Page 386 - Applied Process Design For Chemical And Petrochemical Plants Volume III

66131_Ludwig_CH11A 5/30/2001 4:50 PM Page 343

Refrigeration Systems 343

Figure 11-37. Gas horsepower for two-stage propylene refrigeration system. (Excerpted by special permission: Mehra, Y. R. Chemical Engi-
neering, Jan. 15, 1979. ©McGraw-Hill, Inc., New York. All rights reserved.)

Step 4a. Evaporator volume:
3
Now assume / 4 in. O.D. tubing, 16 ft long.
The load q 1,000 tons 12,000,000 Btu/hr.
4,000
Assume an overall heat transfer coefficient. No. of tubes 1,280
2
U 200 Btu/(hr) (ft )(°F) for brine cooling. 16 0.196
Also assume t 15°F.
The approximate tube bundle diameter for tubes layed out on tri-
q 12,000,000 angular pitch can be calculated from
Therefore: A 4,000 ft 2
t U 15 200 (Text continues on page 348)