Various example embodiments relate to a cooling unit and a refrigeration device comprising the cooling unit.

Background

Coolers, i.e. refrigeration devices, that are used to cool down objects, e.g. alimentary products, are often big and heavy cupboards based on compressor technology. The freezers comprising a compressor require usually a lot of space. Conventional freezers that use compressors for cooling produce noise which may be disturbing. In addition, compressor systems use chemical materials that are not environmentally friendly.

Thermoelectric cooling is based on thermoelectric effect. However, coolers operating based on thermoelectric effect are generally considered to have a poor efficiency.

There is, therefore, a need for an improved cooling unit and a refrigeration device.

Summary

Various aspects comprise a cooling unit and a refrigerator device, which are characterized by what is stated in the independent claims. Various example embodiments are disclosed in the dependent claims.

According to a first aspect, there is provided a cooling unit for cooling a target system, the cooling unit comprising a first part comprising a warm side of a thermoelectric cooler (TEC); a second part comprising a cool side of the TEC; a first air blowing means arranged to draw air from surroundings of the cooling unit to the first part; and supply air from the first part to the surroundings; a second air blowing means arranged to draw air from the target system to the second part; and supply air from the second part to the target system; an insulation frame arranged to separate the first part of the cooling unit and the second part of the cooling unit; and guide the air from the cool side of the TEC to the target system.

According to an embodiment, the first air blowing means comprises an axial fan.

According to an embodiment, the second air blowing means comprises a centrifugal fan.

According to an embodiment, at least part of a side of the insulation frame residing in the second part of the cooling unit has a curved shape for guiding air flow from the cool side of the TEC to the target system.

According to an embodiment, at least part of a surface of the insulation frame is coated with a foil.

According to an embodiment, the cooling unit further comprises a heatsink coupled to the warm side and/or the cool side of the TEC.

According to an embodiment, the cooling unit further comprises a casing comprising first ventilation means for air flow between the first part of the cooling unit and the surroundings; and second ventilation means for air flow between the second part of the cooling unit and the target system.

According to an embodiment, the second ventilation means comprises an outlet for air flow from the second part of the cooling unit to the target system; and an inlet for air flow from the target system to the second part of the cooling unit.

According to a second aspect, there is provided a refrigeration device for cooling one or more objects, comprising the cooling unit, wherein the refrigeration device comprises the target system; and an insulating casing. According to an embodiment, the refrigeration device further comprises a first holder for holding a first object of the one or more objects by an outlet for air flow from the second part of the cooling unit to the target system.

According to an embodiment, the first holder is arranged to guide air from the outlet for air flow from the second part of the cooling unit to the target system towards an inlet for air flow from the target system to the second part of the cooling unit.

According to an embodiment, the first holder is a longitudinal holder having a first end and a second end, wherein the first end is situated upper than the second end when the refrigeration device is in use position; and wherein the first end is arranged to receive the one or more objects.

According to an embodiment, wherein the second end is arranged to hold a first object of the one or more objects by an outlet for air flow from the second part of the cooling unit to the target system.

According to an embodiment, wherein the second end is arranged to hold a first object of the one or more objects by an opening comprised in the cooler for delivering the first object of the one or more objects.

According to an embodiment, the refrigeration device further comprises a second holder below the first holder, wherein the first holder comprises a slit for air flow towards the second holder.

Description of the Drawings

In the following, various example embodiments will be described in more detail with reference to the appended drawings, in which

Fig. 1 shows, by way of example, a thermoelectric element; Fig. 2 shows, by way of example, a thermoelectric assembly;

Fig. 3 shows, by way of example, an exploded view of components of a cooling unit;

Fig. 4 shows, by way of example, a bottom view of the cooling unit;

Fig. 5a, 5b and 5c show, by way of examples, an apparatus for cooling one or more objects;

Fig. 6 shows, by way of example, a block diagram of the cooling unit and/or the apparatus for cooling one or more objects;

Fig. 7a shows, by way of example, an apparatus for cooling one or more objects; and

Fig. 7b shows, by way of example, an opening for the cooling unit.

