Method for correcting heat transfer coefficient of seawater heat exchanger

Abstract

The invention belongs to the technical field of heat exchanger heat transfer coefficient monitoring, particularly relates to a seawater heat exchanger heat transfer coefficient correction method, and provides two heat transfer coefficient correction methods: a standard data correction method establishes working condition spectrums of a seawater heat exchanger in a clean state under different seawater conditions, and determines standard heat transfer coefficients of the seawater heat exchanger under different working conditions; the heat transfer coefficient of the seawater heat exchanger is corrected according to the working condition spectrum and the standard heat transfer coefficient, the method is suitable for the seawater heat exchangers which are produced in a large scale, have fixed specifications and are applied to different sea areas, and after a database is built, the heat transfer coefficients, measured under different working conditions, of the seawater heat exchangers with the same specifications can be corrected. The heat exchange amount correction method is suitable for heat exchangers which are applied in a small scale, customized and applied in a single sea area, early-stage preparation is not needed, the principle is visual, operation is easy and convenient, only the relation between data and the heat transfer coefficient needs to be established, and errors introduced in the correction process are avoided.

Description

Technical field:

[0001] The present invention belongs to the technical field of heat transfer coefficient monitoring of heat exchangers, and specifically relates to a method for correcting the heat transfer coefficient of a seawater heat exchanger, which corrects the heat transfer coefficient of the seawater heat exchanger and eliminates the influence of changes in seawater operating conditions on the heat transfer coefficient of the heat exchanger. Background technology:

[0002] Seawater is an ideal cooling fluid for heat exchangers in thermal power, nuclear power, and ships due to its large reserves and low cost. However, seawater contains a large amount of Ca 2+ and Mg 2+ When the temperature is high, Ca(OH)2, Mg(OH)2, CaCO3, MgCO3 and other sediments containing calcium and magnesium elements are easily precipitated. At the same time, the seawater also carries a large amount of silt, marine organisms and other dirt. During the operation of the heat exchanger, it is easy to adhere to the tube wall, resulting in a decrease in its heat exchange capacity. The heat exchange capacity is the core capacity of the heat exchanger. Insufficient heat exchange capacity will seriously threaten the normal operation of the entire unit.

[0003] In fact, the contamination process of the heat exchanger is very slow and cannot be directly observed. It is necessary to monitor the operating parameters of the heat exchanger to determine the degree of contamination of the heat exchanger. At present, power plants generally use the following three methods to judge the contamination of heat exchangers:

[0004] (1) By analyzing the end difference (the temperature difference between the cold fluid inlet and the hot fluid outlet), the change of the end difference is related not only to the degree of contamination of the heat exchanger, but also to the flow rate and inlet temperature of the cold fluid, and is greatly affected by the natural environment;

[0005] (2) Judging by the inlet and outlet pressure difference of the cold fluid, however, the inlet and outlet pressure difference of the cold fluid mainly reflects the flow resistance of the cold fluid in the heat exchange tube, which is effective when the heat exchanger pipeline is highly polluted or even blocked; when the heat exchanger pipeline is relatively clean, the inlet and outlet pressure difference of the cold fluid is very small, which cannot effectively reflect the pollution of the heat exchanger;

[0006] (3) Judging by the heat transfer coefficient of the heat exchanger, although the heat transfer coefficient can very intuitively reflect the heat transfer capacity of the heat exchanger, the heat transfer coefficient is also affected by the flow rate of the cold fluid, the inlet temperature and the degree of dirtiness of the pipeline. When the inlet temperature and flow rate of the cold fluid (seawater) fluctuate due to changes in the natural environment, the heat transfer coefficient will also fluctuate, and there will be a certain deviation. The heat transfer coefficient needs to be corrected according to the actual operating conditions.

[0007] Research shows that the heat transfer coefficient can more intuitively reflect the changes in the cleanliness status of the heat exchanger tube, and is a reliable basis for monitoring the changes in the heat transfer coefficient. However, since the seawater heat exchanger uses natural seawater as the cold fluid, its temperature and flow rate will be affected by natural factors such as weather and tides, and the accuracy of the heat transfer coefficient cannot be guaranteed. Therefore, it is necessary to use a suitable method to correct the heat transfer coefficient to eliminate the influence of changes in seawater status on the heat transfer coefficient.

