Performance Comparison of a Thermal Energy System Using PCM Encapsulated With Spherical Capsule

Transcription

1 Pefomance Compaison of a Themal Enegy System Usg PCM Encapsulated With Spheical Capsule K. THIMMAREDDY 1, D. R. MEENAKSHI REDDY 2, E. SIVA REDDY 3, S.NARESH 4 1Student, Mechanical Engeeg, G. Pulla Reddy Engeeg (Autonomous) College, Kunool, A.P, India. 2Associate pofesso, Mechanical Engeeg, G. Pulla Reddy Engeeg (Autonomous) College, Kunool, A.P, 3Assistant Pofesso, Mechanical Engeeg, G. Pulla Reddy Engeeg (Autonomous) College, Kunool, A.P, 4Student, Mechanical Engeeg, G. Pulla Reddy Engeeg (Autonomous) College, Kunool, A.P, India, India *** Abstact - Themal enegy stoage (TES) systems povide seveal altenatives fo efficient enegy use and consevation. Nowadays fo sola heatg applications, usage of phase change mateials (PCM) to stoe the heat the fom of latent heat is ceased, because lage quantity of themal enegy is stoed small volume. The pesent expeimental vestigation has been on the themal enegy stoage (TES) system is developed usg application also. paaff and steai as PCM. In the pesent system sola enegy is used as heat souce to stoe the themal enegy Advantages of Themal Enegy Stoage the fom of sensible heat and latent heat. In the TES system paaff and steai ae stoed the fom of spheical capsules of 150 mm diamete. availability. Sensible heat stoage is elatively expensive, but its dawbacks ae its low enegy density and its vaiable dischagg tempeatue. These issues can be ovecome by phase change mateials (PCM)-based TES, which enables highe stoage capacities and taget-oiented dischagg tempeatues. Key Wods: Themal enegy stoage(tes)1, Phase change mateial (PCM)2, Heat tansfe fluid (HTF)3. 1. INTRODUCTION The selection of TES is geneally dependent on the stoage peiod equied, economic viability and opeatg conditions. This system fds many applications domestic, commecial and dustial sectos. It is teestg to note that the combed sensible and latent heat stoage system successfully toduced the ai-conditioned Dynamic balancg between enegy demand and Consevation of pimay fuels Reduce the equipment size and the itial cost. Moe effective and efficient utilization of equipment. Utilization of waste heat ecovey Matenance of envionmental quality Geate flexibility opeation Economical enegy consumption Themal potection and contol of electonic components Heatg and coolg of buildgs and Hot wate pepaation. Enegy is one of the most impotant puts fo the economic gowth of any nation The contuous cease the level of utilization of enegy and the climb fuel pices ae the ma divg foces behd the eseach towad enegy stoage. The themal enegy is a ma topic eseach fo last 20 yeas.themal enegy can be stoed as a change the tenal enegy of ceta mateials as sensible heat, latent heat o both. 1.1 Themal Enegy Stoage Themal enegy stoage (TES) geneal and phase change mateials (PCM) Paticula, have been an aea of eseaches fo the last two decades. The utilization of TES systems educes enegy consumption and povides an altenative as fossil fuels ae gettg depleted. 1.2 Stei popeties PCM plays a vey domant ule the TES system. The selection of the PCM is made based on vaious paametes like latent heat, meltg pot, opeatg tempeatue ange, specific volume, boilg pot, availability, cost etc., Afte the consideation of these factos, Steaic Acid is selected as PCM fo pesent wok. The function of the PCM is to absob the heat enegy fom the suface of exhaust gas flow type. Afte gag the sufficient heat enegy it changes its phase fom solid to liquid and aga convets to solid phase afte eleasg heat enegy. 2016, IRJET Impact Facto value: 4.45 ISO 9001:2008 Cetified Jounal Page 1613

