Charge-based studies, in particular investigations of mass distribution, are still almost absent, although the efficiency of the organic Rankine cycle (ORC) has attracted a great deal of scholarly attention. This paper aims to provide a new perspective on the intrinsic relationship among the mass distribution, phase-zone distribution in the heat exchanger (HEX), charge of working fluid (WF), rotation speed of the pump (RSP), and system performance. A comprehensive ORC simulation model is presented by linking each component’s sub-models, including the independent models for HEX, pump, and expander in an object-oriented fashion. The visualization study of mass distribution of the WF in the system is investigated under different working conditions. Furthermore, the volume and mass of the gas phase, two-phase and liquid phase of WF in the HEX and their variation rules are analyzed in-depth. Finally, the strategies of charge reduction considering HEX areas and pipe sizes are investigated. The results show that the model based on the interior-point method provides high levels of accuracy and robustness. The mass ratio of the WF is concentrated in the liquid receiver, especially in the regenerator, which is 32.9% and 21.9% of the total mass, respectively. Furthermore, 2.4 kg (6.9%) WF in the system gradually migrates to the hightemperature side as the RSP increases while 6.1 kg (17.4%) WF migrates to the low-temperature side, especially to the condenser, as the charge in the system increases. Output power and efficiency both decrease gradually after the peak due to changes in RSP and charge. Last, reducing heat transfer areas of the condenser and regenerator is the most effective way to reduce WF charge.
[1] MARAVER D, ROYO J, LEMORT V, et al. Systematic optimization of subcritical and transcritical organic Rankine cycles (ORCs) constrained by technical parameters in multiple applications [J].Applied Energy, 2014, 117: 11-29.
[2] TIAN H, SHU G Q, WEI H Q, et al. Fluids and parameters optimization for the organic Rankine cycles (ORCs) used in exhaust heat recovery of Internal Combustion Engine (ICE) [J]. Energy, 2012, 47(1): 125-136.
[3] SHU G Q, ZHAO M R, TIAN H, et al. Experimental comparison of R123 and R245fa as working fluids for waste heat recovery from heavy-duty diesel engine [J]. Energy, 2016, 115: 756-769.
[4] MUHAMMAD U, IMRAN M, LEE D H, et al. Design and experimental investigation of a 1 kW organic Rankine cycle system using R245fa as working fluid for low-grade waste heat recovery from steam [J]. Energy Conversion and Management, 2015, 103: 1089-1100.
[5] YE Z H, YANG J Y, SHI J Y, et al. Thermo-economic and environmental analysis of various low-GWP refrigerants in Organic Rankine cycle system [J]. Energy, 2020, 199: 117344.
[6] LIU L C, ZHU T, GAO N P, et al. A review of modeling approaches and tools for the off-design simulation of organic Rankine cycle [J]. Journal of Thermal Science, 2018, 27(4): 305-320.
[7] IBARRA M, ROVIRA A, ALARC′ ON-PADILLA D C, et al. Performance of a 5 kWe Organic Rankine Cycle at part-load operation [J]. Applied Energy, 2014, 120: 147-158.
[8] DICKES R, DUMONT O, DACCORD R, et al. Modelling of organic Rankine cycle power systems in off- design conditions: An experimentally-validated comparative study [J]. Energy, 2017, 123: 710-727.
[9] WEI D H, LU X S, LU Z, et al. Dynamic modeling and simulation of an organic Rankine cycle (ORC) system for waste heat recovery [J]. Applied Thermal Engineering, 2008, 28(10): 1216-1224.
[10] QUOILIN S, AUMANN R, GRILL A, et al. Dynamic modeling and optimal control strategy of waste heat recovery organic Rankine cycles [J]. Applied Energy, 2011, 88(6): 2183-2190.
[11] SHEN G F, YUAN F, LI Y, et al. The energy flow method for modeling and optimization of organic Rankine cycle (ORC) systems [J]. Energy Conversion and Management, 2019, 199: 111958.
[12] ZHANG Y, DENG S, ZHAO L, et al. Dynamic test and verification of model-guided ORC system [J]. Energy Conversion and Management, 2019, 186: 349-367.
