Device forming a manometer intended for measuring biphase fluid pressure, associated method of manufacture and fluidic network

The present invention relates to a device that forms a manometer for measuring the pressure of a two-phase fluid in a fluid network.

The present invention allows for significant reductions in dimensions and incorporation into fluid networks with respect to improving the sensitivity of manometers.

Applications covered by the present invention are, in particular, two-phase fluid heat exchangers, fuel cells, or other systems involving the use of two-phase mixtures operating around atmospheric pressure.

In systems such as two-phase fluid exchangers or fuel cells, the liquid and gas phases of a given fluid co-exist in a fluid network that supports heat and mass exchange.

The fluid pressure and the mass flow rate (titration concentration) between the gas and liquid phases of a two-phase fluid are parameters that constantly reveal the operating efficiency of the system, as well as their respective distributions in the fluid network.

Therefore, accurate information on these parameters in real time and at critical points in the fluid network (hot points, dryout points, clogging points) makes it possible to prevent failure / deterioration and to control the way the system operates. Allows you to modify / adjust.

In other words, it is desired that devices for accurate measurement of these parameters (particularly pressure) be incorporated directly into the fluid network of the system described above without compromising system operation or miniaturization.

It is known to measure the pressure of a liquid using a manometer.

In particular, it is known to measure the pressure of a liquid by measuring the displacement of the liquid meniscus in the capillary.

Patent Document 1 states that the measurement sensitivity is 10.⁴Measurement of the pressure difference by measuring the displacement of the liquid meniscus at the interface with the air bubbles injected by a syringe to double the pressure has been proposed. The dimensions of the proposed measuring device are macroscopic and cannot be incorporated into the fluid network of small systems. Also, the minimum observable displacement of the meniscus is on the order of 0.1 mm, and it is necessary to use optical means outside the sensing element of an appropriate manometer.

<p><patcit num="1"><text>U.S. Pat. No. 4,484,855</text></patcit></p>

<p> Therefore, an object of the present invention is to incorporate a device for accurate measurement of pressure of a two-phase fluid into a fluid network of a system such as a heat exchanger or a fuel cell without impairing the operation and miniaturization of the system. Propose a solution that makes it possible.</p>

