What’s wrong with the calculation process for determining the optimal thickness of insulation for steam pipes?
Thread Content
The optimal insulation layer for steam pipes is calculated using the formula in section 4.3.2.1 of the GB50264-1997 Code for Design of Thermal Insulation of Industrial Equipment and Piping. Where D0=0.159m, Pe=45 yuan/GJ (130 yuan per ton of steam), λ=0.04 (based on rock wool), τ=6000h (the symbol cannot be found), T0=160℃ (average temperature of the boiler), TA=15℃ (annual average temperature), PT=500 yuan/m3, s=0.1233 (0.04 interest rate over 10 years), and the heat transfer coefficient α=11.63 (calculated as a constant value). Based on the above data, the thickness of the insulation layer calculated to be over 14 cm; however, most people suggest that 9 cm is sufficient. I don’t understand why there’s such a difference – I’m not sure what’s wrong with my calculation. I hope experts here can help me out; I’m a beginner seeking guidance
Calculation of the economic thickness of the insulation layer
Project name: ________________________
Person performing the calculation: ________________________
Name of the pipeline: ________________________
Person reviewing the calculation: ________________________
Date: ________________________
Parameter input:
Serial number | Item | Symbol | Unit | Value | Remarks
1 | Dimension | D0 | mm | 159 |
2 | Medium temperature | t | °C | 160 |
3 | Ambient temperature | ta | °C | 15 |
4 | Average outdoor wind speed | w | m/s | 1 |
5 | Energy price | Ph | yuan/106 kJ | 45 |
6 | Unit cost of insulation layer | P1 | yuan/m³ | 500 |
7 | Annual interest rate | i | – | 4 |
8 | Calculation period | n | years | 10 |
9 | Annual operating time | τ | hours | 6000 |
10 | Insulation material | – | Rock wool, slag wool | |
11 | Initial thermal conductivity of insulation | λ0 | W/(m·K) | 0.044 |
12 | λ = λ0 + A(tm – B); A = –0.00018 | | | |
13 | B = –70 | | | |
14 | Type | – | Pipeline | |
15 | Installation location | – | Outdoor | |
16 | Operation mode | – | Throughout the year | |
Calculation results:
1 | Insulation thickness | δ | mm | 190 |
2 | Heat transfer coefficient | a | w/(m²·K) | 18.61 |
3 | Thermal conductivity of insulation material | λ | W/(m·K) | 0.04715 |
4 | Temperature of the outer surface of the insulation layer | ts | °C | 16.1 |
5 | Heat loss | w/m² | 20.6 |
6 | Maximum allowable heat loss | w/m² | 108 |
Project name: ________________________
Person performing the calculation: ________________________
Name of the pipeline: ________________________
Person reviewing the calculation: ________________________
Date: ________________________
Parameter input:
Serial number | Item | Symbol | Unit | Value | Remarks
1 | Dimension | D0 | mm | 159 |
2 | Medium temperature | t | °C | 160 |
3 | Ambient temperature | ta | °C | 15 |
4 | Average outdoor wind speed | w | m/s | 1 |
5 | Energy price | Ph | yuan/106 kJ | 45 |
6 | Unit cost of insulation layer | P1 | yuan/m³ | 500 |
7 | Annual interest rate | i | – | 4 |
8 | Calculation period | n | years | 10 |
9 | Annual operating time | τ | hours | 6000 |
10 | Insulation material | – | Rock wool, slag wool | |
11 | Initial thermal conductivity of insulation | λ0 | W/(m·K) | 0.044 |
12 | λ = λ0 + A(tm – B); A = –0.00018 | | | |
13 | B = –70 | | | |
14 | Type | – | Pipeline | |
15 | Installation location | – | Outdoor | |
16 | Operation mode | – | Throughout the year | |
Calculation results:
1 | Insulation thickness | δ | mm | 190 |
2 | Heat transfer coefficient | a | w/(m²·K) | 18.61 |
3 | Thermal conductivity of insulation material | λ | W/(m·K) | 0.04715 |
4 | Temperature of the outer surface of the insulation layer | ts | °C | 16.1 |
5 | Heat loss | w/m² | 20.6 |
6 | Maximum allowable heat loss | w/m² | 108 |
Could you send me a copy of the calculation table? 605386754@qq.com
I’m asking the same thing – could you send me a copy of this table? My email address is xue* 601087456@qq.com. Thank you very much: handshake
Basically, there should be relevant company regulations available... Of course, from a computational perspective, 14CM↑ is required; in reality, however, the thickness of the insulation material is fixed... That’s just how it is manufactured by the material producers. Even if the thickness increases significantly, the temperature of heat reaching the surface remains more or less the same...