EP4528182B1

EP4528182B1 - Tempering chamber having peltier elements

Info

Publication number: EP4528182B1
Application number: EP23198672.0A
Authority: EP
Inventors: Michal Foltýn
Original assignee: BMT Medical Technology sro
Current assignee: BMT Medical Technology sro
Priority date: 2023-09-20
Filing date: 2023-09-20
Publication date: 2025-11-19
Anticipated expiration: 2043-09-20
Also published as: EP4528182A1; US20250093080A1

Description

Field of technology

The present invention relates to tempering chambers with Peltier elements.

Prior art

A Peltier element is an electronic component that, when an electric current passes through it, develops different temperatures at the contact surfaces of two conductors (the so-called Peltier effect). Thus, when an electric current passes through the element, the Peltier element behaves like a heat pump, with one side of the element heating up at the expense of the other side, which cools down. The side that heats up is called the hot side and the side that cools down is called the cold side. When the polarity of the electric current is reversed, the sides are swapped and the side that was originally heated cools and the side that was originally cooled heats. For the purposes of this description, these sides are referred to as a first side and a second side, and depending on the polarity of the electric current, this means the hot side and the cold side, or the cold side and the hot side.
For efficient heat transfer, heatsinks are mounted on the cold and hot sides of the Peltier elements. The simplest design of a heat pump based on Peltier elements is one where one Peltier element is clamped by screws between a heated heatsink and a cooled heatsink by a force defined by the Peltier element manufacturer. For the purposes of this description, these heatsinks are referred to as a first heatsink and a second heatsink, and depending on the polarity of the electric current, this means the heated heatsink and cooled heatsink, or the cooled heatsink and heated heatsink. For the purposes of this description, a heat pump based on a Peltier element means a tempering module.
Sometimes a spacer made of a thermally conductive material is inserted between the Peltier element and the cooled heatsink or heated heatsink. The spacer increases the distance between the cooled heatsink and the heated heatsink and allows the gap to be filled with a larger layer of thermal insulation, thereby reducing unwanted heat exchange between the cooled and heated heatsink. In order to maximize the heat transfer between the Peltier element, the heated heatsink, the spacer and the cooled heatsink, a thermally conductive paste is applied to their contact surfaces. To increase the efficiency of heat transfer, both heatsinks are flushed with a liquid medium, usually air.
For a proper function and long life of the Peltier element, all surfaces in contact with the Peltier element must be manufactured to the required flatness tolerance specified by the Peltier element manufacturer.
The problem arises when the tempering module contains more than one Peltier element, and at the same time contains only one heated heatsink and only one cooled heatsink. As the electric current passes through the Peltier elements, the heated heatsink starts to lengthen, and the cooled heatsink shortens due to thermal expansion. As a result, the tempering module starts to bend, and this changes the flatness of some of the contact surfaces that are in contact with the Peltier elements. This can result in failure of the Peltier elements over time.
The US patent application US 2005126184 A1 discloses a tempering module comprising two arrays of N and P thermoelectric semiconductor elements, wherein each element has a first (cold) side and a second (hot) side. Said at least two arrays of elements are oriented with their first (cold) side so as to be in thermal contact with a common shared cold heatsink, and each array of elements is oriented with its second (hot) side so as to be in thermal contact with an individual array of hot heatsinks, further connected to electrical terminals. The N and P thermoelectric semiconductor elements form an array of elements electrically connected by conductive connector tabs of the cold heatsink and conductive tab-like base ends of the hot heatsinks. Owing to this electric connection, the whole array of elements is interpreted as one Peltier element. Disadvantageously, the cold heatsink and the individual array of hot heatsinks cannot be swapped because the individual array of hot heatsinks is electrically connected to the array of elements and moisture and frost would accumulate on such a hypothetical individual array of cold heatsinks, thus increasing the risk of short-circuiting the whole module.
