Condenser heat exchange performance monitoring method

Abstract

The invention discloses a condenser heat exchange performance monitoring method, which belongs to the technical field of condensers, and comprises the following steps: S1, performing statistics on condenser performance test and circulating water pump power consumption, and calculating a relation curve of condenser four-layer heat transfer resistance, circulating water pump power consumption and circulating water flow; s2, through the unit heat rate and variable back pressure thermal test, obtaining a change function of the unit heat rate random group load and a correction curve of the back pressure to the heat rate; and S3, a cold end optimization operation calculation process is given based on the online operation data, remote control of a main control room is achieved, and the heat transfer performance of the condenser is monitored in real time. According to the method for monitoring the heat exchange performance of the condenser, online monitoring and monitoring of the heat exchange performance of the condenser are achieved, corresponding real-time data are provided for follow-up cleaning treatment of the condenser, and therefore the operation efficiency of the condenser is improved, and the cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of condensers, and in particular relates to a method for monitoring heat exchange performance of a condenser. Background Art

[0002] The condenser is an important part of a thermal power plant. It is a device that cools the exhaust steam after the steam turbine power plant. The better the heat transfer performance of the condenser, the lower the back pressure of the steam turbine, and the higher the power generation efficiency of the unit.

[0003] Domestic large-scale power station condensers are equipped with various reliable heat exchange equipment cleaning devices. The change process of condenser heat exchange performance is a complex and variable dynamic process, which is formed by many uncertain internal and external factors. Most power plants adopt regular cleaning, which is blind and uneconomical. This is because the operating conditions of power station condensers often change, and the condenser cleaning method formulated according to the design is not applicable. The cleaning is either too frequent or insufficient, resulting in reduced operating economy and safety.

[0004] In view of the above problems, a condenser heat exchange performance monitoring method is developed. Its ultimate goal is to achieve online monitoring and supervision of the condenser heat exchange performance and provide real-time data for cleaning treatment, so as to truly improve the operating efficiency of the condenser. Summary of the invention

[0005] The present invention overcomes the deficiencies of the prior art and provides a method for monitoring the heat exchange performance of a condenser to solve the problems existing in the prior art.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for monitoring the heat exchange performance of a condenser, comprising the following steps:

[0007] S1. Statistic the condenser performance test and circulating water pump power consumption, calculate the heat transfer resistance of the four layers of the condenser, and the relationship curve between the circulating water pump power consumption and the circulating water flow rate;

[0008] S2. Through the unit heat rate and variable back pressure thermal test, the function of the unit heat rate changing with the unit load and the correction curve of back pressure to heat rate were obtained;

[0009] S3. Based on the online operation data, the cold end optimization operation calculation process is given to realize the remote control of the main control room and monitor the condenser heat transfer performance in real time.

[0010] In a preferred embodiment of the present invention, the circulating water pump performs flow calculation, and the calculation formula is:

[0011]

[0012] In the formula

[0013] C——throttling device outflow coefficient under working condition;

[0014] α——Flow coefficient of throttling device under working condition;

[0015] ε——stream expansion coefficient;

[0016] d——diameter of the throttling device opening in the working state, m;

[0017] Δp——Throttling device differential pressure, Pa;

[0018] ρ1——Fluid density under working conditions, kg / m 3 ;

[0019] β - the ratio of the throttle hole diameter to the pipe inner diameter under working conditions.

[0020] In a preferred embodiment of the present invention, the condenser performs heat exchange performance calculation, and the calculation formula is:

[0021]

[0022] In the formula,

[0023] Q + ——condenser heat load;

[0024] ——circulating water inlet and outlet temperatures;

[0025] w + , ——Circulating water flow rate and specific heat capacity;

[0026] Overall heat transfer coefficient

[0027]

[0028] In the formula,

[0029] U + ——overall heat transfer coefficient;

[0030] A o ——heat transfer area of ​​condenser;

[0031] ——logarithmic mean temperature difference;

[0032] ——Saturation temperature corresponding to condenser pressure;

[0033]

