Seeking advice on the diameter of the drum circulation pipe
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The calculated steam generation capacity of the steam generator is 20 t/h; it operates in natural circulation, with a circulation ratio of 60. It is determined that 6 rising tubes are required (with a diameter of 219), and the flow velocity inside the tubes is 1.94 m/s. I think this calculation is too conservative. What is the maximum flow velocity inside the pipe? Is it appropriate to use a cycle multiplier of 60? I appreciate your advice. Thank you
Based on the design experience of natural circulation boilers: 1. **Circulation ratio**: 60 is on the high side; typically, the circulation ratio for natural circulation boilers ranges from 4 to 30. It is recommended to adjust it to 15–25 depending on the operating pressure and boiler type (it can be reduced slightly for medium- and low-pressure boilers). 2. **Flow rate**: 1.94 m/s is on the low side. The recommended flow rate for natural circulation risers is generally 3–8 m/s; higher flow rates (such as above 5 m/s) can enhance heat transfer and reduce the risk of vapor-liquid separation. 3. **Optimization suggestions**: - The number of riser pipes can be reduced (e.g., 4 Φ219 pipes), increasing the flow velocity to around 3 m/s ； - Review the cycle multiplication factor, and adjust it to a reasonable range (such as around 20) in consideration of pressure and heat load ； - It is necessary to verify cycle reliability (such as cycle driving force, steam content, etc.) to avoid stagnation or backflow. It is recommended to recalculate the stability of the circulation loop using specific parameters (pressure, heat load). .
Typically, the circulation ratio for natural circulation boilers ranges from 4 to 30. Is there any reference manual available for this? I haven’t been able to find this convenient information. Thank you
This is related to steam pressure; essentially, it is the density difference of steam and water that provides the driving force for circulation. For specific calculation parameters, refer to relevant boiler design standards and manuals