411-305 Heat Transfer

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Objectives:

Upon completion of this unit the students will:

• be familiar with the concepts of heat transfer in flowing fluids, boiling and condensing fluids, and radiation;

• be able to assess quantitatively the performance of industrial heat transfer equipment.

Content:

Convection: Use of heat transfer correlations to predict coefficients. Consideration of entrance length, including range of validity. Laminar and turbulent flows. Concept of an overall heat transfer coefficient, fouling factors. Determination of the area required for a given heat duty.

Basics of condensation: filmwise and dropwise; mass transfer aspects; presence of non-condensible gases. Horizontal and vertical condensers; sub-cooling. Multicomponent condensation.

Boiling: Vapour/liquid equilibrium in pure component system. h versus Δ T relationship; peak flux, critical Δ T. Sub-cooled boiling.

Free convection: Discussion and application of Grashof Number and other dimensionless groups.

Introduction to heat exchange network analysis.

Evaporation: Various types and their advantages and disadvantages (forced circulation, film types). Multiple and single effects; backward and forward feed; boiling point elevation; apparent and actual heat transfer coefficients; thermal and mechanical recompression. Evaporator energy balance.

Radiation: Basic principles of radiation. Shape factors (viewfactors). Radiation between grey surfaces - the network approach. Applications of networks for various situations, e. g. two or more surfaces, thermocouples and shields, gases which radiate, insulated surfaces.

Assessment: