A. Introduction

One of the basic problems in arriving at the cost of a particular project is to arrive at a reasonably accurate price for the heat exchangers involved. Quite often the information available is sketchy and limited to the surface area and tube length in the case of a shell-and-tube heat exchanger. With these parameters it is possible to arrive at a reasonable first estimate of the cost, either on the basis of cost per ton (usually used for vessel and structural steel work) or on the basis of cost per unit of surface area. There are other parameters that can be used to arrive at a more accurate cost estimate, as discussed below.

B. Determination of shell size

If only the surface area is given, the next step is to arrive at the shell diameter that can be used. Table 1 lists shell diameter against the surface area per unit length of shell (m²/m) for 19-mm (3/4-in) OD tubes with a 25.4-mm (1-in) square pitch. Surface area per unit length is given for four of the basic TEMA configurations (see Section G). Above a 508-mm (20-in) shell OD there is a "breakpoint" between pipe shells and shell rolled from plate. This breakpoint arises from manufacturing considerations and varies from country to county. Table 1 also lists correction factors to the surface area for other pitch configurations and tube diameters.