Performance Prediction of Solar Thermal Parabolic Trough Concentrator System (STPTCS) by Enhancement of Heat Transfer

Transcription

1 ISSN (Online) 3 4 ISSN (Print) Vol. 3, Issue 9, Setember 5 Performance Prediction of Solar hermal Parabolic rough Concentrator System (SPCS) by Enhancement of Heat ransfer Y.. Nayak, U.. Sinha, Nilesh umar 3, P. umar 4 Ph.D. Research Scholar of EED, N. I.. Jamshedur, 3 Associate Professor, EED, N. I.. Jamshedur, 4 Abstract: Performance rediction of SPCS has been studied by enhancement of heat transfer rate using nanofluid, lain tisted tae and nail tisted tae inserts. Nanofluid and tisted tae inserts based SPCS are commonly used in the area as such as industries, heating and cooling for buildings, thermal oer lants, solar cooker, automobiles etc. his aer rovides enhancement and erformance rediction in heat transfer in absorber tube of concentrator using nanofluid and tisted tae inserts. he results obtained by simulation using C++ rogram. eyords: Solar hermal Parabolic rough Collector/Concentrator System (SPCS), Nanofluid, isted ae Insert, Heat ransfer, Heating and Cooling, Friction factor. NOMENCLAURE A Surface area, m C P Secific heat caacity, J/kg D Diameter of coer tube, m d n Diameter of nail f Friction factor h Convective heat transfer co-efficient, W/m h dn Head diameter of nail I Current (A) k hermal conductivity, W/m l n Length of nail m Mass flo rate, kg/s Nu Nusselt number Q Heat transfer rate, W q Heat inut, W q Heat flux, W/m Re Reynolds number emerature, V Voltage, (V) Greek symbols Ρ Density, kg/m3 φ Particle volume concentration (%) μ Dynamic Viscosity (kg/m.s) Subscrits f Base fluid Nanofluids Particle W. INRODUCION Solar technologies can be used for a variety of alication such as generation of electricity, steam generation, and sometimes air cooling and heating systems. Parabolic trough collector/concentrator has obtained ide oularity in the solar technologies. Many researchers have tested several tyes of heat transfer fluid in SPCS, e.g., mineral oils, silicones, heavy aromatic oils, and molten salts. Parabolic-trough solar ater heating and cooling systems have they achieved quit reasonable efficiency in converting solar radiation into useful heat of a heat transfer fluid studied by alogirou S. et al., [,,3]. A series of research have been conducted at Argonne National Laboratory of USA that the conventional fluid thermal erformance could be imroved using nanofluids and tisted tae inserts. he use of conventional fluids in solar collectors has very lo efficiency as comared to nanofluids and tisted tae inserts.. NANOFLUIDS AND WISED APE INSERS he rise in effective thermal conductivity is most imortant in imroving the heat transfer behaviour of fluids. he tisted tae inserts has also lays key role, for forced convection the heat transfer coefficient for absorbing tubes deends on many hysical arameters concerned to the fluid and system through hich the fluid if floing and heating. here arameters include the roerties of the fluid such as its density, viscosity, thermal conductivity and secific heat along ith extrinsic system arameters such as tube diameter, length and average fluid velocity. he effective utilization and uses of nanofluids in heat exchanges as a heat transfer fluids. here are many advantages of nanofluids in erformance enhancement of the heat transfer and they are as belo Due to nano size articles, ressure dro is minimum. Due to higher thermal conductivity of nano articles (fluid) ill increase the heat transfer rate. Nanofluids ill lead to lights and smaller heat exchanger. Heat transfer rate increases due to large surface area of nano articles in the base fluid. Due to above characteristics of the nanofluids it is most suitable for raid heating and cooling. Coyright to IJIREEICE DOI.748/IJIREEICE

