Introduction to Heat Transfer 1 KAUSAR AHMAD KULLIYYAH

Introduction to Heat Transfer 1 KAUSAR AHMAD KULLIYYAH OF PHARMACY http: //staff. iiu. edu. my/akausar

Contents 2 Introduction Methods of heat transfer PHM 3133 Dosage Design 1 2010/11

Transfer of Heat 3 Heat transfers from a region of high temperature to a region of low temperature. PHM 3133 Dosage Design 1 2010/11

Examples: Simple Heat Transfer Processes 4 Cooking Drying clothes under the sun Drying clothes in a dryer Boiling water on stove Boiling water using electric kettle Ironing PHM 3133 Dosage Design 1 2010/11

Examples: Heat Transfer Equipment 5 At home Industrial �Air-conditioner Cooling tower �Solar water heater Evaporator �Water heater �Gas stove �Baking oven �Microwave oven PHM 3133 Dosage Design 1 2010/11 Heat-exchanger Liquid-liquid Boiler

Heat exchanger 6 PHM 3133 Dosage Design 1 2010/11

Boiler House 7 PHM 3133 Dosage Design 1 2010/11

Examples: Equipment in Pharmaceuticals 8 Drying Fluidised bed Oven Spray drying Milling Fluid energy mill PHM 3133 Dosage Design 1 2010/11

Methods of heat transfer 9 The mechanisms involved are: Conduction Contactive Convection Radiation PHM 3133 Dosage Design 1 2010/11

Conduction 10 �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 PHM 3133 Dosage Design 1 2010/11

Collisions in Solids 11 two substances at different temperatures separated by a barrier which is subsequently removed. barrier PHM 3133 Dosage Design 1 2010/11

Transfer of energy in conductive heat transfer 12 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. PHM 3133 Dosage Design 1 2010/11

Thermal conductivity 13 Different materials transfer heat by conduction at different rates this is measured by the material's thermal conductivity. PHM 3133 Dosage Design 1 2010/11

What is thermal conductivity? 14 Suppose we place a material in between two reservoirs at different temperatures PHM 3133 Dosage Design 1 2010/11

Conductors and insulators 15 Material with high thermal conductivity is a conductor E. g. copper Material with low thermal conductivity is an insulator E. g. concrete PHM 3133 Dosage Design 1 2010/11

Heat transfer by convection 16 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. PHM 3133 Dosage Design 1 2010/11

Radiation 17 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? PHM 3133 Dosage Design 1 2010/11

Example: Heat transfer by radiation 18 light (visible or not). from the sun to the earth through mostly empty space cannot occur via convection nor conduction PHM 3133 Dosage Design 1 2010/11

References 19 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 (3 rd 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. PHM 3133 Dosage Design 1 2010/11