Question

1 = Consider a part with volume V = 5 x 10-6 m’, surface area A = 1x10-3 m², mass density P 5000 kg m-3, heat capacity Cp 500 J kg-1 K-1. The part initially has a uniform temperature of Tp : 500 °C. It is suddenly immersed in a fluid at To 25 °C with a heat transfer coefficient of h 20 W m = = -2 K-1 = Based on a control volume that encompasses the part and using an energy balance, determine the initial rate of change of the part's tem- perature (i.e., dT /dt).

Answer 1

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Solution : Given thel → V = 5x100 m² A = [X1033m2 8= 5000 kg/m² Cp = 5003/kg-k Tp = 50°c To=Sox 250 h = 20 W m²k According to the energy bolances Role of charge of internal enersy Rate of het of the Body corrected from the body - (mcp d) = hast de _-ha (Tp-to of initial condition AT ={{p-7-) - dt ما(37) de dt = dox (x10-3)* ( 500-25) 56eox (5 x 10-6x 500 dr dt - 0.76 / = here he sign shows that temperature is decressing with respect to time.