2 ISSN (Online) 3 4 ISSN (Print) Vol. 3, Issue 9, Setember 5 he tisted taes are made of aluminium and have tae x of.5 mm and idth of mm, tae thickness tae length l of mm. the size of tisted tae may increase or decrease deending uon the design of the model for exerimental or simulation urose. he use of tisted tae for enhancement of heat transfer rate and ressure dros. A comarative study of thermal erformance of an ordinary full idth full length tisted taes having modified surface coiguration as reresented by Monheit [4]. Dasmahaatra and Rao [5], had studied augmentation of heat transfer to viscous non- Netonian fluids in laminar flo using full idth interruted tisted tae under the uniform all temerature condition. Nasrin and Alim [6], investigated numerically the flo and heat transfer henomena of different nanofluids, and comared their erformances inside a solar collector, and reorted that the Ag/ater nanofluid are to be more effective in enhancing erformance of heat transfer rate than that of CuO/ater nanofluid. Lalundan and Sharma [7], have investigated the CuO-ater based nanofluid in the solar collector, it increases efficiency comared to ater. By Farajollahi et al. [8], it has been investigated that the Bronian motion occurs hen article volume concentration is more than otimum value of %. herefore, it is exected that the heat transfer coefficient may decrease hen the article volume concentration is more than the otimum value. Suresh et al. [9] also studies that the nano articles susended in ater increases the Nusselt number even for a very lo volume concentration of.3%. In this study. and.3% volume concentration of nanofluid ere investigated and comared ith ater. Risi et al. [] reorted that the erformance of solar transarent arabolic trough collector orking ith gas based ith CuO and nanofluids. he maximum thermal efficiency of 6.5% for a nanofluid ith an out let temerature of 65 C at.3% volume concentration as reorted. In the above several researchers ere studies and carried out for solar heating system using nanofluid in turbulent regions and their results indicated a small decrease in all temerature on the heating absorber surface can cause a great increase of the absorbing solar energy in the solar collector. In the resent ork the exerimental heat transfer and ressure dro results of the nanofluids (ater Al and 3 ) assing through the receiver ith tisted Where tae insert of SPCS under laminar flo condition. tanks O 3. MODEL OF HE SPCS he schematic diagram of the SPCS Fig. is mainly consisted of a test section, rota meter, a um unit, a oer source and cooling ater circulation system ith chiller. he coer tube ith 3 mm long and 5 mm diameter like the absorber tube of PC solar collector. he tisted taes are made of aluminium and have tae idth of mm; tae thickness of.5 mm and tae length of mm. Nail tisted tae as obtained by unching small holes in the lain tisted tae and carefully inserts nails. In this study, deionized ater and ater nano fluids at different volume concentration i.e..,. and.3 % ere used as the orking fluid. Nano articles ere commercial roducts. In the above rearation to get a uniform disersion and stable susension, hich determine the final roerties of nano fluids, the nano fluids are ket under ultrasonic vibration continuously for 6 hours. 4. HERMO PHYSICAL PROPERIES OF NANOFLUIDS he thermo-hysical roerties of nanofluids such as secific heat and density at different concentrations are calculated as belo c c c,, he effective thermal conductivity of dilute nanofluids can also be evaluated using the Maxell model for nanofluids ith volume fraction less than unity. Maxell equation is given by s s S S k k 5. HEA RANSFER CALCULAION (3) he heat flux sulied to the absorber section and energy observed by the floing fluidis calculated from equations (4) and (5) as belo: q V q mc I 4 (5) out he average heat transfer coefficient may be obtained by h q '' b in 6 and b are the mean alls and bulk fluid Where all is the `local all temerature evaluated at outer all surface of tube. No, he Nusselt Number can also be determined from the ell knon shah equation for laminar flo under constant heat flux boundary condition is in reasonable agreement. N u.953 Re Pr d x 3 for Re Pr d x he average Nusselt number is calculated as Coyright to IJIREEICE DOI.748/IJIREEICE

