How can I calculate energy loss from a leak in a large furnace?

[rdolin]

How can I calculate energy loss from a leak in a large furnace?

I currently am working on a large furnace about 1200 square feet. To heat the furnace we use a combination of air and methane at a ratio of 9.54:1. There is currently a hole in the furnace and I would like a formula to calculate the energy loss. We have the temperatures and the pressures to use in the formula. If you can please give me some tips of an equation to determine the energy loss I would greatly appreciate it. Thank you.

 

[russ_watters]

If you have the pressure, you can use Bernoulli's equation to calculate the airflow. If you have the temperature of the leaving air, you can multiply that by airflow and the specific heat of air and get energy (power) loss.

 

[RTW69]

I agree that you can use Bernoulli's equation but assuming the gas mixture leaving the furnace is dry air seems to me to be an over simplification. The mixture in the furnace is probably closer to a combustion gas comprised of O₂, CO₂, CO, N₂ and water vapor.

You can use Bernoulli and the continuity of mass equation to find the mass flow rate of the combustion gas leaving the hole. The heat loss in the dry flue gases can be determined from q=m-dot*c_p*(T_gas-T_air) The properties of nitrogen is frequently assumed for the dry combustion gas.

But the combustion gases are not dry and you must account for vapor formed in the products of combustion so you must account for the change of enthalpy of the superheated steam at the gas exit temperature and the enthalpy of saturated water. This component might be small but you should be aware of it.

 

[russ_watters]

Good point, but whether you account for the vapors depends on the particulars of the problem. Ie, if the furnace doesn't normally condense the water vapor, then you don't need to account for it in the lost energy.

 

[cragar]

Calorimetry , maybe this will work , how about sticking a beaker of water near the hole and seeing how much the heat raises the temp of the water . just a thought , I’m sure the above responses are better

 

[izinho]

i want to learn how to solve pressure loss and head loss.