Page 314 - Applied Process Design For Chemical And Petrochemical Plants Volume III

66131_Ludwig_CH10H-J 5/30/2001 4:47 PM Page 273

Heat Transfer 273

Nomenclature BC tube length for sensible heating, ft, Figure
10-110.
2
A total exchanger bare tube heat transfer, ft ; BCF bundle correction factor, Equation 10-144.
or, net external surface area of tubes b fin height, ft.
2
exposed to fluid heat transfer, ft ; or, area C capacity constant for tubes, Table 10-3,
2
available for heat transfer, ft (for conduc- (except ratio in caloric temperature).
tion heat transfer, A is a cross-sectional area, C or c clearance between tubes, measured along
taken normally in the direction of heat flow, the tube pitch, in.; Figure 10-56.
2
ft ). CD tube length for vaporization, ft, Figure 10-110.
A area of heat transfer, from emitting to or c or c p heat capacity or specific heat at constant
2
absorbing radiation source, ft . pressure, Btu/lb(°F); or, heat capacity of
A a area of heat transfer between the insulation condensate, pcu/lb(°C)
2
or bare pipe and air, ft . c b constant in pressure drop equation.
A b net free area of flow through baffle window, C s or c s surface condition constant for Equation
2
ft . 10-162.
A c net free area of cross-flow between baffles CMTD corrected mean temperature difference
2
on shell side of tube bundle, ft . (°F)(LMTD), °F.
A cc , A cp , A o , A p special symbols for insulation equation. C N turbulence correction factor.
A g geometric mean free flow area on shell side D I.D. of tube, ft; also used as D 1 (inside), D 2
2
of tube bundle, ft . (outside); or, impeller diameter, ft; or, pipe
2
A i inside area of unit length of tube, ft /ft (or, O.D., ft; or, O.D. of insulated or bare pipe,
where indicated). whichever is being studied.
A n net effective outside tube surface area for D tube diameter, side where boiling takes
2
plain or bare tubes, ft . place, ft, Equation 10-165.
A nf net effective outside tube surface area for D a diameter of agitator, ft.
2
finned tubes, ft . D b tube bundle diameter, ft.
2
A o outside area of unit length of tube, ft ; or, D e or D es equivalent tube outside diameter, ft; or,
required effective outside heat transfer sur- equivalent inside tube diameter, in.; or,
face area based on net exposed tube area, equivalent diameter of annulus (D 1 O.D.
2
ft . of inner tube, ft; D 2 inside diameter of
3
ACFM actual ft per min of air at fan intake. outer pipe, ft).
a cross-section area of tube for flow through D e equivalent diameter of tube bundle in shell,
2
inside, ft . May be used for an individual for pressure drop, ft.
tube or a group of tubes, depending on the D eg an equivalent diameter of a finned tube for
intended use; or, bulk fluid outside insu- calculation of condensing coefficient, ft.
2
3
lated pipe; or, interfacial area ft /ft ; or, heat D H diameter of helix of coil, in.
transfer surface area per unit length of tube, D i I.D. of tube, ft; or, insulation O.D., ft.
2
ft /ft/(air cooler). D j diameter of inside of vessel, ft.
1/4
a constant in Bromley equation, (in./ft) . D H nozzle size, diameter, in.
a exponent. D o O.D. of tube, ft; or, outside diameter of
2
a i cross-sectional flow area per tube, in. ; or, insulation, in.
2
cross-sectional flow area, inlet feed pipe, ft . D o or D t tube O.D., in.
a o tube outside heat transfer surface/ft, ft. D s shell I.D., in.
2
a p flow area per pass inside tubes, ft . D s shell I.D., ft.
2
a s flow area across tube bundle, ft (cross-flow D t see D o ; or, O.D. of tracer, in.
area). d e or d s shell-side equivalent tube diameter, in.
2
a t surface area of tube outside, ft /ft. d e equivalent diameter, finned, in.
a x projected area of cross-section of finned d i or d it I.D. of tube, in.
tube at the fin, in. 2 d film thickness, ft.
B overall resistance to heat transfer less d o tube O.D., in. (or ft, as specified).
shell-side resistance (for finned tube d r root diameter of finned tube, in.
2
calculations), 1/Btu (hr)(ft )(°F). d s shell-side I.D., in.
B or B s baffle pitch or spacing, in. d t tube O.D., ft.
2
B s baffle spacing at ends of bundle, in. E superficial liquid entrainment, lb/hr/ft ; or,
B ca baffle cut areas, expressed as fraction, heat transfer effectiveness.
representing opening as percent of shell E B enthalpy of bottoms, Btu/lb.
cross-section area. E D enthalpy of overhead product removed
B L coefficient in Levy boiling coefficient equa- from column, Btu/lb.
tion, Figure 10-99. E F enthalpy of feed, Btu/lb.