<p> Therefore, the object of the present invention is a device that forms a manometer for measuring the pressure of a two-phase fluid in a fluid network. -The first channel (where a two-phase fluid can flow inside), -Including a second channel leading to the first channel, the second channel is a blind, each dimension of which is less than or equal to the length of the capillary of the fluid phase and its lengthwise wall. Has a surface energy gradient that decreases from its inlet to the end, and the surface energy gradient increases the wetting angle of the fluid's liquid phase meniscus in the blind channel from its inlet to the end. Can be done.</p><p> Capillary length is a characteristic dimension of a liquid in the context that capillary force and gravity are of the same strength. In the case of water, the capillary length lc and the capillary volume vc have the following values, respectively:<maths num="1"><img file="JP2013525791A_D0001.tif" /></maths>as well as<maths num="2"><img file="JP2013525791A_D0002.tif" /></maths></p><p> Therefore, in the present invention, for a given liquid, each dimension constructed by the hydraulic diameter and the length of the blind channel (blind tube) is less than or equal to the length of the liquid capillary.</p><p> Therefore, according to the present invention, the formation of a blind channel directly connected to the channel (main channel) of the fluid network, and the addition of a surface energy gradient along its lengthwise wall, creates a liquid meniscus at the interface with the gas phase. It will be possible to place it accurately.</p><p> The displacement of this meniscus depends on the pressure of the fluid at the inlet of the blind channel.</p><p> In fact, the inventor's starting point was to observe in a liquid manometer that the displacement of the meniscus at the interface with the air bubbles under pressure is affected by the wetting of the liquid in contact with the walls of the capillaries. ..</p><p> Therefore, the inventor sought to more accurately test this effect from blind channels in which the fluid co-existed in the liquid and gas phases. Air can also be present in the gas phase.</p><p> This configuration is shown in Figure 1.</p><p> The force equilibrium relationship can be described as:<maths num="3"><img file="JP2013525791A_D0003.tif" /></maths>here: P_liquidIs the pressure of the liquid; P_gasIs the pressure of the gas; W is the width of the blind channel; H is the height of the blind channel; σ is the surface tension constant of water (~ 72mJ / m)²) And; θ_eIs the wetting angle of water on the lengthwise wall 11 of blind channel 1.</p><p> If you write this expression in another way:<maths num="4"><img file="JP2013525791A_D0004.tif" /></maths>And here, ΔP = P_liquid-P_gasAnd D_hIs the hydraulic diameter,<maths num="5"><img file="JP2013525791A_D0005.tif" /></maths>Is defined as.</p><p> The pressure of the gas confined in the cavity 10 is the ideal gas equation.<maths num="6"><img file="JP2013525791A_D0006.tif" /></maths>Asked by, where P_atmIs atmospheric pressure; L₁Is a flat meniscus (cosθ)_e= 1) and the distance between the end of cavity 10; y is the position of the liquid (water) meniscus at the interface with the gas.</p><p> When both terms of equation (2) have the same order strength, the wetting effect is considered to be remarkable.</p><p> Figure 2 shows a typical curve of pressure difference as a function of hydraulic diameter. The region above this curve is the region with low wet sensitivity, and the region below this curve is the region with high wet sensitivity. For example, at a hydraulic diameter of 2 μm, the wetting effect is remarkable when the pressure difference is 1.1 bar or less.</p><p> Next, the present inventor studied the effect of the contact angle (wetting angle) on the displacement y of the liquid meniscus at the interface with the gas.</p><p> The contact angle is constant, that is, cosθe = K (5') Then we get the following relation:<maths num="7"><img file="JP2013525791A_D0007.tif" /></maths>Therefore,<maths num="8"><img file="JP2013525791A_D0008.tif" /></maths>Will be.</p><p> Figures 3A to 3C show three configurations of liquid contact angles with different values of 20 °, 90 °, and 120 °, respectively, with feature dimensions H and L.₁, L₂It is shown.</p><p> Assuming a linear change in the cosine of the contact angle along the lengthwise wall of the blind channel, cosθ_e= K₁y (7) And here,<maths num="9"><img file="JP2013525791A_D0009.tif" /></maths>Is.</p><p> Substituting equations (2) and (3) into (1) gives the following relational expression:<maths num="10"><img file="JP2013525791A_D0010.tif" /></maths>here,<maths num="11"><img file="JP2013525791A_D0011.tif" /></maths>Is.</p><p> Therefore, the following relational expression can be obtained.<maths num="12"><img file="JP2013525791A_D0012.tif" /></maths></p><p> Assuming a quadratic change in the cosine of the contact angle along the lengthwise wall of the blind channel, cosθ_e= K₂y² (16) And here,<maths num="13"><img file="JP2013525791A_D0013.tif" /></maths>Is.</p><p> Therefore, for the position y of the meniscus, the following relational expression is obtained:<maths num="14"><img file="JP2013525791A_D0014.tif" /></maths></p><p> Next, the inventor conducted a comparative study and selected the following numerical examples: -Analytical pressure range of 1-2 bar, for high wet sensitivity, -L₁= L₂= 100 μm, -H = W = 1 μm channel depth and width, -Length L₂Angle θ in the range 0 ° to 90 ° from the entrance of the blind channel at_e -Angle in the range 90 ° to 150 ° at length L1 to the end of the blind channel θ_e。 </p><p> Figure 4A shows the angle θ as a function of the position y of the liquid meniscus._eThe typical curve of the cosine of is shown.</p><p> FIG. 4B shows a typical curve of the meniscus position y as a function of pressure P.</p><p> FIG. 4C shows a typical curve of the sensitivity of meniscus displacement as a function of pressure P.</p><p> Therefore, based on this analysis, the present inventor substantially increases the measurement sensitivity of the manometer (its measurement principle is the position of the liquid meniscus) by changing the wetting angle (contact angle). I came to the conclusion that I can do it.</p><p> In other words, the inventor has concluded that the use of surface energy gradients can increase the measurement sensitivity of the manometer compared to the case of hydrophobic surfaces with constant surface energy. The inventor has also concluded that this increase in measurement sensitivity is even more important for quadratic angular cosine gradients as compared to linear cosine gradients.</p><p> Therefore, due to its high measurement sensitivity, the device according to the invention can be of microscopic dimensions for relatively small pressure changes (typically on the order of 1 bar). Therefore, the present invention can be incorporated into the fluid network without impairing the miniaturization and operation of the fluid network.