Implementation method of water-saving design of a mist-eliminating cooling tower

Abstract

The application discloses a kind of fog dissipating cooling tower water-saving design implementation methods, comprising the following steps: step one, fog dissipating cooling tower parameter setting unit;Step two, fog dissipating cooling tower packing parameter setting unit;Step three, fog dissipating cooling tower heat transfer performance design unit;Step four, the resistance design unit of fog dissipating module cold and hot channel;Step five, the design unit of air inlet resistance;Step six, the design unit of monthly average water-saving rate.It has the following advantages: the size of fog dissipating module and the parameter of operation are more accurately designed with the water-saving rate of the whole year as the guide, accurate air parameters are obtained, precise water loss and water-saving calculation is achieved throughout the year, so that the design of fog dissipating cooling tower is optimized, and better water-saving effect evaluation is achieved.

Description

Technical Field

[0001] This invention is a method for implementing a water-saving design for a mist-eliminating cooling tower, belonging to the field of cooling tower data processing technology. Background Technology

[0002] Currently, defogging cooling towers are widely used in the petroleum, chemical, and civil refrigeration industries. These towers cool saturated, humid air exiting the packing material through indirect heat exchange within the modules, causing the saturated air temperature to decrease and condensation to form. Existing designs often only consider defogging requirements, and water-saving rate calculations typically only consider the operating conditions at the defogging point. There is also no good method for calculating whether the cooling tower can meet the designed annual water-saving requirements. Furthermore, there is no quick way to assess the relationship between water-saving economics and investment. Therefore, an effective method is needed to solve these problems.

[0003] Patent No. CN109029007 B describes a design calculation method for a newly constructed mechanical ventilation defogging cooling tower. However, this technical solution only designs the cooling tower based on the defogging point operating conditions and does not consider year-round water conservation. Furthermore, in the resistance design process, it fails to consider the impact of the module design on resistance, only using the inlet size of the defogging module to design the resistance balance between the wet and dry sections, thus exhibiting design limitations.

[0004] Patent application CN102799762A, entitled "A Method for Calculating the Formation of Plumes from Hot and Humid Airflow at the Outlet of a Cooling Tower," describes a method that uses coupled nonlinear equations based on the conservation laws of mass, momentum, and energy to calculate plume parameters. However, this theoretical model-based method may not fully account for complex factors in actual operating conditions, such as the complex airflow environment around the cooling tower, rapid changes in air humidity, and complex heat exchange between the plume and the surrounding environment. This could lead to discrepancies between the calculated results and actual conditions under certain special circumstances. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for implementing water-saving design of a fog-reducing cooling tower, which takes the annual water saving rate as a guide to more accurately design the size and operating parameters of the fog-reducing module, obtain accurate air parameters at the tower outlet, and achieve accurate water loss and water saving calculation throughout the year, thereby optimizing the design of the fog-reducing cooling tower and achieving better water-saving effect evaluation.

[0006] To solve the above technical problems, the present invention adopts the following technical solution: A method for implementing a water-saving design for an anti-fogging cooling tower includes the following steps: Step 1: Setting parameters for the defogging cooling tower; Step 2: Setting parameters for the cooling tower packing material; Step 3, Design unit for heat exchange performance of defogging cooling tower; Step 4: Resistance design unit for the hot and cold channels of the defogging module; Step 5, Design unit for air inlet resistance; Step six, design unit for average monthly water saving rate.

[0007] Furthermore, step one includes the following steps: Step S1: Determine meteorological parameters for each month: ambient atmospheric pressure Ambient dry bulb temperature Ambient wet-bulb temperature Calculate the average atmospheric pressure for the whole year in December. Average ambient dry bulb temperature Average ambient wet-bulb temperature Calculate the relative humidity of moist air under the current environmental conditions using thermodynamic formulas. Enthalpy of moist air ; Step S2: Determine the annual average temperature and the annual target water saving rate. .

