Method for measuring and calculating fouling resistance of water-cooled condenser heat transfer pipe

Abstract

The present application relates to a kind of water condenser heat transfer tube fouling thermal resistance measurement method, comprising the following steps, S1, obtain the design parameter of water condenser;S2, obtain the performance design parameter of water condenser in design condition;S3, respectively obtain the operating parameter of condenser in test condition 1 and test condition 2;S4, under a certain assumed water condenser heat transfer tube fouling thermal resistance, test condition condenser is corrected to the condenser pressure p c Under the boundary condition of design;S5, according to step S1 to step S4, obtain the water condenser heat transfer tube fouling thermal resistance.The present application can realize the periodic or periodic evaluation of water condenser heat transfer tube fouling thermal resistance change, and provide guidance for taking appropriate operation and maintenance strategy, facilitate on-site implementation.

Description

Technical Field

[0001] This invention belongs to the field of fouling thermal resistance monitoring technology for water-cooled condensers, specifically relating to a method for calculating the fouling thermal resistance of heat transfer tubes in water-cooled condensers. Background Technology

[0002] Condensing equipment is a crucial component of condensing steam turbine units, and its operation directly impacts the overall thermal economy and operational reliability of the unit. Condensing equipment acts as a cold source in the thermodynamic cycle of the steam turbine unit. Reducing the pressure and temperature of the turbine exhaust steam minimizes cold source losses and improves cycle thermal efficiency. An effective way to reduce exhaust steam parameters is to introduce the exhaust steam into the condenser to condense it into water. If improper unit operation causes the exhaust steam pressure to increase by 1% above normal, Δηt / ηt will decrease by more than 1%; if the exhaust steam temperature drops by 5°C, Δηt / ηt will increase by more than 1%. This is significant for large units, highlighting the importance of condensing equipment. Condensing equipment using water as the cooling medium generally consists of a condenser, condensate pump, extraction equipment, circulating water pump, and connecting pipes and accessories between them.

[0003] As the most important heat exchanger equipment in power plant generator units, wet condensers play a crucial role in dissipating the heat from the unit's exhaust steam to the environment. With the development of power units towards larger capacity and higher parameters, the performance of wet condensers in power plants has an increasingly significant impact on the plant's economic efficiency. Taking a 600MW wet-cooled turbine unit as an example, every 1 kPa increase in condenser pressure directly increases the unit's coal consumption for power generation by approximately 3.3 g / kW·h, resulting in an additional consumption of approximately 8910 tons of standard coal annually. The fouling thermal resistance of the heat transfer tubes in water-cooled condensers is a significant factor affecting condenser heat exchange. However, because the performance of power plant unit condensers is influenced by multiple factors during normal operation, such as unit load, circulating water flow rate, circulating water inlet temperature, and the cleanliness of the heat exchange tubes, simply monitoring changes in condenser pressure cannot objectively assess changes in the fouling thermal resistance of the water-cooled condenser's heat transfer tubes. Chinese Patent Application No. 201710757914.6 discloses an online monitoring method for condenser fouling, comprising: establishing a turbine variable operating condition performance model; calculating condenser steam-water parameters based on the turbine variable operating condition performance model; calculating the overall heat transfer resistance of the condenser based on the condenser steam-water parameters; calculating the convective heat transfer resistance on the water side of the condenser cooling pipes, the thermal conductivity resistance of the cooling pipe wall, and the condensation heat transfer coefficient on the gas side of the condenser, and correcting the gas side condensation heat transfer coefficient to obtain the gas side condensation heat transfer resistance; calculating the condenser fouling resistance based on the overall heat transfer resistance of the condenser, the convective heat transfer resistance on the water side of the cooling pipes, the thermal conductivity resistance of the cooling pipe wall, and the condensation heat transfer resistance on the gas side, and using the magnitude of the fouling resistance to represent the water side cleanliness of the condenser, thereby achieving online monitoring of condenser fouling. Chinese patent application number 2008101439928 discloses a method for predicting the trend of fouling changes in large condensers. Existing technologies lack an objective assessment of the changes in the thermal resistance of fouling on the heat transfer tubes of water-cooled condensers. Therefore, there is an urgent need for an experimental and calculation method to determine the thermal resistance of fouling on the heat transfer tubes of water-cooled condensers to address the current problems encountered in the field. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser. This method can periodically or cyclically assess the changes in the fouling thermal resistance of the heat transfer tubes in a water-cooled condenser and provide guidance for adopting appropriate operation and maintenance strategies, making it easy to implement on-site.

