Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101000 | P a g eMathematical Modelling of Solar Air HeateraAmey P Marathe bSandeep M Joshi cGajanan N ThokalaM.E. Scholar, Mechanical Engineering Department, PIIT, New Panvel, Mumbai UniversitybAssistant Professor, Mechanical Engineering Department, PIIT, New Panvel, Mumbai UniversitycAssistant Professor, Mechanical Engineering Department, PIIT, New Panvel, Mumbai UniversityAbstractMathematical modeling has becomean accepted tool for predicting theperformance, and optimization of thermalprocesses. Solving the mathematical modelsrepresenting solar air heating process andsystems is one of the most tedious andrepetitive problems. Mathematical modelingof conventional solar air heater with singleglass cover is presented. Calculations for acollector of aperture area 2m2have been donefor Chennai. It has been found that at solarinsolation of 734 W/m2, average temperatureof outlet air is 328.352K (55.32˚C) i.e. rise intemperature of air through the collector is 8˚Cfor air flow rate of 440 kg/h, Instantaneousefficiency of collector is found as 51.8 % andthe pressure drop is 36.982 Pa. Results areclosely matching with such experimentalresults. Finite Difference Method can also beused to solve heat transfer equations forconventional solar air heaters. Theseequations have also been presented in thiswork.KEYWORDS: FLAT PLATE SOLAR AIR HEATER(FPSAH), SOLAR INSOLATION, FINITE DIFFERENCEMETHOD (FDM)I. INTRODUCTIONIn present’s world the prosperity ofnation is measured by the energy consumption ofthat nation, the GDP of country is directly linkedwith energy consumption. Therefore demand forenergy resources is increasing day by day. Thereare various types of energy resources, but mainlythey are divided in to two forms, these arerenewable energy resources (solar, air, wind) andnon-renewable energy resources (coal,petroleum). The industrial growth is acceleratedby non-renewable energy resources, but therestock is limited in nature.The necessity to move into a new energeticmodel of non conventional energy utilization isbeing progressively assumed in our societies dueto climatic changes and expected increase in oilprices as we run out of fossil fuels. A new greentech revolution has been promoted during lastdecade and a great academic and industrial efforthas contributed to turn to non-pollutingrenewable energy sources. Solar energy is themajor source of such kind. The greatestadvantage of solar energy as compared withother forms of energy is that it is clean and canbe supplied without any environmentalpollution. Over the past century fossil fuelshave provided most of our energy becausethese are much cheaper and more convenientthan energy from alternative energy sources,and until recently environmental pollution hasbeen of little concern.Most research into the use of solarenergy in recent years has been on photovoltaictechnology, where sunlight is converteddirectly into electricity. Other than this thereare many applications of solar thermal energysuch as heating, drying and water distillation.Solar radiation arrives on the surface of theearth with a maximum power of approximately1 kWh/m2. The actual usable radiationcomponent varies depending on geographicallocation, cloud cover, hours of sunlight eachday, etc. Solar radiation received is either asdirect radiation or scattered or diffuse radiation,the ratio depends on atmospheric conditions.Both direct and diffuse radiation is useful, butdiffuse radiation cannot be concentrated. Thesolar collector is one of the devices which canabsorb and transfer energy of the sun to ausable and/or storable form in manyapplications such as industrial and spaceheating, drying agro, textile and marineproducts.Several designs of the solar thermalcollectors have been built and tested dependingon their applications. Figure 1 and 2 shows theexploded and pictorial view of a typical FlatPlate Solar Collector which is further used formathematical modeling and analysis.Fig.1: Exploded View of Typical Flat PlateCollector
