Therefore, care must be taken to choose the test temperature which best typifies the service condition. Unless the stress on a pressurized component is to be duplicated, total system pressure is of less importance in laboratory simulations of process environments. In most cases, partial pressure of corrosive gases in the system must be duplicated to achieve the required solubilities of these constituents in solution. However, total pressure can affect phase behavior and may also be a driving force in a chemical reaction or diffusion of the corrosive media into a material. In these cases, it is more important to simulate the total pressure of the service environment so that the proper relationships between liquids and gases or permeation of corrosive media can be obtained.
Mass transfer is often the most difficult parameter to simulate in the laboratory.
Size effects have a dramatic influence on mass-transfer conditions. Much of the current technology for laboratory test design to simulate systems involving mass transfer includes methodologies such as impinging jets, rotating cylinders, ultrasonic cavitation electrodes, and flow loops.