[0008] In the prior art, some people use formulas to correct the heat transfer coefficient under variable working conditions. For example, the Chinese document Wang Jianguo, Wang Yonghua. Online calculation of the cleanliness coefficient of the condenser water side. Steam Turbine Technology, 2012, 54 (06): 455-457 discloses an application method of correcting the heat transfer coefficient of the condenser using the HEI formula of the American Heat Transfer Society; the Chinese document Jiang Ning, Cao Zuqing. Using the standard heat transfer coefficient to evaluate the cleanliness of the water side and steam side of the condenser. Thermal Power Generation, 2001 (02): 43-45+1 discloses a method for determining the correction coefficient when using the HEI formula and the Behrman formula to correct the heat transfer coefficient of the condenser. However, it is applicable to condensers where one side of the hot fluid is hot steam, and is not applicable to heat exchangers where the hot fluid is liquid.

[0009] Some people correct the heat transfer coefficient through the historical data of the heat transfer coefficient. For example, a heat transfer performance evaluation method for a heat exchanger disclosed in Chinese Patent 202110032711.7 includes: obtaining the monitoring parameters of the heat exchanger; calculating according to the monitoring parameters to obtain the actual flow rate flowing through the heat exchanger; obtaining the fouling heat transfer coefficient of the heat exchanger under the test conditions according to the actual flow rate and the monitoring parameters; obtaining the clean heat transfer coefficient of the heat exchanger under the test conditions; correcting based on the fouling heat transfer coefficient and the clean heat transfer coefficient to obtain the corrected heat transfer coefficient of the heat exchanger after correction; evaluating the heat transfer performance of the heat exchanger according to the corrected heat transfer coefficient; and establishing a relationship formula between the heat transfer coefficient and the dynamic viscosity, thermal conductivity, and the flow rates of cold and hot fluids based on the historical data of the heat exchanger in the clean state.

[0010] Others have corrected the heat transfer coefficient by establishing a corresponding relationship between the heat transfer coefficient and the operating parameters. For example, a condenser heat transfer performance attenuation test method disclosed in Chinese Patent 202210025777.8 includes the following steps: S1. Calculate the cooling water temperature difference of the condenser, specifically: △t = t1-t2, where △t is the cooling water temperature difference, t1 is the condenser outlet water temperature, and t2 is the condenser inlet water temperature; S2. Calculate the basic heat transfer coefficient of the condenser, specifically: Vn = Qw / Sn, where Vn is the flow rate in the cooling pipe, and Qw is the cooling water flow rate; Sn = N1*((Dn-2*HD) / 1000 / 2)2*3.14159 / Mb / L c, where Sn is the condenser flow area, N1 is the number of cooling tubes, Dn is the outer diameter of the cooling tube, HD is the wall thickness of the cooling tube, Mb is the back pressure of the cooling tube, and Lc is the number of cooling tube flow paths; S3, calculate the comprehensive heat transfer coefficient of the condenser, specifically: k = k0 * φ * βc * βt * βm, where k0 is the basic heat transfer coefficient, φ is the basic heat transfer coefficient correction factor, βc is the cleanliness coefficient of the condenser cooling tube, which is taken as 0.85, βm is the correction factor for the condenser tube material and tube thickness, and βt is the cooling water inlet temperature correction factor; S4, calculate the end difference of the condenser, specifically: for a single Back-pressure condenser: Where δt is the condenser end difference, Fc is the condenser cooling area, and Cw is the specific heat of water; the cooling water temperature in the cooling tube is the condenser inlet water temperature, and the comprehensive heat transfer coefficient k is calculated according to step 3; for double-pressure condenser: Where δt1 is the condenser end difference 1, k1 is the comprehensive heat transfer coefficient; the cooling water temperature in the cooling tube is the condenser inlet water temperature, and the comprehensive heat transfer coefficient k1 is calculated according to step 3; Where δt2 is the condenser end difference 2, k2 is the comprehensive heat transfer coefficient; the cooling water temperature in the cooling tube is t2+△t / 2, and the comprehensive heat transfer coefficient k2 is calculated according to step 3; for three Double pressure condenser: Wherein, δt1 is the condenser end difference 1, k1 is the comprehensive heat transfer coefficient; the cooling water temperature in the cooling tube is the condenser inlet water temperature, and the comprehensive heat transfer coefficient k1 is calculated according to step 3; Wherein, δt2 is the condenser end difference 2, k2 is the comprehensive heat transfer coefficient; the cooling water temperature in the cooling tube is t2+△t / 3, and the comprehensive heat transfer coefficient k2 is calculated according to step 3; Wherein, δt3 is the condenser end difference 3, k3 is the comprehensive heat transfer coefficient; the cooling water temperature in the cooling tube is t2+2△t / 3, and the comprehensive heat transfer coefficient k3 is calculated according to step 3; S5, calculate the back pressure of the condenser, specifically: T=

