DE2503411A1 - HOT WATER GENERATORS AND METHOD OF SHOCK TESTING FINISHED PIPE PARTS USING A HOT WATER GENERATOR - Google Patents

Description

of prefabricated pipelines under Use of a hot water generator

The invention relates to hot water generators and relates in particular to a hot water generator for the · = ■ Achieving maximum heat exchanger performance regarding the heat absorption and thereby the temperature rise is operated at high temperatures while avoiding bubble germination, as well as a method for shock testing of prefabricated pipeline parts using a Hot water generator.

So far, hot water boilers have been significantly below the achievable maximum combustion chamber load operated. The reason for this lies in the heat exchangers and in the pressure control devices, which lead to the generation of abruptly occurring vapor pockets or vapor bubbles, which in part can experience overheating. "Strikes" or result from pressure surges generated by these vapor bubbles Load pressure fluctuations in the heat exchanger part of the hot water generator. Such phenomena are undesirable because they lead to damage to the heat exchanger and to audible

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Noises. Hot steam bubbles generate an öriflxc limited overheating of the heat exchange surfaces, which leads to a reduced service life. The evaporation of Water creates film or surface temperatures that are sufficiently high to cause scale formation and / or corrosion. It is therefore important that this is done in the hot water generator. not heated water in the vapor phase passes.

A conventional water heating device is described, for example, in US Pat. No. 3,282,257 in which for Generation of steam of controlled quality in a heat exchanger similar to the heat exchanger according to the invention in Connection with a steam drum is used. This heater works due to load pressure fluctuations about $ 75 of the maximum combustion chamber load.

A boiler for rapidly increasing the water temperature is disclosed in US Pat. No. 3,651,790, which deals with the use of complicated heat transfer devices to increase the heat exchange area. Devices of this type are difficult and expensive to manufacture. In addition, in such devices, the internal pressure distribution is not uniform during thermal and flow surges, so that undesirable vapor bubbles are generated.

Another complicated hot water generator with a heat exchanger is set forth in U.S. Patent 3,773-019. This device is also difficult and expensive in the Manufacturing.

The invention is based on the object of a hot water generator to create, with which, while avoiding the formation of vapor pockets, a high rate of temperature increase up to close to the theoretical maximum

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Achieve water temperature change and a shock test of high-performance Eoiirleitungs -pertigteile by loading a finished part through a rapid rise in water temperature without bubble germination.

The object of the invention is also to provide a hot water generator with control devices with which the hot water generator can be operated in such a way that the maximum rate of temperature change without generation of vapor pockets in the liquid is achieved.

Furthermore, it is the object of the invention to provide a hot water generator, the heat exchanger with simple Medium and economical to produce, has a long service life and with a controlled supply of heat and Heat extraction a maximum heat absorption and thereby Temperature rise rate generated.

This object is achieved by a hot water generator as characterized in the claims is.

The hot water generator according to the invention uses a heat exchanger and a combustion device in a design similar to the devices described in the aforementioned TJS-PS 3 282 in conjunction with an advantageous control system in order to achieve the maximum rate of water temperature increase without generating steam pockets. For example, the hot water generator according to the invention can be operated so that water having a temperature of about 294 ⁰ G at a pressure of about 160 kp / cm s within about 50 to a 'temperature of from about 330 ⁰ C at a pressure of about 159 kp / cm can be brought. This makes it possible for the heat exchanger to absorb the maximum heat flow without entering the area of germ-like boiling or evaporation with bubble formation or even more advanced,

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to pass over the pressure involved in the corresponding boiling or evaporation stages. As a result, the hot water generator is according to the invention is able to perform a shock test of high-performance prefabricated pipeline parts, such as e.g. valves, regulators, heat exchangers and the like, when a finished part is exposed to a rapid increase in water temperature without bubble germination or generation of vapor pockets.

Regarding the control devices with which the hot water generator to achieve the rapid rise in temperature in the heated water, a temperature regulator is required, which monitors the outlet temperature of the water heated in the hot water generator and a signal for actuation a fast-responding air-fuel actuator generated to the maximum allowable combustion rate set that the heat exchanger part of the hot water «produces and tolerates in the heated Water no steam pockets are generated. The power of a combustion air supplying the combustion device The fan can be regulated via a shut-off valve connected to the actuator. The actuator also regulates Fuel metering valve that supplies fuel to the combustion device. A control range of 1:24 for the Hot water generator allows the formation of a "water wall", which increases the water outlet temperature quickly generated within precisely regulated flow and pressure limits.

