Which of the following measurements can be used to calculate boiler efficiency?
A. Feedwater flow
B. Blowdown flow
C. Steam flow
D. Drum level
E. Drum pressure
The feedwater flow (Answer A), blowdown flow (Answer B) and steam flow (Answer C) can be used to calculate the flow of heat either into or out of the boiler. As such, they can be used to calculate boiler efficiency. However, as a practical matter, the blowdown flow is rarely measured because it typically contains a relatively small amount of heat.
The drum level (Answer D) is not indicative of heat flow and would not be used to calculate boiler efficiency.
The drum pressure (Answer E) is not indicative of heat flow but could be used to pressure compensate the steam flow measurement.
Additional complicating factors
Additional measurements such as the feedwater temperature, multiple fuel flows and the like might be needed to calculate boiler efficiency of the system at hand.
David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes LLC, which offers engineering, seminars, strategic, marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies. Spitzer and Boyes is also the publisher of the Industrial Automation INSIDER. He has more than 40 years of experience and has written more than 10 books and 350 articles about flow measurement, instrumentation and process control.
Spitzer may be reached at 845-623- 1830 or via spitzerandboyes.com. Click on the "Products" tab to find his Consumer Guides to various flow and level measurement technologies.