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How to give a full play to the advantages of zeotropic working fluids in organic Rankine cycle (ORC)
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Energy Procedia 158 Energy Procedia 00(2019) (2017)1591–1597 000–000 www.elsevier.com/locate/procedia
10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10th International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
How to give a full play to the advantages of zeotropic working The 15th International on District Heating and Cooling How to give a full play toSymposium the advantages of zeotropic working fluids in organic Rankine cycle (ORC) fluids in organic Rankine cycle (ORC) Assessing the feasibility of using the heat demand-outdoor Weicong Xu, Shuai Deng, Yue Zhang, Dongpeng Zhao, Li Zhao* Weicong Xu, Shuaifor Deng, Yue Zhang, Dongpeng Zhao,demand Li Zhao* forecast temperature function a long-term district heat Key laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education of China, Tianjin 300072, China(Tianjin University), Ministry of Education of China, Tianjin 300072, Key laboratory of Efficient Utilization of Low and Medium Grade Energy a,b,c a a b c c China
I. Andrić
a
*, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Corre
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France Abstract Improving the efficiency of organic Rankine cycle (ORC) is the ultimate goal of the researchers with thermodynamic background. Improving the efficiency organic Rankine the ultimate goal of the researchers with thermodynamic background. As the “blood” of ORC,ofthe working fluid cycle plays(ORC) a vitalisrole to the improvement of the performance. The thermos-physical As the “blood” of ORC, the working fluidand plays a vital role to of theworking improvement the directly performance. thermos-physical properties parameters, transport parameters other parameters fluids of could affect The the efficiency, safety, Abstract parameters, transport parameters and other parameters of working fluids could directly affect the efficiency, safety, properties stability and economy of ORC. With the increasing requirements on working fluids, it is difficult to find a pure working fluid not stability economy of ORC. Withperformance the increasing on working fluids, itprotection is difficultand to safety. find a pure workingzeotropic fluid not only withand satisfied thermodynamic butrequirements also permissible enverimental In contrast, District heating networks are commonly in working the literature asisone of the mostthe effective solutions for decreasing the only withfluid, satisfied thermodynamic also permissible and safety. Inofcontrast, zeotropic working which is mixed withperformance two oraddressed morebut pure fluids,enverimental easier to protection meet requirements thermos-physical greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat working fluid, which is mixed with two or the more pure stage, working is easier to meet working the requirements of thermos-physical properties, environmental and safety. But at present the fluids, application of zeotropic fluids in ORC still adapted or sales. Dueenvironmental to the changed climate conditions and building policies, heat working demand fluids in theinfuture could decrease, properties, safety. But at what the present stage, therenovation application zeotropic ORCthe still adapted or employed the methodologyand originated from we learn from pure workingoffluids. Under such circumstances, temperature prolonging the investment return period. employed the methodology originated fromsystem what we learn from pure fluids.shift Under suchincircumstances, the temperature glide of zeotropic working fluids improves efficiency while theworking composition would turn reduce system efficiency. The of main scope of this paper is to assess the feasibility of using thethe heat demand – outdoor temperature function for heat demand glide zeotropic shift on would in turn reduce system efficiency. Thus, 3D-ORC is working proposedfluids in thisimproves paper tosystem provideefficiency zeotropicwhile working composition fluids a full play performance improvement of energy forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 Thus, 3D-ORC proposed in this paper to provide zeotropic fluidsofa full play on of performance improvement of energy conversion. Theisperformance of 3D-ORC is calculated for working the recovery waste heat internal combustion engines and buildingswith that vary in both construction and typology. weather scenarios (low, medium, high) and three district conversion. Thethe performance ofusing 3D-ORC is calculated for theThree recovery of results waste heat ofthat internal combustion and compared simple ORC pureperiod and zeotropic working fluids. The show the performance ofengines 3D-ORC is renovation scenarios wereORC developed pure (shallow, intermediate, deep). To estimate theshow error,that obtained heat demand values were compared theORC simple and zeotropic working fluids. The results the performance of 3D-ORC is better thanwith simple under theusing same conditions. compared with results dynamic heat demand model, previously developed and validated by the authors. better than simple ORC from underathe same conditions. The results that when weather change is considered, the margin of error could be acceptable for some applications Copyright © showed 2018 Elsevier Ltd. only All rights reserved. ©(the 2019 The Published by Elsevier Ltd.20% for all weather scenarios considered). error annual demand was lower However, after introducing renovation Copyright ©inAuthors. 2018 Elsevier Ltd. Allresponsibility rights than reserved. Selection and peer-review under of the scientific committee of the 10th International Conference on Applied This is an open accessvalue article under theupCC BY-NC-ND license on (http://creativecommons.org/licenses/by-nc-nd/4.0/) scenarios, the error increased to 59.5% (depending the weather and renovation scenarios Conference combination on considered). th Selection and peer-review under responsibility of the scientific committee of the 10 International Applied Energy (ICAE2018). Peer-review under responsibility of the scientific committee of ICAE2018 –ofThe 10thupInternational Conference oncorresponds Applied Energy. The value of slope coefficient increased on average within the range 3.8% to 8% per decade, that to the Energy (ICAE2018). decrease organic in the Rankine number cycle; of heating hours of 3D 22-139h during3D-ORC the heating season (depending on the combination of weather and Keywords: ORC; zeotropic; construction; renovation scenarios considered). the other hand, function intercept increased for 7.8-12.7% per decade (depending on the Keywords: organic Rankine cycle; ORC;On zeotropic; 3D construction; 3D-ORC coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
© 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +86-022-27890051; fax: +86-022-27404188.
