Features Related to Thermal Design
DOI 10.1615/hedhme.a.000416
4.2.5 Features relating to thermal design
E. A. D. Saunders
A. Tubes
(a) Diameter and thickness
Small-diameter, closely packed tubes provide compact units, but the tubes may be difficult to clean both inside and outside; large-diameter, widely spaced tubes provide less compact units, but cleaning problems are reduced. The usual outside tube diameter range for petroleum and petrochemical applications is 15 mm to 32 mm, with 19 mm and 25 mm being the most common.
Tube thickness must be checked against internal and external pressure, but the diameters and thicknesses of tubes most commonly used can withstand appreciable pressure. For instance, a steel tube 19 mm in outside diameter, 2.1 mm thick, can withstand internal and external pressures of 16 and 7 MN/m2, respectively. Hence, in many applications tube thicknesses are selected on the basis of cost, corrosion resistance, and standardization rather than pressure. Typical thicknesses are as follows:
| OD | Carbon and low- alloy steels | Stainless steels and copper alloys |
|---|---|---|
| 15.88 mm (1/4 in) | 1.65 mm (16 BWG) | 1.24 mm (18 BWG) |
| 19.05 mm (1/4 in) | 2.11 mm (14 BWG) | 1.65 mm (16 BWG) |
| 25.40 mm (1 in) | 2.77 mm (12 BWG) | 2.11 mm (14 BWG) |
| 31.75 mm (1 1/4 in) | 3.40 mm (10 BWG) | 2.77 mm (12 BWG) |
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