What are the consequences of choosing an excessively high total pressure for the exhaust fan?
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Dear colleagues: For the design of our company’s new project, a variable-frequency exhaust fan has been selected. The flue gas temperature before the fan is 180°C, the flow rate under operating conditions is 350,000 cubic meters per second, the static pressure before the fan is -5000 Pa, and the static pressure after the fan is 2200 Pa. The actual flow rate indicated on the nameplate of the induced draft fan upon delivery is 350,000 cubic meters per second, with a total pressure of 7,500 Pa for the fan. During the debugging process, it was found that the static pressure before the induced draft fan was only -1600 Pa, while the static pressure behind the fan was 2400 Pa. The flow rate of flue gas from the owner side was not as high as intended in the original design. Yet, the frequency of the induced draft fan was already set at 48 Hz with a current of 77 A. I would like to ask the experts and professionals on this forum: Is it normal for the frequency of the induced draft fan to be this high under such conditions? Is it due to changes in the design conditions or issues with the equipment itself? Thank you all!
What is the rated frequency? If the actual frequency is below the rated value, there is no problem. Generally, it is at least 50 Hz at the power frequency, with 48 Hz being acceptable. The problem is that the static pressure at the inlet is below the design value; it’s likely that the fan itself does not have the necessary capability. Let’s verify the current status to see if the actual capacity of the fan meets the operational requirements.
It’s abnormal; given your current pressure level, it’s probably less than 60% of the design pressure. With such a high frequency, the flow rate will definitely be higher than the designed value. This can be compared using the fan’s performance curve. Moreover, the efficiency at your actual operating conditions will be very low
It’s abnormal; given your current pressure level, it’s probably less than 60% of the design pressure. With such a high frequency, the flow rate will definitely be higher than the designed value. This can be compared using the fan’s performance curve. Moreover, the efficiency at your actual operating conditions will be very low