address:author. [email protected] * E-mail Corresponding Tel.: +86-022-27890051; fax: +86-022-27404188. Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility the scientific 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.374
Weicong Xu et al. / Energy Procedia 158 (2019) 1591–1597 Weicong Xu et al./ Energy Procedia 00 (2018) 000–000
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1. Introduction As an efficient way to convert medium- and low-temperature heat into power, subcritical organic Rankine cycle (ORC) has received much attention from many scholars. The thermos-physical properties parameters, transport parameters and other parameters of working fluid, which is the “blood” of ORC, could directly affect the efficiency, safety, stability and economy of ORC [1]. However, the working fluid also causes many irreversible losses in cycle. Therefore, in order to improve the efficiency of ORC, the bottleneck problem of working fluid has to be solved firstly. At present, pure working fluids are used in most of the subcritical ORC. In addition to considering the thermosphysical properties of working fluid, the safety and environmental protection factors are becoming more and more important during working fluid selection. Considering the above factors comprehensively, the pure working fluids which could be applied in ORC perfectly has been very few. Furthermore, there is no suitable pure working fluid under majority conditions. However, there are bottlenecks in the design and development of novel pure working fluid, such as low accuracy of computational model [2] and poor economic of commercial production [3]. In contrast, zeotropic working fluids, which are produced by a simple mixing of two or more pure working fluids, are easier to meet the requirements of thermos-physical properties, environmental and safety. Therefore, zeotropic working fluids will be the main carrier of the ORC in the future. Zeotropic working fluids are mixtures consisting of two or more pure working fluids with different boiling temperature. At the gas-liquid equilibrium state, the gas and liquid phases of the zeotropic working fluids have different components. Therefore, temperature glide and composition shift are typical characteristics of zeotropic working fluids. The reason of temperature glide and composition shift is the composition variation of gas and liquid phase during phase transformation. By using temperature glide, the cycle performance could be improved by reducing the irreversible loss in heat transfer process. But the composition shift would reduce the performance of ORC. Therefore, there are contradictions in the study of the ORC using zeotropic working fluids, which limits the extensive application of zeotropic working fluids in practical engineering. In this paper, the existing researches on ORC using zeotropic working fluids were summarized to find out the reasons resulting in this contradiction firstly. Then, a 3D thermodynamic cycle construction method was applied to give full play to the advantages of zeotropic working fluids. Lastly, a specific case was comparatively analyzed. 2. State of the art 2.1. Temperature glide The irreversible loss in the heat transfer process of ORC could be reduced by matching the temperature changes of heat transfer fluid and the zeotropic working fluid. Table 1 summarizes the researches of ORC using zeotropic working fluids, which provided relatively detailed data. The contents listed in the table include research time, author, working fluid, heat source, heat sink, research method and research results. The research results show that the relative change values of the performance of zeotropic working fluids compared with pure working fluids from the aspects of net output (Wnet), thermal efficiency (ηⅠ) and the efficiency of the second law of thermodynamics (ηⅡ). In general, the performance of ORC using zeotropic working fluids is better than that of ORC with pure working fluids. However, it is worth noting that under some conditions, the using of zeotropic working fluid could also reduce the thermal efficiency and the efficiency of the second law of thermodynamics of ORC. Table 1. Summary of researches on ORC using zeotropic working fluids. Time
Author
Working fluid
Heat source
Research method
Research results
ΔWnet
ΔηⅠ
ΔηⅡ
(%)
(%)
(%)
2009
Wang et. al [4]
R245fa/R152a (0.45/0.55)
Hot water (85℃)
theoretical analysis
+2.18
-12.26
-12.26
2011
Heberle et. al [5]
R600a/R601a (0.9/0.1)
Hot water (120℃)
theoretical analysis
+11.90
-
+8.20
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2012
Chys et. al [6]
R601a/hexane (0.43/0.57)
Hot water (150℃)
theoretical analysis
+12.30
+15.70
-
2013
Liu et. al [7]
R600a/R601 (0.94/0.06)
Hot water (140℃)
theoretical analysis
+8.10
-
-
2014
Lecompte et. al [8]
R600a/R601a (0.81/0.19)
Hot water (150℃)
theoretical analysis
+27.20
-4.30
+6.10
2014
Dong et. al [9]
MM/MDM (0.4/0.6)
Hot oil (280℃)
theoretical analysis
-
+5.96
+4.45%
2015
Song et. al [10]
Cyclohexane/R141b (0.5/0.5)
Exhaust gas (300℃)
theoretical analysis
+13.30
-
-
2016
Lu et. al [11]
R245fa/R600a (0.65/0.35)
Hot water (140℃)
theoretical analysis
+9.58
+3.22
-
2016
Wang et. al [12]
R601a/R600a (0.6/0.4)
Hot oil (115℃)
experimental study
+25.00
-
-
2017
Pang et. al [13]
R245fa/R123 (0.66/0.34)
Hot oil (120℃)
experimental study
+6.4
+12.80
-
2.2. Composition shift The composition variation during phase transformation also brings about another phenomenon, that is, composition shift. The difference between the charge composition and circulating composition of zeotropic working fluid is composition shift. The main reasons leading to the composition shift of zeotropic working fluid could be attributed to: (a) the velocity difference between gas and liquid phase; (b) solubility difference of different components in lubricating oil; (c) the volume difference of the system and the leakage. A summary of researches on composition shift of zeotropic working fluid with detailed data is listed in Table 2. The value of composition shift is equal to the maximum difference between charge composition and circulating composition. ΔηⅠ is equal to the relative change values of system thermal efficiency using circulating composition compared with using charge composition. The results show that the values of composition shift are between 0.68% and 6.40%. And the composition shift causes the reduction of the system performance. Table 2. Summary of researches on composition shift of zeotropic working fluid. Author
Working fluid
Research method
Composition shift (%)
ΔηⅠ (%)
2004
Chen et. al [14]
R32/Rl34a
theoretical analysis
3.39
-
2005
Youbi-Idrissi et. al [15]
R407C
theoretical analysis
3.00
-
2006
Chen et. al [16]
R23/R134a
experimental study
0.68
-
2011
Bao et. al [17]
R407C
theoretical analysis
5.80
-
Time
2011
Chen et. al [18]
R23/R152
experimental study
6.40
-
2012
Fukuda et. al [19]
R1234ze(E)/R32
experimental study
5.00
-1.79
2012
Xu et. al [20]
R290/R600a
experimental study
4.10
-
2014
Zhao et. al [21]
R600a/R601
theoretical analysis
3.74
-6.79
2016
Bao et. al [22]
R600a/R601
experimental study
1.15
-
2017
Zhou et. al [23]
R227ea/R245fa
theoretical analysis
3.74
-0.34
In summary, the application of zeotropic working fluid could improve the performance of ORC under most of the conditions. But the application of zeotropic working fluids in ORC commonly employ the traditional methodology originate from knowledge gained from pure working fluids, which would lead to the adverse effects of the composition shift of zeotropic working fluid. This means that under existing methods, the advantages of zeotropic working fluids have not been fully realized. 3. 3D thermodynamic cycle 3.1. Methodology In previous studies, we proposed the 3D thermodynamic cycle construction method in [24]. The core of this method is to construct an efficient thermodynamic cycle by using different working fluids to meet different requirements of the thermos-physical properties of working fluids in different thermodynamic processes. At the
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aspect of thermodynamic analysis method, the dimension of working fluid is added to the traditional T-S diagram to clearly indicate the change of working fluids in circulation, as shown in Fig. 1.
