HG/T 20575-1995 Chemical industry furnace resistance calculation regulations
Some standard content:
Industry Standard of the People's Republic of China
HG/T 20575-95
Specification of Resistance Calculation for Chemical Industrial Furnace199511—29 Issued
1995-—12— 01
Ministry of Chemical Industry of the People's Republic of China
Implementation
Document of the Ministry of Chemical Industry
No. 913 of Chemical Construction Development (1995)
Notice on Issuing the Industry Standard of "Regulations on Resistance Calculation of Chemical Industrial Furnaces"
To all provincial, autonomous region, municipality directly under the Central Government, and independently planned cities, and all relevant units: The "Regulations on Resistance Calculation of Chemical Industrial Furnaces", organized by the Industrial Furnace Design Technology Center of the Ministry of Chemical Industry and edited by Beijing Petrochemical Engineering Company of Sinopec, has been reviewed and approved as a recommended industry standard, with the number HG/T20575-95, and will be implemented from December 1, 1995.
This standard is managed by the Ministry's Industrial Furnace Design Technology Center, and published and issued by the Ministry's Engineering Construction Standard Promotion and Editing Center. Ministry of Chemical Industry
November 29, 1995
Industry Standard of the People's Republic of China
Regulations on Resistance Calculation of Chemical Industrial Furnaces
HG/T 20575-95
Editing Unit: Sinopec Beijing Petrochemical Engineering Company Approving Department: Ministry of Chemical IndustrybZxz.net
Effective Date: December 1, 1995 Engineering Design Standard Editing Center of the Ministry of Chemical Industry
2. Calculation source and calculation formula,
2.1 Calculation source
2.2 Friction resistance along the way
Resistance of transverse impact tube bundle
Local resistance
Determination of original data
3 Calculation of resistance of flue gas channel
Resistance of convection section heat exchanger
Resistance of air preheater
Resistance of flue
Resistance of dust collector
3.6. Smoke window resistance during mechanical ventilation··3.7
Spontaneous duct wind
Total pressure drop in the smoke duct
Calculation of smoke duct resistance during natural ventilation
4 Calculation of air duct resistance
Resistance of cold air duct
Resistance of air preheater
4.4 Resistance of hot air duct
4.5 Resistance of combustion device
Spontaneous ventilation
Total pressure drop in the air duct
(3)
5 Selection of forced draft fan and induced draft fan
5.1 Selection General
5.2 Selection of forced draft fans and induced draft fans
6 Calculation of resistance of fluid in furnace tubes·
6.1 Calculation of resistance of fluid in furnace tubes without phase change 6.2 Flow resistance of fluid in furnace tubes with phase change Appendix A Common physical properties of gases in ventilation calculation Appendix BE
Charts for resistance calculation
Instructions for preparation
1.0:1 This standard applies to the calculation of resistance of flue gas, air passage and medium flow in normal pressure chemical industrial furnaces and tubular furnaces with combustion system, blast system and flue gas system.
This standard does not apply to reactors with fillers or catalysts and special industrial 1
ww.bzsoso:com2 Calculation principles and calculation formulas
2.1 Calculation principles
2.1.1 Friction resistance along the way The calculation formulas for transverse scouring resistance and local resistance are all based on isothermal flow conditions, that is, the viscosity and density of the flowing medium are constants. 2.1.2. In order to make the calculation method of negative pressure ventilation, positive pressure ventilation and balanced ventilation uniform for the air and flue gas flow rate in all furnaces, the pressure should be converted to the velocity under 101.32 kPa for calculation, and then the pressure difference correction should be made. Therefore, for all cases, the dry air line calculation diagram with a pressure of 101.32 kPa can be used. 2.1.3 The Reynolds number Re in the resistance calculation can be determined by the curve shown in Figure B.1 (see Appendix B, the same below) based on the air flow velocity W, gas temperature t and channel diameter d. This curve is drawn based on dry air at a pressure of 101.32 kPa. The Reynolds number of flue gas in the calculation can also be determined according to Figure B.1. For furnaces with positive pressure ventilation, in order to determine the value of the required Reynolds number Re according to Figure B.1, the velocity converted to 101.32 kPa should be used as the calculation velocity.
