Gas Flow

Summary

In this chapter, the authors discuss gas flow at reduced pressures. The mathematical descriptions of gas flow are complex, and the nature of their solutions depends on pressure, temperature, flow rate, gas properties, duct geometry, and surface properties. The authors begin by defining flow regimes and introducing the concepts of throughput, speed, conductance, and mass flow. They characterize gas throughput and conductance for several types of flow. The authors describe approximation techniques and probabilistic methods for solving complex problems, such as flow in ducts containing entrance and exit orifices, apertures, elbows, diameter changes, and practical shapes. Gas flow regimes are characterized by the nature and by relative quantity of gas flow. Throughput, conductance, speed, mass flow, molar flow, and molecular flow are important concepts that are sometimes confused and warrant discussion. The theory of gas flow in the transition region between molecular and viscous flow is not well developed.