JP6201640B2 - Steam pipe loss measurement system and measurement method - Google Patents

Description

  The present invention relates to a steam pipe loss measuring system and measuring method.

  In factories in the industrial field, steam is used for a wide range of applications from heating in production processes to heating and humidification of air conditioning. Steam can cover a wide temperature range from a low temperature range of about 45 ° C. to a high temperature range of about 170 ° C., so to speak, it is an easy-to-use heat medium. For this reason, steam pipes are generally laid in many places in the factory, and steam is generally sent to each production process from a centrally installed boiler.

  FIG. 9 shows a general conceptual diagram of a steam system laid in a factory. Steam produced by a steam production device such as a boiler is sent to a steam header and used for heating in a production process or heating / humidification of an air conditioner. Steam used for various purposes is collected as drain, collected in a return water tank, etc., and then supplied again to the boiler. Further, a plurality of steam traps for discharging drains generated by condensation of steam accompanying heat radiation from the piping are arranged in the middle of the piping.

  In the steam system shown in FIG. 9, the following four losses can be considered with respect to the input fuel energy. (1) Loss of boiler: Loss that becomes apparent by calculating the amount of heat produced by the boiler with respect to the boiler fuel flow (so-called loss associated with boiler efficiency), (2) Loss during air supply (piping): Loss discharged from the steam trap on the pipe due to heat radiation from the pipe, or loss due to leaked steam from the damaged part of the valve or pipe, (3) Trap loss after the load equipment: From the steam trap to collect the drain (4) Loss of recovery: loss from piping to return drain. Temperature drops due to water replenished to prevent pump cavitation when the return water tank is open to the atmosphere, for example. Loss by doing. The energy obtained by subtracting these losses (1) to (4) from the fuel supplied to the boiler is the energy that is effectively utilized in the production process and air conditioning equipment.

  Loss at the time of air supply (piping) (hereinafter referred to as “piping loss”) includes the following three types of loss. (1) The drain loss is a loss in which the steam in the pipe is condensed and drained along with heat radiation from the pipe and is discharged from the steam trap. (2) The trap leak is a loss in which steam in the pipe leaks simultaneously when the drain trapped by the steam trap is discharged. (3) Leakage such as piping is a loss in which steam leaks due to physical damage or the like in a piping system including steam piping, valves, flanges, and the like.

  The pipe loss measurement method is as follows. That is, a steam flow meter is installed on each of the pipe inlet side (immediately after the boiler outlet) and the pipe outlet side (immediately before various load facilities), and the loss is calculated based on the comparison of the measurement results. However, in this method, since it becomes possible to measure by directly installing the steam flow meter on the pipe, if the pipe outlet side has a complicated configuration, it is necessary to install a plurality of flow meters. Moreover, it is necessary to cut the existing steam pipes for new installation. In addition, the wetness may not be fully evaluated because not all the moisture (drain) is removed from the steam trap.

As another method for measuring the pipe loss, there is a method using a special device such as a thermography. However, this method is expensive, requires specialized technology for analysis and evaluation of measurement results, and tends to be insufficient in pipe surface temperature measurement accuracy. Evaluation of thermal conductivity of steam pipes or insulation materials. Has problems such as being relatively difficult.
On the other hand, there is provided a method of measuring a steam pipe loss by measuring the amount of evaporation in the steam pipe in this state in an unloaded state in which the internal space of the steam pipe is substantially closed space (for example, Patent Document 1).

Japanese Patent No. 04924762

  In the conventional measuring method, it is necessary to supply steam in order to keep the pressure in the steam pipe constant. When steam is supplied, there is a problem that it is necessary to adjust the flow rate of steam and to adjust the pressure and flow velocity.

  An object of the present invention is to provide a measurement system and a measurement method capable of measuring a loss of a steam pipe, particularly a pipe loss, without performing steam supply while performing no-load measurement.