</p><p> Since a surface energy gradient is given over at least one of the lengthwise walls, multiple parameters can be changed, such as changes in the chemical composition of the material on the surface of the lengthwise walls, changes in the structure of the lengthwise walls. Changes in the structure on the micrometer or nanometer scale include changes in the shape (depth, width) of the cavities forming the surface structure of the wall, changes in the density of the cavities, and changes in the shape and density of the cavities. .. The following three solutions are assumed in principle: -A surface structure with a uniform chemical composition and a depth gradient that increases from the entrance to the end of the blind channel. -Chemical composition gradient from inlet to end of blind channel and uniform surface structure, -A surface structure with a chemical composition gradient and a uniform depth gradient from the inlet to the end of the blind channel.</p><p> For microscopic devices built into fuel cells or two-phase fluid heat exchangers, the horizontal dimension (or hydraulic diameter) of the blind channel is 50 nm to 5 μm to measure pressure changes of 0.5 bar or more. It can be between (Fig. 2).</p><p> The length of the blind channel can be between 50 nm and 500 μm.</p><p> The blind channel can be a cross section of a substantially rectangular shape (ie, rectangular or similar in shape with / without ridges (polygon / oval)).</p><p> Means for measuring the position of the liquid meniscus to determine the pressure of the fluid are advantageously incorporated partially within the blind channel.</p><p> In an advantageous embodiment, the measuring means comprises two electrodes arranged on two portions of a longitudinal wall facing each other, each extending from the inlet to the end of the blind channel, where the electrodes are blind. Together with the two-phase fluid present in the channel, it forms a variable capacitance capacitor.</p><p> Pressure measurements are determined by the position of the equilibrium liquid meniscus in the blind channel. The meniscus determines the liquid / gas volume ratio that changes within the channel depending on its location. This volume ratio or change thereof can be determined by electrical measurement of the average volume of the two-phase fluid in the channel.</p><p> The use of two facing electrodes makes it possible to measure the capacitance of a fluid.</p><p> FIG. 5 shows the installation of the two electrodes 20 and 21. These electrodes are arranged parallel to each other at the top and bottom of the blind channel 1.</p><p> The distance between the two electrodes is close to the depth of the hydraulic diameter of the manometer.</p><p> The length and width of the electrodes are the length and width of the manometer. The total capacitance is the sum of the capacitance of the gas phase and the liquid phase of the two-phase fluid. C_t= C_l+ C_v (20) And here,<maths num="15"><img file="JP2013525791A_D0015.tif" /></maths>And ε₀Is the absolute vacuum permittivity (ε)₀=8.854×10^-12) And ε_lAnd ε_vIs the relative permittivity in water and air, respectively.</p><p> Therefore, the total capacitance is given by the following relation:<maths num="16"><img file="JP2013525791A_D0016.tif" /></maths></p><p> 12A and 12B show the total capacitance as a function of the ratio (W / H) between the lateral dimensions of the blind channel. FIGS. 12C and 12D show that the higher the ratio, the higher the measurement sensitivity. In reality, this ratio is greater than or equal to 1.</p><p> Those skilled in the art will, of course, take into account changes in the relative permittivity of liquid phases such as water as a function of temperature.</p><p> The present invention also relates to a method of manufacturing the device forming the manometer described above, in which the following steps are performed; a / The step of forming the first longitudinal portion of the blind channel within the substrate plate containing the first portion of the main channel through which the two-phase fluid can flow, b / Steps to create a surface energy gradient within the first part of the blind channel, c / Steps to form the second longitudinal portion of the blind channel within the other substrate plate containing the second portion of the main channel through which the two-phase fluid can flow (first and second length of the blind channel) The vertical part is of the same length), The step of aligning both lengthwise and main channel portions of the d / blind channel and transferring one substrate plate to the other substrate plate, e / Steps to secure both substrate plates to each other.</p><p> Compositions having a chemical gradient according to steps b / and d / can be obtained by known methods such as the SAM (SELF-ALIGNED-MOLECULE) method, first layering a layer of hydrophobic molecules of the channel. Deposit on the surface. The hydrophobic layer is then partially removed by plasma or laser ablation to locally expose the hydrophilic substrate. The reverse is also possible, that is, a layer of hydrophilic molecules on the hydrophobic substrate.</p><p> Therefore, surface chemical gradients can be created by controlling the etching / ablation design. This gradient can also be obtained by vapor deposition of functional molecules.</p><p> According to one variant, the same surface energy gradient is generated on the second longitudinal portion of the blind channel prior to step d /.</p><p> Since the electrodes are incorporated as measuring means, a thin metal layer is advantageously deposited prior to each of step b / and step d / to construct electrodes in each longitudinal portion of the blind channel. The electrodes can be deposited in thin layers by a PVD-type vacuum deposition method for metals such as Ti and Cu.</p><p> If the plate is conductive, an electrical connection element with electrodes can be formed on the back surface. If not, connection paths can be formed simultaneously using the same methods as for electrodes.</p><p> Also, depending on the configuration of the plate (whether conductive or not), one or more electrically insulating layers (eg SiO)₂, TiO₂Etc.), which electrically insulates a capacitor composed of electrodes and a two-phase fluid.</p><p> The present invention also relates to a fluid network incorporating one or more devices forming the above-mentioned manometer.</p><p> The present invention also relates to a fuel cell incorporating such a fluid network, in which at least one of a plurality of nanometers can measure the water pressure generated at the cathode or anode.</p><p> Finally, the present invention relates to a two-phase fluid heat exchanger capable of passing from liquid phase to gas phase, which heat exchanger includes such a fluid network, at least one of a plurality of manometers is the pressure of the fluid. Can be measured.</p><p> Other advantages and features of the present invention will become more apparent by reading the detailed description for illustrative purposes and not limiting, with reference to the accompanying drawings.</p>

