Patent Grant
10132494
The present invention relates to a heat transfer tube through which a heating medium such as water flows therein, a boiler and a steam turbine device.
Conventionally, as a heat transfer tube through which a heating medium such as water flows, a tube with an inner surface fin equipped with a fin for forming multi-screws on an inner surface has been known (for example, see Japanese Patent Publication No. 5-118507). The interior of the tube with the inner surface fin has a subcritical pressure. In some cases, water flowing through the interior of the tube with the inner surface fin having the subcritical pressure is subjected to film boiling by heating the heat transfer tube. When the film boiling occurs, since the heat transfer decreases by a steam film formed on the inner surface of the tube, the temperature of the tube increases. Therefore, in the tube with the inner surface fin, the fin has a predetermined shape so as to suppress the temperature rise of the tube due to the film boiling. Specifically, the tube with the inner surface fin is configured so that a lead of the fin is 0.9 times a square root of an average tube inner diameter at a maximum level or a radial height of the fin is 0.04 times the average tube inner diameter at a minimum level.
Furthermore, as a heat transfer tube used in a once-through type steam generator of a supercritical pressure variable pressure operation type, a water-wall tube (rifled tube) of a water-cooled tube wall group has been known (for example, see Japanese Patent Publication No. 6-137501). The rifled tube is provided with a spiral projection on its inner surface. The once-through type steam generator performs a subcritical pressure operation in a partial load operation, and by providing the spiral projection on the inner surface of the rifled tube, the tube wall temperature of the rifled tube is kept below an allowable temperature at the time of subcritical pressure operation.
In this way, when the interior of the heat transfer tube such as the tube with the inner surface fin described in Japanese Patent Publication No. 5-118507 is in a state of subcritical pressure, in order to suppress the temperature rise of the tube due to the film boiling, the fin has a predetermined shape. Similarly, in order to keep the tube wall temperature of the rifled tube below an allowable temperature at the time of subcritical pressure operation, the rifled tube described in Japanese Patent Publication No. 6-137501 is provided with a spiral projection on the inner surface.
Meanwhile, in some cases, the heat transfer tube flows water as a heating medium, in a state in which its interior has the supercritical pressure. Water flowing at the supercritical pressure is not boiled even if it is heated (does not enter a gas-liquid two-phase state), and flows through the interior of the heat transfer tube in a single-phase state. Here, when water flowing through the interior of the heat transfer tube having the supercritical pressure has a low mass velocity (a low flow velocity) or a high heat flux is applied to water at the time of heating the heat transfer tube, a heat transfer degradation phenomenon occurs in which a heat transfer coefficient decreases in some cases. When the heat transfer degradation phenomenon occurs, since the heat transfer from the heat transfer tube to water decreases, the temperature of the heat transfer tube is liable to increase.
Moreover, in the heat transfer tube having the supercritical internal pressure, when the heat transfer coefficient is low, since the heat transfer coefficient from the heat transfer tube to water decreases, the temperature of the heat transfer tube is liable to rise. Here, in Japanese Patent Publication No. 5-118507, a fin has a shape based on the premise that the interior of the heat transfer tube is in a state of subcritical pressure, that is, that the interior of the heat transfer tube is in the gas-liquid two-phase state. For this reason, since the shape of the fin is not based on the premise that the interior of the heat transfer tube is in the single-phase state, it is difficult to suppress the temperature rise of the heat transfer tube even by applying the invention of Japanese Patent Publication No. 5-118507.
Thus, an object of the present invention is to provide a heat transfer tube, a boiler and a steam turbine device capable of suppressing an increase in the tube temperature, by suppressing an occurrence of heat transfer degradation phenomenon during supercritical pressure.
Furthermore, another object of the present invention is to provide a heat transfer tube, a boiler and a steam turbine device capable of suppressing an increase in the tube temperature, by improving the heat transfer coefficient, while suppressing an occurrence of heat transfer degradation phenomenon during supercritical pressure.
According to an aspect of the present invention, a heat transfer tube which is provided in a boiler, an interior of the heat transfer tube having a supercritical pressure and a heating medium flowing through the interior includes: a groove portion that is formed on an inner circumferential surface and has a spiral shape toward a tube axis direction; and a rib portion that is formed to protrude inward in a radial direction by the groove portion of the spiral shape. In a cross section taken along the tube axis direction, when a width [mm] of the groove portion in the tube axis direction is defined as Wg, a height [mm] of the rib portion in the radial direction is defined as Hr, and a tube outer diameter [mm] is defined as D, the width Wg [mm] of the groove portion, the height Hr [mm] of the rib portion, and the tube outer diameter D [mm] satisfy “Wg/(Hr·D)>0.40”.
According to this configuration, when the interior becomes a supercritical pressure, by satisfying Wg/(Hr·D)>0.40, it is possible to suppress the occurrence of the heat transfer degradation phenomenon. For this reason, since the occurrence of the heat transfer degradation phenomenon can be suppressed during supercritical pressure, it is possible to suppress an increase in tube temperature.
Advantageously, in the heat transfer tube, when the boiler is operated at a rated output, an average mass velocity of the heating medium flowing through the interior of the heat transfer tube forming the furnace wall becomes 1000 to 2000 kg/m2s.
