Page 316 - Applied Process Design For Chemical And Petrochemical Plants Volume III

66131_Ludwig_CH10H-J 5/30/2001 4:47 PM Page 275

Heat Transfer 275

h c heat transfer coefficient for outside of coil, K 1 , K 2 , K 3, K 4 constants in tube count equation.
2
Btu/(hr)(ft )(°F); or, average condensing K or k thermal conductivity of material of tube, or
2
2
coefficient on outside of tube, Btu/(hr)(ft ) other, wall, Btu/(hr)(ft )(°F/in.).
(°F); or, U t average of horizontal and ver- k k 1 thermal conductivity of liquid, Btu/
tical transfer film coefficients in still air; or, (hr)(°F/ft); or, thermal conductivity of insu-
2
convection heat transfer film coefficient, lation, Btu/(hr)(ft )(°F/ft); or, when speci-
2
2
Btu/(hr)(ft )(°F). fied, Btu/(hr)(ft )°F/(in.).
h cm average value of condensing film coeffi- k or k a thermal conductivity of fluid at average of
cient, for vertical rows of horizontal tube, temperatures, t 1 and t 2 , Btu/(hr)(°F/ft); or,
2
2
Btu/(hr)(ft )(°F). Btu/(hr)(ft )(°F/ft).
h fg latent heat of vaporization or evaporation, k f thermal conductivity at film temperature,
2
Btu/lb. Btu/(hr)(ft )(°F/ft).
h i film coefficient of fluid on inside of tube, k g gas phase mass transfer coefficient, lb
2
2
Btu/(hr)(ft )(°F). mol/(hr)(ft )(atm).
2
h io , h io inside film coefficient referred to outside of k d diffusivity , ft /hr.
tube surface (plus including condensing k L thermal conductivity of saturated liquid,
film coefficient clean basis for Colburn- Btu/(hr)(°F/ft).
2
Hougen calculations), Btu/(hr)(ft )(°F). k w thermal conductivity of material of wall,
2
h l h lt nucleate boiling coefficient for an (Btu-ft)/[(hr)(ft )(°F)].
2
isolated tube, Btu/(hr)(ft )(°F). L length of straight tube for heat transfer (or,
h ga volumetric gas phase coefficient, nominal tube length), ft; or, length of path,
3
Btu/(hr)(ft )(°F). ft; or, length or thickness of coil or jacket, ft;
h la liquid phase heat transfer coefficient, or, superficial liquid mass velocity,
2
2
Btu/(hr)(ft )(°F). lb/(hr)(ft ); or, equivalent length of pipe, ft;
h M effective heat transfer film coefficient, or, thickness of insulation, in.
2
Btu/(hr)(ft )(°F). L c thickness, ft.
h m film coefficient evaluated at length mean t L e net effective tube length, ft.
2
for vertical tube, Btu/(hr)(ft )(°F). L f finned length of each tube, ft.
h Nu condensing film coefficient by Nusselt L o length of shell; or, length of one tube pass, ft.
2
equation, Btu/(hr)(ft )(°F). L t total length of tubing required, ft.
h o dry gas coefficient on shell side for partial L w thickness of tube wall, in.; or, ft as consistent
2
condensers, Btu/(hr)(ft )(°F); or, (for bare with other units.
or plain tubes) film coefficient outside of L v weighted average latent heat of reboiler
2
tube in bundle, Btu/(hr)(ft )(°F); or, (for fin vapor, Btu/lb.
tubes) outside film coefficient corrected to LMTD log mean temperature difference, °F.
2
base of fin, Btu/(hr)(ft of outside area)(°F). l length of each individual tube, ft; or, fin
h r radiation heat transfer film coefficient, height, in.
2
Btu/(hr)(ft )(°F). l v latent heat of vaporization, Btu/lb.
h s film coefficient for boiling fluid, Gilmour M net free distance (sum) of space between
2
equation, Equation 10-165, Btu/(hr)(ft ) tubes from wall to wall at center of shell
(°F); or, subcooling film coefficient, circle, in.; or, molecular weight.
pcu/(hr)(ft)(°F). M a average molecular weight.
h st theoretical boiling film coefficient for single M v average molecular weight of vapor.
2
tubes, Btu/(hr)(ft )(°F). m exponent for baffle tray columns.
htc a air-side heat transfer coefficient, N or N t total number of tubes in bundle.
2
Btu/(hr)(ft )(°F). N number of tube holes per tubesheet; or,
hct c tube-side heat transfer coefficient, number of fins per in. on tube; or, agitator
2
Btu/(hr)(ft )(°F). or impeller speed, revolutions/hr; or, num-
J Colburn factor. ber of tubes in bundle; or, number
J 4 Colburn factor for equation proposed by tubes/row in direction of air flow.
Pierce. N a average number of tubes in a row in circular
j H factor in heat transfer equations, dimension- shell of multitube condenser.
less. N c number of baffles.
K thermal conductivity of fluid, N nv number of holes in vertical center row of
Btu/(hr)(ft)(°F). (Used by Permission: bundle.
Brown Fintube Company.) N t number of tubes used, for condensing.
2
K g diffusion coefficient, lb mol/(hr)(ft )(atm). N v number of rows of tubes in a vertical tier.
K L thermal conductivity of saturated liquid, N vc number of rows of tubes in a vertical tier at
Btu/(hr)(°F/hr). centerline of exchanger.