The invention is described below with reference to schematic drawings an exemplary embodiment explained in detail. In the drawing shows:

Pig. 1 a simplified representation, partly as a block diagram, of the 'hot water generator according to the invention with the control devices and a Water flow loop,

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Pig. 2 shows a simplified representation of a system with a large number of hot water generators connected in parallel in connection with the. Shock test of a pipe component,

Pig. 3 a graphical representation of the maximum allowable Water temperature at the outlet water generator as a puncture of the outlet pressure "with a Hot water generator according to the invention,

Pig. 4 a graphical representation of the maximum values for the outlet pressure and outlet temperature of the Water of a hot water generator according to the invention as a puncture of the water flow rate to prevent boiling in the heat exchanger of the hot water generator,

Pig. 5 is a graphical representation of a common Boiling curve to show the boiling curve in hot water generators,

Pig. 6 a graphical representation of the time-dependent course of the water outlet temperature of the Heater at the transition from low to high burning capacity of the hot water generator after Invention, with a representation of the maximum temperature rise without bubble germination,

Pig. 7 shows a graphic representation with the characteristic curves for maximum permissible combustion outputs between the outlet temperature of the heater at lower Combustion capacity and the maximum permissible outlet temperature without boundary layer boiling,

Pig. 8 is a block diagram of the air-fuel control device the hot water generator - according to the invention,.

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9 »10 and 11 graphical representations of the operating sequences after a change in the setpoint temperature the sailing device in connection with the control signal, the butterfly valve and the Temperature of the hot water at the outlet of the heat exchanger, and

2, 13 and 14 are graphs showing the relationship between the temperature of the hot water entering the heat exchanger of the hot water generator, the hot water exiting the heat exchanger and the flue gases entering the heat exchanger from the combustion device during the load change.

Pig. 1 shows a simplified representation of the hot water generator according to the invention. In the example shown, this has a housing 20 which has a combustion part 21 and enclosing a coil portion 22. In the case 20

a throttle 23 is provided between the combustion part 21 and the coil part 22, which the gas flow from the combustion part 21 is to lead to the coil part 22. One arranged in the interior of the pipe coil part 22 Coiled pipe or heat exchanger in the form of a coiled pipe is designated as a whole by 24 and has a plurality of water pipes. In the annular-helical designed pipe coil 24 are the water pipes in radially arranged layers and in the longitudinal direction with Intermediate spacing arranged one behind the other rows. To the outermost water pipe layer is an inlet 25 to which an outlet 26 connected to the innermost water pipe layer. Combustion or smoke gases generated in the combustion part 21 flow through the throttle 23 into the central region of the pipe coil 24 and from there to the outside and by a flue gas vent 27. The hot water generator is only shown in a simplified manner, but it is on it

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pointed out that this part of the hot water generator essentially corresponds to a form of construction as shown in; U.S. Patent 3,282,257 "mentioned earlier. The helical water pipes form a flow path for the water, which extracts heat from the coil that is absorbed from the flue gases. This makes the Heat transfer to the one flowing through the coils Minimum amount of water required. In order to achieve the desired rapid temperature increase in the water, it is important to that the minimum amount of water is involved in the heat transfer process.

The generation of combustion gases takes place from a corresponding Mixture of fossil fuel and air. The fuel can be natural gas or another suitable one Be fossil fuel, which is obtained from a corresponding supply source via a fuel line 30 to the combustion part 21 or a combustion chamber in the combustion part 21 can be fed. The fuel flow rate in the combustion part 21 can be regulated with a metering valve 31.

Primary or combustion air can be blown with a fan 32 generate and pass through a line 33 to the combustion part. To regulate the air flow rate in the Line 33 is provided with a shut-off valve 34. To maintain combustion stability With a lower combustion output, a small amount of air can be drawn off from the line 33 above the shut-off valve 34 and via a lifting air line 35 into the fuel line Introduce 30 in order to be able to mix some air into the fuel introduced through this into the combustion part 21. This is important for achieving a large controllability between high and low combustion output. In particular it facilitates the creation of a control range of about 1:24 in order to enable the necessary temperature increase and for the shock test of prefabricated components

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to obtain necessary shock test according to the method according to the invention.

