DE102008054224A1 - Method of transporting liquids, thermal capillary pump and their use - Google Patents

Abstract

The invention relates to a method for TTrnasport of liquids in a microfluidic circulation system, in which a thermal capillary pump is used. Furthermore, the invention relates to a microfluidic cooling circuit containing at least one thermal capillary pump. The thermal capillary pump or the cooling circuit is used in microsystem technology and micro process engineering, in particular in fuel cell systems.

Description

The The invention relates to a method for transporting liquids in a microfluidic circulatory system where a thermal capillary pump is used. Furthermore, the invention relates to a microfluidic Cooling circuit, the at least one thermal capillary pump contains. Use finds the thermal capillary pump or the cooling circuit in microsystem technology and micro process engineering, especially in fuel cell systems.

microfluidic gain in the field of micro process engineering and microsystems technology always greater importance, since the areas in which the Transport of very small amount of liquid required is, constantly evolving. An exemplary Scope is here z. B. the transport of liquids in the cooling circuit of electronic components as well as the Application in the field of biochemical analysis.

Out M. Zimmermann et al .: "Continuous flow in open microfluidics using controlled evaporation", Lap Chip, 2005, 5, 1355-1359 , a method is known to deliberately transport and control very small amounts of liquid in a microfluidic network (MFN). The method described here is used in immunoassays.

Out F. Heuck et al. "Evaporation-based micro-pump integrated into a scanning force microscope sample", Microelectric Engineering 85, (2008), 130-1305 , a micropump is known which is based on capillary effects and used in microscopes. The hydrophilic fluidic system is filled via a reservoir with liquid by means of capillary forces. In the evaporator, the liquid is vaporized and diffuses through an opening into the environment.

Juncker et al .: "Autonomous Microfluidic Capillary System", Anal. Chem. 2002, 74, 6139-6144 , describe an autonomous capillary system for delivering small amounts of fluids based on capillary effects and evaporation.

From the US 5,303,768 For example, a capillary pump is known which comprises an evaporator, a condenser and a channel for steam as well as for liquid. The capillary pump is used in the thermal management of spacecraft with a power range between 5 and 15 kW. The materials used are thermoplastics and aluminum.

From the EP 1 427 971 31 is known a capillary pump, which is used in the cooling circuit of computers. The arrangement described here is used for the removal of heat on the principle of a heat pipe (English heat pipe).

The The systems described in the prior art have in common that so far no microfluidic system could be provided which was autonomous, d. H. without supply of electrical energy, works, leaving a self-regulating heat and cooling circuit allows becomes.

These Task is by the method of transporting liquids with the features of claim 1, the thermal capillary pump with the Features of claim 7 and the microfluidic refrigeration cycle solved with the features of claim 13. In claim 16 and 18 are uses according to the invention specified. The further dependent claims show advantageous developments.

• a) aus einem Gemisch aus mindestens einer flüssigen und einer gasförmigen Phase die mindestens eine flüssige Phase in einem Abscheider abgeschieden und einem Reservoir zugeführt wird,
• b) mittels mindestens einer Kapillare die mindestens eine flüssige Phase in eine Verdampfungszone überführt wird, wobei der Transport der mindestens einen flüssigen Phase durch Kapillarwirkung erfolgt,
• c) der sich in der Verdampfungszone bildende Dampf einem Prozess zugeführt wird, bei dem eine zumindest teilweise Kondensation des Dampfes erfolgt und
• d) das nach dem Prozess vorliegende Gemisch aus Flüssigkeit und Dampf dem Abscheider und anschließend die mindestens eine flüssige Phase dem Reservoir zugeführt wird.

According to the invention, a method for transporting liquids in a microfluidic circulatory system is provided. This procedure is based on the following steps:

• a) from a mixture of at least one liquid and one gaseous phase, the at least one liquid phase is separated in a separator and fed to a reservoir,
• b) the at least one liquid phase is transferred into an evaporation zone by means of at least one capillary, the transport of the at least one liquid phase being effected by capillary action,
• c) the forming in the evaporation zone steam is fed to a process in which an at least partial condensation of the steam takes place and
• d) the mixture of liquid and vapor present after the process is supplied to the separator and subsequently the at least one liquid phase is fed to the reservoir.

