Heater math questions

[rjb1211]

I know the formula for figuring time for heat rise but I have a couple of question:

>If a gas or propane heater is rated at 325,000 BTUs is that before or after applying the efficiency rating? I guess I need a better understanding of the efficiency rating.

>I realize that air temp will have an impact on this. Is there anyway to calculate that?

Thanks

 

[JoyfulNoise]

The heater’s BTU rating is based on the amount of gas consumed, not the amount of heat transferred. So you apply the efficient factor to the heater rating.

As for air temp, try this - Heat Loss from Open Water Tanks

 

[JoyfulNoise]

You can also use these two pages to help with calculations -

Swimming Pool Heaters

Calculate outdoor swimming pool heaters.

www.engineeringtoolbox.com

Evaporation from a Water Surface

Evaporation of water from a water surface - like a swimming pool or an open tank - depends on water temperature, air temperature, air humidity and air velocity above the water surface - online calculator.

www.engineeringtoolbox.com

 

[rjb1211]

You can also use these two pages to help with calculations -

Swimming Pool Heaters

Calculate outdoor swimming pool heaters.

www.engineeringtoolbox.com

Evaporation from a Water Surface

Evaporation of water from a water surface - like a swimming pool or an open tank - depends on water temperature, air temperature, air humidity and air velocity above the water surface - online calculator.

www.engineeringtoolbox.com

Perfect. Thank you.