MEV Journal of Mechatronics, Electrical Power, and Vehicular Technology 11 (2020) 30-37 Journal of Mechatronics, Electrical Power, and Vehicular Technology e-ISSN: 2088-6985 p-ISSN: 2087-3379 www.mevjournal.com doi: https://dx.doi.org/10.14203/j.mev.2020.v11.30-37 2088-6985 / 2087-3379 ©2020 Research Centre for Electrical Power and Mechatronics - Indonesian Institute of Sciences (RCEPM LIPI). This is an open access article under the CC BY-NC-SA license (https://creativecommons.org/licenses/by-nc-sa/4.0/). Accreditation Number: (RISTEKDIKTI) 1/E/KPT/2015. Open feed organic heater pressure analysis on single-stage regenerative organic Rankine cycle performance Ghalya Pikra a,*, Nur Rohmah b, Rakhmad Indra Pramana a, Andri Joko Purwanto a a Research Centre for Electrical Power and Mechatronics, Indonesian Institute of Sciences Komp LIPI Bandung, Gd 20, Lt 2, Bandung, West Java, 40135 Indonesia b Research Unit for Clean Technology, Indonesian Institute of Sciences Komplek LIPI Bandung, Gedung 50, Bandung, West Java, 40135, Indonesia Received 15 May 2020; accepted 10 June 2020; Published online 30 July 2020 Abstract Single-stage regenerative organic Rankine cycle (SSRORC) is a system that is used for increasing the simple organic Rankine cycle (ORC) performance. Open feed organic heater (OFOH) addition in the ORC system increase power and efficiency of the system. This paper analyzes the SSRORC performance with a variation of P6/P1 ranges from 1.25 to 3.75 with an increment of 0.25, where P6 is the OFOH pressure at the inlet side and P1 is the pressure at the inlet pump 1, respectively. Hot water was used as the heat source with 100 °C and 100 l/min of temperature and volume flow rate as the initial data. R227ea, R245fa, and R141b were chosen as working fluids for performance analysis. The analysis was performed by calculating the heat input, heat loss, pump and turbine power, net power, and thermal efficiency through energy balance. Exergy input, exergy output, and exergy efficiency were analyzed through exergy balance. The results show that P6/P1 = 2 obtains the highest performance than the other pressure ratios for R227ea, while R245fa and R141b obtain the highest performance at P6/P1 = 2.25. R141b has better performance than the other two fluids with 10.97 % and 11.96 % for thermal and exergy efficiency. The results show that the ratio of OFOH pressure at the inlet side to the pressure at inlet pump 1 (P6/P1) in the middle value obtains the best performance. ©2020 Research Centre for Electrical Power and Mechatronics - Indonesian Institute of Sciences. This is an open access article under the CC BY-NC-SA license (https://creativecommons.org/licenses/by-nc-sa/4.0/). Keywords: single-stage regenerative organic Rankine cycle; open feed organic heater; R227ea; R245fa; R141b. I. Introduction Electricity needs are increasing in this globalization era. On the other hand, the availability of fossil fuels is running low, so it is necessary to find other alternative sources before fossil fuels could no longer meet the world's electricity demands. Renewable energy has begun to be developed in various parts of the world. During this time, the Rankine cycle has been known as one of the many power generation systems developed and used to generate electricity. Water is commonly used as a working fluid that can only generate electricity at high operating temperatures, whereas existing renewable energy such as geothermal, solar, and waste heat allows it to be used as a heat source to generate electricity at low and medium