  According to an aspect of the present invention, a system for measuring a loss of a steam pipe connected to a steam production apparatus and a load facility is provided. The system includes a first device that creates a substantially closed space including at least a portion of the steam pipe, a second device that measures pressure in the substantially closed space, and a measurement result of the second device. And a third device for measuring the loss of the steam pipe.

  According to another aspect of the present invention, there is provided a method for measuring a loss of a steam pipe connected to a steam production apparatus and a load facility. The loss measuring method includes a first step of creating a substantially closed space including at least a part of the steam pipe, a second step of measuring a pressure in the substantially closed space, and a measurement result of the pressure. And a third step of measuring a loss of the steam pipe.

  According to this measurement system and measurement method, pipe loss can be accurately measured using the measurement of a value related to the amount of steam supplied to a substantially closed space, that is, the result of no-load measurement, without supplying steam. Can do.

It is the schematic which shows a loss measurement system. It is a schematic diagram which shows a control unit. It is the table | surface which showed the physical quantity in a steam pipe. It is a graph which shows the relationship between a pressure and enthalpy. It is a graph regarding the average liquid film thickness of a downward annular flow. It is a graph regarding the dimensionless heat transfer coefficient by general velocity distribution. It is a graph which shows the relationship between temperature and enthalpy. It is the schematic which shows the modification of a loss measurement system. It is a conceptual diagram which shows a general steam system.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing a loss measurement system 1.
As shown in FIG. 1, the steam pipe 10 is disposed between a steam production apparatus 20 (such as a boiler) and a load facility 30. Steam from the steam production apparatus 20 flows through the steam pipe 10 and is sent to the load facility 30. In the load facility 30, steam or steam heat is used. The steam discharged from the load facility 30 is collected as a drain, collected in the return water tank 25, and then supplied again to the steam production apparatus 20. The steam pipe 10 is heat-retained by heat retention means (not shown). Various known heat retaining means can be applied. The heat retaining means includes, for example, a heat retaining material that covers the outer surface of the steam pipe 10.

  The steam pipe 10 is provided with a plurality of steam traps (drain traps) ST1, ST2, and ST3 that discharge drains generated by condensation of steam accompanying heat radiation in the piping or the like. In FIG. 1, the number of steam traps STn is three. The number of steam traps STn varies depending on equipment specifications. At least a part of the drain generated by condensation in the steam pipe 10 is captured by the steam traps ST1, ST2, and ST3. Various known steam traps are applicable. Normally, the steam traps ST1, ST2 and ST3 have a structure capable of appropriately discharging the captured drain.

  Between the steam production device 20 and the steam trap ST1 in the steam pipe 10, a temperature sensor 42 and a pressure sensor (second device) 44 are disposed. At least the measurement result of the pressure sensor 44 is sent to the control unit 40. In the steam supply system including the steam production apparatus 20, the supply of steam can be controlled based on the measurement result of the pressure sensor 44 so that the internal pressure of the steam pipe 10 is constant.

  A valve (first device) 27 is disposed near the inlet of the load facility 30 in the steam pipe 10 (between the final steam trap ST3 and the load facility 30). By opening the valve 27, steam from the steam production apparatus 20 can be input to the load facility 30. By closing the valve 27, the steam input from the steam production apparatus 20 to the load facility 30 is shut off.

The control unit (third device) 40 can measure the piping loss in the steam pipe 10 using the measurement result of the pressure sensor 44 as described later.
As described above, the loss measurement system 1 according to the present embodiment includes the valve 27, the temperature sensor 42, the pressure sensor 44, and the control unit 40.

  FIG. 2 is a schematic diagram showing the control unit 40. In FIG. 2, the computing device 50 is, for example, a computer system. The control unit 40 includes an input device 127 and a display device (output device) 128 in addition to the calculation device 50. The computing device 50 includes a converter 123 such as an A / D converter, a CPU (arithmetic processing means) 124, a memory 125, and the like. Measurement data sent from a sensor (such as the pressure sensor 44) of the loss measurement system 1 is converted by the converter 123 or the like as necessary, and is taken into the CPU 124. In addition, initial setting values, temporary data, and the like are taken into the computing device 50 via the input device 127 and the like. The display device 128 can display information regarding input data, information regarding calculation, and the like.