[0034] In a preferred embodiment of the present invention, the four-layer heat transfer resistance includes tube wall resistance, tube side resistance, dirt resistance and shell side resistance, and the calculation formulas thereof are:

[0035] Thermal resistance of pipe wall

[0036]

[0037] In the formula,

[0038] d i ,d o ——Inner and outer diameters of heat transfer tubes;

[0039] λ m ——Thermal conductivity of the heat transfer tube;

[0040] Tube side thermal resistance

[0041] The tube side thermal resistance is calculated according to the Rabas-Crane method, see formula (5):

[0042]

[0043] The physical properties of circulating water are determined according to the average water temperature. According to formula (8),

[0044]

[0045] Fouling thermal resistance

[0046] According to the overall heat transfer coefficient of the heat transfer tube and the cleanliness factor (C f Take 0.85), and calculate:

[0047]

[0048] Shell side thermal resistance

[0049]

[0050] In a preferred embodiment of the present invention, when the condenser is in a variable operating condition, the calculation formulas for the tube wall thermal resistance, tube side thermal resistance, fouling thermal resistance and shell side thermal resistance are as follows:

[0051] Tube side thermal resistance under variable working conditions

[0052] The thermal resistance of the pipe wall is a constant, which depends only on the wall thickness and material, so:

[0053]

[0054] Tube side thermal resistance under variable working conditions

[0055] According to the Rabas-Crane method, the tube side thermal resistance under variable working conditions is calculated:

[0056]

[0057] The physical parameters of cooling water are determined according to the average water temperature. According to formula (15),

[0058]

[0059] Fouling thermal resistance under variable conditions

[0060] Take the designed fouling thermal resistance:

[0061]

[0062] Shell side thermal resistance under variable working conditions

[0063]

[0064] In a preferred embodiment of the present invention, the total heat transfer coefficient and condenser pressure of the condenser under variable operating conditions are calculated as follows:

[0065] Condenser heat load Q + / Q * replace The physical property parameters are obtained according to the average temperature of the condensed liquid film, and the average temperature is approximately calculated by equations (18) and (19):

[0066]

[0067] Overall heat transfer coefficient under variable conditions

[0068]

[0069] Condenser pressure under variable operating conditions

[0070]

[0071] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0072] The condenser heat exchange performance monitoring method of the present invention realizes online monitoring and supervision of the condenser heat exchange performance, and provides corresponding real-time data for subsequent condenser cleaning treatment, thereby improving the operating efficiency of the condenser and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0074] Figure 1A flowchart of a preferred embodiment of the present invention;

[0075] Figure 2 It is a general curve of the influence of typical exhaust pressure on the heat consumption of the unit in the preferred embodiment of the present invention;

[0076] Figure 3 A general curve showing the relationship between typical circulating water flow and circulating water pump input power in a preferred embodiment of the present invention; DETAILED DESCRIPTION

[0077] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0078] This embodiment provides a method for monitoring the heat exchange performance of a condenser, which realizes online monitoring and supervision of the heat exchange performance of the condenser, and provides corresponding real-time data for subsequent condenser cleaning treatment, thereby improving the operating efficiency of the condenser and saving costs.

[0079] Combination Figures 1 to 3 As shown, the condenser heat exchange performance monitoring method of this embodiment includes the following steps:

[0080] S1. Statistic the condenser performance test and circulating water pump power consumption, calculate the heat transfer resistance of the four layers of the condenser, and the relationship curve between the circulating water pump power consumption and the circulating water flow rate;

[0081] S2. Through the unit heat rate and variable back pressure thermal test, the function of the unit heat rate changing with the unit load and the correction curve of back pressure to heat rate were obtained;

[0082] S3. Based on the online operation data, the cold end optimization operation calculation process is given to realize the remote control of the main control room and monitor the condenser heat transfer performance in real time.

[0083] When calculating the flow rate of the circulating water pump, the calculation formula is:

[0084]

[0085] In the formula

[0086] C——throttling device outflow coefficient under working condition;

[0087] α——Flow coefficient of throttling device under working condition;

[0088] ε——stream expansion coefficient;

[0089] d——diameter of the throttling device opening in the working state, m;

[0090] Δp——Throttling device differential pressure, Pa;

[0091] ρ1——Fluid density under working conditions, kg / m 3 ;

[0092] β - the ratio of the throttle hole diameter to the pipe inner diameter under working conditions.

