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

2. Contents PHM3133 Dosage Design 1 2010/11 2 Introduction Methods of heat transfer

3. Transfer of Heat PHM3133 Dosage Design 1 2010/11 3 Heat transfers from a region of high temperature to a region of low temperature.

4. Examples: Simple Heat Transfer Processes PHM3133 Dosage Design 1 2010/11 4 Cooking Drying clothes under the sun Drying clothes in a dryer Boiling water on stove Boiling water using electric kettle Ironing

5. Examples: Heat Transfer Equipment PHM3133 Dosage Design 1 2010/11 5 At home Air-conditioner Solar water heater Solar water heater Water heater Gas stove Baking oven Microwave oven Industrial Cooling tower Evaporator Heat-exchanger  Liquid-liquid Boiler

6. Heat exchanger PHM3133 Dosage Design 1 2010/11 6

7. Boiler House PHM3133 Dosage Design 1 2010/11 7

8. Examples:Equipment in Pharmaceuticals PHM3133 Dosage Design 1 2010/11 8 Drying  Fluidised bed  Oven  Spray drying Milling  Fluid energy mill

9. Methods of heat transfer PHM3133 Dosage Design 1 2010/11 9 The mechanisms involved are:  Conduction  Contactive  Convection  Radiation

10. Conduction PHM3133 Dosage Design 1 2010/11 10 Solids Transfer of vibrational energy. 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

11. Collisions in Solids PHM3133 Dosage Design 1 2010/11 11 two substances at different temperatures separated by a barrier which is subsequently removed. barrier

12. Transfer of energy in conductive heat transfer PHM3133 Dosage Design 1 2010/11 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.

13. Thermal conductivity PHM3133 Dosage Design 1 2010/11 13 Different materials transfer heat by conduction at different rates this is measured by the material's thermal conductivity.

14. What is the thermal conductivity? PHM3133 Dosage Design 1 2010/11 14 Suppose we place a material in between two reservoirs at different temperatures

15. Conductors and insulators PHM3133 Dosage Design 1 2010/11 15 Material with high thermal conductivity is a conductor  E.g. copper Material with low thermal conductivity is an insulator  E.g. concrete

16. 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. PHM3133 Dosage Design 1 2010/11 16

17. Radiation PHM3133 Dosage Design 1 2010/11 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?

18. Example: Heat transfer by radiation PHM3133 Dosage Design 1 2010/11 18 light (visible or not). from the sun to the earth through mostly empty space  cannot occur via convection nor conduction

19. References PHM3133 Dosage Design 1 2010/11 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.