CA3225649A1

CA3225649A1 - Ecological refrigeration unit cooled with outdoor air

Info

Publication number: CA3225649A1
Application number: CA3225649A
Authority: CA
Inventors: Kari Sarne
Original assignee: Allergia Ja Sisailma Apu Sarne Oy
Current assignee: Allergia Ja Sisailma Apu Sarne Oy
Priority date: 2021-08-31
Filing date: 2022-08-08
Publication date: 2023-03-09
Also published as: FI20215909A1; WO2023031505A1; FI130125B

Abstract

The object of the present disclosure is an ecological refrigeration unit (10) that is cooled with outdoor air. The energy consumption of the refrigeration unit can be decreased by utilizing colder outdoor air to maintain the storage space (12) of the refrigeration unit at a desired temperature. This can be achieved by circulating cold outdoor air in an air space (11.2) between interior space of the refrigeration unit and the insulation (11.1) of the outer housing, such that the interior space of the unit is cooled down. The operation of the unit can be intelligently controlled by means of temperature detecting sensors (15.1, 15.2, 15.3), such that the air circulation automatically starts and stops according to what is most appropriate for the refrigeration unit and the energy consumption thereof.

Description

Ecological refrigeration unit cooled with outdoor air Field of Invention The invention relates to refrigeration units, and especially to energy effi-cient refrigeration units.
Background Refrigeration units, such as refrigerators, can significantly improve the shelf life of perishable products. Nowadays, the refrigerator is a standard equipment in homes and, for example in Europe and North America, one is found in almost every home. In addition, there are refrigeration units in workplaces and institutions, and other private and public spaces where meals are served. Refrigeration units are a very significant group of appliances in terms of energy consumption, which is why signifi-cant energy savings can be achieved by improving their energy efficiency, both on an individual and societal level.
Brief Description The unit according to the invention is characterized by what is stated in the independent claims.
The energy consumption of a refrigeration unit can be decreased by uti-lizing colder outdoor air to maintain the storage space of the refrigeration unit at a desired temperature. This can be achieved by circulating cold outdoor air in an air space between the interior space of the refrigeration unit and the insulation of the outer housing so that the interior space of the unit is cooled down. The operation of the unit can be intelligently controlled by means of temperature detecting sensors, such that the air circulation automatically starts and stops according to what is most appropriate for the refrigeration unit and the energy consumption thereof. In regions with a cool climate, significant energy savings can be achieved by utilizing outdoor air. For example, in all regions of Finland, the coldness can be utilized at least during 6 months of the year and in the Northern Finland even longer. The winters are cold also in many geographical regions even further south, and there are also regions, for example in the mountains, where especially the nights are cold.

2 The outdoor temperature is lowest during winters and nights when it is both cold and dark. During the warmer seasons, when the outdoor air is too warm for cooling a refrigerator, there is on the other hand a lot of light, whereby ecological solar energy may be utilized for cooling the refrigerator.
At temperatures much below freezing, the refrigeration unit may operate completely without external energy. Due to the energy required for heating, the total societal energy demand is at its highest at freezing temperatures, and in the produc-tion thereof there is therefore a need to use all kinds of production methods (including the less environmentally friendly ones). The peak in the energy consumption can be lowered if there is no electricity demand, or only a very small demand, for refrigera-tion units during freezing temperatures.
The refrigeration unit according to the invention may be used all over the world at regions where the outdoor temperature drops below the temperature of the refrigerator for a considerable part of the year. It can be used also at locations where the nights are cold, even if the daytime temperatures would be high.
List of Figures In the following, the invention is described in detail with reference to the enclosed drawings, wherein:
Figure la and lb present an embodiment of a refrigeration unit according to the present disclosure, Figure 2 presents another embodiment of a refrigeration unit according to the present disclosure, and Figure 3 presents further another embodiment of a refrigeration unit ac-cording to the present disclosure.
Detailed Description This description describes an energy efficient refrigeration unit and a method for controlling the same. The refrigeration unit comprises a storage space arranged within a thermally insulated outer housing for cold storage of products, and a refrigeration machinery for lowering the temperature of the storage space to a temperature range defined by a minimum temperature and a maximum temperature.

