JP2002323259A - Instantaneous water-heating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent water from back-flowing due to bumping and a metal pipe from becoming overheated, in an instantaneous water-heating equipment, in which the metal pipe is energized directly to instantaneously heat the water passing through the metal pipe. SOLUTION: In the water-heating equipment, there is used as a supply-water pump 2 a positive displacement pump 2 having a constant flow-rate characteristics. A throttle 10 is provided for narrowing the cross-sectional area of a pipe line 9 between the pump 2 and a water-supply port 5 of a metal pipe 3; while the necessary water flow rate, the temperature of hot water or steam, and the humidity of the steam are preset in a controller 12. An appropriate electric power necessary for the aimed values is calculated, and on the basis of an operation result, the power supplied from power-supply equipment 4 to the pipe 3 is controlled. The throttle 10 blocks back flow of water, due to sudden rise in the pressure in the pipe 3 at the occurrence of bumping. The appropriate power-supply prevents a bumping, and the water can be heated instantaneously stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an instantaneous heating device for water, in which an electric current is applied directly to a metal pipe through which water flows to instantaneously heat water to continuously generate hot water or steam.

[0002]

2. Description of the Related Art The inventors of the present invention have been researching and developing the above-mentioned instantaneous heating device for water, and have applied for a patent for some of the results (see Japanese Patent Application Laid-Open No. 2000-241022). The following issues occurred during the development process.

[0003]

That is, in the instant heating device for rapidly heating water in a small-sized metal tube, the water is evaporated and overheated on the tube wall having a high power density, so that the tube wall is sharply generated. The water vapor film causes various physical phenomena such as bumping, splashing of water droplets due to explosive rapid expansion of water, and sudden rise in pressure, making it difficult to obtain stable hot water or steam. On the other hand, the water temperature in the metal pipe is the lowest at the water supply port side, and becomes higher as the water moves to the sluice side.To efficiently heat the water, the power density of the power supplied to the metal pipe must be It is necessary to control so that it is the highest on the side and gradually decreases toward the gate. However, the pressure suddenly rises near the water supply port having the highest power density, in which case water flows backward to the water supply pump side.

[0004] When the water flows backward, steam having poor heat transfer fills the inside of the tube, so that heat cannot be taken from the tube wall, and the metal tube instantaneously becomes red hot at several hundred degrees Celsius. Subsequently, when steam is released from the sprue and the pressure drops, water is suddenly supplied to the glowing metal tube, and again explosive evaporation occurs with a sudden rise in pressure. Such unstable and destructive repetitive phenomena occur at intervals of several seconds and cannot be accommodated simply by providing a check valve in front of the water supply port. Therefore, it was considered necessary to provide a means for stably injecting water into the metal tube even when a sudden change in pressure occurs, and for appropriately controlling the electric power supplied to the metal tube so as not to cause bumping.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various experiments in order to solve such problems, and as a result, have found means that are satisfactory here. First, according to the present invention, a metal pipe provided with a water supply port at one end and a gate at the other end is energized while supplying water from the water supply port,
In the instantaneous water heating device in which water is heated by the heat generated by the metal tube due to the energization to continuously take out hot water or steam from the gate, water is stably injected into the metal tube even if a sudden pressure change occurs. As means for continuing the operation, a throttle for locally narrowing the cross-sectional area of the pipe is provided in the middle of a pipe connecting the pump for supplying water to the water supply port and the water supply port. ).

According to the experiments conducted by the inventors, the above-described restrictor acts as an obstruction valve due to a temporarily large pressure difference with respect to an extremely steep pressure increase in the metal pipe, and the restriction to the pump side. While effectively preventing water backflow, it has been found that steady water flow from the pump, with a slight pressure drop, does not significantly impede it. For this reason, by providing the throttle, a sudden rise in pressure caused by bumping or the like does not reach the pump side, and water can be injected without interruption from the pump toward the metal pipe. As the throttle, a so-called orifice can be used, but a simple structure in which a pipe is partially crushed to form a constriction is also effective (claim 2). On the other hand, as the pump, it is preferable to use a positive displacement pump such as a gear pump, a vane pump, or a tube pump, so that a constant flow rate of water can be more reliably supplied against the pressure fluctuation on the metal tube side. (Claim 3). Further, if a check valve is provided between the pump and the water supply port, the action of preventing the backflow of water is further ensured, and the operation is stopped by utilizing the pressure required in the forward direction of the check valve. The effect of preventing water leakage at the time can be performed (claim 4).

Next, in order to appropriately control the electric power supplied to the metal pipe, the present invention provides an operation for calculating an appropriate supply electric power from a target flow rate of water and temperature of hot water or temperature or wetness of steam. Means, and power command means for commanding a power supply device to supply power to the metal pipe based on a calculation result of the calculation means (claim 5).