3 Nusselt number (Nu) ISSN (Online) 3 4 ISSN (Print) Vol. 3, Issue 9, Setember 5 N u h Di he Reynolds number is given by Re V D i PRESSURE DROP CALCULAION he ressure dro P measured across the test section under isothermal condition is used to determine the friction (f) using the relation f P V D L P V fl / D 7. RESUL AND DISCUSSIONS 7. Heat ransfer Performances and Pressure dro characteristics Nusselt number of ater and other volume concentration nanofluid in a lain tube ith tisted tae inserts shon in figure- and figure- resectively. 7.. Effect of Reynolds Number on Nusselt Number in Plain tube and Plain isted ae he variation of Nusselt number for ater and nanofluids in lain tube and lain tisted tae are shon in Fig.. From the lot, it is clear that the Nusselt number sloly increases as Reynolds number increases for different volume concentration ratio and highest for volume concentration.3% and loest for ater. 7.. Effect of Reynolds Number on Nusselt Number in Plain tube and ith various isted ae inserts he variation of Nusselt number for ater and nanofluids in lain tube and various lain tisted tae inserts are shon Fig.. he Fig. shos the variation of Nusselt number ith Reynolds number for ater and nanofluid in lain tube and various tisted tae inserts and it is found that the variation on Nusselt number ith Reynolds number is uniform in all the cases but loest for loer volume concentration and vice versa ReynoldsNumber (Re) 7..3Effect of Reynolds number on Friction Factor in lain tube and various tisted tae It has been observed that the Nusselt number reasonably increased ith increase in Reynolds number. he simulated result also reveal that the nail tisted tae (N- ) result in a higher Nusselt number than lain tisted tae. his can be recognized as the fact that the nails act as turbulent and give intensive mixing of nanofluid that romotes the turbulence near the tube all surface that break the boundary layer at the surface hich enhance the heat transfer and ressure gradient might be created along the radial direction hile the P- causes sirl flo only. In addition to the above, various use of the considered in the resent simulation lead to further heat transfer enhancement, increase of ressure dro and hence increase in uming oer. he reason for higher ressure dro has the dissiation of dynamic ressure of the fluid due to high viscosity loss near the tube all. hroughout the simulated results, it is the fact that the nanofluid of.% volume concentration ith N- (y=) gave the higher volume of heat transfer comared ith the other data. his is only due to increase in shear force on tube all ith the activity of larger number of nanoarticles. he maximum increase in Nusselt number as observed to be 8% hen nanofluid ith.3% volume concentration is used comared ith distilled ater in a lain tube. he maximum enhancement in Nusselt number is about % hen nanofluid ith.3% volume concentration is used ith N- tube. he friction factor of ater and different volume concentration nanofluid in a lain tube ith tisted tae insert is shon in Fig. 3 and Fig. 4 resectively. he simulated result sho the significant increase of friction factor ith increase in volume concentration of nanoarticles. It is also clear that a very high friction factor is only due to use of nanofluid and tisted tae inserts, but very lo friction factor in case of lain tube and ater used as fluid. In general, it is obvious that the volume concentration increases the surface area that affect considerably the ressure losses in the fluid flo due to increase in disturbance of laminar layer of the boundary layer. Figure : Variation of Nusselt number ith Reynolds in lain tube and lain tisted tae AlO3.% AlO3.3% Y= Y=3 Coyright to IJIREEICE DOI.748/IJIREEICE