According to this configuration, even when the heating medium such as water flowing through the interior of the heat transfer tube has a low mass velocity, or high heat flux is applied to the heating medium, it is possible to suppress an occurrence of the heat transfer degradation phenomenon.
Advantageously, in the heat transfer tube, when an interval [mm] of the rib portion in the tube axis direction is defined as Pr, the number of the rib portion in a cross section which is taken perpendicularly to the tube axis direction is defined as Nr, and a wetted perimeter length [mm] of the cross section which is taken perpendicularly to the tube axis direction is defined as L, the height Hr [mm] of the rib portion, the interval Pr [mm] of the rib portion, the number of the rib portion Nr and the wetted perimeter length L [mm] satisfy “(Pr·Nr)/Hr>1.25 L+55”.
According to this configuration, when the interior becomes the supercritical pressure, by satisfying (Pr·Nr)/Hr>1.25 L+55, it is possible to suppress the occurrence of the heat transfer degradation phenomenon. Thus, since the occurrence of the heat transfer degradation phenomenon can be suppressed during supercritical pressure, it is possible to suppress an increase in tube temperature.
Advantageously, in the heat transfer tube, when the boiler is operated at a rated output, the average mass velocity of the heating medium flowing through the interior of the heat transfer tube forming the furnace wall is equal to or less than 1500 kg/m2s.
According to this configuration, even when the mass velocity of the heating medium that flows through the interior of the heat transfer tube is lowered, it is possible to suppress the occurrence of the heat transfer degradation phenomenon.
Advantageously, in the heat transfer tube, the tube outer diameter D [mm] is “25 mm≤D≤40 mm”.
According to this configuration, if the tube outer diameter is 25 mm to 40 mm, the effect is more remarkable.
According to another aspect of the present invention, a heat transfer tube which is provided in a boiler, an interior of the heat transfer tube having a supercritical pressure and a heating medium flowing through the interior includes: a groove portion that is formed on an inner circumferential surface and has a spiral shape toward a tube axis direction; and a rib portion that is formed to protrude inward in a radial direction by the groove portion of the spiral shape. When a height [mm] of the rib portion in the radial direction is defined as Hr, an interval [mm] of the rib portion in the tube axis direction is defined as Pr, the number of the rib portion in the cross section which is taken perpendicularly to the tube axis direction is defined as Nr, and a wetted perimeter length [mm] of the cross section which is taken perpendicularly to the tube axis direction is defined as L, the height Hr [mm] of the rib portion, the interval Pr [mm] of the rib portion, the number Nr of the rib portion and the wetted perimeter length L [mm] satisfy “(Pr·Nr)/Hr>1.25 L+55”.
According to this configuration, when the interior becomes a supercritical pressure, by satisfying (Pr·Nr)/Hr>1.25 L+55, it is possible to suppress the occurrence of the heat transfer degradation phenomenon. For this reason, since the occurrence of the heat transfer degradation phenomenon can be suppressed during supercritical pressure, it is possible to suppress an increase in tube temperature.
Advantageously, in the heat transfer tube, when the boiler is operated at a rated output, an average mass velocity of the heating medium flowing through the interior of the heat transfer tube forming the furnace wall is equal to or less than 1500 kg/m2s.
According to this configuration, even when the mass velocity of the heating medium that flows through the interior of the heat transfer tube is lowered, it is possible to suppress the occurrence of the heat transfer degradation phenomenon.
Advantageously, in the heat transfer tube, in a cross section taken along the tube axis direction, when a width [mm] of the groove portion in the tube axis direction is defined as Wg, and a tube outer diameter [mm] is defined as D, the width Wg [mm] of the groove portion, the height Hr [mm] of the rib portion, and the tube outer diameter D [mm] satisfy “Wg/(Hr·D)>0.40”.
According to this configuration, when the interior becomes a supercritical pressure, by satisfying Wg/(Hr·D)>0.40, it is possible to suppress the occurrence of the heat transfer degradation phenomenon. For this reason, since the occurrence of the heat transfer degradation phenomenon can be suppressed during supercritical pressure, it is possible to suppress an increase in tube temperature.
Advantageously, in the heat transfer tube, when the boiler is operated at a rated output, an average mass velocity of the heating medium flowing through the interior of the heat transfer tube forming the furnace wall becomes 1000 to 2000 kg/m2s.
According to this configuration, even if the heating medium such as water flowing through the interior of the heat transfer tube has a low mass velocity, or a high heat flux is applied to the heating medium, it is possible to suppress the occurrence of the heat transfer degradation phenomenon.
Advantageously, in the heat transfer tube, the tube outer diameter D [mm] is “25 mm≤D≤40 mm”.
According to this configuration, if the tube outer diameter is 25 mm to 40 mm, the effect is more remarkable.
