ISSN : (Print) INVESTIGATION OF USING DIFFERENT FLUIDS FOR USING IN GAS TURBINE- RANKINE CYCLE

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1 Indian J.Sci.Res.1(2) : 74-81, 2014 ISSN: (Online) ISSN : (Print) INVESTIGATION OF USING DIFFERENT FLUIDS FOR USING IN GAS TURBINE- RANKINE CYCLE MOHAMMAD JAMAL ABADI a, PAYAM HOOSHMAND 1b, BEHROOZ KHEZRI c, AMIR REZA RADMANESH d a Chabahar maritime university, Iran b Young Researchers and Elite Club, Mahabad Branch, Islamic Azad University Mahabad, Iran c Islamic Azad University, Chemistry Faculty, Mahabad Branch, Iran d Deartment of mechanical Engineering, Sharif University of technology, kish, Iran ABSTRACT Use of different organic fluids in Organic Rankine Cycle is investigated as hybrid cycle with Gas Turbine. Analysis shows a first and second law of thermodynamics for fourteen Organic fluids. Viable results have been obtained for R245fa, roane and R152a ORC combined cycles, with reasonably high global efficiencies for low temeratures and for temerature more than 100 C results demonstrate that GT/ORC using R113 shows the maximum efficiency. KEYWORDS: Combine Cycle, Thermodynamics Analysis, Organic Rankine Cycle, Gas Turbine, Second Law. Several industrial rocesses have low-temerature waste heat sources that cannot be efficiently recovered. Because of lack of efficient and economic recovery methods, in some industries low waste heat has generally been ignored and these have damages for environment as heat ollution. One method to solve this roblem is using the lowtemerature Rankine cycle that uses the organic fluid as a working fluid in the cycle. To roduce the ower from a gas turbine based combined cycles, virtually all bottoming cycles are Rankine cycles with steam due to very attractive features such as good thermal integration with the toing gas turbine cycle, high reliability and considerable ast industry exerience. The Organic Rankine Cycle is a Rankine thermodynamic ower cycle that uses an Organic fluid to generate electricity. The working fluid is heated in heat exchanger, and converting into vaor which is used to drive a turbine. This turbine can be used to drive a generator to convert the work into electricity or to drive rotary equiment. The working fluid vaor is condensed back into the liquid and reused in the cycle. A schematic of a simle ORC system is shown in Fig. 1. Fig. 1. Schematic of ORC system One advantage of using ORCs instead the steam Rankine cycle is that the thermal efficiency becomes economically feasible when Organic fluids are used to recover waste heat at T<300 C. ORCs can be alied to a low-temerature waste heat recovery in some industries, to increase the efficiency imrovement in ower station (esecially ower station with less than 20MW), and to recover the heat from geothermal sources and solar heat. The organic Rankine cycle has many ossible alications. Among them, the most widesread and romising fields are the waste heat recovery, the biomass ower lant, the geothermal lants, and the solar thermal ower (Quoilin and Lemort, 2009). Here we focused on the alications of ORCs in the waste heat recovery of gas turbine (less than 20MW). Considering the fact that there are many low ower gas turbines in um stations (oil or water um station), using ORC in this case and also to test the various fluids on erformance of ORCs lonely and the cycle as a whole, is reviewed. There are a wide collection of organic fluids that can be used in ORC. Proerties and characteristics of different working fluids for waste heat recovery system can be found in references (Najjar, 2001; Chacartegui et al., 2009). Generally, a good working fluid should exhibit low toxicity, good material comatibility, fluid stability limits, low flammability, corrosion and fouling characteristics. Another characteristic must be considered during the selection of an organic fluid is the saturation vaor curve. This characteristic affects the fluid alicability, cycle efficiency, and arrangement of associated equiment in a ower generation system. The sloe of the saturation curve in T-S diagram deends on the tye of the emloyed fluid. There are three kinds of organic fluids in ORC: dry fluids with ositive sloe; wet fluids with negative sloe; and isentroic fluids with infinite large sloe. The schematic of these three kinds of fluids emloyed in ORC is 1 Corresonding author