The European patent EP 2891176 B1 discloses a tempering module comprising at least two thermoelectric modules, wherein each thermoelectric module has a first (hot) side and a second (cold) side. Said at least two thermoelectric modules are oriented with their first (hot) side so as to be in thermal contact with a common shared hot heatsink. Moreover, at least two, but not each thermoelectric module is oriented with its second side so as to be in thermal contact with a respective separate one of cold heatsinks. Fig. 5 of said document shows two groups by four thermoelectric modules. Disadvantageously, the tempering module starts to bend upon heating of the hot heatsink and cooling of the cold sink, and this changes the flatness of some of the contact surfaces that are in contact with the thermoelectric modules. This can result in shortened lifetime and failure of the thermoelectric modules over time.
The US patent US 6463743 B1 discloses a tempering module comprising at least two thermoelectric cooler devices, wherein each thermoelectric cooler device has a first (hot) side and a second (cold) side. Said at least two thermoelectric cooler devices are oriented with their first (hot) side so as to be in thermal contact with a common shared hot heatsink. Fig. 4A of said document showing three thermoelectric cooler devices arranged in one horizontal plane front to back in thermal contact with a common shared hot heatsink. Moreover, at least two, but not each thermoelectric cooler device is oriented with its second (cold) side so as to be in thermal contact with a respective separate one of cold heatsinks. Fig. 4A of said document shows three thermoelectric cooler devices arranged in one horizontal plane front to back in thermal contact with a common shared cold heatsink, and Fig. 4B of said document shows two thermoelectric cooler devices arranged in two different horizontal planes one above another, each in thermal contact with an individual cold heatsink. Disadvantageously, the tempering module starts to bend upon heating of the hot heatsink and cooling of the cold sink, and this changes the flatness of some of the contact surfaces that are in contact with the thermoelectric cooler devices. This can result in shortened lifetime and failure of the thermoelectric cooler devices over time.
The US patent US 6463743 B1 also discloses a tempering chamber comprising a wall with a tempering module mounted thereon. The common shared hot heatsink is arranged on an outer side of said wall, on which a first fan is arranged for pushing air into the common shared hot heatsink in a substantially perpendicular direction to the plane of the first side of the Peltier element. At least two cold heatsinks and a second fan for pushing air into the cold heatsinks in a direction substantially parallel to the plane of the second side of the Peltier element are arranged on an inner side of said wall. At least one flow rectifier in the form of a pair of subsequent conduits is arranged on the inner side of said wall. The cold heatsinks and the second fan are arranged in a pair of conduits between the inner side of said wall and a floor of the tempering chamber. The floor of the tempering chamber separates said pair of conduits from the interior of the tempering chamber and comprises an air inlet for sucking air therethrough from the interior of the tempering chamber into the second fan. Disadvantageously, the second fan is arranged with its rotational axis parallel (Fig. 4B of said document) or at a non-orthogonal angle with respect to said wall (Fig. 5 of said document), decreasing available cooling space within the tempering chamber and less effective cooling of the cold heatsinks.
The US patent US 5315830 A1 discloses a similar modular thermoelectric assembly including a thermoelectric device with a hot sink and a cold sink.
Consequently and with respect to known prior art, there is a need in the prior art to provide a tempering chamber comprising a more compact tempering module with Peltier elements with longer lifetime and lower failure rate.