Description of Example Embodiments

Thermoelectric coolers operate by a thermoelectric effect, i.e. the Peltier effect. Fig. 1 shows, by way of example, a thermoelectric element, e.g. a thermoelectric cooler 100. The thermoelectric cooler (TEC), e.g. a Peltier element, comprises two sides, a hot side 1 10 and a cool side 120. The two sides may be plates of dielectric material e.g. ceramic plates or aluminium plates. Between the hot side 1 10 and the cool side 120 there are semiconductors, n-type semiconductors 130, 132, 134 and p-type semiconductors 140, 142, 144. The elements of semiconductor materials, thermocouples, are connected electrically in series and thermally in parallel. Conducting tabs 150, 151 , 152, 153, 154 may be used to interconnect the semiconductors. The conducting tabs may be e.g. copper or any suitable conducting material. The cooling ability of the TEC is proportional to the number of the thermocouples. The TEC comprises wire leads 160, 162. When current, direct current DC, moves across the TEC, it causes temperature differential between the sides 1 10, 120. As a result, the cool side 120 will be cooled while its opposite face, the hot side 1 10, simultaneously is heated.

There is provided a cooling unit for cooling a target system 290. The target system may comprise objects that needs to be cooled down and/or kept cool, in case the objects have been pre-cooled. Alternatively, the target system may comprise space, gas or a mixture of gas, e.g. air that needs to be cooled down. A dashed line 275 in Fig. 2 illustrates the target system 290 in a schematic way and its size is not proportional to the size of the cooling unit. Fig. 2 shows, by way of example, a thermoelectric assembly, i.e. a cooling unit 200. The cooling unit 200 comprises a first part 201 comprising a warm side 212 of a thermoelectric cooler (TEC) 210. The cooling unit 200 comprises a second part 202 comprising a cool side 214 of the TEC 210. The cooling unit 200 comprises a first air blowing means 220. The first air blowing means 220 is arranged to draw air from surroundings 295 of the cooling unit 200 to the first part 201 . The first air blowing means 220 is arranged to supply air from the first part 201 to the surroundings 295. The cooling unit 200 comprises a second air blowing means 230. The second air blowing means 230 is arranged to draw air from the target system 290 to the second part 202. The second air blowing means 230 is arranged to supply air from the second part 202 to the target system 290. The cooling unit 200 comprises an insulation frame 240. The insulation frame 240 is arranged to separate the first part 201 of the cooling unit 200 and the second part 202 of the cooling unit 200. The separation is to prevent the warm air in the first part 201 and cool air in the second part 202 from mixing with each other. Insulation between the first part and the second part ensures more efficient cooling of the target system. The insulation frame 240 is arranged to guide the air from the cool side 214 of the TEC 210 to the target system 290.

The TEC is situated such that it penetrates the insulation frame. The insulation frame may comprise an opening for the TEC. The warm side of the TEC is arranged in the first part of the cooling unit. The cool side of the TEC is arranged in the second part of the cooling unit. The material of the insulation frame may be e.g. expanded polystyrene (EPS). Alternatively, the material of the insulation frame may be e.g. expanded polypropylene (EPP) or any suitable insulating material.

The cooling unit 200 may comprise a heatsink 260 coupled to or connected to the warm side 212 of the TEC 210. The cooling unit 200 may comprise a heatsink 265 coupled to or connected to the cool side 214 of the TEC 210. The heatsink is a passive heat exchanger transferring the heat generated by the TEC to the air in the first part. Accordingly, the cold generated by the TEC is transferred by the heatsink to the air in the second part. The heatsink is designed to maximize its surface area in contact with the air surrounding the heatsink. The heatsink may comprise fins which are flat plates conducting heat and dissipating the heat into the air. The fins may be e.g. straight or flared fins, or pin fins. The heatsink 260 in the warm side may be larger in size than the heatsink 265 in the cool side. Larger heatsink improves the dissipation of the heat.

The cooling unit may comprise an extension block 213. The extension block may be connected to the cool side of the TEC. The extension block improves conduction of the cold further away from the warm side of the TEC. The material of the heatsink(s) and the extension block may be e.g. aluminium.

The cooling unit 200 comprises a casing 250. Material of the casing 250 may be e.g. plastic. The casing 250 is shown, by way of example, in more detail in Fig. 3. The casing 250 encompasses and protects the components of the cooling unit 200. The casing 250 comprises vents for airflow. The vents 280, 281 , 282, 283, 284 are schematically illustrated in Fig. 2.

