Question

calculate the quantity of air supplied per kg of fuel burnt in the combustion chamber of the boiler when the required draught of 1.85 cm of water is produced by a chimney of 32 m height. The temperature of the flue gases and ambient air recorder are 370°C and 30°C respectively.

Answer 1

Solution;

Given;

Height of chimney,H=32m

Draught,h=1.85cm of water=18.5mm of water

Ambient temperature,T_a=30°c=303K

Temperature of the flue gases; T_g=370°c=643K

Let m_a be the mass of air supplied per kg of fuel.

Draught is calculated as;

$h=353H[\frac{1}{T_a}-\frac{m_a+1}{m_aT_g}]$ mm of water

By direct substitution;

$18.5=353×32[\frac{1}{303}-\frac{1}{643}-\frac{1}{643m_a}]$

Simplify;

$-1.0737×10^{-4}=-\frac{1}{643m_a}$

Hence;

$m_a=14.48kg$