According to still another aspect of the present invention, a heat transfer tube which is provided in a boiler, an interior of the heat transfer tube having a supercritical pressure and a heating medium flowing through the interior includes: a groove portion that is formed on an inner circumferential surface and has a spiral shape toward a tube axis direction; and a rib portion that is formed to protrude inward in a radial direction by the groove portion of the spiral shape. When a height [mm] of the rib portion in the radial direction is defined as Hr, an interval [mm] of the rib portion in the tube axis direction is defined as Pr, a width [mm] of the rib portion in a circumferential direction of the inner circumferential surface is defined as Wr, the number of the rib portion in the cross section which is taken perpendicularly to the tube axis direction is defined as Nr, a wetted perimeter length [mm] of the cross section which is taken perpendicularly to the tube axis direction is defined as L, a width [mm] of the groove portion in the tube axis direction of the cross section which is taken along the tube axis direction is defined as Wg, and a tube outer diameter [mm] is defined as D, the width Wg [mm] of the groove portion, the height Hr [mm] of the rib portion, and the tube outer diameter D [mm] satisfy “Wg/(Hr·D)>0.40”, and the height Hr [mm] of the rib portion, the interval Pr [mm] of the rib portion, the width Wr [mm] of the rib portion, the number Nr of the rib portion and the wetted perimeter length L [mm] satisfy “(Pr·Nr)/(Hr·Wr)>0.40 L+9.0”.
According to this configuration, when the interior becomes a supercritical pressure, it is possible to improve the heat transfer coefficient, while suppressing the occurrence of the heat transfer degradation phenomenon. For this reason, by improving the heat transfer coefficient while suppressing the occurrence of the heat transfer degradation phenomenon during supercritical pressure, it is possible to suppress an increase in tube temperature.
Advantageously, in the heat transfer tube, when the boiler is operated at a rated output, an average mass velocity of the heating medium flowing through the interior of the heat transfer tube forming the furnace wall becomes 1000 to 2000 kg/m2s.
According to this configuration, even when the heating medium such as water flowing through the interior of the heat transfer tube has a low mass velocity, or a high heat flux is applied to the heating medium, it is possible to improve the heat transfer coefficient, while suppressing the occurrence of the heat transfer degradation phenomenon.
Advantageously, in the heat transfer tube, when the boiler is operated at the rated output, the average mass velocity of the heating medium flowing through the interior of the heat transfer tube forming the furnace wall is equal to or less than 1500 kg/m2s.
According to this configuration, even when the mass velocity of the heating medium flowing through the interior of the heat transfer tube is lowered, it is possible to improve the heat transfer coefficient, while suppressing the occurrence of the heat transfer degradation phenomenon.
Advantageously, in the heat transfer tube, the tube outer diameter D [mm] is “25 mm≤D≤35 mm”.
According to this configuration, if the tube outer diameter is 25 mm to 35 mm, the mass flow velocity of the heating medium can be set to at least any one of the above-described range, and the mass flow velocity of the heating medium can be set to the suitable mass flow velocity. Here, in the case of applying the heat transfer tube to a boiler, the mass flow velocity of the heating medium flowing through the interior is set to a predetermined mass flow velocity. In this case, in regard to a defined mass flow velocity, when the tube outer diameter decreases, the mass flow velocity increases, and meanwhile, when the tube outer diameter increases, the mass flow velocity decreases. For this reason, in order to achieve the mass flow velocity suitable for the shape of the heat transfer tube that satisfies the above-described formula, by setting the tube outer diameter in the range of 25 mm to 35 mm, the defined mass flow velocity can be achieved, and it is possible to optimize the performance of the heat transfer coefficient.
Advantageously, in the heat transfer tube, the height Hr [mm] of the rib portion, the interval Pr [mm] of the rib portion, the width Wr [mm] of the rib portion, the number Nr of the rib portion and the wetted perimeter length L [mm] satisfy “(Pr·Nr)/(Hr·Wr)<0.40 L+80”.
According to this configuration, in the formula of “(Pr·Nr)/(Hr·Wr)>0.40 L+9.0”, when the formula of the left side extremely increases, an interval Pr of the rib portion widens, the number Nr of the rib portion increases, a height Hr of the rib portion becomes zero, and a width Wr of the rib portion in a circumferential direction becomes zero. Accordingly, it is not easy to maintain the shape of the heat transfer tube. For this reason, by satisfying the formula “(Pr·Nr)/(Hr·Wr)<0.40 L+80”, it is possible to easily maintain the heat transfer tube in a suitable shape.
According to still another aspect of the present invention, a boiler includes the heat transfer tube according to any one of the above that is used as the furnace wall tube that forms a furnace wall of the boiler operated at a supercritical pressure, when operated at a rated output.
According to this configuration, the heat transfer tube can be applied as a furnace wall tube that forms a furnace wall of the boiler. In addition, such a furnace wall tube may also be referred to as a rifled tube.
According to still another aspect of the present invention, a boiler which heats the heating medium flowing through the interior of the heat transfer tube, by heating the heat transfer tube according to any one of the above by radiation of flame or high-temperature gas.