3 The thermally insulated outer housing refers to an entity formed by the thermally insulated walls surrounding the storage space. The desired storage temperature de-pends on the intended use of the refrigeration unit. The refrigeration unit may, for example, be a refrigerator, or another storage space equipped with a refrigeration machinery, such as a wine storage or chiller unit. In the case of a refrigerator, the desired storage temperature range may be +2 C ¨ +6 C, for example. In order to improve the energy efficiency of the refrigeration unit, an air space is arranged within the outer housing between the storage space and the thermally insulated outer hous-ing.
The air space is a cavity or an air channel system that at least partially surrounds the storage space. Figures la and lb present an embodiment of such a refrigeration unit.
In Figure la, a simplified cross-section representation of the refrigeration unit 10 is shown in a front view. Refrigeration unit 10 can be a refrigerator, for ex-ample. Figure lb shows the same refrigeration unit 10 as presented from the side. In Figures la and lb, a storage space 12 is arranged within the outer housing 11 com-prising thermal insulation 11.1. In Figure lb, disclosing the side view, also a refriger-ation machinery 17 arranged to cool down the storage space is shown.
The storage space is surrounded by an air space 11.2. The air space 11.2 is situated between the storage space 12 and the thermal insulation 11.1 of the outer housing. The wall 12.1 between the air space 11.2 and the storage space 12 is pref-erably made of a material having high thermal conductivity, such as aluminum.
Thus, it is ensured that heat can be efficiently transferred between the storage space 12 and the air space 11.2. At the same time, because the thermal insulation 11.1 of the housing 11 is between the air space 11.2 and the air outside the housing 11 (such as indoor air), the air outside the housing 11 does not considerably heat the air within the air space 11.2. The wall between the storage space 12 and the air space 11.2 can also be formed such that it functions as a heat sink. A sufficiently thick wall can for instance function as a cooling plate heat sink. Alternatively, or additionally, the refrig-eration unit may be equipped with separate heat sinks, such as cooling plates.
The heat sinks may be cooled down, for example, during cold nights, whereby they assist in cooling the storage space 12 at other times of the day.
The refrigeration unit according to the present disclosure comprises an inlet and outlet air pipe connected to the air space within the housing to provide an

4 air circulation path within the air space. In Figures la and lb, the inlet air pipe 13 is at the bottom part of the refrigeration unit 10 and the outlet air pipe 14 is at the upper part. The air flow of the air circulation path is in Figures la and lb shown with arrows. The cold or cool outdoor air is drawn into the inlet air pipe 13 and proceeds therefrom into the air space 11.2. In the air space 11.2, the cold or cool air cools down the storage space 12 via the wall 12.1 and proceeds therefrom warmed up through the air space 11.2 into the outlet air pipe 14. From the outlet air pipe 14 the heated air is discharged to the outdoor air.
The refrigeration unit further comprises measuring means for measuring the outdoor temperature, the temperatures of the air space arranged within the hous-ing and the storage space. The measuring means may be in the form of, e.g., tem-perature sensors. There are preferably at least three sensors, such as shown in figures la and lb, for example. The first sensor 15.1 can be outside the building, or in the inlet air pipe 13 as close as possible to the outer wall, where it may detect the tern-perature of the outdoor air. A second sensor 15.2 can be in the air space of the refrigerating unit, where it detects the temperature of the air space 11.2. A
third sensor 15.3 can be inside the refrigeration unit, where it detects the temperature of the interior space 12 of the refrigeration unit.
The refrigeration unit according to the present disclosure further corn-prises air flow adjustment means arranged in connection with the inlet and/or outlet air pipe for adjusting the air circulation. These adjustment means may be imple-mented in several ways. They may be, for example, a shutter mechanism in the form of a valve or valves. One simple example of a shutter mechanism is a flap operated with an electric motor, whereby the flap can be set in two different positions (closed and open). In Figure la and lb, such flaps 16.1 and 16.2 functions as adjustment means.
The refrigeration unit further comprises control means adapted to control the refrigeration machinery and the air flow adjustment means as a response to the measured temperatures. Outdoor air is circulated in the space between the interior space of the refrigeration unit and the insulated outer housing such that the air cir-culation of the space in between can be automatically adjusted based on the outdoor temperature, the temperature of the air space in the refrigeration unit and the interior temperature. The control means may be, for example, in the form of an electrical control unit. The control unit may comprise a calculation unit (such as a processor,