• a) Abscheiden der Flüssigphase einer Zwei-Phasenströmung und Bereitstellung der Flüssigphase in einem Reservoir.
• b) Kontinuierliches Pumpen einer Flüssigphase mittels Kapillareffekten.
• c) Verdampfen der Flüssigphase und Austreiben der Flüssigphase aus der Kapillare.
• d) Dosierung verschiedener Stoffe durch Regelung der zugeführten Wärme.
• e) Mischen verschiedener Stoffe in der Gasphase entsprechend geforderten Mischungsverhältnissen. Dadurch sind sehr kurze Mischzeiten erreichbar.
• f) Nach dem Prozess wird das Zwei-Phasengemisch dem Abscheider zugeführt und die Gasphase abgetrennt.

The inventive method is thus based on capillary effects, together with an evaporator or evaporation. In addition to the pure function of transporting liquids, the arrangement according to the invention fulfills the following additional functions:

• a) depositing the liquid phase of a two-phase flow and providing the liquid phase in a reservoir.
• b) Continuous pumping of a liquid phase by means of capillary effects.
• c) evaporation of the liquid phase and expulsion of the liquid phase from the capillary.
• d) dosing different substances by controlling the heat supplied.
• e) mixing of different substances in the gas phase according to required mixing ratios. As a result, very short mixing times are reached bar.
• f) After the process, the two-phase mixture is fed to the separator and the gas phase separated.

The A special feature of the present invention is the self-regulating Character of the microfluidic system. Under self regulation is in the context of the present invention, a closed loop to understand without electrical signal conversion. Thus ent falls the measurement of specific parameters, as well as the signal conversion and the control of an actuator. The regulation takes place in that, depending on the supplied to the evaporator Heat sets the amount of steam generated directly can be.

Of the Transport of the liquid phase takes place exclusively with the help of capillary forces, which is why the supply of electrical Auxiliary power or additional actuators is not necessary. In a preferred variant, however, for the system start an electric heating of the capillary in the evaporation zone be provided. By Joulescher heat is the liquid Phase preheated and evaporated. This will make the liquid Phase discharged as gas phase from the capillaries and the transport the liquid phase by capillary force is maintained.

It it is preferred that after step b) in the evaporation zone forming vapor with another gaseous substance is mixed in a mixing zone.

Preferably is the amount of the forming steam on the Heat of evaporation supplied to the evaporation zone and / or the Geometry of at least one capillary set. Regarding the geometry of the capillaries play the number of capillaries, their diameter, their length, their nature and / or their material plays a crucial role. These parameters can both individually and together are modified so that the desired amount of steam generated can be adjusted can.

Regarding the nature of the capillaries can this example porous, foamy, fibrous, sponge-like or gel-like be constructed or have corresponding areas. The capillary structure can be built in different ways. In principle exists the possibility of individual, mutually closed channels form as a capillary and this directly into the material of the thermal capillary pump or to use a capillary material that acts as a Type insert is introduced into the thermal capillary pump.

used one channels as a capillary, so may differences in the channel cross section in shape and size, z. Rectangular, circular, triangular, star-shaped, polygonal, as well as differences in length and channel guidance, z. Straight, curved, meandering, spiral, be used to correct the capillary pressure and the amount of steam adjust.

used one capillary material as capillary, so can with fibrous Materials the fiber interstices, in porous, foam-like, sponge-like and gel-like materials with each other in open composite pores are used as capillaries.

at fibrous capillary materials may have differences in Fiber cross section, z. B. round, lamellar, in the fiber structure, z. B. directed, undirected, long fibers, short fibers, cut, broken, in the fiber material itself, in fiber processing, felt, Fleece, fabric, wick, as well as in the amount to be used to the Capillary pressure and adjust the amount of steam properly.

at porous, spongy, foamy and gelatinous capillary materials Differences in pore size, the Materials, the pore size distribution, the degree porosity, compressibility and quantity be used to properly adjust the capillary pressure and the amount of steam. Materials are especially ceramics, glasses, airgel, Polymers and viscose.

It is further preferred that by means of capillary force a pressure difference between reservoir and evaporation zone or between separators and evaporation zone in the range of 1 mbar to 10 bar is generated.

A Another preferred variant provides that the liquid Phase during transport through the capillary of impurities, especially particles, is purified.