operating temperatures so that the use of water must be replaced for the renewable energy utilization. Therefore, organic fluids which have lower boiling temperatures than water can be used in the system to produce electricity at low and medium operating temperatures. This system is known as the organic Rankine cycle (ORC) which has the same components as the Rankine cycle but can produce electricity at low and moderate operating temperatures by using organic fluid as a working fluid. Organic Rankine cycle (ORC) has been utilized in many heat sources, such as biomass [1], geothermal [2][3][4], solar [5], ocean thermal [6], and waste heat [7][8][9]. This system can also be combined with other cycles so that the use of heat sources can be maximized and the heat loss in the system can be reduced. However, because of the low operating temperature, the ORC system has a low performance. Modification of the ORC configuration is one of many ways that can be used to increase the ORC * Corresponding Author. Phone: +6222-2503055 E-mail address: ghalya30@gmail.com; ghal001@lipi.go.id https://dx.doi.org/10.14203/j.mev.2020.v11.30-37 http://u.lipi.go.id/1436264155 http://u.lipi.go.id/1434164106 http://mevjournal.com/index.php/mev/index https://dx.doi.org/10.14203/j.mev.2020.v11.30-37 https://creativecommons.org/licenses/by-nc-sa/4.0/ https://crossmark.crossref.org/dialog/?doi=10.14203/j.mev.2020.v11.30-37&domain=pdf https://crossmark.crossref.org/dialog/?doi=10.14203/j.mev.2020.v11.30-37&domain=pdf https://crossmark.crossref.org/dialog/?doi=10.14203/j.mev.2020.v11.30-37&domain=pdf https://creativecommons.org/licenses/by-nc-sa/4.0/ https://crossmark.crossref.org/dialog/?doi=10.14203/j.mev.2020.v11.30-37&domain=pdf mailto:ghalya30@gmail.com https://crossmark.crossref.org/dialog/?doi=10.14203/j.mev.2020.v11.30-37&domain=pdf G. Pikra et al. / Journal of Mechatronics, Electrical Power, and Vehicular Technology 11 (2020) 30-37 31 system performance. Many ORC configurations have been studied and experimented by many researchers in order to enhance the system performance. Li et al. compared parallel and series of two-stage organic Rankine cycle and as a result, the series configuration has a better performance than the parallel [10]. K. Braimakis and S. Karellas investigated an open and closed preheater that resulting in better performance by using a closed preheater [11]. Li et al. optimized the ORC using dual-pressure evaporation and analyze nine different working fluids with 100-200 °C of heat source temperature. The optimization showed an increase in net power output between 21.4 – 26.7 % [12]. Sciubba et al. compared double stage ORCs and a recuperator addition that resulting in an electricity generation increment up to 8.11 % and 2.67 %, respectively [8]. Mosaffa et al. studied regenerative and recuperative ORCs for geothermal energy that obtain high efficiency [4]. Xi et al. optimized the ORC using single and double stage regenerative ORCs and shows that the double stage has the highest energy and exergy efficiency [13]. Zare compared three configurations such as a simple ORC, a recuperative ORC, and an open-type regenerative preheater ORC for binary geothermal power plants. The result shows that simple ORC obtains the highest power output and the lowest economic cost, and recuperative ORC observed the best energy and exergy efficiency [14]. Safarian and Aramoun evaluated a simple and regenerative-recuperative ORC and examined that the regenerative- recuperative ORC has the best thermal efficiency [15]. Single-stage