2 shown in Fig. 2. It is can be seen that wet fluids are converted into two hases in the entrance of the condenser; Dry fluids in the entrance of the condenser remain suerheated and isentroic fluid remain in the saturate condition. it is desirable fluids not to be in the suerheat condition in the entrance to the condenser. In the calculations of the cycle, it is roved that dry fluids yield the best results. Fig. 2. Schematic of 3 kind of Working Fluid a) Isentroic b) Wet and c) Dry [Ref. 16] The working fluids emloyed in this investigation are classified as follow: R152a, R134a, R12, R22, RC318, R143a, R32, R125 and roane are wet Fluids. R245fa, R245ca, R236fa, R236ea and R113 are dry fluids. While R12 and R22 can be assumed wet and isentroic fluids. Fig. 3 Illustrates the T-S diagram of such hybrid cycle of GT/ORC. This cycle in Fig. 3 is alicable to all the analysis shown in this aer. Fig. 3. Schematic of hybrid cycle GT/ORC and T-S diagram for dry and wet fluids In the low temerature range, bottoming Organic Rankine Cycles (ORC) constitute another alternative, having shown good thermodynamic erformance for low maximum temerature bottoming cycles (Manolakos et al, 2009; Gurgency, 1986). This interest in organic working fluids for low temerature Rankine cycles is not new and it has been roosed for different alications: renewable energy and low temerature heat recovery [7 20]. Moreover, small-scale ORC ower lants are resently commercially available (Mago et al., 2006). Some of the researchers who have investigated the alication and erformance of ORC are Manolakos et al. (2009) roosed the use of ORC technology for seawater desalination, Hung et al (1997; 2001), Dai et al (2009), Gurgency (1986), Lee et al (1998), Wei et al, (2007), Vijayaraghavan and Goswami (2005), Maizza (1996, 2001), studied an analyzed the erformance of ORC for waste heat recovery. In view of increasing the system efficiency, Mago et al. (2006), Fankam Tchanche et al (2009), and Kaushik et al. (1994) assessed modified ORC configuration. Yamamoto et al. (2001) and Saleh et al. (2007) are some of the researchers who analyzed the characteristics of different fluids in view of their selection in an ORC alication. ORCs bottoming cycles in combined ower lants have been roosed reviously by Najjar (Najjar, 2001), who scrutinized a combination of ORC fluids and cycle layouts, and Chacartegui et al (2008, 2009) changed it to use for intermediate temerature thermo solar ower lants. Invernizzi et al. (2003), Caresana et al. (2002), and yari (2001) used ORC for microturbine combined cycles. The aer is structured in four main arts. First, a review of ORC cycle and their alications, and then a thermodynamic analysis of combined cycles with Gas Turbine and ORC are resented. A arametric analysis of a Gas Turbine combined ORC is erformed in order to achieve a better integration between these two technologies in the third section and at the end best fluids for different range temerature are selected. In this aer, all simulations were rogrammed with Delhi Main algorithm is based on following equations and used databases were achieved from NIST 7 software. SYSTEM MODELING The resented ORC system consists of heat exchangers, a turbine, a condenser and a um. The equations used to determine the cycle efficiencies such as cycle irreversibility of ORC are resented in this section. Using the first and second laws of thermodynamics, the erformance of an ORC can be Indian J.Sci.Res.1(2) : 74-81,

3 evaluated under diverse working conditions for different working fluids. Modeling resented in this article is assumed to be in a steady-state condition with no ressure dros in the evaorator, condenser, and ies. Also isentroic efficiencies for the turbine and the um are considered while the internal irreversibility is ignored. The resented Gas Turbine system considered in this article is a simle GT that used in Iranian Oil Pieline and Telecommunication Comany (IOPTC). The assumtions of the GT cycle are like that of the ORC. The equations obtained for ORC system are summarized below. Turbine. & t = W& t, ideal η t = m& ( h3 h4 s ) ηη t m = m& ( h3 h4) η m (1) W We know that