The heat transfer coefficient (h) for a vapor bubble rising through a boiling li
ID: 1848013 • Letter: T
Question
The heat transfer coefficient (h) for a vapor bubble rising through a boiling liquid is given by where h = A where V = 1 / 4 heat transfer coefficient (e.g.. Btu/(hr degree F ft2)], cp = liquid heat capacity [e.g.,cal/(g degree C)],k = liquid thermal conductivity [e.g.. J/(s Km)], sigma = liquid/vapor surface tension [e.g., dyn/cm], delta rho = rholiquid - rhovapor = rho1 - rhov, d = bubble diameter. and g = acceleration due to gravity. What are the fundamental dimensions of V and A? If the value of h is 1000 Btu/(hr ft2 :F) for a 5mm diameter steam bubble rising in boiling water at atmospheric pressure, determine the corresponding values of V and A in SI units. You must look up values for the other quantities you need: be sure to cite the sources you use for these data.Explanation / Answer
1)= M/L3 ; g= L/T2 ; = newton/meter=M/T2
V = L/T
A= L2
2) Assuming liquid to be water and vapour to be air
density(water)= 1000kg/m3 ; density(air) =1.225 kg/m3 ; g=9.8 m/sec2
surface tension for air-water interface = 0.072 N/m4
V= 4.655 m/sec
h=5678.3 in SI units ; k(water)=0.61 w/m2-K ; Cp(water)=4185 J/kg-K ; =1.225kg/m3 ; d=0.005m
A=3.3 m2
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