[0005] The technical solution adopted in this invention is:

[0006] This invention discloses a method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser, comprising the following steps:

[0007] S1, obtain the design parameters of the water-cooled condenser;

[0008] S2, obtain the performance design parameters of the water-cooled condenser under the design conditions;

[0009] S3, obtain the operating parameters of the condenser under test condition 1 and test condition 2 respectively;

[0010] S4, Calculate the condenser pressure p under the test condition, corrected to the design boundary conditions, under a certain assumed fouling thermal resistance of the water-cooled condenser heat transfer tubes. c ;

[0011] S5. Based on steps S1 to S4, calculate the fouling thermal resistance of the heat transfer tubes of the water condenser.

[0012] Further, in step S1, the design parameters include the number of design processes, the condenser design area A, the condenser tube type, the condenser tube model, the condenser tube outer diameter, the condenser tube wall thickness, the condenser tube inner diameter, the condenser tube length, and the number of condenser tubes.

[0013] Furthermore, in step S2, the performance design parameters include circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature, condenser pressure, and condenser design cleanliness factor.

[0014] Further, in step S3, the test condition 1 is that the unit load is controlled at 100% load, the test circulating water inlet temperature is close to the design inlet temperature value, and the deviation is less than ±6℃. The operating parameters of test condition 1 are recorded, including circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature and condenser pressure.

[0015] Further, in step S3, the test condition 2 is that the unit load is controlled at 95% load, the test circulating water inlet temperature is close to the design inlet temperature value with a deviation of less than ±6℃, and the difference between the test circulating water inlet temperature and the test condition 1 is within 5℃; the operating parameters of test condition 2 are recorded, including circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature and condenser pressure.

[0016] Further, in step S4, the condenser pressure p of the condenser under the test condition, corrected to the design boundary conditions, is calculated under the assumed fouling thermal resistance of the water-cooled condenser heat transfer tubes. c The calculation process includes the following steps:

[0017] (1) Calculate the heat transfer characteristic parameters of the condenser under test conditions, including the following steps:

[0018] 1-a, Calculate the condenser heat load under the test conditions;

[0019] 1-b, Calculate the overall heat transfer coefficient of the condenser under the test conditions;

[0020] 1-c, Calculate the heat transfer resistance of the pipe wall under the test conditions;

[0021] 1-d, calculate the tube-side heat transfer thermal resistance under the test conditions;

[0022] 1-e, the pipe-side fouling thermal resistance under the test conditions is calculated using an assumed value;

[0023] 1-f, Calculate the shell-side thermal resistance under the test conditions;

[0024] (2) Calculate the heat transfer characteristic parameters of the condenser corrected to the design operating condition boundary conditions, including the following steps:

[0025] 2-a, Calculate the heat transfer resistance of the pipe wall under the design conditions;

[0026] 2-b, Calculate the tube-side heat transfer thermal resistance under design conditions;

[0027] 2-c, Calculate the pipe-side fouling thermal resistance under design conditions;

[0028] 2-d, calculate the shell-side thermal resistance corrected to the design conditions;

[0029] 2-e, corrected to the overall heat transfer coefficient under design conditions.

[0030] (3) Calculate the condenser pressure corrected to the design operating condition boundary conditions, including the following steps.

[0031] 3-a. Obtain the number of heat exchange units (NTUs) corrected to the design boundary conditions. tc ;

[0032] 3-b. Obtain the condenser pressure p corrected to the design operating condition boundary conditions. c .

[0033] Furthermore, in 1-a, the formula for calculating the condenser heat load is:

[0034] Q T =G wT ·C P ·(t 2T -t 1T ) / 3.6

[0035] In the formula: Q T For the condenser operating heat load, W;t 2T The outlet temperature of the condenser circulating water is expressed in °C (t). 1T The inlet water temperature of the condenser circulating water is expressed in °C (G). wT The circulating water flow rate is kg / h; C P The specific heat capacity of the circulating water is 4.186 kJ / (kg·℃).

[0036] In section 1-b, the formula for calculating the overall heat transfer coefficient of the condenser is:

[0037]

[0038] In the formula, U t The overall heat transfer coefficient of the condenser is W / (m²). 2 .℃); A is the condenser area, m 2 LMTD is the logarithmic mean temperature difference, in °C.