Fig. 1. The principle diagram of the 3D construction method[24]
According to this method, the actual cycle process is A1→B1→B2→C2→C1→D1→D2→A2→A1, as follows. A1→B1：The working fluid used in this process is X, which could meet the temperature matching requirements of the heat source in the evaporation process; B1→B2：The working fluid is switched from X to Y; B2→C2：The working fluid used in this process is Y, which could meet the requirements of the expansion process on the thermos-physical properties of working fluids. C2→C1：The working fluid is switched from Y to X; C1→D1：The working fluid used in this process is X, which could meet the temperature matching requirements of the heat sink in the condensation process; D1→D2：The working fluid is switched from X to Y; D2→A2：The working fluid used in this process is Y, which could meet the requirements of the compression process on the thermos-physical properties of working fluids. A2→A1：The working fluid is switched from Y to X; The ultimate goal of this thermodynamic cycle is to approach the Carnot cycle by means of various working fluids in different thermodynamic processes. By combining this method with zeotropic working fluids, the switching of working fluids in different processes could be achieved by using the composition variation of gas and liquid phase during phase transformation. This method could not only make reasonable use of temperature glide of zeotropic working fluids, but also solve the problems caused by composition shift. The feasibility and superiority of this method are verified by a case studied in the section 3.2. 3.2. Case study The recovery of waste heat is an effective way to improve the thermal efficiency of internal combustion engines. The waste heat of internal combustion engine usually comes from exhaust gas and jacket water, whose temperature is 500℃-900℃ and 90℃-100℃, respectively [25]. A large number of thermodynamic cycles have been carried out by scholars for the recovery and utilization of internal combustion engine waste heat. But there is no consistent conclusion for the optimal cycle. From the perspective of working fluids, each working fluid should have the best operating conditions. In order to adapt to the characteristics of large temperature difference of internal combustion engine waste heat, this paper compares the Benzene, which has higher critical temperature, and R245fa, which has lower critical temperature. During comparison, the high temperature in cycle is set from 300K to critical temperature with the interval of 2K. The temperature difference of the cycle is set to 20K. The thermal efficiency and thermodynamic perfection of a
Weicong Xu et al. / Energy Procedia 158 (2019) 1591–1597 Author name / Energy Procedia 00 (2018) 000–000
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7 6
(a)
352K
5 4 3
Benzene R245fa
2 1
320
360
400
440
480
520
Thermodynamic perfection (%)
Thermal efficiency (%)
simple ORC using Benzene and R245fa are calculated in this temperature range. The results are shown in Fig 2. When the high temperature is less than 352K, the thermal efficiency and thermodynamic perfection of ORC using R245fa are higher than that of ORC using Benzene. While the high temperature is greater than 352K, ORC using Benzene shows better performance. Therefore, the waste heat in different temperature ranges should be recovered by using different working fluids. As a result, 3D-ORC for internal combustion engine waste heat recovery is proposed by using the 3D construction method. The system schematic diagram and the 3D thermodynamic cycle diagram are shown in fig. 3(a) and fig. 3(b) respectively. 100
(b)
352K
90 80
Benzene R245fa
70 60
320
High temperature (K)
360
400
440
480
520
High temperature (K)
Fig. 2. Comparison results of R245fa and Benzene: (a) thermal efficiency; (b) thermodynamic perfection 4 3
T P
separator sight glass P T
expanderⅠ 5
6
evaporatorⅠ
7 P T
pumpⅡ
2
T/K
P T
evaporatorⅡ
3 2 1
4
P T
pumpⅠ
8
P T
expanderⅡ
T P
10
9
mixer 9
R245fa/Benzene (0.11/0.89)
8
1
T P
T P
10
7
6 5
P T
s/kJ·kg-1·K-1
R245fa/Benzene (0.3/0.7)
θ/% R245fa/Benzene (0.49/0.51)
(a) (b) Fig. 3. 3D-ORC: (a) system schematic diagram; (b) 3D thermodynamic cycle diagram
The zeotropic working fluid R245fa/Benzene is applied in 3D-ORC. The adjustment of the composition of working fluid is realized by the separation of gas and liquid phases in separator. In order to research the advantages of 3D-ORC, the performance is compared with the simple ORC using pure and zeotropic working fluid. A detailed mathematical model of 3D-ORC is established to calculate the whole system performance, as shown in Table 3. The 3D-ORC is better than the simple using pure or zeotropic working fluids in terms of net output, thermal efficiency and thermodynamic perfection. Table 3. Mathematical model of 3D-ORC. Component/Efficiency Pump Ⅰ Evaporator Ⅰ Separator Pump Ⅱ Evaporator Ⅱ
Equation = WpumpΙ mwf_Ι (h2 − h1 ) pumpΙ = Qeva Ι m= C p_hseΙ mhseΙ (ThseΙ_in − ThseΙ_out ) wf_Ι (h3 - h2 ) mwf_П= (1 − x)mwf_Ι ; mwf_Ш = xmwf_Ι ; m = mwf_Π h5 + mwf_Ш h4 wf_Ι h3 = WpumpΠ mwf_Π (h6 − h5 ) pumpΠ
= Qeva П m= C p_hseП mhseП (ThseП_in − ThseП_out ) wf_П (h7 - h6 )
Expander Ⅰ
= WexpΙ mwf_Ш (h4 − h9 )expΙ
ExpanderⅡ
= WexpП mwf_П (h6 − h7 )expП
Mixer
m= mwf_Π h8 + mwf_Ш h9 ; m = mwf_Π + mwf_Ш wf_Ι h10 wf_Ι
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= Qcon m= Cp_hsk mhsk (Thsk_out − Thsk_in ) wf_І (h10 - h1 )
Condenser Net power
Wnet =WexpІ +WexpП − WpumpІ − WpumpП
Thermal efficiency
thermal = Wnet (QevaΙ +QevaП )
Thermodynamic perfection
therm_perf = thermal Carnot
Table 4. Comparison results between 3D-ORC and simple ORC. Parameters
Simple ORC [26]
3D-ORC
Temperature of exhaust gas (K)
771.15
771.15
771.15
-1
Mass flow of exhaust gas (kg·s )
0.2586
0.2586
0.2586
Temperature of jacket water (K)
365.25
365.25
365.25
Mass flow of jacket water (kg·s )
2.1
2.1
2.1
Inlet temperature of cooling water (K)
288.15
288.15
288.15
Working fluid
R245fa
R245fa/Benzene (0.3/0.7)
R245fa/Benzene (0.3/0.7)
-1
Net output (kW)
13.7
15.6
39.84
Thermal efficiency (%)
9.4
11.4
15.42
Thermodynamic perfection (%)
27.17
30.94
40.92
4. Conclusions In order to solve the problems existing in the application of zeotropic working fluids, this paper presents a method to give full play to the advantages of zeotropic working fluids. The existing literatures on the ORC using zeotropic working fluids are summarized briefly. Most of the studies show that ORC using zeotropic working fluids has better performance than that of pure working fluids. But the efficiency of ORC would be reduced due to the composition shift of zeotropic working fluid. Based on the 3D construction method of thermodynamic cycle, 3DORC is proposed, which could not only make reasonable use of temperature glide of zeotropic working fluids, but also solve the problems caused by composition shift. According to theoretical analysis, the performance of 3D-ORC is better than that of simple ORC using pure or zeotropic working fluids. Acknowledgements This work is supported by the National Nature Science Foundation of China under Grant No.51776138, Innovation Development and Demonstration Project of Ocean Economy under Grant No. BHSF2017-19 and Tianjin Talent Development Special Support Program for High-Level Innovation and Entrepreneurship Team. References [1]. [2]. [3]. [4]. [5]. [6]. [7].
