Online Heat Transfer Coefficient Calculator

Heat Transfer Coefficients


The inside film coefficient needed for the thermal calculations may be estimated by several different methods. The API RP530, Appendix C provides the following methods,

For liquid flow with R_e =>10,000,




h_l = 0.023(k/d_i)R_e^0.8*P_r^0.33(m_b/m_w)^0.14

And for vapor flow with R_e =>15,000,




h_v = 0.021(k/d_i)R_e^0.8*P_r^0.4(T_b/T_w)^0.5

Where the Reynolds number is,




R_e = d_i*G/m_b

And the Prandtl number is,




P_r = C_p*m_b/k

Where,

hl = Heat transfer coefficient, liquid phase, Btu/hr-ft2-°F

k = Thermal conductivity, Btu/hr-ft-°F

di = Inside diameter of tube, ft

mb = Absolute viscosity at bulk temperature, lb/ft-hr

mw = Absolute viscosity at wall temperature, lb/ft-hr

hv = Heat transfer coefficient, vapor phase, Btu/hr-ft2-°F

Tb = Bulk temperature of vapor, °R

Tw = Wall Temperature of vapor, °R

G = Mass flow of fluid, lb/hr-ft2

Cp = Heat capacity of fluid at bulk temperature, Btu/lb-°F

For two-phase flow,



h_tp = h_lW_l + h_vW_v

Where,

htp = Heat transfer coefficient, two-phase, Btu/hr-ft2-°F

Wl = Weight fraction of liquid

Wv = Weight fraction of vapor

The following script will allow us to try these formulas out using our browser.

Tube diameter, in:		Mass flow, lb/hr-ft2:
Percent vapor, %:		Bulk Temp., °F:
Liquid Properties		Vapor Properties
Thermal cond., Btu/hr-ft-°F:		Thermal cond., Btu/hr-ft-°F:
Visc. bulk, lb/ft-hr:		Visc. bulk, lb/ft-hr:
Spec. Heat, Btu/lb-°F:		Spec. Heat, Btu/lb-°F:
Visc. @ wall, lb/ft-hr:		Temp. @ wall, °F:

h_l Coefficient, Btu/hr-ft²-°F:


h_v Coefficient, Btu/hr-ft²-°F:


h_tp Coefficient, Btu/hr-ft²-°F:


Reynolds number:LiquidVapor

It should be stressed at this time, that there are many ways to calculate the inside heat transfer coefficient, and a lot of care should be taken in the procedure selected for use in heater design. Other methods, such as HTRI, Maxwell, Dittus-Boelzer, or others may be more appropriate for a particular heater design.