# Essays on Energy Transfer And Thermodynamics Article

Where m is the mass and V is the velocityPotential Energy, PE= mgzWhere m is mass, g is acceleration due to gravity and z is the datum. Work, W=Wext(external work)+Wflow(flow work)Wflow= m (p/r)Where m is mass, p is pressure and r is the densityChange in Heat content, dQ = dE + dWQ4. Formula for conversion of temperature scale is: TK K = (TK - 273.15) °C = [1.80 * (TK - 273.15) + 32] °F = 1.80 TK °RankineNormal body temperature is 98.6°F = 37°C = 558 °RankineAbsolute zero = 0 K = -459.4°FTemperature rises by 30°C = Temperature rise 30 K Temperature rise by 60°F = Temperature rise by 33.33°C = Temperature rise by 33.33K = Temperature rise by 59.4 °RankineQ5.

There are basically there mechanisms of heat transfer. They are namely, Conduction, convection and radiation. Conduction: It is a mode of direct heat flow through any matter and it is a result of actual physical contact between two parts of a same body or two different bodies. Heat is always conducted from hot to cold part or body but is never the other way round.

Heat flows through the shortest and easiest route. Example is heating of a metallic container kept on heater. Convection: It is a mode of heat transfer in gases and liquids which is caused by the actual flow of the material itself i. e. the movement of the matter. Generally the movement of the matter is turbulently upward after getting heated though with a component of sideways motion also. Example is boiling of water. Radiation: This is a mode of heat transfer in vacuum or in space without and help of matter.

The transfer takes place through infrared or electromagnetic waves. Example is the heat og sun coming to earth. Q6. Heat transfer is often classified as being steady or transient (also called unsteady). The term steady implies no change with time at any point within the medium, while transient implies variation with time or time dependence. Therefore, the temperature or heat flux remains unchanged with time during steady heat transfer through a medium at any location, although both quantities may vary from one location to another. During transient heat transfer process, the temperature normally varies with time but not with position.

Most heat transfer problem encountered in practice is transient in nature, but they are usually analyses under some presumed steady condition since they are easy to analyse. Transient heat conduction Steady heat conductionQ7. In natural convection, the driving force for heat transfer to take place is buoyancy. This buoyancy is because of difference in fluid density because of acceleration in the system. The fluid around the source of heat gets less dense after being heated and rises above. This gives way to cooler and denser fluid to go down near the source.

This process keeps on continuing and the heating takes place and it is said that convection current is formed. Forced convection, on the other hand, takes place when forced draft of the fluid through external means like mechanical pumps or fans is used to artificially form the convection current.