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101001 | P a g eFig.2: Pictorial View of Typical Flat PlateCollectorNumerical simulation has been revealedas an important tool in the past years in order toprovide an insight into physical industrialprocesses, improving systems performance andprocess optimization.Aim and objective of this work is toreview and understand the design procedure offlat plate solar air heaters, FPSAH and develop amathematical model for thermal analysis ofFPSAH using CAD software to predict theThermal efficiency, Useful heat gain, CollectorEfficiency, Collector heat removal factor andPressure drop parameter for Flat Plate solar airheater. And also to investigate the effect oftemperature rise parameter on effectiveefficiency other important parameters.II. Literature ReviewIn any solar-thermal collection device,the principle usually followed is to expose a darksurface to solar to solar radiation so that most ofthe solar radiation is absorbed and converted heatenergy. A part of this heat energy is thentransferred to a fluid like water or air. When nooptical concentration of radiation is done, thedevice in which the collection is achieved iscalled the flat plate collector. In other words,when the area of interception of solar radiation issame as that of absorption then the collectiondevice is called flat-plate collector else it isconcentrating collector. The flat plate collector isthe most important type of solar collectorbecause it is simple in design, has no movingparts and requires little maintenance. It can beused for variety of applications in whichtemperature of required heat energy ranges from40-100oC.When the temperature above100oC arerequired, it usually becomes necessary toconcentrate the radiation. This is achieved byconcentrating collector. The devices which areused for this purpose are known as solarcollectors. Fig 3 shows classification of solarcollectors.Fig. 3: Classification of Solar Collectors.Flat-plate collectors are very commonand are available as liquid based and air-basedcollectors. These collectors are better suited formoderate temperature applications where thedemand temperature is 30- 70oC and forapplications that require heat during the wintermonths. The air-based collectors are used forthe heating of buildings, ventilation air andcrop-drying. In this type of collector a flatabsorber plate efficiently transforms sunlightinto heat. To minimize heat escaping, the plateis located between a glazing (glass pane ortransparent material) and an insulating panel.The glazing is chosen so that a maximumamount of sunlight will pass though it andreach absorber.A flat plate collector basically consistsof a flat surface with high absorptivity for solarradiations, called the absorbing surface;typically a metal plate, painted black. Theenergy is transferred from the absorber plate toa carrier fluid circulating across the collector.Thermal insulation is usually placed on the rearside to prevent heat losses. The front side hastransparent covers, generally glass that allowstransmission of incoming solar radiations but isopaque to the infrared radiations form theabsorber plate. Flat plate collectors are usuallypermanently fixed in position and require notracking of the sun. The collector should beoriented directly towards the equator, facingsouth in the northern hemisphere and facingnorth in the southern hemisphere. Fig 4Schematic of smooth flat plate collector.
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101002 | P a g eFig.4 :Schematic of Smooth Flat PlateCollector (Choudhury et al, 1993)For year round applications, theoptimum tilt angle of collector is equal to thelatitude, whereas for winter, tilt angle should beapproximately 10° to 15° more than the latitudeand for summer, tilt angle should beapproximately 10° to 15° less than latitude.Temperature up to a maximum of about 100 °Cabove ambient can be achieved through flat platecollectors. Flat plate solar collectors may bedivided into two main classifications based onthe type of heat transfer fluid used i.e. liquidheating and air heating collectors.There is an increasing demand for thesolar collectors, especially the flat-plate solarcollector. Owing to the many parametersaffecting the solar collector performance,attempting to make a detailed analysis of a solarcollector is a very complicated problem.Fortunately, a relatively simple analysis willyield very useful results, Duffie Beckmann, 1991.One of the most potential applicationsof solar energy is the supply of hot air for thedrying of agricultural, textile and marineproducts, and heating of buildings to maintain acomfortable environment especially in the winterseason. Designer and potential user of thesesystems must consider a number of factors whencomparing their merits. These can mainly becategorized as: (i) thermal performance, (ii) cost(iii) lifetime/durability, (iv) maintenance and (v)ease of installation. Thermal performance ofcollectors is compared by using the concept ofthermal efficiency. It is generally believed thatthe thermal efficiency of a solar collector is themajor requirement for the prediction of thermalperformance of the complete solar system ofwhich the solar air collector is a part. Chandraand Sodha, 1991 have provided a fundamentalunderstanding