[0011] 273.16+ts, where Pn is the saturated steam pressure, T is the temperature, and ts is the condensate temperature; for a single back-pressure condenser, the condensate temperature is ts=t2+△t+δt; for a double back-pressure condenser, the condensate temperature is ts1=t2+△t / 2+δt1, and the condenser back pressure 1Pn1 is obtained. The condensate temperature is ts2=t2+△t+δt2, and the condenser back pressure 2Pn2 is obtained. (Pn1+Pn2) / 2 is taken as the back pressure of the double back-pressure condenser; for a triple back-pressure condenser, the condensate temperature is ts1=t2+△t / 3+δt1, and the condensate back pressure 1Pn1 is obtained. The condensate temperature is ts2=t2+2△t / 3+δt2, and the condensate back pressure 2Pn2 is obtained. The condensate temperature is ts3=

[0012] t2+△t+δt3, get the condenser back pressure 3Pn3, take (Pn1+Pn2+Pn3) / 3 as the back pressure of the three-back-pressure condenser; S6, assuming different basic heat transfer coefficient correction coefficients, different condenser back pressures can be calculated according to steps 1-5, and the relationship curve between the basic heat transfer coefficient correction coefficient and the condenser back pressure can be obtained, and then according to the measured condenser back pressure, the current condenser basic heat transfer correction coefficient can be obtained; S7, according to step 6, continuously obtain the condenser basic heat transfer coefficient correction coefficient at different times, and the attenuation of the condenser heat transfer performance with time can be obtained; it monitors the condenser back pressure, the cold fluid inlet temperature, and the cold fluid flow rate to reverse the heat transfer coefficient, establishes the corresponding relationship between the heat transfer coefficient and the condenser back pressure, the cold fluid inlet temperature, and the cold fluid flow rate, and derives the correction coefficient of each parameter to correct the heat transfer coefficient. Summary of the invention:

[0013] The purpose of the present invention is to overcome the shortcomings of the prior art and to develop a method for correcting the heat transfer coefficient of a seawater heat exchanger so as to eliminate the influence of changes in natural conditions of seawater on the monitoring results of the heat transfer coefficient of the seawater heat exchanger and to more intuitively reflect the changes in the heat transfer capacity of the seawater heat exchanger.

[0014] In order to achieve the above-mentioned purpose, the method for correcting the heat transfer coefficient of a seawater heat exchanger according to the present invention includes a standard data correction method applicable to seawater heat exchangers for large-scale applications and a heat transfer correction method applicable to seawater heat exchangers for small-scale applications and seawater heat exchangers that cannot be corrected by the standard data correction method due to time, cost and other factors; wherein,

[0015] Before the heat exchanger is put into use, the standard data correction method establishes a seawater condition spectrum based on the service conditions of the seawater heat exchanger, conducts test operation on the seawater heat exchanger, tests the standard heat transfer coefficient under different working conditions, and establishes a database to serve the subsequent application of the seawater heat exchanger;

[0016] The heat transfer correction method calculates the existing heat transfer coefficient by fitting and mathematical operation, takes the heat transfer as the reference object for correcting the heat transfer coefficient, and uses the functional relationship between the heat transfer and the heat transfer coefficient as the standard for correcting the heat transfer coefficient.

[0017] The correction process of the standard data correction method involved in the present invention is as follows:

[0018] First, determine the specifications, structure, size and seawater environment spectrum of the seawater heat exchanger during service;

[0019] Then, according to the normal working conditions of the seawater heat exchanger, the standard working conditions of the seawater heat exchanger are set, and the seawater heat exchanger in a clean state is placed under each standard working condition for 24 hours to obtain the standard heat transfer coefficient of the seawater heat exchanger, and a standard heat transfer coefficient database of the seawater heat exchanger under standard working conditions is established;

[0020] Finally, the heat transfer coefficient of the seawater heat exchanger is corrected according to the standard heat transfer coefficient database.