[0039] The logarithmic mean temperature difference is calculated using the following formula:

[0040]

[0041] In the formula: t sT is the saturation temperature corresponding to the condenser pressure, in °C;

[0042] In 1-c, the formula for calculating the heat transfer resistance of the pipe wall is:

[0043]

[0044] In the formula, D o With D i These are the outer and inner diameters of the heat exchanger tubes, in meters (m); R m The heat transfer resistance of the pipe wall is expressed in m².K / W; k m The thermal conductivity of the heat exchanger tube is expressed in W / mK.

[0045] In step 1-d, the formula for calculating the tube-side thermal resistance is:

[0046]

[0047] in,

[0048]

[0049]

[0050]

[0051] In the formula, R t The tube-side heat transfer thermal resistance is expressed in m²·K / W; Pr is Prandtl number; Re is Reynolds number; k is the thermal conductivity of the medium, expressed in W / mK; μ is the dynamic viscosity of the medium, expressed in Pa·s; ρ is the density of the medium, expressed in kg / m³; v is the flow velocity of the medium in the tube, expressed in m / s; N is the number of heat exchange tubes in the condenser; n is the number of shell-side tubes in the condenser; when calculating the thermal conductivity, dynamic viscosity, and density of the medium, the characteristic temperature of the medium is taken as the average temperature of the condenser circulating water inlet and outlet under the test conditions.

[0052] In 1-e, R f =R fg ;

[0053] In the formula, R f For the tube-side fouling thermal resistance under test conditions; R fg This is a assumed thermal resistance value for fouling on the pipe side under test conditions.

[0054] In 1-f, the thermal resistance R of the shell side is... s The calculation formula is:

[0055]

[0056] Furthermore, 2-a, the calculation formula is:

[0057] R md =R m

[0058] In the formula, R md The heat transfer resistance of the pipe wall under design conditions;

[0059] 2-b, the calculation formula is:

[0060]

[0061] in,

[0062]

[0063]

[0064]

[0065] In the formula, R td The design tube-side thermal resistance is expressed in m².K / W; Prd is the design Prandtl number; Red is the design Reynolds number; k d Thermal conductivity of the medium under design conditions, in W / mK; μ d The dynamic viscosity of the medium under design operating conditions is expressed in Pa·s; ρ d The density of the medium under design conditions, in kg / m³ 3 ;v d The flow velocity in the pipe under design conditions is given in m / s. When calculating the thermal conductivity, dynamic viscosity, and density of the medium, the characteristic temperature of the medium is taken as the average temperature of the condenser circulating water inlet and outlet under design conditions.

[0066] The calculation process for 2-c includes the following steps:

[0067] i) Calculate the overall heat transfer coefficient under design conditions

[0068] The overall heat transfer coefficient of the condenser under design conditions is calculated using the following formula:

[0069]

[0070] The logarithmic mean temperature difference under design conditions is calculated using the following formula:

[0071]

[0072] In the formula, the parameters marked with the subscript "d" all correspond to the parameters under the design conditions;

[0073] ii) Calculate the fouling factor on the heat exchanger tube side under design conditions.

[0074]

[0075] In the formula, R fd β is the fouling factor of the heat exchanger tube under design conditions, in m2.K / W. cd This is the design value for the pipe cleanliness coefficient under the design operating conditions.

[0076] The formula for calculating 2-d is:

[0077]

[0078] In the formula, R sd The shell-side thermal resistance under design conditions, in meters (m). 2 .K / W; μ s The dynamic viscosity of the shell-side liquid medium under test conditions is expressed in Pa·s and kJ / kJ. s The thermal conductivity of the shell-side liquid medium under test conditions is expressed in W / mK; ρ s Density of the shell-side liquid medium under test conditions, in kg / m³ 3 Parameters marked with the subscript "d" correspond to parameters under design conditions. When solving for the physical properties of the medium under experimental conditions, the shell-side liquid film temperature t is used. f =t sT Calculated using -0.2×LMTD; when solving for the physical property parameters of the medium under design conditions, the shell-side medium liquid film temperature t is used. fs =t sd -0.2×LMTD d calculate;

[0079] The formula for calculating 2-e is:

[0080]

[0081] In the formula, U tc To correct for the overall heat transfer coefficient under design conditions, the unit is W / (m²). 2 .℃);

[0082] The formula for calculating 3-a is:

[0083] Number of heat exchange units (NTU)tc The calculation formula is

[0084]

[0085] In the formula, G wd The circulating water flow rate under design conditions is expressed in kg / h; C Pd The specific heat capacity of the circulating water under design conditions is 4.186 kJ / (kg·℃).

