Page 216 - Design for Environment A Guide to Sustainable Product Development

Analysis Methods for Design Decisions 193

Heat Transfer Process Design
This second DFE example applies similar concepts to the design of a
process in a manufacturing facility. A company is reviewing options
for replacing heat transfer fluids that are used in injection molding
applications. Currently, heat transfer fluids are purchased on the
basis of the requirements of the application, product availability,
and initial purchase cost. Worker concerns about adverse health
impacts, recent product price increases, and the availability of sev-
eral new products have motivated the company to reevaluate the
heat transfer fluids used in the manufacturing process. In selecting
a heat transfer fluid, the company has the following goals:
• Minimize the total life-cycle costs,
• Decrease the volume of heat transfer fluids that are inciner-
ated or landfilled, and
• Reduce adverse impacts to worker health.

Heat transfer fluids typically have different purchase costs, dis-
posal costs, and useful lives. In addition, because of fundamental
differences in their physical and chemical characteristics, the operat-
ing and maintenance costs (e.g., inspection costs, system repair costs,
and worker training costs) can also differ.
Table 9.5 illustrates an analysis of several alternative types of
fluid. While perfluorinated fluids are more costly initially, they have
a longer expected lifetime (35 years), lower operating and mainte-
nance costs, and much lower disposal costs (since they are recycla-
ble) than other alternatives. These lower costs more than make up
for the initial capital costs incurred to modify the heat exchangers.
This life-cycle cost perspective shows that, on an annualized basis,
perfluorinated fluids have significantly lower costs.
There are environmental benefits as well. Because perfluori-
nated fluids can be recycled, their use virtually eliminates the need
to landfill or incinerate spent material. Furthermore, they are inert,

Capital and Operating & Annual
Acquisition Maintenance Disposal Life-Cycle Cost
Costs Costs Costs Costs (NPV)

Mineral Oil $275 $4,531 $130 $4,936 $3,705
Aromatic $750 $6,023 $113 $6,886 $2,769
Hydrocarbon
Perfluorinated $18,500 $4,344 $1 $22,845 $2,369
Fluid

TABLE 9.5 Comparison of Alternative Heat Transfer Fluids