To control the operation of the metering valve 31 and the shut-off valve 34 and thus for regulating the fuel-air mixture flowing into the combustion part 21 A fast-responding air-fuel actuator 38 is mechanically connected to the components 3.1 and 34 mentioned. This actuator 38 receives a signal from an appropriately designed [temperature controller 39, the by a setpoint indicator 40 and by the one removed with a corresponding temperature measuring instrument. 41 Temperature of the hot water at the outlet 26 of the heat exchanger 24 is controllable.

The inlet and outlet ends of the coil or heat exchanger 24 are through a pipe or conduit connected with each other. In the pipeline 45, a pump 46 is installed, which always has an appropriate flow rate a constant flow of water through the entire *> Forcing water flow path or water loop. In the Coiled pipe 24 is therefore forced to circulate water. To load the system is in the pipeline 45 also a loading member 47 installed. In the example shown, this is a heat exchanger, but it can be any be designed expediently. However, it should be designed so that there is a continuous path in the Pipeline 45 creates. If the

Shock test provided prefabricated part around a heat exchanger it can be installed at the installation point provided for the load element 47. Is this The component to be tested is a valve, regulator or the like. Its installation in the pipeline 45 at a point 48 is upstream from the loading member 47 or at a point 49 between the loading member 47 and the pump 46 possible. The load link 47 is to the heat exchanger capacity of the To adapt the hot water dispenser.

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If the load member is so large that a single high-speed steam generator would not be sufficient, how the example according to Pig. Figure 2 shows a variety of hot water generators be connected in parallel, as in this example with the hot water generators 2OA, 2OB and 2OC shown. Corresponding distributors and collectors at the inlet and outlet facilitate the parallel arrangement of such Rapid steam generator. Although the one shown in FIG Example has three hot water generators, it is obvious that, depending on the load member, any one. Number of hot water generators can be connected in parallel. Hot water generator connected in parallel at the outlets Corresponding equalization or relief valves can be provided so that the outlet collector of each, Hot water generator is supplied under the same temperature and pressure conditions. -

As already mentioned, the hot water generators can be heated with any fossil fuel. The water used in the system should be degassed, softened and, if necessary, _ύ : treated in some other way.

The air-fuel actuator 38 can be of any type be considered, which has the necessary, sufficiently short response time to deal with the rapid increase in temperature to allow the liquid in the heat exchanger of the hot water generator and also to allow bubble germination impede. For example, if the actuator has a complete cycle in two seconds or less, then it has the for the hot water generator according to the invention ' required short response time. The transition behavior must be faster than the heat absorption capacity of the Heat exchanger of the hot water generator.

Pig. 5 shows a typical boiling curve for the boiling curve for hot water generators. Most hot water systems work in a state of unsteady equilibrium

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the several of the in I ¹ Xg. 5 boiling ranges shown are traversed. An attachment should be in the. with 51 designated area "beginning point-like boiling or evaporation with bubble formation, which is immediately before point A, in which pure boiling occurs, and forms the area in which the most effective heat transfer is available. The plant after the The invention works in point B. Exceeding the maximum heat output can lead to the system working in the areas of unstable boiling, which results in damage or destruction of the heat exchange surfaces.

The speed of the temperature increase depends on the maximum heat flow that the heat exchanger of the hot water generator can absorb without moving into the area of punctiform boiling or even more advanced boiling stages corresponding to the pressures involved. In Pig. 6 shows the temperature-time behavior of a hot water generator according to the invention, the water temperature at the heater outlet being plotted over time in s. As can be seen from this graph, the time to transition from low combustion performance at high combustion output or full firing rate (100? S) is the hot water he zeugers about 40 seconds, the temperature at low focal power about 300.5 ⁰ C and at high combustion output is approximately 330.5 ⁰ C. Similarly, the rate of temperature drop is dependent on the maximum heat flow that can be absorbed by the heat exchanger. The "trigger point ¹¹ A" and the normal operation point B are also shown.

The one in Pig. 3 curve refers to the maximum permissible water temperature at the outlet of the pipe coil as puncture of the outlet pressure at the hot water generator of the invention and shows what relationship between

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Temperature and pressure must be maintained to prevent bubble germination. In the area to the left of the curve, there is in the coil does not boil at the boundary layer, while in the hatched area to the right of the curve in the coil boundary layer boiling takes place. This Area is to be avoided. Accordingly, during the Increase in water temperature to avoid boiling the relationship between temperature and pressure in the area on the left off the curve. The places shown for point A (Pig. 5) apply to water flow rates of 50 .to $ 100 if the in Pig. 7 specified fuel inserts and throughputs are maintained.

