Definition of Transport Phenomena

Daniela Nataly Díaz Zepeda
MC in Biomedical Engineering and Physics

The term transport phenomena refers mainly to three types of processes: momentum transport, energy transport and mass transport. These three major fields of study involve, respectively, fluid dynamics, heat transfer and mass transfer of different chemical species.

The study of transport phenomena is fundamental for the development of different scientific fields, including physics, chemistry, mechanical engineering and chemical engineering, among many others. It is worth mentioning that, fundamentally, all transport phenomena base their behavior on the laws of conservation (matter and energy).

momentum transport

Momentum transport refers to materials in motion, specifically, fluids. Fluid dynamics is responsible for the study of these processes, which deals with the principles under which the process occurs. movement of fluids under different conditions such as flow through pipes, turbulence, open channels, among others. The study of momentum transfer is useful in applications such as aerodynamic and land vehicle design, even in biological systems such as blood flow in the human body.

energy transport

On the other hand, heat transfer is a fundamental process that describes how energy in the form of heat passes from one place to another. This occurs under three main mechanisms, which are conduction, convection and radiation. Conduction is the transfer of heat in one solid in contact with another, convection is the transfer of heat through of fluid movement and radiation is the transfer of heat by means of electromagnetic waves, such as microwaves and infrared.

Understanding how the heat transfer phenomenon occurs is essential in applications such as the design of heat exchangers, room heating or cooling devices, kitchen appliances, among others. many others.

Mass transfer

Mass transfer refers to the mechanism by which matter passes from one location to another within a certain system, either by a phase change or by chemical processes involved. Here comes the diffusion of compounds or other chemical species, such as molecules or ions, the description of reactions that occur in certain processes, such as physiological ones, among others. Mass transfer plays an important role in unit operations, which are applied in industrial processes, such as absorption, extraction, drying and distillation.

Transport phenomena can be studied under the magnifying glass of three different levels, referring to different scales: macroscopic, microscopic and molecular. Starting at the macroscopic level, in which equations known as balance are proposed, which describe how the momentum, energy and mass in a system are affected under a certain change. Said change can be the introduction or removal of some of the elements, due to inputs of matter, energy or external currents. These balances focus on the differences from an initial state to a point in time where the condition occurred in the process, leaving aside the understanding of all the details of the system. The study of transport phenomena at a macroscopic level helps us understand a problem from a global perspective, and in certain applications, such as engineering, it is all that is needed.

Next is the microscopic level, under which small regions within the system are examined, Equations describing a change also apply here, but only within the small region of study. The objective of a study at the microscopic level is to obtain information, more detailed than at the macroscopic level, such as temperature, pressure and concentration profiles, which can be extrapolated to other regions to obtain a more detailed x-ray of the study. Finally, the molecular level seeks to fundamentally understand transport phenomena, that is That is, understanding the mechanisms of mass, momentum and energy in terms of forces and structure molecular. These types of studies are adopted by scientific branches such as theoretical physics, physical chemistry, and very occasionally engineering.

Application examples

Some applications of the study of transport phenomena include the resolution of industrial, biological, agriculture and meteorology, then let us remember that all these processes are governed by the laws of conservation of matter and energy. Engineers and scientists dedicated to this field of study use equations to model these phenomena and predict its behavior under different conditions, in addition to looking for ways to optimize the processes governed for them. More specifically, industrial processes such as distillation, drying of grains and wood, fermentation processes for the production of foods and beverages, water treatment, mining, oil refining, all of them were developed and continue to be perfected thanks to the application of the phenomena of transport.