According to this configuration, it is possible to suppress an occurrence of heat transfer degradation phenomenon of the heat transfer tube during supercritical pressure, or to improve heat transfer coefficient, while suppressing the occurrence of the heat transfer degradation phenomenon of the heat transfer tube. For this reason, it is possible to suitably maintain the heat transfer from the heat transfer tube to the water as a heating medium, and it is possible to stably generate steam from water. In addition, for example, the high-temperature gas may be a combustion gas that is generated by combusting the fuel, and may be a flue gas discharged from a device such as a gas turbine. In other words, as a boiler using a heat transfer tube in which the interior becomes a supercritical pressure, for example, a supercritical pressure variable pressure operation boiler, a supercritical pressure constant pressure operation boiler or the like may be applied which heats the heat transfer tube by radiation of flame or combustion gas. In this case, the heat transfer tube is configured as furnace wall of a furnace provided in the boiler, by arranging a plurality of the heat transfer tubes in the radial direction. Furthermore, as another boiler that uses the heat transfer tube in which the interior becomes a supercritical pressure, for example, an exhausted heat recovery boiler which heats the heat transfer tube by the flue gas may be applied. In this case, the heat transfer tube is configured as the plurality of heat transfer tube groups arranged in the radial direction, and is housed in a container through which the flue gas flows. In this way, the heat transfer tube may be applied to any boiler, as long as the interior of a boiler becomes a supercritical pressure.
According to still another aspect of the present invention, a steam turbine device includes: the boiler according to any one of the above; and a steam turbine that is operated by steam generated by heating of water as the heating medium which flows through the interior of the heat transfer tube provided in the boiler.
According to this configuration, it is possible to suppress the occurrence of the heat transfer degradation phenomenon of the heat transfer tube during supercritical pressure, or to improve the heat transfer coefficient, while suppressing the occurrence of the heat transfer degradation phenomenon of the heat transfer tube. For this reason, it is possible to suitably maintain the heat transfer from the heat transfer tube to the water, and the steam can be stably generated. For this reason, since it is possible to stably supply the steam to the steam turbine, it is also possible to stably operate the steam turbine.
Embodiments according to the present invention will be described below in detail based the drawings. In addition, the present invention is not to be limited by the embodiments. In addition, constituent elements in the embodiments include those capable of being easily replaced by those skilled in the art, or those substantially identical thereto. Furthermore, the constituent elements described below can be appropriately combined with each other, and when there is a plurality of embodiments, it is also possible to combine the embodiments.
The thermal power plant of the first embodiment uses pulverized coal obtained by crushing coal (such as bituminous, and subbituminous coal) as pulverized fuel (solid fuel). The thermal power plant combusts the pulverized coal to generate steam by heat generated by combustion, and drives a generator connected to the steam turbine to generate electric power, by rotating the steam turbine by the generated steam.
As illustrated in
The boiler 10 is used as a conventional boiler, and is a pulverized coal-fired boiler that is capable of combusting the pulverized coal by a combustion burner 41 and recovering the heat generated by the combustion by the use of a furnace wall tube 35 that functions as a heat transfer tube. Furthermore, the boiler 10 is a supercritical pressure variable pressure operation boiler in which the interior of the furnace wall tube 35 is set to a supercritical pressure or a subcritical pressure. The boiler 10 is equipped with a furnace 21, a combustor 22, a steam separator 23, a superheater 24, and a repeater 25.
The furnace 21 has furnace walls 31 that surround the four sides, and is formed in a square tubular shape by the furnace walls 31 of the four sides. Moreover, in the furnace 21 having the square tubular shape, its extending longitudinal direction becomes a vertical direction and becomes perpendicular to an installation surface of the boiler 10. The furnace wall 31 is formed using a plurality of furnace wall tubes 35, and the plurality of furnace wall tubes 35 is disposed side by side in the radial direction so as to form the wall surfaces of the furnace walls 31.
Each furnace wall tube 35 is formed in a cylindrical shape, and its tube axis direction becomes the vertical direction and becomes perpendicular to the installation surface of the boiler 10. Further, the furnace wall tubes 35 are so-called rifled tubes in which spiral grooves are formed therein. Water as a heat transfer medium flows through the interior of the furnace wall tubes 35. The internal pressure of the furnace wall tubes 35 becomes a supercritical pressure or a subcritical pressure, depending on the operation of the boiler 10. The furnace wall tubes 35 are configured so that the lower side in the vertical direction is an inflow side, and the upper side in the vertical direction is an outflow side. In this way, the furnace 21 of the boiler 10 of the present embodiment is in a vertical tubular furnace type in which the furnace wall tubes 35 are perpendicular. The details of the furnace wall tubes 35 will be described below.
The combustor 22 has a plurality of combustion burners 41 mounted on the furnace wall 31. Furthermore, in
The superheater 24 is provided inside the furnace 21 to superheat the steam supplied from the furnace wall tubes 35 of the furnace 21 via the steam separator 23. The steam superheated in the superheater 24 is supplied to the steam turbine 11 via a main steam pipe 46.
The reheater 25 is provided inside the furnace 21 to heat the steam used in (a high-pressure turbine 51 of) the steam turbine 11. The steam flowing into the reheater 25 from (the high-pressure turbine 51 of) the steam turbine 11 via a low-temperature reheat steam pipe 47 is heated by the reheater 25, and the heated steam flows into (an intermediate-pressure turbine 52 of) the steam turbine 11 from the reheater 25 again via a high-temperature reheat steam pipe 48.