<figref num="1">A schematic longitudinal sectional view of the blind channel 1 of the device according to the present invention is shown.</figref><figref num="2">A typical curve of the change in pressure difference according to the hydraulic diameter of the blind channel of the device according to the present invention is shown.</figref><figref num="3">The configuration of the three different contact angles is represented by a longitudinal sectional view of the blind channel of the device according to the present invention.</figref><figref num="4A">Angle θ as a function of the position y of the liquid meniscus in the blind channel_eThe typical curve of the cosine of is shown.</figref><figref num="4B">As a function of pressure P, a typical curve of the position y of the meniscus is shown.</figref><figref num="4C">As a function of pressure P, a typical curve of the sensitivity of meniscus displacement is shown.</figref><figref num="5">The installation of two electrodes as a means for measuring the position of the liquid meniscus in the blind channel of the device according to the present invention is shown.</figref><figref num="6">It is a schematic diagram of the device which concerns on this invention.</figref><figref num="7">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="8A">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="8B">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="9A">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="9B">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="10A">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="10B">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="11A">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="11B">The steps of forming a blind channel of the device according to the present invention are shown.</figref><figref num="12A">According to the value of the ratio between the dimensions of the blind channel, a typical curve of the change in capacitance of the two-phase fluid is shown as a function of the pressure and the position of the liquid meniscus in the blind channel of the device according to the present invention.</figref><figref num="12B">According to the value of the ratio between the dimensions of the blind channel, a typical curve of the change in capacitance of the two-phase fluid is shown as a function of the pressure and the position of the liquid meniscus in the blind channel of the device according to the present invention.</figref><figref num="12C">According to the value of the ratio between the dimensions of the blind channel, a typical curve of the change in capacitance of the two-phase fluid is shown as a function of the pressure and the position of the liquid meniscus in the blind channel of the device according to the present invention.</figref><figref num="12D">According to the value of the ratio between the dimensions of the blind channel, a typical curve of the change in capacitance of the two-phase fluid is shown as a function of the pressure and the position of the liquid meniscus in the blind channel of the device according to the present invention.</figref>

