IMPACT OF SELECTIVE SURFACE ON PERFARMANCE OF SOLAR THERMAL SYSTEM

IMPACT OF SELECTIVE SURFACE ON PERFARMANCE OF SOLAR THERMAL SYSTEM

A FIRST REVIEW PROJECT SUBMITTED BY

NAGARAJAN S (421313114022)VIGNESHVARAN.S (421313114044)

Under the guidance of Mr.S.KARTHIKEYAN Associate professor

ABSTRACT

In this work, we proposed a low cost material to be used as an excellent absorber for solar collectors, to increase its thermal efficiency by the high capacity to absorb solar radiation. A comparative analysis between the optical properties (reflectance, absorbance, and emissivity) measured on four various materials like Aluminium sheet, Stainless Steel sheet, Copper sheet and Mild Steel sheet. It has been observed that the yield is very low upto noon but increased at after noon.

INTRODUCTIONThe main aim of this research work is to compare four different absorber plates and determine optimum absorber plate which can increase the yield from( solar still, solar water heater, solar furnace, like that).To increase the absorbance of the surface coating in order to improve the thermal efficiency. Metal makes a good thermal conductor, especially copper and aluminium. In high performance collectors, a "selective surface" is used in which the collector surface is coated with a material having properties of high- absorption and low-emissivity. The selective surface reduces heat-loss caused by infrared radiant emission from the collector to ambient.

Literature review 1:An investigation on the performance characteristics of solar flat plate collector with different selective surface coatings(ES PRAKASH)In the present work, investigations are made to study performance characteristics of solar flat plate collector with different selective surface coatings. Flat plate collector is one of the important solar energy trapping device which uses air or water as working fluid. Of the many solar collector concepts presently being developed, the relative simple flat plate solar collector has found the widest application so far.Keywords: Selective surface coatings; Solar flat plate collector; Collector performance.

Literature review 2:A high absorbance material for solar collectors applications (A I Oliva, R D Maldonado, E A Daz, A I Montalvo) In this work, we proposed a low cost material to be used as an excellent absorber for solar collectors, to increase its thermal efficiency by the high capacity to absorb solar radiation. The material, known as smoke black (soot) can be obtained by the incomplete combustion of organic materials, such as the oxygen-acetylene, paraffin, or candles. A comparative analysis between the optical properties (reflectance, absorbance, and emissivity) measured on three covered copper surfaces (without paint, with a commercial matte black paint, and with smoke black) shows amazing optical results for the smoke black.

Literature review 3:Solar Absorptance and Thermal Emittance of Some Common Spacecraft (John H. Hemmer)Solar absorptance and thermal emittance of spacecraft materials are critical parameters in determining spacecraft temperature control. Because thickness, surface preparation, coatings formulation manufacturing techniques, etc. affect these parameters, it is usually necessary to measure the absorbtance and emittance of materials before they are used. Also, because most materials exhibit some amount of degradation dye to outgassing, ultraviolet, and or particle damage, it is necessary to conduct laboratory testing on these materials before certifying them for use in space.

Literature review 4:Solar Selective Coatings for High Temperature Applications(Donald A. Jaworske and Dean A. Shumway )Solar selective coatings are envisioned for use on minisatellites, for applications where solar energy is to be used to power heat engines or to provide thermal energy for remote regions in the interior of the spacecraft. These coatings are designed to have the combined properties of high solar absorptance and low infrared emittance. The coatings must be durable at elevated temperatures. For thermal bus applications, the temperature during operation is likely to be near 100C. For heat engine applications, the temperature is expected to be much greater. The objective of this work was to screen candidate solar selective coatings for their high temperature durability.

Emissivity and Absorptivity

Main article:Kirchoff's law of thermal radiation

The term emissivity is used to describe radiation efficiency of a target compared to a blackbody at the same wavelength, angle and temperature.

9Absorptivity

20% emission

80% absorptivityActual Temperature40C

Apparent Temperature May be absorptivity Apparent Temperature1500C > TOTAL>0.2

Solar Absorptance:

A Beckman DK-2A spectrophotometer modified with a Gier-Dunkle absolute integrating sphere is used for making absolute reflectance, absorptance, and transmittance measurements. This instrument covers the wavelength region from 300 to 2400 nanometers (nm). Their is coupled to a microcomputer for data reduction. The manufacturer's data lists an accuracy of total measurement range.

Kirchhoff's law of thermal radiation

For a body of any arbitrary material emitting and absorbing thermal electromagnetic radiation at every wavelength in thermodynamic equilibrium, the ratio of its emissive power to its dimensionless coefficient of absorption is equal to a universal function only of radioactive wavelength and temperature. That universal function describes the perfect black-body emissive power.

HOW YOU MEASURE TEMPERATURE

All temperature measuring devices accomplish this by measuring an effect of temperature:Thermistor: resistance changes with temperatureThermometer: volume changes with temperatureThermocouple: voltage changes with temperature IR Thermometers: voltage changes with temperature IR Camera: resistance changes with temperature

Experimental Setup

Samples preparation Groups of four samples of copper ,aluminium ,mild steel and stainless steel .All the material dimensions are125 mm x125 mm of 1.5 mm thickness used for solar collectors were prepared. The first group of samples were analysed with high temp spray paint coating on the all sample material. The second group of samples was totally coated with ultra-cover black paint. Third group of samples was completely covered with industrial paint. Similarly the fourth group of sample materials were analysed with the paint of block chrome now compare the group of materials and different types of paints, which set of material and paint gives more efficiency take that particular paint and material.

CopperCopper as an elementsPeriodic symbol: Cu. Density: 8930kg/m3.Melting point: 1083C.Thermal expansion: 0.0168mm/m/C (20-100).Tensile strength: 210 - 240 N/mm2

ALUMINIUM

ALUMINIUM Properties Aluminium is a very light metal with a specific weight of 2.7 g/cm3, about a third that of steel. For example, the use of aluminium in vehicles reduces dead-weight and energy consumption while increasing load capacity.

Electrical and Thermal ConductivityAluminium is an excellent heat and electricity conductor and in relation to its weight is almost twice as good a conductor as copper. This has made aluminium the most commonly used material in major power transmission lines

MILD STEELMild steel is the most widely used steel which is not brittle and cheap in price. Mild steel is not readily tempered or hardened but possesses enough strength.consist of iron alloyed with less than 0.3% carbon most commonly between 0.1 to 0.25%. The building industry frequently uses mild steel in construction because of its ductility and malleability.

Properties :

Solid strengthRust freeAbrasions resistantLong lastingUser friendlyTensile strengthTemperature ToleranceDurable and long lasting

Stainless SteelVery hard, making it difficult to create a profileShould not be blasted with steel grit or shotCauses corrosion problemsNon-carbon blast materials, brushes or grinding disks should be used.

General Properties of Stainless SteelsElectrical ResistivitySurface & bulk resistance is higher than that for plain-carbon steelsThermal ConductivityAbout 40 to 50 percent that of plain-carbon steelMelting TemperaturePlain-carbon:1480-1540 CMartensitic: 1400-1530 CFerritic: 1400-1530 CAustenitic: 1370-1450 C

Coefficient of Thermal ExpansionGreater coefficient than plain-carbon steelsHigh StrengthExhibit high strength at room and elevated temperaturesSurface PreparationSurface films must be removed prior to weldingSpot SpacingLess shunting is observed than plain-carbon steels

control the corrosion in low cost

Coating system method:

BLOCK CHROME100% mirror like chromed effectvery good lastingapplication easiness with special equipmentpractically applicable on any surface

RUST OLIUMThe ultimate protection for industrial environments. Formulated with the highest quality pigments and resins, the High Performance brand of coatings has the highest paint solids in the industry. These proprietary formulations are designed for severe industrial environments and are backed by a Rust-Proof Guarantee. The High Performance brand is the foundation of Rust-Oleum Corporation.

RUST OLEUM

BOSNY SPRAY PAINT

FeaturesResists outgassing to 400F (204C)Heat resistant to 1,500F (538C)Doesn't peel, flake or chalkWon't bleach or discolour Withstands repeated thermal cyclingResistant to UV degradationDries for handling in 30 minutesAir dry or heat cure Long lasting

PRINCIPLES OF CORROSION

Corrosion is the disintegration of an engineered material into its constituent atom due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as O2.

Effects of corrosionReduces strengthLife time is reducedMetallic properties are lostWastage of metal

IMPORTANCE OF CORROSION DATA 5 mpyGood corrosion resistant material

5 to 50 mpyLow corrosion resistant material

50 mpyUnsuitable as constructional material

CORROSION DAMAGEDisfiguration or loss of appearance Loss of material Maintenance cost Extractive metallurgy in reverse- Loss of precious minerals, power, water and man-power Loss in reliability & safetyPlant shutdown, contamination of product etc

WORK IS TO BE DONE:The equipment and material was purchased.The purchased equipment wereRest olium paintBosney spray paintIndustrial paintCopper, aluminium,mild steel,stainless steel plate.

FUTURE WORK:To start the fabrication work of selective surface coating.To analyze the experimental investigation of absorptivity and then low emissivity.

THANK YOU ALL

Any Question?