The steam turbine 11 has the high-pressure turbine 51, the intermediate-pressure turbine 52, and a low-pressure turbine 53. These turbines 51, 52 and 53 are connected by a rotor 54 as a rotating shaft in an integrally rotatable manner. The main steam pipe 46 is connected to the inflow side of the high-pressure turbine 51, and the low-temperature reheat steam pipe 47 is connected to the outflow side thereof. The high-pressure turbine 51 rotates by the steam supplied from the main steam pipe 46, and discharges the steam after use from the low-temperature reheat steam pipe 47. The high-temperature reheat steam pipe 48 is connected to the inlet side of the intermediate-pressure turbine 52, and the low-pressure turbine 53 is connected to the outflow side thereof. The intermediate-pressure turbine 52 rotates by the steam supplied and reheated from the high-temperature reheat steam pipe 48, and discharges the steam after use toward the low-pressure turbine 53. The intermediate-pressure turbine 52 is connected to the inflow side of the low-pressure turbine 53, and the condenser 12 is connected to the outflow side thereof. The low-pressure turbine 53 rotates by the steam supplied from the intermediate-pressure turbine 52, and discharges the steam after use toward the condenser 12. The rotor 54 is connected to the generator 17, and rotationally drives the generator 17 by rotation of the high-pressure turbine 51, the intermediate-pressure turbine 52 and the low-pressure turbine 53.
The condenser 12 flocculates the steam discharged from the low-pressure turbine 53 by a cooling line 56 provided therein to return (condensate) the steam to water. The flocculated water is supplied toward the low-pressure feed water heater 14 from the condenser 12. The low-pressure feed water heater 14 heats the water flocculated by the condenser 12 in a low-pressure state. The heated water is supplied toward the deaerator 15 from the low-pressure feed water heater 14. The deaerator 15 deaerates water supplied from the low-pressure feed water heater 14. The deaerated water is supplied toward the high-pressure feed water heater 13 from the deaerator 15. The high-pressure feed water heater 13 heats the water deaerated by the deaerator 15 in a high-pressure state. The heated water is supplied toward the furnace wall tubes 35 of the boiler 10 from the high-pressure feed water heater 13. In addition, between the deaerator 15 and the high-pressure feed water heater 13, a feed water pump 16 is provided to supply water toward the high-pressure feed water heater 13 from the deaerator 15.
The generator 17 is connected to the rotor 54 of the steam turbine 11, and generates power by being rotationally driven by the rotor 54.
In addition, although it is not illustrated, the thermal power plant 1 is provided with a denitrification device, an electrostatic precipitator, an induced blower, and a desulfurization device, and a stack is provided at a downstream end portion.
In the thermal power plant 1 configured in this way, the water flowing through the interior of the furnace wall tubes 35 of the boiler 10 is heated by the combustor 22 of the boiler 10. Water heated by the combustor 22 is converted into steam until it flows into the superheater 24 through the steam separator 23, and the steam passes through the superheater 24 and main steam pipe 46 in this order and is supplied to the steam turbine 11. The steam supplied to the steam turbine 11 passes through the high-pressure turbine 51, the low-temperature reheat steam pipe 47, the repeater 25, the high-temperature reheat steam pipe 48, the intermediate-pressure turbine 52, and low-pressure turbine 53 in this order, and flows into the condenser 12. At this time, the steam turbine 11 rotates by the flowed steam, thereby rotationally driving the generator 17 via the rotor 54 to generate power in the generator 17. The steam flowed into the condenser 12 is returned to water by being flocculated by the cooling line 56. Water flocculated in the condenser 12 passes through the low-pressure feed water heater 14, the deaerator 15, the feed water pump 16, and the high-pressure feed water heater 13 in this order, and is supplied into the furnace wall tubes 35 again. In this way, the boiler 10 of this embodiment becomes a once-through boiler.
Next, the furnace wall tube 35 will be described referring to
A plurality of groove portions 36 is formed in the circumferential direction of the inner circumferential surface P1 at a predetermined interval, in a cross section illustrated in
Furthermore, since each groove portion 36 is formed to sink to the outside in the radial direction, the bottom surface (that is, the outside plane in the radial direction of the groove portion 36) of each groove portion 36 is an inner circumferential surface P2 that is located outside in the radial direction from the inner circumferential surface P1. The inner circumferential surface P2 has a circular shape around the center line I in the cross section illustrated in
Also, since each of the groove portions 36 is formed in a spiral shape toward the tube axis direction, a plurality of groove portions 36 is formed in the tube axis direction of the inner circumferential surface P1 at a predetermined interval, in the cross-section illustrated in
The plurality of rib portions 37 is formed in the circumferential direction of the inner circumferential surface P1 at a predetermined interval, in the cross section illustrated in
Furthermore, each of the rib portions 37 is formed to protrude inward in the radial direction from the bottom surface (that is, the inner circumferential surface P2) of the respective groove portions 36. Also, since the rib portions 37 are formed in a spiral shape toward the tube axis direction, the plurality of rib portions 37 is formed on the inner circumferential surface P2 in the tube axis direction at a predetermined interval, in the cross-section illustrated in
Here, as illustrated in
Also, in the cross section illustrated in
Furthermore, in the cross-section illustrated in
Next, the shape of the furnace wall tube 35 will be described. As described above, water flows through the furnace wall tube 35 in a state in which its interior has a supercritical pressure. In this case, in the furnace wall tube 35 heated by the combustor 22, in some cases, the heat transfer degradation phenomenon in which the heat transfer coefficient is lowered occurs. Therefore, the furnace wall tube 35 is formed in a shape in which the small inner diameter d1, the large inner diameter d2, the tube outer diameter D, the groove width Wg, the rib width Wr, the interval Pr, the rib number Nr, the rib height Hr, and the wetted perimeter length L satisfy the relational formula described below.