[0021] The specific correction process includes the following steps:

[0022] (1) Determine the specifications, structure and size of the seawater heat exchanger;

[0023] (2) Determine the normal operating conditions of the seawater heat exchanger during actual operation, including the temperature and flow rate of seawater during operation of the seawater heat exchanger. The highest seawater temperature during operation is recorded as t max , the lowest seawater temperature is t min , the maximum seawater flow is recorded as q max , the minimum seawater flow is denoted as q min ;

[0024] (3) Establish a heat transfer coefficient database for seawater heat exchangers under normal operating conditions. max and t min Set n temperature gradients (2≤n≤10) and name them t1 to t n ;

[0025] In q max and q min Between, set m flow gradients (2≤m≤10), named q1 to q m ; The combination of different temperature gradients and flow gradients is named as the standard operating spectrum;

[0026] The clean seawater heat exchanger was placed in each standard operating condition for stable operation for 24 hours. The heat transfer coefficient in this state was calculated based on the seawater heat exchanger operating parameters collected during this process (the heat transfer coefficient is a range, not a fixed value). The maximum value of the heat transfer coefficient was named K max，(对应温度)，(对应流速) , the minimum value is named Kmin，(对应温度)，(对应流速) , the interval [K max，(对应温度)，(对应流速) , K min，(对应温度)，(对应流速) ] is named as the standard heat transfer coefficient under this standard working condition;

[0027] Establish a database of standard heat transfer coefficients for seawater heat exchangers under standard operating conditions;

[0028] (4) Run the seawater heat exchanger under normal operating conditions for a certain period of time and calculate the corresponding heat transfer coefficient;

[0029] The seawater temperature under normal operating conditions is named t 原始 , the sea water temperature at a certain point in time is named t 原始-(运行时间) ;

[0030] The seawater flow rate under normal working conditions is named q 原始 , the seawater temperature at a certain point in time is named q 原始-(运行时间) ;

[0031] The heat transfer coefficient calculated based on seawater temperature and seawater flow rate is named the original heat transfer coefficient K. 原始 The heat transfer coefficient at a certain time point is named K 原始-(运行时间) ;

[0032] (5) Set t 原始 and q 原始 Compare with the standard operating condition spectrum established in step (3) to classify the actual operating conditions of the seawater heat exchanger;

[0033] (6) For each K 原始-(运行时间) , when K max，(对应温度)，(对应流速) ≤K 原始 ≤K min，(对应温度)，(对应流速) When the heat transfer coefficient is [K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2;

[0034] When K 原始 ≤K min，(对应温度)，(对应流速) When the heat transfer coefficient is K min，(对应温度)，(对应流速) -K 原始 +[K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2;

[0035] When K max，(对应温度)，(对应流速) ≤K 原始 When the heat transfer coefficient is K 原始 -K max，(对应温度)，(对应流速) +[K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2;

[0036] (7) The heat transfer coefficients corrected one by one in step (6) are integrated to obtain the heat transfer coefficient corrected by the standard data correction method, denoted as K 标准修正 .

[0037] The correction process of the heat exchange correction method involved in the present invention is as follows:

[0038] First, the seawater heat exchanger is operated under normal conditions, the operating data of the seawater heat exchanger (temperature, flow rate, etc.) is collected, and the heat transfer coefficient and heat transfer capacity of the seawater heat exchanger are calculated;

[0039] Then, the functional relationship between the heat transfer coefficient and the heat exchange amount is established and fitted;

[0040] Finally, a standard heat transfer rate is selected, and the heat transfer coefficient is corrected based on the functional relationship between the heat transfer coefficient and the heat transfer rate.