Bao J, Zhao L. A review of working fluid and expander selections for organic Rankine cycle. Renewable & Sustainable Energy Reviews, 2013, 24(10):325-342. Lampe M, Stavrou M, Bücker H M, et al. Simultaneous Optimization of Working Fluid and Process for Organic Rankine Cycles Using PC-SAFT. Industrial & Engineering Chemistry Research, 2014, 53(21):8821–8830. Linke P, Papadopoulos A I, Seferlis P. Systematic Methods for Working Fluid Selection and the Design, Integration and Control of Organic Rankine Cycles—A Review. Energies, 2015, 8(6):4755-4801. Wang X D, Zhao L. Analysis of zeotropic mixtures used in low-temperature solar Rankine cycles for power generation. Solar Energy, 2009, 83(5):605-613. Heberle F, Preißinger M, Brüggemann D. Zeotropic mixtures as working fluids in Organic Rankine Cycles for low-enthalpy geothermal resources. Renewable Energy, 2012, 37(1):364-370. Chys M, Broek M V D, Vanslambrouck B, et al. Potential of zeotropic mixtures as working fluids in organic Rankine cycles. Energy, 2012, 44(1):623-632. Liu Q, Duan Y, Yang Z. Effect of condensation temperature glide on the performance of organic Rankine cycles with zeotropic mixture
[8]. [9]. [10]. [11]. [12]. [13]. [14]. [15]. [16]. [17]. [18]. [19]. [20]. [21]. [22]. [23]. [24]. [25]. [26].
Weicong Xu et al. / Energy Procedia 158 (2019) 1591–1597 Author name / Energy Procedia 00 (2018) 000–000
1597 7
working fluids. Applied Energy, 2014, 115(4):394-404. Lecompte S, Ameel B, Ziviani D, et al. Exergy analysis of zeotropic mixtures as working fluids in Organic Rankine Cycles. Energy Conversion & Management, 2014, 85(9):727-739. Dong B, Xu G, Cai Y, et al. Analysis of zeotropic mixtures used in high-temperature Organic Rankine cycle. Energy Conversion & Management, 2014, 84:253-260. Song J, Gu C W. Analysis of ORC (Organic Rankine Cycle) systems with pure hydrocarbons and mixtures of hydrocarbon and retardant for engine waste heat recovery. Applied Thermal Engineering, 2015, 89:693-702. Lu J, Zhang J, Chen S, et al. Analysis of organic Rankine cycles using zeotropic mixtures as working fluids under different restrictive conditions. Energy Conversion & Management, 2016, 126:704-716. Wang Y, Liu X, Ding X, et al. Experimental investigation on the performance of ORC power system using zeotropic mixture R601a/R600a. International Journal of Energy Research, 2017, 41(5). Pang K C, Chen S C, Hung T C, et al. Experimental study on organic Rankine cycle utilizing R245fa, R123 and their mixtures to investigate the maximum power generation from low-grade heat. Energy, 2017, 133. Chen J. Comprehensive approach to predicting the circulation composition of zeotropic refrigerants. Journal of Southeast University (English Edition), 2004, 20(3):315-318. Youbi-Idrissi M, Bonjour J, Meunier F. Local shifts of the fluid composition in a simulated heat pump using R-407C. Applied Thermal Engineering, 2005, 25(17):2827-2841. Chen J, K.Beermann. New problems in the composition shift of zeotropic working fluids (In Chinese). National Symposium on New technology of refrigeration and air conditioning. 2006. Bao J, Zhao L, Song W. Theoretical Investigation on the Influence of Composition Shift on the Heat Exchange during the Phase Change Using R407C (In Chinese). Journal of Mechanical Engineering, 2011, 47(16):127-132. Chen J, Kruse H. Calculating Circulation Concentration of Zeotropic Refrigerant Mixtures. Hvac & R Research, 2011, 1(3):219-231. Fukuda S, Takata N, Koyama S. The Circulation Composition Characteristic of the Zeotropic Mixture R1234ze(E)/R32 in a Heat Pump Cycle. Faseb Journal, 2012, 24. Xu X, Liu J, Cao L, et al. Local composition shift of mixed working fluid in gas–liquid flow with phase transition. Applied Thermal Engineering, 2012, 39(4):179-187. Zhao L, Bao J. The influence of composition shift on organic Rankine cycle (ORC) with zeotropic mixtures. Energy Conversion & Management, 2014, 83(4):203-211. Bao J, Zhao L. Experimental research on the influence of system parameters on the composition shift for zeotropic mixture (isobutane/pentane) in a system occurring phase change. Energy Conversion & Management, 2016, 113:1-15. Zhou Y, Zhang F, Yu L. The discussion of composition shift in organic Rankine cycle using zeotropic mixtures. Energy Conversion & Management, 2017, 140:324-333. Xu W, Deng S, Su W, et al. How to approach Carnot cycle via zeotropic working fluid: Research methodology and case study. Energy, 2018, 144:576-586. Wang T, Zhang Y, Peng Z, et al. A review of researches on thermal exhaust heat recovery with Rankine cycle. Renewable & Sustainable Energy Reviews, 2011, 15(6):2862-2871. Yu G, Shu G, Tian H, et al. Simulation and thermodynamic analysis of a bottoming Organic Rankine Cycle (ORC) of diesel engine (DE). Energy, 2013, 51(9):281-290.