2.1.4 The dynamic pressure head h in the resistance calculation can be obtained from Figure B.2 based on the air flow velocity W and gas temperature t. Figure B.2 is drawn based on dry air at a pressure of 101.32 kPa, and can also be used to determine the dynamic pressure head value of flue gas in furnace pressure calculation. 2.1.5 The resistance of the channel is calculated based on the average pressure of the flue gas or air. The average pressure is taken as half of the sum of the absolute pressures at the beginning and end of the channel. In order to facilitate the calculation, the pressure is 101.32 kPa, and the temperature is 0.0℃. Dry air (density 0 = 1.293 kg/m2) is used to replace the actual working medium (flue gas or air) at the same pressure or converted to this pressure for resistance calculation, and the line diagram of the pressure drop is drawn accordingly. At the end of the calculation, the density difference between the flue gas or air at 101.32 kPa and the dry air under the standard state, the dust content, and the difference between the average pressure of the channel and 101.32 kPa are corrected. The same corrections must be made when the resistance of individual sections of the channel must be determined. 2.2 Friction resistance along the way
2.2.1 When the medium passes through a channel of equal cross-section, including the longitudinal scouring of the tube bundle by the medium, the friction resistance △hm generated by the medium flowing along the wall can be calculated by the following formula: Ahadl we
In--friction resistance coefficient along the way,
1 channel length, m,
d equivalent diameter of the channel section, m,
W--medium flow rate, m/s,
g--medium density, kg/m calculated at the average temperature. (2.2.1)
2.2.2 The friction resistance coefficient along the way is related to the Reynolds number Re and the relative roughness k/d of the tube wall (k is the absolute roughness, d is the equivalent diameter of the channel), and its value can be found in Figure B.3 (the inverse of the relative roughness is taken as the parameter in the figure). In addition to looking up the diagram, the friction resistance coefficient along the route can also be calculated. The calculation formula of the resistance coefficient is obtained by experiment in a circular pipe. For non-circular pipes, the equivalent diameter is used, and its accuracy is also sufficient. In laminar flow (Re<2×10°), the friction resistance coefficient is only related to the Reynolds number Re, but has nothing to do with the roughness. Its value can be determined by the following formula: 64
(2.2.2—1)
When the relative roughness k/d=0.00008~0.0125 and the Reynolds number Re=4×10, it can be obtained by the following formula or by referring to Figure B.3:
k 68)0.25
=0. 11(+Re
For a smaller area, it can be calculated according to the following formula. (2.2.2—2)
For the "smooth" pipe in engineering, that is, the pipe whose resistance is independent of roughness at a given Reynolds number Re, when the Reynolds number Re≥2×103, the resistance coefficient is calculated according to the following formula:
(ugRe-0. 9)2
(2.2.2-3)
When the Reynolds number Re is 4×10°～100×103, the resistance coefficient of the "smooth" pipe is calculated as follows:
(2. 2.2-3) 3a)
In the area of square law of resistance, the resistance coefficient λ is only related to the relative roughness of the tube wall, but has nothing to do with the Reynolds number Re. The resistance coefficient is determined by the following formula: 1
k absolute roughness of the tube wall, m,
the value of the absolute roughness of the tube wall is selected according to Table B.1. (2.2.2-4)
2.2.3 For furnaces designed according to sufficiently approximate conditions, the friction resistance coefficients of most components can be approximately determined according to the following provisions. 2.2.3.1 For the case where flue gas or air flows in the tubes of a tubular air preheater with a relatively smooth channel wall and an equivalent diameter of 20 to 60 mm or in the gaps of a plate air preheater, when the medium temperature is less than or equal to 300°C and the medium velocity is 5 to 30 m/s, and when the medium temperature is greater than 300°C and the medium velocity does not exceed 45 m/s, the friction resistance coefficient λ can be determined by the following approximate formula: 0.335 (
y0. 17 Re-0. 14
(2. 2. 3-- 1)
For ease of use, Figure B is drawn according to formula (2.2.1) and (2.2.3--1).4. The line calculation diagram can be used to determine the friction resistance consumed by the flowing medium in each meter of air preheater tube or gap. The total friction resistance can be calculated by multiplying the value 4
by the total length of the channel.
2.2.3.2 When flue gas or air flows in a rotary air preheater along a heat storage channel composed of corrugated plates or alternating corrugated plates and flat plates, the friction resistance coefficient can be determined according to the following provisions:
(1) When the corrugation direction of the corrugated plate forms a certain angle with the airflow direction (No. 1 in Figure 2.2.3-1), the friction resistance coefficient of the flow in the channel is determined by the following formula: A=(1+11.1)
(2.2.3-—2a)
The value of the friction resistance coefficient of flow in a smooth channel can be calculated according to formula (2.2.23) or determined by referring to Figure B.5:
The nominal roughness of the channel,.
a, b--respectively, the clear height of the corrugation of the two corrugated plates including the manufacturing tolerance (Figure 2.2.3-1), mm;
Average spacing of the corrugations of the two corrugated plates along the medium flow direction, mm. Filling
Figure 2. 2. 3 1
Simplified diagram of the filling of the rotary air preheater (a+b)
Including 2mm
The applicable range of formula (2.2.3-2a) is 2.5≤c≤3.5 (c is the plate spacing, in mm), 0.04≤k≤0.2, 1.2×103≤Re≤104. The value of the friction coefficient can be obtained according to formula (2.2.3-2a), or it can be determined directly by looking up Figure B.5 according to the Reynolds number Re and the nominal roughness E of the channel. For the channel composed of corrugated plates and flat plates (No. 3 in Figure 2.2.3-1), the calculation of the resistance coefficient can also be determined according to formula (2.2.3-2a). However, the value of S depends only on the size of the corrugated plate.
(2) For the heat storage body with triangular channels composed of offset sections (No. 4 in Figure 2.2.3-1), the calculation formula for the resistance coefficient of flow in the channel is: A=X4.47
- 0. 25 =- AgCcs
(2.2.3-2b)
The friction coefficient of the smooth channel can be calculated according to formula (2.2.2-3) or determined by referring to Figure B.5: d. —Equivalent diameter of the channel in the heat storage body, mm; 1--The length of the offset section, mm;
The shape coefficient of the heat storage body with a triangular channel is determined according to d. Refer to Figure B.5.
The applicable range of formula (2.2.3-2b) is offset 82mm~3.5≤l/d≤40.1.6X103≤Re104
(3) For the checkered plate heat storage body (No.5 in Figure 2.2.3--1), the calculation formula for the resistance coefficient flowing along the heat storage body channel is:
+1.3)=AC
(2.2.3--2c)
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