Page 404 - Handbook of Energy Engineering Calculations
P. 404
shows the action and usual type of heater chosen. Thus,
4. Select the heater for each service
Where the heat-transfer conditions are normal for the type of service met, the
type of heater listed in step 2 can be safely used. When the heat-transfer
conditions are unusual, a special type of heater may be needed. To select such
a heater, study the data in Table 1 and make a tentative selection. Check the
selection by using the methods given in the following calculation procedures
in this section.
Related Calculations. Use Table 1 as a general guide to heat-exchanger
selection in any industry—petroleum, chemical, power, marine, textile,
lumber, etc. Once the general type of heater and its typical U value are
known, compute the required size, using the procedure given later in this
section.
SIZING SHELL-AND-TUBE HEAT EXCHANGERS
What is the required heat-transfer area for a parallel-flow shell-and-tube heat
exchanger used to heat oil if the entering oil temperature is 60°F (15.6°C), the
leaving oil temperature is 120°F (48.9°C), and the heating medium is steam
2
at 200 lb/in (abs) (1378.8 kPa)? There is no subcooling of condensate in the
heat exchanger. The overall coefficient of heat transfer U = 25 Btu/(h · °F ·
2
2
ft ) [141.9 W/(m · °C)]. How much heating steam is required if the oil flow
rate through the heater is 100 gal/min (6.3 L/s), the specific gravity of the oil
2
is 0.9, and the specific heat of the oil is 0.5 Btu/(lb · °F) [2.84 W/(m · °C)]?
Calculation Procedure:
