FABRICATION AND COMPARISON OF SOLAR WATER HEATER WITH AND WITHOUT SEMI CIRCULAR TROUGH

Transcription

1 FABRICATION AND COMPARISON OF SOLAR WATER HEATER WITH AND WITHOUT SEMI CIRCULAR TROUGH Ranganatha 1, Lingaraj. K. Ritti 2, Pavan Kumar 3 1, 2, 3 Department of Mechanical Engineering, Shri Madhwa Vadiraja Institute of Technology and Management, Bantakal Udupi, India ABSTRACT: In the present work, an attempt has been made to fabricate a semicircular trough solar water heater and is to increase the performance of the conventional domestic solar water heater by adding the semicircular trough beneath the tube of solar water heater. A conventional tube solar water heater when interfaced with semi-circular trough type of solar collector shows noticeable increase in the collective efficiency and performance when compared to the conventional solar water heater. Solar water heater is tested in two different arrangements with semi-circular trough and without semi-circular trough. The conclusions derived from the comparison made between with and without semi-circular trough has clearly shown that solar water heater with semi-circular trough cause an increase of heat absorption, temperature rise, and thermal efficiency than the conventional tube solar water heater. The obtained result shows the collective efficiency of semicircular trough solar water heater is 54.34% higher than conventional tube solar water heater. Time taken by water to get heated is less in semi-circular trough water heater than in conventional tube system.. Convex lens or mirror placed at end cavities to concentrate the solar rays on the collector tubes can be used to absorbs more sunlight Keywords: Semicircular trough, solar water heater, thermal efficiency, convex lens [1] INTRODUCTION Solar energy is energy that comes from the sun. The sun generates energy in its core in a process called nuclear fusion. During a nuclear fusion, four hydrogen nuclei fuse to become one helium atom. The helium atom weighs less than the four nuclei that combined to form it. Energy equivalent of this mass defect is emitted into space. A small part of the solar radiation reaches the earth. Today, solar energy is used in many areas such as heating water for domestic use, space heating of buildings, lumber drying, agricultural products drying, cooking, electricity production and water distillation [1]. Heating water for domestic use is the most economical way of solar energy utilization. Basically, solar energy is converted into heat using solar collectors and converted into electricity using solar cells. In solar collectors, a fluid is heated using solar energy. 39

2 Fabrication and Comparison of Solar Water Heater with and without Semi Circular Trough According to the type of the fluid used, solar collectors can be also named as solar water heater or solar air heaters [2]. The performance of the model is tested in two stages. In the 1st stage, model is tested without Semicircular trough and in 2nd stage; model is tested with semicircular trough. Comparison of experimental studies with conventional tube solar water heater have shown that semicircular trough solar water heaters are preferred because they cause an increase of heat absorption and temperature rise, thus results in higher efficiency. A novel ICS vessel design based on a pyramid shape was presented by Abdel-Rehin [3], which performed successfully in the studies have been conducted to enhance the thermal performance of the ICSSWH systems by incorporating transparent insulation material. Fibre glass, organic-based transparent foams, inorganic glass foams, and honey comb structures have been used as insulating materials in several designs. To analyze the effect of flow circulation in a thermosyphon system, Grossman et al. [4] carried out a study on a parallel plate absorber type SWH system which was subjected to Forced or natural circulation of water between the storage tank and the absorber plate. This design offered the maximum area of contact between the fluid and the collecting surface exposed to the Sun and may therefore serve as a reference for comparison with other less efficient geometries. Huang [5] developed a more general theory for a parallel plate absorber type system with natural circulation of water between the plate and the tank by representing solar radiation as a sine function of time. Other than investigations on conventional solar flat plate collector, studies have been carried out on the use of heat-pipes in the evacuated tube collector to affect SWH systems. Ng et al. [6] developed and experimentally confirmed a theoretical model to predict the performance of an evacuated-tube heat-pipe solar collector. Performance parameters such as the collector efficiency and useful energy gain were analyzed. For a range of expected coolant temperatures, the heat loss coefficient and efficiency of the collector could be sufficiently represented by a simple linear expression. Redpath et al. [7] carried out an experimental study on a heat-pipe evacuated tube SWH system. A two dimensional particle imaging velocimetry (PIV) was used to visualize the thermosyphon fluid regime. It was concluded from the study that the overall cost of the heat pipe evacuated tube SWH system can be reduced by using thermosyphonic flow instead of forced circulation. The objectives of the project work are to conduct an experiment on conventional tube solar water heater and solar water heater with Semicircular trough and note down the temperature of hot water in equal interval of time and to determine heat absorbed in the tank and to compare the results of heat absorbed in the tank with and without semicircular trough and also to determine the difference in the efficiency obtained by solar water heater with semicircular system over conventional tube system. [2] FABRICATION OF SOLAR WATER HEATER WITH AND WITHOUT SEMICIRCULAR TROUGH Fabrication of solar water heater without semicircular trough and with semicircular trough is carried out to test the thermal efficiency of the solar water heater. Solar water heater without semicircular trough is shown in figure.1. It utilizes a standard absorber tube fitted into the tank placed across the slope. A high absorbance, low remittance copper coating is applied to the inner side of the absorber tube. Absorber tubes are usually made of metal, typically copper or aluminum. Copper is more expensive, but is a better conductor and less prone to corrosion than aluminum. 40