Summary of the invention

The object of the invention is to provide a tempering chamber with Peltier elements that maintains the flatness of the contact surfaces resulting from thermal expansion, thereby extending its lifetime and reducing failure rate. The compact arrangement of the tempering module within the tempering chamber increases the available interior space.
The object is achieved by a tempering chamber comprising a wall with a tempering module mounted thereon. The tempering module comprises at least two Peltier elements, wherein each Peltier element has a first side and a second side, and wherein said at least two Peltier elements are oriented with their first side so as to be in thermal contact with a common shared first heatsink (i. e. a common shared hot heatsink).
Each Peltier element is oriented with its second side so as to be in thermal contact with a respectively separate one of second heatsinks (i. e. a respectively separate one of cold heatsinks).
On the outer side of said wall, the first heatsink is arranged on which a first fan is arranged for pushing air into the first heatsink in a substantially perpendicular direction to the plane of the first side of the Peltier element. At least two second heatsinks are arranged on the inner side of said wall. A second fan is further arranged on the inner side of said wall for pushing air into the second heatsinks in a direction substantially parallel to the plane of the second side of the Peltier element. The cooled heatsinks and the second fan are arranged in a space between the inner side of said wall and a cover plate. The cover plate separates said space from the interior of the tempering chamber and comprises an opening for sucking (drawing) air therethrough from the interior of the tempering chamber into the second fan.
In this arrangement, the cooled heatsinks are flushed with air from the side of the cooled heatsink through the gaps between the fins. In this way, one second fan arranged in this way can provide air flushing to one or more cooled heatsinks which are arranged on one or more tempering modules. A further advantage of the second fan positioned in this way is its height space saving compared to a second fan positioned from above on the cooled heatsink.
At least one flow rectifier is arranged on the inside of said wall to increase the efficiency of flushing of the cooled heatsinks.
The underlying idea of the tempering module according to the present invention is that a rotational axis of the second fan is arranged perpendicular to the cover plate and extends through the opening in the cover plate to save height space.
According to the present invention, the first side is the hot side, the second side is the cold side, the first heatsink is the heated heatsink, and the second heatsink is the cooled heatsink, and these terms are used interchangeably below, although one skilled in the art understands that when the polarity of the electric current is reversed, opposite definitions apply.
Thus, the tempering module according to the present invention comprises just as many cooled heatsinks as it comprises Peltier elements. Owing to this structure, the passage of electric current due to heating of the heated heatsink results only in its linear extension, whereby the desired flatness of the surfaces in contact with the Peltier elements is not affected. Even in the case of reversal of the polarity of the electric current, when the originally heated heatsink starts to cool and the originally cooled heatsinks start to heat, there is no bending of the tempering module, but only its linear shortening.
This structure also allows easy removal of the cooled heatsinks. This makes it possible, e.g. in the event of a tempering module failure, to replace only the tempering module without the cooled heatsinks, to which the original cooled heatsinks from the failed tempering module are fitted, saving production costs.
A further advantage of this invention is that other cooled heatsinks with different cooling fin direction can be mounted on the tempering module with unmounted cooled heatsinks, as it is the most advantageous for the air flow and positioning of the tempering module.
A spacer may be arranged between the second side of each Peltier element and each corresponding individual second heatsink to allow thermal contact between the Peltier element and the second heatsink in order to increase the distance between the cooled heatsink and the heated heatsink and to create a gap to be filled with a larger layer of thermal insulation, thereby reducing unwanted thermal exchange between the cooled and heated heatsink.
The first heatsink and the second heatsink can be attached to the spacer. The first heatsink may be secured to the spacer by means of first screws, preferably provided with a resilient member (e.g. a disc spring), a steel washer and a thermal insulating member (e.g. a thermal insulating pad) to limit heat transfer between the first heatsink and the spacer. The second heatsink may be attached to the spacer by second bolts, preferably provided with a resilient element (e.g. a resilient washer).
The first and second sides of each Peltier element, as well as both sides of the first and each second heatsinks in thermal contact with the corresponding Peltier element, may be coated with a layer of thermally conductive paste for as efficient heat transfer as possible. The first and/or second heatsink may be formed as a finned air heatsink. The fins of the first heatsink may be oriented parallel to the fins of the second heatsink or perpendicular to the fins of the second heatsink.
Thermal insulation can be placed between the heated heatsink and the cooled heatsinks.

Brief description of the drawings

Figure 1 shows a side sectional view of a tempering module which can be used in a tempering chamber according to the present invention.
Figure 2 shows a front view of a tempering chamber according to the present invention with a cover plate (A) and without a cover plate (B).
Figure 3 shows a rear view (A) and a sectional view along A-A (B) of a tempering chamber according to the present invention.

Examples

Example 1

A first example of a tempering module which can be comprised in a tempering chamber according to the present invention, which invention is defined by independent claim 1, is shown in Figure 1. The tempering module comprises three Peltier elements 2, each Peltier element 2 having a first side (typically a hot side) and a second side (typically a cold side) and said three Peltier elements 2 are oriented with their first side so as to be in thermal contact with a common shared first heatsink 1 (typically a heated heatsink). Each Peltier element 2 is oriented with its second side so as to be in thermal contact with a separate second heatsink 4 (typically a cooled heatsink). A spacer 3 (e.g., a spacer cube) is arranged between the second side of the Peltier element 2 and the second heatsink 4 to allow thermal contact between the Peltier element 2 and the second heatsink 4. The first heatsink 1 is fixed to the spacer 3 by means of first screws 5 provided with a disc spring 6, a steel washer 7 and a thermal insulating pad 8 to limit the thermal contact between the first heatsink 1 and the spacer 3. The second heatsink 4 is fixed to the spacer 3 by means of second screws 10 provided with a resilient washer 9. The first and second sides of the Peltier element 2 and both sides of the first and second heatsinks 1, 4 in thermal contact with the Peltier element 2 are provided with a layer of thermally conductive paste 11. A thermal insulation 12 is provided between the first heatsink 1 and the second heatsink 4. The first and second heatsinks 1, 4 are formed as finned air heatsinks, wherein the fins of the first heatsink 1 (not shown in Figure 1) are oriented perpendicular to the fins of the second heatsink 4.