[0008] Furthermore, step two includes the following steps: Step S3: Determine the designed circulating water volume Inlet water temperature Outlet water temperature and the thermodynamic properties of the packing material used. A represents the area of ​​the defogging module; Step S4: Solve the Michael model using the Simpson integral method to obtain the thermodynamic performance N of the packing material, and determine the air-to-water ratio in the humid heat section of the cooling tower. According to the determined Calculate the amount of dry air required for cooling the current circulating water. air-to-water ratio Dry air volume Specific circulating water volume Given the circulating water volume and That can be obtained ; According to the Michael model, assuming the air exiting the tower is 100% saturated, the dry-bulb and wet-bulb temperatures of the exiting air can be calculated using thermodynamic formulas. , Simultaneously calculate the moisture content of the humid air exiting the packing. enthalpy of moist air Then the evaporation rate is equal to the dry air mass flow rate multiplied by the evaporation rate of the conventional part of the fog-eliminating tower. ; Calculate the resistance at the lower air inlet based on the determined cooling tower dimensions and airflow in the wet zone. Packing resistance Water collector resistance The total resistance of the conventional section is reduced to .

[0009] Step three includes the following steps: Step S5: Based on the structural dimensions of the cooling tower, determine the size and spacing of the selected anti-fogging modules, and calculate the number of rows of anti-fogging modules and the total heat exchange area; Step S6: Based on the determined annual target water saving rate Dry air volume at the packing material outlet The water-saving rate is calculated based on the change in the moisture content of the air. First, the amount of water required for condensation is calculated. The moisture content of the thermal channel of the defogging module can be calculated using this formula. Since the air is saturated, the current air temperature at the outlet of the hot passage can be calculated using thermodynamic formulas. The enthalpy of the moist air at the hot passage outlet is ; Step S7: First, assume the air temperature at the cold aisle outlet of an anti-fogging module. Subsequent calculations will be carried out based on the cold aisle outlet temperature. Step S8: Calculate the heat exchange within the defogging module based on the air parameters and dry air flow rate at the inlet and outlet of the hot channel of the defogging module. ; Hypothetical air temperature at the cold aisle exit The humidity content of the cold aisle air remains constant. Using the humidity content, the assumed air temperature t3, and atmospheric pressure, the enthalpy of the outlet air can be calculated using thermodynamic formulas. Furthermore, the air volume can be determined using thermal equilibrium. Based on heat balance and thermodynamic formulas, the air volume in the cold aisle can be calculated. ; Step S9: Based on the structural dimensions of the defogging module, the air volume in the hot and cold channels within the defogging module, and the inlet and outlet air parameters, calculate the overall heat transfer coefficient of the defogging module using empirical formulas. Calculate the current logarithmic mean temperature difference based on the air temperatures at the inlet and outlet of the hot and cold aisles of the defogging module. , ,in , T1 - Hot flow inlet temperature, t1 - Cold flow inlet temperature, T2 - Hot flow outlet temperature, t2 - Cold flow outlet temperature. Calculate the area of ​​the defogging module based on the determined dimensions. The actual heat exchange is ; Step S10: Based on the actual heat exchange The heat exchange calculated in step S8 The comparison is performed to determine whether the current structure and parameters meet the process design requirements; if they do, then... equal If the condition is met, proceed to the next step. If not, readjust the air temperature t3 in step S7. Greater than Then the air temperature t3 will increase. Less than Then lower the air temperature t3 and repeat steps S7 to S10.

[0010] Furthermore, step four includes the following steps: Step S11: After the heat exchange performance meets the design requirements, calculate the resistance of the thermal channel of the defogging module according to the resistance calculation formula in the channel. ; Step S12: Calculate the resistance of the cold aisle of the defogging module according to the resistance calculation formula within the aisle. ; Step S13: Check the resistance of the hot and cold aisles. In the mixing section, the static pressure is the static pressure of the fan, and the resistance of the hot and cold aisles is balanced. The cold-side resistance is: module resistance + cold air inlet louver resistance; the hot-side resistance is: anti-fogging module hot aisle resistance + conventional section resistance. Therefore, it is required that... If the design requirements are met, then we can proceed to the next step. If necessary, the spacing between the modules of the defogging module needs to be readjusted, and the calculation steps S5 to S13 need to be repeated.

