Cost Evaluation of Industrial Ventilation System Designs

Abstract

This paper describes a method for determining and comparing the costs of various design choices at each step in the design of an industrial ventilation system. The technique applies to the design of new systems and the alteration of existing systems. Cost evaluations are made in terms of the sum of annual energy cost and annualized initial (or capital construction) cost for each option. This method addresses only the system components and presumes that ancillary costs (maintenance, space required, taxes, and factors affecting system life) are similar for each option.

The fundamental variables which contribute to energy cost are separately identified and expressed in terms of dollars per year. These variables are air flow rate; total pressure loss coefficients for entries, ducts, elbows, and junctions; velocity pressure; fan efficiency; motor and drive efficiencies; power costs and hours of operation per year. Tables are provided for estimating 1986 annualized initial costs for ductwork for situations where local specific construction cost data are not available.

Designs having low energy costs frequently have higher initial costs. The sum of the energy and annualized initial costs of specific design options for system components (type of entry, size of duct, etc.) identifies the more cost-efficient component at each step in the design. The overall costs of options for altering or upgrading a system may also be compared. Designers are advised to evaluate both energy and annualized initial costs in selecting the more cost-efficient component or system. Hickey, J.LS.: Cost evaluation of industrial ventilation system designs. Appl. Ind Hyg. 4177-180; 1986.