  The CPU 124 can execute a calculation related to the loss of the steam pipe 10 based on the measurement data and information stored in the memory 125. For example, the heat loss (pipe loss) of the steam pipe 10 can be calculated using the measurement result of the pressure sensor 44. Hereinafter, an example of a calculation method related to the loss of the steam pipe 10 will be described.

  This measurement method focuses on the pressure in the steam pipe. In this measurement method, steam is prevented from flowing into the load facility 30 such as (1) stopping the load facility 30 or (2) closing the valve 27 immediately before the load facility 30. That is, a substantially closed space mainly including the internal space of the steam pipe 10 is created. Hereinafter, this state is appropriately referred to as “no load”.

  In a no-load state, the pressure sensor 44 measures the pressure in the substantially closed space formed in the internal space of the steam pipe 10. The pressure in the closed space decreases (changes) with time. This is because the enthalpy has been changed (decreased) due to the occurrence of drainage due to the condensation of steam accompanying the heat radiation in the steam pipe 10 or leakage from the piping / valve. That is, it is considered that the amount of heat loss (enthalpy change amount) in the steam pipe 10 can be grasped by measuring the pressure change in a substantially closed space when there is no load.

  Hereinafter, a method for obtaining the amount of heat loss in the steam pipe 10, that is, the pipe loss, in the no-load measurement by using the pressure measurement value will be described.

  In the evaluation method of the present embodiment, first, the pressure in the substantially closed space formed in the steam pipe 10 is measured by the pressure sensor 44. The measurement data of the pressure sensor 44 is sent to the control unit 40. The control unit 40 obtains heat radiation of the steam pipe 10 from the information related to the pressure and enthalpy change and the pressure change amount per unit time (measurement result of the pressure sensor 44). Information on pressure and enthalpy change is stored in the memory 125.

FIG. 3 is a table showing physical quantities such as dryness, pressure (KPa), enthalpy (KJ / Kg), enthalpy difference, temperature (° C.), density (Kg / m ³ ), density difference, etc. in the steam pipe 10. It is. Pressure and enthalpy are based on the average value of steam and drain. Each physical quantity in FIG. 3 is calculated from a design value of the steam pipe 10 and a steam table. Further, the density shown in FIG. 3 is a combination of drain and steam. In FIG. 3, the case where the dryness is 1 means that the drain ratio with respect to the vapor in the substantially closed space to be pressure-measured is zero, and the drain ratio becomes 10 in the order of decreasing dryness. %, 20%, 30% and 40%. Moreover, in FIG. 3, an enthalpy difference is each enthalpy difference in each pressure 600KPa-900Kpa and pressure 1000KPa. Moreover, in FIG. 3, a density difference is each density difference in each pressure 600KPa-900Kpa and pressure 1000KPa.

FIG. 4 is a graph showing the relationship between the pressure and enthalpy shown in FIG. As shown in FIG. 4, the enthalpy decreases as the pressure decreases.
The relationship between pressure and enthalpy shown in FIGS. 3 and 4 is based on theoretical values created in advance by calculation. For this reason, a deviation occurs between the graph shown in FIG. 4 and the actual measurement result of the pressure sensor 44.

First, the density in the steam pipe is obtained from the measured value of the pressure sensor 44. In the present embodiment, pressure measurement is performed by the pressure sensor 44 before drainage starts from the steam traps ST1, ST2, ST3 provided in the steam pipe 10. Alternatively, the control unit 40 may perform pressure measurement by the pressure sensor 44 by intentionally closing the steam traps ST1, ST2, ST3.
According to this, it is possible to eliminate an error due to a pressure change due to steam being discharged from the steam traps ST1, ST2 and ST3 simultaneously with drain discharge, and a more accurate measurement result can be obtained. .