ds system =0. dt For the turbine, the irreversibility rate can be exressed as & (2) I t ( ) = T m& o s 4 s 3 Condenser & (3) Q c = m& = Tom ( ) h 1 h 4 h 1 h ( s1 s4) & (4) 4 I &. c TL Evaorator & (5) Q e = m& = T m& ( ) h 3 h 2 h 3 h ( s3 s2) & (6) 2 Ie o TH Pum ( h h ) & W, ideal m 1 2s = = (7) η η W I & = T m& o & ( ) & (8) s 2 s 1 First law efficiency W& t + W& η th = (9) Q& e SECOND LAW EFFICIENCY The second-law efficiency can be calculated using the following equation W& net ηth ηii = = (10) T L TL Q& e 1 1 TH TH The arameters of the considered secial Gas Turbine is given in Table 1. Table 1. Main characters of gas turbine (solar4500) Mass flow rate 17.9 kg/sec Pressure ratio 10 Turbine inlet temerature 980 C Turbine outlet temerature 425 C Net ower 3634 KW Thermal efficiency 28.3% RESULT AND DISCUSSION For the urose of this study, fourteen organic fluids with different roerties in three grous (due to the alicable temerature range) were emloyed. These organic fluids are R152a, R134a, R12, R22, RC318, R143a, R32, R125 and roane (wet Fluids) and R245fa, R245ca, R236fa, R236ea and R113 (dry fluids). The results for the different organic fluids were comared together in three grous. Some of the roerties of the fluids used in this investigation are resented in Table 2. Table 2. Physical and Critical roerties of working fluids Substance Critical oint Physical data Temerature C Pressure MPa Kg/Mol 1 R152a R134a R R RC Proane Indian J.Sci.Res.1(2) : 74-81,

4 7 R143a R R R245fa R245ca R236fa R236ea R RESULT FOR ORC SYSTEM The oerating conditions of the ORC are given below with the characteristics of the turbine and the um. First, the arameters of ORC system were considered. The overall oerating conditions of ORC system are given as below: Low temerature (temerature of condenser) is constant at 30 C. High temerature (temerature of evaorator) is varied from 60 C to vaorization temerature of every working fluid. The isentroic efficiencies of the turbine and the um were both 85 ercent. The mechanical efficiencies of the turbine and the generator and couling are assumed to be around 85 ercent. The behavior of the working fluid is assumed to be real. The oerating conditions of the GT system are as below: The temerature and the ressure of the GT in all oints are suosed to be constant. The isentroic efficiencies of the turbine and the comressor were 82 and 85 ercent resectively. CYCLE EFFICIENCY The system thermal efficiency ranged from 5.66% for RC318 to 18.28% for R113, Fig. 4 shows the effects of the variation of the turbine inlet temerature. The temerature difference is maintained constant at 10 C and the vaor at the turbine inlet is saturated. Generally, the system thermal efficiency increases by raising the turbine inlet temerature. The high temerature ranges of the dry fluids are more than wet fluids; therefore for conditions with high temerature, the dry fluids are more interested. For temerature below 100 C, fluids such as R236fa, R245ca, R236ea, R245fa, Proane, RC318, R113, R22, R12, R134a, R152a, have a similar thermal efficiency. Fig. 4. System thermal efficiency versus turbine inlet temerature for working fluids in three grous A, B and C The second law efficiency varies from % for R236ea to % for R113. The effect of the turbine inlet temerature on the system second law efficiency can be seen in Fig. 5. For the third grou (dry fluids), the second law efficiency is become maximum, between temeratures 120 C to 160 C and then decreases. So in temerature less than 76 C, R125 and R143a have a minimum amount. Indian J.Sci.Res.1(2) : 74-81,

5 Fig. 5. System second law efficiency versus turbine inlet temerature for working fluids in three grous A, B and C Fig. 6 shows the thermal efficiency versus evaorator ressure for working fluids. In first grou the RC318 and in second grou the Proane and in third grou the R113 have more amounts related to the other fluids in the same ressure. For the wet fluids increasing the thermal efficiency the grah behaves aroximately like a arabola but for the dry fluids the sloe for low-ressure condition is shar and then subsides. Fig. 6. System thermal efficiency versus turbine inlet temerature for working fluids in three grous A, B and C at T amb =20 C and T=10 C MASS FLOW RATE Fig. 7 illustrates the effect of the turbine inlet temerature on the mass flow rate of the working fluids. The mass flow rate of the wet fluids is aroximately constant but in a high temerature is increased, so the mass flow rate for RC318 is decreased to its maximum temerature. For the dry fluids, the mass flow rate decreases while turbine inlet temerature increased. Indian J.Sci.Res.1(2) : 74-81,