The arrows 270, 271 , 272, 273, 274, 275, 276, 277 in Fig. 2 illustrate the flow of air when the cooling unit is in use. The arrow 270 illustrates the air flow from the surroundings 295, i.e. the ambient air, to the first part 201 of the cooling unit. The arrow 271 and the arrow 272 illustrate the air flow from the first part 201 of the cooling unit to the surroundings 295 of the cooling unit. The arrow 276 and the arrow 277 illustrate how the air flows in the first part 201 . The air is drawn in by the first air blowing means 220 and the air flows through the heatsink 260 as illustrated by the arrow 276 and the arrow 277. The insulation frame 240 may be arranged to guide the air from the warm side 212 of the TEC 210 to the surroundings 295.

The arrow 273 illustrates the air flow from the second part 202 of the cooling unit to the target system 290. The arrow 274 illustrates the air flow from the target system 290 to the second part of the cooling unit. The arrow 275 illustrates how the second air blowing means 230 draws air from the target system and blows the air through the heatsink 265 and supplies the air from the second part 202 to the target system 290. The insulation frame 240 is arranged to guide the air from the cool side 214 of the TEC 210 to the target system 290.

The first part 201 and the second part 202 of the cooling unit may be considered as spaces inside the casing 250. The first part 201 may be a top part of the cooling unit and the second part 202 may be a bottom part of the cooling unit. In addition to the warm side of the TEC, the first part 201 may comprise the heatsink 260 and/or the first air blowing means 220. The first part 201 may be the space or chamber defined by the insulation frame 240 and the casing 250.

In addition to the cool side of the TEC, the second part 202 may comprise the heatsink 265 and/or the second air blowing means 230. The second part 202 may be the space or chamber defined by the insulation frame 240 and the casing 250.

Fig. 3 shows, by way of example, an exploded view of components of a cooling unit 300. The casing 250 may comprise two parts, a top cover 251 and a bottom cover 252. The top cover and the bottom cover may form the casing 250 when attached to each other. It is to be understood that the casing 250 may be any kind of a housing or a container, wherein the components of the cooling unit may be arranged to such that they are protected by the casing. For example, the casing may be a housing or a container which may be arranged to be closed by a lid. The lid may be e.g. a hinged lid or a separate lid. The casing 250 comprises vents for airflow, which are described in more detail below.

When assembled, the top cover 251 and the insulation frame 240 may define the first part of the cooling unit 300. When assembled, the first part comprises a warm side 212 of a thermoelectric cooler (TEC) 210. When assembled, the bottom cover 252 and the insulation frame 240 may define the second part of the cooling unit 300. When assembled, the second part comprises a cool side 214 of the TEC 210. The cool side of the TEC may be connected to the extension block 213. The extension block improves conduction of the cold further away from the warm side of the TEC. The TEC is coupled to a control unit 340.

The cooling unit may comprise a heatsink 260 coupled to or connected to the warm side of the TEC. The cooling unit may comprise a heatsink 265 coupled to or connected to the cool side of the TEC. The heatsink 260 in the warm side may be larger in size than the heatsink 265 in the cool side. Larger heatsink improves the dissipation of the heat.

The cooling unit 300 comprises a first air blowing means 220. The first air blowing means 220 is arranged to draw air from surroundings of the cooling unit to the first part. The air may be drawn through the vents 312. The first air blowing means 220 is arranged to supply air from the first part to the surroundings. The air may be supplied through the vents 310, 314. The insulation frame 240 is arranged to guide the air from the warm side 212 of the TEC to the surroundings through the vents 310, 314. Even though the vents 310, 312, 314 are described as separate vents in Fig. 3, it is to be understood that there may be vents along a larger area on top of the top cover 251 . For example, the top cover may be or may comprise a grille.

The cooling unit 300 comprises a second air blowing means 230. The second air blowing means 230 is arranged to draw air from the target system to the second part. The air may be drawn through vents in the bottom cover, which are not visible in Fig. 3. The second air blowing means 230 is arranged to supply air from the second part to the target system. The air may be supplied through vents in the bottom part, which are not visible in Fig. 3.