[0086] 3-b condenser pressure p c1 The calculation formula is

[0087]

[0088] p sc =f(t) sc )

[0089] p c =p sc

[0090] In the formula, t sc To correct for the condenser saturation temperature under design conditions, ℃; t 1d t 2d These are the condenser circulating water inlet and outlet temperatures under design conditions, in °C; formula p sc =f(t) sc ).

[0091] Further, in step S5, based on steps S1 to S4, the fouling thermal resistance of the water-cooled condenser heat transfer tubes is calculated, specifically including the following steps:

[0092] (1) Assume the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser. fg Calculate the condenser pressure p under test condition 1 (corrected to the design boundary conditions) according to step S4. c1 And the condenser pressure p under test condition 2, corrected to the design boundary conditions. c2 .

[0093] (2) When Abs(p c1 -p c2 When )≤0.05, it indicates that the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser under the assumed test conditions is... fg Meets requirements; the fouling thermal resistance value R of the water-cooled condenser heat transfer tubes is [value missing]. f =R fg The solution process ends here; Abs() is the absolute value function in the formula.

[0094] Furthermore, when Abs(p c1 -p c2When ) > 0.05, it indicates that the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser under the assumed test conditions is... fg If the requirements are not met, the fouling thermal resistance value of the water-cooled condenser heat transfer tube needs to be re-assumed, and the process should be returned to step (1) for recalculation.

[0095] The beneficial effects of this invention are:

[0096] This invention provides a method for calculating the fouling thermal resistance of heat transfer tubes in water-cooled condensers, solving the problem of accurately assessing the fouling thermal resistance of heat transfer tubes in power plant water-cooled condensers during normal operation.

[0097] This invention employs external measurement and calculation methods, primarily determining the fouling thermal resistance of the heat transfer tubes in a water-cooled condenser by measuring operating parameters under two performance test conditions and using appropriate methods. This invention solves the problem of accurately assessing the fouling thermal resistance of heat transfer tubes in power plant water-cooled condensers during normal operation. It provides quantitative data on the condenser's operating status for power plant operation and maintenance, offering a basis for condition-based condenser maintenance and energy conservation in power plants. Based on the fouling thermal resistance of the water-cooled condenser's heat transfer tubes, the condenser's performance and abnormal conditions can be monitored and assessed, meeting the needs of power plant economic analysis.

[0098] The method of this invention, when used for evaluation, enables periodic or cyclical assessment of the fouling thermal resistance changes of water-cooled condenser heat transfer tubes through on-site testing, and provides guidance for adopting appropriate operation and maintenance strategies. Attached Figure Description

[0099] Figure 1 This is a flowchart illustrating the method for calculating the fouling thermal resistance of the heat transfer tubes in a water-cooled condenser according to the present invention. Detailed Implementation

[0100] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0101] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0102] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0103] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0104] Reference Figure 1 This invention provides a method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser, comprising the following steps:

[0105] S1, obtain the design parameters of the water-cooled condenser.

[0106] In step S1, the design parameters include the number of design processes, the condenser design area A, the condenser tube type, the condenser tube model, the condenser tube outer diameter, the condenser tube wall thickness, the condenser tube inner diameter, the condenser tube length, and the number of condenser tubes.

[0107] S2, obtain the performance design parameters of the water-cooled condenser under the design conditions.

[0108] In step S2, the performance design parameters include circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature, condenser pressure, and condenser design cleanliness factor.

[0109] S3, obtain the operating parameters of the condenser under test condition 1 and test condition 2 respectively.

[0110] In step S3, the test condition 1 is that the unit load is controlled at 100% load, the test circulating water inlet temperature is close to the design inlet temperature value, and the deviation is less than ±6℃. The operating parameters of test condition 1 are recorded. The operating parameters include circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature and condenser pressure.

[0111] In step S3, the test condition 2 is that the unit load is controlled at 95% load, the test circulating water inlet temperature is close to the design inlet temperature value with a deviation of less than ±6℃, and the difference between the test circulating water inlet temperature and the test condition 1 is within 5℃; the operating parameters of test condition 2 are recorded, including circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature and condenser pressure.

[0112] S4, Calculate the condenser pressure p under the test condition, corrected to the design boundary conditions, under a certain assumed fouling thermal resistance of the water-cooled condenser heat transfer tubes. c .