regenerative organic Rankine cycle (SSRORC) is one of many configurations that can increase the ORC system performance. Inspired from our previous research [16] about the performance comparison of single SSRORC and double stage of regenerative organic Rankine cycle (DSRORC), this paper discusses the pressure analysis of an open feed organic heater (OFOH) in a single-stage regenerative organic Rankine cycle (SSRORC), since our previous research assumes that the pressure entering the OFOH is constant. Eleven different pressure values are investigated to determine the best performance. Those pressures were based on the ratio of pressure at inlet pump 1 and the pressure at inlet OFOH, that is, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75. Temperature and volume flow rate of 100 °C and 100 l/min are used as the initial data using water as the heat source. Three working fluids such as R227ea, R245fa, and R141b are compared and analyzed to determine the best performance. Because the pressure at inlet OFOH must be lower than the inlet turbine pressure, then R227ea can only be used until the maximum pressure ratio of 3.25. II. Materials and Methods A simple organic Rankine cycle consists of four main components, such as evaporator, turbine, condenser, and pump. A modification of the ORC system configuration is necessary to increase its performance. Open feed organic heater (OFOH) addition in the ORC system is one of many modifications that can enhance the system performance. The addition of OFOH in the system is commonly called as a single-stage regenerative organic Rankine cycle (SSRORC). Figure 1 shows the scheme of SSRORC. The working principle of SSRORC that is shown in Figure 1 is almost the same with the simple ORC. The simple ORC only uses one pump and do not use an open feed organic heater (OFOH). In the simple ORC, the fluid from the condenser (1) is directly pumped to the evaporator (4) to be vaporized and expanded in the turbine (5). All of the expanded fluids are condensed in the condenser (7) to be pumped back to the evaporator (4). The SSRORC has an OFOH (6) and one additional pump (3) so that some of the expanded fluids from the turbine flow directly to the OFOH (6) while some other fluids are condensed in the condenser (7) prior to being pumped back to OFOH and finally be pumped to the evaporator. This configuration has a possibility to decrease the heat loss in the condenser and subsequently increase the system performance. This paper analyzes the OFOH pressure influence on the performance of the SSRORC system. It analyzes eleven states of OFOH pressure from the ratio of pressure at inlet pump 1 (P1) and the OFOH inlet (P6). The P6/P1 values used in this study are 1.25, Figure 1. Configuration of single-stage regenerative organic Rankine cycle (SSRORC) G. Pikra et al. / Journal of Mechatronics, Electrical Power, and Vehicular Technology 11 (2020) 30-37 32 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, and 3.75. The T-s diagram from Figure 2 shows all states at each component of SSRORC. Figure 2 shows that the pressure at the state 1 (P1) is the same as the pressure at 7 (P7), the pressure at 2 (P2) is the same as the pressure at 3 and 6 (P3 and P6), and the pressure at 4 (P4) is the same as the pressure at 5 (P5). The pressure at 6 as shown in Figure 2 is made varied for the analysis requirement. The performance analysis was carried out using the first and second laws of thermodynamics through energy and exergy balance from Moran et al. [17]. Figure 3 shows the flowchart of the