In the furnace wall tube 35, the groove width Wg, the rib height Hr and the tube outer diameter D satisfy the relational formula “Wg/(Hr·D)>0.40”. Here, in the case of “Wg/(Hr·D)=F”, the relation “F>0.40” is obtained. At this time, the rib height Hr is “Hr>0”, the rib portion 37 is configured to protrude radially inward. Moreover, the rib height Hr, the rib interval Pr, the rib number Nr and the wetted perimeter length L satisfy the relational formula of “(Pr·Nr)/Hr>1.25 L+55”. Although the details will be described later, by setting the shape of the furnace wall tube 35 to satisfy the above-described relational formula, it is possible to suppress the occurrence of the heat transfer degradation phenomenon. At this time, if the tube outer diameter D is “25 mm≤D≤40 mm”, more remarkable effect is achieved.
A lead angle of the rib portion 37 having the spiral shape becomes an angle that satisfies the above-mentioned relational formula. In addition, the lead angle is an angle with respect to the tube axis direction. If the lead angle of the rib portion 37 is 0°, it becomes a direction along the tube axis direction, and if the lead angle of the rib portion 37 is 90°, it becomes a direction along the circumferential direction. Here, the lead angle of the rib portion 37 is also appropriately changed depending on the number of rib portions 37. In other words, if there are a large number of rib portions 37, the lead angle of the rib portion 37 becomes a gentle angle (approaches 0°), and on the other hand, if there are a small number of rib portions 37, the lead angle of the rib portion 37 becomes a steep angle (approaches 90°).
Next, changes in tube wall surface temperature of the furnace wall which vary depending on the enthalpy will be described referring to
As illustrated in
Here, in
As illustrated in
Meanwhile, as illustrated in
Next, in
As illustrated in
Meanwhile, as illustrated in
As described above, according to the configuration of first embodiment, in the furnace wall tubes 35 in which the interior becomes a supercritical pressure, even if water flowing through the interior of the furnace wall tubes 35 has a low mass velocity or the high heat flux is applied thereto, by satisfying the relation of Wg/(Hr·D)>0.40, as illustrated in
Also, according to the configuration of the first embodiment, even if the water flowing through the interior of the furnace wall tube 35 has the lower limit velocity, by satisfying the relational formula (Pr·Nr)/Hr>1.25 L+55, as illustrated in
Also, according to the configuration of the first embodiment, the furnace wall tube 35 satisfying the above-mentioned relational formula can be applied to a supercritical pressure variable pressure operation boiler of a vertical tubular furnace type. Thus, since it is possible to suppress the occurrence of the heat transfer degradation of the furnace wall tube 35 during supercritical pressure, it is possible to suitably maintain the heat transfer from the furnace wall tube 35 to water and to stably generate the steam.
Also, according to the configuration of the first embodiment, the boiler 10 having the furnace wall tube 35 can be applied to the thermal power plant 1 that uses the steam turbine 11. For this reason, since the steam can be stably generated in the boiler 10, it is possible to stably supply the steam toward the steam turbine 11, and thus, it is possible to stably operate the steam turbine 11.
In the first embodiment, the furnace wall tube 35 which functions as the heat transfer tube is applied to the conventional boiler, and the conventional boiler is applied to the thermal power plant 1, but the present invention is not limited to this configuration. For example, the heat transfer tube which satisfies the above-mentioned relational formula may be applied to an exhausted heat recovery boiler, and the exhausted heat recovery boiler may be applied to an integrated coal gasification combined cycle (IGCC) plant. That is, as long as a once-through boiler is adopted in which the interior of the heat transfer tube has a supercritical pressure, it may be applied to any boiler.
Furthermore, in the first embodiment, although F2 has the shape of the furnace wall tube 35 that satisfies the relational formula of “F>0.40”, and F3 has the shape of the furnace wall tube 35 that satisfies the relational formula of “(Pr·Nr)/Hr>1.25 L+55”, the shape of the furnace wall tube 35 is not limited to the shape of F2 or F3. That is, the shape of the furnace wall tube 35 may be a shape obtained by combining the shape of F2 and the shape of F3.
