EP1966426A1

EP1966426A1 - Domestic appliance comprising a thermoelectric heat pump

Info

Publication number: EP1966426A1
Application number: EP06819825A
Authority: EP
Inventors: Hasan Gökcer ALBAYRAK; Klaus Grunert; Günter Steffens; Andreas Stolze
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2005-12-16
Filing date: 2006-11-29
Publication date: 2008-09-10
Anticipated expiration: 2026-11-29
Also published as: KR20080075874A; US9322126B2; WO2007068588A1; DE502006004264D1; US20090049843A1; EP1966426B1; KR101306420B1; DE102005060355A1

Abstract

The invention relates to a domestic appliance (1), especially a tumbler (1), comprising a thermoelectric heat pump (20, 26, 28). The aim of the invention is to prevent the Peltier elements (20) in the thermoelectric heat pump (20, 26, 28) from exceeding a predetermined threshold temperature under any circumstances. The resistance of the Peltier elements (20) increases with increasing temperature while the electrical power drawn by a constant mains voltage decreases. A separate heat flow path (34) allows heat being carried off from the individual Peltier elements (20). The heat flow path is designed in such a manner that with increasing temperature, the power P<SUB>therm</SUB> of the heat carried off becomes equal the electrical power P<SUB>el</SUB> which the Peltier elements (20) draw from the constant mains voltage.

Description

Domestic appliance with thermoelectric heat pump

The invention relates to a domestic appliance with a thermoelectric heat pump, which comprises at least one operable with a constant terminal voltage series arrangement of Peltier elements whose resistance increases with increasing temperature, and in which a limit temperature for the Peltier elements is predetermined.

From a document, which was downloadable on November 25, 2005 from the Internet address http://de.wikipedia.org/wiki/Peltier-Element, a Peltier element in structure and function is known, which has the structure described above , The half elements of this Peltier element are formed in columns or cuboid and consist of doped semiconductors as materials. The semiconductors are, in particular, bismuth telluride, and a p-type doped semiconductor and an n-type doped semiconductor are used. In each case a half element of the p-type doped semiconductor and a half element of the n-type doped semiconductor are each connected to one side via a printed circuit board, also referred to as a metal bridge, and at another side, which is opposite to said one side , Connected via a respective further circuit board with another half-element or a connection contact for connection of the Peltier element to an electrical network.

Further information on the basics, application-specific selection and assembly of Peltier elements can be found in documents published on 25 November 2005 from the Internet addresses http://www.quick-ohm.de/waerme/download/Erlaeuterung-zu-Peltierelementen .pdf and http://www.quick-ohm.de/waerme/download/Einbau.pdf were downloadable.

DE 1 410 206 A discloses a domestic appliance in the form of a washing machine, in which laundry can not only be washed, but also dried. For the additional facilities required for this, the document shows several alternatives; In particular, an electric heater for heating a for Drying of laundry used air flow and a simple heat exchanger for cooling the heated air stream after the loading of the laundry be provided, the heater and the radiator can also belong to a heat pump. The heat pump may be a heat pump that uses Peltier elements to utilize the thermoelectric effect; In this case, the heat pump is referred to as a "thermoelectric heat pump".

A domestic appliance for drying laundry, which emerges from an English summary extract belonging to the patent abstract "Patent Abstracts of Japan" for JP 08 057 194 A, contains, in addition to a heater and a radiator, both of which belong to a thermoelectric heat pump, a radiator upstream of a duct system additional heat exchanger for cooling the discharged air stream from the laundry and an additional heating device downstream of the heater for further heating of the air flow before the loading of the laundry.

A domestic appliance in the form of a tumble dryer with a thermoelectric heat pump is known from DE 69 26 182 U. Usually, the resistance increases with increasing temperature in all Peltier elements. For Peltier elements, a temperature limit is specified by using a solder that can melt. Usually, a threshold temperature for Peltier elements is 150 ° C.

The problem is such a structure when it comes to a disturbance in the operation of the domestic appliance, for example, a failure of a fan blower, excessive drying of the laundry or excessive loading of the airways with lint. If unsuitable safety measures are taken in such a case, the heat pump may be destroyed by overheating. Such overheating can damage a solder joint in a Peltier element and impair its electrical contact; It is also possible for a metal to diffuse out of an overheated solder joint into a semiconductor material of the Peltier element and to adversely affect its function.