The first air blowing means comprises a fan. The fan may be an axial fan 320. Alternatively, the first air blowing means may comprise a centrifugal fan or a plurality of fans, e.g. axial fans and/or centrifugal fans. The fan blades may form a spiral form. Axial fan causes air to flow through the fan in an axial direction. Axial fan has a high flow rate which is beneficial for the purpose of drawing air in to the first part of the cooling unit, towards the warm side of the TEC, and supply the warm air to the surroundings of the cooling unit in order to maximize the dissipation of the heat from the warm side of the TEC. The fan in the first part, e.g. axial fan 320, may be substantially centered with the vents 312 in order to improve the air flow from the surroundings to the first part of the cooling unit.

The second air blowing means comprises a fan. The fan may be a centrifugal fan 330. Alternatively, the second air blowing means may comprise a plurality of fans, e.g. axial fans and/or centrifugal fans. The centrifugal fan displaces air radially, changing the direction of the airflow. The fan blades of the centrifugal fan may be forward-curved, backward-curved or radial. The centrifugal fan creates a steadier flow of air and is beneficial for the purpose of directing the cold air towards the target system. The centrifugal fans produce less noise than the axial fans.

In addition to the fan(s), the first and the second air blowing means may comprise one or more motors configured to operate the fan. The blowing means are coupled to the control unit 340.

The cooling unit 300 comprises an insulation frame 240. When assembled, the insulation frame 240 is arranged to separate the first part of the cooling unit and the second part of the cooling unit 200. The separation is to prevent the warm air in the first part and cool air in the second part from mixing with each other. Insulation between the first part and the second part ensures more efficient cooling of the target system. The insulation frame 240 is arranged to guide the air from the cool side 214 of the TEC to the target system 290 through the vent 284. The vent 284 may be the outlet 410 shown in Fig. 4. The insulation frame 240 may be arranged to guide the air from the warm side 212 of the TEC to the surroundings through the vents 310, 314. For guiding, at least part of a side of the insulation frame 240 residing in the first part and/or the second part of the cooling unit has a curved shape. The curved shape decreases air resistance and acts as a guide for air flow from the cool side of the TEC to the target system and/or from the warm side of the TEC to the surroundings. Referring back to Fig. 2, the curved shape 241 is arranged to guide the air flow 275, flowing from the ventilation means 230 towards the curved shape 241 , towards the vent 284. The curvature of the curved shape 241 may be defined as approximately 70° in a distance of 4cm.

The insulation frame may be made of one part, e.g. using a mould, or may comprise several parts.

At least part of a surface of the insulation frame may be coated with a foil, e.g. aluminium foil or tin foil. For example, at least part of the surface of the insulation frame residing in the second part of the cooling unit and/or at least part of the surface of the insulation frame residing in the first part of the cooling unit may be coated with the foil. The foil coating increases a smoothness of the surface of the insulation frame thus reducing air resistance and improving air flow. The foil coating may reduce noise production of the cooling unit. The foil coating may be realized e.g. by a foil tape. The whole surface may be coated or alternatively, the portion of the surface of the insulation frame leading towards the vent 284 and comprising the curved shape 241 in Fig. 2 may be coated. Experiments have shown that the foil coating increases the production of cold. The foil coating increases the production of cold and contributes in reaching the temperature according to drink industry standards. The production of cold may be increased by approximately 2 °C. For example, without foil coating, the product may be cooled down to approximately 5 °C but when the coating is used on the surface of the insulation frame, the product may be cooled down to close to 3 °C.

The casing 250 comprises ventilation means for airflow. The casing comprises first ventilation means for air flow between the first part of the cooling unit and the surroundings. The first ventilation means may be or comprise e.g. the vents 310, 312, 314. The vents may be openings or slits of any form. The ventilation means may be or may comprise valves which open due to air pressure caused by flowing air when the air is drawn or supplied by the blowing means through the valve. Such valves that are open only when the air flows during use of the cooling unit may prevent e.g. dust from moving from the surroundings of the cooling unit to the cooling unit when the cooling unit is not in use.

The casing comprises second ventilation means for air flow between the second part of the cooling unit and the target system. Fig. 4 shows, by way of example, a bottom view of the cooling unit 300, when the components of the cooling unit are assembled. The second ventilation means may comprise an outlet 410 for air flow from the second part of the cooling unit to the target system. The second ventilation means may comprise an inlet 420 for air flow from the target system to the second part of the cooling unit. The fan in the second part, e.g. centrifugal fan 330, may be substantially centered with the inlet 420 in order to improve the air flow from the target system to the second part of the cooling unit.

