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 combustionwas 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. . The solid surface temperatures of regions 2, 3, 4
and 5 were recorded, and region 1 temperature was considered as
the ambient air inlet temperature due to negligible temperature
difference between combustor solid surface and air. The velocity