[0113] The calculation process includes the following steps:

[0114] (1) Calculate the heat transfer characteristic parameters of the condenser under test conditions, including the following steps:

[0115] 1-a, Calculate the condenser heat load under the test conditions;

[0116] In section 1-a, the formula for calculating the condenser heat load is:

[0117] Q T =G wT ·C P ·(t 2T -t 1T ) / 3.6

[0118] In the formula: Q T For the condenser operating heat load, W;t 2T The outlet temperature of the condenser circulating water is expressed in °C (t). 1T The inlet water temperature of the condenser circulating water is expressed in °C (G). wT The circulating water flow rate is kg / h; C P The specific heat capacity of the circulating water is 4.186 kJ / (kg·℃).

[0119] 1-b, Calculate the overall heat transfer coefficient of the condenser under the test conditions;

[0120] In section 1-b, the formula for calculating the overall heat transfer coefficient of the condenser is:

[0121]

[0122] In the formula, U tThe overall heat transfer coefficient of the condenser is W / (m²). 2 .℃); A is the condenser area, m 2 LMTD is the logarithmic mean temperature difference, in °C.

[0123] The logarithmic mean temperature difference is calculated using the following formula:

[0124]

[0125] In the formula: t sT is the saturation temperature corresponding to the condenser pressure, in °C;

[0126] 1-c, Calculate the heat transfer resistance of the pipe wall under the test conditions;

[0127] In 1-c, the formula for calculating the heat transfer resistance of the pipe wall is:

[0128]

[0129] In the formula, D o With D i These are the outer and inner diameters of the heat exchanger tubes, in meters (m); R m The heat transfer resistance of the pipe wall is expressed in m².K / W; k m The thermal conductivity of the heat exchanger tube is expressed in W / mK.

[0130] 1-d, calculate the tube-side heat transfer thermal resistance under the test conditions;

[0131] In step 1-d, the formula for calculating the tube-side thermal resistance is:

[0132]

[0133] in,

[0134]

[0135]

[0136]

[0137] In the formula, R t The tube-side thermal resistance is given by: Pr (Plaints number), Re (Reynolds number), k (thermal conductivity of the medium, E / mK), μ (dynamic viscosity of the medium, Pa·s), and ρ (density of the medium, kg / m³). 3 v is the flow velocity of the medium in the tube, in m / s; N is the number of heat exchange tubes in the condenser; n is the number of shell-side tubes in the condenser; when calculating the thermal conductivity, dynamic viscosity and density of the medium, the characteristic temperature of the medium is taken as the average temperature of the condenser circulating water inlet and outlet under the test conditions.

[0138] 1-e, the pipe-side fouling thermal resistance under the test conditions is calculated using an assumed value;

[0139] In 1-e, R f =R fg ;

[0140] In the formula, R f For the tube-side fouling thermal resistance under test conditions; R fg This is a assumed thermal resistance value for fouling on the pipe side under test conditions.

[0141] 1-f, Calculate the shell-side thermal resistance under the test conditions;

[0142] In 1-f, the thermal resistance R of the shell side is... s The calculation formula is:

[0143]

[0144] (2) Calculate the heat transfer characteristic parameters of the condenser corrected to the design operating condition boundary conditions, including the following steps:

[0145] 2-a, Calculate the heat transfer resistance of the pipe wall under the design conditions;

[0146] 2-a, the calculation formula is:

[0147] R md =R m

[0148] In the formula, R md The heat transfer resistance of the pipe wall under design conditions;

[0149] 2-b, Calculate the tube-side heat transfer thermal resistance under design conditions;

[0150] 2-b, the calculation formula is:

[0151]

[0152] in,

[0153]

[0154]

[0155]

[0156] In the formula, R td The design tube-side thermal resistance is expressed in m².K / W; Prd is the design Prandtl number; Red is the design Reynolds number; k d Thermal conductivity of the medium under design conditions, in W / mK; μ d The dynamic viscosity of the medium under design operating conditions is expressed in Pa·s; ρ dThe density of the medium under design conditions, in kg / m³; v d The flow velocity of the medium under design operating conditions is expressed in m / s. When calculating the thermal conductivity, dynamic viscosity, and density of the medium, the characteristic temperature of the medium is taken as the average temperature of the condenser circulating water inlet and outlet under design operating conditions.

[0157] 2-c, Calculate the pipe-side fouling thermal resistance under design conditions;

[0158] The calculation process for 2-c includes the following steps:

[0159] i) Calculate the overall heat transfer coefficient under design conditions

[0160] The overall heat transfer coefficient of the condenser under design conditions is calculated using the following formula:

[0161]

[0162] The logarithmic mean temperature difference under design conditions is calculated using the following formula:

[0163]

[0164] In the formula, the parameters with the subscript "d" all correspond to the parameters under the design conditions; the meanings of the symbols are similar to those of the parameters under the test conditions with the subscript "T" in 1-b, such as LMTD. d The logarithmic mean temperature difference under design conditions is expressed in °C.

