JPH0579695A - Liquid heater - Google Patents

Abstract

PURPOSE:To obtain a compact liquid heater which can heat with high thermal efficiency surely without contaminating liquid to be heated and has a high heating capacity. CONSTITUTION:A passage 2 surrounded by a quartz glass tube 5 is provided inside a tubular ceramic heater 4 which irradiates with a far infrared ray and has PTC characteristics. A passage 3 formed between concentrically disposed quartz glass tubes 6 and 7 is provided outside the heater 4 to constitute a liquid heater 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid heating apparatus which can efficiently and continuously heat a liquid to be heated such as pure water without being contaminated and which is compact even under a heavy load.

[0002]

2. Description of the Related Art In many industrial fields, there is a demand for a liquid heating device that can heat a liquid to be heated efficiently without being contaminated by impurities or dust eluted from the wall of a flow path and is compact and inexpensive even under a heavy load. There is.

As a conventional electric resistance heating type liquid heating apparatus, one in which a rod-shaped heater, a plate-shaped heater or a coil-shaped heater is placed inside the liquid tank, or one in which a heating element is incorporated in the wall of the liquid tank, etc. It has been known. In the case of this throw-in heater, there is an example in which a heating element of nichrome wire is enclosed in quartz glass, for example.
In recent years, PTC characteristics, that is, a type in which a fluid is flown through a honeycomb ceramic heater whose temperature coefficient of electric resistance is a positive number, or a plate-shaped electric heater in which the flow path of the liquid to be heated is in close contact Have been proposed.

In Japanese Unexamined Patent Publication (Kokai) No. 57-204744, a heating element is vapor-deposited on the surface of a cylindrical ceramic, and the heating resistor is covered with a thin ceramic sheet to prepare a cylindrical heating element. An electric water heater that uses both inner and outer surfaces as heating surfaces, generates a swirling flow in the outer flow path of the cylindrical heating element to improve heat exchange efficiency, and has a uniform temperature distribution on the heating element surface. Is disclosed. When the liquid to be heated has conductivity such as water or electrolyte solution, the insulating material is lined in the flow path of the liquid to be heated as in this example, and the space between the liquid to be heated and the heater is An insulated one is used.

Further, in Japanese Patent Laid-Open No. 1-98854, a first space, a second space, and a third space are formed from the inside by a triple pipe arranged concentrically, and the first space, the second space, and the third space are formed in a second space having a cylindrical shape. Generates arc plasma and heats arc plasma first
Disclosed is an electric heating instantaneous water heater that transfers heat to water to be heated flowing in a space and a second space. In this case, there is no description of what is used for the material of the tube, but it is considered that the two inner tubes are made of an electrically conductive material because of its configuration.

[0006] Recently, a technique of using chemically and physically purified pure water instead of CFC for cleaning intermediate products of electronic products such as semiconductor devices has begun to be adopted, and pure water is completely polluted. There is an increasing need for a liquid heating device that can heat without heating.

[0007]

However, in the conventional liquid heating apparatus using the rod-shaped or linear heater, the heat transfer area between the liquid and the heater cannot be increased, so that the heat generation capacity cannot be increased, and the heater cannot be used. Since it is necessary to use many heaters or long heaters, it is difficult to make the heater compact.

When a plate-shaped heater is used, it is difficult to increase the heat generation capacity of the heater with a conventional small heater, and it is difficult to manufacture a liquid heating device that is compact and has a high heat generation capacity. Further, when a honeycomb ceramics heater is used, there is a drawback that the thermal efficiency is small by the amount of heat radiated from the periphery of the honeycomb ceramics heater.

Further, when the liquid to be heated has conductivity such as water or an aqueous solution of electrolyte, there is a problem of electric leakage and the honeycomb heating element cannot be used in a bare state. Attempts have been made to insert an insulating tube. However, considering that it is indispensable to bind the tubes at the entrance and exit of the tube to insert the tubes into a large number of through holes, it is complicated and takes a lot of time and labor, and the liquid heating device cannot be manufactured at low cost. There are difficulties.

In addition, there is a great demand for a liquid heating device that can heat a liquid to be heated without polluting the liquid to be heated, for example, when heating ultrapure water. The liquid heating device that holds the liquid at a desired temperature is bulky, it takes time to obtain a liquid at a predetermined temperature, and the thermal efficiency is not good, and it does not pollute the liquid to be heated, it has good thermal efficiency, and it is compact. There has been a strong demand to provide an inexpensive liquid heating device that can be used with high load and at a reasonable price.

The present invention solves these drawbacks of the prior art, does not pollute the liquid to be heated at all, is compact, has a high load and high thermal efficiency, requires little waiting time, and is inexpensive and easy to use. It is intended to provide a device.

[0012]

The present invention has been made as a result of various investigations for solving the above-mentioned problems, and the liquid heating apparatus of the present invention is close to the inside and the outside of a resistance heating tubular ceramics heater. Then the flow path of the liquid to be heated is arranged,
A flow path of the liquid to be heated inside the tubular ceramics heater is formed by being surrounded by a first quartz glass tube which is concentrically arranged inside the tubular ceramics heater. A flow path is formed between second and third quartz glass tubes which are concentrically arranged outside the tubular ceramic heater.