[0041] The specific process of the heat exchange correction method includes the following steps:

[0042] (1) The seawater heat exchanger is placed in normal operating conditions and operated for a certain period of time, and the corresponding heat transfer coefficient is calculated and named the actual heat transfer coefficient K 原始 The heat transfer coefficient at a certain time point is named K 原始-(运行时间) ;

[0043] (2) Calculate the heat transfer per unit time during the operation of the seawater heat exchanger, denoted as Q 原始 , the heat transfer coefficient at a certain point in time is named Q 原始-(运行时间) ;

[0044] The heat absorbed by seawater is used as the overall heat transfer of the seawater heat exchanger, and the calculation formula is: Q 原始 =c n q n ρ n (t 入口 -t 出口 ), where Q 原始 is the heat transfer capacity of the seawater heat exchanger per unit time, in W, c n is the specific heat of seawater, in J / (kg·k), q n is the seawater flow rate, in m 3 / s,ρ n is the density of seawater, in kg / m 3 , t 入口 and t 出口 are the inlet and outlet temperatures of seawater, respectively, in K;

[0045] (3) Establish K 原始-(运行时间) With Q 原始-(运行时间) The linear function relationship of K is fitted by the least square method: 原始-(运行时间)=a Q 原始-(运行时间) +b;

[0046] (4) Q of the seawater heat exchanger 实际 The maximum value in is recorded as Q max , the minimum value is recorded as Q min , will (Q max +Q min ) / 2 as the correction standard, denoted as Q 标准 ;

[0047] (5) Q 标准 and Q 原始 With K 原始 The functional relationship of K 原始 Make corrections, the correction formula is:

[0048] (6) The heat transfer coefficients corrected one by one in step (5) are integrated to obtain the heat transfer coefficient corrected by the standard data correction method, denoted as K 换热量修正 ;

[0049] According to the principle of heat transfer, the basic calculation formula of heat transfer coefficient is: Where K is the heat transfer coefficient of the heat exchanger, in W / (m 2 ·k); Q is the heat exchange capacity of the heat exchanger per unit time, in W, and A is the heat exchange area, in m 2 , Δt is the logarithmic mean temperature difference, the unit is k; it shows that the heat transfer coefficient K of the heat exchanger is affected by the heat transfer amount Q, the heat exchange area A and the logarithmic mean temperature difference Δt, among which the heat exchange area A is a constant and will not affect the heat transfer coefficient K. The heat transfer amount and the logarithmic mean temperature difference are both affected by the changes in natural seawater temperature, flow rate and other parameters. The logarithmic mean temperature difference participates in the calculation in the form of 1 / Δt, and its disturbance has a relatively small effect on the calculation result of the heat transfer coefficient K. In contrast, the change in the heat transfer amount Q has the most significant effect on the calculation result of the heat transfer coefficient.

[0050] Compared with the prior art, the present invention provides two heat transfer coefficient correction methods with strong feasibility and different applicable scopes. The standard data correction method establishes the operating spectrum of the clean seawater heat exchanger under different seawater conditions, determines the standard heat transfer coefficient of the seawater heat exchanger under different operating conditions, and corrects the heat transfer coefficient of the seawater heat exchanger according to the operating spectrum and the standard heat transfer coefficient. The method is suitable for seawater heat exchangers produced in large quantities, with fixed specifications, and used in different sea areas. After completing the database construction, the heat transfer coefficients measured under different operating conditions for seawater heat exchangers of the same specifications can be corrected. The correction process is simple and intuitive, the correction result is highly accurate, and no other errors are introduced. The heat transfer correction method is suitable for small-scale, customized heat exchangers used in a single sea area. No preliminary preparation is required, the principle is intuitive, and the operation is simple. Only a relationship between data and the heat transfer coefficient needs to be established, thereby avoiding errors introduced in the correction process. The method can effectively eliminate the influence of fluctuations in natural seawater conditions on the heat transfer coefficient of the seawater heat exchanger, and improve the monitoring accuracy of the heat transfer coefficient. The applicable scopes of the two correction methods do not overlap with each other, and can cover different application scenarios of seawater heat exchangers. Description of the drawings:

[0051] Figure 1 It is a schematic diagram of the uncorrected heat transfer coefficient of the seawater heat exchanger involved in Examples 1 and 2 of the present invention when it runs for 20 days.

[0052] Figure 2 This is a schematic diagram of the seawater inlet temperature value when the seawater heat exchanger involved in Examples 1 and 2 of the present invention is operated for 20 days.

[0053] Figure 3 This is a schematic diagram of the seawater flow rate value when the seawater heat exchanger involved in Examples 1 and 2 of the present invention is operated for 20 days.

[0054] Figure 4 Schematic diagram of heat transfer coefficient values ​​after correction of standard data involved in Example 1 of the present invention.