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Energy Procedia 158 Energy Procedia 00(2019) (2017)1591–1597 000–000 www.elsevier.com/locate/procedia
10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10th International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
How to give a full play to the advantages of zeotropic working The 15th International on District Heating and Cooling How to give a full play toSymposium the advantages of zeotropic working fluids in organic Rankine cycle (ORC) fluids in organic Rankine cycle (ORC) Assessing the feasibility of using the heat demand-outdoor Weicong Xu, Shuai Deng, Yue Zhang, Dongpeng Zhao, Li Zhao* Weicong Xu, Shuaifor Deng, Yue Zhang, Dongpeng Zhao,demand Li Zhao* forecast temperature function a long-term district heat Key laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education of China, Tianjin 300072, China(Tianjin University), Ministry of Education of China, Tianjin 300072, Key laboratory of Efficient Utilization of Low and Medium Grade Energy a,b,c a a b c c China
I. Andrić
a
*, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Corre
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France Abstract Improving the efficiency of organic Rankine cycle (ORC) is the ultimate goal of the researchers with thermodynamic background. Improving the efficiency organic Rankine the ultimate goal of the researchers with thermodynamic background. As the “blood” of ORC,ofthe working fluid cycle plays(ORC) a vitalisrole to the improvement of the performance. The thermos-physical As the “blood” of ORC, the working fluidand plays a vital role to of theworking improvement the directly performance. thermos-physical properties parameters, transport parameters other parameters fluids of could affect The the efficiency, safety, Abstract parameters, transport parameters and other parameters of working fluids could directly affect the efficiency, safety, properties stability and economy of ORC. With the increasing requirements on working fluids, it is difficult to find a pure working fluid not stability economy of ORC. Withperformance the increasing on working fluids, itprotection is difficultand to safety. find a pure workingzeotropic fluid not only withand satisfied thermodynamic butrequirements also permissible enverimental In contrast, District heating networks are commonly in working the literature asisone of the mostthe effective solutions for decreasing the only withfluid, satisfied thermodynamic also permissible and safety. Inofcontrast, zeotropic working which is mixed withperformance two oraddressed morebut pure fluids,enverimental easier to protection meet requirements thermos-physical greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat working fluid, which is mixed with two or the more pure stage, working is easier to meet working the requirements of thermos-physical properties, environmental and safety. But at present the fluids, application of zeotropic fluids in ORC still adapted or sales. Dueenvironmental to the changed climate conditions and building policies, heat working demand fluids in theinfuture could decrease, properties, safety. But at what the present stage, therenovation application zeotropic ORCthe still adapted or employed the methodologyand originated from we learn from pure workingoffluids. Under such circumstances, temperature prolonging the investment return period. employed the methodology originated fromsystem what we learn from pure fluids.shift Under suchincircumstances, the temperature glide of zeotropic working fluids improves efficiency while theworking composition would turn reduce system efficiency. The of main scope of this paper is to assess the feasibility of using thethe heat demand – outdoor temperature function for heat demand glide zeotropic shift on would in turn reduce system efficiency. Thus, 3D-ORC is working proposedfluids in thisimproves paper tosystem provideefficiency zeotropicwhile working composition fluids a full play performance improvement of energy forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 Thus, 3D-ORC proposed in this paper to provide zeotropic fluidsofa full play on of performance improvement of energy conversion. Theisperformance of 3D-ORC is calculated for working the recovery waste heat internal combustion engines and buildingswith that vary in both construction and typology. weather scenarios (low, medium, high) and three district conversion. Thethe performance ofusing 3D-ORC is calculated for theThree recovery of results waste heat ofthat internal combustion and compared simple ORC pureperiod and zeotropic working fluids. The show the performance ofengines 3D-ORC is renovation scenarios wereORC developed pure (shallow, intermediate, deep). To estimate theshow error,that obtained heat demand values were compared theORC simple and zeotropic working fluids. The results the performance of 3D-ORC is better thanwith simple under theusing same conditions. compared with results dynamic heat demand model, previously developed and validated by the authors. better than simple ORC from underathe same conditions. The results that when weather change is considered, the margin of error could be acceptable for some applications Copyright © showed 2018 Elsevier Ltd. only All rights reserved. ©(the 2019 The Published by Elsevier Ltd.20% for all weather scenarios considered). error annual demand was lower However, after introducing renovation Copyright ©inAuthors. 2018 Elsevier Ltd. Allresponsibility rights than reserved. Selection and peer-review under of the scientific committee of the 10th International Conference on Applied This is an open accessvalue article under theupCC BY-NC-ND license on (http://creativecommons.org/licenses/by-nc-nd/4.0/) scenarios, the error increased to 59.5% (depending the weather and renovation scenarios Conference combination on considered). th Selection and peer-review under responsibility of the scientific committee of the 10 International Applied Energy (ICAE2018). Peer-review under responsibility of the scientific committee of ICAE2018 –ofThe 10thupInternational Conference oncorresponds Applied Energy. The value of slope coefficient increased on average within the range 3.8% to 8% per decade, that to the Energy (ICAE2018). decrease organic in the Rankine number cycle; of heating hours of 3D 22-139h during3D-ORC the heating season (depending on the combination of weather and Keywords: ORC; zeotropic; construction; renovation scenarios considered). the other hand, function intercept increased for 7.8-12.7% per decade (depending on the Keywords: organic Rankine cycle; ORC;On zeotropic; 3D construction; 3D-ORC coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
© 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +86-022-27890051; fax: +86-022-27404188.
