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the outside air is colder, but the flame temperature is still much much hotter than that so the difference cold inlet air makes on the outlet temperature of the furnace will be small.
The same commentary applies to the density argument: yes, but the effect is small.
The fact that the outlet air is at 43 C represents the 8% efficiency loss of your furnace. ...
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calculation of exit temperature
The heat transfer rate between $\dot{Q}$ oil and water should be equal to the change in heat capacity in the medium.
$$\dot{Q}= m_oC_{p,o}\delta T_{o} = - m_wC_{p,w}\delta T_{w}$$
you can solve this algebraically and obtain:
$$ 2.27 \cdot 2198 \cdot(150−40)= 1.36\cdot 4187 (T_{wo}−21)$$
$$ T_{wo} =\frac{2.27 \cdot 2198 \cdot(...
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Thermal equilibrium will be reached when heat in = heat lost.
Find the U-value for each surface and calculate the heat loss rate in W/K (watts/kelvin) for each surface.
Add them up and you've got the heat loss rate for the whole room.
From this you can calculate the ΔT between inside and outside at equilibrium.
For a give outside temperature you can now ...
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Outside air is colder. Does this decrease the maximum temperature of the flames?
Your furnace will always need air for combustion. This combustion air must ultimately come from the outside. Combustion air can either come directly from outside (say it's 30F outside) or it can leak into your house, go through the heater and be warmed up from 30F to 70F, and ...
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Did you ever get a real answer to your question? I have been considering this question for years and I have no real answer. Many responses I see show me that people are a bit confused as to what you are trying to do. In a simplistic explanation you are trying to move thermal energy from a 70 degree environment into a say 75 degree environment which is very ...
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