In a clothes dryer or in a correspondingly upgraded washing machine laundry is usually dried in a laundry drum, the hot air is supplied. The hot air saturates with evaporating water, and the thus humidified air is supplied to the thermoelectric heat pump. On a cold side of this heat pump, water condenses out of the humidified air and is separated from it. The air is fed to a hot side of this heat pump, where it is reheated to be re-supplied to the laundry drum. This operation can be disturbed. For example, blockage in the airways, such as laundry or lint buildup, can cause insufficient air flow past the thermoelectric heat pump. It may also be the abnormal operating condition occur that the tumble dryer would have to stop because the laundry is dried or the laundry drum is empty, and that the tumble dryer still continues to run.

In each case, the Peltier elements of the thermoelectric heat pump are heated above their normal operating temperature, which is generally between 60 ° C and 100 ° C. It may easily be possible that their limit temperature is exceeded, which can lead to the failure of the modules and beyond a certain risk of fire.

It is an object of the invention to design a domestic appliance of the type mentioned so that it remains intact and safe even in an abnormal operating condition. This object is achieved by a type of domestic appliance with the features according to the characterizing part of patent claim 1.

According to the invention, therefore, heat can be dissipated from each Peltier element via a heat flow path. This is a separate heat flow path, which is different from the usual heat dissipation in the heating of the air at the hot side of the thermoelectric heat pump. The heat flow path is designed so that as the temperature rises, before reaching the threshold temperature, the power of the heat dissipated becomes equal to the electrical power that draws the Peltier elements from the constant supply voltage.

The invention is based on the recognition that the Peltier elements just do not need to be protected by thermal insulation, but that on the contrary a heat flow path must be provided, which dissipates heat from them. This Heat flow with the power Pt _h e _rm is different from the heat flow at the warm side of the heat pump. It transports the heat that flows through structural components of the heat pump and adjacent components of the tumble dryer. This heat flow is made available in the present case in order to achieve complete operational reliability of the heat pump. According to the invention, this maximum temperature is less than the limit temperature which the Peltier elements are allowed to reach a maximum. If P _th e _{rm is} equal to P _e ι, supply and removal of heat in the totality of the Peltier elements balance out, and the maximum temperature at which the two powers P _e ι and P _th e _{rm are} in equilibrium can not more are exceeded. By providing the additional heat flow path, the thermoelectric heat pump is intrinsically safe, ie there are no additional safety measures required to prevent exceeding the limit temperature. The connected load and the resistance of the Peltier elements on the one hand (whereby the resistance can be determined by the number of Peltier elements) are in a balanced relationship to the power Ptherm power dissipated via the additional heat flow path.

Due to the fortunate circumstance that the resistance of a Peltier element increases with increasing temperature, the electrical power drawn decreases with increasing temperature. As a result, the heat output to be dissipated in an emergency is less than the electrical power consumed during regular operation. The invention gives a clear prescription on how, on the one hand, the heat flow path is to be dimensioned and, on the other hand, how the electric power of the Peltier elements is to be faced. Of course, in the case of a fixed heat flow path, the electrical power of the Peltier elements to be drawn can also be changed in order to satisfy the conditions according to the invention. For example, the number of Peltier elements can be increased in order to increase the resistance of the Peltier elements and thus to lower the drawn power in order to fulfill the inventive condition for a given heat flow path.

The electrical power of the heat pump is in regular operation preferably between 800 W and 1500 W, in particular at 1000 W, at an operating temperature of

Heat pump between 60 ° C and 100 ° C, especially at 90 ° C. The resistance increases in an emergency by the slope of the temperature, so that the electric power at a no longer passable temperature, which is preferably between 120 ° C and 150 ° C, in particular at 120 ° C, is only about half.

Preferably, the power of the dissipated heat at the temperature at which it becomes equal to the drawn electric power is 450 W to 700 W, preferably 600 W.

If it is assumed that the heat to be conducted via the heat flow path reaches an environment with a temperature around 20 ° C. and the heat dissipatable via the heat flow path is proportional to the temperature difference across the heat flow path, then it is apparent from the above statements that the heat flow path in regular operation of the domestic appliance only a few 100 W, in particular about a quarter of the heat pump regularly recorded electrical power, dissipates heat.

