A series of biomass combustion tests were carried out using 5 kg
fuel in the combustor. Initially, the biomass fuel was ignited at the bottom central position of
the combustor. After that, the flame was self-sustained by the gases released from the fuel. The air
supply to the fuel combustion was not controlled as such but the air inlet vent remained fully open
for all the experiments. However, it was mainly due to natural draught, and the velocity of flue
gasses was continuously measured and used for calculating the heat taken away by the flue gasses.
In order to improve the accuracy of quantifying the heat transfer between ambient and external
surface of the system, the external surface was divided into four vertical regions 1, 2, 3 and 4.
The lid of the combustor is region 5 as shown in Fig. 2. Region 5 has a horizontal flat surface, so
the convected heat transfer is different when compared with the vertical cylindrical surfaces. .