of testing procedures for solar airheaters.Solar air heaters are broadly classifiedinto two types: bare plate and cover plate solarenergy collectors, Ekechukwu and Norton, 1999.Based on this classification, authors havesummarized various designs of solar air heaters.Solar air heaters are simple devices to heat air byutilizing solar energy. Such heaters areimplemented in many applications whichrequire low to moderate temperature below 60°C. The disadvantages of solar air heaters arethe need for handling larger volumes of air thanliquids due to the low density of air as aworking substance and low thermal capacity ofair. However, the efficiency of solar air heatersis low because of the low Prandtl number of airUcar and Inallı, 2006 and low absorber to airheat transfer coefficient Ozturk and Demirel,2008. Also, in cases where thermal storage isneeded, water is superior to air. Some of thesedisadvantages are being addressed usingtheoretical models. On the other hand, themost important advantages for solar air heatersinclude: no freezing, boiling or pressureproblems; generally lower weight and lowconstruction cost Selcuk, 1977, Qenawy andMohamad, 2007.Important design parameters areidentified and their appropriateness validatedthrough experimental results, Karslı, 2007 andChow, 2010. Different modifications aresuggested and applied to improve the heattransfer coefficient between the absorber plateand air. These modifications include use ofabsorber with fins Garg et al., 1991, acorrugated absorber Choudhury et al., 1988, asolid matrix Sharma et al., 1991 and hollowspheres Swartman and Ogunade, 1966. Thesemodifications enhance the thermal efficiency ofsolar collector but also increase the pressuredrop, which becomes important at high volumeflow rates of the air. Mohamad, 1997 hasanalyzed the performance of a counter-flowsolar air heater with a porous matrix and theresults were compared with conventional solarair heaters, thermal efficiency of this type ofcollector was found to be exceeding 75%which is much higher than the efficiency of theconventional air heaters.Several investigators have attemptedto design more effective solar air heaters bychanging the design characteristics, theapplications of solar air heaters or usingvarious collector types. Experimentalinvestigation of three different solar flat plateair heaters was carried out by Deniz et al.,2010, two of which having fins, Type II andType III, and the other without fins, Type I, oneof the heater with a fin had single glass cover,Type III and the others had double glasscovers, Type I and Type II. The energy andexergy output rates of the solar air heaters wereevaluated for various air flow rates 25, 50 and100 m3/m2h, tilt angle 0, 15 and 30° andtemperature conditions versus time. Based onthe energy and exergy output rates they foundheater with double glass covers and fins, Type
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101003 | P a g eII, to be more effective and the differencebetween the input and output air temperature tobe higher than of the others. Besides, they alsofound that the circulation time of air inside theheater played more important role than of thenumber of transparent sheet. Lower air flow ratesshould be preferred in the applications of whichtemperature differences is more important.Performance studies on four differenttype of solar air heater, two corrugated and twomesh, was performed by Gupta and Garg 1966.They concluded that solar air heaters of thecorrugated type of construction can be fabricatedto supply hot air up to 30 oC above ambient withan overall efficiency of 60 % and mesh type ofair heaters to supply air up to 20 oC aboveambient with an efficiency of 50 % or more.Ong and Than, 2002 have studied performanceof flat plate solar air heater operating undernatural convection. They plotted mean glass,wall and air temperatures, outlet air temperature,outlet air flow velocity and instantaneousefficiency against solar radiation. They observedthat all the variables plotted increased withincident solar radiation. Wall temperature washigher than glass or air temperatures. Glasstemperature was observed to be lower than airtemperature initially and at low radiation levels.At higher radiation glass temperature was higherthan air temperature. At 90otilt, glasstemperature was always higher than air. Itindicated that the air flow in the duct was non-symmetrical and that the air was initially heatedup by the heat absorbing wall and thentransferred some heat to the glass as it flowsupwards.Satcunanathan and Deonarine, 1973have suggested use of two pass solar air heater toreduce the heat loss. Whillier,1964 carried outexperiments