to the experimental system and the unknown thermal heat transfer coefficient h due to the convection effect being changed as a parameter fig5 a shows a fan structure 300 shown in fig3 fig5 b shows a cross section of the blade assembly 500 comprising a blade 502 oil 504 conductor 506 and heat source 510 fig6 shows the effect of thermal conductivity h on the source temperature the observed value of 126 degrees c at 29 w total power input matched the estimated results when h 50 w m 2 k fig6 illustrates an estimation of h it also reveals that if the source temperature were to be kept near 70 degrees celsius then the h value must be increased to values above 150 w m2k it is well known that a continuous no slip surface within a fluid flow field allows the boundary layer to grow a boundary layer essentially means a near stagnant fluid layer above the heat conducting surface thus it is important to minimize the boundary layer build up fig7 a c show a simple modification to the tested blade structure where several slots are provided for the fluid to become detached from the surface for reducing the boundary layer effect fig7 a and 7b show different views of a fan blade with a spiral pattern of fins in fig7 b there is shown three cascading fins in the.