2 1.3 Paaff popeties The nomal paaff s of type CnH2n+2 ae a family of satuated hydocabons with vey simila popeties. Paaff s between C5 and C15 ae liquids and the est ae waxy solids. Paaff waxes the maly used commecial oganic heat stoage PCM. Paaff s have no tendencies to supe cool, so nucleatg agents ae not necessay. Paaff s ae chemically stable. Paaff waxes show high heats of fusion. Table 1: Themo-physical popeties of PCMs Phase Change Mateial Paaff Steai Meltg Tempeatue C Latent heat of fusion (kj/kg) followg vaiables ae studied. by tegatg with constant let heat souce. In this pocess the effect of followg vaiables ae studied, Phase Change Mateials (PCM) Steai and Paaff wax Mass flow ates of Heat Tansfe Fluid (HTF) 2lit/m and 4 lit/m. Above vaiables ae studied two diffeent stages: 1. Chagg pocess. 2. Dischagg Pocess. 2.1 Test Rig Density Solid (kg/m Specific (J/kg C) heat Liquid Solid Liquid Themal Conductivity (W/m Solid Liquid Extended sufaces (Fs) Fig1: Expeimental Setup In the heat tansfe study, the suface that extends fom an object is known as a f. This is used to cease the ate of heat dissipation fom o to the envionment by ceasg the ate of convection. The total of convection, conduction, o adiation of an object decides the amount of heat it dissipates. It ceases with the diffeence of tempeatue between the envionment and the object, also ceasg the convection coefficient of heat tansfe, o ceasg the suface aea. 2. EXPERIMENTAL SETUP AND DESIGN DETAILS A TES system is tended and evaluated fo its themal pefomance obsevance that the system should be able to supply hot wate at an aveage tempeatue of 45 C fo domestic use geneal. The themal pefomance of the system is vestigated by wate with f. Both chagg and dischagg expeiments ae caied out fo evaluatg the pefomance of the system. by tegatg with constant let heat souce. In this pocess the effect of Fig2: le diagam of Expeimental Setup 1. Electic heate; 2. Constant tempeatue bath (wate stoage tank); 3 & 8 Flow contol valves; 4. Flow mete;5. Distibute; 6. TES Tank; 7. PCM capsules; 9. Outlet tank; 10. Digital themomete. 2016, IRJET Impact Facto value: 4.45 ISO 9001:2008 Cetified Jounal Page 1614

3 The above fig. Shows the set-up used the study of themal pefomance of TES system usg latent heat and sensible heat of the PCMs. In pesent system Investigations ae caied out to impove the pefomance of the system, fs ae aanged to the PCM stoage spheical capsule fally the stoage tank is sulated to educe the heat tansfe losses like conduction, convection, adiation losses PCMs stoage spheical capsules Stoage tank Fig5: Insulated with themocole Fig3: Spheical capsule without f Fig6: stoage tank with spheical ball Fig4: Spheical capsule with f () The test ig shows the set-up used the study of themal pefomance of TES system usg latent heat and sensible heat of the PCMsthis consists of an sulated TES tank, which contas PCM capsules (spheical capsules), flow mete and wate stoage tank. The TES tank has a capacity of 5 littes. The stoage tank is sulated with glass wool of 50mm thick and side of the stoage tank is sulated with themocole of 3 mm thick. The stei and paaffwax ae used as PCMs. Wate is used asboth SHS mateial and HTF.A flow mete with an accuacy of ±2% is used to measue the flow ate of HTF and the flow ate is changedby diffeent tap opengs. The TES tank is copoated with digital themometes with an accuacy of ±1 C isplaced above the TES tank to measue the tempeatues of HTF and PCM stoed side the capsules. An electicwate heate is used to mata the constant tempeatue the wate stoage tank. 2016, IRJET Impact Facto value: 4.45 ISO 9001:2008 Cetified Jounal Page 1615