In the instant water heating apparatus according to the present invention, since the temperature of hot water or steam changes instantaneously, it is difficult to stably perform power control based on a deviation between a slow response temperature detection result and a target temperature. . Therefore, in the present invention,
By setting the required flow rate of water, the temperature of hot water or steam, and the wetness of steam in advance, the appropriate power required for this target value is calculated, and the supplied power is controlled based on the calculation result. (Claim 6). Since this control is an open-loop control, stable control can be obtained, and high-precision power control can be performed by performing calculations at high speed.

[0009] In the instantaneous heating device for water, abnormal overheating accompanied by danger due to empty heating, clogging of a metal tube or the like is apt to occur. Therefore, a water detector for detecting the presence or absence of water is provided in the pipeline on the upstream side of the water supply port, and when the water detector detects that water supply has been cut off, power is supplied to the metal pipe. Should be stopped immediately (claim 6).
In this case, a large pressure is not generated in the area from the water tank to the pump, so use a transparent or translucent plastic tube, etc. Is detected, the detection can be performed more easily than the determination of the presence or absence of water from the detection of the flow rate.

Further, it is preferable that a temperature detector for detecting the temperature of an energized portion near the water supply port of the metal pipe is provided, and when the temperature detector detects an abnormal temperature, the supply power is reduced. (Claim 7). Since it is difficult to detect the temperature of water in a metal tube, it is easier and more accurate to detect abnormal overheating of water from the temperature of the metal tube. In that case, near the water supply port,
Since the normal temperature is low, a simple temperature sensor can be used.The power density is the highest, so there is a high possibility that the temperature at the time of an abnormality such as when water does not come is the highest, and the temperature difference between the normal time and the abnormal time is large. Abnormality detection is easiest because the detection error of the abnormality detection is small and the detection speed is fast.

On the other hand, a temperature detector is provided for detecting the temperature of a non-energized portion near the gate of the metal tube, and the temperature of hot water or steam in the gate is estimated from the metal tube temperature detected by the temperature detector. (Claim 8). The steam temperature of the gate is a high temperature of, for example, 300 ° C. to 400 ° C., and the temperature sensor becomes expensive. Also, when trying to detect the steam temperature of the gate, installation is also difficult because the temperature sensing part of the temperature sensor protrudes outside the apparatus. On the other hand, the temperature of the non-energized part near the gate of the metal pipe is much lower, and 200 ° C to 300 ° C.
And a stable and inexpensive standard sensor can be used. In addition, even if the temperature of the metal tube becomes the current-carrying part near the gate, 350 ° C to 500 ° C
And higher.

Preferably, the metal tube is bent in a spiral or snake shape or partially deformed flat. In a metal tube, water is scattered due to a sudden rise in pressure due to bumping, but when water droplets reach a tube wall near a sprue having a high steam temperature, the water is cooled, so that stable superheated steam of 100 ° C. or more cannot be obtained. By adopting a shape other than the straight line as described above, the scattered water droplets collide with the nearby tube wall and stick to the tube wall so that they cannot reach far. As a result, continuous steam separation becomes possible, and stable steam generation is obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system configuration diagram showing an embodiment of the present invention as a steam generator used in an experiment.
FIG. 2 is a heating characteristic diagram for explaining a control mode in the apparatus of FIG. First, in FIG.
The vertical axis indicates the power P required to obtain the desired hot water, wet steam and dry steam, using the flow rate Q (g / sec) as a parameter at the gate temperature T ₀ ° C. ing. In FIG. 2, the case where the flow rate Q is 1 g / sec is shown by a thick line as a representative, and therefore, description will be made below as an example. Now, in order to raise the temperature of water at a flow rate of Q = 1 g / sec by 100 ° C., a calorie of 100 cal / sec, that is, 418 W of electric power is required. When this 100 ° C water is heated in the air, wet steam is obtained in which water and steam coexist. To convert all water to steam (wetness = 0),
539cal / sec is added, and 2672W of power is required. When this steam is further heated, high-temperature dry steam is obtained, and the electric power required for increasing the temperature is well known. Figure 2 is a representation of these relationships as a line diagram for a number of the flow rate Q (g / sec), the broken line of FIG. 2, the temperature T ₀ of water to target
^{* 1} , if the wetness H ^* (%) of the wet steam or the temperature T ₀ ^{* 3} of the thirst steam is selected, the electric power to be supplied to the metal tube 3 is P ^{* 1} ,
P ^{* 2} and P ^{* 3} are known for each flow rate Q (g / sec).