analysis. Figure 3 shows that the initial temperature and volume flow rate of the heat source (water) for all fluids and all states are assumed to be constant at 100 °C and 100 l/min. The inlet temperature of the turbine (T5) is 90 °C which is at saturated vapor state, and the inlet temperature of the pump 1 (T1) is 40 °C which is at saturated liquid state. Both states are assumed constant for various P6. Isentropic efficiency of the pump and the turbine are assumed 0.75 and 0.85, while the potential and kinetic energy are negligible. The analysis started with heat input (𝑄𝑖𝑖) and heat loss (𝑄𝑙𝑙𝑙𝑙) calculation from energy balance at the evaporator and condenser. The calculation was continued with pump power (𝑊𝑝) and turbine power (𝑊𝑡) calculation from energy balance at the pump and the turbine to determine the net power output. The thermal efficiency (𝜂𝑡ℎ) obtained from the ratio of net power output and the heat input. The calculation of 𝑄𝑖𝑖, 𝑄𝑙𝑙𝑙𝑙, 𝑊𝑝, 𝑊𝑡, and 𝜂𝑡ℎ is shown in Equations (1) to (5) 𝑄𝑖𝑖 = �̇�𝑙𝑓(ℎ5 − ℎ4) = �̇�ℎ𝑤𝐶𝑝ℎ𝑤(𝑇9 − 𝑇8) (1) 𝑄𝑙𝑙𝑙𝑙 = �̇�𝑙𝑓(1 − 𝑦)(ℎ7 − ℎ1) (2) 𝑊𝑝 = �̇�𝑙𝑓[(ℎ4 − ℎ3) + (1 − 𝑦)(ℎ2 − ℎ1)] = �̇�𝑙𝑓 𝜂𝑝⁄ [(ℎ4𝑙 − ℎ3) + (1 − 𝑦)(ℎ2𝑙 − ℎ1)] (3) Wt = ṁof[(h5 − h6) + (1 − y)(h6 − h7)] = Figure 2. T-s Diagram of SSRORC Figure 3. Flowchart of SSRORC performance analysis G. Pikra et al. / Journal of Mechatronics, Electrical Power, and Vehicular Technology 11 (2020) 30-37 33 ṁofηt[(h5 − h6s) + (1 − y)(h6 − h7s)] (4) ηth = Wt−Wp Qin = Wnet Qin (5) where 𝑄𝑖𝑖 is heat input (kW); �̇�𝑙𝑓 is the organic fluid mass flow rate (kg/s); �̇�ℎ𝑤 is heat source mass flow rate (kg/s); 𝐶𝑝ℎ𝑤 is heat source heat capacity (kJ/kg K); 𝑇8 is heat source temperature at inlet evaporator (°C); 𝑇9 is heat source temperature at outlet evaporator (°C); 𝑊𝑖𝑛𝑡 is net output (kW); 𝑄𝑙𝑙𝑙𝑙 is heat loss (kW); 𝑊𝑝 is pump power (kW); 𝑊𝑡 is turbine power (kW); ℎ1 is organic fluid enthalpy at inlet pump 1/outlet condenser (kJ/kg); ℎ2 is organic fluid enthalpy at inlet OFOH/outlet pump 1 (kJ/kg); ℎ2𝑙 is isentropic organic fluid enthalpy at inlet OFOH/outlet pump 1 (kJ/kg); ℎ3 is organic fluid enthalpy at outlet OFOH/inlet pump 2 (kJ/kg); ℎ4 is organic fluid enthalpy at outlet pump 2/inlet evaporator (kJ/kg); ℎ4𝑙 is isentropic organic fluid enthalpy at outlet pump 2/inlet evaporator (kJ/kg); ℎ5 is organic fluid enthalpy at outlet evaporator/inlet turbine (kJ/kg); ℎ6 is organic fluid enthalpy at outlet turbine/inlet OFOH (kJ/kg); ℎ6𝑙 is isentropic organic fluid enthalpy at outlet turbine/inlet OFOH (kJ/kg); ℎ7 is organic fluid enthalpy at outlet turbine/inlet condenser (kJ/kg); ℎ7𝑙 is isentropic organic fluid enthalpy at outlet turbine/inlet condenser (kJ/kg); 𝜂𝑝 is isentropic efficiency of the pump; 𝜂𝑡 is isentropic efficiency of the turbine; 𝜂𝑡ℎ is thermal efficiency (%); and 𝑦 is the fraction of steam extracted. Exergy input (𝐸𝐸𝑖𝑖 ), exergy loss (𝐸𝐸𝑙𝑙𝑙𝑙 ), and exergy efficiency (𝜂𝑛𝑒) are the parameter that would be calculated from the exergy side. The calculation of 𝐸𝐸𝑖𝑖, 𝐸𝐸𝑙𝑙𝑙𝑙, and 𝜂𝑛𝑒 are shown in Equations (6) to (8) 𝐸𝐸𝑖𝑖 = �̇�𝑙𝑓[ℎ5 − ℎ4 − 𝑇𝑎𝑚𝑏(𝑠5 − 𝑠4)] (6) 𝐸𝐸𝑙𝑙𝑙𝑙 = �̇�𝑙𝑓(1 − 𝑦)[ℎ7 − ℎ1 − 𝑇𝑎𝑚𝑏(𝑠7 − 𝑠1)] (7) 𝜂𝑛𝑒 = 𝑊𝑡−𝑊𝑝 𝐸𝑒𝑖𝑛 = 𝑊𝑛𝑒𝑡 𝐸𝑒𝑖𝑛 (8) where 𝐸𝐸𝑖𝑖 is exergy input (kW); 𝐸𝐸𝑙𝑙𝑙𝑙 is exergy loss (kW); 𝜂𝑛𝑒 is exergy efficiency (%); 𝑇𝑎𝑚𝑏 is ambient temperature (°C); 𝑠1 is organic fluid entropy at inlet pump 1/outlet condenser (kJ/kg K); 𝑠4 is organic fluid entropy at outlet pump 2/inlet evaporator (kJ/kg K); 𝑠5 is organic fluid entropy at outlet evaporator/inlet turbine (kJ/kgK); and 𝑠7 is organic fluid entropy at outlet turbine/inlet