[0093] When calculating the heat transfer performance of the condenser, the calculation formula is:

[0094]

[0095] In the formula,

[0096] Q + ——condenser heat load;

[0097] ——circulating water inlet and outlet temperatures;

[0098] w + , ——Circulating water flow rate and specific heat capacity;

[0099] Overall heat transfer coefficient

[0100]

[0101] In the formula,

[0102] U + ——overall heat transfer coefficient;

[0103] A o ——heat transfer area of ​​condenser;

[0104] ——logarithmic mean temperature difference;

[0105] ——Saturation temperature corresponding to condenser pressure;

[0106]

[0107] In this embodiment, the four-layer heat transfer resistance includes the tube wall resistance, the tube side resistance, the dirt resistance and the shell side resistance, and the calculation formulas thereof are:

[0108] Thermal resistance of pipe wall

[0109]

[0110] In the formula,

[0111] d i ,d o ——Inner and outer diameters of heat transfer tubes;

[0112] λ m ——Thermal conductivity of the heat transfer tube;

[0113] Tube side thermal resistance

[0114] The tube side thermal resistance is calculated according to the Rabas-Crane method, see formula (5):

[0115]

[0116] The physical properties of circulating water are determined according to the average water temperature. According to formula (8),

[0117]

[0118] Fouling thermal resistance

[0119] According to the overall heat transfer coefficient of the heat transfer tube and the cleanliness factor (C f Take 0.85), and calculate:

[0120]

[0121] Shell side thermal resistance

[0122]

[0123] Furthermore, when the condenser is in variable operating conditions, the calculation formulas for the tube wall thermal resistance, tube side thermal resistance, fouling thermal resistance, and shell side thermal resistance are as follows:

[0124] Tube side thermal resistance under variable working conditions

[0125] The thermal resistance of the pipe wall is a constant, which depends only on the wall thickness and material, so:

[0126]

[0127] Tube side thermal resistance under variable working conditions

[0128] According to the Rabas-Crane method, the tube side thermal resistance under variable working conditions is calculated:

[0129]

[0130] The physical parameters of cooling water are determined according to the average water temperature. According to formula (15),

[0131]

[0132] Fouling thermal resistance under variable conditions

[0133] Take the designed fouling thermal resistance:

[0134]

[0135] Shell side thermal resistance under variable working conditions

[0136]

[0137] In this embodiment, the total heat transfer coefficient and condenser pressure of the condenser under variable operating conditions are calculated as follows:

[0138] Condenser heat load Q + / Q * replace The physical property parameters are obtained according to the average temperature of the condensed liquid film, and the average temperature is approximately calculated by equations (18) and (19):

[0139]

[0140] Overall heat transfer coefficient under variable conditions

[0141]

[0142] Condenser pressure under variable operating conditions

[0143]

[0144] Through online operation data, the condenser heat load, circulating water flow rate and circulating water temperature are changed according to the unit load conditions, and the condenser performance data under different operating boundary conditions are measured. The total thermal resistance and the tube side thermal resistance, tube wall thermal resistance, and dirt thermal resistance are calculated to obtain the shell side thermal resistance. Then the shell side thermal resistance under each test condition is corrected to the design conditions (such as heat load, circulating water flow rate and inlet water temperature) to obtain the average shell side thermal resistance under the design conditions. The average thermal resistance of the four layers under the design conditions is as follows:

[0145] Four-layer thermal resistance data under condenser design conditions

[0146]

[0147] According to the shell-side thermal resistance under the design conditions, the shell-side thermal resistance under the target working condition is calculated; then the tube-side thermal resistance under the target working condition is obtained, and the total thermal resistance under the current working condition is obtained by adding the tube wall thermal resistance and the dirt thermal resistance, and the reciprocal of the total thermal resistance is the overall heat transfer coefficient.

