Heat exchangers purchase cost

Design an air-cooled heat exchanger to cool water under the following conditions. The design ambient air temperature is 35°C (95°F). The tubes to be used are steel tubes [thermal conductivity = 25 Btu/ (h)(ft2)(°F), or 43 W/(m)(K)] with aluminum fins. The steel tube is 1 in (0.0254 m) outside diameter and 0.834 in (0.0212 m) inside diameter. The inside heat-transfer coefficient and the fouling coefficient hs are each 1000 Btu/(h)(ft2)(°F) [5680 W/(m2)(K)]. Heat-exchanger purchase cost is 22 per square foot for four-tube-row units, 20 per square foot for five-tube-row units, and 18 per square foot for six-tube-row units. 

The costs of materials, for installation include the costs of concrete for the foundations, steel for structural support, piping from and to the other modules, instruments and controllers, lighting and electrical materials, insulation, and paint. Piping costs can be very substantial. Guthrie (1969, 1974) indicates that the cost of piping for a heat exchanger is typically 45.6% of the f.o.b. purchase cost, while the total cost of materials for installation is estimated at 71.4% of the f.o.b. purchase cost, as shown in Table 16.10. Hence, for a 10,000 heat exchanger, the cost of materials for installation is 7,140. 

Published Cost Correla.tions. Purchased cost of an equipment item, ie, fob at seller s site or other base point, is correlated as a function of one or more equipment—size parameters. A size parameter is some elementary measure of the size or capacity, such as the heat-transfer area for a heat exchanger (see HeaT-EXCHANGETECHNOLOGy). Historically the cost—size correlations were graphical log—log plots, but the use of arbitrary equation forms for correlation has become quite common. If cost—size equations are used in computer databases, some limit logic must be included so that the equation is not used outside of the appHcable size range. 

The purchased cost of a shell and tube heat exchanger, carbon shell, stainless steel tubes, heat transfer area 500 m2, was 7600 in January 1998 estimate the cost in January 2006. Use the Process Engineering plant index. 

Figure 6.3a, b. Shell and tube heat exchangers. Time base mid-2004 Purchased cost = (bare cost from figure) x Type factor x Pressure factor... 

It should be noted that a resequence or repipe does not involve zero capital cost, even though no new heat exchanger equipment might be purchased. The pipework modifications for a resequence or repipe might be very expensive. Also, equipment might need to be relocated. Methods for capital cost estimation for retrofit were discussed in Chapter 2. 

Purchased equipment costs for various types of heat exchangers. 

Most other metals in the cooling system are subject to similar corrosive influences, although of reduced intensity, as they will have been selected in part due to their more corrosion-resistant (or noble) properties, albeit at a higher purchasing cost. Although some of these metals and alloys may be quite exotic (and therefore more expensive), they will be used because of a particular suitability for heat exchangers or as components for special types of pumps or valves they may also tend to be inherently noble. 

The basis for estimating the purchase cost of the heat exchangers was the area available for heat transfer. Factors were then applied to allow for different construction materials, operating pressures and tube dimensions. 

Installation costs for the various units are estimated using the data of Ref. CE9 (Table 6 p.169). This data expresses typical installation costs for each unit as a percentage of purchase price. Compressors are rated at 30% of purchase cost heat exchangers at 35% towers/, columns at 60% metal tanks at 30%. Those items not included are estimated as having an installation cost at 30% of the purchase cost. 

Employing the correlations presented in Ref. CE9 to estimate the purchase cost based upon heat-exchange area ... 

Plot the 1985 purchased cost of the shell-and-tube heat exchanger outlined in the previous problem as a function of the surface area from 100 to 2000 ft2. Note that the purchased-cost-capacity exponent is not constant over the range of surface area requested. 

Figure 15-12 presents average cost data for heat exchanger tubing constructed of steel. The average purchased cost of complete heat exchangers with... 

The total fixed capital investment (FCI) for the entire system taking all costs for heat-exchanger equipment, pumps, piping, installation, etc., into account is equal to the initial cost of the catalyst solution plus 4.5 times the purchased cost of the reactor. Assume none of the unreacted materials can be recovered. 

Typical face velocities (FVs) used for design are also tabulated in Table 7.6. These values result in air-cooled heat exchangers that approach an optimum cost, taking into account the purchase cost, the cost for installation, and the cost of power to drive the fans. Each designer may wish to establish his or her own values of typical design face velocities these should not vary greatly from those tabulated. 

In the factor methods for cost estimating, first calculate the purchased or delivered cost of all major equipment, for example, distillation columns, reactors, pumps, heat exchangers, etc. Then multiply the total equipment cost by factors to estimate the various other components of the depreciable capital cost given in Equation 2.2, such as piping and electrical wiring. Thus, we arrive at the cost of installing all the equipment and supplying all the services needed to produce an operational process. 

Included among the factors is the effectiveness index. It is a measure of the cost-effectiveness of an exchanger, and is defined as /= overall heat-transfer coefficient/heat-ex-changer cost. With coefficients expressed in Biu/(h) ft )CF), and purchase costs in /ft, Elis given as Btu/(h) °F)( ). Such indices are shown in the table, and these are averages for a variety of heat-exchanger sizes (250, 500, 750 and 1,000 ft )... 

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