condenser (kJ/kg K). R227ea, R245fa, and R141b are chosen as the working fluid for the analysis. They are chosen because they are suitable to be used at a low to medium heat source temperature [18][19]. The properties of the three fluids are shown in Table 1 [20][21]. Wet fluid type is not used in the analysis because it is more appropriate to be used for high temperature and the superheated condition [22][23]. A dry and isentropic fluid is a fluid type that is suitable to be used for a low and medium grade heat source [21]. III. Results and Discussions The performance analysis is divided into 5 sections, that is heat input and heat loss analysis, pump and turbine power analysis, net power output and thermal efficiency analysis, exergy input and exergy output analysis, and lastly, the exergy efficiency analysis. The five sections are depicted as the step of the energy and exergy analysis to obtain the system performance of SSRORC with various OFOH pressure. A. Heat input and heat loss analysis The results of heat input (𝑄𝑖𝑖 ) and heat loss (𝑄𝑙𝑙𝑙𝑙 ) calculations for three fluids in all eleven pressure values at the OFOH inlet the OFOH are shown in Figure 4. Figure 4 shows the same heat input values for all fluids at different P6/P1 because of the constant initial data for all states and all fluids. Equation (1) shows that 𝑄𝑖𝑖 is influenced by the mass flow rate (�̇�ℎ𝑤 ), heat capacity (𝐶𝑝ℎ𝑤 ), and temperature differences (𝑇9 − 𝑇8) of the heat source. Those three parameters are constant for all fluids and all P6/P1, hence the 𝑄𝑖𝑖becomes constant. Figure 4 shows the heat loss (𝑄𝑙𝑙𝑙𝑙) for R227ea obtains the highest value and R141b obtains the lowest 𝑄𝑙𝑙𝑙𝑙 among the three different fluids. This condition is connected to the properties of each fluid that is shown in Table 1, where R227ea has the lowest critical pressure and R141b has the highest critical pressure. The result determines that R227ea with the lowest critical pressure obtain a lower pressure at the same P6/P1 than the other fluids, thus made R227ea obtains the highest 𝑄𝑙𝑙𝑙𝑙 than others. R227ea obtains the lowest 𝑄𝑙𝑙𝑙𝑙 at P6/P1= 2, and the highest result is obtained from P6/P1 = 3.25. R245fa and R141b obtain their lowest 𝑄𝑙𝑙𝑙𝑙 at P6/P1 = 2.25, and their highest result is obtained from P6/P1= 3.75. Figure 3 shows that the middle value between the ratio of OFOH pressure at the inlet side (P6) and pump 1 (P1) pressure at the inlet side shows the lowest heat loss for all fluids. B. Pump power and turbine power analysis Figure 5 shows the result of pump power and turbine power calculations for three fluids in eleven states of pressure at inlet the OFOH. Figure 5 shows the highest 𝑊𝑝 obtained by R227ea, and the lowest Table 1. Properties of R227ea, R245fa, and R141b [20][21] Properties R227ea R245fa R141b Molecular Weight (g/mol) 170.03 134.05 116.95 Boiling Temperature (°C) -16.19 15.29 32.2 Critical Temperature (°C) 101.9 154.16 204.5 Critical Pressure (bar) 28.7 36.1 42.1 Type Dry Dry/Isentropic Isentropic G. Pikra et al. / Journal of Mechatronics, Electrical Power, and Vehicular Technology 11 (2020) 30-37 34 Figure 4. 𝑄𝑖𝑖 and 𝑄𝑙𝑙𝑙𝑙 for each fluid atdifferent OFOH pressure 𝑊𝑝 obtained by R141b. Moreover, R141b obtains the highest Wt and R227ea obtains the lowest 𝑊𝑡.𝑊𝑝 for R227ea obtains the lowest and the highest result at P6/P1 = 3.25 and P6/P1 = 2.25, while 𝑊𝑡 obtains its lowest and highest result at P6/P1 = 3.25 and P6/P1 = 2. R245fa and R141b obtain the highest and the lowest 𝑊𝑝 at P6/P1 = 2.5 and P6/P1 = 3.75. Furthermore, the 𝑊𝑡value for R245fa and R141b obtain at P6/P1 = 2.25 and P6/P1 = 3.75 for the highest and the lowest 𝑊𝑡.