and analyze the conventional airheater consists of an absorbing plate, a rear plate,insulation below the rear plate, transparent coveron exposed side, and the air flows between theabsorbing plate and rear plate. Ranjan et al.,1983 refers to an air heater with flow above theabsorber which consists of an absorber plate witha transparent cover at the top and insulation atthe bottom. The cover and the plate provide thepassage for the air. Solar radiation, aftertransmission through the cover, is absorbed bythe absorber plate. Sodha and Bansalt, 1982have studied an air heater with flow on bothsides of the absorber assuming that equal flowoccurs both above and below the absorber plateand the heat transfer coefficient between theabsorber plate and the air stream on either side isthe same.There are numerous works on bothexperimental and theoretical performance ofsolar air heaters. Steady state heat balanceequations, involved linking plate efficiency andheat removal factors with air flow rates, surfacewind heat transfer coefficients, and heattransfer coefficients between the moving airstreams and the surfaces forming the flowchannels also reported Parker 1981,Vijeysundera et al., 1982, Than and Ong 1984,Biondi et al. 1988, Duffie and Beckman 1991,Verma et al. 1992, Parker et al. 1993. Differentmathematical model and solution procedurewere studied by Ong, 1995. Finite ElementModeling of serpentine Solar Collector waspresented by Álvarez et al., 2010. It was foundthat because of new topology it was possiblefor the fluid to have greater contact surfacewith the absorber plate and leads to an increasein collector efficiency. They obtained anefficiency of 84.5% with maximum platetemperature of 31.7oC for stationary analysis.For low temperature solar dryingapplications (temperature rise less than 40oCabove ambient), single covered solar air heatersare adequate. Where higher temperature risesare desired, double or triple covered solar airheaters can be used to reduce drastically theupward convective and re-radiative heat losses.However, the resulting higher temperature risewould imply more insulation than in bare-plateor single covered solar air heaters. Theadditional cost of constructing double or triplecovered solar air heaters (with improvedinsulation) may not be justified economicallyfor numerous low cost passive solar air heaterdesigns. Because of the considerable heatlosses in bare-plate solar air heaters (withtemperature rise less than 10oC above ambient),they would require high air velocities 15 m/s.The limitation imposed by this is the use offans which, thus, makes bare-plate solar-energyair heaters inappropriate for natural-circulationsolar dryers. For higher temperature rises, thereduction of heat losses from the absorber platebecomes necessary by the use of glazing. ThusSingle cover Flat Plate Solar air Heater isselected for Mathematical Modeling.III Problem FormulationA literature review of solar air heatersshows that that the different type of solar airheaters have been investigated experimentallyunder different systems and operatingconditions by several researchers. Acomparison of performance of these heatersbecome difficult without identical values ofparameters such a ambient conditions, inlet airtemperature, air mass flow rate per unitcollector width, gap between the absorber andcover plates, intensity of solar radiation etc.Thus to compare the performance of these
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101004 | P a g eheaters under identical values of parameters,their simulation becomes necessary.Numerical simulation has been revealed as animportant tool in the past years in order toimprove system performance and processoptimization. Aim and objective of this work isto review and understand the design procedure offlat plate solar air heaters, FPSAH, and develop amathematical model for thermal analysis ofFPSAH. Based on the literature review simplegeometry of a conventional solar air heater isselected.Mathematical simulation ofConventional flat plate solar air heater, FPSAHhas been carried out.Mathematical model for designing aFPSAH is obtained by the application of thegoverning conservation laws. The heat balance isaccomplished across each component of FPSAHi.e., glass covers, air stream and the absorberplate. The heat balance for the air stream yieldsthe governing differential equations and theassociated boundary conditions. The finitedifference method, FDM, is used to solve thedifferential equations and hence to simulate agiven solar air heater. Study has been extendedby changing the various governing parameterslike the air mass flow rate, the inlet airtemperature, the