4 2.2 Expeimental Pocedue Chagg pocess The heat is tansfeed to o fom HTF as it flows on the spheical capsule. Dug chagg the hot HTF is ted though the tank by the pump employed the cicuit. The PCM side the capsules absobs heat and melts. The diffeence between the mean tempeatue of HTF and PCM must be sufficient to obta a satisfactoy ate of heat tansfe. Dug this pocess at vaious levels the HTF tempeatue and PCM tempeatues ae noted. Afte the tank is filled, the outlet valve is opened and adjusted such that the wate level the tank is mataed constant. The tion of HTF is contued at the given flow ate, till the same tempeatue is attaed by the PCM. The chagg expeiments ae conducted fo the HTF at 2lit/m, 4 lit/m. The chagg expeiments ae epeated fo the mild steel spheical capsule with f () and without f Dischagg pocess The pocess can be by contuous/batch wise pocess. Howeve, it is epoted the liteatue that batch wise pocess is moe effective whee the equiement is temittent. A ceta quantity of hot wate (5 Lit) is withdawn fom TES tank and the tank is aga filled with cold wate of quantity equal to the amount of wate withdawn. This fixed quantity of 5 lit of wate which is withdawn fom the TES tank to facilitate fillg up of fesh cold wate is temed as batch. Afte a time teval of 20 mutes allowg fo tansfe of enegy fom PCM, anothe batch of 5 lit of wate is withdawn fom the TES tank. This pocess is contued until the aveage tempeatue of the complete amount of wate withdawn is about 45 C. 3 Numeical Studies: A themal enegy stoage system is designed and evaluated fo its themal pefomance. The themal pefomance of the system is evaluated based on the heat enegy etieval fom the system. In this the theoetical calculations ae caied out fo evaluatg the pefomance of the system. Total volume consideed fo the steai = 1.4lit Mass of the PCM (m st) = Density volume = m st = kg Total heat of PCM stoed spheical capsule is Q = (m stc pδt) solid+( m stl)+( m stc p Δt) liquid Whee, m s t = mass of steai c p = specific heat of steai Δt L = tempeatue diffeence = Latent heat of fusion Q = Q st= 0.377MJ Mass of the paaff wax Volume of the ball = 1.6 lit Cleaance volume of the ball = 0.2lit Total volume consideed fo the Paaff = 1.4lit Mass of the PCM (m pw) = Density volume = m pw = kg Total heat of Paaff stoed spheical capsule is Q = (m pwc p Δt ) solid+( m pwl)+( m pwc p Δt) liquid Whee, m pw = mass of Paaff c p = specific heat of Paaff Δt = tempeatue diffeence 3.1 Calculation Pocedue L = Latent heat of fusion Mass of the steai Q = = 0.36MJ Volume of the ball = 1.6 lit Cleaance volume of the ball = 0.2lit 2016, IRJET Impact Facto value: 4.45 ISO 9001:2008 Cetified Jounal Page 1616

5 3.1.3 Mass flow ate of HTF Mass flow ate of wate = density of wate flow ate Flow ate of HTF when it is 2lit/m Mass flow ate = ( ) 60 m htf = kg/sec Flow ate of HTF when it is 4lit/m Table 2: Summay of numeical esults and expeimental values s.n o Types of PCMs F type Flow ate of HTF (lit/ m) Chagi ng time (ms) Q (MJ) Qpcm (MJ) Qout (MJ) ɳ(%) Mass flow ate = ( ) 60 m htf = kg/sec. 3.2 Calculation of amount of Heat tansfe and Efficiency of TES system Heat tansfe and efficiency of PCM(steai) based TES systemwith Cicula f by usg wate as HTF when the flow ate is 2lit/m: Total time duation fo chagg pocess =140m Mass flow ate of HTF m htf = kg/sec Specific heat c p = 4.187kj/kg k Tempeatue diffeence Δt = T -T out Heat put of HTF (Q) = mc pδt Q = (80-79)= j/s. Total heat put of HTF (Q )= heat put total time duation Q = = 1.171MJ 1 Steai 2 Steai 3 Steai 4 Steai 5 Paaff 6 Paaff NA f NA f NA NA Heat output of HTF (Q out) =Total heat put of HTF- Total heat of steai. Q out = Q -Q st = Paaff f Q out= 0.794MJ Efficiency of the TES system 8 Paaff f Efficiency of the TES system ( ɳ ) = (Q -Q out) (Q ) ɳ = ( )/1.171 ɳ= 32.17% 4. RESULTS AND DISCUSSION 4.1 Effect of PCM The expeiment is caied fo diffeent PCMs like steai and paaff wax and the effect of this PCM on heat tansfe is illustated usg the gaph shown fig. 2016, IRJET Impact Facto value: 4.45 ISO 9001:2008 Cetified Jounal Page 1617

