Performance comparison of organic Rankine cycle with expansion from superheated zone or two-phase zone based on temperature utilization rate of heat source Hongchuang Sun a , Jiang Qin a, * , Tzu-Chen Hung b, ** , Chih-Hung Lin b , Yi-Fan Lin b a Key Laboratory of Aerospace Thermophysics, Ministry of Industry and Information Technology, School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, PR China b Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan, ROC article info Article history: Received 14 November 2017 Received in revised form 27 December 2017 Accepted 10 February 2018 Available online 13 February 2018 Keywords: Small-scale organic Rankine cycle Temperature utilization rate of heat source Classification of expansion process Rotary vane pump abstract The temperature utilization rate of heat source is defined to evaluate the energy utilization rate of organic Rankine cycles (ORCs). Rotary vane pump, plate heat exchangers and scroll expander are adopted to compare the performance of ORCs with expansion from superheated zone or two-phase zone. The results show that temperature utilization rate increases with the increase of mass flow rate of working fluid and the decrease of mass flow rate of heat source. The working conditions are classified into three types of A, B and C according to starting zone of expansion. The temperature utilization rate keeps almost unchanged for types B and C, but the net electric power output efficiency decreases obviously with the increase of working fluid mass flow. The maximum thermal efficiency, net electric power output effi- ciency and isentropic efficiency of expander are obtained as 6.1%, 3.01% and 83.5%, respectively. The maximum temperature utilization rate can reach 64.4% with the decrease of heat source mass flow. Furthermore, the rotary van pump is suitable for small-scale ORC with stable volume flow rate, relative high efficiency, good sealing condition and long service life. The highest isentropic efficiency and elec- tricity consumption efficiency of pump are 46.1% and 39.8%, respectively. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction The utilization of low/medium temperature heat source has far- reaching implications for reducing the energy consumption. Improving the energy utilization rate and utilizing new energy are the effective ways to ease energy crisis and solve environmental problem. Organic Rankine cycle (ORC) has advantages in utilizing low/medium temperature heat sources such as solar energy [1], geothermal energy [2,3], industrial waste heat and exhaust heat of engine [4,5], due to the low boiling point of organic working fluids. These low temperature energy resources are widely scattered and can be unstable. Even though the heat sources providing energy to the ORC significantly impact the theoretical analyses and system designs of ORC, however, the behaviors of these heat sources have received little attention over the past few decades [6]. In order to recover energy from waste heat source more effi- ciently, matching suitable working fluids with different heat sour- ces, optimizing system structures and improving components’ characters are widely implemented in the past decade to reduce irreversible lost on heat transfer process and improve system effi- ciency. Plenty of researchers have carried out studies on thermal efficiency, exergy efficiency, net work output and thermo-economic to optimize ORC. The influencing factors are such as evaporating pressure, superheating, pinch temperature, condensing pressure, subcooling and mass flow rate of working fluid [7]. Shu et al. [8] compared the performance of bottoming ORC with 20 working fluids and found R245fa, R123 and R141b had better performance than others in terms of power output and thermal efficiency. Invernizz et al. [9] proposed an increase of 30%e40% of thermal efficiency with esa-methyl-disiloxane used as working fluid for heat source among 250e300  C. Hung et al. [10e12] carried out a series of experiment to screen suitable Chloro-fluoro-carbon for increasing system efficiency with different temperatures of heat source [11]. Shu et al. [13, 14], investigated the thermal efficiency, * Corresponding author. No.92, West Da-Zhi Street, Harbin, Heilongjiang,150001, PR China. ** Corresponding author.1, Sec. 3, Zhongxiao E. Road, Taipei, Taiwan, ROC. E-mail addresses: qinjiang@hit.edu.cn (J. Qin), tchung@ntut.edu.tw (T.-C. Hung). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy https://doi.org/10.1016/j.energy.2018.02.047 0360-5442/© 2018 Elsevier Ltd. All rights reserved. Energy 149 (2018) 566e576