A titanium alloy blade from an axial compressor for which k = 25 W/m K, p = 4500 kg / m3 and C = 520 J/kg K, is initially at 40C. Although the blade thickness (from pressure to suction side) varies along the blade, the effective length scale for conduction may be taken as 3mm. When exposed to a hot gas stream at 350C, the blade experiences a heat transfer coefficient of 150 W/m2 K. Use the lumped mass approximation to estimate the blade temperature after 50 s. Firstly, check that Bi < < 1 Bi=hL/ k = 150 x 0.003 / 25 = 0.018. So the lumped mass method can be used.