In the present invention, the quartz glass is a glass obtained by melting quartz glass having high purity and vitrifying it, or a silica glass made from silica synthesized by hydrolyzing silicon tetrachloride (SiCl ₄ ). I mean.

In the liquid heating apparatus of the present invention, the inner and outer surfaces of the resistance heating tubular ceramics heater are provided close to the inside and the outside of the resistance heating tubular ceramics heater, so that both inner and outer surfaces of the tubular ceramics heater are used as heat transfer surfaces. Therefore, a large heat transfer area can be taken, and heat transfer to the liquid to be heated effectively utilizes both heat transfer through the wall of the quartz glass tube and radiant heat transfer by heat radiation from the tubular ceramics heater. Heat transfer is good, and because the heat generation part of the tubular ceramics heater is almost entirely surrounded by the flow path of the liquid to be heated, the heat from the inner and outer surfaces of the heater is not completely transferred to the liquid to be heated. Therefore, the thermal efficiency is excellent.

In the liquid heating device of the present invention, the inner and outer surfaces of the tubular ceramics heater are insulated from the liquid to be heated by quartz glass, so that the liquid to be heated is a conductive liquid such as water or aqueous solution. Can be used as is.

Further, in the liquid heating apparatus of the present invention, the liquid flow path is entirely made of quartz glass, and the quartz glass has good corrosion resistance to corrosive liquids other than hydrofluoric acid, and the liquid to be heated contains impurities. It is a material that does not get dirty with dust and
Since quartz glass made of high-purity material is available on the market, a liquid heating device suitable for heating ultrapure water used in semiconductor manufacturing processes, etc., that can heat a liquid to be heated without contaminating it at all is provided. It can be provided relatively inexpensively.

Since quartz glass is resistant to corrosion by acid, even if the channel is contaminated, it can be regenerated by acid cleaning. In addition, quartz glass has sufficient heat resistance required for the material adjacent to the ceramic heater in the liquid heating device, and its coefficient of thermal expansion is extremely small, so it will be damaged even if it is subjected to rapid heating or rapid cooling during use. Since it has no infrared rays and has good infrared transparency, it can effectively use the radiant heat transfer from far infrared rays radiated in large amounts from the ceramics heater for good heat transfer, so it usually heats the ceramics heater that emits a lot of infrared rays. It is a material of the flow channel which is particularly suitable for the liquid heating device of the present invention used as a source.

However, when quartz glass is heated at 700 ° C. or higher for a long time, it tends to be devitrified (crystallized) and deteriorate in quality. Therefore, it is preferable that the temperature of use is not so high. When devitrification occurs, dust is emitted, which may cause contamination of the liquid to be heated, so it is necessary to pay attention. In this sense, it is preferable to use the tubular ceramic heater at a temperature of about 600 ° C. or lower.

In addition to quartz glass, the most effective materials used for the flow path include PTFE as a fluororesin and borosilicate glass as a heat-resistant glass. However, even if a small amount of PTFE is used, it is heated pure water. It is unavoidable that the organic matter will dissolve out and dust will be generated at the same time, so it is not suitable for the purpose of heating pure water.

Further, since the heat resistance of PTFE is as low as about 300 ° C. and the thermal conductivity is not so good, it is not possible to raise the temperature of the tubular ceramic heaters arranged adjacent to each other, and the flow rate of PTFE cannot be increased. When the channel material is used, the liquid to be heated is not polluted at all, and a compact and high heating capacity liquid heating device cannot be constructed.

When borosilicate glass is used for the flow path of the liquid to be heated, its heat resistance is about 600 ° C., so that the temperature of the tubular ceramics heater is limited to a low level, and although the coefficient of thermal expansion is small, quartz glass is used. Since it is much larger than that, thermal stress cracking may occur if it is rapidly heated or rapidly cooled. Even though the corrosion resistance is relatively good, the release of extremely small amounts of impurities and dust cannot be prevented when the temperature of the liquid to be heated rises, so it is recommended for other than normal applications in which very small amounts of impurities and dust are acceptable. Not used.

In a preferred aspect of the liquid heating apparatus of the present invention, the material of the tubular ceramics heater is made of metallic silicon and a metal oxide containing alumina and silica as main components, and the content of metallic silicon in the material is 5 to 5. It is 50% by weight.

Since the material of the tubular ceramics heater is such that the main components are metal silicon and metal oxide, and the content of metal silicon is 5 to 50% by weight, the material of the ceramics heater is Has a positive temperature coefficient of electric resistance, and the conventional barium titanate PT
A heater made of C material (ceramics with a positive temperature coefficient of electrical resistance) can heat up to about 300 ℃ at most due to its characteristics, while it can easily be heated up to about 600 ℃ and has a temperature of electric resistance. Since the heating element has a positive coefficient, the electrical resistance increases as the temperature rises, so that there is no fear of overheating the heater, and a liquid heating apparatus with easy temperature control can be obtained.

Further, the content of metallic silicon affects the resistance characteristics of the ceramic heater, and in order to obtain a material having resistance characteristics that is easy to use as a ceramic heater, the content of metallic silicon is preferably 5 to 50% by weight. ..

The ceramic heater made of this material is a ceramic heater that radiates infrared rays (heat rays) containing a large amount of far infrared rays, and the far infrared rays emitted pass through the quartz glass tube surrounding the liquid flow path. Since it is easily absorbed by water or an aqueous solution, radiant heat transfer can be conveniently used for heat transfer when the liquid to be heated is water or an aqueous solution. A good liquid heating device can be realized.

In another preferable mode of the liquid heating apparatus of the present invention, the outer flow passage and the inner flow passage of the tubular ceramics heater are connected in series by a connecting pipe. By configuring the inner and outer flow passages to be connected in series, the temperature range in which the liquid to be heated can be controlled can be widened.

Furthermore, when a plurality of liquid heating devices are connected, the temperature of pure water is set to 80 ° C. so that drying of the object to be cleaned after cleaning can be completed quickly, such as when cleaning a silicon wafer or a magnetic disk substrate. It is said to be good, but it is easy to heat to this temperature,
A liquid heating device that is easy to use and has a wide range of applications can be provided.

In another preferable embodiment of the liquid heating apparatus of the present invention, the temperature signals of the temperature sensor attached to the inflow portion of the liquid to be heated and the temperature sensor attached to the tubular ceramics heater, the inlet of the liquid to be heated, etc. Based on the flow rate signal of the liquid to be heated flowing into the liquid heating device by the flow rate sensor attached to the heater, the electric power is controlled so as to maintain the temperature of the tubular ceramics heater at a predetermined temperature. The temperature of the liquid is adjusted.

That is, since the temperature sensor is attached to the tubular ceramics heater, the temperature of the tubular ceramics heater can be directly detected and the temperature of the tubular ceramics heater can be directly controlled. Here, the temperature of the tubular ceramics heater is controlled to a predetermined temperature which is predetermined with respect to the flow rate and the inflow temperature of the liquid to be heated. The temperature of the heated liquid obtained with respect to the holding temperature is determined as data, and the temperature of the tubular ceramics heater corresponding to the required temperature of the heated liquid is determined and controlled based on this data. With the liquid heating device having this configuration, the temperature at which the liquid to be heated flows out of the liquid heating device can be quickly controlled to a desired temperature.

There are several control methods for controlling the outflow temperature of the liquid to be heated because there are several parameters, but it may take time for the outflow temperature to converge to a desired temperature depending on the method. , There is a phenomenon that the temperature of the heated liquid that flows out changes when one parameter changes, but it takes time for the temperature to converge by controlling the temperature of the tubular ceramic heater directly, It is possible to avoid the phenomenon of vibration.

This control is preferably performed by a microcomputer. For example, the inflow amount and inflow temperature of the liquid to be heated and the temperature of the liquid to be heated to be obtained, which correspond to the temperature of the liquid to be heated, are stored in the memory of the microcomputer. The temperature of the liquid flowing out can be quickly adjusted to a desired temperature by controlling the supply power so that the temperature of the tubular ceramics heater becomes the predetermined temperature read from the data. It will be possible.

However, when the temperature data of the corresponding tubular ceramics heater is not obtained in advance, it takes some time, but the temperature of the liquid to be heated is required while monitoring the temperature of the liquid to be heated flowing out from the liquid heating device. It is also possible to set it to a different temperature.

In another preferred embodiment of the liquid heating apparatus of the present invention, the first heater provided inside the tubular ceramics heater is used.
A hollow core tube made of quartz glass is inserted into the flow path of the quartz glass tube, and an impeller is attached around the upstream end of the flow path of the fluid to be heated of the core tube, and impeller blades are attached. The core tube is concentrically fixed to the inside of the first quartz glass tube by the contact of the tip with the inner wall of the first quartz glass tube.

Since the hollow quartz glass core tube is inserted into the first quartz glass tube, the outer diameter of the flow path in the first quartz glass tube is increased to increase the heat transfer area from the tubular ceramic heater. The flow velocity of the liquid to be heated can be increased by increasing the flow velocity of the liquid to be heated, and the flow velocity of the liquid to be heated can be further increased by making the flow of the liquid to be heated into a swirl flow by an impeller attached to the core tube. Since it can be increased, it is possible to easily increase the flow velocity of the liquid to be heated flowing in the flow path to the Reynolds number of 3000 or more, which is a turbulent region where heat transfer dramatically increases, and heat transfer through the quartz glass wall Can be further promoted.

Further, since the core tube is fixed to the center of the first quartz glass tube by the presence of the impeller, the core tube is held without being shaken by the flow of the liquid, and the first quartz glass tube and the core tube are held. The width of the cross section of the flow path of the liquid to be heated formed between and is kept uniform, and the heat transfer from the inner wall of the heater is made uniform and good. It is preferable that the tip of the core tube is formed in a streamline shape such as a hemisphere so that the flow of the liquid to be heated is made uniform and the resistance of the flow is not increased.

In another preferred embodiment of the liquid heating apparatus of the present invention, the distance between the surface of the tubular ceramics heater and the surfaces of the first and second quartz glass tubes arranged in proximity to each other is 1.2 mm or less. Has been done. That is, there is a gap between the surface of the tubular ceramics heater and the surfaces of the first and second quartz glass tubes, and there is usually an air layer there. The thinner the air layer, the better the heat transfer through the air layer, so the thickness is preferably 1.2 mm or less.

The thickness of this air layer can be reduced to 0.1 mm by increasing the circularity of the inner and outer surfaces of the tubular ceramics heater and the wall of the flow path of the liquid to be heated, that is, the quartz glass tube. Although possible, it is more preferably 0.3 mm or more and 1.0 mm or less in consideration of the labor required for processing the member. By adjusting the thickness of each of the air layers, it is possible to adjust the heat transfer balance from the inside and the outside of the tubular ceramics heater.

Since the heat conductivity of the air layer is low, it is possible to further improve the heat transfer by devising a method for improving the heat transfer in this portion. For example, a liquid heating device is filled with a helium gas container. It is effective to put it inside and replace the air layer with a helium gas layer.

When heating one kind of liquid to be heated,
The larger the flow velocity of the liquid to be heated is, the larger the heat transfer is, and the easier it is to heat the liquid to be heated. Therefore, the liquid to be heated inside and outside the tubular ceramic heater can be heated. It is preferable to use the above-mentioned channels by connecting them in series with a connecting pipe.

Further, when the liquid to be heated having a low temperature is first caused to flow in the flow passage outside the tubular ceramics heater, and then the liquid to be heated which has been heated to some extent is caused to flow into the flow passage inside the tubular ceramics heater, the liquid heating device is obtained. By keeping the temperature outside the chamber low, the heat dissipation from the liquid heating device is reduced, and the effect of improving the thermal efficiency is obtained. Of course, it is also effective to coat the outside of the third quartz glass tube with a heat insulating material.

In another preferred embodiment of the liquid heating apparatus of the present invention, spacers are inserted in the vicinity of both ends of the tubular ceramics heater between the tubular ceramics heater and the first quartz glass tube, and the tubular ceramics heater is provided. The heat generating part of is completely surrounded by the flow path of the liquid to be heated,
In addition, the axial length of the heat generating portion of the tubular ceramics heater is made shorter than the length of the liquid flow path so that the spacer does not overlap the heat generating portion of the tubular ceramics heater.

The electrode portions on both ends of the tubular ceramics heater are further impregnated with metallic silicon or have their surfaces sprayed with aluminum so that the electric resistance becomes smaller than that of the heat generating portions, and even if heat is generated. Made to be slight. Then, lead wires are connected to the electrode portions at both ends and connected to a power source not shown in the drawing.

With this structure, almost all the heat-generating portion of the tubular ceramics heater is surrounded by the flow path of the liquid to be heated, which is made of a quartz glass tube, and the heat-generating portion of the tubular ceramics heater does not overlap the spacer mounting position. Since the spacer is arranged in the space, it is possible to avoid the overheating of the tubular ceramics heater caused by the spacer being a heat insulating material, thereby ensuring the durability of the tubular ceramics heater and waste from this overheated portion. It is possible to avoid dissipating heat.

As the spacer, for example, a tape having a heat resistance and an insulating property obtained by knitting a long glass fiber of E glass or a long glass fiber of quartz glass can be preferably used, and the vicinity of the end of the first quartz glass tube or a tubular ceramic heater can be used. The tape is wrapped around the end of the
A tubular ceramics heater or a second quartz glass tube is inserted on the outside thereof. The spacer keeps the distance between the surface of each quartz glass tube and the surface of the tubular ceramics heater at a predetermined narrow and even distance, absorbs the positional deviation caused by the difference in thermal expansion between both tubes, and heat transfer. Prevents partial overheating and temperature unevenness due to partial bias, or partial boiling of the heated liquid,
It fulfills the function of ensuring the durability of the tubular ceramics heater.

In the liquid heating apparatus of the present invention, since the flow paths of the liquid to be heated, which are separated by the quartz glass tube, are provided inside and outside the tubular ceramics heater, the liquid to be heated is separately provided in each liquid flow path. It is possible to simultaneously heat different liquids to be heated by flowing the liquid with a liquid heating device having a simple structure. In addition, when it is desired to obtain a liquid heating device having a larger heating capacity, the main body of the liquid heating device can be further connected in series or in parallel to form a large heating capacity liquid heating device. ..

In another preferable embodiment of the liquid heating apparatus of the present invention, the temperature sensor is a sheath thermocouple, and the sheath thermocouple is provided on the outside and the outside of the second and third quartz glass tubes which are outside the tubular ceramics heater. The tip of the sheath thermocouple is inserted into the hollow provided on the surface of the tubular ceramics heater, passing through the inside of the silica glass thin tube attached in the direction orthogonal to the axis of the tubular ceramics heater so as to penetrate the flow path. ..

As a temperature sensor for measuring the temperature of the tubular ceramics heater heated up to about 600 ° C., a sheath thermocouple is easy to use and convenient, and if a relatively thin sheath thermocouple is used, the sheath thermocouple can be used in a narrow gap. It is also possible to plug in pairs. However, the gap between the surface of the tubular ceramics heater and the surfaces of the first and second quartz glass tubes is narrow, and if a sheath thermocouple is inserted into this gap, it becomes difficult to keep the gaps even.

As one measure to avoid this difficulty, the walls of the second and third quartz glass tubes surrounding the outer flow path from the direction orthogonal to the central axis of the resistance heating tubular ceramics heater and the outer side of the tubular ceramics heater are surrounded. A quartz glass thin tube is integrally provided with the second and third quartz glass tubes so as to penetrate the flow path.
A sheath thermocouple is passed through the inside of this thin tube, and its tip is inserted into a recess provided on the surface of the tubular ceramic heater, preferably near the center.

When a quartz glass tube is used, such glass work can be carried out relatively easily, and by arranging the sheath thermocouple in this way, a space between the tubular ceramic heater and the quartz glass tube can be obtained. It is easy to keep the intervals between and narrow and even, and it is easy to attach and replace the temperature sensor.

In another preferred embodiment of the liquid heating apparatus of the present invention, the liquid to be heated is pure water. Pure water (also referred to as ultrapure water) is artificially purified water and is highly purified by chemical and physical means. Specific examples of purification means include distillation, ion exchange, adsorption with activated carbon, filtration with a membrane, and the like.

[0051]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 FIG. 1 is a cross-sectional view of a liquid heating apparatus 1 for heating one type of liquid to be heated.
A mixture of Kibushi clay and borosilicate glass, which are mixed so that ₂ O ₃ is 28% by weight, SiO ₂ is 67% by weight, and Fe ₂ O _{3 and} others are 5% by weight, is used as a metal oxide. The powder was added and mixed so that the proportion thereof was 35% by weight, methylcellulose was added as a binder to this mixture, and water was further kneaded and extruded into a tubular form, which was cut after drying, It was obtained by firing at 1350 ° C. for 4 hours in a reducing atmosphere. In this case, since the metal oxide may contain iron to some extent, it is possible to use ferrosilicon instead of silicon powder.

The flow path 2 inside the tubular ceramics heater is surrounded by the first quartz glass tube 5, and the flow path 3 outside the tubular ceramics heater is the second quartz glass tube 6.
And a third quartz glass tube 7 are formed. In this liquid heating device 1, a large amount of infrared rays (heat rays) containing far infrared rays radiated by heating the tubular ceramics heater 4 penetrate the wall of the quartz glass tube and reach the liquid to be heated flowing through the flow paths 2 and 3. By doing so, if the liquid to be heated has a property of absorbing infrared rays, the heat transfer becomes considerably good even if the tubular ceramics heater and the quartz glass tube are not in close contact with each other.

Further, a thin rod 13 of quartz glass is spirally wound around the outer periphery of the second quartz glass tube 6 just outside the tubular ceramics heater, and the liquid to be heated is in this flow path 3
It is designed to flow while rotating in a spiral. The inner channel 2 and the outer channel 3 are connected by a connecting pipe 14.

When assembling this liquid heating device,
It is recommended that the quartz glass portion and the tubular ceramics heater portion be separately prepared in advance, and that both portions be finally combined. However, it is also possible to fit the inner and outer quartz glass tubes into the tubular ceramic heater and then join them at the connecting tube.

As an example, the liquid heating device of this form was used for heating pure water. That is, a tubular ceramics heater having an outer diameter of 20 mm, an inner diameter of 14 mm, a length of 300 mm and an electric power of 10 kW when a voltage of 200 V is applied is used,
When liters of pure water was introduced from the inlet 9 of the liquid to be heated into the outer flow passage 3 and then flown into the inner flow passage 2, 30 ° C.
Water temperature rose to 44.1 ℃, the effective thermal efficiency was over 98%. Further, at this time, no contamination of pure water as the liquid to be heated by the flow path wall material could be detected.

Embodiment 2 FIG. 2 is a cross-sectional view of an example of the liquid heating apparatus of the present invention used for heating ultrapure water used for cleaning intermediate products in the manufacturing process of electronic products such as semiconductor devices. is there.

The material of the tubular ceramics heater 4 is the same as that of the first embodiment, and as in the first embodiment, the flow paths 2 for the liquid to be heated are inside and outside the tubular ceramics heater,
No. 3 is surrounded by high-purity quartz glass containing harmful impurities in the order of 1 ppm. The wall thickness of these quartz glass tubes is 1.5 to 2 mm.
The difference from Example 1 is that the diameter of the first quartz glass tube 5 arranged inside the tubular ceramics heater 4 is large, and the heat transfer area is correspondingly large.