The cooling unit 300 may comprise condensate removal means 440, 442. The condensate removal means may comprise e.g. a collector ramp for collecting the condensation water. The condensate removal means may comprise e.g. a drain, pipe or tube for removing the condensation water from the cooling unit. The condensate removal means may comprise a water cup for collecting the condensation water. The condensate removal means 440 removes condensation water when the cooling unit 300 is in substantially horizontal position when in use. The condensate removal means 442 removes condensation water when the cooling unit 300 is in substantially vertical position when in use. In the examples of Fig. 5a and Fig. 5b the cooling unit is arranged to substantially horizontal position when installed to a refrigeration device 500.

Referring back to Fig. 3, the cooling unit comprises a control unit 340. The control unit may comprise or may be connected to a user interface. The user interface may receive user input e.g. through a touch screen and/or a keypad. Alternatively, the user interface may receive user input from internet or a personal computer or a smartphone via a communication connection. The communication connection may be e.g. a Bluetooth connection, Satellite, GSM or a WiFi connection. The control unit may comprise e.g. a single board computer. The control unit is configured to control operation of the cooling unit. For example, the control unit may be configured to operate the fan motors and/or the TEC.

The cooling unit 300 may be installed in a cooling system, e.g. in an apparatus for cooling one or more objects. The cooling unit may be installed in different positions, e.g. in a substantially horizontal position or in a substantially vertical position. Air circulation is arranged such that it functions despite of the position of the cooling unit. The cooling unit may be electrically coupled to the cooling system.

Fig. 5a shows, by way of examples, an apparatus for cooling one or more objects 540, 541 , 540. The apparatus may be a refrigeration device 500 or a cooler device. The objects may be e.g. alimentary products, such as drinks and/or chocolate. The refrigeration device may be arranged to cool down cans, e.g. a drink can or a beverage can, such as a soda can.

The refrigeration device 500 comprises the cooling unit 300. The refrigeration device comprises the target system 290. The refrigeration device comprises an insulating casing 520, which is shown in Fig. 5b. The insulating casing 520 is arranged to at least partly enclose and thus insulate the target system 290. The insulating casing 520 may also be arranged to at least partly enclose the cooling unit 300. The insulating casing 520 reduces the heat transfer between the surroundings 590 of the refrigeration device 500 and the target system 290 such that the cool air flowing into the target system will be able to cool down and keep cool the objects in the target system 290. The insulating casing 520 may comprise e.g. two pieces such that a first piece may be placed on one side of the refrigeration device 500, as shown in Fig. 5b, and a second piece may be placed on another side of the refrigeration device 500. When placed like this, the first piece of the insulating casing and the second piece of the insulating casing will enclose between them at least partly the target system 290. In addition, the cooling unit may be placed between the first piece and the second piece of the insulating casing. The material of the insulating casing may be e.g. expanded polypropylene (EPP). Alternatively, the material of the insulating casing may be e.g. expanded polystyrene (EPS) or any suitable insulating material.

The cooling unit 300 may be attached to the refrigeration device, e.g. by assembling the cooling unit in the refrigeration device. As shown in Fig. 5a, the cooling unit 300 may be installed in the upper section of the refrigeration device. This may improve the cooling efficiency, since the cool air which has a higher density than warm air moves to the lower sections of the refrigeration device. The cooling unit 300 may be attached in any suitable way. For example, the cooling unit may be placed on a support 525, or attached, e.g. using screws or any fastening means such as adhesive fastening, from the top of the cooling unit to the frame 510. In case there is a support below the cooling unit, the support may comprise openings for airflow to enable airflow between the cooling unit and the target system through the inlet 420 and the outlet 410.

The refrigeration device 500 comprises one or more holders 530, 535 for holding the objects that are to be cooled. The refrigeration device 500 may comprise a first holder 530 for holding a first object 540 of the one or more objects 540, 541 , 542 by an outlet 410 for air flow from the second part of the cooling unit 300 to the target system 290. This way the cool air is efficiently directed to the first object to be delivered from the target system 290. The cooling is efficient, since the cooling is directed primarily towards the object(s), not only to the space in the target system 290.