Preferably, the domestic appliance has at least one additional heat cover in addition to the heat flow path, wherein furthermore preferably the heat flow path and this at least one additional heat cover are designed for discharging

Heat with a power at least equal to the power supplied by the Peltier

Pull elements at operating temperature. This creates a prerequisite for stationary operation, because for such stationary operation it is necessary that the entire power absorbed by the heat pump (as well as possibly additionally introduced into the circulation of air in the heat exchanger

Power) is dissipated. In a corresponding heat dissipation balance, the heat dissipated via the heat flow path goes only as relatively low, and easily accountable by appropriate design of other required heat leaks a contribution.

The stated numerical value of the power of the heat to be dissipated makes it clear that, if necessary, extensive cooling mechanisms have to intervene to form the heat flow path, for example cooling fins have to be provided, etc.

There will now be described an embodiment according to a preferred embodiment of the invention with reference to the drawing, wherein the figure schematically illustrates a domestic appliance in the form of a tumble dryer. The tumble dryer 1 comprises a laundry drum 10, from which air can be discharged via an air outlet opening 12, and into which air can be introduced via an air inlet opening 14. From the air outlet opening 12, the air enters the tube 16, wherein it is sucked by means of a blower 18. The air is guided in the tube 16 and via the tube 22 to an array of Peltier elements 20. The Peltier elements 20 (shown here as square blocks) are arranged in a row. A terminal voltage, which supplies the electrical power P _e i, is due to the Peltier elements at the 20th Of the Peltier elements 20, the air passes through the tube 24 via the blower 18 through the air inlet opening 14 into the drum 10 back.

The sucked into the pipe 16 air is loaded by located in the laundry drum 10 laundry (not shown) with moisture. This moisture condenses on a cold side 26 of the Peltier elements 20, which cold side 26 is formed from a thermally coupled to the Peltier elements 20 and in particular ribbed heat exchanger 26. The condensed moisture is collected over a known and presently not shown for clarity device and removed from the circulation of the air. From the cold side 26, the air passes to a hot side 28 of the Peltier elements 20, which hot side 28 is also formed from a thermally coupled to the Peltier elements 20 and in particular ribbed heat exchanger 28. There, the air is reheated and thus finally returns via the air inlet opening 14 in the laundry drum 10. The Peltier elements 20 form, with the cold side 26 and the hot side 28, a heat pump 20, 26, 28 in the tumble dryer 1.

A voltage source 30 provides the electrical voltage for operating the Peltier elements 20 to which it is connected via leads 32.

The system of the tubes 16, 22 and 24 may be prone to failure, in particular fluff from the laundry on the inside of the tube can adhere firmly and clog a pipe at least partially. Therefore, in a real laundry dryer 1 is always a sieve for

Collection of such lint (not shown here) provided. A disturbance can also be caused by a faulty, possibly completely precipitating fan 18 or excessive loading of the heat exchanger 26 and 28.

It may also be possible that the laundry drum 10 does not contain any laundry, or that the laundry has already dried very quickly. In all these cases, the air entering the pipe 16 is not affected by moisture, so that there is no condensation on the cold side 26. The air continues to heat up, which eventually increases the temperature of the Peltier elements 20.

In order to prevent the Peltier elements 20 from heating up further and further, it is provided that a heat flow path 34 leads away a heat flow with a power P _therm to be subsequently specified from the individual Peltier elements 20. This

Heat flow with the power Pt _h e _rm is different from the heat flow on the hot side 28. It transports the heat that comes through structural components of the

Heat pump 20, 26, 28 and adjacent components of the clothes dryer 1 drains. This heat flow is made available here to a complete

Operational safety of the heat pump 20, 26, 28 to achieve.

As the temperature rises, the resistance of the Peltier elements 20 increases. As a result, the electrical power P _e ι absorbed by them decreases. On the other hand, the power of the dissipated heat P _th e _rm increases due to the increasing temperature difference between the components of the heat pump 20, 26, 28 and the vicinity of the clothes dryer 1 into which the dissipated heat ultimately flows. Assuming that the temperature of the Peltier elements 20 still remains deep enough to maintain their structural and functional integrity, it comes at a certain temperature, the maximum temperature, the tie between Ptherm and P _e ι.