[0011] Furthermore, step five includes the following steps: Step S14: When the resistance of the cold aisle of the defogging module meets the requirements, the air volume of the cold aisle is calculated according to step S8. The air inlet height is designed according to an air inlet velocity of 7 m / s; Step S15: Determine the area of ​​the air inlet based on its height, and calculate the resistance of the air inlet based on the air volume and the area of ​​the air inlet. The total resistance from the cold aisle to the mixing section of the cooling tower is... ; Step S16: The total resistance of the hot channel from the inlet to the mixing section of the cooling tower is Since the hot aisle air enters from the lower air inlet, passes through various components, and then enters the module's hot aisle, the resistance of each part is added together. Step S17: When and When the difference is less than 1 Pa, the design requirements are met, and the process proceeds to the next step. When the difference is large, the corresponding louver height is adjusted, and the calculation steps S14 to S17 are repeated.

[0012] Furthermore, step six includes the following steps: Step S18: Based on the determined defogging module and the air volume of the hot and cold aisles, calculate the water saving rate for each month of operation of the defogging tower according to the meteorological conditions of each month. Repeat steps S2 to S10 for the same calculation. The dry air flow rate in step S4 and the air volume of the cold aisle in step S8 are also included. The airflow should be consistent with the previous steps; Step S19: Determine whether the current monthly average water saving rate meets the annual target water saving rate. If the calculation result does not meet the annual target water saving rate requirement, the water saving rate of the design point shall be increased and the calculation shall be recalculated according to steps S2 to S19.

[0013] The present invention adopts the above technical solution and has the following technical effects compared with the prior art: Guided by the annual water saving rate, the size and operating parameters of the defogging module are designed more accurately. The size and spacing of the defogging module are optimized, thereby changing the number of rows and the overall heat exchange area of ​​the defogging module. This yields accurate air parameters exiting the tower, enabling precise calculation of water loss and water saving throughout the year. As a result, the design of the defogging cooling tower is optimized, leading to a better evaluation of water saving performance. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0015] Figure 1 This is a flowchart illustrating the overall process of a water-saving design calculation method for an anti-fogging cooling tower according to the present invention. Figure 2 This is a schematic diagram of the layout of a fog-reducing cooling tower, illustrating the water-saving design calculation method for fog-reducing cooling towers according to the present invention. Figure 3 This is a schematic diagram showing the monthly water saving rate calculation results of this invention. Detailed Implementation

[0016] Examples, such as Figures 1 to 3 As shown, a method for implementing a water-saving design for an anti-fogging cooling tower includes the following steps: Step 1, the parameter setting unit for the defogging cooling tower, includes the following steps: Step S1: Determine meteorological parameters for each month: ambient atmospheric pressure (kPa), ambient dry bulb temperature (°C), ambient wet-bulb temperature (°C), calculate the average atmospheric pressure for the entire year in December. (kPa), average ambient dry-bulb temperature (°C), average ambient wet-bulb temperature (°C), calculate the relative humidity of the moist air under the current environmental conditions using thermodynamic formulas. Enthalpy of moist air The calculations here are well-known techniques and will not be described in detail. Step S2: Determine the annual average temperature and the annual target water saving rate. .

[0017] Step two, the parameter setting unit for the defogging cooling tower packing, includes the following steps: Step S3: Determine the designed circulating water volume (m3 / h), inlet water temperature (°C), water outlet temperature (°C) and the thermodynamic properties of the packing material used A represents the area of ​​the defogging module; Step S4: Solve the Michael model using the Simpson integral method to obtain the thermodynamic performance N of the packing material, and determine the air-to-water ratio in the humid heat section of the cooling tower. According to the determined Calculate the amount of dry air required for cooling the current circulating water. (kg / h), air-to-water ratio Dry air volume Specific circulating water volume Given the circulating water volume and That can be obtained .

[0018] According to the Michael model, assuming the air exiting the tower is 100% saturated, and based on thermodynamic calculation formulas, the dry-bulb and wet-bulb temperatures of the current air exiting the tower can be calculated as follows: [Dry-bulb temperature values ​​are missing from original text]. (°C) (°C), simultaneously calculate the moisture content of the humid air exiting the packing. enthalpy of moist air Then the evaporation rate is equal to the dry air mass flow rate multiplied by the evaporation rate of the conventional part of the fog-eliminating tower. Alternatively, the Popper model can be used to calculate the dry-bulb and wet-bulb temperatures of the air in the tower. (°C) (°C).