On the other hand, in FIG. 1, water in a water tank 1 is sent to a metal pipe 3 by a gear pump 2 as a positive displacement pump,
, And is converted into dry steam and released from the gate 6. The power supply device 4 includes a high-frequency inverter 7 and a transformer 8, and a low-voltage, large-current (for example, 5 V, 500 A) current is supplied from a secondary terminal of the transformer 8. As the metal tube 3, a stainless steel tube having an inner diameter of 5 mm and an outer diameter of 6 mm is used. Here, the metal tube 3 is wound in a spiral shape with several turns, and is divided into four sections whose length gradually increases from the water supply port side to the gate port side.
The current is supplied in parallel from the next side so that the directions of the currents in the adjacent sections are opposite to each other. As a result, electric power whose power density decreases stepwise is supplied from the water supply port side into which the low-temperature water flows to the sluice side where the water temperature gradually rises, and bumping is suppressed and efficient heating is performed. In addition, since the currents in adjacent sections are reversed, the magnetomotive forces in each section cancel each other out, reducing inductance and facilitating energization, reducing magnetic flux leakage and preventing effects on peripheral devices. Is done. The metal tube 3
Is indicated by a single line except for the water supply port 5 and the gate 6.
The output of the power supply device 4 is controlled by the control unit 12.

A transparent plastic pipe (silicon tube) is used for a pipe 9 extending from the water tank 1 to the metal pipe 3, and a throttle 1 is provided in the pipe 9 on the discharge side of the gear pump 2.
0 and a check valve 11 are inserted, and a water detector 13 for detecting the presence or absence of water is provided on the suction side. Water detector 13
Is used for detecting the presence or absence of water from the refraction of the light beam, and the output signal is input to the control unit 12.
A temperature detector 14 for detecting the temperature T ₁ of the metal tube 3 is provided in a current-carrying portion near the water supply port 5 of the metal tube 3,
A temperature detector 1 for detecting a temperature for detecting the temperature T ₂ of the metal tube 3 is provided in a non-energized portion near the gate 6 of the metal tube 3.
5 are provided. Further, on the outside of the sprue 6 of the metal tube 3, the temperature detector 16 for detecting the steam temperature T ₀ which is emitted from the sprue 6 are provided. A thermocouple or a thermistor is used for each of the temperature detectors 14 to 16, and an output signal thereof is input to the control unit 12.

FIG. 3 shows the power calculation and
FIG. 3 is a block diagram illustrating a command unit. The power calculation / command unit 17 includes a main calculation unit 18 and an auxiliary calculation unit 19, and the main calculation unit 18 stores a characteristic diagram formed by a polygonal line shown in FIG. Therefore, when the target steam temperature T ₀ ^* or the wetness H ^* and the flow rate Q ^* are set and input, the main processing unit 18 outputs a power signal P necessary for it. On the other hand, the auxiliary calculation unit 19
Compares the target temperature T ₀ ^* with the actual measured value T ₀ of the steam outlet temperature from the temperature detector 16, and calculates a correction signal ΔP corresponding to the deviation.
Is output. The power calculation / command unit 17 adds this correction signal to the power signal P and outputs an appropriate power signal P *. The control unit 12 controls the output of the power supply device 4 based on the appropriate power signal P ^* . As can be seen from FIG. 2, dP / dT ₀ has an infinite part, and it is difficult to perform feedback control of the steam temperature. However, according to the open-loop control shown in FIG. Stable heating can be realized.

Now, the apparatus shown in FIG.
The metal pipe 3 is energized from the power supply device 4 while the pump 2 is operated to supply water from the water supply port 5, and the water is heated by the heat generated by the metal pipe 3 due to the energization, and in this case, a desired temperature T ₀ ^* the dry steam continuously releases (for example 300 ° C. to 400 ° C.). The rotation speed of the pump 2 is controlled based on the rotation speed / flow rate characteristics of the pump 2 and the target flow rate Q ^* stored in advance, but the flow rate detector 20 is provided as shown by a dashed line, and based on the signal thereof, Feedback control may be performed. When the control unit 12 detects that the supply of water is cut off by the water detector 13, the control unit 12 immediately shuts off the power supply to prevent empty heating. When the temperature of the metal pipe 3 near the water supply port detected by the temperature detector 14 rises abnormally, the supply power is reduced.

The throttle 10 acts to suppress the backflow of water to the pump 2 when the internal pressure of the metal tube 3 rises explosively due to bumping or the like. 4 shows a diaphragm used in the apparatus shown in FIG. 1. FIG. 4 (A) is a longitudinal sectional view, and FIG. 4 (B) is a transverse sectional view along the line BB. The diaphragm 10 in FIG. 4 has the simplest structure, and is formed by crushing the pipe 9 from above and below to form a constriction. The throttle 10 allows water from the pump to pass from left to right as indicated by the arrow, while exhibiting a large resistance action against a sudden rise in pressure in the metal pipe 3 on the right side of the throttle 10, In combination with the flow characteristics, backflow of water to the pump side is prevented. The check valve 11 also has a backflow preventing function, but at the same time, when the pump 2 is at rest, it is necessary for the water to flow forward (to the right in FIG. 1).
Water pressure from the pump 2 to the metal pipe 3 is prevented at a pressure of about 2 atm.