4 Friction factor (f) Friction Factor (f) Nusselt number (Nu) ISSN (Online) 3 4 ISSN (Print) Vol. 3, Issue 9, Setember Reynolds number (Re) Y=3 AlO3=.% Y=3 AlO3=.3% Y= AlO3=.% Y= AlO3=.3% Y=3AlO3=.% (N-) Figure : Variation of Nusselt number ith Reynolds number in lain tube and ith various tisted taes AlO3.% AlO3.3% Y= Y= ReynoldsNumber (Re) Figure 3: Variation of friction factor ith Reynolds number for ater and nanofluid in lain tube and lain tisted tae Reynolds number (Re) Y=3 AlO3=.% Y=3 AlO3=.3% Y= AlO3=.% Y= AlO3=.3% Y=3AlO3=.% (N-) Y=3 AlO3=.3% (N-) Figure 4: Variation of friction factor ith Reynolds number for ater and nanofluid in lain tube and ith various tisted taes Coyright to IJIREEICE DOI.748/IJIREEICE

5 ISSN (Online) 3 4 ISSN (Print) Vol. 3, Issue 9, Setember 5 9. CONCLUSIONS he simulated results for erformance rediction of SPCS ere carried out and lead to the folloing conclusions: he simulation ork have been carried out for heat transfer and friction factor to investigate the erformance in absorber tube (on hich solar radiation concentrated) for laminar flo ( i.e. for R e < ) using ater/al O 3 nanofluid as orking fluid ith volume concentration of.% and.3% ith lain tube and lain tisted tae resectively. he authors conclude the folloing: On the basis of simulated results, it has been concluded that he higher Nusselt number considerably increases ith increase in the volume concentration of nanofluid. Heat transfer rate consequently increased due to tisted tae and varying volume concentration of nanofluid. he heat transfer rate increases ith increase in tae tist u to a certain value. Friction factor initially decreases raidly ith increase in Reynolds number for various tisted tae inserts in the absorber tubes. Nanofluid enhances the heat transfer co-efficient ith normal enhancement in ressure dro as comared to ater. he ressure dro significantly occurs hen tisted tae inserts in absorber tube due to interaction in the inertial force and ressure forces on the boundary layer. he most imortant findings of this investigation are that the use of nanofluid ith.3% volume concentration and nail tisted taes (N-) gives the higher Nusselt Number and high friction factor. REFERENCES ) alogirou S., Eleftheriou P., Lloyd S., and Ward J., 994. Design and erformance characteristics of a arabolic trough solarcollector system. Alied Energy 47: ) alogirou S., 996. Parabolic-trough collector system for lo temerature steam generation- design and erformance characteristics. Alied Energy 55: -9. 3) Odeh S.D., Morrison G.L. and Behnia M., 998. Modelling of arabolic through direct steam generation solar collectors. Solar Energy 6 (6): ) Monheit. M, 987. Exerimental evaluation of the convective characteristics of tubes ith tisted tae inserts, Advances in Enhanced Heat ransfer, AMSE, Ne York,. 8. 5) Dasmahaatra J., and Raja Rao M, 99. Laminar Flo heat transfer to generalized oer la fluids inside circular tubes fitted ith regularly saced tisted tae elements for uniform all temerature condition, Fundamentals of Heat ransfer in Non- Netonian Fluids, ASME, Ne York, ) Nasrin R. and M.A. Alim. 3. Performance of nanofluids on heat transfer in a avy solar collector. International Journal of Engineering, Science and echnology 5(3): ) undan L. and P. Sharma. 3. Performance evaluation of a nanofluid (CuO-HO) based lo flux solar collector. International Journal of Engineering Research (): 8-. 8) Farajollahi B., EtemadS.Gh. And Hojjat M.,. Heat transfer of nanofluids in a shell and tube heat exchanger. International Journal of Heat and Mass ransfer 53(-3): -7. 9) Suresh S., Chandrasekhar M. and Selvakumar P.,. Exerimental studies on heat transfer and friction factor characteristics of AlO3/ater nanofluid under laminar flo ith siraled rod inserts. International Journal of Nanoarticles 5(): ) De Risi A., Milanese M. and Laforgia D., 3. Modeling and Otimization of ransarent Parabolic rough Collector based on gas hase nanofluid. Reneable Energy 58: Coyright to IJIREEICE DOI.748/IJIREEICE