In the first embodiment, although the shape of the rib portion 37 of the furnace wall tube 35 is not particularly limited, for example, it may be a shape illustrated in
As illustrated in
As illustrated in
Furthermore, the shape of the rib portion 37 of the furnace wall tube 35 may be a shape illustrated in
As illustrated in
As illustrated in
Furthermore, the shape of the rib portion 37 of the furnace wall tube 35 may be a shape illustrated in
As illustrated in
In addition, as illustrated in
Next, a furnace wall tube 35 according to a second embodiment will be described referring to
The interior of the furnace wall tube 35 enters a state of supercritical pressure, and water flows in this state. At this time, the furnace wall tube 35 of the second embodiment heated by the combustor 22 has a shape with high heat transfer coefficient, while suppressing the heat transfer degradation phenomenon.
Incidentally, since the interior of the furnace wall tube 35 has a supercritical pressure, water flows in a single-phase state. Also, since water flows in the tube axis direction, the water becomes the flow that gets over the rib portion 37, while being given a turning force by the rib portion 37. At this time, the flow getting over the rib portion 37 is a so-called back-step flow. The relation between the back-step flow and the heat transfer coefficient will be described referring to
Here, when the fluid flows in a predetermined flow direction in the flow passage 100, the fluid flows on the stepped portion 101 and then separates at the corner portion of the stepped portion 101. The separated fluid reattaches to the bottom surface P4 of the groove portion 102 at the reattachment point O. Thereafter, the water reattaching to the bottom surface P4 of the groove portion 102 flows to the downstream side along the bottom surface P4.
At this time, the heat transfer coefficient of the bottom surface P4 in the predetermined flow direction is as illustrated in
Here, the position of the reattachment point O can be adjusted by varying the rib height Hr and the rib width Wr. That is, it is possible to set the position of the reattachment point O to a position at which the heat transfer coefficient of the furnace wall tube 35 is high, by setting the rib height Hr and the rib width Wr to an optimum shape.
For this reason, the furnace wall tube 35 is formed in a shape in which the small inner diameter d1, the large inner diameter d2, the tube outer diameter D, the groove width Wg, the rib width Wr, the interval Pr, the rib number Nr, the rib height Hr and the wetted perimeter length L satisfy the relational formula described below.
In the furnace wall tube 35, the groove width Wg, the rib height Hr and the tube outer diameter D satisfy the relational formula “Wg/(Hr·D)>0.40” (hereinafter, referred to as Formula (1)). Here, when “Wg/(Hr·D)=F”, the relation is “F>0.40”. At this time, the rib height Hr is “Hr>0”, and the rib portion 37 is configured to protrude radially inward. In addition, the rib height Hr, the rib interval Pr, the rib width Wr, the rib number Nr, and the wetted perimeter length L satisfy the relational formula “(Pr·Nr)/(Hr·Wr)>0.40 L+9.0” (hereinafter, referred to as Formula (2)). Although the details will be described below, by setting the shape of the furnace wall tube 35 to a shape that satisfies the above-described two relational formulas, it is possible to improve the heat transfer coefficient, while suppressing the occurrence of the heat transfer degradation phenomenon.
The lead angle of the rib portion 37 having a spiral shape becomes an angle that satisfies the above-mentioned relational formula. In addition, the lead angle is an angle with respect to the tube axis direction, if the lead angle of the rib portion 37 is 0°, it becomes a direction along the tube axis direction, and if the lead angle of the rib portion 37 is 90°, it becomes a direction along the circumferential direction. Here, the lead angle of the rib portion 37 is also appropriately changed depending on the number of the rib portions 37. That is, if the number of the rib portions 37 is large, the lead angle of the rib portion 37 becomes a gentle angle (approaching 0°), and meanwhile, if the number of the rib portions 37 is small, the lead angle of the rib portion 37 becomes a steep angle (approaching 90°).
Next, the changes in tube wall surface temperature of the furnace wall that varies depending on the enthalpy will be described referring to
As illustrated in
Here, in
As illustrated in
Meanwhile, as illustrated in
Furthermore, as illustrated in
Next, in
As illustrated in
Meanwhile, as illustrated in
In contrast, as illustrated in
Next, a relation between a graph illustrating the relation among the rib height Hr, the rib interval Pr, the rib width Wr and the rib number Nr, and the location according to F4, which varies depending on the wetted perimeter length L, will be described referring to
S1 illustrated in
As described above, according to the configuration of the second embodiment, in the furnace wall tube 35 in which the interior has a supercritical pressure, by satisfying “Wg/(Hr·D)>0.40” and “(Pr·Nr)/(Hr·Wr)>0.40 L+9.0”, it is possible to improve the heat transfer coefficient, while suppressing the occurrence of the heat transfer degradation phenomenon. For this reason, by improving the heat transfer coefficient during supercritical pressure, while suppressing the occurrence of the heat transfer degradation phenomenon, it is possible to suppress the increase in the tube temperature (tube wall surface temperature of the furnace wall 31), over the magnitude of entropy.
Furthermore, according to the configuration of the second embodiment, even when water flowing through the interior of the furnace wall tube 35 is low mass velocity (average mass velocity is 1000 to 2000 kg/m2s), high heat flux is applied thereto, or the mass velocity of water flowing through the interior of the furnace wall tube 35 is lowered (average mass velocity is equal to or less than 1500 kg/m2s), it is possible to improve the heat transfer coefficient during supercritical pressure, while suppressing the occurrence of the heat transfer degradation phenomenon.
