ABSTRACT
As engineers or scientists, we design processes to operate at a steady-state because such systems are efficient, continuous, easy to control, easy to operate, easy to analyze, and satisfy an innate desire in our species to resist change in our environment. More often than not, it will be your job as an engineer or scientist to decide when a system can be analyzed as a steady-state operation and when fluctuations are fast enough to require a transient analysis. As an example, suppose we are able to measure the momentum of our system at any time. If the system were not operating at a steady-state, we would notice that our momentum measurements would change over time. We refer to these changes as accumulation. Although we tend to view accumulation as an increasing process, in the jargon of transport phenomena, accumulation can represent both an increase or decrease in our transport quantity.