It is further preferred that the discharge of the liquid Phase from the capillary into the evaporation zone by evaporation, Evaporation, by means of a sorbent, by another Capillary with less hydraulic than the first capillary Diameter and / or done by chemical reaction.

• • ein Reservoir, gefüllt mit einem Gemisch mit mindestens einer flüssigen Phase und/oder ein Abscheider zur Abscheidung mindestens einer flüssigen Phase aus einem Gemisch aus min destens einer flüssigen und einer gasförmigen Phase,
• • eine in Verbindung mit einer Wärmequelle stehende Verdampfungszone zum Verdampfen der mindestens einen flüssigen Phase,
• • mindestens eine Kapillare zum Transport der flüssigen Phase vom Reservoir in die Verdampfungszone mittels Kapillareffekt.

According to the invention, a thermal capillary pump is likewise provided which contains the following components:

• A reservoir filled with a mixture having at least one liquid phase and / or a separator for separating at least one liquid phase from a mixture of at least one liquid and one gaseous phase,
• • one in connection with a heat source evaporation zone for evaporating the at least one liquid phase,
• • at least one capillary for transporting the liquid phase from the reservoir to the evaporation zone by capillary action.

Farther it is preferred that the at least one capillary with a porous and / or fibrous and / or foamy and / or sponge-like Material and / or a gel to increase the capillary effect at least partially filled or coated.

Preferably the at least one capillary has a hydraulic diameter in the range of 1 nm to 1000 microns. The length can be the capillary vary in the range of 1 mm to 100 cm.

According to the invention also provided a microfluidic cooling circuit, the at least one thermal capillary pump as previously described was, as well as at least one waste heat generating reactor and at least one supply line from the reactor to the reservoir.

Preferably the cooling circuit has a mixing zone to the mixture the forming in the evaporation zone steam with at least one another gaseous substance, in particular separately formed Steam, up. The mixing zone is preferably directly the Downstream evaporation zone.

Preferably the cooling circuit has a burner as a reactor Burner reformer unit on.

The Thermo-capillary pump according to the invention is preferably used in areas where specifically waste heat of a Process can be tapped. Is the temperature of the waste heat greater than the target temperature of the process (eg. B. burner in a burner reformer unit) is more liquid evaporates as a predetermined setpoint. this leads to an increased reformer activity (steam reformer) and thus to a reduction in the firing temperature. If the burner temperature is lower as the set temperature, less liquid is evaporated as the setpoint. This leads to a reduction of Reformer activity and thus to an increase the burner temperature.

In a preferred variant can for the system start a provided electrical heating of the capillary in the evaporation zone become. By Joulescher heat is the liquid Phase preheated and evaporated. This turns the liquid phase discharged as gas phase from the capillaries and the transport of the liquid phase by capillary force is maintained.

Based the following figure is the inventive Subject to be explained in more detail, without this restrict to the specific embodiment shown here to want.

In 1 the principle of the thermal capillary pump according to the invention is shown schematically. It is an integrated solution for the recirculation of a liquid phase 2 via a supply line 1 within a process 3 , Here, the deposition of the liquid phase takes place first 2 a 2-phase flow 5 in a separator 4 , Through capillaries 6 becomes the liquid phase 2 then by capillary force continuously into the evaporator 7 pumped. In the evaporator 7 then the evaporation of the liquid phase takes place. About another supply line 8th a dosage of the steam, which takes place in a mixing zone 9 is transferred, in which this steam can be mixed with another steam, in the present image from another thermal capillary pump. This thermal capillary pump has a reservoir 12 instead of a separator 4 on, but is otherwise identical. The mixed vapors are then sent to the process via a supply line 10 fed again.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 5303768 [0006]
• EP 142797131 [0007]

Cited non-patent literature

• M. Zimmermann et al .: "Continuous flow in open microfluidics using controlled evaporation", Lap Chip, 2005, 5, 1355-1359 [0003]
• - F. Heuck et al. "Evaporation-based micro-pump integrated into a scanning force microscope sample", Microelectric Engineering 85, (2008), 130-1305 [0004]
• Juncker et al .: Autonomous Microfluidic Capillary System, Anal. Chem. 2002, 74, 6139-6144 [0005]

Claims (21)