Since FIGS. 1 to 5 have been described above, they will not be described below.

The device forming the manometer according to the present invention is for measuring the pressure of the two-phase fluid F.

The device includes a blind channel 1 leading to the main channel 3 of the fluid network (open or closed through which the two-phase fluid F flows). This blind channel 1 forms an integral part of the network.

Each dimension (length, depth, width) of the blind channel 1 is less than or equal to the capillary length of the liquid phase of the fluid.

At least one of the lengthwise walls 11 of the blind channel 1 has a surface energy gradient that decreases from its entrance to its end.

Therefore, according to the present invention, the surface energy gradient can increase the wetting angle of the meniscus of the liquid phase of the fluid from its inlet to its end in the blind channel.

Figures 7 through 11B represent the various manufacturing steps of the device.

The first longitudinal portion 110 of the blind channel is formed within the substrate plate 4 containing the first portion 30 of the main channel through which the two-phase fluid can flow.

A metal layer is deposited to form an electrode 20 on the first portion 110 with its connection 200. Then, a surface energy gradient 112 is generated on the surface of the electrode 20 (plan view of FIG. 7, cross-sectional view of FIGS. 8A to 11B).

Similarly, the second longitudinal portion 111 of the blind channel is formed within the substrate plate 5 containing the second portion of the main channel through which the two-phase fluid can flow. Also, a metal layer is deposited to form the electrode 21 with its connection. Then, the same surface energy gradient is generated on the second portion 111 of the blind channel 1.

The first longitudinal portion 110 and the second longitudinal portion 111 of the blind channel are of the same length.

Then, both lengthwise portions 110 and 111 of the blind channel and both portions of the main channel are aligned and one substrate plate 5 is moved onto the other 4 (FIGS. 8A, 9A, 10A, 11A). ).

Finally, the steps of fixing both substrate plates 4 and 5 to each other are performed (FIGS. 8A, 9B, 10B, 11B).

Various methods are envisioned for the generation of energy gradients, for example, two identical gradients facing each other (FIGS. 8A and 8B).

Alternatively, it is assumed that one of the walls has no slope and has a constant surface energy (either hydrophilic or hydrophobic) (in FIGS. 9A and 9B, the first of the blind channels). Part 110 has no energy gradient and in FIGS. 10A and 10B the transferred second part 111 has no energy gradient).

It is also assumed that one longitudinal wall has a predetermined surface energy gradient and the other facing longitudinal walls have different surface energy gradients (in FIGS. 11A and 11B, the first of the channels). Part 110 has a surface energy gradient 112, while the second portion 111 has a different surface energy gradient 112').

The curves in FIGS. 12A and 12B show the position of the water meniscus (liquid phase) at the interface between pressure and air and water vapor (gas phase) in the blind channel, respectively, according to the ratio (W / H) between the lateral dimensions. The change in total capacitance with respect to and is shown.

Although the two-phase fluid in which the liquid phase is water and the gas phase is air and water vapor has been described, the present invention can be applied to various other two-phase fluids.

Similarly, other forming methods for forming the blind channel of the device according to the present invention are also envisioned. Therefore, replication by machining aluminum or steel substrates, lithography and etching of silicon substrates, injection or embossing of polymer substrates is envisioned.

1 blind channel 3 main channel 4, 5 board plate 10 cavities 11 Length direction wall 20, 21 electrodes 110, 111 Length-wise portion of blind channel 112 Surface energy gradient