6 Fig. 7. Mass flow rate versus turbine inlet temerature for working fluids in three grous A, B and C R152a and R12 have a same behavior in thermal efficiency and the second law efficiency and the range of the ressure and the temerature aroximately, but the mass flow rate of R152 is much less than R12 in all temeratures. Fig. 8 shows the mass flow rate versus the thermal efficiency for all working fluids. R125 has a maximum mass flow rate, and the roane has a minimum mass flow rate for all thermal efficiency. Fig. 8. System thermal efficiency versus mass flow rate for working fluids RESULT FOR HYBRID GT/ORC CYCLE This section continues the revious analysis where the interest of combining low temerature bottoming cycles with low exhaust temerature gas turbines has been shown. The arametric otimization of the bottoming cycle deending on the turbine inlet temerature of the bottoming cycle for differences working fluids is now resented. The selection of TOTAL NET WORK In order to show the variety of the total net work due to mass flow rate of any working fluids, Fig. 9 is illustrated. Also, it is aeared that before reaching to the high temerature limitation, in site of decreasing the mass flow rate of dry fluids, it will remain constant for the wet fluids. Furthermore, cycles with dry organic fluids and the constraint of the working fluids close to saturated vaor conditions at turbine inlet have the advantage of allowing for a higher exansion or the use of a recuerator in the toing cycle, as mentioned above. The effectiveness of the HRVG and heat exchangers has been assumed nearly 90%. as deicted in these grahs, Proane and R125 have the lowest and highest mass rate, resectively. RC318 and R143a have a high flow rate versus the Total net Work. Reaching the magnitude of total net work around 5200KW, in site of the low mass rate of R113, the temerature is remained considerably. With analyzing the hybrid GT/ORC, it is Indian J.Sci.Res.1(2) : 74-81,

7 concluded that Proane, R152a and all the other dry fluids regarded in this work are seemed to be more reasonable to use. Fig. 9.System total Net Power versus mass flow rate of ORC for working fluids in three grous A, B and C CONCLUSIONS The erformance of GT/ORC using R152a, R134a, R12, R22, RC318, R143a, R32, R125 and roane and R245fa, R245ca, R236fa, R236ea and R113 as working fluids were analyzed in this study. Afterwards, the comarisons between these results under similar conditions were added. These analyses are erformed based on the first and second laws of thermodynamics. In this regard, the arameters such as thermal efficiency and irreversibility were comared with each other. It was concluded that by utilizing the low-temerature waste heat and alying the roosed working fluids, generating ower could be ossible. Having been examined the obtained results with ones resented in (Tchanche et al., 2009; Kaushik et al., 1994), and (Yamamoto et al., 2001) the high accuracy of this study is roved. The main results of this work are outlined as following: Due to the matter of fact that the cycle thermal efficiency remains aroximately constant, it is not required to suerheat the Organic fluids, when the inlet temerature of the turbine is increased. However, using the second-law analysis, it can be seen that suerheating organic fluids increase the amount of irreversibility. Therefore, to reduce the total irreversibility of the system, the organic fluids must be oerated at the saturated conditions. It is concluded that the dry fluids (R245fa, R245ca, R236fa, R236ea and R113) have a better erformance with resect to the wet fluids. Secially, for R245fa which has the lowest magnitude of the mass flow rate in temerature u than 100 o C, or for the roane and R152 in temerature less than 100 C. In site of the fact that the dry fluids were not condensed after assing the turbine, the