Page 1 :
Lecture 1.1:, Temperature:, Temperature is a physical quantity that expresses hot and cold., Temperature is measure by help of thermometer., Commonly used scales: Celsius (OC), Fahrenheit (OF), Kelvin (k)., A temperature scale is defined and said to be absolute because it is independent of the characteristics of particular thermometric substances and thermometer mechanisms., Heat:, It is form of energy in transit., Heat Transfer:, The transmission of energy from one region to another as a result of temperature gradient., Mode of Heat Transfer:, It takes place by following three modes;, Conduction:, Conduction is the transfer of heat from one part of substance to another part of the same substance or from one substance to another in physical contact with it, without appreciable displacement of molecules forming the substance., It takes place in solid, liquid and gases., It require material medium for heat transfer., Law governing conduction is Fourier law of heat conduction at steady state., Example: Heating of metal rod, Convection:, Convection is the transfer of heat within a fluid by mixing of one portion of the fluid with another., It takes place in liquid and gases., It requires material medium for heat transfer., Law governing convection is Newton’s Law of Cooling., Type of Convection:, Natural or Free Convection:, Free convection occurs when the fluid circulates by virtue of the natural difference in densities of hot and cold fluids., Example: boiling of water., Force convection:, In Force Convection external work is done to blow or pump the fluid, for heat transfer., Example: Circulation of air with help of fan or AC, Radiation:, In radiation mode, heat transfer takes place through photons present in the electromagnetic waves. The random movement of atoms and molecules in heated substances results in emission of electromagnetic waves which carry the heat to be transferred., It takes place in solid, liquid and gases., It doesn’t require material medium so can take place in vacuum also., Some basic laws that govern Radiation are Planck Radiation Law, Wien law and the Stefan-Boltzmann Law etc., Example: Heat transfer in space between sun and earth by through radiation, heat transfer through furnace wall through radiation.