## 1 Introduction  
Currently, internal combustion engines (ICEs) are still the main power for transportation. Energy conservation and emission reduction are two critical tasks for the ICE industry all over the world. Organic Rankine cycle (ORC) is a feasible technology to recover the waste heat of an ICE so that the energy efficiency can be enhanced apparently. Compared with other technologies such as improvements of the combustion and friction, the utilization of waste heat has a greater potential for energy conservation and emission reduction. ORC technology is a method that can generate power from a low-temperature heat source such as the waste heat of the exhaust and the coolant of an ICE. For exhaust heat recovery, the working fluid of the ORC absorbs heat from the exhaust and outputs power via an expander. Hence, the total power output and the energy efficiency of the ICE-ORC system are increased [1]. The emissions of the ICE also decrease due to a reduction of the fuel consumption [2]. There are various waste heat recovery technologies such as the thermoelectric generator, steam Rankine cycle, and Kalina cycle. However, ORC technology has a high thermal efficiency and good security, which has drawn extensive attentions in recent years [3]. There are many parameters that will influence the performance of an ORC [4; 5]. The selection of the organic working fluid is very important [6; 7]. [PERSON] et al. selected an alkane as the working fluid and compared the performance indicators including the thermal efficiency, the work output, and the expander size parameters. The results showed that the performances of cycloalkanes such as cyclohexane were relatively superior. However, the condensing pressure of the alkanes was low. Thus, it was difficult to realize subcooling in an actual working system [8]. [PERSON] et al. compared the performances of an ORC using R113, R123, R245 fa, ethanol, and water. It was concluded that ethanol and R113 had better performances. However, R113 and R123 belonged to CFCs (chlorofluocarbon), which violated the requirements for green energy and environmental protection. Ethanol and R245 fa were more suitable [9]. [PERSON] et al. analyzed the optimal performances of different working fluids for various power cycles using the same waste heat. The results indicated that the ORC was superior to the steam cycle and the converting efficiency from low-grade waste heat to useful energy was higher [10]. [PERSON] et al. analyzed the performances of different working fluids in specific operation regions by using the thermodynamic model built by MATLAB and REFPROP. The results showed that the thermodynamic performances of R11, R141b, R113, and R123 were slightly higher than those of the others. However, R245 fa and R245 ca were environmentally-friendly fluids and more suitable for the waste heat recovery of engines [11]. [PERSON] et al. compared the economic performances of an ORC using R123 and R245 fa as working fluids and the influences of the operation parameters were evaluated [12]. Although there are many investigations devoted to the ORC system for waste heat recovery of ICE, this technology still faces huge difficulty for practical application. [PERSON] et al. analyzed six different architectures of ORC using ten non-flammable working fluids for waste heat recovery of jacket cooling water and the double regenerative ORC using SES36 achieved the maximum net efficiency of 7.15 [13]. [PERSON] et al. designed a two-parallel-step ORC configuration to recover waste heat from the engine coolant and the exhaust gas simultaneously [14]. [PERSON] et al. proposed a dual-loop ORC system to recover the exhaust and coolant waste heat that could improve the fuel efficiency evidently [15]. [PERSON] et al. evaluated the performance of different ORCs with various working fluids [16]. [PERSON] and [PERSON] [17] and [PERSON] et al. [18] summarized the recent investigations on engine waste heat recovery and [PERSON] et al. [19] reviewed the relevant patents. [PERSON] et al.