BTU to CFM to CFH
Determining Air Flow Rate using Thermal Mass Flow Meter
When utilizing a thermal mass flow meter to gauge gas flow rate, it may be necessary to determine the CFM (cubic feet per minute) or CFH (cubic feet per hour) values from the BTU (British thermal unit) per hour data output supplied by the meter.
Here’s how to do it:
One of the most commonly used units of measurement for quantifying natural gas is the therm, which is widely recognized in the industry.
Fun fact: Have you ever heard of a “therm”? It’s actually a unique unit of measurement for energy, defined as exactly 100,000 British Thermal Units (BTUs). But here’s where it gets even more interesting: a therm can also be converted to other units, such as 29.3 kilowatt-hours or 105.5 mega-joules. Pretty cool, right?
A therm’s worth of natural gas contains 96.7 cubic feet/therm, or about100 cubic feet/therm.
With its high energy content and adaptability, natural gas serves as a valuable source of energy. One of its most noteworthy attributes is its capacity to convert seamlessly between two widely-used measurement units: BTUs per hour and cubic feet per minute (CFM). As a result, converting between BTUs per hour and CFM (or vice versa) is a simple and straightforward process.
To calculate the CFM (ft3/min) or CFH (ft3/hr) for 500,000 BTUs per hour of Methane we have:
500,000 BTU/hr ÷ 100,000 BTU/therm = 5 therms/hr.
5 therms/hr × 96.7ft3/therm = 483.5 ft³/hr.
483.5 ft3/hr ÷ 60min/hr = 8.06 ft3/min
Watch this quick video to see EXACTLY how to calculate the SCFM or SCFH flow rate for a 500,000 BTU/Hr boiler.