  Here, the density in the steam pipe is defined as a function of pressure and dryness. Usually, even when a pressure change occurs in the steam pipe 10, the density does not change. Therefore, the correct dryness can be obtained by back-calculating (goal seek) the numerical values in the table of FIG. 3 so that the density becomes the same value as in the case of 1000 KPa shown in FIG.

  The enthalpy in the steam pipe is defined as a function of density and dryness. Therefore, the enthalpy can be obtained by using the density and the back-calculated dryness value. Then, the enthalpy difference between the initial pressure value and the pressure value after the lapse of a predetermined time, that is, the heat radiation (KW / Kg) accompanying the pressure drop is obtained.

  Subsequently, the pipe loss (heat radiation amount (KW)) Q associated with the pressure drop generated in the steam pipe 10 from the volume and density in the substantially closed space where the pressure measurement was performed and the heat radiation (KW / Kg) is obtained. Can be sought.

  By the way, when there is no load (the state where there is no flow), the steam flow rate is low and can be regarded as almost zero. On the other hand, during normal operation, the steam flow rate is high and a flow rate is generated in the pipe. Moreover, in the steam pipe 10 at the time of normal operation, it becomes an annular flow in which drain condensed by heat radiation adheres to the pipe wall as a liquid film. The thickness of the liquid film adhering to the tube wall varies depending on the flow velocity in the steam tube 10.

Here, the flow state (annular flow) of the steam in the steam pipe 10 during normal operation will be described.
FIG. 5 is a graph relating to the average liquid film thickness of the downward annular flow. FIG. 6 is a graph relating to a dimensionless heat transfer coefficient based on a general velocity distribution. In FIG. 5, the horizontal axis indicates the Reynolds number, and the vertical axis indicates the thickness of the liquid film. In FIG. 6, the horizontal axis indicates the Reynolds number, the vertical axis indicates the heat transfer coefficient (W / m ² / ° C.) in the tube, the solid line indicates the tendency of the turbulent liquid film, and the dotted line indicates the laminar liquid film. It shows a trend. In the case of normal operation in the present embodiment, the case of the laminar liquid film in FIG. 6 is applied. 5 and 6, τ is a shearing force exerted on the surface of the liquid film attached to the tube wall by the vapor flow flowing through the vapor tube 10. The shear force τ is expressed by the following formula (1).

here,
c _f : coefficient of friction at the gas-liquid boundary,
γ _v : specific weight of steam,
g: acceleration of gravity,
u _v : steam flow rate,
u _l : liquid film flow rate.

  As shown in FIG. 5, it can be seen that the thickness of the liquid film increases in proportion to the Reynolds number (that is, the flow velocity of the vapor). This is a common tendency regardless of the magnitude of the shearing force τ. Moreover, as shown in FIG. 6, in the case of a laminar liquid film, it can be seen that the heat transfer coefficient in the tube decreases as the Reynolds number increases.

  That is, during normal operation (in a state where there is a flow), the thickness of the liquid film increases as the Reynolds number increases (the increase in the flow rate of steam). Since the liquid film adhering to the tube wall becomes a thermal resistance, the thermal resistance increases as the thickness of the liquid film increases. As a result, the heat transfer coefficient in the tube is affected. That is, during normal operation (in a state where there is a flow), it is necessary to use the heat transfer coefficient in the tube in consideration of the heat dissipation characteristics that vary depending on the flow velocity.

  On the other hand, in this embodiment, the pipe loss Q is obtained by no-load measurement. Therefore, when applying to the piping loss when supplying steam into the load facility 30 (hereinafter referred to as normal operation), it is necessary to correct in accordance with the steam flow rate during normal operation.