Method for transporting liquids in a microfluidic circulatory system in which a) from one Mixture of at least one liquid and one gaseous Phase the at least one liquid phase in a separator separated and fed to a reservoir, b) by means of at least one capillary, the at least one liquid Phase is transferred to an evaporation zone, wherein the transport of the at least one liquid phase by capillary action, c) located in the evaporation zone forming steam is fed to a process in which a at least partial condensation of the steam takes place and d) the mixture of liquid present after the process and steam the separator and then the at least a liquid phase is supplied to the reservoir. Method according to claim 1, characterized in that that after step b) the vapor forming in the evaporation zone with another gaseous substance in a mixing zone is mixed. Method according to one of the preceding claims, characterized in that the amount of the forming vapor over the heat supplied to the evaporation zone and / or the geometry of the at least one capillary, in particular the Number of capillaries, their diameter, their length, their nature and / or their material is set. Method according to one of the preceding claims, characterized in that by means of capillary force a pressure difference between reservoir and evaporation zone or between separator and Evaporation zone is generated in the range of 1 mbar to 10 bar. Method according to one of the preceding claims, characterized in that the liquid phase during the transport through the capillary of impurities, in particular Particles, being cleaned. Method according to one of the preceding claims, characterized in that the discharge of the liquid Phase from the capillary into the evaporation zone by evaporation and / or evaporation and / or by means of a sorbent and / or through another capillary with respect to the first capillary smaller hydraulic diameter and / or by chemical reaction he follows. Thermo-capillary pump containing • a reservoir ( 12 ) filled with a mixture having at least one liquid phase and / or a separator for separating at least one liquid phase from a mixture of at least one liquid and one gaseous phase, • an evaporation zone connected to a heat source (US Pat. 7 ) for vaporizing the at least one liquid phase, • at least one capillary ( 6 ) for transporting the liquid phase from the reservoir ( 12 ) into the evaporation zone ( 7 ) by capillary effect. Thermo-capillary pump according to claim 7, characterized in that that the at least one capillary with a porous and / or fibrous and / or foamy and / or spongy material and / or a gel for increasing the capillary effect at least partially filled. Thermo-capillary pump according to claim 7 or 8, characterized characterized in that the at least one capillary is a hydraulic Diameter in the range of 1 nm to 1000 microns has. Thermo-capillary pump according to claim 7 to 9, characterized characterized in that the at least one capillary is a length ranging from 1 mm to 100 cm. Thermo-capillary pump according to one of the claims 7 to 10, characterized in that between reservoir and evaporation zone or between the separator and the evaporation zone by means of capillary forces produced pressure difference in the range of 1 mbar to 10 bar is present. Thermo-capillary pump according to one of the claims 7 to 11, characterized in that the pump is a device for the purification of the liquid phase during the Transport of impurities, especially particles has. Thermo-capillary pump according to one of the preceding Claims, characterized in that the liquid from the capillary thermally by means of waste heat of a process is discharged at the end of the capillary in the region of the evaporation zone. Thermo-capillary pump according to one of the preceding Claims, characterized in that the liquid from the capillary thermally via Joule'scher over heat an electrically heated zone at the end of the capillary in the area of Evaporation zone is discharged. Microfluidic cooling circuit comprising at least one thermal capillary pump according to one of claims 7 to 14, at least one waste heat-generating reactor ( 3 ) and at least one feed line from the reactor ( 3 ) to the reservoir ( 4 ). Cooling circuit according to claim 15, characterized in that the cooling circuit, the evaporation zone ( 7 ) downstream of a mixing zone ( 9 ) for mixing the steam forming in the evaporation zone with at least one further gaseous substance, in particular separately formed steam. Cooling circuit according to one of the claims 15 or 16, characterized in that the reactor is a burner a burner reformer unit. Use of the thermal capillary pump after one of claims 7 to 14 in microsystems technology, the micro process engineering, in particular in fuel cell systems, in particular portable Fuel cell systems. Use according to claim 18 in process engineering Systems and / or installations for evaporation and / or evaporation at least a liquid phase and / or for humidification of a gas. Use of the cooling circuit according to one of Claims 15 to 17 in microsystems technology, the micro process engineering, in particular in fuel cell systems, in particular portable Fuel cell systems. Use according to claim 20 in process engineering Systems and / or installations for evaporation and / or evaporation at least a liquid phase and / or for humidification of a gas.