Simultaneous Heat and Mass Transfer (advanced transport phenomena)
Simultaneous Heat and Mass
Transfer (Advanced transport phenomena)
Heat transfer and mass transfer are kinetic processes that may occur and be studied separately or jointly.
Studying them apart is simpler, but both processes are modelled by similar mathematical equations in the case of diffusion and convection (there is no mass-transfer similarity to heat radiation), and it is thus more efficient to consider them jointly. Besides, heat and mass transfer must be jointly considered in some cases like evaporative cooling.
The usual way to make the best of both approaches is to first consider heat transfer without mass transfer, and present at a later stage a briefing of similarities and differences between heat transfer and mass transfer, with some specific examples of mass transfer applications. There are complex problems where heat and mass transfer processes are combined with chemical reactions, as in combustion.
But many times the chemical process is so fast or so slow that it can be decoupled and considered apart.
Example: Important diffusion-controlled combustion problems of gas-fuel jets, and condensed fuels (drops and particles), which are covered under combustion kinetics.
In process operations where material is transferred between phases, usually between liquid and vapor phases, the transport process may be described in terms of heat transfer and mass transfer. When both expressions are developed and handled simultaneously, the resulting equations show that heat and mass transfer affect each other. Equations applied to humidification and dehumidification processes are presented. These expressions could equally well be applied to drying, evaporation, or crystallization processes. The conceptual design of counterflow cooling towers or dehumidification towers is discussed, as are the mechanical and operating features of these columns, costs, and environmental impacts. In all of these processes the air–water system is usually of concern. Thus the properties of moist air are developed and displayed on psychrometric charts.
In distillation columns, simultaneous mass and heat transfer occur at each tray. Vapor and liquid are at equilibrium at each tray.
Hot vapor flowing in upward direction looses heat to liquid on each tray and because of this heat transfer there will be mass transfer of key component from liquid to vapor and vice versa heavy component will condense out from vapor and get into liquid due to cooling effect.
Examples: • Distillation • Absorption • Cooling • Air-conditioning • Etc.
What is Engineering? what is Chemical Engineering?
Transport phenomena in porous media
Seperation Process - Condensation
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