Example 2

A second example, representing an embodiment of the present invention, is a tempering chamber 13 according to Figures 2A, 2B, 3A and 3B. The tempering chamber 13 comprises a wall 19 with two mounted tempering modules 17 according to Example 1. On the outer side of said wall 19, a first heatsink 1 is arranged at each tempering module 17 , on which a first fan 18 is arranged for pushing air into the first heatsink 1 in a substantially perpendicular direction to the plane of the first side of the Peltier element 2. On the inner side of said wall 19 (typically the inner side of the rear wall 19), three second heatsinks 4 are arranged at each tempering module 17. Further, on the inner side of said wall 19, a second fan 15 is arranged for pushing air into the second heatsinks 4 sucked through an opening 21 in a cover plate 14, from the tempering chamber 13, in a direction substantially parallel to the plane of the second side of the Peltier element 2 . Further, two flow rectifiers 16 are arranged on the inner side of the rear wall 19 of the tempering chamber 13 for directing the air pushed in by the second fan 15. The second heatsinks 4 and the second fan 15 are arranged in a space 20 between the inner side of the rear wall 19 of the tempering chamber 13 and the cover plate 14. A rotational axis 22 of the second fan 15 is arranged perpendicular to the cover plate 14 and extends through the opening 21.

Industrial applicability

The above-described tempering chamber can be used as various instrument, coolable and/or heatable chambers, e.g. laboratory incubators or storage and test cabinets.

List of reference signs

1: first heatsink
2: Peltier element
3: spacer
4: second heatsink
5: first screws
6: disc spring
7: steel washer
8: thermal insulating pad
9: resilient washer
10: second screws
11: thermally conductive paste
12: thermal insulation
13: tempering chamber
14: cover plate
15: second fan
16: flow rectifier
17: tempering module
18: first fan
19: wall
20: space
21: opening
22: rotational axis

Claims

A tempering chamber (13) comprising a wall (19) with a tempering module (17) mounted thereon, wherein the tempering module (17) comprises at least two Peltier elements (2), wherein each Peltier element (2) has a first side and a second side, and wherein said at least two Peltier elements (2) are oriented with their first side so as to be in thermal contact with a common shared first heatsink (1), wherein each Peltier element (2) is oriented with its second side so as to be in thermal contact with a respectively separate one of second heatsinks (4), wherein the first heatsink (1) is arranged on an outer side of said wall (19), on which a first fan (18) is arranged for pushing air into the first heatsink (1) in a substantially perpendicular direction to the plane of the first side of the Peltier element (2), wherein at least two second heatsinks (4) and a second fan (15) for pushing air into the second heatsinks (4) in a direction substantially parallel to the plane of the second side of the Peltier element (2) are arranged on an inner side of said wall (19), wherein at least one flow rectifier (16) is arranged on the inner side of said wall (19), wherein the second heatsinks (4) and the second fan (15) are arranged in a space (20) between the inner side of said wall (19) and a cover plate (14), wherein the cover plate (14) separates said space (20) from the interior of the tempering chamber (13) and comprises an opening (21) for sucking air therethrough from the interior of the tempering chamber (13) into the second fan (15), characterized in that a rotational axis (22) of the second fan (15) is arranged perpendicular to the cover plate (14) and extends through the opening (21).
The tempering chamber (13) according to claim 1, characterized in that a spacer (3) is arranged between the second side of each Peltier element (2) and each corresponding individual second heatsink (4) to allow thermal contact between the Peltier element (2) and the second heatsink (4).
The tempering chamber (13) according to claim 2, characterized in that the first heatsink (1) and the second heatsink (4) are attached to the spacer (3).
The tempering chamber (13) according to any one of the preceding claims, characterized in that the first heatsink (1) is attached to the spacer (3) by means of first screws (5), preferably provided with a thermal insulating element (8) to limit the thermal contact between the first heatsink (1) and the spacer (3).
The tempering chamber (13) according to any one of the preceding claims, characterized in that the second heatsink (4) is attached to the spacer (3) by means of second screws (10).
The tempering chamber (13) according to any one of the preceding claims, characterized in that the screw connection by means of the first and/or second screws (5, 10) comprises a resilient element (6, 9).
The tempering chamber (13) according to any one of the preceding claims, characterized in that the first and second sides of each Peltier element (2) as well as both sides of the first and each second heatsink (1, 4) in thermal contact with the corresponding Peltier element (2) are coated with a layer of thermally conductive paste (11).
The tempering chamber (13) according to any one of the preceding claims, characterized in that the first and/or second heatsink (1, 4) is formed as a finned air heatsink.
The tempering chamber (13) according to claim 8, characterized in that the fins of the first heatsink (1) are oriented parallel to the fins of the second heatsink (4) or perpendicular to the fins of the second heatsink (4).