[0055] Figure 5 It is a schematic diagram of the functional relationship between the heat transfer coefficient K original and the heat exchange amount per unit time Q original involved in Example 2 of the present invention.

[0056] Figure 6 It is a schematic diagram of the heat transfer coefficient values ​​before and after the heat exchange amount correction involved in Example 2 of the present invention. Specific implementation method:

[0057] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0058] Embodiment 1:

[0059] The method for correcting the heat transfer coefficient of a seawater heat exchanger involved in this embodiment uses a standard data correction method to correct the heat transfer coefficient of a seawater heat exchanger that has been running for 20 days;

[0060] The heat transfer coefficient of the seawater heat exchanger is Figure 1 As shown in Figure 2, obvious fluctuations occur in a short period of time; the seawater temperature during the operation of the seawater heat exchanger is as follows: Figure 2 As shown, the seawater flow rate is Figure 3 As shown, the temperature and flow of seawater are affected by weather and tides, and show obvious periodic changes;

[0061] The specific correction process includes the following steps:

[0062] (1) Determine the specifications, structure and size of the seawater heat exchanger;

[0063] (2) Determine the normal operating conditions of the seawater heat exchanger during actual operation, and the maximum seawater temperature during operation t max The lowest seawater temperature is 28.5℃. min is 26.4℃, the maximum seawater flow rate q max 0.24m 3 / h, minimum seawater flow rate q min 0.19m 3 / h;

[0064] (3) Establish a heat transfer coefficient database for seawater heat exchangers under normal operating conditions. max and t min Two temperature gradients were set, namely (26.4°C, 27.5°C] and (27.5°C, 28.5°C], named t1 and t2 respectively;

[0065] In q max and q min Two flow gradients are set, namely (0.19m 3 / h, 0.21m 3 / h] and (0.21m 3 / h, 0.24m 3 / h], named q1 and q2 respectively;

[0066] Combine 2 temperature gradients and 2 flow gradients into standard working conditions;

[0067] The clean seawater heat exchanger is placed in each standard operating condition and operated stably for 24 hours. The heat transfer coefficient of this state is calculated based on the operating parameters of the seawater heat exchanger collected during this process, and a standard heat transfer coefficient database of the seawater heat exchanger under this operating condition is established. The standard operating conditions and corresponding standard heat transfer coefficients are shown in Table 1:

[0068]

[0069] (4) The seawater heat exchanger is placed under normal operating conditions and operated for a certain period of time. The corresponding heat transfer coefficient is calculated and the seawater temperature under normal operating conditions is named t 原始 , the seawater flow is named q 原始 The heat transfer coefficient calculated based on seawater temperature, seawater flow rate and other parameters is named the original heat transfer coefficient K 原始 , the results are shown in Table 2;

[0070] (5) Set t 原始 and q 原始 By comparing with the standard operating conditions established in step (3), the actual operating conditions of the seawater heat exchanger are classified. The results are shown in Table 2:

[0071]

[0072]

[0073]

[0074] (6) For each K 原始-(运行时间) , when K max，(对应温度)，(对应流速) ≤K 原始 ≤K min，(对应温度)，(对应流速) When the heat transfer coefficient is [K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2;

[0076] When K 原始 ≤K min，(对应温度)，(对应流速) When the heat transfer coefficient is K min，(对应温度)，(对应流速) -K 原始 +[K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2;

[0077] When K max，(对应温度)，(对应流速) ≤K 原始 When the heat transfer coefficient is K 原始 -K max，(对应温度)，(对应流速) +[K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2, the correction results are shown in Table 3:

[0078]

[0079]

[0080]

[0081] (7) Integrate the heat transfer coefficients corrected one by one in step (6), and the heat transfer coefficient obtained is the heat transfer coefficient K corrected by the standard data correction method 标准修正 , the results are as follows Figure 4 shown.

