This course presents an elementary treatment of the principles of conduction, convection and radiation heat transfers. Steady state conduction is studied from analytical and numerical view points, while most of unsteady state conduction for cooling/heating is studied by using Heisler charts. To predict the convection heat transfer coefficient, conduction through fluid layer near the heating surface mechanism is treated prior to the empirical and graphical relations. Radiation is treated especially to compare the heat exchange between back and non blackbodies. Only the popular heat exchangers are studied their performance, by LMTD or effectiveness-NTU method. The heat transfer with phase changes are studied to predict condensation and vaporization coeficients and apply it on suitable equipment.