SOLAR THERMAL COLLECTORS
Definition :-
Solar thermal collectors are the devices which use heat Energy in the solar Radiations directly to heat the fluids circulated through tubes.
Incidental Solar Radiations have Electromagnetic waves of various waves lengths. Apart from visible spectrum, non visible radiations such as infrared UV and short wave radiations have also large amount of heat Energy which is absorbed by Solar Collectors.
Classification of Solar thermal Collectors :
There are various types and designs of Solar Collectors depending on their application, principles, working fluids, types of heat transfer and materials used in their constructions. They are broadly classified as below :
(1) According to working fluids :-
a. Liquid collectors - Normally water is used as fluid
b. Air collectors - Normally air is used as fluid
(2) According to mounting of collector on the stand :-
a. Stationary Collector - It is fixed in the same position
b. Tracking Collectors - It is move in the direction of sun.
(3) According to method of collection of Radiations :-
a. Flat plate Collectors - Solar Radiations are directly falling on the Collector without any concentration.
b. Concentrating Collectors - In this type of Collectors solar rays are Concentrated before they fall on absorber.
(4) According to type of absorber plate :-
a. Flat absorber plate Collectors - simple flat sheet is used as Collector.
b. Corrugated absorber plate Collector - corrugated sheet is used as Collector.
c. Honey comb Collector - Honey comb types plate is used as Collector.
(5) According to the flow of fluid :-
a. Single pass Collector - Fluid is passing through Collector only for once.
b. Double pass Collector - Fluid is passing Twice through Collector.
c. Multi pass Collector - Fluid is passing more than two times through Collector.
(6) According the Cover Glass :-
a. Single Glass cover type Collector - Only single Glass cover is used.
b. Double glass cover type Collector - Double glass cover is used to protect the leakage of heat.
(7) Vacuum Tube Collector :-
a. Double walled tube are used which the Vacuum is maintained in between the walls tubes.
b. Single wall non-vacuum type Tubes are used in the ordinary Collector.
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