In each case, calculate the Biot number for the object and indicate whether or not the lumped approximation is valid.
a) A carbon-steel rod of length 2m and diameter 10cm is set in a crossfow of air, which results in a convective heat transfer coecient of 2*( W/m^2K).
b) A teflon sphere of diameter 20cm is dunked in an agitated tank of oil, which results in a convective heat transfer coecient of 20*( W/m^2K).