Pull down power is a time needed to cool down an object from the ambient temperature to the target temperature. For example, the ambient temperature may be e.g. 21 °C and the targettemperature may be e.g. 3,4° C. Pull down power for this temperature difference achieved with the refrigeration device 500 comprising the cooling unit 300 is approximately 8h, when the objects are soda cans.

The first object 540 of the on or more objects 540, 541 , 542 is received in the target system before the other objects 541 , 542. The first object 540 is the first to be delivered from the target system. The objects 540, 541 , 542 may be received to the target system 290 through a first opening 550 of the refrigeration device 500. A user of the device, e.g. a salesperson, may fill the target system by entering the objects through the first opening 550. The first opening may be equipped with a door or a lid (see Fig. 5c, door 553) to improve the insulation such that the opening is not open when the objects are not entered through the opening. The objects 540, 541 , 542 may be delivered to a user, e.g. a customer buying the objects, through a second opening 552 of the refrigeration device 500. The second opening 552 may be equipped with a door or a lid to improve the insulation such that the opening is not open when the objects are not delivered through the opening. Since the refrigeration device 500 is arranged to deliver first the first object 540 received in the target system, the refrigeration device enables first-in, first-out (FIFO) accounting. Since the products are received and delivered through small openings, when compared to a door of a conventional freezer, thermal loss is minimized during the receiving and delivering.

The insulating casing may comprise corresponding openings to the first opening and the second opening.

The refrigeration device may comprise a frame 510, e.g. wood composite frame, metal frame, aluminium frame, plastic frame or a fibre class frame. The wood composite frame may comprise wood granulate and wood composite. The wooden frame is more environmental friendly than e.g. metal frames and plastic frames. The first opening 550 and the second opening 552 may be comprised in the frame 510. The frame 510 may comprise vents 560. The vents 560 of the frame may be arranged to substantially coincide, at least partly, with the vents 310 of the cooling unit 300 to improve the dissipation of heat from the first part of the cooling unit.

The first holder is arranged to guide air from the outlet 410 for air flow from the second part of the cooling unit 300 to the target system 290 towards an inlet 420 for air flow from the target system 290 to the second part of the cooling unit 300. This arrangement may improve the air circulation in the refrigeration device and between the target system and the cooling unit.

The first holder 530 may be a longitudinal holder having a first end 531 and a second end 532. The longitudinal holder may be in an inclined position such that the first end 531 is situated upper than the second 532 when the refrigeration device is in use position. The first end 531 may be arranged to receive the one or more objects. The first end 531 of the holder may be situated by the first opening 550 such that the object inserted to the target system may be placed on the first end 531 . The second end 532 may be arranged to deliver the one or more objects. In other words, the second end 532 of the holder may be situated by the second opening 552 such that the first object at the second end may be taken through the second opening 552. The inclined position of the holder causes the objects to move due to gravity from the first end 531 towards the second end 532. Thus, the user of the refrigeration device does not need to take care of arranging the objects, and/or moving the objects in order to manage the objects according to FIFO principle. The inclined position of the holder further guides the air from the outlet 410 for air flow from the second part of the cooling unit 300 to the target system 290 towards an inlet 420 for air flow from the target system 290 to the second part of the cooling unit 300. The second end 532 of the holder may be slightly bent upwards to stop the movement of the object and/or prevent the object from falling out from the refrigeration device, e.g. when the second opening 552 is open.

The second end 532 may be arranged to hold a first object 540 of the one or more objects 540, 541 , 542 by an outlet 410 for air flow from the second part of the cooling unit 300 to the target system 290. The second end 532 may be arranged to hold a first object 540 of the one or more objects 540, 541 , 542 by an opening 552 comprised in the cooler for delivering the first object of the one or more objects. This way the cool air is efficiently directed to the first object to be delivered from the target system 290. The cooling is efficient, since the cooling is directed primarily towards the object(s), not only to the space in the target system 290.

Distance between the outlet 410 and the inlet 420 may be e.g. approximately 20 cm. The distance is suitable for standard sized soda cans. The number of soda cans that fits between the outlet 410 and the inlet 420 is not too high, which is important since the products that have not been cooled before will warm up the target system and thus decrease the efficiency of the cooling. The TEC may be situated approximately in the middle between the inlet and the outlet.