FIGS. 5 and 6 are longitudinal sectional views showing modified examples of the diaphragm. The diaphragm 10 in FIG. 5 is formed of an orifice, and has an edge on the metal tube side (the right side in FIG. 5). The throttle 10 in FIG. 6 is formed of a tapered nozzle, and the pump side (the left side in FIG. 6) is formed in a trumpet shape, and the metal tube side is formed in a cylindrical shape. Although the shape is slightly more complicated than that of FIG. 5, there is an advantage that the contraction is small. Each of them has an action of blocking a sudden rise in pressure on the metal tube side from the pump side.

[0020]

As described above, according to the present invention, it is possible to suppress complicated phenomena of water in a metal pipe by stable water supply and appropriate power supply to the metal pipe, and to promote instantaneous heating of water smoothly. become.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an instantaneous heating device for water showing an embodiment of the present invention.

FIG. 2 is a water heating characteristic diagram for explaining a control mode in the apparatus of FIG. 1;

FIG. 3 is a block diagram of a power calculation / command unit included in a control unit in FIG. 1;

FIG. 4 shows the diaphragm in FIG. 1, (A) is a longitudinal sectional view,
(B) is a cross-sectional view along the line BB.

FIG. 5 is a longitudinal sectional view showing a modification of the stop.

FIG. 6 is a longitudinal sectional view showing a different modification of the stop.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water tank 2 Water supply pump 3 Metal pipe 4 Power supply device 5 Water supply port 6 Sluice 9 Pipe line 10 Throttle 11 Check valve 12 Control part 13 Water detector 14 Temperature detector 15 Temperature detector 16 Temperature detector 17 Power calculation / Command means

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H05B 3/00 H05B 3/00 310D 3/40 3/40 A F term (Reference) 3K058 AA11 AA22 AA41 AA51 AA71 BA11 CA12 CA13 CA46 CE02 3K092 PP11 QA02 QB02 RA06 RA10 RD03 UA05 UA06 UA11 VV11 VV25 3L034 BA14 BA34 EA02

Claims (9)

[Claims] An electric current is supplied to a metal pipe having a water supply port at one end and a sprue at the other end while supplying water from the water supply port, and the water is heated by the heat generated by the metal pipe due to the energization. In an instantaneous heating device for water that continuously takes out hot water or steam from a pump, a cross-sectional area of the pipe is locally determined in a pipe connecting the pump for supplying water to the water supply port and the water supply port. An instantaneous heating device for water, characterized in that an aperture for narrowing is provided. 2. The instantaneous heating device for water according to claim 1, wherein said restrictor is formed by constriction of said conduit. 3. The instantaneous heating device for water according to claim 1, wherein a positive displacement pump is used as said pump. 4. The instant water heating device according to claim 1, wherein a check valve is provided between the pump and the water supply port. 5. A metal pipe provided with a water supply port at one end and a sprue at the other end is supplied with water from said water supply port while supplying electricity thereto, and heat is generated by said metal pipe due to the energization to heat the water so that the sprue is heated. An instantaneous heating device for continuously extracting hot water or steam from the apparatus, comprising: calculating means for calculating an appropriate supply power from a target flow rate of the water and a temperature of the hot water or a temperature or wetness of the steam; An instantaneous heating device for water, comprising: a power commanding means for commanding power supplied to the metal tube to a power supply device based on a calculation result of the calculating means. 6. A water detector for detecting the presence or absence of water is provided in a pipe upstream of the water supply port, and when no water is detected by the water detector, power supply to the metal pipe is immediately stopped. 6. The instantaneous heating device for water according to claim 5, wherein: 7. A temperature detector for detecting a temperature of an energized portion near the water supply port of the metal pipe, and when the temperature detector detects an abnormal temperature, the power supplied to the metal pipe is reduced. 6. The instantaneous heating device for water according to claim 5, wherein: 8. A temperature detector for detecting the temperature of a non-energized portion near the gate of the metal pipe, and the temperature of the hot water or steam of the gate is estimated from the temperature of the metal pipe detected by the temperature detector. 6. The instantaneous heating device for water according to claim 5, wherein: 9. An instantaneous water heating device according to claim 1, wherein said metal tube is bent in a spiral or snake shape or partially flattened.