[0165] ii) Calculate the fouling factor on the heat exchanger tube side under design conditions.

[0166]

[0167] In the formula, R fd β is the fouling factor of the heat exchanger tube under design conditions, in m2.K / W. cd This is the design value for the pipe cleanliness coefficient under the design operating conditions.

[0168] 2-d, calculate the shell-side thermal resistance corrected to the design conditions;

[0169] The formula for calculating 2-d is:

[0170]

[0171] In the formula, R sd The shell-side thermal resistance under design conditions, in meters (m). 2 .K / W; μ s The dynamic viscosity of the shell-side liquid medium under test conditions is expressed in Pa·s and kJ / kJ. s The thermal conductivity of the shell-side liquid medium under test conditions is expressed in W / mK; ρ sDensity of the shell-side liquid medium under test conditions, in kg / m³ 3 Parameters marked with the subscript "d" correspond to parameters under design conditions. When solving for the physical properties of the medium under experimental conditions, the shell-side liquid film temperature t is used. f =t sT Calculated using -0.2×LMTD; when solving for the physical property parameters of the medium under design conditions, the shell-side medium liquid film temperature t is used. fs =t sd -0.2×LMTD d Calculate; 2-e, corrected to the overall heat transfer coefficient under design conditions.

[0172] The formula for calculating 2-e is:

[0173]

[0174] In the formula, U tc To correct for the overall heat transfer coefficient under design conditions, the unit is W / (m²). 2 .℃);

[0175] (3) Calculate the condenser pressure corrected to the design operating condition boundary conditions, including the following steps.

[0176] 3-a. Obtain the number of heat exchange units (NTUs) corrected to the design boundary conditions. tc ;

[0177] The formula for calculating 3-a is:

[0178] Number of heat exchange units (NTU) tc The calculation formula is

[0179]

[0180] In the formula, G wd The circulating water flow rate under design conditions is expressed in kg / h; C Pd The specific heat capacity of the circulating water under design conditions is 4.186 kJ / (kg·℃).

[0181] 3-b. Obtain the condenser pressure p corrected to the design operating condition boundary conditions. c .

[0182] 3-b condenser pressure p c1 The calculation formula is

[0183]

[0184] p sc =f(t) sc )

[0185] p c=p sc

[0186] In the formula, t sc To correct for the condenser saturation temperature under design conditions, ℃; t 1d t 2d These are the condenser circulating water inlet and outlet temperatures under design conditions, in °C; formula p sc =f(t) sc ).

[0187] S5. Based on the data obtained from steps S1 to S4, calculate the fouling thermal resistance of the heat transfer tubes of the water condenser.

[0188] Step S5, based on steps S1 to S4, calculate the fouling thermal resistance of the water-cooled condenser heat transfer tubes, specifically including the following steps:

[0189] (1) Assume the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser. fg Calculate the condenser pressure p under test condition 1 (corrected to the design boundary conditions) according to step S4. c1 And the condenser pressure p under test condition 2, corrected to the design boundary conditions. c2 .

[0190] (2) When Abs(p c1 -p c2 When )≤0.05, it indicates that the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser under the assumed test conditions is... fg Meets requirements; the fouling thermal resistance value R of the water-cooled condenser heat transfer tubes is [value missing]. f =R fg The solution process ends here; Abs() is the absolute value function in the formula.

[0191] When Abs(p) c1 -p c2 When ) > 0.05, it indicates that the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser under the assumed test conditions is... fg If the requirements are not met, the fouling thermal resistance value of the water-cooled condenser heat transfer tubes needs to be re-assumed, and the process should return to step (1) of step S5 for recalculation. The above-described embodiments are preferred embodiments of the present invention, but not exhaustive examples of all feasible implementations of the present invention. For those skilled in the art, any improvements made without departing from the spirit and essence of the present invention should be considered to be included within the scope of protection of the present invention.

