|
Counter & Parallel Flow Heat Exchanger Tube Length Calculation |
|
|
Input data in YELLOW
Update and Reset funtions at bottom of page. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Heat transfer, Q = |
U*A*∆Tm |
|
|
|
|
|
|
|
|
Plane wall heat transfer coefficient, U = |
1 / (1/ho + L/K + 1/h1 |
|
|
|
|
Cylindrical wall heat transfer coefficient, U = |
1 / (1/hi + [RoLn(Ro/Ri)]/K + Ri/Ro) |
|
|
|
i and o refer to inside and outside tube surfaces. |
|
|
|
|
Large temperature difference, ΔTbc = |
Ta - Td |
|
ΔTbc = |
|
From Input Data below. |
|
Small temperature difference, ΔTad = |
Tb - Tc |
|
|
ΔTad = |
|
From Input Data below. |
|
Logarithmic mean temp. difference, ΔTm = |
(ΔTbc - ΔTad)/ln(Tbc/ΔTad) |
|
Answer: ΔTm = |
|
deg C |
|
|
|
The added resistance to heat transfer caused by corrosion is called fouling. |
|
Fouling factor, R ranges between 0.0005 and 0.002. See manufactures data. |
|
Fouling factor, R = |
(1/Udirty) - (1/Uclean) |
|
|
|
|
Forced Convection - in Coiled Tube Heat Exchangers |
|
Turbulent flow in coiled tube. |
Input Data |
|
Temp. of Fluid (Liquid) flowing in, Ta = |
|
deg C |
|
|
|
Temp. of Fluid (Liquid) flowing out, Tb = |
|
deg C |
|
|
Tc = |
|
deg C |
|
|
|
Td = |
|
deg C |
|
|
Tube inside diameter, Di = |
|
mm |
|
|
Tube outside diameter, Do = |
|
mm |
|
|
Velocity of Fluid (Liquid) in tube, V = |
|
m / s |
|
|
|
|
|
Water properties at temperature Tb deg C from the table above: |
|
Fluid (Liquid) density, ρ = |
|
kg / m^3 |
|
|
|
Cp = |
|
k*J/kg*K |
|
|
|
Fluid (Liquid) dynamic viscosity, μ = |
|
kg / m*s |
|
|
|
Fluid (Liquid) conductivity, k = |
|
W / m*K |
|
|
|
Prandtl number, Pr = |
|
- |
|
|
|
Factor, n = |
|
|
|
|
|
Velocity of Fluid (Liquid) in tube, V = |
|
m / s |
|
|
|
|
|
|
|
Results |
|
|
Fluid (Liquid) bulk temperature, Tb = |
(Tin + Tout) / 2 |
deg C |
|
Answer: Tb = |
|
deg C |
|
Reynolds Number, Re = |
V*D / ν |
|
|
|
or, Re = |
V*D*ρ / μ |
|
|
Answer: Re = |
|
Turbulent |
Re >4000 |
|
|
|
Convective heat transfer coefficient, h = |
0.023*(Re^.8)*(Pr^n)*(k/d) |
|
|
S.I. Answer: h = |
|
W / m^2*K |
|
U.S. Answer: h = |
(W/m^2*K)/5.5956 |
Btu/hr-ft^2*F |
|
U.S. Answer: h = |
|
Btu/hr-ft^2*F |
|
|
|
S.I. Answer from above: h = |
|
W / m^2*K |
|
Large temperature difference, ΔTbc = |
Tb - Tc |
|
|
Answer: ΔTbc= |
|
deg C |
|
|
|
|
|
|
|
Small temperature difference, ΔTad = |
Ta - Td |
|
|
|
|
Answer: ΔTad = |
|
deg C |
|
|
|
|
|
|
Logarithmic temperature difference, ΔTm = |
(ΔTbc - ΔTad)/ln(Tbc/ΔTad) |
|
Answer: ΔTm = |
|
deg C |
|
|
|
|
Overall heat transfer coefficient = |
Uo |
|
|
Heat flow rate, Q = |
Uo*A*ΔTm |
|
|
Heat flow rate thru inside tube wall, Qi = |
Uo*π*di*L*ΔTm |
|
|
Heat flow rate thru outside tube wall, Qo = |
Uo*π*do*L*ΔTm |
|
|
Uo = |
h *Ai / Ao |
|
|
|
|
|
|
Tube inside area, Ai = |
π*di*L |
|
|
|
Tube outside area, Ao = |
π*do*L |
|
|
Overall heat transfer coefficient, Uo = |
h *di / do |
|
|
|
Answer: Uo = |
|
W / m^2*K |
|
|
|
|
|
|
Cp = |
Cp*1000 |
1000*J/kJ |
|
|
|
Answer: Cp = |
|
J/kg*K |
|
|
|
|
|
|
Disregarding tube fouling, determine the tube length required: |
|
|
|
The tube length required, L = |
ρ*V*(di)^2*Cp*(Tout -Tin) / (4*Uo*do*ΔTm) |
|
Answer: L = |
|
m |
|
|
|