[13] HU D S, ZHENG Y, WU Y, et al. Off-design performance comparison of an organic Rankine cycle under different control strategies [J]. Applied Energy, 2015, 156: 268-279.
[14] MANENTE G, TOFFOLO A, LAZZARETTO A, et al. An organic Rankine cycle off-design model for the search of the optimal control strategy [J]. Energy, 2013, 58: 97-106.
[15] SCHUSTER S, MARKIDES C N, WHITE A J. Design and off-design optimisation of an organic Rankine cycle(ORC) system with an integrated radial turbine model [J]. Applied Thermal Engineering, 2020, 174: 115192.
[16] SONG J, GU C W, REN X D. Parametric design and off-design analysis of organic Rankine cycle (ORC) system [J]. Energy Conversion and Management, 2016, 112: 157-165.
[17] LI H, HU D S, WANG M K, et al. Off-design performance analysis of Kalina cycle for low temperature geothermal source [J]. Applied Thermal Engineering, 2016, 107: 728-737.
[18] MOHAMMADKHANI F, YARI M. A 0D model for diesel engine simulation and employing a transcritical dual loop organic Rankine cycle (ORC) for waste heat recovery from its exhaust and coolant: Thermodynamic and economic analysis [J]. Applied Thermal Engineering, 2019, 150: 329-347.
[19] HUSTER W R, VAUPEL Y, MHAMDI A, et al. Validated dynamic model of an organic Rankine cycle(ORC) for waste heat recovery in a diesel truck [J]. Energy, 2018, 151: 647-661.
[20] ZIVIANI D, WOODLAND B, GEORGES E, et al. Development and a validation of a charge sensitive organic Rankine cycle (ORC) simulation tool [J]. Energies, 2016, 9(6): 389.
[21] LIU L C, ZHU T, MA J C. Working fluid charge oriented off-design modeling of a small scale organic Rankine cycle system [J]. Energy Conversion and Management, 2017, 148: 944-953.
[22] DICKES R, DUMONT O, GUILLAUME L, et al. Charge-sensitive modelling of organic Rankine cycle power systems for off-design performance simulation [J]. Applied Energy, 2018, 212: 1262-1281.
[23] DICKES R, DUMONT O, QUOILIN S, et al. Online measurement of the working fluid mass repartition in a small-scale organic Rankine cycle power system [C]//17th International Refrigeration and Air Conditioning Conference. West Lafayette: Purdue University, 2018: 2630.
[24] LIU L C, ZHU T, WANG T T, et al. Experimental investigation on the effect of working fluid charge in a small-scale organic Rankine cycle under off-design conditions [J]. Energy, 2019, 174: 664-677.
[25] POGGI F, MACCHI-TEJEDA H, LEDUCQ D, et al. Refrigerant charge in refrigerating systems and strategies of charge reduction [J]. International Journal of Refrigeration, 2008, 31(3): 353-370.
[26] KNABBEN F T, RONZONI A F, HERMES C J L. Effect of the refrigerant charge, expansion restriction, and compressor speed interactions on the energy performance of household refrigerators [J]. International Journal of Refrigeration, 2021, 130: 347-355.
[27] GARDENGHI ′A R, LACERDA J F, TIBIRIC? ′A C B, et al. Numerical and experimental study of the transient behavior of a domestic vapor compression refrigeration system: Influence of refrigerant charge and ambient temperature [J]. Applied Thermal Engineering, 2021, 190: 116728.
[28] LEMORT V, QUOILIN S, CUEVAS C, et al. Testing and modeling a scroll expander integrated into an organic Rankine cycle [J]. Applied Thermal Engineering, 2009, 29(14/15): 3094-3102.
[29] CHISHOLM D. Two-phase flow in heat exchangers and pipelines [J]. Heat Transfer Engineering, 1985, 6(2): 48-57.
[30] COOPER M G. Heat flow rates in saturated nucleate pool boiling: A wide-ranging examination using reduced properties [J]. Advances in Heat Transfer, 1984, 16: 157-239.
