Tuesday, 29 April 2014

Know about Thermosyphon in Solar Water Heating System

thermosiphon,solar water heater,solar water heating system,solar thermal system,thermal heat,sun heat,sun energy,solar energy,thermosiphon principles
Thermosiphon Is a term usually referred in physics for passive heat exchange by natural convection of a liquid without using a external pump.The principle is simple,Cold water has higher specific density than a warm water,so the heavier always sinks and collector was placed in the downside of a storage tank in order to heat up,When cold water passes to the solar collector,Due to solar radiation the water gets warmer ,As we know warm water specific density was lower, the Warm water moves from collector to the storage tank.Lighter one always float,By applying these principle the warm water floats over cold water,We will get warm water from the top surface of water level.

The storage tank need to be placed well above the collector ,otherwise all the water will backflow during the night and becomes cold,The Thermosiphon works perfectly for the small and medium systems but for large systems the construction and operation will be difficult.These thermosiphon systems are suitable only for the frost free regions.

Usually the storage tank is covered by an insulating material to avoid any convection due to sunlight and made of stainless steel tank for corrosion free operation.The materials include Solar collector,piping,insulation,storage tank,strong roof,supports are vital need for construction of solar thermal power system.

Physics Related to the operation of Thermosiphon.

First law of thermodynamics- States that energy may be changed from one form to another, but cannot be created or destroyed. - Energy is always conserved.

This law may be applied to the movement of water in thermosiphoning system: Energy from the sun is directed and transferred (via conduction and convection) to either water, air, or another medium of choice. This natural process of heating eliminates the need for external energy sources such as fossil fuels or electricity.

Second law of thermodynamics- States that in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state. - The net return of a system is always less than that of which was initially put in.

Energy is always conserved, however energy (or heat in this case) may often be lost in a given system (thermosiphoning) as heat. Adding insulation with appropriate R values to the system and its plumbing may greatly reduce heat loss, and thus increase efficiency.

Planck’s Law- the wavelength of radiation emitted from a surface is proportional to the temperature of the surface

Energy transferred as a result of temperature differences between two objects -Dark objects absorb heat, while light objects reflect

Darkly colored collection plates within the solar collector will aid in increasing solar absorption, thus increasing the amount of heat available to heat water or air in thermosiphoning. In contrast, reflective or lightly colored piping and storage tanks should be utilized as the light colors will help to reduce heat radiation out of the system.