For correction, for example, the following correction coefficients can be used.
The correction coefficient is defined based on information on heat dissipation corresponding to the flow state of steam in the steam pipe 10. Specifically, as described later, it is defined by the ratio (qr / qm) of the theoretical heat dissipation amount qr during normal operation and the theoretical heat dissipation amount qm in the no-load state.

  The following formula (2) shows the basic formula for heat dissipation.

here,
q: Amount of heat dissipated per unit pipe length (W / m),
T ₀ : Pipe internal temperature (pipe steam temperature) (° C),
T ₁ : outside air temperature (atmospheric temperature) (° C.)
α ₁ : In-pipe heat transfer coefficient (W / m ² / ° C.),
α ₂ : heat transfer coefficient from the heat insulating material surface to the atmosphere (W / m ² / ° C.),
λ ₁ : thermal conductivity of heat insulation (W / m / ° C.)
r ₀ : Pipe inner diameter (m),
r ₁ : Piping outer diameter (m),
r ₂ : heat insulation outer diameter (outer diameter of heat insulating material) (m).

Hereinafter, a method for calculating the correction coefficient will be described.
First, the theoretical amount of heat release qr of the steam pipe 10 during normal operation (flowing state) is defined. In this case, the Reynolds number (steam flow velocity) is obtained by calculation as information relating to the flow state of the steam. The Reynolds number is obtained from, for example, the pipe diameter, the steam flow rate, the density, the viscosity, and the like.

Subsequently, the in-tube heat transfer coefficient is obtained using the Reynolds number obtained by calculation as described above and the graph shown in FIG. Here, in the graph shown in FIG. 5, the heat transfer coefficient in the tube varies depending on the shearing force. Therefore, the vapor flow rate and the liquid film flow rate are measured, and the shearing force τ is calculated based on the above equation (1). Then, the in-tube heat transfer coefficient corresponding to the calculated shearing force τ is obtained from the graph shown in FIG. 5, and the obtained in-tube heat transfer coefficient is replaced with α _{1 in the} above equation (2).

  Thereby, the theoretical heat radiation amount qr in the normal operation can be derived from the above equation (2).

  Next, the theoretical amount of heat release qm of the steam pipe 10 in a no-load state (state without flow) is defined. In this case, first, the Reynolds number (steam flow velocity) is obtained as information regarding the flow state of the steam in the steam pipe 10. In the no-load state, the liquid film thickness can be regarded as almost zero. From the graph shown in FIG. 5, the Reynolds number at which the liquid film becomes almost zero can be extrapolated.

Subsequently, the in-tube heat transfer coefficient is obtained using the Reynolds number extrapolated as described above and the graph shown in FIG. Here, in the graph shown in FIG. 6, the heat transfer coefficient in the tube varies depending on the shearing force. Since there is no flow in the pipe in the no-load state, the shearing force τ calculated from the difference between the vapor flow rate and the liquid film flow rate can be regarded as almost zero. Therefore, the heat transfer coefficient in the tube corresponding to the shearing force τ = 0 is obtained from the graph shown in FIG. 6, and the obtained heat transfer coefficient in the tube is replaced with α _{1 in the} above equation (2).

  Thereby, the theoretical heat radiation amount qm in the no-load state is derived from the above formula (2).

  In the present embodiment, the ratio (qr / qm) of the theoretical heat dissipation amount qr during normal operation and the theoretical heat dissipation amount qm in the no-load state, calculated as described above, is used as the correction coefficient.

  Subsequently, the piping loss Q obtained by no-load measurement is corrected by multiplying the correction coefficient (qr / qm).

  As described above, according to the present embodiment, it is possible to measure the steam pipe loss by pressure measurement at no load without supplying steam. Therefore, there is no need to adjust the flow rate of steam generated along with the supply of steam, or adjustment due to pressure / velocity fluctuations, and the processing is simple, so there is an advantage that no modification of equipment is required. Moreover, in this embodiment, the piping loss calculated | required by no-load measurement is correct | amended to the value at the time of normal operation. Therefore, highly practical measurement values can be obtained with high accuracy.