depth of the collector duct andthe intensity of solar radiation.Simulation in a crude sense is themethod of predicting the output of a proposedsystem or an existing system without conductingexperiment on it. System simulation involves thedevelopment of the mathematical model for agiven problem which should be dynamic innature. The mathematical model is then solvednumerically. Energy balance analysis for FPSAHhas been presented in this work. The analysis isbased on the assumption that heat and the fluidflow are one-dimensional and in steady state. Anumerical approach is applied to obtain thesolution of the given problem.In FDM method, the physical domain isfirst discritized into computational domain by themethod of grid generation. The grid consists ofthe linear elements with nodes at the point ofintersection. The following steps describe thewhole procedure:(i) Differential Equations can be obtainedby the application of governingconservation laws over a system.(ii) Applying finite difference schemes totransform the given differentialequations into the difference equations.(iii) Algebraic equations in nodal unknownsare thus obtained.(iv) These simultaneous algebraic equationscan be solved by any numerical method.(v) The solution of these algebraicequations is the solution at the nodes.(vi) Finally, quantities of interest can becalculated.Following are the assumptions made in theanalysis of the conventional FPSAH:1. The air flow is steady and onedimensional.2. Thermo physical properties of air areindependent of temperature.3. Air velocity in the channel at anysection is constant.4. The temperature drop across thethickness of the covers is negligible.5. Heat loss from the sides of thecollector is very small and henceneglected.6. The temperature distribution withineach element and glass cover isuniform.IV.Mathematical Modeling and AnalysisDesign procedure for solar air heateris presented below. Solar data required forsimulation program has been taken from Mani,1981. The equations used for calculating thecollector efficiency are based on the analysislisted in Sukhatme S.P.and Nayak J K, 2011.4.1 Design Procedure of Solar CollectorThe simulation procedure is given below.Determining number of the day for 21stApril201021312831n n = 111Hour angle at 11.00 am15deg)me)ti((12ω o15ω Declination angle for the day of the year, n =111, for 21stApril n).deg(284365360).sin(23.45.degδCos of incident angle for β = 30oand фl =19.12o)) β).cos(cos(δβ)sin(sin(δθcos ll 924.0θcoso811.5δ
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101005 | P a g eAngle of reflection1.50sinθsinφ 1-ro77.14rφTransmissivity of beam radiation for thevalues of τr = 0.922, τar = 0.969arr .894.0Transmissivity absorptivity product for αp =0.9 ).0.15α(11ατ.ταppb82.0bταTransmissivity of diffused radiation for thevalues of τd = 0.738, τad = 0.964adddif .71.0difTransmissivity and absorptivity product ofdiffused radiation ).0.15α(11α.τταppdiffd0.65ταd Cos of zenith angle .cos.ccscos.sinδsincos ll cos 0.96Tilt factor for beam radiationcoscosθr1963.01rTilt factor for diffuse radiation2cosβ1r20.933r2 Tilt factor for reflected radiation2cosβ1.ρr r3013.03rFlux falling on tilted surface for the valuesof Ib = 591 W/m2, Id = 254 W/m2]).(..[ 321 rIIrIrII dbdbt 2t W/m817.34I Assuming efficiency of solar collector as66%tuclq2/44.539 mWqu Mass flow rate of the air is calculated byassuming a difference of 30 °C in inlet andoutlet air temperature of the collector.dtCpmuqMass flow rate of the airm = 17.89 g/s or 64.4 kg/h.Mass flow rate of the air can be controlled byadjusting fan speed or using dampers or flowcontrollers.Energy Balance analysis have beendone for FPSAH. The analysis is based on theassumption that heat and the fluid flow are one-dimensional and in steady state. A numericalapproach is applied to obtain the solution of thegiven problem. In the present study first amathematical model is obtained by theapplication of the governing conservation laws.The heat balance is accomplished across eachcomponent of a given air heater, i.e., the glasscovers, the air streams and the absorber plate.The heat balance for the air stream yields thegoverning differential equations and theassociated boundary conditions. It is because ofthe radiation heat exchange terms that renderthe problem non-linear hence making the exactsolution cumbersome. So a numerical approachwhich would give a solution with a fairly goodaccuracy is needed.The finite difference (FDM) has beenemployed to solve the differential equations. InFDM technique the first step involves thetransformation of the actual physical domain
