Question 21 on the morning of the first day of 2011
Thread Content
Heat transfer coefficient values for convective heat transfer in three fluids: air flow velocity of 30 m/s, water flow velocity of 1.5 m/s, and steam condensation
Why? Could you explain it?
Steam condensation > Water flow velocity 1.5 m/s > Air flow velocity 30 m/s
The air flow velocity is 30 m/s and the water flow velocity is 1.5 m/s; the steam condensation rate increases accordingly. According to the formula for convective heat transfer coefficient = ARe^a.Pr^b / thermal conductivity / pipe length, since the thermal conductivity and Pr value of air are much lower than those of liquids, the convective heat transfer coefficient for air is the lowest. The latent heat of steam condensation is very high, so its convective heat transfer coefficient is the highest