Abstract: Energy Efficiency and Distribution Systems

Air and Liquid Distribution Systems

This chapter considers methods and designs to optimize delivery of air and water to condition laboratory spaces. The method used to size the air distribution system is critical. Air distribution system first cost and operating cost are reduced if properly sized ducts and other system components are selected by optimizing fan pressure and duct air velocities. Fan pressure and air velocities are usually chosen based on "engineering experience" rather than on optimization of performance and cost for each building design. Most computerized duct sizing programs available are simply automated versions of methods that do not consider life-cycle cost and energy-efficiency optimization. The engineer wishing to save energy should design an air distribution system with low-velocity, large-diameter, round ductwork including efficient fitting transitions, large-area coils and filters, and active noise attenuation. The laboratory pressure control system contributes to overall safety and energy efficiency by correctly isolating the laboratory from adjacent spaces without wasting conditioned air. Energy-efficient fume hood systems in the modern laboratory must take into account the discharge velocity of supply diffusers near hoods. When noise attenuation devices are necessary, the air distribution system will have a higher pressure-drop, which increases fan size and power consumption. Using quiet fans to minimize noise is the first step in the design process. Even though hot and chilled water pumps are not large consumers of energy, their impact is significant, as much as 5 to 15 percent of HVAC system energy use.

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