3 Adiabatic tank Water inlet Water outlet Absorber tube Figure: 1. Solar water heater without Semicircular trough Adiabatic tank Water inlet Water outlet Absorber tube Semi circular trough Figure: 2.Solar water heater with Semicircular trough Adiabatic tank is made up of stainless steel which is used to store water. There is no heat exchange takes place between tank and surrounding. Tank is always in contact with water therefore chances of corrosion are high to avoid corrosion stainless steel is used. Cover plate is a transparent sheet used to cover the absorber tube, thereby preventing rain and dust particle which may come in contact with the absorber tube. It also retards the heat from escaping to environment. It is placed about 51.2 mm (2 inch) above the absorber tube. Common materials used for cover plates are glass, float glass flexi glass and fibreglass. Absorber tube consists of one or more copper sheets which are welded to copper tubes. The sheet absorbs the heat from the sun. Then the heat energy is transported via the tubes, through which a transport fluid runs, into a heat accumulator. [3] EXPERIMENTAL SETUP 3.1 Testing solar water heater without semicircular trough The setup is kept at suitable angle according to the time in an open space. Solar radiations are absorbed by the absorber tube and transferred to water that circulates in the tube. This is an 41

4 Fabrication and Comparison of Solar Water Heater with and without Semi Circular Trough incident radiation that means direct absorption. The temperature rises from the atmospheric condition. The heat transfer takes place between the copper tube and the water flowing through it. The storage tank is kept at higher elevation in order to obtain thermo siphon effect in which hot water moves up without any external force like pumping. The heated water from the absorber tube rises through the transfer hose to the absorber tube for the further heat addition. The temperature of hot water which is stored in the adiabatic tank is noted down for every 15 or 30 minutes and the readings are tabulated. The conventional mercury thermometer is used to measure the temperature of the water in the adiabatic tank. 3.2 Testing solar water heater with semicircular trough Aluminum sheet is taken and is fixed to the supporting stand as shown in figure 2. Water is filled in the tank to its maximum capacity. The temperature of hot water which is stored in the adiabatic tank is noted down for every 15 or 30 minutes and the readings are tabulated. The conventional mercury thermometer is used to measure the temperature of the water in the adiabatic tank. Normally less area is exposed to sun, so energy collection will be low. Here due to application of trough the energy flex on the absorber tube is high. It gives more efficiency when compared to the conventional tube solar water heater. The both solar heater is tested at the mid-day (12:00PM- 1:30PM) for better efficiency. [4] RESULTS AND DISCUSSION Figure: 3. Sun radiations falling on Semicircular trough 4.1 Testing solar water heater without semicircular trough By conventional method experiment is conducted on 8th May 2014, at12:00pm-1:15pm. Ambient temperature: 30.5 C.with working medium as water. The table 1 shows the determination of heat added to the water for trial 1.0 Table: 2 shows the determination of heat added to water for trial 2 Table: 1 to the water (trail1) Sl. no. Time (t) in minutes. (T) in ᵒ C. (Q) in KJ