The refrigeration device 500 may comprise a second holder 535. The second holder 535 may be a longitudinal holder arranged to an inclined position as described above in the context of the first holder. The second holder may be arranged below the first holder 530. The first holder 530 may comprise a slit 570, or a plurality of slits, for air flow towards the second holder 535. The slit is shown in Fig. 5c showing, by way of example, refrigeration devices. The slit 570 enables the air flow from the first holder towards the second holder. This arrangement may improve the air circulation in the refrigeration device and between the target system and the cooling unit.

The holder(s) may comprise longitudinal rails on which the product may be placed. The rail lifts a product from the surface of the holder such that the contact area between the product and the holder is reduced and the air may flow below the product. Fig. 5c shows examples of refrigeration devices, wherein the figure on the right shows a device from the inside. In the example of Fig. 5c, the objects to be cooled are drink cans or beverage cans 580, 581 . The size of the drink cans are standardized and the refrigeration device may be designed for certain sizes of the drink cans. For example, cans of 0.25 litre, 0,33 litre and 0.5 litre are suitable for objects to be cooled in the refrigeration device. The drink can has a cylindrical form and when placed on its side it may roll along the inclined holder from the first end 531 towards the second end 532. The second end 532 of the holder may be slightly bent upwards to stop the movement of the can and/or prevent the can from falling out from the refrigeration device, e.g. when the second opening 552 is open. The inclination of the holder may be e.g. 6° which is noted to be enough br the objects to roll and not too steep. An inclination which is too steep may cause the objects roll too fast and probably fall out from the refrigeration device.

Even though the Fig. 5c shows an example, wherein the objects to be cooled are drink cans, it is to be understood that other objects may be cooled by the refrigeration devices. The objects may be e.g. alimentary products such as chocolate bars. The bars may slide along the inclined holder from the first end 531 towards the second end 532. Material of the drink cans may be e.g. aluminium or tin-plated steel. Flowever, the refrigeration device may be suitable for e.g. plastic bottles. Aluminium or tin-plated steel cans may be cooled down faster than e.g. plastic drink bottles.

The door 553 may be a hinged door and may be arranged to self-close, e.g. by gravity, when not lifted or opened by a user.

The insulating casing 250 and the holder(s) 530, 535 may be made of the same material, e.g. EPP. The first piece of the insulating casing and at least part of the holder may form a monolithic structure. The holder(s) may be protrusions extending out from the casing, as shown in Fig. 5c. One side of the holder may be comprised in the first piece of the insulating casing. Another side of the holder may be comprised in the second piece of the insulating casing. The slit 570 may be arranged between the sides of the holders when the casing is assembled.

The cooling unit and/or the refrigeration device as presented herein is/are silent when in use. Common regulation for maximal noise level is 45 dB. The noise level of the refrigeration device has been measured to be below 45 dB, when measured with a calibrated sound level meter (Tenmars) approximately in 1 m distance from the front of the refrigeration device. The front side of the refrigeration device is the side through which the objects may be delivered to a user, e.g. a buyer. Low noise level of the cooling unit may be achieved by silent fans. Further, the surrounding structures, e.g. the insulating casing 520, the frame 510 and/or the casing 250 of the cooling unit may reduce the noise production. Filters for reducing noise may be installed in the vents 560 of the frame.

Low noise level is important, since the cooler systems are commonly used in retail places, e.g. groceries, coffee shops, gas station etc. and are commonly located near a cash desk. The size of the refrigeration device is such that it may be placed e.g. on a cash desk.

Fig. 6 shows, by way of example, a block diagram 600 of the cooling unit 300 and/or the apparatus for cooling one or more objects, e.g. a refrigeration device 500. The cooling unit comprises the control unit 340, e.g. a microcontroller unit (MCU). The control unit may comprise or may be connected to a user interface 610. The user interface may receive user input e.g. through a touch screen and/or a keypad. Alternatively, the user interface may receive user input from internet or a personal computer or a smartphone via a communication connection. The communication connection may be e.g. a Bluetooth connection or a WiFi connection. The control unit may comprise e.g. a single board computer. The control unit is configured to control operation of the cooling unit. For example, the control unit may be configured to operate the fan motors and/or the TEC.