[0019] Calculate the resistance at the lower air inlet based on the determined cooling tower dimensions and airflow in the wet zone. Packing resistance Water collector resistance The total resistance of the conventional section is reduced to .

[0020] Step 3, the heat exchange performance design unit for the defogging cooling tower, includes the following steps: Step S5: Based on the structural dimensions of the cooling tower, determine the size and spacing of the selected anti-fogging modules, and calculate the number of rows of anti-fogging modules and the total heat exchange area; Step S6: Based on the determined annual target water saving rate Dry air volume at the packing material outlet The water-saving rate is calculated based on the change in the moisture content of the air. First, the amount of water required for condensation is calculated. The moisture content of the thermal channel of the defogging module can be calculated using this formula. Since the air is saturated, the current air temperature at the outlet of the hot passage can be calculated using thermodynamic formulas. The enthalpy of the moist air at the hot passage outlet is ; Step S7: First, assume the air temperature at the cold aisle outlet of an anti-fogging module. Subsequent calculations will be carried out based on the cold aisle outlet temperature. Step S8: Calculate the heat exchange within the defogging module based on the air parameters and dry air flow rate at the inlet and outlet of the hot channel of the defogging module. ; Hypothetical air temperature at the cold aisle exit The humidity content of the cold aisle air remains constant. Using the humidity content, the assumed air temperature t3, and atmospheric pressure, the enthalpy of the outlet air can be calculated using thermodynamic formulas. Furthermore, the air volume can be determined using thermal equilibrium. Based on heat balance and thermodynamic formulas, the air volume in the cold aisle can be calculated. ; Step S9: Based on the structural dimensions of the defogging module, the air volume in the hot and cold channels within the defogging module, and the inlet and outlet air parameters, calculate the overall heat transfer coefficient of the defogging module using empirical formulas. Calculate the current logarithmic mean temperature difference based on the air temperatures at the inlet and outlet of the hot and cold aisles of the defogging module. , ,in , T1 - Hot flow inlet temperature, t1 - Cold flow inlet temperature, T2 - Hot flow outlet temperature, t2 - Cold flow outlet temperature. Calculate the area of ​​the defogging module based on the determined dimensions. The actual heat exchange is ; Step S10: Based on the actual heat exchange The heat exchange calculated in step S8 The comparison is performed to determine whether the current structure and parameters meet the process design requirements; if they do, then... equal If the condition is met, proceed to the next step. If not, readjust the air temperature t3 in step S7. Greater than Then the air temperature t3 will increase. Less than Then lower the air temperature t3 and repeat steps S7 to S10.

[0021] Step four, the resistance design unit of the hot and cold aisles of the defogging module, includes the following steps: Step S11: After the heat exchange performance meets the design requirements, calculate the resistance of the thermal channel of the defogging module according to the resistance calculation formula in the channel. ; Step S12: Calculate the resistance of the cold aisle of the defogging module according to the resistance calculation formula within the aisle. ; Step S13: Check the resistance of the hot and cold aisles. In the mixing section, the static pressure is the static pressure of the fan, and the resistance of the hot and cold aisles is balanced. The cold-side resistance is: module resistance + cold air inlet louver resistance; the hot-side resistance is: anti-fogging module hot aisle resistance + conventional section resistance. Therefore, it is required that... If the design requirements are met, then we can proceed to the next step. If necessary, the spacing between the modules of the defogging module needs to be readjusted, and the calculation steps S5 to S13 need to be repeated.

[0022] Step 5, the design unit for air inlet resistance, includes the following steps: Step S14: When the resistance of the cold aisle of the defogging module meets the requirements, the air volume of the cold aisle is calculated according to step S8. The air inlet height is designed according to an air inlet velocity of 7 m / s; Step S15: Determine the area of ​​the air inlet based on its height, and calculate the resistance of the air inlet based on the air volume and the area of ​​the air inlet. The total resistance from the cold aisle to the mixing section of the cooling tower is... ; Step S16: The total resistance of the hot channel from the inlet to the mixing section of the cooling tower is Since the hot aisle air enters from the lower air inlet, passes through various components, and then enters the module's hot aisle, the resistance of each part is added together. Step S17: When and When the difference is less than 1 Pa, the design requirements are met, and the process proceeds to the next step. When the difference is large, the corresponding louver height is adjusted, and the calculation steps S14 to S17 are repeated.