𝑊𝑝 value for each state and each fluid are not significantly different, while for 𝑊𝑡, the middle ratio of P6 and P1 obtain the highest value, and the lowest value obtains from the highest P6/P1, which is close to inlet turbine pressure, thus made it gain the lowest 𝑊𝑡 and 𝑊𝑝. The result of 𝑊𝑝 and 𝑊𝑡 are then used to determine the net power output (𝑊𝑖𝑛𝑡) of the system, thus will obtain the energy performance of the system. C. Net power output and thermal efficiency analysis Net power output and thermal efficiency calculation are the final energy analysis. The result is shown in Figure 6. Figure 6 shows that 𝑊𝑖𝑛𝑡 for R227ea obtains the highest result at P6/P1 = 2, R245fa and R141b at P6/P1 = 2.25. On the contrary, R227ea obtains the lowest 𝑊𝑖𝑛𝑡 at P6/P1 = 3.25, and R245fa and R141b at P6/P1 = 3.75 obtain the lowest 𝑊𝑖𝑛𝑡 . 𝑊𝑖𝑛𝑡 value is influenced by the difference between 𝑊𝑝 and 𝑊𝑡, which means that the higher 𝑊𝑡 and the lower 𝑊𝑝 obtain a high 𝑊𝑖𝑛𝑡. Figure 5 shows that 𝑊𝑝 for R227ea obtains the lowest result at P6/P1 = 3.25, while 𝑊𝑡 obtains its highest result at P6/P1 = 2. The result shows that 𝑊𝑖𝑛𝑡 value is more influenced by 𝑊𝑡 than 𝑊𝑝 because 𝑊𝑖𝑛𝑡 value results in the highest value at P6/P1= 2, which is the same as 𝑊𝑡. Figure 5. 𝑊𝑝and 𝑊𝑡 for each fluid at different OFOH pressure G. Pikra et al. / Journal of Mechatronics, Electrical Power, and Vehicular Technology 11 (2020) 30-37 35 Furthermore, 𝑊𝑝 value obtains a very low value compared to 𝑊𝑡 , thus made 𝑊𝑖𝑛𝑡 value more influenced by 𝑊𝑡 than 𝑊𝑝 . R245fa and R141b also obtain the highest 𝑊𝑖𝑛𝑡 at P6/P1 = 2.25 because they obtain the highest 𝑊𝑡 at the same P6/P1. However, R141b obtains the highest 𝑊𝑖𝑛𝑡 value than R227ea and R245fa. The lowest 𝑊𝑝 value obtained by R141b than R227ea and R245fa made R141b obtain the highest 𝑊𝑖𝑛𝑡 since 𝑊𝑡 value for each fluid almost obtain the same result in the same condition. Thermal efficiency (𝜂𝑡ℎ) value depends on heat input (𝑄𝑖𝑖) and 𝑊𝑖𝑛𝑡 value. Since 𝑄𝑖𝑖 is the same for all fluids and all states, then 𝜂𝑡ℎ value depends on 𝑊𝑖𝑛𝑡. Equation (5) shows that the higher the 𝑊𝑖𝑛𝑡 obtain a higher 𝜂𝑡ℎ. It is clear that Figure 6 shows the highest 𝜂𝑡ℎ value for R227ea obtained from P6/P1 = 2, the lowest 𝜂𝑡ℎ obtained from P6/P1 = 3.25, which is the same states with 𝑊𝑖𝑛𝑡. The result also the same with R245fa and R141b, where 𝜂𝑡ℎ value obtains its highest value at P6/P1= 2.25, and they obtain the lowest 𝜂𝑡ℎ at P6/P1 = 3.75, the same with 𝑊𝑖𝑛𝑡 value. Furthermore, R141b obtain the highest 𝜂𝑡ℎ than R245fa and R227ea because R141b gain the highest 𝑊𝑖𝑛𝑡 than other fluids. This result shows that R141b obtains the best energy performance than R227ea and R245fa. D. Exergy input and exergy loss analysis Exergy input and exergy loss are two main parameters for exergy analysis. The result of both parameters for three fluids in eleven states is shown in Figure 7. Figure 7 shows that all fluids obtain the highest 𝐸𝐸𝑖𝑖 at the highest P6/P1, which is 3.25 for R227ea, and 3.75 for R245fa and R141b. In addition, the lowest 𝐸𝐸𝑖𝑖 obtained from the lowest P6/P1, Figure 6. 𝑊𝑖𝑛𝑡 and 𝜂𝑡ℎ for each fluid at different OFOH pressure Figure 7. 𝐸𝐸𝑖𝑖 and 𝐸𝐸𝑙𝑙𝑙𝑙 for each fluid at different OFOH pressure G. Pikra et al. / Journal of Mechatronics, Electrical Power, and Vehicular Technology 11 (2020) 30-37 36 which is 1.25. It can be analyzed that the highest pressure difference from P1 and P6 obtain the highest 𝐸𝐸𝑖𝑖. However, 𝐸𝐸𝑖𝑖 value for all fluids at the same states obtain almost the same because of the same 𝑄𝑖𝑖 value for all fluids for all states. Figure 7 shows that R227ea obtains its highest and its lowest 𝐸𝐸𝑙𝑙𝑙𝑙 at P6/P1 = 3.25 and at P6/P1= 1.75. Similarly, R245fa and R141b obtain their highest and lowest 𝐸𝐸𝑙𝑙𝑙𝑙 at P6/P1 = 3.75 and at P6/P1 = 2.25. 