6 4.3 Effect of Fs The expeiment is caied out to impove the pefomance of the system by usg fs fo the PCM stoed spheical capsules due to this the suface aea will be impoved and the esults ae shown by usg the gaphs. Gaph 1: Tempeatue Vaiation of PCM Spheical capsule without f and flow ate is 2 lit/m Fom the above figues shows the elation between chagg time and PCM tempeatue fo paaff and steai. The chagg time of steai is 12% less compaed to that of paaff. This is due to the fluence of themal popeties of steai. 4.2 Effect of flow ate The expeiment is caied fo diffeent flow ates like 2lit/m, 4 lit/m and the effect of this flow ate on heat tansfe is illustated usg the gaph shown. Gaph 3: Tempeatue Vaiation of PCM Spheical capsule with and without f and PCM as steai (2lit/m): It is obseved fom the above gaphs that the chagg time deceases by usg of extended sufaces i.e., the contact suface aea is ceases fo the spheical capsules so it cease the ate of heat tansfe fom the system. It ceases with the diffeence of tempeatue between the system and the object, also ceasg the convection coefficient of heat tansfe. This causes eduction chagg time with ceased suface aea. 5. CONCLUSION Gaph 2: Tempeatue Vaiation of PCM Spheical capsule without f PCM as steai It is obseved fom the above gaphs that the chagg time deceases with the cease mass flow ate fom 2 to 4lit/m. This is because as the mass flow ate is ceased, the themal enegy supplied to the TES tank though HTF a given time ceases and as thee always exists a tempeatue diffeence between HTF and PCM. This causes eduction chagg time with ceased mass flow ates. A TES system is developed fo the supply of hot wate at an aveage tempeatue of 45 C fo vaious applications such as wate heatg, ai heatg, buildg applications, ptg on the cotton cloths and dyg the theads and cleang of utensils etc. Expeiments wee conducted on the TES unit to study its pefomance by tegatg it with constant heat souce. The vaiables studied clude PCMS, mass flow ate and extended sufaces (FINS), on the pefomance of TES. Fom the expeimental esults it is concluded Out of the two PCMs used the expeiments, steai attas maximum tempeatue (equal to HTF let tempeatue) faste compaed to paaff. This is due to the phase change tempeatue and latent heat of steai beg less compaed to paaff and by ceasg the mass flow ate, the themal enegy supplied to the TES tank though HTF a given time ceases so the chagg times can be educed. 2016, IRJET Impact Facto value: 4.45 ISO 9001:2008 Cetified Jounal Page 1618

7 By usg extended sufaces the contact suface aea is ceases fo the spheical capsules so it ceases the ate of heat tansfe fom the system. Hence, it is concluded that by chagg times can be educed by usg of extended sufaces. 5.1 SCOPE OF FUTURE WORK In place of PCM beg used the spheical capsules, PCM based nano paticles may be employed. To cease heat tansfe ate HTF, low density nano paticles may be employed, it may give bette esults. To educe the heat tansfe losses pefect sulation povided to the TES system. 6. REFERENCES 1. D. R. Meenakshi Reddy "Sola enegy based themal enegy stoage system usg phase change mateials" Intenational Jounal on Renewable enegy Vol 3, No.1, R.Meenakshi Reddy et al. (2010) An vestigation of the effect of PCM capsule mateial on themal enegy stoage systems Int. Jounal of Ulta Scientist of Physical Sciences, Vol. 22, No.l, pp Afif Hasan., Themal enegy stoage system with steai as phase change mateial Enegy Convesion and Management, Vol.35, Issue 10, 1994, pp BIOGRAPHIES Student, M.Tech Themal Sciences and Enegy Systems G. Pulla Reddy Engeeg College (Autonomous), Kunool, A.P, India. Associate Pofesso, Mechanical Engeeg, G. Pulla Reddy Engeeg College (Autonomous), Kunool, A.P, India. Assistant Pofesso, Mechanical Engeeg, G. Pulla Reddy Engeeg College (Autonomous), Kunool, A.P, India. Student, M.Tech Themal Sciences and Enegy Systems G. Pulla Reddy Engeeg College (Autonomous), Kunool, A.P, India. Mobile: Saitoh, T., Hiose, K., High pefomance phase-change themal enegy stoage usg spheical capsules. Chemical Engg.Commun, 41: K. A. R. Ismail and J. R. Heniquez, Numeical and expeimental study of spheical capsules packed bed latent heat stoage system, Applied Themal Engeeg, 22 (2002), Y. Shia and T. Inagaki, Study on the efficiency of effective themal conductivities on meltg chaacteistics of latent heat stoage capsules, Intenational Jounal of Heat and MassTansfe, 48 (2005), , IRJET Impact Facto value: 4.45 ISO 9001:2008 Cetified Jounal Page 1619