5 microcontroller or programmable logic) and a memory. A program that programs the calculation unit to control the refrigeration machinery and the air flow control means may be stored in the memory. The control unit may be programmed to receive meas-urement data from the measuring means and based thereon decide how the refrig-5 eration machinery and the air flow is utilized in the cooling.
Alternatively, the refrig-eration unit is cooled only by means of an air stream conducted from the outside, only by means of the refrigerator's own refrigeration machinery, or by a combination of these. If the interior temperature of the refrigeration unit decreases to the lower limit of a desired temperature range, the cooling of the refrigeration unit will be stopped completely until the cooling is calculated to be necessary again.
The refrigeration unit is intelligently controlled by means of temperature sensors such that air is circulated when the cooling of the interior space benefits from air circulation. In general, air is circulated when the temperature of the outdoor air is lower than the temperature of the air space. The air circulation is stopped when the temperature of the outdoor air becomes so high that circulation of air no longer facil-itates cooling of the refrigeration unit. In one embodiment, the control means of the refrigeration unit are adapted to control the refrigeration machinery and the adjust-ment means for the air flow such that the temperature of the storage space is pri-marily cooled with the air flow. When the outdoor air is too warm to keep the refrig-eration unit at a desired temperature range, the refrigeration machinery is used. The refrigeration unit can also be adjusted to simultaneously use both the air flow and the refrigeration machinery. This is convenient for example when the refrigeration unit has just been loaded with warm food products and the temperature of the storage space of the refrigeration unit has increased above a maximum temperature of the desired temperature range. It is thus important to cool down the interior space to the desired temperature as quickly as possible.
When the temperature of the outdoor air becomes so high that the air circulation does not provide an advantageous effect anymore, the air circulation is automatically stopped, and the air circulation openings are closed tightly. A
corn-pletely sealed air space provides good thermal insulation, thereby improving the ther-mal economy of the refrigeration unit.
In a refrigerator, the desired minimum temperature of the storage space is generally about +2 C, and it is important that the temperature does not become too low, thereby causing freezing. When the outdoor air is very cold, the programmed

6 refrigeration unit prevents the interior space from cooling down too much by auto-matically stopping the air circulation at a stage where the temperature decreases to a lower limit of the desired temperature range. In that case, no cooling method is used until the temperature of the storage space has increased above the minimum temperature of the temperature range, whereby the air circulation is started again.
The air circulation can be arranged in different ways. In one embodiment, gravity-assisted air circulation is utilized. Gravity-assisted air circulation may be most easily arranged when the refrigeration unit is placed against an outer wall of the building. The air is put into motion by means of gravity when outdoor air is brought into the bottom part of the refrigeration unit and the air outlet can be arranged in the upper part of the refrigeration unit. The air circulates vertically because the air that has been warmed up raises upwards. The air moves by means of gravity when the air comes from below and leaves from above and the air inlet and outlet are far enough apart and their horizontal portions are short. The refrigeration unit may fur-ther be equipped with a blower that improves the gravity-assisted ventilation.
The control means of the refrigeration unit may be defined to detect when it is beneficial to assist the gravity-assisted air circulation with a blower. The blower may be low-power, having a nominal power of, e.g., less than 2 W. The example of Figures la and lb represents an embodiment based on gravity-assisted air flow. The inlet air pipe 13 is at the bottom part of the refrigeration unit 10 and the outlet air pipe 14 is on top of the refrigeration unit 10. It can be seen from Figure lb that the refrigeration unit 10 is placed in immediate proximity to the wall 18.
If the refrigeration unit is far from the outer wall, it might be challenging to achieve a gravity-assisted air circulation. In that case the refrigeration unit may comprise a blower which provides the main part of the air flow or the air flow in its entirety. The refrigeration unit may in such embodiments not operate completely without electricity, but the electricity demand of the blower is very low.
When the air flow is produced with a blower, it is not necessary to place the inlet and outlet air pipes separately, but they can be placed close to each other, whereby the pipes can be drawn side by side or on top of each other indoors. Figure 3 presents a schematic picture of such an embodiment.
The air circulation may also be implemented utilizing the ventilation sys-tem of the building. In some embodiments of the refrigeration unit, the outlet air pipe of the refrigeration unit may for example be adapted to be connected to the exhaust