[0023] Step six, the design unit for the average monthly water saving rate, includes the following steps: Step S18: Based on the determined defogging module and the air volume of the hot and cold aisles, calculate the water-saving rate for each month of operation of the defogging tower (the defogging mode is off by default in July, August, and September) according to the monthly meteorological conditions. The calculation of the water-saving rate has been disclosed in the patent and will not be repeated here. Repeat steps S2 to S10 for the same calculation. The dry air flow rate in step S4 and the air volume of the cold aisle in step S8 are also included. The airflow should be consistent with the steps above.

[0024] Step S19: Determine whether the current monthly average water saving rate meets the annual target water saving rate. If the calculated water-saving rate does not meet the annual target, the water-saving rate at the design point should be increased, and the calculation should be repeated according to steps S2 to S19. The calculated monthly water-saving rate and the water-saving rate at the design point are as follows: Figure 3 As shown.

[0025] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for implementing a water-saving design for an anti-fogging cooling tower, characterized in that: Includes the following steps: Step 1: Setting parameters for the defogging cooling tower; Step 2: Setting parameters for the cooling tower packing material; Step 3, Design unit for heat exchange performance of defogging cooling tower; Step 4: Resistance design unit for the hot and cold channels of the defogging module; Step 5, Design unit for air inlet resistance; Step six, design unit for average monthly water saving rate; Step two includes the following steps: Step S3: Determine the designed circulating water volume Inlet water temperature Outlet water temperature and the thermodynamic properties of the packing material used. A represents the area of ​​the defogging module; Step S4: Solve the Michael model using the Simpson integral method to obtain the thermodynamic performance N of the packing material, and determine the air-to-water ratio in the humid heat section of the defogging cooling tower. According to the determined Calculate the amount of dry air required for cooling the current circulating water. air-to-water ratio Dry air volume Specific circulating water volume Given the circulating water volume and That can be obtained ; According to the Michael model, assuming the air exiting the tower is 100% saturated, the dry-bulb and wet-bulb temperatures of the exiting air can be calculated using thermodynamic formulas. , Simultaneously calculate the moisture content of the humid air exiting the packing. enthalpy of moist air Then the evaporation rate is equal to the dry air mass flow rate multiplied by the evaporation rate of the conventional part of the defogging cooling tower. ; Based on the determined dimensions of the defogging cooling tower and the airflow in the humid zone, calculate the resistance at the lower air inlet. Packing resistance Water collector resistance The total resistance of the conventional section is reduced to ; Step three includes the following steps: Step S5: Based on the structural dimensions of the defogging cooling tower, determine the size and spacing of the selected defogging modules, and calculate the number of rows of defogging modules and the total heat exchange area; Step S6: Based on the determined annual target water saving rate Dry air volume at the packing material outlet The water-saving rate is calculated based on the change in the humidity content of the air. First, the amount of water required for condensation is calculated. The moisture content of the thermal channel of the defogging module can be calculated using this formula. Since the air is saturated, the current air temperature at the outlet of the hot passage can be calculated using thermodynamic formulas. The enthalpy of the moist air at the hot passage outlet is ; Step S7: First, assume the air temperature at the cold aisle outlet of an anti-fogging module. According to air temperature To carry out subsequent calculations; Step S8: Calculate the heat exchange within the defogging module based on the air parameters and dry air flow rate at the inlet and outlet of the hot channel of the defogging module. ; Hypothetical air temperature at the cold aisle exit The humidity content of the air in the cold aisle remains constant before and after. Using the humidity content, the assumed air temperature is... Using atmospheric pressure and thermodynamic formulas, the enthalpy of the outlet air can be calculated, and then the air volume can be determined using thermal equilibrium. ; Step S9: Based on the structural dimensions of the defogging module, the air volume in the hot and cold channels within the defogging module, and the inlet and outlet air parameters, calculate the overall heat transfer coefficient of the defogging module using empirical formulas. Calculate the current logarithmic mean temperature difference based on the air temperatures at the inlet and outlet of the hot and cold aisles of the defogging module. , ,in , T1 - Hot flow inlet temperature, t1 - Cold flow inlet temperature, T2 - Hot flow outlet temperature, t2 - Cold flow outlet temperature. Calculate the area of ​​the defogging module based on the determined dimensions. The actual heat exchange is ; Step S10: Based on the actual heat exchange The heat exchange calculated in step S8 The comparison is performed to determine whether the current structure and parameters meet the process design requirements; if they do, then... equal If the condition is met, proceed to the next step. If not, readjust the air temperature t3 in step S7. Greater than Then the air temperature t3 will increase. Less than Then lower the air temperature t3 and repeat steps S7 to S10.

