Calculation method for integral regulation and control opening degree of blind window of indirect air cooling tower

Abstract

The invention provides a method for calculating the integral regulation and control opening degree of a shutter of an indirect air cooling tower, and the method comprises the steps: obtaining a target tower outlet water temperature theoretical value under different working conditions through a three-dimensional numerical simulation method based on parameters such as environmental meteorological parameters, a load ratio, a cooling margin and the like; and calculating according to the heat balance and the draft resistance balance of the cooling tower, and coupling to obtain a suggested value of the opening degree of the shutter. By adjusting the opening degree of the blind window and the air inlet amount, pipe bundle frost crack caused by too low temperature of the cooling triangle is avoided, winter freezing prevention of the indirect cooling tower is achieved, and a theoretical basis is provided for practical engineering implementation.

Description

Technical Field

[0001] The present invention is a calculation method for overall regulating the opening degree of the louvers of an indirect air cooling tower, belonging to the technical field of cooling towers. Background Art

[0002] Indirect air cooling is one of the circulating water cooling methods. In order to cool the exhaust steam of the condenser, the indirect cooling unit uses circulating water as an intermediate medium. The circulating water cools the exhaust steam of the steam turbine at the condenser, and the heated circulating water is carried by the circulating water pump to the cooling triangle in the sector of the indirect cooling tower, and exchanges heat with the cold air flowing from the bottom of the tower through the cooling triangle to cool the circulating water in the pipeline. The cooled circulating water then returns to the condenser to enter the next heat exchange cycle.

[0003] The air cooling tube bundle (also known as the "cooling triangle") of the indirect air cooling system is vertically placed at the bottom of the cooling tower, and the air flows outside the tube bundle, and the cooling water cools down inside the tube bundle. Louvers are provided at the bottom of the cooling tower to adjust the air volume. When the ambient temperature is relatively low, especially when the lowest temperature is below 0°C, the louvers can be used to adjust the cooling performance to avoid freezing the radiator due to too low cooling water temperature. By adjusting the opening degree of the louvers, the temperature of the circulating water can be controlled, thereby protecting the radiator and maintaining the normal power generation operation of the unit.

[0004] During the operation in severely cold regions in winter, different opening degrees of the louvers will cause differences in the air intake volume, resulting in local low temperatures in the cooling triangle and cracking of the tube bundle, which will affect the safety of the indirect cooling tower and the generator set. Currently, most of the regulation of the opening degree of the louvers of the indirect cooling tower is based on empirical values or fixed switch angles, and there is a lack of a calculation method for determining the opening degree of the louvers according to different working conditions. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a calculation method for overall regulating the opening degree of the louvers of an indirect air cooling tower, so as to solve the problems in the above-mentioned background art, realize winter anti-freezing of the indirect cooling tower, and improve the energy efficiency and safety of the indirect cooling tower.

[0006] In order to achieve the above purpose, the present invention is realized through the following technical solutions: A calculation method for overall regulating the opening degree of the louvers of an indirect air cooling tower, characterized by including the following steps: S1: Obtain the parameters of the information collection module: ambient meteorological parameters, structural parameters such as louvers and cooling columns, water temperature parameters, and unit load parameters; S2: According to the environmental parameters and load ratio, obtain the theoretical outlet water temperature twbi under different working conditions through three-dimensional data simulation calculation and store it, and set the cooling margin Ty; S3: Calculate the target outlet water temperature twba according to the theoretical outlet water temperature twbi and the cooling margin Ty; S4: Calculate meteorological data such as wet-bulb temperature and moisture content according to the above parameters, and calculate operation data such as the windward area of the cooling tower, fin area, water temperature difference at the inlet and outlet of the tower Δtw, and target inlet water temperature twaa; S5: Assume an initial value for the face velocity vf and an initial value for the heat transfer coefficient K; S6: Conduct a thermodynamic calculation for the indirect cooling tower to calculate the total heat transfer area Az, heat transfer coefficient K, effectiveness E, and air temperature rise Δta, and obtain the heat release on the water side Qwc and the heat absorption on the air side Qai; S7: Determine whether the heat release on the water side Qwc is equal to the heat absorption on the air side Qai or the absolute value of the difference is less than the allowable heat error Ea; if not, continue to determine the magnitude of Qai and Qwc: if Qai is greater, return to S4 after reducing the step size stepa of vf; if Qwc is greater, return to S4 after increasing the step size stepa of vf; otherwise, determine the face velocity vf and the inlet air volume Ga and proceed to the next step; S8: Calculate the overall draft of the entire tower and the resistance of each part of the indirect cooling tower except the louvers based on the inlet air volume Ga and the structural parameters of the indirect cooling tower; S9: Obtain the louver resistance ΔPb based on the balance of draft and resistance during the operation of the indirect cooling tower; S10: Assume an initial value for the louver opening Kd; S11: Obtain the calculated value of the louver resistance ΔPbj according to the louver resistance calculation formula; S12: Determine whether the louver resistance ΔPb is equal to ΔPbj or the absolute value of the difference is less than the allowable resistance error Eb; if not, continue to determine the magnitude of ΔPb and ΔPbj: if ΔPb is greater, return to S8 after reducing the step size stepb of Kd, if ΔPbj is greater, return to S8 after increasing the step size stepb of Kd; otherwise, determine the louver opening Kd and proceed to the next step; S13: Output the louver opening Kd;