However, when the liquid to be heated is caused to flow through the flow path 2 having the circular cross section as it is, the flow velocity of the liquid to be heated becomes slow, and the heat transfer between the liquid to be heated and the first quartz glass tube 5 becomes poor. It becomes difficult for heat to be transferred to the liquid to be heated.

Therefore, the tip end is closed and the core tube 16 made of a hollow quartz glass tube having the impeller 17 attached around the tip end is inserted into the inside of the first quartz glass tube 5 to disconnect the flow path 2. The area is reduced and the tip of the impeller 17 is arranged so as to contact the inside of the first quartz glass tube 5. Thus, the impeller 17 has a core so that the core tube 6 is not biased and the thickness of the flow passage 2 having a ring-shaped cross section is not uniform, and the core tube 6 is not pushed by the flow of the fluid to be heated and does not move. It supports the tube 6.

Since the number of blades of the impeller 17 is three and the blades are inclined in a spiral shape, a rotational force is applied to the liquid flowing in the flow path, and the flow velocity of the liquid is further increased. As a result, the number of Reynolds increases and heat transfer is further promoted. In the figure, the end surface of the core tube on the side where the impeller is attached is formed in a hemispherical shape so as to equalize the flow of the liquid to be heated and reduce the flow resistance.

By increasing the outer diameter of the flow path 2 in this way, the inner diameter of the flow path 3 is also increased, the size of the tubular ceramics heater is increased and the heat transfer area is increased, and liquid heating with a larger heating capacity is performed. It becomes possible to make a device.

On the outer periphery of the quartz glass tube 5 in the vicinity of both ends thereof, a spacer 21 formed by winding a ribbon having a width of 10 mm, which is formed by weaving long fibers of quartz glass, is attached.
A tubular ceramics heater is inserted into the outer side of 21, and the space between the inner surface of the tubular ceramics heater 4 and the outer surface of the first quartz glass tube 5 is equalized by a spacer 21 to be about 0.5 mm. There is.

The outer diameter of the tubular ceramic heater 4 is
40mm, inner diameter 32mm, total length 600mm, 50mm length of electrode part which hardly generate heat is provided at both ends so as to reach 5mm inside from the end of the outer flow path 2, respectively. A lead wire 12 connected to a power source (not shown) is attached. Further, in the central portions of the second quartz glass tube 6 and the third quartz glass tube 7, as shown in the enlarged view of FIG. A thin tube 22 is attached, and a temperature sensor 23 formed of a sheath thermocouple passes through the inside of the thin tube 22, and a temperature sensor formed of a sheath thermocouple is formed in a recess 24 provided on the surface of the tubular ceramics heater 4.
23 tips are inserted.

With this construction, the temperature of the tubular ceramics heater 4 can be directly detected by the temperature sensor 23, and the surface temperature of the tubular ceramics heater 4 is surely controlled so as not to rise to a temperature that causes devitrification of the quartz glass. be able to.

An attempt was made to heat pure water with this liquid heating apparatus 1. That is, the maximum output when applying a voltage of 200 V to the tubular ceramics heater 4 is 6 kW, and when pure water at 20 ° C. is flowed from the inlet / outlet pipe 11 for the liquid to be heated at a flow rate of 10 liters / min, the inlet / outlet pipe 9 The temperature of the pure water flowing out of the chamber was 28.5 ° C.

At this time, the effective thermal efficiency is 98% or more, and the temperature of the tubular ceramics heater 4 during use is 460.
The temperature of the electrode part of the heating element was about 80 ° C. Moreover, the presence or absence of contamination of pure water flowing out from the inlet / outlet pipe 9 was inspected, but no contamination of impurities was observed.

When it is desired to raise the temperature of the pure water stored in the pure water tank to a desired higher temperature, it is possible to circulate the pure water in the liquid heating device.

Embodiment 3 FIG. 4 is an explanatory view showing an application example of a liquid heating apparatus according to the present invention, which is used for heating and keeping heat of a developing solution and a fixing solution for photography. In the figure, 1 is a liquid heating apparatus main body, 31 is a pump, 33 is a developing solution reservoir, 34 is a fixing liquid reservoir, and 35 is a flow rate controller for controlling the rotational speed of the pump.

In this example, the developing solution and the fixing solution are not mixed with each other and are simultaneously heated by a liquid heating device having a simple structure, and the temperature of the solution is a temperature sensor attached to the developing solution reservoir 23 and the fixing solution reservoir 24. Detected by the flow controller 35
The rotation speed of the pump 31 is adjusted by, and the electric power supplied to the tubular ceramics heater is adjusted by an electric power control system (not shown) to adjust the liquid temperature of the developing solution and the fixing solution to a required temperature.

[0071] The dimensions of tubular ceramic heater used is an outer diameter 15 mm, inner diameter of 9 mm, a length of 100 mm, SiO ₂ is
62% by weight, 35% by weight of Al ₂ O ₃ and 3 of other oxides
To the mixed powder of clay and alkali feldspar blended so as to be wt%, metal silicon is added so that the ratio becomes 20 wt%, and the binder methyl cellulose and water are further added and kneaded, followed by extrusion molding. After being dried, it is baked at 1350 ° C. for 4 hours.