[0148] In summary, the condenser heat exchange performance monitoring method of this embodiment solves the objective function condenser heat exchange performance, this parameter monitors the condenser heat exchange performance in real time, guides the condenser cleaning device, calculates the heat exchange performance deterioration time and cleaning time, thereby solving the key problems of "when to clean" and "how long to clean" in the condenser heat exchange equipment cleaning process strategy. From the perspective of economic and social benefits, the current periodic scheduled cleaning is changed to cleaning according to the degree of deterioration of the condenser heat exchange performance. "Cleaning on demand" is an inevitable trend of technological development.

[0149] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for monitoring heat exchange performance of a condenser, characterized in that: The following steps are involved: S1. Statistic the condenser performance test and circulating water pump power consumption, calculate the heat transfer resistance of the four layers of the condenser, and the relationship curve between the circulating water pump power consumption and the circulating water flow rate; S2. Through the unit heat rate and variable back pressure thermal test, the function of the unit heat rate changing with the unit load and the correction curve of back pressure to heat rate were obtained; S3. Based on the online operation data, the cold end optimization operation calculation process is given to realize the remote control of the main control room and monitor the condenser heat transfer performance in real time.

2. A condenser heat exchange performance monitoring method according to claim 1, characterized in that: The circulating water pump performs flow calculation, and the calculation formula is: In the formula C——throttling device outflow coefficient under working condition; α——Flow coefficient of throttling device under working condition; ε——stream expansion coefficient; d——diameter of the throttling device opening in the working state, m; Δp——Throttling device differential pressure, Pa; ρ1——Fluid density under working conditions, kg / m 3 ; β - the ratio of the throttle hole diameter to the pipe inner diameter under working conditions.

3. A condenser heat exchange performance monitoring method according to claim 1, characterized in that: The heat exchange performance of the condenser is calculated by the following formula: In the formula, Q + ——condenser heat load; ——circulating water inlet and outlet temperatures; w + , ——Circulating water flow rate and specific heat capacity; Overall heat transfer coefficient In the formula, U + ——overall heat transfer coefficient; A o ——heat transfer area of ​​condenser; ——logarithmic mean temperature difference; ——Saturation temperature corresponding to condenser pressure; 4. A condenser heat exchange performance monitoring method according to claim 1, characterized in that: The four-layer heat transfer resistance includes tube wall resistance, tube side resistance, dirt resistance and shell side resistance, and the calculation formulas are: Thermal resistance of pipe wall In the formula, d i ,d o ——Inner and outer diameters of heat transfer tubes; λ m ——Thermal conductivity of the heat transfer tube; Tube side thermal resistance The tube side thermal resistance is calculated according to the Rabas-Crane method, see formula (5): The physical properties of circulating water are determined according to the average water temperature. According to formula (8), Fouling thermal resistance According to the overall heat transfer coefficient of the heat transfer tube and the cleanliness factor (C f Take 0.85), and calculate: Shell side thermal resistance 5. A condenser heat exchange performance monitoring method according to claim 4, characterized in that: When the condenser is in variable operating conditions, the calculation formulas for the tube wall thermal resistance, tube side thermal resistance, fouling thermal resistance and shell side thermal resistance are as follows: Tube side thermal resistance under variable working conditions The thermal resistance of the pipe wall is a constant, which depends only on the wall thickness and material, so: R m * =R m + (11) Tube side thermal resistance under variable working conditions According to the Rabas-Crane method, the tube side thermal resistance under variable working conditions is calculated: The physical parameters of cooling water are determined according to the average water temperature. According to formula (15), Fouling thermal resistance under variable conditions Take the design fouling thermal resistance: Shell side thermal resistance under variable working conditions 6. A condenser heat exchange performance monitoring method according to claim 5, characterized in that: The total heat transfer coefficient and condenser pressure of the condenser under variable working conditions are calculated as follows: Condenser heat load Q + / Q * replace The physical property parameters are obtained according to the average temperature of the condensed liquid film, and the average temperature is approximately calculated by equations (18) and (19): Overall heat transfer coefficient under variable conditions Condenser pressure under variable operating conditions

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