Kausar Ahmad Kulliyyah of Pharmacy, IIUM Physical Pharmacy 2 1 SIZE EXCLUSION CHROMATOGRAPHY.
KAUSAR AHMAD KULLIYYAH OF PHARMACY Introduction to Heat Transfer 1.
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Transcript of KAUSAR AHMAD KULLIYYAH OF PHARMACY Introduction to Heat Transfer 1.
KAUSAR AHMADKULLIYYAH OF PHARMACY
Introduction to Heat Transfer
http://staff.iiu.edu.my/akausar
1
Contents
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Introduction
Methods of heat transfer
Transfer of Heat
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Heat transfers from
a region of high temperature to
a region of low temperature.
Examples: Simple Heat Transfer Processes
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Cooking
Drying clothes under the sun
Drying clothes in a dryer
Boiling water on stove
Boiling water using electric kettle
Ironing
Examples: Heat Transfer Equipment
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At home
Air-conditioner
Solar water heater
Water heater
Gas stove
Baking oven
Microwave oven
Industrial
Cooling tower
Evaporator
Heat-exchanger
Liquid-liquid
Boiler
Heat exchanger
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Boiler House
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Examples:Equipment in Pharmaceuticals
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Drying Fluidised bed Oven Spray drying
Milling Fluid energy
mill
Methods of heat transfer
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The mechanisms involved are:
Conduction
Contactive
Convection
Radiation
Conduction
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Solids Transfer of vibrational energy.
Occurs via collisions between atoms and molecules in the substance
and the subsequent transfer of kinetic energy.
E.g. cooking on electric stove/hot plate
Collisions in Solids
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two substances at different temperatures separated by a barrier which is subsequently removed.
barrier
Transfer of energy in conductive heat transfer
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When the barrier is removed:fast/hot atoms collide with slow/cold ones. faster atoms lose some speed and slower
ones gain speed; fast ones transfer some of their kinetic
energy to slow ones. This transfer of kinetic energy from the
hot to the cold side is called a flow of heat through conduction.
Thermal conductivity
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Different materials transfer heat by conduction at different rates
this is measured by the material's thermal conductivity.
What is the thermal conductivity?
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Suppose we place a material in between two reservoirs at different temperatures
Conductors and insulators
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Material with high thermal conductivity is a conductor
E.g. copper
Material with low thermal conductivity is an insulator
E.g. concrete
Heat transfer by convection
Applied to most fluids Movement in natural convection
is caused by buoyancy forces, induced by variations in the density of the fluid, due to temperature difference.
E.g. boiling water: Hot water at bottom rises due to
buoyancy Dense cold water at top falls
down A current is created.
In forced convection, a pump is used.
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Radiation
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All bodies at temperature above absolute zero can radiate heat.
Radiation may be transmitted, reflected or absorbed.
The amount absorbed is transformed into heat.
E.g. nuclear power, food irradiation to kill bacteria and lengthen shelf-life
In pharmacy?
Example: Heat transfer by radiation
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light (visible or not).
from the sun to the earth through mostly empty space
cannot occur via convection nor conduction
References
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Aulton, M. E. (1988). Pharmaceutics: The Science of
dosage form design. London: Churchill
Livingstone.
Llachman, L, Lieberman, H. A. and Kanig, J. L.
(1986). The theory and practice of industrial
pharmacy (3rd ed.). Philadelphia: Lea & Febiger.
Note:I got some of the materials from the internet and books but I lost the information on the sources. I acknowledge the authors’ contribution to science. Thank you.