5 Table: 2 to the water (trail2) Sl. no. Time (t) in minutes. (T) in ᵒ C. (Q) in KJ Testing solar water heater with semicircular trough By introducing Semi-circular trough to the original model experiment is conducted on 17th May 2014, at12:00pm-1:15pm. In ambient temperature: 30.5 C. Table 3 shows the experimental values for trial 1 Table 3. to the water (trial1) Sl.no. Time (t) in minutes (T) in ᵒ C The same experiment is conducted on 18th May 2014, at 12:00PM-1:15PM.in ambient temperature: 31 C. Table 4 shows the experimental values for trial 2 Table 4. to the water (trial2) (Q) in KJ Sl. no. Time (t) in minutes (T) in ᵒ C (Q) in KJ Average increased percentage of total heat transferred with semi-circular trough when compared to conventional tube is (100* )/ = 54.3% 43

6 Fabrication and Comparison of Solar Water Heater with and without Semi Circular Trough Table 5.0 Compression of heat added to the water Sl. No. Experiment conducted (Q) in KJ. 1 Without Trial semicircular trough Trial With Trial semicircular trough Trial Figure: 4. Graphical representation of solar water heater with and without semicircular trough [5] CONCLUSIONS Following conclusion can be made from the present work 1. The presented technology can be used successfully to increase efficiency of the conventional water heaters 2. The existing solar water heater is observed and the modification is made by incorporating the semicircular trough beneath the absorber tube. The obtained result shows the collective efficiency of semicircular trough solar water heater is 54.34% higher than conventional tube solar water heater 3. Time taken by water to get heated is less in semi-circular trough water heater than in conventional tube system REFERENCES [1] P K Nag, Solar Power Engineering Tata McGraw Hill, 2003 [2] Solar Energy, Fundamental and application by H P Garg & J Prakash [3] Abdel-Rehim ZS. New design of solar water heater. Journal of Engineering and Applied Sciences 1997; 44(3): [4] Grossman G, Shitzer A, Zvirin Y. Heat transfer analysis of a flat-plate solar energy collector. Solar Energy 1977;19:

7 [5] Huang B J Similarity theory of solar water heater with natural circulation. Solar Energy 1980;25: [6] Ng KC, Yap C, Khor T H. Outdoor testing of evacuated-tube heat-pipe solar collectors, Proceedings of the Institution of Mechanical Engineers 2000; 214(part E): (Article). [7] Redpath DAG, Eames PC, Lo SNG, Griffiths PW. Experimental investigation of natural convection heat exchange within a physical model of the manifold chamber of a thermosyphon heat-pipe evacuated tube solar water heater. Solar Energy 2009;83: [8] M A Islam, M A R Khan and M. A. R. Sarkar, Performance of a Two-Phase Solar Collector in Water Heating, Journal of Energy & Environment 4 (2005): Technical Note Author[s] brief Introduction Mr. Ranagantha is working as an Assistant Professor in Mechanical Engineering department at institute mentioned in author details section. He completed his Masters in Design Engineering in B M S Engineering College Bangalore and has 5 years of teaching experience. His interested topics are Design of Machine Elements, Mechanical Vibrations, Tribology etc. Mr. Lingaraj K Ritti also works in same institute as an Assistant Professor in Mechanical Engineering department. He completed his Masters in Design Engineering In JNNCE Shimoga and has 5 years of teaching experience. His interested topics are Strength of Materials, Kinematics of Machines, Finite element method, Mechanical Vibrations, Tribology etc. He published 2 papers in two international Journals. Mr. Pavan Kumar also belongs to same institute and working as an Assistant Professor in Mechanical Engineering department. He completed his Masters in Production Engineering in PDACE Gulbarga and has 5 years of teaching experience and 3 years of industrial Experience. His interested topics are Manufacturing Process, CIM, Production Technology, Tribology etc. He published 7 international Journal papers and has working Editor/ reviewer for 3 international Journals. 45