A device and method for measuring heat flux density of water-cooled wall heating surface

Abstract

The present invention discloses a device for measuring the heat flux density of a water-cooled wall heating surface and a method for measuring the heat flux density of the water-cooled wall heating surface. The device includes a data acquisition and processing system and at least one pair of thermocouples, including a cold-end thermocouple and a hot-end thermocouple. A protective sleeve is provided outside the thermocouple, and a fixing frame is provided at the end of the protective sleeve, and the fixing frame is fixedly connected to the water-cooled wall heating surface. The protective sleeve and the fixing frame ensure that the positioning error of the cold-end thermocouple and the hot-end thermocouple is no more than 2 mm. The cold-end measuring point and the hot-end measuring point are arranged on the water-cooled wall heating surface at the same height on the back-fire side of the water-cooled wall heating surface to be measured, and the cold-end measuring point is set at the far-fire end of the water-cooled pipe to be measured, and the hot-end measuring point is set at the central axis point of the fin closest to the water-cooled pipe. The temperature value T of the cold-end thermocouple and the hot-end thermocouple is obtained through the data acquisition and processing system. 冷 and T 热 The heat flux density is calculated. The invention has the advantages of convenient point arrangement, low measurement cost and reliable measurement results.

Description

Technical Field

[0001] The invention relates to a device and a method for measuring the heat flux density of a water-cooled wall heating surface, and belongs to the field of thermal engineering testing. Background Art

[0002] In high-temperature equipment, heat flux is an important parameter for whether the equipment is running safely and stably. Heat flux analysis is an important step in the design, maintenance and calibration of high-temperature equipment. Therefore, obtaining accurate heat flux is of great significance to the safe and stable operation of high-temperature equipment. How to improve the accuracy of heat flux measurement is an important issue that needs to be solved.

[0003] At present, the heat flux density test method mainly uses a heat flux meter. The existing heat flux meter mainly uses a technical solution of drilling holes in the heat-conducting components and burying thermocouples. However, in the actual heat flux density test of high-temperature equipment, due to the high temperature, the heat flux meter needs to be equipped with a cooling device, which makes the heat flux meter large in size, high in cost, and complex to install. It also requires the modification of the high-temperature equipment, which greatly limits the use scenarios of high-temperature heat flux meters.

[0004] The intelligentization of modern power plants urgently requires advanced power plant boiler slagging monitoring, namely water-cooled wall heat flux density testing technology, which can meet the requirements of low measurement cost, high prediction accuracy, and easy installation and maintenance. Summary of the invention

[0005] The purpose of the present invention is to provide a device and method for measuring the heat flux density of a water-cooled wall heating surface, by setting measuring points on the back-fire side of the water-cooled wall heating surface to measure the cold end measuring point temperature and the hot end measuring point temperature respectively, and calculate the heat flux density.

[0006] The present invention is achieved through the following technical solutions:

[0007] A device for measuring the heat flux density of a water-cooled wall heating surface can be used for testing the heat flux density of a water-cooled wall heating surface. The water-cooled wall heating surface serves as a furnace wall and includes a plurality of water-cooled tubes and fins connecting adjacent water-cooled tubes. The device includes a data acquisition and processing system and at least one pair of thermocouples. Any pair of thermocouples includes a corresponding cold-end thermocouple and a hot-end thermocouple. The cold-end thermocouple and the hot-end thermocouple are fixedly connected to a cold-end measuring point and a hot-end measuring point of the water-cooled wall heating surface, respectively, and are used to measure the temperature of the cold-end measuring point and the temperature of the hot-end measuring point, respectively. Any thermocouple is provided with a data line connected to the data acquisition and processing system.

[0008] In the above technical solution, a protective sleeve is provided outside the thermocouple, and a fixing frame is provided at the end of the protective sleeve, and the fixing frame is fixedly connected to the heating surface of the water-cooled wall.