[0082] Embodiment 2:

[0083] The method for correcting the heat transfer coefficient of a seawater heat exchanger involved in this embodiment uses a standard data correction method to correct the heat transfer coefficient of a seawater heat exchanger that has been running for 20 days;

[0084] The heat transfer coefficient of the seawater heat exchanger is Figure 1 As shown in Figure 2, obvious fluctuations occur in a short period of time; the seawater temperature during the operation of the seawater heat exchanger is as follows: Figure 2 As shown, the seawater flow rate is Figure 3 As shown, the temperature and flow of seawater are affected by weather and tides, and show obvious periodic changes;

[0085] The specific correction process includes the following steps:

[0086] (1) The seawater heat exchanger was placed in normal operating conditions and operated continuously for 20 days. The corresponding heat transfer coefficient was calculated and named the actual heat transfer coefficient K 原始 , the results are shown in Table 4;

[0087] (2) Calculate the heat transfer rate Q per unit time during the operation of the seawater heat exchanger 原始 , the results are shown in Table 4:

[0088]

[0089]

[0090] (3) Establish K 原始-(运行时间) With Q 原始-(运行时间) The linear function relationship of is fitted by the least square method, and the fitted function relationship is:

[0091] K 原始-(运行时间) =0.1979Q 原始-(运行时间) -89.322

[0092] K 原始-(运行时间) With Q 原始-(运行时间) The functional relationship and fitting results are as follows Figure 5 As shown, there is an obvious linear relationship between K and Q, and the fitting results can effectively reflect the functional relationship between the two;

[0093] (4) During the operation of the seawater heat exchanger, Q 实际 The maximum value Q max 3300.50W, minimum Q min is 2394.06W, Q max With Q min The average value of 2847.28W is used as the correction standard, recorded as Q 标准 ;

[0094] (5) Q 标准 and Q 原始 With K 原始 The functional relationship of K 原始 Correction is performed and the correction result is recorded as K 换热量修正 , the correction formula is:

[0095]

[0096] Corrected K 换热量修正 The data are shown in Table 5:

[0097]

[0098]

[0099]

[0100] The heat transfer coefficient before and after the heat transfer correction method is as follows: Figure 6 shown.

Claims

1. A method for correcting the heat transfer coefficient of a seawater heat exchanger, characterized in that: It includes a standard data correction method for seawater heat exchangers used in large-scale applications and a heat transfer correction method for seawater heat exchangers used in small-scale applications and seawater heat exchangers that cannot be corrected using the standard data correction method.

2. A method for correcting heat transfer coefficient of a seawater heat exchanger according to claim 1, characterized in that: The standard data correction method is to establish a seawater condition operating spectrum based on the service conditions of the seawater heat exchanger, conduct test operation on the seawater heat exchanger, test the standard heat transfer coefficient under different operating conditions, and establish a database.

3. A method for correcting heat transfer coefficient of a seawater heat exchanger according to claim 1, characterized in that: The heat transfer correction method calculates the existing heat transfer coefficient by fitting and mathematical operation, takes the heat transfer as the reference object for correcting the heat transfer coefficient, and uses the functional relationship between the heat transfer and the heat transfer coefficient as the standard for correcting the heat transfer coefficient.

4. A method for correcting the heat transfer coefficient of a seawater heat exchanger according to claim 1 or 2, characterized in that: The correction process of the standard data correction method is: First, determine the specifications, structure, size and seawater environment spectrum of the seawater heat exchanger during service; Then, according to the normal working conditions of the seawater heat exchanger, the standard working conditions of the seawater heat exchanger are set, and the seawater heat exchanger in a clean state is placed under each standard working condition for 24 hours to obtain the standard heat transfer coefficient of the seawater heat exchanger, and a standard heat transfer coefficient database of the seawater heat exchanger under standard working conditions is established; Finally, the heat transfer coefficient of the seawater heat exchanger is corrected according to the standard heat transfer coefficient database.

5. A method for correcting heat transfer coefficient of a seawater heat exchanger according to claim 1 or 3, characterized in that: The correction process of the heat exchange correction method is: First, the seawater heat exchanger is operated under normal conditions, the operating data of the seawater heat exchanger is collected, and the heat transfer coefficient and heat transfer amount are calculated; Then, the functional relationship between the heat transfer coefficient and the heat exchange amount is established and fitted; Finally, the standard heat transfer rate is selected, and the heat transfer coefficient is corrected based on the functional relationship between the heat transfer coefficient and the heat transfer rate.