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101006 | P a g einto the computational grid. Second step is totransform the differential equations intodifference equations. Which along with theequations obtained by heat balance across thecovers and the absorber are the simultaneous nonlinear algebraic equations. The next step is tosolve those numerically using gauss eliminationmethod. The solution is obtained in the form ofnodal temperatures for the covers, the air streamsand the absorber. Study has been extended bychanging the various governing parameters likethe air mass flow rate, the inlet air temperature,the depth of the collector duct and the intensityof solar radiation and finally the performancecharacteristics have been obtained.Under steady state operating conditions, theenergy balance for the Conventional FPSAH andapplying the Finite Difference Method onproposed model are as below:Fig 4.1 and 4.2 Computational Domain forFPSAHFor ithnode1. For Absorber plate:Governing Differential Equation isI τbαb = Ul (Tpm-Ta) + hfp (Tpm-Tf) + hr (Tpm-Tbm)The Finite Difference equation is (FDE)I τbαb= Ul (Tpm[i]-Ta) + hfp (Tpm[i]-Tf[i]) + hr(Tpm[i]-Tbm[i])On solving the above equation we get,Tpm[i] =2. For Air Stream:Governing Differential Equation ism.cp = hfp (Tpm-Tf) + hfb (Tbm-Tf)Solving FDE using Central Differenceformulationm.cp. = hfp (Tpm[i]-Tf [i-1])+ hfb (Tbm[i]-Tf [i+1])On solving we getTf [i+1] =Associated Boundary condition Tf [-i] = T13. For Bottom Plate:Governing Differential Equation ishr (Tpm-Tbm) = hfb (Tbm-Tf)The FDM equation ishr (Tpm[i]-Tbm[i]) = hfb (Tbm[i]-Tf[i])On solving we get,Tpm[i] =For convenience heat transfer coefficientbetween absorber plate and bottom plate areequal.Therefore hfp = hfb= hfV .ResultsA program in MathCAD has beendeveloped to simulate the conventionalFPSAH. Further FDM has been employed tosolve differential equations obtained by heatbalance across each component (glass cover,air stream and absorber plate).FPSAH is simulated for standardSolar Radiation Data for Chennai. Averagesolar insolation for Chennai is 5.5 kW/m2for7.5 sunshine hours i.e. @ 734 W/m2. Intensityof solar radiation is also calculated for differentincident angles. Collector selected forsimulation has single glass cover, selectivecoated aluminum plate absorber, glass woolinsulation enclosed in a metallic frame. Outlettemperature of air was predicted for specificmass flow rate of air for entire day. Variouslosses were calculated. Useful heat gain of the
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101007 | P a g ecollector was estimated. Finally thermalefficiency of the collector was calculated. Massflow rate of the air flowing through a collector isone of the important parameter as far as collectorperformance in concern. Outlet temperature ofair from the collector at various flow rates wasalso calculated using the developed model.Effect of change in mass flow rate, intensity ofsolar radiation, absorber material on collectorperformance was predicted using the developedmodel and then compared with experimental dataavailable in literature.5.1 Important Outcomes for ConventionalFPSAH:1. Effect of changing parameter on Thermalefficiency: Fig 5.1 shows the variation inthermal efficiency with mass flow rate. Firstthe efficiency increases rapidly for massflow rate 0.01kg/s to 0.1 kg/s then it rise isalmost constant. This is because the usefulheat gain is directly proportional to the massflow rate and the thermal efficiency is theratio of useful gain to the total solarradiation incident on it.2. Effect of changing parameters on Δt/Io: Fig5.2 depicts the variation of Δt/IO with massflow rate. Initially Δt/IO decreases rapidlythen becomes almost constant after the massflow rate of 0.1 kg/s. This may be becausethe solar heat is converted into thermal massof the system initially.3. Effect of changing parameters on air outlettemperature (ta.o): Fig 5.3 depicts thevariation of air outlet temperature with massflow rate. Air outlet air temperature ta.o iscomparatively high at lower mass flow rates.The drop in outlet temperature is significantin early stages of rise in mass flow rate butbecomes almost constant after mass flowrate of 0.1 kg/s.4. Effect of changing parameters on Usefulheat gain (QU): Fig 5.4 depicts the variationof Useful heat gain with mass flow rate. Athigher mass flow rates useful heat gain ismore. More heat is carried away by flowingair this lowers the collector temperature.Lower collector temperature results inreduced losses. This in turn increases usefulheat gain.Results obtained from the simulation study ofConventional Flat plate Solar Air Heater underconsideration is tabulated below: Table 5.1 Results for Chennai Region
