Film Coefficient Formula - John Campbell

[Angsi]

I have taken the following formula from Chap 13, John Campbell's text (Gas Conditioning and Processing, Vol II)

h= A * (k/d) *(d*v*roh/mew)^a * (Cp*mew/k)^b

where,

h = film coefficient, W/(m2.K)
A = proportionaliy constant
k = fluid thermal conductivity, W/(m.K)
d = tube inside diameter, m
v = fluid velocity, m/s
roh = fluid density, kg/m3
Cp = fluid specific heat capacity, kJ/(kg.K)
mew = fluid viscosity, kg/(m.s)
a = coefficient on Reynolds No.
b = coefficient on Prandtl No

A, a and b constant were taken from his Table 13.1 and typ values are like 0.02-0.26, 0.6-0.8 and 0.3-0.4 respectively for various tube arrangment and shell/tube fluid types and duties.

The reason I am aksing this is because when ever I tried using this formula, I am getting tube side film coefficient of approx 500 W/m2.K when I know that these values should be higher. Note that I think the expression Cp should really be in J/kg.K, not kJ/kg.K.

Values used are:

d, m = 0.01575
k, W/m.K = 0.03985
v, m/s = 6.99
roh, kg/m3 = 94.77
Cp, kJ/kg deg C = 1.909 (but I think it should be 1909 J/kg.K and have used this figure 1909 in calc)
mew, kg (m.s)= 0.0179 (which I assume equates to 0.0179 mN-s/m2)
A = 0.0225
a = 0.8
b = 0.4

Result: h = 790 W/m2.K

The tubeside fluid is dry natural hydrocarbon gas. The average film coefficient on the tubeside as printed out by the HTRI software shows 2168.99 W/m2.K. I am not getting anywhere close to this number.

Can someone please help?

Thanks in adavnce.

 

[Angsi]

I have re-phrased the question.

What is the formula (in metric units) for calculating the forced convection film coefficient?

Thanks.

 

[25362]

Sorry for the delay. Try to recalculate the Re based on a viscosity 1/1000 the quoted value, which is in mPa.s, and you'd probably find a result quite near the tabulated one.