Furthermore, according to the configuration of the second embodiment, the furnace wall tube 35 satisfying the above-mentioned relational formula can be applied to a supercritical pressure variable pressure operation boiler of a vertical tubular furnace type. For this reason, since it is possible to suppress the occurrence of the heat transfer degradation phenomenon of the furnace wall tube 35 during supercritical pressure, it is possible to suitably maintain the heat transfer from the furnace wall tube 35 to water, and the steam can be stably generated.
Furthermore, according to the configuration of the second embodiment, the boiler 10 having the furnace wall tube 35 can be applied to the thermal power plant 1 that uses the steam turbine 11. Therefore, since the steam can be stably generated in the boiler 10, it is possible to stably supply the seam toward the steam turbine 11, and thus, the steam turbine 11 can also be stably operated.
In the second embodiment, although the furnace wall tube 35 serving as a heat transfer tube is applied to a conventional boiler and the conventional boiler is applied to the thermal power plant 1, the present invention is not limited to this configuration. For example, the heat transfer tube which satisfies the above-mentioned relational formula may be applied to an exhausted heat recovery boiler, and the exhausted heat recovery boiler may be applied to an integrated coal gasification combined cycle (IGCC) device. That is, as long as a once-through boiler is adopted in which the interior of the heat transfer tube has a supercritical pressure, the heat transfer tube can be applied to any boiler.
Furthermore, although the shape of the rib portion 37 of the furnace wall tube 35 is not particularly limited in the second embodiment, for example, as in the first embodiment, it may have the shape as illustrated in
Next, the furnace wall tube 35 according to a third embodiment will be described referring to
As described in the second embodiment, the average mass velocity of water flowing through the interior of the furnace wall tube 35 is in the range of 1000 (kg/m2s) or more and 2000 (kg/m2s) or less, or is 1500 (kg/m2s) or less and equal to or greater than the minimum mass velocity at which the boiler 10 can be operated. In this way, the mass velocity of the water flowing through the interior of the furnace wall tube 35 becomes a preset mass velocity. The reason is that, in order to achieve an optimum heat transfer coefficient of the furnace wall tube 35 that satisfies Formula (1) and Formula (2), by setting the mass velocity within the above-described range, the position of the reattachment point O illustrated in
In the third embodiment, the tube outer diameter D of the furnace wall tube 35 is formed to be “25 mm≤D≤35 mm”. Here, as illustrated in
As described above, according to the configuration of the third embodiment, by setting the tube outer diameter D to “25 mm≤D≤35 mm”, the mass flow velocity of water can be set to the above-described range, and the mass flow velocity of water can be set to a suitable mass flow velocity. Therefore, since it is possible to achieve the mass flow velocity that is suitable for the shape of the furnace wall tube 35 which satisfies Formula (1) and Formula (2), the position of the reattachment point O can be set to an optimum position, and the optimum performance of the heat transfer coefficient can be achieved.
Next, a furnace wall tube 35 according to a fourth embodiment will be described referring to
In the furnace wall tube 35 of the fourth embodiment, the rib height Hr, the rib interval Pr, the rib width Wr, the rib number Nr and the wetted perimeter length L satisfy the relational formula of “(Pr·Nr)/(Hr·Wr)<0.40 L+80” (hereinafter, referred to as Formula (3)), in addition to Formula (1) and Formula (2). That is, the furnace wall tube 35 of the third embodiment becomes in the range of “0.40 L+9.0<(Pr·Nr)/(Hr·Wr)<0.40 L+80” when Formula (2) and Formula (3) are combined with each other.
Here, in Formula (2), that is, in the formula of “(Pr·Nr)/(Hr·Wr)>0.40 L+9.0”, since the upper limit of “(Pr·Nr)/(Hr·Wr)” is not set, when the formula of the left side extremely increases, a direction is obtained in which the rib interval Pr is widened, the rib number Nr increases, the rib height Hr becomes zero, and the rib width Wr becomes zero. In this case, it is not easy to maintain the shape of the furnace wall tube 35.
Therefore, in the fourth embodiment 4, an upper limit value is set in Formula (3). Here, as illustrated in
As described above, according to the configuration of the fourth embodiment, by defining the upper limit value by Formula (3), it is possible to easily maintain the furnace wall tube 35 to a suitable shape without diverging the rib height Hr, the rib interval Pr, the rib width Wr, the rib number Nr, and the wetted perimeter length L.
In the first to fourth embodiments, although the turning direction of the groove portion 36 and the rib portion 37 having the spiral shape is not particularly limited, the turning direction may be a clockwise direction, may be a counterclockwise direction, and is not particularly limited.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-272804 | Dec 2013 | JP | national |
| 2014-082139 | Apr 2014 | JP | national |
| 2014-227415 | Nov 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/084238 | 12/25/2014 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/099009 | 7/2/2015 | WO | A |
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| Number | Date | Country | |
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| 20160320052 A1 | Nov 2016 | US |