[0007] The louver opening is obtained by coupling the thermal balance of the indirect cooling tower and the balance of draft and resistance during operation; according to the thermal balance calculation of the indirect cooling tower, the face velocity vf and the inlet air volume Ga are obtained; finally, according to the louver resistance ΔPbj and the louver opening calculation formula, the louver opening is obtained.

[0008] The face velocity vf and the louver opening Kd are determined by the trial method or the bisection method.

[0009] Advantages of the present invention: A calculation method for overall regulation of the opening degree of the louver of an indirect air cooling tower according to the present invention. This calculation method is based on the theoretical value of the target outlet water temperature under different working conditions, and through the coupling of heat balance and the balance of suction and resistance during operation, the recommended value of the louver opening degree is obtained, the air intake is adjusted, winter anti-freezing is achieved, the energy efficiency and safety of the indirect cooling tower are improved, the tube bundle rupture caused by too low temperature of the cooling triangle is avoided, and the loss of human and material resources is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a flowchart of a calculation method for overall regulation of the opening degree of the louver of an indirect air cooling tower. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] To make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0012] Please refer to Figure 1 , the present invention provides a technical solution: A calculation method for overall regulation of the opening degree of the louver of an indirect air cooling tower, which is characterized by including the following steps: S1: Obtain the parameters of the information collection module: environmental meteorological parameters, structural parameters such as louvers and cooling columns, water temperature parameters, and unit load parameters, etc.; S2: According to the environmental parameters and load ratio, obtain the theoretical value of the outlet water temperature twbi under different working conditions through three-dimensional data simulation calculation and store it, and set the cooling margin Ty; S3: Calculate the target outlet water temperature twba according to the theoretical value of the outlet water temperature twbi and the cooling margin Ty; S4: According to the above parameters, calculate meteorological data such as wet bulb temperature and moisture content, and calculate operating data such as the windward area of the cooling tower, fin area, water temperature difference between inlet and outlet atw, and target inlet water temperature twaa; S5: Assume the initial value of the oncoming wind speed vf and the initial value of the heat transfer coefficient K; S6: Conduct a thermal calculation of the indirect cooling tower, calculate the total heat dissipation area Az, heat transfer coefficient K, effectiveness E, air temperature rise ∆ta, and obtain the heat release Qwc on the water side and the heat absorption Qa on the air side; S7: Judge whether the heat release Qwc on the water side is equal to the heat absorption Qai on the air side or the absolute value of the difference is less than the allowable heat error Ea; if not, continue to judge the magnitude of Qai and Qwc: if Qai is large, then vf is reduced by the step size stepa and return to S4; if Qwc is large, then vf is increased by the step size stepa and return to S4; otherwise, determine the oncoming wind speed vf and the air intake Ga, and enter the next step; S8: According to the air intake Ga and the structural parameters of each part of the indirect cooling tower, calculate the overall tower draft and the resistance of each part of the indirect cooling tower except the louver; S9: Based on the balance between the suction force and the resistance during the operation of the indirect cooling tower, the resistance of the louver ∆Pb is obtained; S10: Assume the initial value of the louver opening Kd; S11: Obtain the calculated value of the louver resistance ∆Pbj according to the louver resistance calculation formula; S12: Determine whether the louver resistance ∆Pb is equal to ∆Pbj or the absolute value of the difference is less than the allowable resistance error Eb; if not, continue to judge the magnitudes of ∆Pb and ∆Pbj: if ∆Pb is larger, then after reducing the step size stepb of Kd, return to S8; if ∆Pbj is larger, then after increasing the step size stepb of Kd, return to S8; otherwise, determine the louver opening Kd and proceed to the next step; S13: Output the louver opening Kd;

[0013] Example 1: Obtain the parameters of the information acquisition module: environmental meteorological parameters, structural parameters such as louvers and cooling columns, water temperature parameters, and unit load parameters, etc.

[0014] According to the environmental parameters and load ratio, through three-dimensional data simulation calculation, obtain the theoretical value of the water temperature leaving the tower under the current working condition twbi = 27.7 °C and store it. Set the cooling margin Ty = 5 °C, and calculate the target water temperature leaving the tower twba = 32.7 °C.

[0015] According to the above parameters, calculate the wet bulb temperature of the meteorological data tau = 9.68 °C, moisture content x = 0.0062, etc., and calculate the operating data: the windward area of the cooling tower A = 35175.84 m 2 、the fin area of a single cooling column Af = 1514.82 m 2 、the temperature difference between the water entering and leaving the tower atw = 10.18 °C, the target water temperature entering the tower twaa = 42.88 °C, etc.