Claims

1. A method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser, characterized in that, Includes the following steps, S1, obtain the design parameters of the water-cooled condenser; S2, obtain the performance design parameters of the water-cooled condenser under the design conditions; S3, obtain the operating parameters of the condenser under test condition 1 and test condition 2 respectively; Test condition 1 involves controlling the unit load at 100% and ensuring the test circulating water inlet temperature is close to the design inlet temperature with a deviation of less than ±6℃. Record the operating parameters for test condition 1. Test condition 2 involves controlling the unit load at 95% and ensuring the test circulating water inlet temperature is close to the design inlet temperature with a deviation of less than ±6℃. Simultaneously, the test circulating water inlet temperature should be within 5℃ of that in test condition 1. Record the operating parameters for test condition 2. The operating parameters include circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature, and condenser pressure. S4, Calculate the condenser pressure p under the test condition, corrected to the design boundary conditions, under a certain assumed fouling thermal resistance of the water-cooled condenser heat transfer tubes. c ; S5. Based on steps S1 to S4, calculate the fouling thermal resistance of the heat transfer tubes in the water-cooled condenser. This specifically includes the following steps: (1) Assume the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser. fg Calculate the condenser pressure p under test condition 1 (corrected to the design boundary conditions) according to step S4. c1 And the condenser pressure p under test condition 2, corrected to the design boundary conditions. c2 ; (2) When Abs(p c1 -p c2 When )≤0.05, it indicates that the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser under the assumed test conditions is... fg Meets requirements; the fouling thermal resistance value R of the water-cooled condenser heat transfer tubes is [value missing]. f =R fg The solution process ends; in the formula, Abs() is the absolute value function; When Abs(p) c1 -p c2 When the value is greater than 0.05, it indicates that the fouling thermal resistance R of the heat transfer tubes of the water-cooled condenser under the assumed test conditions is... fg If the requirements are not met, the fouling thermal resistance value of the water-cooled condenser heat transfer tube needs to be re-assumed, and the process should be returned to step (1) for recalculation.

2. The method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser according to claim 1, characterized in that, In step S1, the design parameters include the number of design processes, the condenser design area A, the condenser tube type, the condenser tube model, the condenser tube outer diameter, the condenser tube wall thickness, the condenser tube inner diameter, the condenser tube length, and the number of condenser tubes.

3. The method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser according to claim 1, characterized in that, In step S2, the performance design parameters include circulating water flow rate, circulating water inlet temperature, circulating water outlet temperature, condenser pressure, and condenser design cleanliness factor.

4. The method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser according to claim 1, characterized in that, Step S4 calculates the condenser pressure p under the test condition, corrected to the design boundary conditions, assuming the fouling thermal resistance of the water-cooled condenser heat transfer tubes. c The calculation process includes the following steps: (1) Calculate the heat transfer characteristic parameters of the condenser under the test conditions. Includes the following steps, 1-a, Calculate the condenser heat load under the test conditions; 1-b, Calculate the overall heat transfer coefficient of the condenser under the test conditions; 1-c, Calculate the heat transfer resistance of the pipe wall under the test conditions; 1-d, calculate the tube-side heat transfer thermal resistance under the test conditions; 1-e, the pipe-side fouling thermal resistance under the test conditions is calculated using an assumed value; 1-f, Calculate the shell-side thermal resistance under the test conditions; (2) Calculate the heat transfer characteristic parameters of the condenser corrected to the design operating condition boundary conditions. Includes the following steps, 2-a, Calculate the heat transfer resistance of the pipe wall under the design conditions; 2-b, Calculate the tube-side heat transfer thermal resistance under design conditions; 2-c, Calculate the pipe-side fouling thermal resistance under design conditions; 2-d, calculate the shell-side thermal resistance corrected to the design conditions; 2-e, corrected to the overall heat transfer coefficient under design conditions; (3) Calculate the condenser pressure corrected to the design operating condition boundary conditions, including the following steps. 3-a. Obtain the number of heat exchange units (NTUs) corrected to the design boundary conditions. tc ; 3-b. Obtain the condenser pressure p corrected to the design operating condition boundary conditions. c .