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101008 | P a g eFig.5.1 Variation of Mass Flow Rate (m) vs.Thermal Efficiency (η)Fig.5.2 Variation of Mass Flow Rate (m)with Δt/IoFig.5.3 Variation of Mass Flow Rate (m)with Air Outlet Temperature (Ta.o)Fig.5.4 Variation of Mass Flow Rate (m)with Useful Heat Gain (Qu)VI.Conclusions and Recommendationsfor future workResults from the developed modelsuch as efficiency of the collector for specific
Amey P Marathe, Sandeep M Joshi, Gajanan N Thokal / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1000-10101009 | P a g eflow rate, inlet and outlet temperature of air ortemperature lift of the collector are comparedwith experimental data available in the literature.It is found that, model as well as simulationprogram are predicting closely matching resultswith experimental data. This model may be asuitable model for analyzing conventionalFPSAH.Simulation program was run for locationspecific condition, Chennai (13.0810° N,80.2740° E). It is revealed from the simulationprogram that, at solar insolation of 734 W/m2and, mass flow rate of 440 kg/h (0.122 kg/s)gave efficiency about 51.8%. This result isclosely matching with results recorded inliterature for the same type of collector.Recommendations for future workUse of computational fluid dynamicsalong with developed model may lead toexhaustive thermal analysis of flat plate solarcollectors. Temperature distribution along theabsorber surface as well as temperaturedistribution in the glass cover sheets can bepredicted in a better way using CFD. Knowledgeof heat distribution in each component andthermal analysis of the collector lead towardsbetter ways to further minimize various lossesfrom the collector. This will certainly leadtowards enhanced efficiency of the collector.Further Work can also be extended for varyingsolar radiation instead of constant solar radiationas in present work.Use of Finite Volume Method along withImplicit modeling technique may reduce error inpredicting thermal behavior and performance ofthe collector.References1. A Álvarez, M.C. Muñiz, L.M. Varela,O. Cabeza,23th to 25thMarch 2010,Finite element modelling of a solarcollector, International Conference onRenewable Energies and Power Quality(ICREPQ’10) Granada (Spain).2. A.A.Mohamad, 1997, High efficiencySolar air heater, Solar Energy Vol. 60,No. 2, 71-76.3. Bala B. K. and Woods J. L. ,1994,Simulation of the indirect naturalconvection solar drying of rough rice.Solar Energy, Vol. 53, 259-266.4. Biondi P., Cicala L. and Farina G.,1988,Performance analysis of solar airheaters of conventional design, SolarEnergy, Vol. 41, 101-107.5. C L. Gupta and H. P. Garg,1966,Performance Studies on Solar AirHeaters, Solar Energy Vol. 11, No. 1.6. Chandra R, Sodha M S., 1991, Testingprocedures for solar air heaters: areview, Energy Conversion andManagement; Vol. 32, No 1, 11–33.7. Choudhury, C., Anderson, S.L.,Rekstad, J.,1988 A solar air heater forlow temperature applications, SolarEnergy, Vol. 40, 335-344.8. Chow T T., 2010, A review onphotovoltaic/thermal hybrid solartechnology, Applied Energy, Vol.87,365–379.9. Deniz Alta, Emin Bilgili, C. Ertekin,Osman Yaldiz, 2010, Experimentalinvestigation of three different solarair heaters: Energy and exergyanalyses, Applied Energy , Vol. 87,2953–2973.10. Duffie J. and Beckmann W., 1991,Solar engineering of thermalprocesses, 2ndedition, WileyInterscience, New York.11. Ekechukwu OV, Norton B., 1999,Review of solar-energy drying systemsIII: low Temperature air-heating solarcollectors for crop dryingapplications, Energy Conversion andManagement Vol. 40,657–667.12. Garg H. P., Choudhury C. and DattaG, 1991, Theoretical analysis on anew finned type solar air heater,Energy, Vol. 16, 1231-1238.13. Kalogirou., 2004, Solar ThermalCollectors and Applications, Progressin Energy and Combustion Science,Vol. 30, 231–295.14. Karsli S., 2007, Performance analysisof new-design solar air collectors fordrying applications, RenewableEnergy, Vol.32,1645–1660.15. Mani, A.,1985 Methodologies forassessing solar energy potential, IndiaSymposium Workshop on SolarEnergy Research and Application,Department of Mechanical andIndustrial Engineering, University ofRoorkee, 133-146.16. Ong K. S.1995, Thermal PerformanceOf Solar Air Heaters: MathematicalModel And Solution Procedure, SolarEnergy Vol. 55, No. 2, 93-109.17. Ozturk H H, Demirel Y., 2004,Exergy-based performance analysis ofpacked-bed solar air heaters, Int JEnergy Res, Vol. 28,423–432.18. Parker B. F., Lindley M. R., ColliverD. G. and Murphy W. E., 1993,Thermal performance of three solarair heaters, Solar Energy, Vol. 51,467-479.
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