STUDY OF FLAT PLATE COLLECTOR SOLAR WATER HEATER

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1 STUDY OF FLAT PLATE COLLECTOR SOLAR WATER HEATER Bhagyashree P Dahane, S.P. Adhau dahane.hagyashree@gmail.com, adhau_sp@yahoo.co.in Astract: In this paper experimental results of flat plate collector are presented. A solar water heater indoor unit is studied. The test was conducted over a period of few hours to determine the performance of the setup. As this water heater is an indoor unit, halogen lamp has een used as a source of radiation, with the help of regulator radiation can e varied. Experiment was conducted y setting radiation and wind velocity at particular point. In 0 minutes we get the collector time constant. The overall heat loss coefficient we get is within the standard range, where top loss coefficient dominates the ase loss coefficient as well as the side loss coefficient. Keywords: Solar water heater, Thermosyphon mode, Collector time constant, Overall heat loss coefficient I. INTRODUCTION There has always een a gap etween supply and demand of electricity energy and the situation further worsen during peak hours when enormous heating load is switched on. If the heating load is switched over to non conventional source of energy from conventional energy sources the gap can e ridged consideraly. Solar energy is an ultimate source of renewale energy and it can e ridged the gap etween demand and supply of electricity and it also saves money since its running cost is zero. Flat plate collector is widely used for domestic hot water, space heating and for applications requiring fluid less than 80 C. Heating water for domestic purpose is a simple and effective way of utilizing solar energy. A type of solar thermal collectors, relative thermal analyses and practical applications of each type is given in []. Collector efficiency is calculated []. Experiment was conducted in Bangladesh and data is collected for months. It is found that FPC water heater can work without disturance [3].This [4] paper suggests using a phase transition material as working fluid. It undergoes phase transition at a specific and release latent heat which is used to heat the water. It is suggested [5] that instead of leaving collector mount in a fixed position throughout a year it is suggest to tilt it monthly, seasonally or i-annually. The experiment is conducted in order to find out long term performances of FPC y system advisor model [6]. In this [7] paper two FPC are studied one with conventional design and another is with new design i.e. in this collector the heat transfer directly takes place from the asorer plate to the fluid. Also the material used for asorer plate is GI ut instead of Cu. And there is a small difference etween the output s while using a different collector. Experiment is carried out [8] whose result reveals that the performance of the water heater depends on the flow rate through the collector, the collector efficiency increases with the increase in flow rate and incident solar radiation. In this paper [9] an auxiliary tank filled with cold water is warmed y exposition to the sun and then transferred to the tank so that it will get heated quickly and y doing this efficiency of solar water heater is improved. This paper [0] studies some incentives which can e offered to consumers to increase the use of solar water heater. 80 II. SOLAR COLLECTORS Solar collectors are the main component of active solarheating systems. They asor the sun's energy, transform its radiation into heat, and then transfer that heat to a working fluid (usually water or air). The solar thermal energy can e used in solar water-heating

2 systems, solar pool heaters, and solar space-heating systems. These designs are classified in two general types of solar collectors: Non Concentrating collectors the asoring surface is approximately as large as the overall collector area that intercepts the sun's rays. Concentrating collectors large areas of mirrors or lenses focus the sunlight onto a smaller asorer. III. FLAT-PLATE COLLECTOR Flat-plate collectors are the most common solar collector for solar water-heating systems in homes and solar space heating. A typical flat-plate collector is an insulated metal ox with a glass or plastic cover (called the glazing) and a dark-coloured asorer plate. These collectors heat liquid or air at s less than 80 C.The Schematic diagram of the experimental setup is shown in Figure. Description of the system (solar water heater) suject to study is composed of: Flat plate solar collector with characteristics given in Tale. A horizontal storage tank of 00 litters capacity, insulated with Rockwool material and its insulation thickness-ase and insulation thickness-side are 50 and 5 mm respectively. TABLE CHARACTERISTICS OF THE COLLECTOR Dimension Radiator No of tue = 0, L=.7, Di=.7mm Asorer Copper, Insulation Back Lateral Tempered glass 0.5 mm thickness Rockwool 50mm 5mm Thickness=4mm Transmission=0.85 A. Collector Time constant: Collector time constant is required to evaluate the transient ehaviour of a collector. It is define as the time required rising the outlet y 0.63 of the total increase from T fo T a at time zero to T fo T a at time infinity i.e. time at which the outlet attains a stagnant value. It can e calculated from the curve etween R and time as shown elow. Where R is given as, R= T fo t T fo (0) T fo α T fo (0) Where, T fo t : Outlet water at any time t T fo (0) : Outlet water at time zero T fo α : Outlet water at infinite time (maximum ) B. Heat Loss coefficient (U L ) U L is the overall heat transfer coefficient from the asorer plate to the amient air. It is a complicated function of the collector construction and its operating conditions. In simple term it can e expressed as, U L =U t +U +U e () According to Klein (975), the top loss coefficient can e calculated y using the flowing formula. U t = { Where, N C Tp [T p Ta ] N +f h a } + { C=365.9( β β ) σ (T p +T a )(T p +Ta ) ε p +0.05N ( ε p) + N+f N εg f=(+0.04h a h a ) ( N) h a = v } () The heat loss from the ottom of the collector is first conducted through the insulation and then y a comined convection and infrared radiation transfer to the surrounding amient air. However the radiation term can e neglected as the of the ottom part of the casing is very low. Moreover the conduction resistance of the insulation ehind the collector plate governs the heat loss from the collector plate through the ack of the collector casing. The heat loss from the ack of the plate rarely exceeds 0% of the upward loss. To calculated the ottom loss coefficients we can use the following formula U = k x (3) In a similar way, the heat transfer coefficient for the heat loss from the collector edges can e otained y using the following formula U e =U ( A e A C ) (4) Assumptions: To perform different experiments with this set-up a numer of assumptions need to e made. These 8