5. The method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser according to claim 4, characterized in that, In section 1-a, the formula for calculating the condenser heat load is: Q T =G wT ·C P ·(t 2T -t 1T ) / 3.6 In the formula: Q T The condenser operating heat load, W; t 2T The outlet temperature of the condenser circulating water is expressed in °C (t). 1T The inlet water temperature of the condenser circulating water is expressed in °C (G). wT The circulating water flow rate is kg / h; C P The specific heat capacity of the circulating water is 4.186 kJ / (kg·℃). In section 1-b, the formula for calculating the overall heat transfer coefficient of the condenser is: In the formula, U t The overall heat transfer coefficient of the condenser is W / (m²). 2 .℃); A is the condenser area, m 2 LMTD is the logarithmic mean temperature difference, in °C. The logarithmic mean temperature difference is calculated using the following formula: In the formula: t sT is the saturation temperature corresponding to the condenser pressure, in °C; In 1-c, the formula for calculating the heat transfer resistance of the pipe wall is: In the formula, D o With D i These are the outer and inner diameters of the heat exchanger tubes, in meters (m); R m The heat transfer resistance of the pipe wall is expressed in m².K / W; k m The thermal conductivity of the heat exchanger tube is expressed in W / mK. In step 1-d, the formula for calculating the tube-side thermal resistance is: in, In the formula, R t The tube-side thermal resistance is given by: Pr (Plaints number), Re (Reynolds number), k (thermal conductivity of the medium, W / mK), μ (dynamic viscosity of the medium, Pa·s), and ρ (density of the medium, kg / m³). 3 v is the flow velocity of the medium in the tube, in m / s; N is the number of heat exchange tubes in the condenser; n is the number of shell-side tubes in the condenser; when calculating the thermal conductivity, dynamic viscosity and density of the medium, the characteristic temperature of the medium is taken as the average temperature of the condenser circulating water inlet and outlet under the test conditions. In 1-e, R f =R fg ; In the formula, R f For the tube-side fouling thermal resistance under test conditions; R fg The assumed thermal resistance value of fouling on a certain pipe side under test conditions; In 1-f, the thermal resistance R of the shell side is... s The calculation formula is: 。 6. The method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser according to claim 4, characterized in that, 2-a, the calculation formula is: R md =R m In the formula, R md The heat transfer resistance of the pipe wall under design conditions; 2-b, the calculation formula is: in, In the formula, R td The design tube-side thermal resistance is expressed in m².K / W; Prd is the design Prandtl number; Red is the design Reynolds number; k d Thermal conductivity of the medium under design conditions, in W / mK; μ d The dynamic viscosity of the medium under design operating conditions is expressed in Pa·s; ρ d The density of the medium under design conditions, in kg / m³ 3 ;v d The flow velocity in the pipe under design conditions is given in m / s. When calculating the thermal conductivity, dynamic viscosity, and density of the medium, the characteristic temperature of the medium is taken as the average temperature of the condenser circulating water inlet and outlet under design conditions. The calculation process for 2-c includes the following steps: i) Calculate the overall heat transfer coefficient under design conditions The overall heat transfer coefficient of the condenser under design conditions is calculated using the following formula: The logarithmic mean temperature difference under design conditions is calculated using the following formula: In the formula, the parameters marked with the subscript "d" all correspond to the parameters under the design conditions; ii) Calculate the fouling factor on the heat exchanger tube side under design conditions: In the formula, R fd β is the fouling factor of the heat exchanger tube under design conditions, in m2.K / W. cd This is the design value for the pipe cleanliness coefficient under the design operating conditions; The formula for calculating 2-d is: In the formula, R sd The shell-side thermal resistance under design conditions, in meters (m). 2 .K / W; μ s The dynamic viscosity of the shell-side liquid medium under test conditions is expressed in Pa·s and kJ / kJ. s The thermal conductivity of the shell-side liquid medium under test conditions is expressed in W / mK; ρ s Density of the shell-side liquid medium under test conditions, in kg / m³ 3 Parameters marked with the subscript "d" correspond to parameters under design conditions. When solving for the physical properties of the medium under experimental conditions, the shell-side liquid film temperature t is used. f =t sT Calculated using -0.2×LMTD; when solving for the physical property parameters of the medium under design conditions, the shell-side medium liquid film temperature t is used. fs =t sd -0.2×LMTD d calculate; The formula for calculating 2-e is: In the formula, U tc To correct for the overall heat transfer coefficient under design conditions, the unit is W / (m²). 2 .℃).

7. The method for calculating the fouling thermal resistance of heat transfer tubes in a water-cooled condenser according to claim 6, characterized in that, The formula for calculating 3-a is: Number of heat exchange units (NTU) tc The calculation formula is In the formula, G wd The circulating water flow rate under design conditions is expressed in kg / h; C Pd The specific heat capacity of the circulating water under design conditions. kJ / (kg·℃), take 4.186 kJ / (kg·℃); 3-b condenser pressure p c1 The calculation formula is p sc =f(t sc ) p c =p sc In the formula, t sc To correct for the condenser saturation temperature under design conditions, ℃; t 1d t 2d These are the condenser circulating water inlet and outlet temperatures under design conditions, in °C; formula p sc =f(t) sc ).

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