The control unit may receive input from sensors. For example, the control unit may receive measurement data as input, e.g. from cool side temperature sensor 620 and/or warm side temperature sensor 630. In addition, the control unit may receive measurement data from target system temperature sensor 640. The temperature sensor(s) may be e.g. electrical temperature sensors, e.g. thermistors such as negative temperature coefficient (NTC) type sensors. The control unit may be configured to display the measurement data received from the sensors via the user interface.

The control unit may be configured to operate the TEC 655, e.g. via the TEC controller 650. The TEC controller may be e.g. a pulse-width modulator (PWM) controllers. For example, power of the TEC may be controlled based on the received measurement input from the temperature sensors in order to achieve and stay in a pre-defined target temperature, or a temperature range.

The control unit may be configured to operate the first air blowing means 670 and the second air blowing means 660. The operation of the air blowing means may be controlled using PWM controller. For example, rotation speed of the fans may be controlled based on the received measurement input from the temperature sensors in order to achieve and stay in a pre-defined target temperature, or a temperature range.

The cool side temperature sensor 620 may measure the heatsink temperature in the second part of the cooling unit. The control unit is configured to control the cool side temperature to prevent freezing of the heatsink. Thus, the cool side temperature should be kept above 0°C.

The input power for the control unit may be supplied from an external universal mains power adaptor.

The control unit may receive input from a condensation water level sensor 680. The condensation water level sensor may be in the condensation water cup. When the measurement data from the condensation water level sensor increases a predefined threshold, the control unit may be configured to indicate to the user, e.g. via the user interface, that the water cup needs to be emptied. Alternatively, there may be other indicators, e.g. LED indicators. Further, there may be a condensation water cup detection sensor, e.g. a microswitch. The control unit may receive input from the condensation water cup detection sensor. When the condensation water cup is present, based on the input, the control unit may be configured to indicate that to the user, e.g. via the user interface. Alternatively, there may be other indicators, e.g. light emitting diode (LED) indicators.

The control unit may comprise means such as circuitry and electronics for handling, receiving and transmitting data, computer program code in a memory, and a processor that, when running the computer program code, causes the device to carry out the controlling of the cooling unit.

Fig. 7a shows, by way of example, an apparatus for cooling one or more objects. The apparatus is a cardboard display 700. The cardboard display comprises the cooling unit 300. The cardboard display comprises the target system 790. The objects to be cooled may be placed in the target system 790. The cardboard display comprises an insulating casing 710. The material of the insulating casing is cardboard. The cooling unit may be installed in the cardboard display such that the ambient air is drawn from the surroundings 795 and the cold air flows through the outlet 410 to the upper parts of the target system. The cooling unit draws air through from the target system through the inlet 420 from lower parts of the target system. The cooling unit is installed in a substantially vertical position such that the outlet 410 is situated higher than the inlet 420. This way the cool air is flowing to the upper parts and due to its higher density than warm air, it moves to the bottom part of the target system. The cooling may be improved by a pipe or a tube that may be connected to the inlet 420 and arranged to draw air from the bottom parts 795 of the target system. This way the air circulation inside the target system may be improved.

Fig. 7b shows, by way of example, an opening 750 for the cooling unit which may be on a wall 720 of the cardboard display 700. The wall 720 is illustrated with a dashed line, since it’s a schematic drawing of the wall. For example, the opening for the cooling unit may be on the back wall of the cardboard display. The opening is arranged to receive the cooling unit and hold it such that it draws air from the surroundings and the cold air is blown to the target system, when the cooling unit is in use. The size of the opening 750 may be corresponding to the size of the cooling unit. The cooling unit may comprise attachment means for attaching the cooling unit to the cardboard display. For example, the cooling unit may comprise lugs. The opening 750 may comprise hollows 751 , 752, 753, 754 for receiving the lugs of the cooling unit. Alternatively, the cooling unit may be attached to the wall, e.g. by gluing or by hook-and-loop fastener. The wall may comprise openings in corresponding positions with the inlet 420 and the outlet 410 of the cooling unit. Cooling technology based on thermoelectric cooling is environmental friendly. Thermoelectric coolers do not use chemicals that are bad for environment. Thermoelectric coolers are maintenance-free. The cooling unit and/or the refrigeration device as presented herein is/are silent when in use.