𝐸𝐸𝑙𝑙𝑙𝑙 has a similar curve with the 𝑄𝑙𝑙𝑙𝑙, where it reaches the lowest P6/P1 in the middle and the highest P6/P1 at the highest value. The exergy input is then used to determine the exergy efficiency of the system. E. Exergy efficiency analysis Exergy efficiency is determined to perform the exergy performance of the system. Figure 8 shows the results for the three fluids in eleven states of OFOH in the SSRORC system. Figure 8 shows that 𝜂𝑛𝑒 obtains the highest value at P6/P1 = 1.75 for R227ea, nearly the same as at P6/P1 = 2, and at P6/P1 = 2.25 for R245fa and R141b. On the contrary, 𝜂𝑛𝑒 has the lowest value for R227ea at P6/P1 = 3.25, and for R245fa and R141b at P6/P1 = 3.75. The result is the same as 𝜂𝑡ℎ, where they obtain the highest value at the middle P6/P1 and the lowest value at the highest P6/P1. Although 𝜂𝑛𝑒 depends on 𝑊𝑖𝑛𝑡 and 𝐸𝐸𝑖𝑖 value, in this analysis the 𝑊𝑖𝑛𝑡 result is more dominant than 𝐸𝐸𝑖𝑖 for 𝜂𝑛𝑒. Since 𝐸𝐸𝑖𝑖 value is almost the same for all fluids and all states, the 𝜂𝑛𝑒 value has the same maximum and minimum value as 𝑊𝑖𝑛𝑡 and 𝜂𝑛𝑒. IV. Conclusion Open feed organic heater (OFOH) pressure analysis using eleven states obtain the best performance for R227ea at P6/P1 = 2 for energy analysis and at P6/P1 = 1.75 for exergy analysis, and at P6/P1 = 2.25 for R245fa and R141b. The lowest performance for R227ea was at P6/P1= 3.25, and at P6/P1 = 3.75 for R245fa and R141b. The analysis concluded that the P6/P1 in the middle value obtain the best performance, and the highest pressure difference from state 1 and state 6 obtain the lowest performance. R141b with the highest critical pressure than R227ea and R141b obtain the highest performance with thermal and exergy efficiency of 10.97 % and 11.96 %, thus made R141b is the most recommended fluid to be used for 100 °C of heat source temperature rather than R227ea and R245fa. Since in this paper it is assumed that a constant heat source temperature is used in analyzing the OFOH pressure influence to the SSRORC performance, the variation of the heat source temperature will be done in the future to complete the analysis of OFOH pressure to the performance of SSRORC. Acknowledgement The authors would like to thank the Research Centre for Electrical Power and Mechatronics for supporting the organic Rankine cycle research. We also would like to thank our research team in the conversion and conservation energy for helping the research. We also express our high gratitude to the reviewers who have provided input and suggestions so that this paper is qualified for publication. Declarations Author contribution G. Pikra is the main contributor of this paper. All authors read and approved the final paper. Funding statement This research did not receive any specific grant from funding agencies in the public, commercial, or non-profit sectors. 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Introduction II. Materials and Methods III. Results and Discussions A. Heat input and heat loss analysis B. Pump power and turbine power analysis C. Net power output and thermal efficiency analysis D. Exergy input and exergy loss analysis E. Exergy efficiency analysis IV. Conclusion Acknowledgement Declarations Author contribution Funding statement Conflict of interest Additional information References