Thermochemical Conversion and Heat Transfer Mechanisms Lecture 28

This set of flashcards covers key concepts related to thermochemical conversion processes, various types of reactors, properties of heat transfer mechanisms, and considerations in heat exchanger design.

What is pyrolysis in thermochemical conversion?

A process of chemically decomposing organic materials at elevated temperatures in the absence of oxygen.

Name two types of bio-oil reactors.

Bubbling fluidized bed and Circulating fluidized bed/Transport reactor.

What is a characteristic of a Bubbling Fluidized Bed reactor?

It requires small sizes of biomass and has good heat and mass transfer.

How does a Circulating Fluidized Bed reactor function?

Hot sand is circulated between a combustor and pyrolyzer, with heat supplied from burning char.

What is a feature of the Rotating Cone Pyrolyzer?

It has a compact design and does not require a carrier gas.

What disadvantage does the Ablative Pyrolyzer have?

It is complex and does not scale well.

Why is Vacuum Pyrolysis advantageous?

It operates at lower temperatures, avoiding adverse chemical reactions.

What is a drawback of the Auger Reactor?

It requires a hot sand heating and circulating system and has high wear and tear.

What are Microwave Pyrolyzers known for?

They are rapid, efficient, controllable, and provide uniform heating at the molecular level.

Describe the structure of Entrained flow reactors (gasifiers).

They operate at high temperatures and pressures with powdered fuel entrained in the gasifying medium.

What principle does conduction heat transfer rely on?

Energy transfer from high-temperature regions to low-temperature regions within a body.

How does convection heat transfer differ from conduction?

Convection involves the movement of air or fluid that carries heat away, whereas conduction does not involve fluid motion.

What is the mechanism of radiation heat transfer?

Heat is transferred through regions where a perfect vacuum exists by electromagnetic radiation.

What are essential phase change processes in heat transfer?

Condensation and boiling phenomena.

What is the log mean temperature difference (LMTD)?

It is the suitable mean temperature difference across a heat exchanger used in heat transfer calculations.