[0009] A method for measuring heat flux density of a water-cooled wall heated tube, the method comprising:

[0010] Select the water-cooled wall heating surface to be tested, obtain its characteristic parameters, and calibrate the heat flux coefficient k of the water-cooled wall heating surface to be tested through numerical simulation;

[0011] The cold end measuring point and the hot end measuring point are arranged on the non-fire side of the heated surface of the water-cooled wall to be tested, and the cold end measuring point is set at the far-fire end of the water-cooled tube to be tested, and the hot end measuring point is set at the central axis point of the fin closest to the water-cooled tube;

[0012] The temperature values ​​T of the cold-end thermocouple and the hot-end thermocouple are obtained by a data acquisition and processing system. 冷 and T 热 , and by the formula q=k(T 热 -T 冷 ) is used to calculate the heat flux density of the water-cooled wall heating surface.

[0013] In the above technical solution, the protective sleeve and the fixing frame ensure that the positioning error of the cold-end thermocouple and the hot-end thermocouple is no more than 2 mm.

[0014] In the above technical solution, the cold end measuring point and the hot end measuring point are set at the same horizontal height.

[0015] In the above technical solution, the characteristic parameters of the water-cooled wall heating surface include its wall thickness, water-cooling tube diameter, water-cooling tube and fin structure and fin width.

[0016] In the above technical solution, the numerical simulation calibration method includes:

[0017] According to the geometric structure of the water-cooled tubes and fins on the heating surface of the water-cooled wall, the periodic calculation domain is selected to carry out the two-dimensional heat transfer numerical calculation, and the inner wall of the tube is set to the boundary condition of equal convection heat transfer coefficient. The convection heat transfer coefficient h is calculated according to the following formula:

[0018]

[0019] Wherein, subscript b represents the working fluid temperature of the cross section of the water-cooled wall heating surface, subscript w represents the working fluid temperature of the water-cooled wall heating surface facing the fire side wall; Nu is the Nusselt number, Re is the Reynolds number, Pr is the Prandtl number; ρ is the density, kg / m 3 ; L is the inner diameter of the water-cooled wall tube; k1 is the thermal conductivity of the static working medium, W / m·K;

[0020] Obtain the pipe material of the water-cooled wall heating surface to be tested, and select the thermal conductivity k1 according to the temperature range. Through numerical simulation, the functional relationship between the heat flux coefficient k of the water-cooled wall heating surface to be tested and the heat flux density of the outer wall of the water-cooled pipe is obtained: k = f(q, T 热 ,T 冷);

[0021] By inputting at least five heat flux values ​​and obtaining corresponding at least three sets of temperature values ​​[T 热 ,T 冷 ] is calibrated to obtain the heat flux coefficient k of the water-cooled wall heating surface to be tested.

[0022] The present invention has the following advantages and beneficial effects: by setting measuring points on the back-to-fire side of the water-cooled wall heating surface, the heat flux density is calculated by the working medium temperature in the water-cooled tube and the center temperature of the finned tube, thus avoiding high-temperature measurement, making point arrangement convenient, measuring cost low and measuring results reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the heat flux density measuring device of the water-cooled wall heating surface involved in the present invention.

[0024] In the figure: 1 - water cooling tube; 2 - fin; 3 - cold end thermocouple; 4 - hot end thermocouple; 5 - data acquisition and processing system; 6 - protective sleeve; 7 - fixing bracket. DETAILED DESCRIPTION

[0025] The specific implementation manner and working process of the present invention will be further described below in conjunction with the accompanying drawings.

[0026] The terms such as up, down, left, right, front and back in this application document are based on the positional relationships shown in the drawings. If the drawings are different, the corresponding positional relationships may also change accordingly, so they cannot be understood as limiting the scope of protection.

[0027] like Figure 1 As shown, a water-cooled wall heating surface heat flux density measuring device can be used for water-cooled wall heating surface heat flux density testing, and the water-cooled wall heating surface is usually used as a furnace wall, which includes a plurality of water-cooled tubes 1 and fins 2 connecting adjacent water-cooled tubes. The water-cooled wall with fin water-cooled tube structure is a common water-cooled wall heating surface structure in the art, and those skilled in the art can understand and imagine its detailed structure.