The one in the diagram of the pig. 4 drawn curves represent the limit values for the water outlet pressure and the water outlet temperature of the hot water generator as a puncture of the water flow rate, at which boundary layer boiling in the pipe coil of the hot water generator is avoided. The absolute outlet pressure at the heater in kp / cm is plotted against the outlet temperature at the heater in G. *> ■ The curves marked 55, 56 and 57 represent the water flow rates at 50, 90 and 100 $ respectively. In the areas to the left of the curves there is no boiling, the areas to the right of the curves are boiling areas. The maximum allowable for the stationary system temperatures are at an absolute pressure of about 168.7 kg / cm ² to about 332, 336.8 and 339 ⁰ C at a Wasserdur.chflußmenge of 50, 90 and 100 $ achieved. Accordingly, the limit of about 168.7 kgf / cm is referred to as the "trip point", which is a pressure that must be maintained or exceeded in order to enter the in Pig. 3 to prevent hatched boiling range.

The operation of the hot water generator according to the invention makes it in the transition from low to high burning power

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It is necessary to increase a nominal or residual temperature in the case of a low combustion output and to set the water flow rate to a value corresponding to the required amount of heat. This is in Pig. 7, in which above the heat transferred to the water in FIG. kcal / h. the outlet temperature of the heater is plotted ^{in 0 C.} These curves represent the fuel throughputs that are maximum permissible during operation between the heater outlet temperature at low combustion output and the maximum permissible outlet temperature without boundary layer boiling. For the water flow rate, the curves for 50, 60, 70, 80, 85, 90, 95 and $ 100 flow rates are shown. The water flow rate of $ 100 represents the maximum heat output of the system. These curves are based on a high-speed steam generator with a capacity of about 3 »03» 10 kcal / h. The maximum fuel throughput depends on the required water flow rate. Rapid feeding of the correct fuel-air mixture or its rapid setting to about $ 50 of the nominal throughput capacity of the hot water ^generator according to the invention leads to a temperature increase corresponding to curve 60, at which the desired heat flow capacity is reached at about 330.5 C. . The associated control devices for the fuel-air mixture switch off and thereby interrupt the supply of heat. At this water flow rate, a temperature higher than about 336 ^° C. leads to boiling. Furthermore, it is not possible to set the maximum burning power higher. The time required to achieve the temperature point of about 330.5 ⁰ C is about 50 s.

It stands to reason that when heating water at full maximum power ($ 100) without training of steam bags there is a certain relationship between pressure, temperature and flow rate. The following For example, the table contains information about the

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Throughput capacity of a hot water generator with the in Pig. 7 characteristic curves shown:

Water flow rate at maximum fuel throughput in io

Minimum flow throughput capacity speed in the pipe in the pipe in m / s in kg / h

100

95 90

85 80 70 60 50

1.77 1.68 1.58 1.49 1.40 1.37 1.07 0.88

56 623 53 782 50 961 48 130 45 298 39 636 33 974 28 312

The values given are approximate conversion values. . ·

From the one in Pig. 8 shown block diagram of the system it can be seen that the temperature controller 39 the setpoint v Receives temperature and outputs a signal to an adder terminal 65, which a feedback signal accordingly the temperature T, of the hot water flowing out, the one with the temperature measuring instrument 41 in the outlet 26 '. of the heat exchanger 24 is measured. The sum of the feedback signal and that from temperature controller 39 The signal is supplied to the servomotor or actuator 38 which regulates the operating position of the metering valve 31 and the shut-off valve 34. From the operating position of the metering valve 31 and the shut-off valve 34 results in the weight or the mass and the temperature of the flue gases in the combustion part 21 and in the heat exchanger 24. The load member 47, which dissipates heat and thereby the temperature of the flowing into the heat exchanger Determined by hot water, has an impact on the overall operation of the system.

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The answer to the change in setpoint of the temperature controller 39 during a temperature rise is in Pig. 9, 10 and 11 recorded as a function of time. According to Pig. is the change in the control signal of the setpoint temperature T

amplified by the full range of the desired temperature increase of about 300.5 to about 330.5 ⁰ C. Pig. 10

shows the relationship between temperature T- and weight or

ig

Mass W »of the flue gases and the operating position of the shut-off valve 34 and the metering valve 31. The increase in the The temperature T, of the hot water flowing out of the heat exchanger 24 is in Pig. 11 shown. Let it be on one dead zone 68 indicated, which is also referred to by the reference numeral 69 in Pig. 6 is shown.

