Interfacial transport phenomena in engineering flows

Mechanical Engineering

About this course

Multiphase flows are of prime importance in the automotive branch (injection of gasoline), in power engineering (steam atemperation), in agriculture (insecticides), in inkjet printers and in many fysiological transport processes in the food industry. Break-up of liquid filaments and coalescence of drops are essential processes in sprays and the development of structures in mixing and dispersion of fluids. Transport of mass across a fluid-gas interface if important in atmosphere and climate (rain), in-house climate control (humidity and temperature control), steam generation and heat recovery in power plants, as well as in diffusion induced and flow induced phase separation. The role of surfactants is of eminent importance for the so-called tears of wine, in polymer and food production and in drug-delivery systems. Diffusion in the surrounding gas phase with inert components prevents sudden disappearing of the oceans, hampers heat transfer with condensation and eases combustion. In this course the conservation laws valid on an interface between a gas mixture and a fluid will be derived. Focus is on systematic approach and solution methods and on the capability to solve the above mentioned processes and related phenomena that occur during transport of heat and mass across an interface. The conservation laws will be combined with principles of non-equilibrium thermodynamics to describe an interface thermodynamically via an additional stress tensor in the Navier-Stokes equations. Focus will be on fluid-fluid and fluid-solid systems of several components. Simple engineering models for important applications will be based on fundamental descriptions. Examples of these applications are separation of phases, surface tension, diffusion and Marangoni convection, as well as the coupling of evaporation and chemistry in the gas phase. Various topics will be considered in detail during lectures:

• Droplet evaporation in a gas mixture, including analytical and numerical solutions, the diameter squared law during evaporation, comparison with experimental results.

• Gas-liquid flows mass transfer and reaction.

• Mass and Heat transfer in presence of chemical reaction in gas-solid systems.

Expected learning outcomes

Apprehension and capacity to solve problems on thermodynamic processes concerning dynamic interfaces are the main educational targets. In addition students should become familiar with current engineering methods to solve heat and mass transport across a deforming interface.