This tubular ceramic heater has an electric power of 300 W when connected to an AC power source of 100 V, and at an arbitrary room temperature, about 1 liter of developing solution and about 1 liter of fixing solution stored in both liquid reservoirs are fixed. It functioned as a liquid heating device suitable for holding each liquid at 35 ° C. This liquid heating device can be similarly used for a resist developing solution and a fixing solution that are used in the semiconductor device manufacturing process.

Embodiment 4 FIG. 5 is an explanatory view showing an example of a liquid heating apparatus of the present invention used for heating pure water used for cleaning an intermediate product of a semiconductor device. In the figure, 1 is a liquid heating apparatus main body, 15 is a power supply, 23, 28 and 29 are temperature sensors, 30 is a control computer, 31 is a pump, 35 is a flow controller, 36
Is an electric power controller, 37 is a deionized water tank, 38 is a flow sensor,
39 is a discharge port, 11 and 40 are piping.

In this example, the pure water at room temperature stored in the pure water tank 37 is sent by the pump 31, introduced through the flow rate sensor 38 into the two liquid heating devices 1 connected in series, and both liquid heating devices are heated. The temperature is raised to a predetermined temperature by the device and is discharged from the entrance / exit 39. In this example, the flow rate of pure water flowing through the flow path is detected by the flow rate sensor 38 and is controlled to a predetermined constant flow rate.

The temperature of the pure water stored in the pure water tank 37 is detected by the temperature sensor 28, and the temperature signal is stored as data in the memory of the control computer.

When the pure water starts to flow, the flow rate signal enters the control computer, the electric power is supplied to the tubular ceramics heater by the signal from the control computer, and the temperature of the tubular ceramics heater in the liquid heating device is controlled by the temperature sensor 23. The detected temperature signal is also stored as data in the memory of the control computer. Further, a temperature sensor 28 is attached to a pipe 40 provided between the liquid heating device and the liquid sensor, and a temperature sensor 29 is attached to a heated pure water outlet 39. Sent to and stored in memory as data. These data can be displayed on the display of the control computer 30 as needed.

Based on the collected data, the control computer 30 determines the temperature to be held by the tubular ceramics heater of each liquid heating device by the control program stored in the memory in advance, and determines the temperature to be held by the tubular ceramics heater. The power supplied from the power controller 36 is controlled so that

As described above, by controlling the temperature of the tubular ceramics heater of each liquid heating device to the temperature to be maintained, the temperature of the pure water flowing out from the discharge port 39 can be quickly controlled to the desired temperature. ..

In the case of a liquid heating device having a large heating capacity in which eight liquid heating devices having the same specifications as shown in Example 2 were connected in series, pure water at 20 ° C. was flowed at 10 liters / minute. While the temperature of the pure water flowing out from the outlet 39 is accurate to ± 0.5 ° C
I was able to keep it at 80 ℃. At this time, the temperatures of the tubular ceramic heaters should be approximately
The fluid to be heated was heated under a control program so that the temperature was maintained at 460 ° C and the temperature was finely adjusted by the liquid heating device arranged at the final stage. The average required power in this case was 43 kW, and the effective thermal efficiency was 97.3%.

When the heated pure water discharged from the discharge port 39 was examined for contamination, no contamination could be detected.

Comparative Example FIG. 6 is a sectional view of a comparative example of a liquid heating apparatus. This liquid heating device 1 contains 20% by weight of metallic silicon, SiO ₂ and Al ₂ O.
_A tubular ceramics heater 4 composed of 80% by weight of a metal oxide containing ₃ as a main component is provided. This liquid heating device is provided inside the tubular ceramics heater 4, and is made of a fluororesin PTFE tube 25 that encloses the flow passage 2 for the liquid to be heated, and the tubular ceramics heater 4 is almost in contact with the outside of the tubular ceramics heater 4. Fluororesin PTFE tube 26, which is arranged as a unit, a fluororesin PTFE tube 27 which is concentrically spaced apart from this tube 26, and a lead wire 12 which is attached to the electrode portion of the tubular ceramics heater. Thus, the outer flow path 3 is formed between the tubes 26 and 27. Further, 10 and 11 are inlet / outlet pipes to the flow channel 2, and 8 and 9 are inlet / outlet pipes to the flow channel 3.

The liquid heating apparatus having this structure can be used for heating many kinds of liquids including hydrofluoric acid, but the temperature of the tubular ceramics heater 4 is controlled by the heat resistance of the fluororesin.
Since it cannot be raised above 300 ° C, it is difficult to make it a liquid heating device with a high heating capacity, and when it is used to heat pure water, especially when it is desired to raise the temperature of the liquid to be heated,
It was found that it is not suitable for heating pure water because it emits a small amount of organic substances and dust into pure water.

