, 14b in the internal heat exchanger 23; only the flow running via the evaporator 15c is available for the preheating of the drawn-in refrigerant. Via the duty factors of the phases open toward the heat exchanger 15a or toward the heat exchanger 15b, it is possible for the heating power allotted to each compartment 3, 4 to be controlled and for different operating temperatures to be set for the two compartments 3, 4, if desired.
In a fourth operating state, the directional valve 24 is permanently in the closed position. The valves 13a, 13b are open, the heat exchangers 15a, 15b are in the evaporator operating state and cool the compartments 3, 4. Refrigerant on the way to the heat exchangers 15a, 15b runs through the supply lines 14a, 14b and thus also the internal heat exchanger 23.
Thus, on the one hand, heat losses and condensation of the refrigerant before reaching the heat exchanger 15a or 15b is avoided when it works in the condenser operating mode; on the other hand, a higher degree of efficiency is achieved in the evaporator operating mode.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019213220.0 | Sep 2019 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/073179 | 8/19/2020 | WO |