address:author. [email protected] * E-mail Corresponding Tel.: +86-022-27890051; fax: +86-022-27404188. Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility the scientific 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.374
Weicong Xu et al. / Energy Procedia 158 (2019) 1591–1597 Weicong Xu et al./ Energy Procedia 00 (2018) 000–000
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1. Introduction As an efficient way to convert medium- and low-temperature heat into power, subcritical organic Rankine cycle (ORC) has received much attention from many scholars. The thermos-physical properties parameters, transport parameters and other parameters of working fluid, which is the “blood” of ORC, could directly affect the efficiency, safety, stability and economy of ORC [1]. However, the working fluid also causes many irreversible losses in cycle. Therefore, in order to improve the efficiency of ORC, the bottleneck problem of working fluid has to be solved firstly. At present, pure working fluids are used in most of the subcritical ORC. In addition to considering the thermosphysical properties of working fluid, the safety and environmental protection factors are becoming more and more important during working fluid selection. Considering the above factors comprehensively, the pure working fluids which could be applied in ORC perfectly has been very few. Furthermore, there is no suitable pure working fluid under majority conditions. However, there are bottlenecks in the design and development of novel pure working fluid, such as low accuracy of computational model [2] and poor economic of commercial production [3]. In contrast, zeotropic working fluids, which are produced by a simple mixing of two or more pure working fluids, are easier to meet the requirements of thermos-physical properties, environmental and safety. Therefore, zeotropic working fluids will be the main carrier of the ORC in the future. Zeotropic working fluids are mixtures consisting of two or more pure working fluids with different boiling temperature. At the gas-liquid equilibrium state, the gas and liquid phases of the zeotropic working fluids have different components. Therefore, temperature glide and composition shift are typical characteristics of zeotropic working fluids. The reason of temperature glide and composition shift is the composition variation of gas and liquid phase during phase transformation. By using temperature glide, the cycle performance could be improved by reducing the irreversible loss in heat transfer process. But the composition shift would reduce the performance of ORC. Therefore, there are contradictions in the study of the ORC using zeotropic working fluids, which limits the extensive application of zeotropic working fluids in practical engineering. In this paper, the existing researches on ORC using zeotropic working fluids were summarized to find out the reasons resulting in this contradiction firstly. Then, a 3D thermodynamic cycle construction method was applied to give full play to the advantages of zeotropic working fluids. Lastly, a specific case was comparatively analyzed. 2. State of the art 2.1. Temperature glide The irreversible loss in the heat transfer process of ORC could be reduced by matching the temperature changes of heat transfer fluid and the zeotropic working fluid. Table 1 summarizes the researches of ORC using zeotropic working fluids, which provided relatively detailed data. The contents listed in the table include research time, author, working fluid, heat source, heat sink, research method and research results. The research results show that the relative change values of the performance of zeotropic working fluids compared with pure working fluids from the aspects of net output (Wnet), thermal efficiency (ηⅠ) and the efficiency of the second law of thermodynamics (ηⅡ). In general, the performance of ORC using zeotropic working fluids is better than that of ORC with pure working fluids. However, it is worth noting that under some conditions, the using of zeotropic working fluid could also reduce the thermal efficiency and the efficiency of the second law of thermodynamics of ORC. Table 1. Summary of researches on ORC using zeotropic working fluids. Time
Author
Working fluid
Heat source
Research method
Research results
ΔWnet
ΔηⅠ
ΔηⅡ
(%)
(%)
(%)
2009
Wang et. al [4]
R245fa/R152a (0.45/0.55)
Hot water (85℃)
theoretical analysis
+2.18
-12.26
-12.26
2011
Heberle et. al [5]
R600a/R601a (0.9/0.1)
Hot water (120℃)
theoretical analysis
+11.90
-
+8.20
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2012
Chys et. al [6]
R601a/hexane (0.43/0.57)
Hot water (150℃)
theoretical analysis
+12.30
+15.70
-
2013
Liu et. al [7]
R600a/R601 (0.94/0.06)
Hot water (140℃)
theoretical analysis
+8.10
-
-
2014
Lecompte et. al [8]
R600a/R601a (0.81/0.19)
Hot water (150℃)
theoretical analysis
+27.20
-4.30
+6.10
2014
Dong et. al [9]
MM/MDM (0.4/0.6)
Hot oil (280℃)
theoretical analysis
-
+5.96
+4.45%
2015
Song et. al [10]
Cyclohexane/R141b (0.5/0.5)
Exhaust gas (300℃)
theoretical analysis
+13.30
-
-
2016
Lu et. al [11]
R245fa/R600a (0.65/0.35)
Hot water (140℃)
theoretical analysis
+9.58
+3.22
-
2016
Wang et. al [12]
R601a/R600a (0.6/0.4)
Hot oil (115℃)
experimental study
+25.00
-
-
2017
Pang et. al [13]
R245fa/R123 (0.66/0.34)
Hot oil (120℃)
experimental study
+6.4
+12.80
-
2.2. Composition shift The composition variation during phase transformation also brings about another phenomenon, that is, composition shift. The difference between the charge composition and circulating composition of zeotropic working fluid is composition shift. The main reasons leading to the composition shift of zeotropic working fluid could be attributed to: (a) the velocity difference between gas and liquid phase; (b) solubility difference of different components in lubricating oil; (c) the volume difference of the system and the leakage. A summary of researches on composition shift of zeotropic working fluid with detailed data is listed in Table 2. The value of composition shift is equal to the maximum difference between charge composition and circulating composition. ΔηⅠ is equal to the relative change values of system thermal efficiency using circulating composition compared with using charge composition. The results show that the values of composition shift are between 0.68% and 6.40%. And the composition shift causes the reduction of the system performance. Table 2. Summary of researches on composition shift of zeotropic working fluid. Author
Working fluid
Research method
Composition shift (%)
ΔηⅠ (%)
2004
Chen et. al [14]
R32/Rl34a
theoretical analysis
3.39
-
2005
Youbi-Idrissi et. al [15]
R407C
theoretical analysis
3.00
-
2006
Chen et. al [16]
R23/R134a
experimental study
0.68
-
2011
Bao et. al [17]
R407C
theoretical analysis
5.80
-
Time
2011
Chen et. al [18]
R23/R152
experimental study
6.40
-
2012
Fukuda et. al [19]
R1234ze(E)/R32
experimental study
5.00
-1.79
2012
Xu et. al [20]
R290/R600a
experimental study
4.10
-
2014
Zhao et. al [21]
R600a/R601
theoretical analysis
3.74
-6.79
2016
Bao et. al [22]
R600a/R601
experimental study
1.15
-
2017
Zhou et. al [23]
R227ea/R245fa
theoretical analysis
3.74
-0.34
In summary, the application of zeotropic working fluid could improve the performance of ORC under most of the conditions. But the application of zeotropic working fluids in ORC commonly employ the traditional methodology originate from knowledge gained from pure working fluids, which would lead to the adverse effects of the composition shift of zeotropic working fluid. This means that under existing methods, the advantages of zeotropic working fluids have not been fully realized. 3. 3D thermodynamic cycle 3.1. Methodology In previous studies, we proposed the 3D thermodynamic cycle construction method in [24]. The core of this method is to construct an efficient thermodynamic cycle by using different working fluids to meet different requirements of the thermos-physical properties of working fluids in different thermodynamic processes. At the
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aspect of thermodynamic analysis method, the dimension of working fluid is added to the traditional T-S diagram to clearly indicate the change of working fluids in circulation, as shown in Fig. 1.