It is envisaged that this maximum temperature is less than the limit temperature, which may reach the Peltier elements 20 maximum. If P _therm equals P _e ι, supply and removal of heat in the totality of the Peltier elements 20 balance out, and the maximum temperature at which the two powers P _e ι and Pt _h e _{rm are} in equilibrium can no longer be crossed, be exceeded, be passed. By providing the additional heat flow path 34, the thermoelectric heat pump 20, 26, 28 intrinsically safe, ie there are no additional security measures required to prevent exceeding the limit temperature. The connected load and the resistance of the Peltier elements 20 on the one hand (wherein the resistance may be determined by the number of Peltier elements 20) are in a balanced relationship to the power Ptherm power dissipated via the additional heat flow path 34.

While a typical operating power is 1000W so as to provide sufficient condensation of water on the cold side 26 and heating of the air on the hot side 28 of the thermoelectric heat pump, the resistance of the Peltier elements 20 increases so much with temperature it is sufficient if P _th e _rm at the limit temperature of the Peltier elements 20 by 600W: The electric power P _e ι decreases with increasing temperature accordingly strong on this value, so as to the condition P _e ι = Pt _h e _rm to meet, and before the limit temperature is reached. Conventional limit temperatures of Peltier elements are at 150 ° C. It is possible to meet the condition P _e ι = Pt _h e _rm already at 120 ° C to 140 ° C.

So that the tumble dryer 1 can operate in a stationary operation, wherein the Peltier elements 20 assume their intended and interpretation according to operating temperature between 60 ° C and 100 ° C, in particular at about 90 ° C, the supply of heat to the tumble dryer 1 can be compensated by the removal of heat from the tumble dryer 1. Accordingly, a removal of all heat is provided, which arises in the Peltier elements 20 in regular operation. The heat flow path 34 does not do this alone, but there are more heat leaks available. These heat leaks include - not least because of the inevitable losses occurring - the tubes 16, 22 and 24 and the drum 10. It may be necessary to provide additional, optionally controllable heat leaks - for example, a part of circulating in the tumble dryer 1, hot air be discharged from this and replaced by cooler air from the environment of the tumble dryer 1. In any event, the heat flow path 34 and the additional heat leaks are designed to dissipate heat at a power that is at least equal to the power that the Peltier elements 20 pull at the operating temperature. It is possible to measure the electrical resistance of the arrangement of Peltier elements 20, which here acts as a self-controlled variable, in order to obtain information about the presence of abnormal states. It would be necessary for this purpose to install a (not shown) resistance meter in the Peltier elements 20 dining circuit. Accordingly, the clothes dryer 1 can be turned off early, before the abnormal condition has an adverse effect.

Claims

claims

1. Domestic appliance (1) with a thermoelectric heat pump (20, 26, 28) which comprises at least one operated with a constant terminal voltage series of Peltier elements (20) whose resistance increases with increasing temperature, and in which a limit temperature for the Peltier elements (20) is predetermined, characterized in that via a heat flow path (34) heat from the individual Peltier elements (20) can be derived, wherein the heat flow path (34) is designed so that at a maximum temperature above a regular Operation of the Peltier elements (20) occurring

Operating temperature and below the limit temperature, the power (Pt _h e _rm ) of the over the heat flow path (34) derived heat of the electric power (Pei) is the same, which pull the Peltier elements (20) from the constant terminal voltage.

2. Domestic appliance (1) according to claim 1, wherein the electric power drawn by the Peltier elements (20) at the operating temperature is between 800 W and 1500 W, in particular about 1000 W.

3. domestic appliance (1) according to claim 2, wherein the of the Peltier elements (20) drawn at the maximum temperature electrical power (P _e ι) between 450 W and 700W, in particular about 600 W, is.

4. domestic appliance (1) according to one of the preceding claims, wherein the operating temperature between 60 ° C and 100 ° C, in particular about 90 ° C, is.

5. domestic appliance (1) according to one of the preceding claims, wherein the maximum temperature between 120 ° C and 150 ° C, in particular about 120 ° C, is.

6. domestic appliance (1) according to one of the preceding claims, wherein in the

Operating temperature, the power of the over the heat flow path (34) discharged Heat corresponds to about a quarter of the electric power drawn by the Peltier elements (20).

7. domestic appliance (1) according to one of the preceding claims, which has at least one additional heat cover (10,16,22,24).

8. domestic appliance (1) according to claim 7, wherein the heat flow path (34) and the additional heat cover (10,16,22,24) are designed to dissipate heat with a power that is at least equal to the power that the Peltier Pull elements (20) at operating temperature.

9. domestic appliance (1) according to one of the preceding claims, which is designed as a tumble dryer (1).