2. The method for implementing the water-saving design of an anti-fogging cooling tower as described in claim 1, characterized in that: Step one includes the following steps: Step S1: Determine meteorological parameters for each month: ambient atmospheric pressure Ambient dry bulb temperature Ambient wet-bulb temperature Calculate the average atmospheric pressure for the whole year in December. Average ambient dry bulb temperature Average ambient wet-bulb temperature Calculate the relative humidity of moist air under the current environmental conditions using thermodynamic formulas. Enthalpy of moist air ; Step S2: Determine the annual average temperature and the annual target water saving rate. .

3. The method for implementing the water-saving design of an anti-fogging cooling tower as described in claim 1, characterized in that: Step four includes the following steps: Step S11: After the heat exchange performance meets the design requirements, calculate the resistance of the thermal channel of the defogging module according to the resistance calculation formula in the channel. ; Step S12: Calculate the resistance of the cold aisle of the defogging module according to the resistance calculation formula within the aisle. ; Step S13: Check the resistance of the hot and cold aisles. In the mixing section, the static pressure is the static pressure of the fan, and the resistance of the hot and cold aisles is balanced. The cold-side resistance is: module resistance + cold air inlet louver resistance; the hot-side resistance is: anti-fogging module hot aisle resistance + conventional section resistance. Therefore, it is required that... If the design requirements are met, then we can proceed to the next step. If necessary, the spacing between the modules of the defogging module needs to be readjusted, and the calculation steps S5 to S13 need to be repeated.

4. The method for implementing the water-saving design of an anti-fogging cooling tower as described in claim 3, characterized in that: Step five includes the following steps: Step S14: When the resistance of the cold aisle of the defogging module meets the requirements, the air volume of the cold aisle is calculated according to step S8. The air inlet height is designed according to an air inlet velocity of 7 m / s; Step S15: Determine the area of ​​the air inlet based on its height, and calculate the resistance of the air inlet based on the air volume and the area of ​​the air inlet. The total resistance from the cold aisle to the mixing section of the defogging cooling tower is... ; Step S16: The total resistance of the hot channel from the inlet to the mixing section of the defogging cooling tower is... Since the hot aisle air enters from the lower air inlet, passes through various components, and then enters the module's hot aisle, the resistance of each part is added together. Step S17: When and When the difference is less than 1 Pa, the design requirements are met, and the next step is performed. When the difference is large, the corresponding louver height is adjusted, and the calculation steps S14 to S17 are repeated.

5. The method for implementing the water-saving design of an anti-fogging cooling tower as described in claim 3, characterized in that: Step six includes the following steps: Step S18: Based on the determined defogging module and hot and cold aisle airflow, calculate the water saving rate for each month of operation of the defogging cooling tower according to the monthly meteorological conditions. Repeat steps S2 to S10 for this calculation. The dry air flow rate in step S4 and the air volume in the cold aisle in step S8 are calculated separately. The air volume should be consistent with that in steps S2 to S17; Step S19: Determine whether the current monthly average water saving rate meets the annual target water saving rate. If the calculation results do not meet the annual target water saving rate, the water saving rate at the design point shall be increased and the calculation shall be recalculated according to steps S2 to S19.

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