Fig. 1. The principle diagram of the 3D construction method[24]
According to this method, the actual cycle process is A1→B1→B2→C2→C1→D1→D2→A2→A1, as follows. A1→B1：The working fluid used in this process is X, which could meet the temperature matching requirements of the heat source in the evaporation process; B1→B2：The working fluid is switched from X to Y; B2→C2：The working fluid used in this process is Y, which could meet the requirements of the expansion process on the thermos-physical properties of working fluids. C2→C1：The working fluid is switched from Y to X; C1→D1：The working fluid used in this process is X, which could meet the temperature matching requirements of the heat sink in the condensation process; D1→D2：The working fluid is switched from X to Y; D2→A2：The working fluid used in this process is Y, which could meet the requirements of the compression process on the thermos-physical properties of working fluids. A2→A1：The working fluid is switched from Y to X; The ultimate goal of this thermodynamic cycle is to approach the Carnot cycle by means of various working fluids in different thermodynamic processes. By combining this method with zeotropic working fluids, the switching of working fluids in different processes could be achieved by using the composition variation of gas and liquid phase during phase transformation. This method could not only make reasonable use of temperature glide of zeotropic working fluids, but also solve the problems caused by composition shift. The feasibility and superiority of this method are verified by a case studied in the section 3.2. 3.2. Case study The recovery of waste heat is an effective way to improve the thermal efficiency of internal combustion engines. The waste heat of internal combustion engine usually comes from exhaust gas and jacket water, whose temperature is 500℃-900℃ and 90℃-100℃, respectively [25]. A large number of thermodynamic cycles have been carried out by scholars for the recovery and utilization of internal combustion engine waste heat. But there is no consistent conclusion for the optimal cycle. From the perspective of working fluids, each working fluid should have the best operating conditions. In order to adapt to the characteristics of large temperature difference of internal combustion engine waste heat, this paper compares the Benzene, which has higher critical temperature, and R245fa, which has lower critical temperature. During comparison, the high temperature in cycle is set from 300K to critical temperature with the interval of 2K. The temperature difference of the cycle is set to 20K. The thermal efficiency and thermodynamic perfection of a
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7 6
(a)
352K
5 4 3
Benzene R245fa
2 1
320
360
400
440
480
520
Thermodynamic perfection (%)
Thermal efficiency (%)
simple ORC using Benzene and R245fa are calculated in this temperature range. The results are shown in Fig 2. When the high temperature is less than 352K, the thermal efficiency and thermodynamic perfection of ORC using R245fa are higher than that of ORC using Benzene. While the high temperature is greater than 352K, ORC using Benzene shows better performance. Therefore, the waste heat in different temperature ranges should be recovered by using different working fluids. As a result, 3D-ORC for internal combustion engine waste heat recovery is proposed by using the 3D construction method. The system schematic diagram and the 3D thermodynamic cycle diagram are shown in fig. 3(a) and fig. 3(b) respectively. 100
(b)
352K
90 80
Benzene R245fa
70 60
320
High temperature (K)
360
400
440
480
520
High temperature (K)
Fig. 2. Comparison results of R245fa and Benzene: (a) thermal efficiency; (b) thermodynamic perfection 4 3
T P
separator sight glass P T
expanderⅠ 5
6
evaporatorⅠ
7 P T
pumpⅡ
2
T/K
P T
evaporatorⅡ
3 2 1
4
P T
pumpⅠ
8
P T
expanderⅡ
T P
10
9
mixer 9
R245fa/Benzene (0.11/0.89)
8
1
T P
T P
10
7
6 5
P T
s/kJ·kg-1·K-1
R245fa/Benzene (0.3/0.7)
θ/% R245fa/Benzene (0.49/0.51)
(a) (b) Fig. 3. 3D-ORC: (a) system schematic diagram; (b) 3D thermodynamic cycle diagram
The zeotropic working fluid R245fa/Benzene is applied in 3D-ORC. The adjustment of the composition of working fluid is realized by the separation of gas and liquid phases in separator. In order to research the advantages of 3D-ORC, the performance is compared with the simple ORC using pure and zeotropic working fluid. A detailed mathematical model of 3D-ORC is established to calculate the whole system performance, as shown in Table 3. The 3D-ORC is better than the simple using pure or zeotropic working fluids in terms of net output, thermal efficiency and thermodynamic perfection. Table 3. Mathematical model of 3D-ORC. Component/Efficiency Pump Ⅰ Evaporator Ⅰ Separator Pump Ⅱ Evaporator Ⅱ
Equation = WpumpΙ mwf_Ι (h2 − h1 ) pumpΙ = Qeva Ι m= C p_hseΙ mhseΙ (ThseΙ_in − ThseΙ_out ) wf_Ι (h3 - h2 ) mwf_П= (1 − x)mwf_Ι ; mwf_Ш = xmwf_Ι ; m = mwf_Π h5 + mwf_Ш h4 wf_Ι h3 = WpumpΠ mwf_Π (h6 − h5 ) pumpΠ
= Qeva П m= C p_hseП mhseП (ThseП_in − ThseП_out ) wf_П (h7 - h6 )
Expander Ⅰ
= WexpΙ mwf_Ш (h4 − h9 )expΙ
ExpanderⅡ
= WexpП mwf_П (h6 − h7 )expП
Mixer
m= mwf_Π h8 + mwf_Ш h9 ; m = mwf_Π + mwf_Ш wf_Ι h10 wf_Ι
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= Qcon m= Cp_hsk mhsk (Thsk_out − Thsk_in ) wf_І (h10 - h1 )
Condenser Net power
Wnet =WexpІ +WexpП − WpumpІ − WpumpП
Thermal efficiency
thermal = Wnet (QevaΙ +QevaП )
Thermodynamic perfection
therm_perf = thermal Carnot
Table 4. Comparison results between 3D-ORC and simple ORC. Parameters
Simple ORC [26]
3D-ORC
Temperature of exhaust gas (K)
771.15
771.15
771.15
-1
Mass flow of exhaust gas (kg·s )
0.2586
0.2586
0.2586
Temperature of jacket water (K)
365.25
365.25
365.25
Mass flow of jacket water (kg·s )
2.1
2.1
2.1
Inlet temperature of cooling water (K)
288.15
288.15
288.15
Working fluid
R245fa
R245fa/Benzene (0.3/0.7)
R245fa/Benzene (0.3/0.7)
-1
Net output (kW)
13.7
15.6
39.84
Thermal efficiency (%)
9.4
11.4
15.42
Thermodynamic perfection (%)
27.17
30.94
40.92
4. Conclusions In order to solve the problems existing in the application of zeotropic working fluids, this paper presents a method to give full play to the advantages of zeotropic working fluids. The existing literatures on the ORC using zeotropic working fluids are summarized briefly. Most of the studies show that ORC using zeotropic working fluids has better performance than that of pure working fluids. But the efficiency of ORC would be reduced due to the composition shift of zeotropic working fluid. Based on the 3D construction method of thermodynamic cycle, 3DORC is proposed, which could not only make reasonable use of temperature glide of zeotropic working fluids, but also solve the problems caused by composition shift. According to theoretical analysis, the performance of 3D-ORC is better than that of simple ORC using pure or zeotropic working fluids. Acknowledgements This work is supported by the National Nature Science Foundation of China under Grant No.51776138, Innovation Development and Demonstration Project of Ocean Economy under Grant No. BHSF2017-19 and Tianjin Talent Development Special Support Program for High-Level Innovation and Entrepreneurship Team. References [1]. [2]. [3]. [4]. [5]. [6]. [7].
