Page 287 - Applied Process Design For Chemical And Petrochemical Plants Volume III

66131_Ludwig_CH10G 5/30/2001 4:40 PM Page 249

Heat Transfer 249

f. Btu/ft 2 -hr-°F.

(t 1 t a ), °F. K, Btu-in./ft -hr-°F.
2

Pipe size, in.
Figure 10-172. Heat loss through process pipes and insulation. (Used by permission: Ganapathy, V. Oil and Gas Journal, Apr. 25,1983, p. 75.
©PennWell Publishing Company. All rights reserved.)

J. Direct-Contact Gas-Liquid Heat Transfer A. Spray Columns

The direct counter-current contact of a hot gas with a cool Data correlated by Fair 242 provides an empirical relation-
immiscible liquid is effectively used in certain hydrocarbon ship for heat transfer:
cracking processes for the quenching of hot gases/vapors.
Sometimes, the liquid used is oil and followed by water
L
0.015G 0.82 0.47
quench, as is typical in ethylene plants cracking naphtha or h ga (10-275)
0.38
other hydrocarbon as feed stock. Z sp
The three primary devices used in this service are (a)
open spray columns, 242, 245 (b) packed columns, 242, 243, 244, 245
where Z sp height of a single zone of spray contact, which most
and (c) tray columns, which are perforated plates, baffle likely is the space between spray nozzles when the
trays, etc. 242, 245, 246, 247, 248, 249 full area coverage is achieved, ft.
Fair 242 reports that the data for mass transfer in spray, G superficial gas mass velocity, lb/(hr) (ft )
2
packed, and tray columns can be used for heat-transfer cal- L superficial liquid mass velocity, lb/(hr) (ft )
2
culations for these columns. The pressure drop in these h ga gas phase volumetric heat transfer coefficient,
types of columns is usually quite low. Btu/(hr) (ft )(°F)
3