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Heat & Mass Transfer: A Tutorial

Heat and mass transfer is a sub-discipline of physics that has broad and varied application in the design of residential and commercial buildings, industrial processes, design of electronic devices, common household appliances, in food processing as well as in the study of biological systems. Prerequisites for studying heat and mass transfer on a university level include a background in calculus and physics. The application of the concept of heat transfer can be simply understood when you put on a winter coat, the trapped heat keeps you warm. Evaporation is a simple example of mass transfer.

Things You'll Need

Glass
Water
Salt
Spoon
Stove
Pot or teapot
Copper plate
Steel plate or pan
Thermostat (heating system)

Instructions

- 1
  
  Evaporating water provides an example of the mass transfer of water into the air.
  
  Dissolve a tablespoon of salt in a large glass or water. Stir the water with a spoon. Notice how only some of the salt drifts to the bottom of the glass, while the rest of the salt dissolves and diffuses in the water. Taste the water and observe how the water has transformed from fresh to salty water. This illustrates the process of mass transfer as molecules of salt diffuse with molecules of water to form a new substance. A similar process occurs when a copper plate is placed on a steel plate, atoms of copper and molecules of steel are exchanged between the two surfaces. This process of mass transference between surfaces is referred to as convection. With the process of evaporation, water molecules diffuse into the air when exposed to heat. These three examples demonstrate basic principles of mass transfer.
- 2
  
  Laws of thermodynamics are involved in the design of household appliances.
  
  Plug in a vacuum or toaster and turn it on. Run a battery-powered tool like a rechargeable drill. Put gas in your car engine and turn on the ignition key. All of these processes demonstrate the transference of energy, which is converted for everyday use. Thermodynamics is a sub-topic of heat and mass transfer that studies how and at what rates energy is transferred. NASA defines thermodynamics as the study of the effects of work, heat and energy on a system. The design of all appliances and equipment takes thermodynamics and energy transfer into consideration.
- 3
  
  Heat transference can be understood when you turn up the thermostat in your home.
  
  Turn up the thermostat in your heating system. Notice how the heat of the room or home gradually rises. Turn on the stove and boil water or tea. Now turn the heat on low to maintain the temperature for several minutes. These examples demonstrate the principles of heat transfer. Heat is transferred from a radiator into the air of the enclosed room or from the fire of a gas stove or electric burner to the surface of a pot. The heat of the pot is transferred again from the surface of the pot to the water. Adjusting the temperature changes the rate of heat transfer from a radiator to the air. These concepts can be understood on a much broader context in terms of the sun, solar energy and when studying the greenhouse effect.

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