The change in load of the heat exchanger 24, indicated by a temperature drop, is in Pig. 12, 13 and 14 shown as the effect on the temperature of the hot water flowing into the heat exchanger, on the temperature of the hot water flowing out of the heat exchanger or on the temperature and weight or mass of the flue gases in the combustion part _ύ and heat exchanger part.

From the above it follows that the hot water generator according to the invention for performing the method the shock test of high-performance pipeline components can be used, with the generation of a maximum heat flow without bubble germination is aimed at, so that a long service life of the hot water generator and the Heat exchanger is guaranteed.

/Expectations

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Claims (1)

A. N S. P. R- Ü. C. H E ■ 1 ../ hot water generator with a large control range for quick Raising the temperature of hot water to approximately the point of theoretical maximum heat absorption and temperature increase without germ-like boiling or without bubble germination, with • a housing with interconnected, essentially cylindrical pipe hammering and combustion parts, one Annular-helical tube coil in the tube coil part, which has an open central area for receiving combustion gases has, forms a water flow path and the Absorbs minimum amount of water, -as well as an inlet and an outlet for the pipe coil, marked by - a pipe (45) connected to the inlet (25) and the outlet (26) with a loading member (47) in the form of * a heat exchanger that forms a self-contained water flow path, - A pump (46) in the pipeline (45), which has a constant Forces water to circulate through the closed loop, - A device for supplying fuel and air with Control devices (31, 34) for fuel and air which, in cooperation with one another, the combustion part (21) the supply the correct fuel-air mixture, - a fast-responding actuator (38) for the fuel and air regulating devices (31, 34), - - and by a temperature controller (39), the actuator (38) Actuating signals as a function of a nominal value and of the water temperature at the outlet (26) of the coil (24) to cause a rapid increase in the temperature of the outflowing water without germinal boiling. 509831/0669 2503 A 1 1 2. Hot water generator according to claim 1, characterized in that the device for feeding of fuel and air comprises a fossil fuel burner and a fan (32). 3. hot water generator according to claim 1 or 2, characterized in that that the by the pump (46) in the pipe (45) maintained .Druck the water temperature just below the value of the germ-like boiling. 4. Hot water generator according to one of claims 1 to 3, characterized in that the control devices (31, 34) have a fuel metering valve (31). 5. hot water generator according to claim 4, characterized by - One connecting the fan (32) to the combustion part (21) Line (33) with a shut-off valve (34) for regulating the combustion air, - a line (3 5) branching off above the shut-off valve (34) for secondary combustion air, with which a small amount of air is constantly flowing into the fuel line below the valve (31) (30) can be introduced in order to maintain combustion stability at low combustion output, and a throttle (23) arranged in the housing (20) between the combustion part (21) and the coil part (22), which throttle the Directs combustion gases from the combustion part (21) in the central area of the pipe coil (24). 6. hot water generator according to claim 5, characterized in that the fast-responding fuel-air actuator (38) is connected to the fuel metering valve (31) and to the air shut-off valve (34). 509831/0669 ³ 7. hot water generator according to one of claims 1 to 6, characterized in that the control range is approximately 1:24. 8. Hot water generator according to one of claims 1 to 7, characterized in that it is eichnet with natural gas is heatable ". 9. Hot water generator according to one of claims 1 to 8, characterized in that the burning power is dimensioned such that a peak temperature of the water at the outlet (26) of the coil (24) in less than a minute is attainable. 10. Procedure for shock testing of a prefabricated pipeline part using a hot water generator, g e k e η 'η draws through the following work steps: - Installation of the prefabricated part in a water pipe, - Connecting the water line to a coil on the hot water generator, 'ύ - Circulation of the water through the pipe and through the coil of the hot water generator, - and starting up the hot water generator from lower to high burning power in such a way that the water ' quickly and without germinal boiling to an approximate point of the theoretical maximum heat absorption and temperature increase is heated. 11. The method according to claim 10, characterized in that during operation of the hot water generator, the temperature of the water flowing out of this ^: is monitored in order to regulate the increase in the burning power so that the formation of steam pockets in the water is avoided. - 4 509831/0669 25Ü3411 12. The method according to claim 11, characterized in that g e k e η η ζ calibrates that when the water is circulated, such a flow rate is set that the ratio pressure held at water temperature means the maximum temperature rise to a point just below the point of beginning germ-like boiling limited. 6761. 509831/0669