wet fluids can be condensed in this osition. For the different conditions investigated in this aer, the best thermal efficiency of the system is determined by emloying GT/ORC uses R113 with a wide temerature range in To imrove the roosed technology in the medium and largescale ower generation, the main challenges are the develoment of the reliable axial vaor turbines, the increment of the HRVG efficient, the big size of the lant, and the amount of mass flow rate. Also, this develoment can be shared with utilizing of the other ower generators, like thermal solar facilities. REFERENCES Quoilin S and Lemort V Technological and Economical Survey of Organic Rankine Cycle Systems. 5 th Euroean Conference Economic and Management of Energy in Industry. Najjar YSH Efficient use of energy by utilizing gas turbine combined systems. Al Therm Eng; 21: Chacartegui R, Sanchez D, Jiménez F, and Sanchez T Analysis of intermediate temerature combined cycles with a carbon dioxide toing cycle. In: Proc. Of ASME Turbo Exo 2008, Berlin, GT Chacartegui R., Sanchez D., Munoz J. M., and Sanchez T Alternative ORC bottoming cycle FOR combined cycle ower lants. Alied Energy, 86(10): Manolakos D., Kosmadakis G., Kyritsis S., and Paadakis G Identification of behaviour and evaluation of erformance of small scale, low-temerature Organic Rankine Cycle system couled with a RO desalination unit. Energy, 34(6): Hung T. C., Shal T. Y., and Wang S. K A review of organic Rankine cycles (ORCs) for the recovery of lowgrade waste heat. Energy, 22(7): Hung T. C waste heat recovery of organic Rankine cycle using dry fluids. Energy Convers. Manage, 42: Dai Y., Wang J. and Gao L Parametric otimization and comarative study of organic Rankine cycle (ORC) for low grade waste heat recovery. Energy Conversion and Management, 50(3): alication, whereas others show the worst. Indian J.Sci.Res.1(2) : 74-81,

8 Gurgency H erformance of ower lants with organic Rankine cycles under art-load and off-design conditions. Solar Energy, 36(1): Lee K. M., Kue S. F., Chien M. L., and Shih Y. S Parameters analysis on organic Rankine cycle energy recovery system. Energy Convers. Manage, 28(2): Wei D, Lu X, Lu Z, Gu J Performance analysis and otimization of Organic Rankine Cycle (ORC) for waste heat recovery. Energy Convers Manage, 48: Maizza V. and Maiza A Working fluids in non-steady flow for waste energy recovery system. Alied Thermal Engineering, 16 (7): Maizza V. and Maiza A Unconventional working fluids in organic Rankine cycles for waste energy recovery system. Alied Thermal Engineering, 21(3): Vijayaraghavan S. and Goswami D. Y Organic working fluids for a combined ower and cooling cycle. ASME j. Energy Resource technology, 127: Mago P. J., Chamra L. M., and Somayaji C Performance analysis of different working fluids for use in organic Rankine cycles. Power and Energy, (221), Tchanche B. F., Paadakis G., Lambrinos G. and Frangoudakis A Fluid selection for a lowtemerature solar organic Rankine cycle. Alied Thermal Engineering, 29(11): Kaushik S.C., Dubey A., Singh, M Steam rankine cycle cooling system: analysis and ossible refinements, Energy Conversion Management 35: Yamamoto T., Furuhata T., Aral N., and Mori K Design and testing of the organic Rankine cycle. Energy, 26(3), Saleh B, Koglbauer G, Wendland M, Fischer J Working fluids for low-temerature organic Rankine cycles. Energy, 32: Invernizzi C, Iora P, and Silva P Bottoming micro- Rankine Cycles for micro-gasturbines. Al Therm Eng, 27: Caresana F, Comodi G, Pelagalli L, and Vagni S Micro combined lant with gas turbine and Organic Cycle. In: Proc. of ASME Turbo Exo, Berlin, GT ; NOMENCLATURE Yari M Thermodynamic analysis of a combined micro turbine with a micro ORC. In: Proc. of ASME Turbo Exo 2008, Berlin, GT ORC h Organic Rankine cycle secific enthaly kj/kg I & irreversibility rate kw M molecular weight kg/mol m& mass flow rate kg/s η efficiency q secific heat kj/kg Q & heat rate kw S entroy kj/k s secific entroy kj/kg K T temerature K W & ower kw T L T H Subscrits c cycle e exit ideal inlet t temerature of the lowtemerature reservoir temerature of the hightemerature reservoir condenser cycle evaorator conditions at the exit isentroic case conditions at the inlet um turbine K K Indian J.Sci.Res.1(2) : 74-81,