Lecture

Heat Transfer in Microreactors

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In course

ChE-408: Process intensification and green chemistry

The first part of the course (~20%) is devoted to green chemistry and life cycle assessment. The remainder focuses on process intensification (fundamentals, detailed description of a few selected technologies, with a special focus on microreactors). Exa ...

Description

This lecture covers the concept of narrowing Residence Time Distribution (RTD) in segmented flow microreactors by using gas-liquid or liquid-liquid systems to generate fluid-fluid slugs, which travel through the system to suppress axial dispersion. It also discusses the importance of surface wettability in RTD, the mechanisms to improve RTD in microreactors, and the heat transfer in microchannels for homogeneous and segmented flows. The instructor explains the reaction classes, heat production, and heat management strategies for different types of reactions, emphasizing the critical role of heat evacuation and hot spot reduction in microreactors.

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Instructor

Harvey Randall

Official source

Related concepts (25)

Heat transfer

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer.

Heat

In thermodynamics, heat is the thermal energy transferred between systems due to a temperature difference. In colloquial use, heat sometimes refers to thermal energy itself. An example of formal vs. informal usage may be obtained from the right-hand photo, in which the metal bar is "conducting heat" from its hot end to its cold end, but if the metal bar is considered a thermodynamic system, then the energy flowing within the metal bar is called internal energy, not heat.

Convection (heat transfer)

Convection (or convective heat transfer) is the transfer of heat from one place to another due to the movement of fluid. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined processes of conduction (heat diffusion) and advection (heat transfer by bulk fluid flow). Convection is usually the dominant form of heat transfer in liquids and gases. Note that this definition of convection is only applicable in Heat transfer and thermodynamic contexts.

Heat transfer coefficient

In thermodynamics, the heat transfer coefficient or film coefficient, or film effectiveness, is the proportionality constant between the heat flux and the thermodynamic driving force for the flow of heat (i.e., the temperature difference, ΔT ). It is used in calculating the heat transfer, typically by convection or phase transition between a fluid and a solid. The heat transfer coefficient has SI units in watts per square meter per kelvin (W/m2/K).

Residence time

The residence time of a fluid parcel is the total time that the parcel has spent inside a control volume (e.g.: a chemical reactor, a lake, a human body). The residence time of a set of parcels is quantified in terms of the frequency distribution of the residence time in the set, which is known as residence time distribution (RTD), or in terms of its average, known as mean residence time. Residence time plays an important role in chemistry and especially in environmental science and pharmacology.

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