6. A method for correcting heat transfer coefficient of a seawater heat exchanger according to claim 4, characterized in that: The specific correction process includes the following steps: (1) Determine the specifications, structure and size of the seawater heat exchanger; (2) Determine the normal operating conditions of the seawater heat exchanger during actual operation, and record the highest seawater temperature during operation as t max , the lowest seawater temperature is t min , the maximum seawater flow is recorded as q max , the minimum seawater flow is denoted as q min ; (3) Establish a heat transfer coefficient database for seawater heat exchangers under normal operating conditions. max and t min n temperature gradients are set, named t1 to t n ; In q max and q min Between, set m flow gradients, named q1 to q m ; The combination of different temperature gradients and flow gradients is named as the standard operating spectrum; The clean seawater heat exchanger was placed in each standard operating condition for stable operation for 24 hours. The heat transfer coefficient under this state was calculated based on the seawater heat exchanger operating parameters collected during this process, and the maximum value of the heat transfer coefficient was named K. max，(对应温度)，(对应流速) , the minimum value is named K min，(对应温度)，(对应流速) , the interval [K max，(对应温度)，(对应流速) , K min，(对应温度)，(对应流速) ] is named as the standard heat transfer coefficient under this standard working condition; Establish a database of standard heat transfer coefficients for seawater heat exchangers under standard operating conditions; (4) Run the seawater heat exchanger under normal operating conditions for a certain period of time and calculate the corresponding heat transfer coefficient; The seawater temperature under normal operating conditions is named t 原始 , the sea water temperature at a certain point in time is named t 原始-(运行时间) ; The seawater flow rate under normal working conditions is named q 原始 , the sea water temperature at a certain point in time is named q 原始-(运行时间) ; The heat transfer coefficient calculated based on seawater temperature and seawater flow rate is named the original heat transfer coefficient K. 原始 The heat transfer coefficient at a certain time point is named K 原始-(运行时间) ; (5) Set t 原始 and q 原始 Compare with the standard operating condition spectrum established in step (3) to classify the actual operating conditions of the seawater heat exchanger; (6) For each K 原始-(运行时间) , when K max，(对应温度)，(对应流速) ≤K 原始 ≤K min，(对应温度)，(对应流速) When the heat transfer coefficient is [K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2; When K 原始 ≤K min，(对应温度)，(对应流速) When the heat transfer coefficient is K min，(对应温度)，(对应流速) -K 原始 +[K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2; When K max，(对应温度)，(对应流速) ≤K 原始 When the heat transfer coefficient is K 原始 -K max，(对应温度)，(对应流速) +[K max，(对应温度)，(对应流速) +K min，(对应温度)，(对应流速) ] / 2; (7) The heat transfer coefficients corrected one by one in step (6) are integrated to obtain the heat transfer coefficient corrected by the standard data correction method, denoted as K 标准修正 .

7. A method for correcting heat transfer coefficient of a seawater heat exchanger according to claim 5, characterized in that: The specific process of the heat exchange correction method includes the following steps: (1) The seawater heat exchanger is placed in normal operating conditions and operated for a certain period of time, and the corresponding heat transfer coefficient is calculated and named the actual heat transfer coefficient K 原始 The heat transfer coefficient at a certain time point is named K 原始-(运行时间) ; (2) Calculate the heat transfer per unit time during the operation of the seawater heat exchanger, denoted as Q 原始 , the heat transfer coefficient at a certain point in time is named Q 原始-(运行时间) ; The heat absorbed by seawater is used as the overall heat transfer of the seawater heat exchanger, and the calculation formula is: Q 原始 =c n q n ρ n (t 入口 -t 出口 ), where Q 原始 is the heat transfer capacity of the seawater heat exchanger per unit time, in W, c n is the specific heat of seawater, in J / (kg·k), q n is the seawater flow rate, in m 3 / s,ρ n is the density of seawater, in kg / m 3 , t 入口 and t 出口 are the inlet and outlet temperatures of seawater, respectively, in K; (3) Establish K 原始-(运行时间) With Q 原始-(运行时间) The linear function relationship of K is fitted by the least square method: 原始-(运行时间) =aQ 原始-(运行时间) +b; (4) Q of the seawater heat exchanger 实际 The maximum value in is recorded as Q max , the minimum value is recorded as Q min , (Q max +Q min ) / 2 as the correction standard, denoted as Q 标准 ; (5) Q 标准 and Q 原始 With K 原始 The functional relationship of K 原始 Make corrections, the correction formula is: (6) The heat transfer coefficients corrected one by one in step (5) are integrated to obtain the heat transfer coefficient corrected by the standard data correction method, denoted as K 换热量修正 .

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