Chapter 8 - Air flow in open-cell foams

Abstract

This chapter is designed to study air flow in open cell foams. Air-flow properties are important when open-cell foams are used as air filters or for sound absorption. Sound consists of pressure waves in air in the frequency range 50 Hz to 10 kHz. Metal open-cell foams, based on Polyurethane (PU) foams, are used for heat exchangers. Airflow measurements are also used to characterize the open-cell content of foams. Silicone surfactants control face opening in PU foams, affecting the air-flow values. This chapter begins with the discussion of air-flow resistance of foams and its modeling in terms of microstructural parameters, such as cell size, the proportion of open-cell faces, and foam density. Cell size strongly influences air-flow properties in contrast with its minor effect on mechanical properties. This chapter describes that the compressive impact resistance of some large open-cell foam products may be influenced by air flow, so the appropriate experimental data needs to be elucidated and the phenomena modeled. The chapter closes by exploring the links between sound absorption in foams and air flow.