  Note that when the enthalpy changes in the steam pipe 10, the temperature also changes with the pressure. FIG. 7 is a graph showing the relationship between the temperature and the enthalpy shown in FIG. As shown in FIG. 7, it can be seen that the temperature decreases as the enthalpy decreases.

Enthalpy changes as shown in the above formula (2), i.e., the heat dissipation of the steam pipe 10, the pipe internal temperature T ₀ is concerned. Therefore, when the enthalpy is obtained in consideration of only the pressure change in the steam pipe 10, an error corresponding to the temperature change is included. Therefore, the correction may be made in consideration of the temperature change in the steam pipe 10. A temperature sensor 42 is used for measuring the temperature in the steam pipe 10.

For example, the case where the temperature in the steam pipe 10 decreases from 180 ° C. to 150 ° C. during pressure measurement will be described as an example. That is, the pipe internal temperature T ₀ is changed from 180 ° C. to 150 ° C. Incidentally, the outside air temperatures _{T 1} shall be 20 ° C..

The correction coefficient for correcting the pipe loss Q is the amount of heat radiation defined by the difference (T ₀ −T ₁ = 160) between the pipe internal temperature T ₀ (180 ° C.) and the outside air temperature T ₁ (20 ° C.), and the pipe internal It is defined by the ratio of the amount of heat radiation defined by the difference (T ₀ -T ₁ = 145) between the temperature T ₀ (165 ° C.) and the outside air temperature T ₁ (20 ° C.). Here, 165 ° C. is an average temperature in the steam pipe 10 before and after pressure fluctuation (that is, an average value of 180 ° C. and 150 ° C.).

In the above formula (2) indicating the amount of heat release, terms other than the temperature change (T ₀ -T ₁ ) can be regarded as constants. Therefore, the pipe loss Q corrected for the temperature change satisfies the relationship of the following expression (3) with the pipe loss Q ′ before correction.

  Q = Q ′ × (145/160) (3)

  In this way, the piping loss Q can be obtained more accurately by correcting the temperature change.

  Further, in the above description, a case has been described as an example in which correction in consideration of temperature fluctuations is collectively performed on the entire calculated pipe loss, but is not limited thereto. That is, heat dissipation (piping loss) may be corrected based on temperature fluctuations per unit time (for example, every second). The temperature per unit time may be measured by a temperature sensor or may be calculated from the pressure measured by the pressure sensor 44.

For example, the initial temperature of the pipe internal temperature T ₀ is 180 ° C., and the outside air temperature T ₁ is 20 ° C.
The temperature T ₀ ′ and the enthalpy change (heat radiation amount) per unit time are calculated. Here, since the heat radiation amount obtained by calculation is a heat radiation amount corresponding to each temperature T ₀ ′, it is converted into a heat radiation amount at the initial temperature (T ₀ = 180 ° C.).

  The expression for converting to the heat radiation amount at the initial temperature is expressed by the following expression (4).

q _{180 ° C.} = W _T0 ′ × (T ₀ ′ / (180 ° C.−20 ° C.)) (4)

here,
q _{180 ° C .} : heat radiation amount at an initial temperature of 180 ° C. W _T0 ′: heat radiation amount at each temperature T ₀ ′.

For example, when the pressure measurement takes 100 seconds, the integrated heat radiation amount can be obtained by adding q _{180 ° C.} of each temperature T ₀ ′ for 1 to 100 seconds. Since the integrated heat radiation amount obtained in this way is composed of the total heat radiation amount considering the temperature per second, an error component due to temperature fluctuation during pressure measurement is eliminated. Therefore, piping loss is required with higher accuracy.

  Further, in the above description, when calculating the correction coefficient, in the case of obtaining the theoretical heat dissipation amount qr during normal operation, the case where the Reynolds number obtained by calculation is used as an initial value is taken as an example. It is not limited to this. For example, a value obtained by measuring the film thickness of the liquid film attached to the pipe wall of the steam pipe 10 with an ultrasonic sensor or the like may be used as the initial value.

