Water vapor/ moisture from a propane fireplace

Divide the heat rating by the heat of combustion of propane, available at http://www.seered.co.uk/folk95a.htm, to give the number of moles of propane consumed per unit of time. 4 moles of water are produced from each mole of propane burnt, so multiplying by 4 gives the number of moles of water produced per unit of time. Then, either:

• multiply by 18gm/mol to achieve the mass flow rate, or
• multiply by 22.4 litres per mole at 25degC to give a volumetric flow rate at that temperature, then correct the volumetric flow to allow for the actual temperature of the combustion product gases.

There are some unit conversions to do along the journey: http://www.simetric.co.uk/ can help.

For the complete combustion:

C3H8 + 5 O2 -----> 3 CO2 + 4 H20(g)

30,000 BTU/h = app. 8.8 kW

Q=VxHix0.278 V = 0.68 kg/h Hi = 46.34 Mj/kg

0,044 kg/h C3H8 0,072 kg/h H2O

0.68 C3H8 ? H2O

H20 (g) = 1.112 kg/h

Well I can't say exactly how much, but I can say quite a bit. I have a small 500 sq ft cabin in the mountains, and thought this to be a good source for heating it. However, it produced so much vapor that the windows and doors sweat when it ran, so I had to purchase a dehumidifier to run while it was on. I had to resort last winter to installing a heat pump.

When the heater failed in my minivan, I warmed it with a propane heater for a few minutes one winter morning. I only did it one time because the windows condensed so much water on the inside surfaces that I had to open all the doors to get rid of the damp air. I knew that hydrocarbon combustion produces water vapor, but I had never seen such a dramatic demonstration.

Perhaps the propane fireplace needs an efficient heat exchanger like the gas furnace in my home that has a chimney. Some of the ventilated water vapor could possibly be recaptured and used to humidify the dry winter air inside the home.

there;

a vent fer the stove would be much better than than dehumidifer /

A gallon of propane gives about 90,000 BTU, burning a gallon of propane produces about a gallon of water (in vapor). If you are venting to the outside of the house, as soon as the vent gets hot and a good draw is established then you should not have to worry about the water vapor in the house.

If it is an un-vented fireplace then it probably will help keep the humidity to a comfortable level.

I would recommend testing before investing.

If 90,000 btu's provides 1 gallon of water, boil a gallon of water on the stove once every 3 hours until it is completely vaporized. Or boil 1/3 gallon every hour.

You will know within several hours if the unit will deliver too much moisture for the area you are trying to heat.

Since this is a fireplace, take into consideration how long and how frequently it will be in operation. Is it for recreation only or is it intended as a replacement for another source of heat.