Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
ENHANCED HEAT TRANSFER IN SOLAR WATER HEATER (WITH PARABOLIC COLLECTOR) USING PARTIALLY REFLECTIVE GLASS – A NOVEL IDEA 1Karunamurthy 1 3 K, 2Kanakarajan B, 2Chandrasegaran T Assistant Professor / Mechanical, JJ College of Engineering and Technology, Tiruchirappalli Students of Final Year B.E (Mechanical), JJ College of Engineering and Technology, Tiruchirappalli Abstract: Solar energy collectors are focus on the flowing fluid will result in special kind of heat exchangers that high temperature output. convert the solar irradiation into internal Keywords: Solar water heater, solar energy energy of the flowing fluid. It is the major component of any solar system. utilization, enhanced heat transfer, partially reflective glass. There are basically two types of solar collectors: stationary) non-concentrating and concentrating. (or The concentrating type collectors require tracking mechanism for better performance. Solar water heaters with parabolic collectors are very common type. Line focusing type of collection of radiation energy is adopted in parabolic trough collectors. In this paper an attempt is made to incorporate partially reflective glass with the parabolic collector. Partially reflective glass will allow 50% of the radiation to pass through and the remaining 50% of radiation will be reflected back. This reflected radiation along with incoming radiation is from the source is collimated to form highly intense radiation. This high energy radiation, if allowed to I. Introduction Nowadays, most(80%) of worlds energy demand is met from fossil fuels. massive exploitation of fossil fuels leads to a real threat to the environment, through global warming and acidification of the water cycle. The distribution of fossil fuels around the world is equally uneven. Middle East possesses more than half of the known oil reserves. This fact leads to economical instability around the world, which affects the whole geopolitical system. The present system as it is cannot be maintained for more than two generations. The impact it has on the environment as well to the humans cannot be disputed. So it is mandatory to switch to renewable resources. Renewable energy technology produces marketable energy by converting natural phenomena into useful form of energy At the end of 2001 the total these technologies use the sun’s energy installed capacity of renewable energy and its direct and indirect effects on the system was equivalent to 9% of the total earth (solar radiation, wind falling water electricity generation. By applying a and renewable energy intensive scenario the various plants, i.e. biomass), gravitational forces (tides), and the heat global of the earth’s core (geothermal) as the sources by 2050 would reach 318 joules. recourses from which energy consumption II. Solar Collectors energy potential, however, they are diffused and Solar energy collectors are special fully kinds of heat exchangers that transform solar accessible, most of them are intermittent, radiation energy to internal energy of the and have distinct regional variability’s. transport medium. The major component of These to any solar system is the solar collector. This difficult, but solvable, technical and is a device that absorbs the incoming economical challenges. solar radiation, converts it into heat, and characteristics not renewable is produced . These resources have massive generally of give rise transfers the heat to a fluid (usually air, Nowadays, the water, or oil) flowing through the collector. efficiency of collection and conversion, The solar energy Collected is carried from lowering the initial and maintenance the circulating fluid either directly to the hot cost, and increasing the reliability of and water or space conditioning equipment or to applicability make significant progress. a thermal energy storage tank, from which it Energy conversion system that is based can be drawn for use at night or on cloudy on days. renewable improving energy technologies appeared to be cost effective compared to the projected high cost of oil. There are basically two types of solar Furthermore, renewable energy system collectors: non-concentrating or stationary can have a beneficial impact on the and concentrating. environmental, economic and political collector has the same for intercepting and issues of the world. absorbing solar radiation, whereas a suntracking A concentrating non-concentrating solar collector usually has concave reflecting surfaces to intercept and focus the B. Non-concentrating type collector sun’s beam In this type of collector, the radiation to a smaller receiving area, radiation is allowed to fall over the thereby increasing the radiation flux. entire surface of the flat plate collector, Concentrating collectors are suitable for instead of concentrating at particular high-temperature point below figure shows the non- applications. Solar collectors can also be distinguished by concentrating the type of heat transfer liquid used important parts. collectors and its (water, non-freezing liquid, air, or heat transfer oil) and whether they are covered III. Methods to increase the rate of or uncovered. When solar radiation passes heat transfer in Solar Water Heaters through a transparent cover and impinges on the blackened absorber surface of high A. Green house Principle: absorptive, a large portion of this energy is This principle is used to trap the heat absorbed by the plate and transferred to by using evacuated glass tubes, it consist of the transport medium in the fluid tubes, to inner copper tube and outer glass tube ,the be carried away for storage or use. The glass tube behaves as the green house gas underside of the absorber plate and the two which locks the heat, results in increasing sides are well insulated to reduce the the radiation. conduction loss the liquid tubes can be welded the absorbing plate or they can be an integral part of the plate. The liquid tubes are connected in both the ends by largediameter header tubes. A. Concentrating type Collectors In this type of solar collectors the radiation is either concentrated in a particular point or in a line. So they are classified into two types namely line focusing and point. Fig 1: Water tube in a concentric glass tube B. Selective Coating partially reflective mirror. 50% of In this type, the receiver surface is photons passed to the required target, coated with selective materials in order to and the remaining 50%enters into the trap the heat resulting in increased radiation. source. By multiple reflections the intensity of the beam gets increased. In C. Using reflective surfaces this solar heater, a partially reflected In this type the collector consist of glass is placed in between the collector mirror in order to get a good reflection. and receiver, when the incident sun light Schematic diagram shows the collector with fall on the collector it is passed to the reflecting surfaces partially reflective mirror. it send 50% of radiation to the receiver remaining 50% return back to the collector, but the collector receiving the radiation continuously, thus the intensity of the radiation get increased, thus very huge amount of heat is generated. Fig 2: Parabolic collector with reflective mirror D. Physics behind partially reflective glass A partially reflected glass is also known as semi silvered glass which allows the light partially into the target and remaining into the source. It is used in lasers in order to achieve the high coherent and intense source of light. Initially small quantity of photon is generated by optical pumping and the photons lies in between the partial and fully reflected mirror, and then the generated photon is allowed to strike the Fig 3: Schematic diagram of collector along with partially reflecting mirror [6] Stu campell-build your own solar water heater, garden way publishing IV. Conclusion The paper shows to increase the radiation by this way we have to improve the efficiency of solar water heating system using partially reflective glass. Using this system we have generate a heat with in the fraction of seconds in a small area. References [1] P.L.knight & A. miller- measuring the quantum state of light, Cambridge studies in modern optics. [2] Alastair I.M.Rae-quantum physics illusion or reality, Cambridge university press. [3] G.D Rai- non conventional energy sources-khanna publication-2007. [4] Barry L.Butler, golden, colo- light weight diaphragm mirror module system for solar collectors, US PATENT, 1985. [5] David K. Fork, Palo Alto, Calif-laser beam conditioner using partially reflective mirrors, US PATENT, Jan, 1999. charlotte, Vermont 05445