3 assumptions are not against the asic physical principles ut simplify the prolems up to a great extent.. The collector is in a steady state.. The headers cover only a small area of the collector and can e neglected. 3. Heaters provide uniform flow to the riser tues. 4. Flow through the ack insulation is one dimensional. 5. Temperature gradients around tues are neglected. 6. Properties of materials are independent of. 7. No energy is asored y the cover. 8. Temperature drop through the cover is negligile. 9. Same amient exists at the front and ack of the collector. 0. Dust effects on the cover are negligile (if otherwise mention). There is no shading of the asorer plate (if otherwise mention) Valve Valve 3 Thermometer 4 Cold Tank Air vent Radiation Meter Valve 8 Valve 6 Valve 7 Valve 4 Hot Tank Tap Flow rate measurement (Thermosyphon ) Pressure gauge Anemometer Flow meter (Force mode) Halogen Fixture Thermometer Valve 5 Pressure gauge Thermometer Fan FPC Thermometer 3 Cold Tank Valve Pump Figure Schematic diagram of the experimental setup. IV. OBSERVATION TABLE: Wind speed =.07m/sec, Radiation level = 700 w/m², mass flow rate = 0.0 kg/sec, Amient Temperature = 3ᵒC. S N Time (t, min) Inlet (Ta, ᵒC) Plate (Tfi, ᵒC) Outlet (Tfo, ᵒC) in the Storage tank (Ts, ᵒC) Inlet Pressure (Pi, Kpa) Outlet Pressure (Pout, Kpa)

4 CALCULATION: Now the overall heat loss coefficient can e calculated as: And, And, U t U k 3 x *0 0.9 W / m K A 0.66 e U U e W / m K Ac.73 N ( T T )( T T ) p a p a 0.33 T T N f C p a ( 0.05 N ( )) N p p T N f h g p a *0 ( )( ) * ( *( 0.)) = =.486 W / m K U U U U L t e = =.5657 W / m K V. CONCLUSION: Time at which the outlet attains a stagnant value is collector time constant (0.63 of the total ). And in around 0 minutes 63.% of the total outlet is achieved. Now from the calculated values it can e seen that top loss coefficient dominates oth the ase loss coefficient as well as the side loss coefficient. The ase loss coefficient and the side loss coefficient are constant since the parameter required to calculate it are constant. And the top heat loss coefficient is a function of various parameters which includes the of the asoring plate, amient, wind speed, emissivity of the asoring and the cover glass plate, etc. Since these parameter keeps on varying the value of top loss coefficient keeps changing Nomenclatures: A c : Area of the collector (m ) A e : Area of the edge (m ) k, k e : Conductivity of the ack and edge insulation ( W mk ) m : mass flow rate ( kg sec ) N: Numer of glass cover T a : Amient ( 0 C) T P : Plate ( 0 C) U t, U, U e : Top, ottom and edge heat coefficient respectively. v: Wind velocity ( m sec ) loss w: Distance etween two risers (mm) x, x e :Back and Edge insulation thickness (mm) ε p : Emissivity of the asoring plate ε g : Emissivity of the glass cover REFERENCES: [] Kalogirou SA. Solar thermal collectors and applications.prog Energy Comust 004; 30:3 95. [] Faio Struckmann, Analysis of a Flat plate Solar Collector, Renewale Energy Technology (008). [3] Shahidul Islam Khan, Asif Islam. Performance Analysis of Solar Heater. Smart Grid and Renewale Energy, 0,, [4] Samson A. Arekete. Performance of Solar Heater in Akure, Nigeria. Journal of Energy Technologies and Policy ISSN 4-33 (Paper) ISSN (Online) Vol.3, No.6, 03. [5] Y. Tian, C.Y. Zhao. A review of solar collectors and thermal energy storage in solar thermal applications. Applied Energy 04 (03) (Elsevier). [6] P. Sivakumar, W. Christraj, M. Sridharan and N. Jayamalathi. Performance Improvement Study Of Solar Heating System. ARPN Journal of Engineering and Applied Sciences vol. 7, no., JANUARY 0. 83

5 [7] Zhang Tao,Zou Tonghua, Ye Qingyin. Experimental Research on the Performance of the Heat Storage Solar Heater. 0 IEEE. [8] Houda Ennaceri, Khalid Loudiyi. Modeling the Variation of Optimum Tilt Angles for Flat-Plate Solar Collectors in Ifrane, Morocco. 03 IEEE. [9] Akachukwu Ben Eke. Prediction of optimum angle of inclination for flat plate solar collector in Zaria, Nigeria. CIGR Journal. Vol. 3, No.4, 0. [0] Saw C. L. A.P. Dr. Hussain Al-Kayiem. An Investigation of Integrated Flat Plate Solar Collector: Experimental Measurement. 0 IEEE. Figure 3 The graph etween R and time is as shown aove. It can e seen from the graph that in around 0 minutes the value of collector time constant is achieved i.e of the total. 84