GB2563575A

GB2563575A - Thermoelectric dehumidifier

Info

Publication number: GB2563575A
Application number: GB1709291.7A
Authority: GB
Inventors: Francesconi Guido; Tuley Richard
Original assignee: European Thermodynamics Ltd
Current assignee: European Thermodynamics Ltd
Priority date: 2017-06-12
Filing date: 2017-06-12
Publication date: 2018-12-26
Also published as: GB201709291D0

Abstract

A thermoelectric dehumidifier with an improved coefficient of performance (COP) obtained by cooling the thermoelectric device 100 hot side 102 more effectively than prior arrangements by supplying both the air cooled 105 on the thermoelectric device cold side 101 and the cold condensate 106 collected from the thermoelectric cold side to the hot side without having the latter re-evaporate into the hot side air stream which can thus be delivered back into the original environment. Units may be stacked or provided with an air valve (208 Fig. 2) to bypass the hot side whilst still supplying condensate.

Description

THERMOELECTRIC DEHUMIDIFIER

Inventors:

Guido Francesconi: 8 Priory Business Park, Kibworth, Leicestershire, LE8 ORX. UK Richard Tuley: 8 Priory Business Park, Kibworth, Leicestershire, LE8 ORX. UK

FIELD OF THE INVENTION

The present invention relates to the field of thermoelectric dehumidifiers.

BACKGROUND

Thermoelectric devices use the Peltier effect to pump heat across the device itself. Thus one side tends to get cold while the other hot. The coefficient of performance (COP) of the thermoelectric device improves as the temperature differential (ΔΤ) across the device decreases.

Thermoelectric devices have long been used as dehumidifiers. The air is dehumidified by lowering its temperature below the dew point on the cold side of the thermoelectric device. Heat sinks or heat exchangers are usually placed on both sides of the thermoelectric device to enhance heat transfer and increase the condensation surface area.

Different approaches are known to lower the ΔΤ across the thermoelectric device and thus improve the COP. These can be broadly grouped under two methods.

One method consists in ducting the air dehumidified and cooled on the cold side of the thermoelectric device onto the thermoelectric hot side itself to cool this more effectively compared to cooling the hot side with ambient air. The dehumidified re-heated air can then be delivered back into the original environment at a temperature close to ambient. The condensate on the thermoelectric cold side is collected or discarded externally to the environment to be dehumidified. This is the case for example of patent US 3126710 A, US 5448891 A, US 5555732 A, US 2944404 A, US 20120174599 Al, US 5921088 A, US 20100107656 Al, US 5575835 A, US 8613200 B2, US 20070272290 Al, US 20100101239 Al, US 5279128 A, US 9555686 B2, DE 4227148 Al, US 8079223 B2, US 9388994 B2, US 6834509 B2.

The second method consists in ducting the condensation from the thermoelectric cold side onto the thermoelectric hot side where it is evaporated into the hot air stream. During evaporation, the condensate absorbs the latent heat of vaporization thus aiding in cooling the thermoelectric hot side and improving the COP. The hot air stream, which contains the evaporated water, cannot be delivered back into the environment to be dehumidified and is thus discarded elsewhere. This is the case for example of patent US 5884486 A, US 3040538 A, US 8256236 B2, US RE44272 El, US 20060118274 Al, US 8601824 B2, US 7272936 B2, US 6907739 B2, US 6817197 BI, US 20090000031 Al.

SUMMARY OF THE INVENTION

The present invention describes a method to improve the COP of the thermoelectric dehumidifier by cooling the thermoelectric hot side more effectively by employing both the air cooled on the thermoelectric cold side as well as the condensed cold water without having the latter re-evaporate into the hot side air stream which can thus be delivered back into the original environment. It is a second objective of this invention to describe a more versatile thermoelectric dehumidifier which allows to combine dehumidifying and thermal management functions in one compact unit while optimizing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS Figure lisa schematic cross-sectional view of the present invention.

Figure 2 shows a different embodiment of the present invention with additional functionalities. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows the preferred embodiment 110 of the present invention. A fan 103 increases the rate of condensation by forcibly blowing ambient humid air from the environment to be dehumidified onto the heat sink 101 located on the cold side of the thermoelectric device 100. Here, the air is cooled below the dew point and is thus dehumidified. The same cooled air 105 is then ducted 104 onto the heat sink 102 located on the hot side of the thermoelectric device thereby cooling the hot side more effectively compared to blowing ambient air onto the hot heat sink. The now re-heated air is re-introduced into the original environment at a temperature close to ambient.

Moreover, the condensate 106 from the cold side is ducted into the hot heat sink without having it evaporate into the hot air stream which is to be re-inserted into the environment to be dehumidified. One method to achieve this is to have the condensate flow via gravity through grooves drilled into the hot heat sink base 107 and then discarded outside the target environment or collected in a separate container. The heat dissipated on the hot heat sink is thus partially absorbed also by the cold condensed water, thus exploiting its high heat capacity.

The ΔΤ across the thermoelectric assembly is hence more effectively reduced leading to higher COP and thus lower temperatures on the thermoelectric cold side which in return leads to higher rate of condensation and cooler air, both to be used in cooling the thermoelectric hot side, thus creating a positive feedback loop.

By not removing air from the target environment to be dehumidified, this is not depressurized and thus potentially undesirable external air infiltrations are reduced. This can lead to further energy savings by reducing the dehumidification and thermal management requirements of such infiltrated external air.

The person skilled in the art will understand that other methods to duct the condensate are possible and that different heat exchange assemblies can replace the aforementioned heat sink. For example, the condensate could drip by gravity directly through ring-shaped thermoelectric devices into wicks leading into the hot side heat sink. It is also understood that multiple thermoelectric devices can be used and connected in series or in parallel.

Further, the heat exchange assemblies can be coated with appropriate coatings to facilitate condensation on their surface. Finally, the thermoelectric device polarity can be temporarily reversed to defrost potential frozen condensation.

It is noted that the present invention also offers advantages in terms of compactness and efficiency also due to the fact that only one fan can be employed to forcibly blow air on both sides of the thermoelectric assembly.

The present invention may be used for different applications including electronic cabinets, home and hybrid or electric vehicles.

Figure 2 shows a different embodiment with additional functionalities that can be attributed to the original concept. A valve 208 is placed after the cold heat sink 201. This allows to re-direct some or all of the air 209 blown by the fan 203 and cooled by the cold heat sink 201 directly into the original environment thus providing cooling besides dehumidifying functions at the expense of lower COP of the thermoelectric device 200 since less or no cooled air 205 is directed onto the hot heat sink 202 which in the worst case scenario is thus cooled by ambient natural convection. For thermal management purposes, the heated air from the hot side must now be ducted 204 externally to the original environment in order to preserve the cooling effect.

The condensed water 206 however can still be used to cool the hot heat sink base 207 as in the preferred embodiment.

It is also understood that multiple units 210 of this embodiment can be connected in series to achieve greater dehumidification and cooling effect. This can be achieved by ducting the cooled air re-directed by the valve through a second unit thermoelectric cold side before reentering the target environment.

Claims

CLAIMS We claim a dehumidifier comprising a thermoelectric device, a heat sink on the cold side, a heat sink on the hot side, airflow which passes over the cold side and subsequently the hot side, and a condensate channel which drains condensate from the cold side heat sink to the hot side heat sink where the temperature of the water is increased without substantial evaporation before the water is drained from the hot side heat sink.