[0028] The device includes a data acquisition and processing system 5 and at least one pair of thermocouples. Any pair of thermocouples includes a cold end thermocouple 3 and a hot end thermocouple 4. The cold end thermocouple 3 and the hot end thermocouple 4 are respectively fixedly connected to the cold end measuring point and the hot end measuring point of the water-cooled wall heating surface, and are used to measure the cold end measuring point temperature and the hot end measuring point temperature respectively. A data line is provided at the end of any thermocouple to connect with the data acquisition and processing system 5, so that the thermocouple temperature data can be collected and stored. A protective sleeve 6 is provided outside any thermocouple, and a fixing frame 7 is provided at the end of the protective sleeve 6. The fixing frame 7 is fixedly connected to the water-cooled wall heating surface by welding or the like. The fixing frame 7 is made of rigid material, such as channel steel, to avoid its deformation as much as possible. Self-locking nuts can be used to connect the protective sleeve 6 and the fixing frame 7. The fixing frame 7 made of rigid material is used to enhance the stability of the protective sleeve 6, thereby reducing the positioning deviation caused by the movement of the thermocouple caused by the vibration during the operation of the boiler. The protective sleeve 6 and the fixing bracket 7 ensure that the positioning error of the cold-end thermocouple 3 and the hot-end thermocouple 4 is no more than 2 mm, thereby ensuring the accuracy of the measurement position.

[0029] The water-cooled wall heating surface to be tested is selected, and characteristic parameters of the water-cooled wall heating surface including its wall thickness, water-cooling tube diameter, water-cooling tube and fin structure, and fin width are obtained. Through numerical simulation, the heat flux coefficient k of the water-cooled wall heating surface to be tested is calibrated.

[0030] The numerical simulation and calibration process includes:

[0031] According to the geometric structure of the water-cooled tubes and fins on the heating surface of the water-cooled wall, the periodic calculation domain is selected to carry out the two-dimensional heat transfer numerical calculation, and the inner wall of the tube is set to the boundary condition of equal convection heat transfer coefficient. The convection heat transfer coefficient h is calculated according to the following formula:

[0032]

[0033] Wherein, subscript b represents the working fluid temperature of the cross section of the water-cooled wall heating surface, subscript w represents the working fluid temperature of the water-cooled wall heating surface facing the fire side wall; Nu is the Nusselt number, Re is the Reynolds number, Pr is the Prandtl number; ρ is the density, kg / m 3 ; L is the inner diameter of the water-cooled wall tube; k1 is the thermal conductivity of the static working medium, W / m·K;

[0034] Obtain the pipe material of the water-cooled wall heating surface to be tested, and select the appropriate thermal conductivity k1 according to the temperature range. Through numerical simulation, the functional relationship between the heat flux coefficient k of the water-cooled wall heating surface to be tested and the heat flux density of the outer wall of the water-cooled pipe is obtained: k = f(q, T 热 ,T 冷 );

[0035] By inputting at least five heat flux values ​​and obtaining corresponding at least three sets of temperature values ​​[T 热,T 冷 ] is calibrated to obtain the heat flux coefficient k of the water-cooled wall heating surface to be tested.

[0036] The cold end measuring point and the hot end measuring point are arranged on the back-fire side of the heated surface of the water-cooled wall to be tested, and the cold end measuring point is set at the far-fire end of the water-cooled tube 1 to be tested, and the hot end measuring point is set at the central axis point of the fin 2 closest to the water-cooled tube 1. The cold end measuring point and the hot end measuring point are set at the same horizontal height.