  In this case, the Reynolds number is obtained from the measured thickness of the liquid film and the graph shown in FIG. Here, the graph shown in FIG. 5 has different Reynolds numbers depending on the shearing force. Therefore, the Reynolds number is obtained by setting the initial value of the shearing force τ to zero.

  Subsequently, the in-tube heat transfer coefficient is obtained from the Reynolds number obtained from the thickness of the liquid film, using the graph shown in FIG. Here, in the graph shown in FIG. 6 as well, although the heat transfer coefficient in the pipe varies depending on the shearing force, the temporary heat transfer coefficient in the pipe is obtained by setting the initial value of the shearing force τ to zero, similarly to the Reynolds number.

  By replacing the temporary heat transfer coefficient obtained in this way with α1 in the above equation (2), a temporary heat release amount is obtained from the above equation (1) (step S1). Subsequently, the drain flow rate in the steam pipe is calculated from the provisional heat radiation amount. The following formula (5) is used to calculate the drain flow rate.

  q ′ × l = Δh × G (5)

here,
q ′: Temporary heat dissipation (W / m),
l: length of steam pipe (m),
Δh: heat of condensation at pipe pressure (evaporation heat; J / Kg)
G: Drain flow rate (Kg / s)

  That is, if the provisional heat radiation amount q ′ is obtained, the drain flow rate G is obtained from the known l and Δh.

  Subsequently, the shear force τ in the steam pipe in the no-load state is obtained again using the drain flow rate G obtained from the provisional heat radiation amount q ′. As shown in the above equation (1), the shearing force τ is calculated from the difference between the vapor flow rate and the liquid film flow rate. Here, the steam flow velocity is obtained by proportionally distributing the flow rate of the entire pipe calculated based on a flow rate sensor (not shown) by the distance to the steam traps ST1, ST2, ST3, for example. Further, the liquid film flow rate can be calculated from the drain flow rate G. That is, the shearing force τ can be obtained again by using the above formula (1) (step S2).

  Subsequently, the Reynolds number, the in-tube heat transfer coefficient, and the shear force τ are obtained again using the shear force τ and the thickness of the liquid film obtained as described above (step S3). That is, step S1 to step S3 are sequentially repeated until the shearing force τ converges to a constant value.

In this way, the shear force τ in the steam pipe 10 during normal operation can be calculated with high accuracy. Therefore, heat dissipation characteristics (increase in thermal resistance due to the presence of a liquid film) in the flow state of steam during normal operation are taken into account by using the accurately calculated shear force τ and the measured value of the liquid film thickness. Obtain the heat transfer coefficient in the pipe. The theoretical heat release qr during normal operation may be calculated from the above equation (2) by replacing the in-tube heat transfer coefficient thus obtained with α ₁ in the above equation (2).

  In the above embodiment, the valve opening / closing control may be automatic or manual. Periodic loss measurement can be performed to verify damage to piping systems and deterioration of heat insulation performance.

  FIG. 8 shows a modification of the loss measurement system. In FIG. 8, a plurality of steam lines 10A, 10B, and 10C corresponding to the plurality of load facilities 30A, 30B, and 30C are provided. The steam line 10A corresponding to the load facility 30A includes a plurality of steam traps STA1, STA2, and STA3, a pressure sensor 44A, and a valve 27A. Similarly, the steam line 10B corresponding to the load facility 30B includes a plurality of steam traps STB1, STB2, STB3, a pressure sensor 44B, and a valve 27B, and the steam line 10C corresponding to the load facility 30C includes a plurality of steams. Traps STC1, STC2, STC3, a pressure sensor 44C, and a valve 27C are included. The valves 27A, 27B, and 27C are respectively near the entrance of the load facility 30A (30B and 30B) in the steam line 10A (10B and 10C) (the final steam trap STA3 (STB3 and STC3) and the load facility 30A (30B and 30B). Between).