[0016] Assume the face velocity vf = 2 m / s, assume the heat transfer coefficient K = 45 W / (m 2 *°C); According to the law of conservation of energy, set the step size stepa = 0.001, and adjust the face velocity vf until the absolute value of the difference between the heat release amount Qwc on the water side and the heat absorption amount Qai on the air side is less than the allowable heat error Ea = 1 kW, so as to determine the face velocity vf = 1.57 m / s, the air inflow rate Ga = 213577.19 t / h, the total heat dissipation area of the cooling tower Az = 1690135.69 m 2 、the heat transfer coefficient K = 42.86 W / (m 2 *°C), the effectiveness E = 0.61, the air temperature rise ∆ta = 30.18 °C, and obtain the heat release amount Qwc on the water side = 1105382.46 kW and the heat absorption amount Qai on the air side = 1105383.35 kW.

[0017] According to the inlet air volume Ga = 213577.19 t / h and the structural parameters of each part of the indirect cooling tower, the draft of the whole tower and the resistance of each part of the indirect cooling tower except the louver are calculated; according to the balance between the draft and the resistance during the operation of the indirect cooling tower, the louver resistance ∆Pb = 25.97 N is obtained.

[0018] Assume that the louver opening degree is Kd = 1%; according to the louver resistance calculation formula, the calculated value of the louver resistance ∆Pbj is obtained; set the step size stepb = 0.01; adjust the louver opening degree Kd until the absolute value of the difference between ∆Pb and ∆Pbj is less than the allowable resistance error Eb = 1 N; output the louver opening degree Kd = 52%.

[0019] The foregoing has shown and described the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms; therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0020] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A calculation method for overall regulating the opening degree of the louvers of an indirect air cooling tower, characterized in that It includes the following steps: S1: Obtain the parameters of the information acquisition module: environmental meteorological parameters, structural parameters such as louvers and cooling columns, water temperature parameters, and unit load parameters, etc.; S2: According to the environmental parameters and load ratio, obtain the theoretical value of the water temperature out of the tower twbi under different working conditions through three-dimensional data simulation calculation and store it, and set the cooling margin Ty; S3: Calculate the target water temperature out of the tower twba according to the theoretical value of the water temperature out of the tower twbi and the cooling margin Ty; S4: According to the above parameters, calculate meteorological data such as wet bulb temperature and moisture content, and calculate operation data such as the windward area of the cooling tower, fin area, water temperature difference in and out of the tower atw, and target water temperature into the tower twaa; S5: Assume the initial value of the face velocity vf and the initial value of the heat transfer coefficient K; S6: Conduct a thermodynamic calculation of the indirect cooling tower to calculate the total heat dissipation area Az, heat transfer coefficient K, effectiveness E, air temperature rise ∆ta, and obtain the heat release on the water side Qwc and the heat absorption on the air side Qai; S7: Judge whether the heat release on the water side Qwc is equal to the heat absorption on the air side Qai or the absolute value of the difference is less than the allowable heat error Ea; if not, continue to judge the magnitude of Qai and Qwc: if Qai is large, return to S4 after reducing the step size stepa of vf; if Qwc is large, return to S4 after increasing the step size stepa of vf; otherwise, determine the face velocity vf and the air inflow rate Ga and proceed to the next step; S8: According to the air inflow rate Ga and the structural parameters of each part of the indirect cooling tower, calculate the overall tower draft and the resistance of each part of the indirect cooling tower except the louvers; S9: According to the balance of draft and resistance during the operation of the indirect cooling tower, obtain the louver resistance ∆Pb; S10: Assume the initial value of the louver opening Kd; S11: Obtain the calculated value of the louver resistance ∆Pbj according to the louver resistance calculation formula; S12: Judge whether the louver resistance ∆Pb is equal to ∆Pbj or the absolute value of the difference is less than the allowable resistance error Eb; if not, continue to judge the magnitude of ∆Pb and ∆Pbj: if ∆Pb is large, return to S8 after reducing the step size stepb of Kd, if ∆Pbj is large, return to S8 after increasing the step size stepb of Kd; otherwise, determine the louver opening Kd and proceed to the next step; S13: Output the louver opening Kd.

2. The calculation method for overall regulating the opening degree of the louver of an indirect air cooling tower according to claim 1, characterized in that: The louver opening is obtained by coupling the thermal balance of the indirect cooling tower and the balance of draft and resistance during the operation process; According to the thermal balance calculation of the indirect cooling tower, obtain the face velocity vf and the air inflow rate Ga; Finally, according to the louver resistance ∆Pbj and the louver opening calculation formula, obtain the louver opening.

3. The calculation method for overall regulating the opening degree of the louver of an indirect air cooling tower according to claim 1, characterized in that: The face velocity vf and the louver opening Kd are determined by the trial method or the bisection method.

Images