[0037] The temperature values ​​T of the cold end thermocouple 3 and the hot end thermocouple 4 are obtained by the data acquisition and processing system 5 冷 and T 热 , and by the formula q=k(T 热 -T 冷 )Calculate the heat flux density of the water-cooled wall heating surface.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for measuring heat flux density of a water-cooled wall heating surface, wherein the water-cooled wall heating surface comprises a plurality of water-cooled tubes (1) and fins (2) connecting adjacent water-cooled tubes; characterized in that: The device comprises a data acquisition and processing system (5) and at least one pair of thermocouples, and each pair of thermocouples comprises a cold end thermocouple (3) and a hot end thermocouple (4); the cold end thermocouple (3) and the hot end thermocouple (4) are respectively fixedly connected to a cold end measuring point and a hot end measuring point on the heating surface of the water-cooled wall, and are used to measure the temperature of the cold end measuring point and the temperature of the hot end measuring point respectively; the thermocouple is provided with a data line connected to the data acquisition and processing system (5); the cold end measuring point and the hot end measuring point are respectively arranged on the heating surface of the water-cooled wall The heat-repelling side is provided with a cold end measuring point arranged at the far end of the water-cooling tube (1) on the heating surface of the water-cooling wall, and the hot end measuring point is arranged at the central axis point of the fin (2) closest to the water-cooling tube (1); a protective sleeve (6) is arranged outside each thermocouple, and a fixing frame (7) is arranged at the end of the protective sleeve (6), and the fixing frame (7) is fixedly connected to the heating surface of the water-cooling wall. The protective sleeve (6) and the fixing frame (7) ensure that the positioning error of the cold end thermocouple (3) and the hot end thermocouple (4) is not greater than 2 mm.

2. The device for measuring heat flux density of a water-cooled wall heating surface according to claim 1, characterized in that: The cold end measuring point and the hot end measuring point are arranged at the same horizontal height.

3. A method for measuring the heat flux density of a water-cooled wall heating tube, using the water-cooled wall heating surface heat flux density measuring device as claimed in claim 1, characterized in that: The method comprises: Select the water-cooled wall heating surface to be tested, obtain its characteristic parameters, and calibrate the heat flux coefficient k of the water-cooled wall heating surface to be tested through numerical simulation; The cold end measuring point and the hot end measuring point are respectively arranged on the non-fire side of the heated surface of the water-cooled wall to be tested, and the cold end measuring point is set at the far-fire end of the water-cooled tube (1) to be tested, and the hot end measuring point is set at the central axis point of the fin (2) closest to the water-cooled tube (1); The temperature value T of the cold end thermocouple (3) and the hot end thermocouple (4) is obtained through a data acquisition and processing system (5). 冷 and T 热 , and by the formula q=k(T 热 -T 冷 ) calculates the heat flux density of the water-cooled wall heating surface; Among them, the numerical simulation calibration process of the heat flux coefficient k includes: According to the geometric structure of the water-cooled tubes and fins on the heating surface of the water-cooled wall, the periodic calculation domain is selected to carry out the two-dimensional heat transfer numerical calculation, and the inner wall of the tube is set to the boundary condition of equal convection heat transfer coefficient. The convection heat transfer coefficient h is calculated according to the following formula: Wherein, subscript b represents the working fluid temperature of the cross section of the water-cooled wall heating surface, subscript w represents the working fluid temperature of the water-cooled wall heating surface facing the fire side wall; Nu is the Nusselt number, Re is the Reynolds number, Pr is the Prandtl number; ρ is the density, kg / m 3 ; L is the inner diameter of the water-cooled wall tube; k1 is the thermal conductivity of the static working medium, W / m·K; Obtain the pipe material of the water-cooled wall heating surface to be tested, and select the thermal conductivity k1 according to the temperature range. Through numerical simulation, the functional relationship between the heat flux coefficient k of the water-cooled wall heating surface to be tested and the heat flux density of the outer wall of the water-cooled pipe is obtained: k = f(q, T 热 ,T 冷 ); By inputting at least five heat flux values ​​and obtaining corresponding at least three sets of temperature values ​​[T 热 ,T 冷 ] is calibrated to obtain the heat flux coefficient k of the water-cooled wall heating surface to be tested.

4. The method for testing the heat flux density of a water-cooled wall heated tube according to claim 3, characterized in that: The protective sleeve (6) and the fixing frame (7) ensure that the positioning error of the cold end thermocouple (3) and the hot end thermocouple (4) is no more than 2 mm.

5. The method for testing the heat flux density of a water-cooled wall heated tube according to claim 3, characterized in that: The cold end measuring point and the hot end measuring point are arranged at the same horizontal height.

6. The method for testing the heat flux density of a water-cooled wall heated tube according to claim 3, characterized in that: The characteristic parameters of the water-cooled wall heating surface include its wall thickness, the diameter of the water-cooled tube (1), the fin structure and the width of the fin (2).

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