  In FIG. 8, the loss of the entire steam system can be calculated by closing all the valves 27A, 27B, and 27C. In this case, the pressure in the substantially closed space can be measured by the pressure sensors 44A, 44B, and 44C, and the pipe loss in each of the steam lines 10A, 10B, and 10C can be calculated.

  Further, by closing the valve 27A and opening the valves 27B and 27C, the loss of the steam line 10A corresponding to the load facility 30A can be calculated during the operation of the load facilities 30B and 30C. In this case, the loss in the steam line 10A can be calculated by directly measuring the pressure change in the substantially closed space by the pressure sensor 44A.

  Note that the heat dissipation amount q (W / m) per unit pipe length obtained from the measurement results is a value under the pipe diameter and the heat insulation diameter at the measurement point. You may spend it.

The size and heat insulation thickness of the steam pipe in the steam system may vary depending on the steam conditions (amount of steam used, pressure, temperature) of the load equipment. Even in such a case, if the heat radiation amount of a certain steam pipe is known, it is possible to obtain the heat radiation amount by performing correction based on differences in the pipe size, the insulation thickness, the pipe internal temperature, and the outside air temperature. is there. A correction calculation formula (6) for calculating a heat radiation amount corresponding to another pipe size and a heat insulation thickness from a known heat radiation amount is shown below. This equation (6) can be derived from the above theoretical equation (2).
In the correction calculation formula (6), q ″: heat radiation amount per unit length (W / m) in another pipe, r1 ′: pipe outer diameter (m) of another pipe, r2 ′: another pipe Thermal insulation outer diameter (outer diameter of heat insulating material) (m), T0 ′: Internal temperature of another pipe (supply steam temperature) (° C.), T1 ′: Outside air temperature (air temperature) of another pipe (° C.) is there.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment. The numerical value used in the above description is an example, and the present invention is not limited to this. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Loss measuring system, 10 ... Steam pipe, 20 ... Steam production apparatus, 27 ... Valve, 30 ... Load equipment, 40 ... Control unit, 42 ... Temperature sensor, 44 ... Pressure sensor, 50 ... Calculation apparatus, 123 ... Converter , 124, CPU, 125, memory, 127, input device, 128, display device, ST1, ST2, ST3, steam trap.

Claims (6)

A system for measuring the loss of steam pipes connected to steam production equipment and load equipment,
A first device for creating a substantially closed space including at least a portion of the steam pipe;
A second device for measuring the pressure in the substantially closed space;
A third device for measuring a loss of the steam pipe using a measurement result of the second device;
A loss measurement system for a steam pipe, comprising:   The second device measures the pressure in the substantially closed space before draining is started from a drain trap provided in the steam pipe or in a state where the drain trap is closed. The loss measurement system for a steam pipe according to claim 1.   2. The apparatus according to claim 1, wherein the first device includes at least one of a means for stopping the load equipment and a means for closing a valve disposed in the steam pipe in the vicinity of an inlet of the load equipment. The steam pipe loss measurement system according to 2. A method for measuring a loss of a steam pipe connected to a steam production apparatus and a load facility,
A first step of creating a substantially closed space including at least a portion of the steam pipe;
A second step of measuring the pressure in the substantially closed space;
A third step of measuring the loss of the steam pipe using the measurement result of the pressure;
A loss measurement method for a steam pipe, comprising:   The second step is to measure the pressure in the substantially closed space before draining is started from the drain trap provided in the steam pipe or in a state where the drain trap is closed. The steam pipe loss measuring method according to claim 4, wherein:   5. The method according to claim 4, wherein the first step includes at least one of a step of stopping the load facility and a step of closing a valve disposed in the steam pipe in the vicinity of an inlet of the load facility. 5. The steam pipe loss measurement method according to 5.

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