Bao J, Zhao L. A review of working fluid and expander selections for organic Rankine cycle. Renewable & Sustainable Energy Reviews, 2013, 24(10):325-342. Lampe M, Stavrou M, Bücker H M, et al. Simultaneous Optimization of Working Fluid and Process for Organic Rankine Cycles Using PC-SAFT. Industrial & Engineering Chemistry Research, 2014, 53(21):8821–8830. Linke P, Papadopoulos A I, Seferlis P. Systematic Methods for Working Fluid Selection and the Design, Integration and Control of Organic Rankine Cycles—A Review. Energies, 2015, 8(6):4755-4801. Wang X D, Zhao L. Analysis of zeotropic mixtures used in low-temperature solar Rankine cycles for power generation. Solar Energy, 2009, 83(5):605-613. Heberle F, Preißinger M, Brüggemann D. Zeotropic mixtures as working fluids in Organic Rankine Cycles for low-enthalpy geothermal resources. Renewable Energy, 2012, 37(1):364-370. Chys M, Broek M V D, Vanslambrouck B, et al. Potential of zeotropic mixtures as working fluids in organic Rankine cycles. Energy, 2012, 44(1):623-632. Liu Q, Duan Y, Yang Z. Effect of condensation temperature glide on the performance of organic Rankine cycles with zeotropic mixture
[8]. [9]. [10]. [11]. [12]. [13]. [14]. [15]. [16]. [17]. [18]. [19]. [20]. [21]. [22]. [23]. [24]. [25]. [26].
Weicong Xu et al. / Energy Procedia 158 (2019) 1591–1597 Author name / Energy Procedia 00 (2018) 000–000
1597 7
working fluids. Applied Energy, 2014, 115(4):394-404. Lecompte S, Ameel B, Ziviani D, et al. Exergy analysis of zeotropic mixtures as working fluids in Organic Rankine Cycles. Energy Conversion & Management, 2014, 85(9):727-739. Dong B, Xu G, Cai Y, et al. Analysis of zeotropic mixtures used in high-temperature Organic Rankine cycle. Energy Conversion & Management, 2014, 84:253-260. Song J, Gu C W. Analysis of ORC (Organic Rankine Cycle) systems with pure hydrocarbons and mixtures of hydrocarbon and retardant for engine waste heat recovery. Applied Thermal Engineering, 2015, 89:693-702. Lu J, Zhang J, Chen S, et al. Analysis of organic Rankine cycles using zeotropic mixtures as working fluids under different restrictive conditions. Energy Conversion & Management, 2016, 126:704-716. Wang Y, Liu X, Ding X, et al. Experimental investigation on the performance of ORC power system using zeotropic mixture R601a/R600a. International Journal of Energy Research, 2017, 41(5). Pang K C, Chen S C, Hung T C, et al. Experimental study on organic Rankine cycle utilizing R245fa, R123 and their mixtures to investigate the maximum power generation from low-grade heat. Energy, 2017, 133. Chen J. Comprehensive approach to predicting the circulation composition of zeotropic refrigerants. Journal of Southeast University (English Edition), 2004, 20(3):315-318. Youbi-Idrissi M, Bonjour J, Meunier F. Local shifts of the fluid composition in a simulated heat pump using R-407C. Applied Thermal Engineering, 2005, 25(17):2827-2841. Chen J, K.Beermann. New problems in the composition shift of zeotropic working fluids (In Chinese). National Symposium on New technology of refrigeration and air conditioning. 2006. Bao J, Zhao L, Song W. Theoretical Investigation on the Influence of Composition Shift on the Heat Exchange during the Phase Change Using R407C (In Chinese). Journal of Mechanical Engineering, 2011, 47(16):127-132. Chen J, Kruse H. Calculating Circulation Concentration of Zeotropic Refrigerant Mixtures. Hvac & R Research, 2011, 1(3):219-231. Fukuda S, Takata N, Koyama S. The Circulation Composition Characteristic of the Zeotropic Mixture R1234ze(E)/R32 in a Heat Pump Cycle. Faseb Journal, 2012, 24. Xu X, Liu J, Cao L, et al. Local composition shift of mixed working fluid in gas–liquid flow with phase transition. Applied Thermal Engineering, 2012, 39(4):179-187. Zhao L, Bao J. The influence of composition shift on organic Rankine cycle (ORC) with zeotropic mixtures. Energy Conversion & Management, 2014, 83(4):203-211. Bao J, Zhao L. Experimental research on the influence of system parameters on the composition shift for zeotropic mixture (isobutane/pentane) in a system occurring phase change. Energy Conversion & Management, 2016, 113:1-15. Zhou Y, Zhang F, Yu L. The discussion of composition shift in organic Rankine cycle using zeotropic mixtures. Energy Conversion & Management, 2017, 140:324-333. Xu W, Deng S, Su W, et al. How to approach Carnot cycle via zeotropic working fluid: Research methodology and case study. Energy, 2018, 144:576-586. Wang T, Zhang Y, Peng Z, et al. A review of researches on thermal exhaust heat recovery with Rankine cycle. Renewable & Sustainable Energy Reviews, 2011, 15(6):2862-2871. Yu G, Shu G, Tian H, et al. Simulation and thermodynamic analysis of a bottoming Organic Rankine Cycle (ORC) of diesel engine (DE). Energy, 2013, 51(9):281-290.