[0083]

EFFECTS OF THE INVENTION A quartz glass tube is used as a material for a flow path, and heat from a tubular ceramics heater that radiates a large amount of far infrared rays is heated by heat transfer that effectively utilizes both heat transfer and radiation. By transmitting the liquid to the liquid, the liquid to be heated is not polluted at all, the compact and high heating capacity, the relatively simple structure and the high heating efficiency make it possible to heat multiple liquids at the same time depending on the purpose. A liquid heating device is obtained which does not require time. This liquid heating device is suitable for continuously heating pure water used in the manufacturing process of electronics-related products, and a liquid heating device having a wide range of industrial applications can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a liquid heating apparatus of the present invention.

FIG. 2 is a sectional view showing another example of the liquid heating apparatus of the present invention.

FIG. 3 is an enlarged sectional view of a mounting portion of the temperature sensor in FIG.

FIG. 4 is an explanatory diagram showing an application example of the liquid heating apparatus of the present invention.

FIG. 5 is an explanatory view of an example of the liquid heating apparatus of the present invention equipped with an automatic control system.

FIG. 6 is an explanatory diagram of a comparative example of a liquid heating device.

[Explanation of symbols]

 1: Liquid heating device 2: Flow path of liquid to be heated inside 3: Flow path of liquid to be heated outside 4: Tubular ceramics heater 5: First quartz glass tube 6: Second quartz glass tube 7: Third Quartz glass tube 8, 9, 10, 11: Pipe for inlet and outlet of liquid to be heated 12: Lead wire 13: Quartz glass rod 14: Connection tube 15: Power supply 16: Core tube 17: Impeller 21: Spacer 22: Thin tube 23 : Temperature sensor 24: Dimples 25, 26, 27: Fluorine resin tube 30: Control computer 31: Pump 33: Developer reservoir 34: Fixer reservoir 35: Flow controller 36: Electric power controller 37: Pure water tank 38: Flow sensor 39: outlet 40: piping

Claims (9)

[Claims] 1. A flow path for a liquid to be heated is arranged close to the inside and the outside of a resistance heating tubular ceramics heater, and the flow path for the liquid to be heated inside the tubular ceramics heater is concentric with the inside of the tubular ceramics heater. Second and third quartz glass tubes which are formed so as to be surrounded by the arranged first quartz glass tubes and in which the flow paths of the liquid to be heated outside the tubular ceramic heater are concentrically arranged outside the tubular ceramic heater. A liquid heating device, characterized in that it is formed between. 2. The material of the tubular ceramic heater according to claim 1, wherein the material of the tubular ceramics heater is metal silicon and a metal oxide containing alumina and silica as main components, and the content of metal silicon in the material is 5 to 50% by weight. A liquid heating device. 3. The temperature control of the liquid to be heated according to claim 1, wherein the temperature signal from the temperature sensor attached to the inflow part of the liquid to be heated and the temperature sensor attached to the tubular ceramics heater, and the temperature to be heated. Acts to maintain the temperature of the tubular ceramics heater at a predetermined temperature corresponding to the temperature at which the liquid to be heated is raised based on the flow rate signal from the flow rate sensor provided in the liquid flow path. A liquid heating apparatus that is performed by controlling electric power by a control unit. 4. The hollow quartz glass core tube according to claim 1, wherein the hollow quartz glass core tube is inserted close to the inside of the tubular ceramics heater, and is inserted into the first quartz glass tube.
An impeller is attached around the end of the core tube on the upstream side of the flow path of the liquid to be heated, and the core tube is fixed in the first quartz glass tube concentrically with the first quartz glass tube by the impeller. Liquid heating device. 5. The space between the surface of the tubular ceramics heater and the surface of the first and second quartz glass tubes, which are arranged close to each other, is 1.2 mm.
The following liquid heating device. 6. The liquid heating device according to claim 1, wherein the outer side channel and the inner side channel of the tubular ceramics heater are connected in series by a connecting pipe. 7. The spacer according to any one of claims 1 to 6, wherein spacers are inserted in the vicinity of both ends of the tubular ceramic heater between the tubular ceramic heater and the surface of the first quartz glass tube, and The heat generating portion of the tubular ceramics heater is almost completely surrounded by the flow path of the liquid to be heated which is partitioned by the first quartz glass tube and the second and third quartz glass tubes, and the spacer is at the center of the tubular ceramics heater. The liquid heating device is arranged so as not to overlap the heat generating portion formed in the portion. 8. The temperature sensor according to claim 3, wherein the temperature sensor is a sheath thermocouple, and the sheath thermocouple surrounds the liquid flow path outside the tubular ceramics heater.
In a direction orthogonal to the axis of the tubular ceramics heater, so as to penetrate the quartz glass tube and the flow path formed between them.
A liquid heating apparatus in which a tip of a sheath thermocouple is inserted into a recess provided on the surface of a tubular ceramics heater, passing through the inside of a silica glass capillary attached integrally with the second and third silica glass tubes. 9. The liquid heating apparatus according to claim 1, wherein the liquid to be heated is pure water.