Heat Transfer - Pharmaceutical Engineering B. Pharm Third Semester PDF Notes

 Heat Transfer

Intended Learning Outcomes

At the end of this lecture student will be able to:

• Define heat and heat transfer

• Explain the different mechanisms of heat transfer

• Recall the applications of heat transfer

• State Fourier’s law with applications

• Derive equation for compound resistance for conduction

• Differentiate between natural and forced convection

• State the differences between black body and grey body

• State Stefan Boltzamann law for radiation

• Contrast between heat exchangers and heat interchangers

• Classify heaters according to the mode of heat transfer

• Describe the construction and working of Tubular heater

• Explain the working of multipass heater

• Draw and describe the working of few heat interchangers

Summary

• Summary Heat is a form of energy. According to the principle of thermodynamics whenever a physical or chemical transformation occurs heat flow into or leaves the system

• Three modes of heat transfer are conduction, convection and radiation

• Fourier’s law states that the rate of heat flow through a uniform material is proportional to the area and the temperature drop and inversely proportional to the length of the path of flow

• The coefficient of thermal conductivity depends upon the material with which the body is made and upon its temperature

• Natural convection is the Mixing of fluid may be accomplished by the currents set up, when body of fluid is hated

• Forced convection is the mixing of fluid may be obtained by the use of a stirrer of agitator or pumping the fluid for recirculation

• A black body is defined as a body that radiates maximum possible amount of energy at a given temperature.

• A grey body is defined as that body whose absorptive is constant at all wavelengths of radiation, at a given temperature

• Stefan-Boltzmann law gives the total amount of radiation emitted by a black body

• Heat interchangers are the devices used for transferring heat from one liquid to another or from one gas to another gas through a metal wall

• Heat exchangers are the devices used for transferring heat from one fluid (hot gas or steam) to another fluid (liquid) through a metal wall

• Shell-and-tube heater is the simplest form of a tubular heater. It is a single-pass tubular heater

• In a multi-pass heater, the velocity of fluid can be increased. As a result, heat transfer coefficient also increases

• Heat interchangers are the devices used for transferring heat from one liquid to another or from one gas to another gas through a metal wall. In heat interchangers, the heating medium is a hot liquid

• In a liquid-to-liquid heat interchanger, the fluid to be heated is passed only once through the tubes before it gets discharged, i.e. single pass. The heat transfer in this case is not efficient. When few tubes per pass is desirable double pipe heat interchanger is employed.

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