7 duct of the ventilation system of a building. The ventilation may be gravity-assisted, equipped with mechanical exhaust ventilation, or it may be fully mechanical.
In grav-ity-assisted exhaust ventilation, the exhaust duct draws air out most efficiently when the outdoor air is significantly colder than the indoor air. Thereby, the exhaust duct draws air most efficiently when the outdoor air can be used for cooling the refrigera-tion unit. In gravity-assisted exhaust ventilation, the air circulation may be improved with a low-power blower when necessary.
In buildings having mechanical exhaust ventilation or fully mechanical ventilation, the air circulation is made to function by use of an underpressure pro-duced by a machine, and a separate blower is not necessarily needed in connection with the unit.
Figure 2 presents an example of such an embodiment. Figure 2 shows a side view of a refrigerator 20 placed next to the outer wall 28. Like in Figures la and lb, air is brought from outside through the inlet pipe 23 into the bottom part of the unit 20. However, in contrast to Figures la and 2b, the air is led from the upper part of the unit to an exhaust duct 24.1 in Figure 2. When the exhaust ventilation operates mechanically, the air circulation of the refrigeration unit is functioning by means of the underpressure produced by the exhaust ventilation without the need of a blower in connection with the refrigeration unit.
When the refrigeration unit is used in connection with mechanical venti-lation, it is beneficial to keep the volume of the air space relatively small, such that the unit can be cooled down effectively with a small amount of air. Thereby variations in the air circulation have almost no effect on other indoor ventilation or heat recov-ery.
When the refrigeration unit is a refrigerator, it typically has horizontal di-mensions somewhat greater than 500 x 500 mm. When the insulation of the housing is reduced from the external dimensions, the horizontal dimensions of the air space thereby fall below 500 x 500 mm. If air is brought from outside into the lower part of the refrigerator with a pipe having a diameter of 80 mm into a 100 mm high air space, then the volume of the air space in the lower part of the refrigerator is about 25 dm3 and the height of the lower part can even be lowered in some parts of the space, whereby its volume may be estimated to about 15 dm3. At the sides of the refrigera-tor, the thickness of the air space may be, e.g., about 10 mm, whereby the air space at the sides is 10-20 dm3 in total, depending on the size of the refrigerator.
At the

8 upper part of the refrigerator, a suitable height of the air space may be around 20 mm, whereby the volume of the air space there is about 5 dm3. The total volume of the air space in a high refrigeration unit is thus about 40 dm3. If the amount of air is, e.g., 0,8 dm3/s, which means 2880 dm3/h, the amount of air is sufficient to exchange the air of the whole air space of a large refrigerator more than 60 times an hour, that is more than once every minute.
In Figure 3, the refrigeration unit 30, which may be for example a refrig-erator, comprises a storage space 32 and an outer housing 31 surrounding it.
The outer housing comprises thermal insulation 31.1 and an air space 31.2. The storage space 32 and the air space 31.2 are separated by a case formed by the walls 32.1 defining the storage space. The walls 32.1 are made from thermally conducting ma-terial. An inlet air pipe 33 and an outlet air pipe 34 are connected to the air space 31.2. The pipes 33 and 34 are next to each other in the upper part of the refrigeration device 30. The outlet air pipe 34 comprises a blower 34.1. The air space 31.2 is divided by a partitioning wall 31.3 such that the air coming from the inlet air pipe 33 needs to circulate around the storage space 32 in order to get to the outlet air pipe 34. In this way, cool air is arranged to cool down the air space 32. Like in the em-bodiments presented above, the refrigeration unit 30 comprises several temperature sensors. The first sensor 35.1 can be outdoors or in the inlet air pipe 33, the second sensor 35.2 is in the air space 31.2 and the third sensor 35.3 is in the storage space 32. The control means for the refrigeration unit are adapted to control the air flow adjustment means 36.1 and 36.2 of the refrigeration unit as well as the refrigeration machinery based on temperature data provided by the measuring sensors 35.1, 35.2 and 35.3, for example in a same manner than previously presented in this description.
The refrigeration unit according to the present disclosure may be imple-mented in several ways, and the methods of implementation are not limited to the examples presented above.

Claims

1. Refrigeration unit comprising - a storage space arranged within a thermally insulated outer housing for cold storage of products, and - a refrigeration machinery for lowering the temperature of the storage space to a temperature range defined by a minimum temperature and a maximum temperature, characterized in that the refrigeration unit further comprises - an air space arranged within the outer housing, between the thermal insulation of the outer housing and the storage space, - an inlet and outlet air pipe in connection to the air space for arranging an air circulation path within the air space, - measuring means for measuring the outdoor temperature, the temper-atures of the air space within the housing and the storage space, - air flow adjustment means arranged in connection with the inlet and/or outlet air pipe for adjusting the air circulation of the air space, and - control means adapted to control the refrigeration machinery and the air flow adjustment means as a response to the measured tempera-tures.

2. Refrigeration unit according to Claim 1, wherein - the inlet air pipe is adapted to extend to the outdoor air to conduct cold or cool outdoor air into the air space.

3. Refrigeration unit according to Claim 1 or 2, wherein the refrigeration unit further comprises - a wall made of material having high thermal conductivity between the air space and the storage space.

4. Refrigeration unit according any one of Claims 1-3, wherein the control means are adapted to control the refrigeration rnachinery and the air flow adjustment means such that - the temperature of the storage space is primarily adjusted by means of the air flow when the outdoor temperature cools down the tempera-ture of the air space and the temperature of the storage space main-tains below the desired maximum temperature, - the temperature of the storage space is primarily adjusted by means of the refrigeration rnachinery when the outdoor air is not cold enough to maintain the temperature of the storage space below the desired maximum temperature, and - when the temperature of the storage space decreases to a lower limit of the minimum temperature of the desired temperature range, nei-ther the refrigeration machinery nor the air flow is employed.

5. Refrigeration unit according to any one of Claims 1-4, wherein - the refrigeration unit further comprises a blower to achieve air circula-tion within the air space.

6. Refrigeration unit according to any one of Claims 1-4, wherein - the inlet air pipe is placed at the bottom part of the refrigeration unit and the outlet air pipe is placed at the upper part of the refrigeration unit to enable gravity-assisted air circulation within the air space.

7. Refrigeration unit according to any one of Claims 1-6, wherein - the outlet air pipe is adapted to be connected to the exhaust duct of the ventilation system of a building.

8. Refrigeration unit according to Claim 7, wherein - the refrigeration unit comprises a blower adapted to assist the gravity-assisted air circulation within the air space, and - the control means are adapted to assist the gravity-assisted air circula-tion by means of a blower when circulating air is able to cool down the temperature of the air space of the unit but the gravity-assisted air cir-culation is not enough for maintaining an air circulation sufficient for cooling within the air space.

9. Refrigeration unit arrangement comprising a refrigeration unit according to Claim 7 or 8 connected to the exhaust duct of a ventilation system of a building.