Working Fluid Pump Research Articles

Experimental study on hydraulic performance and cavitation characteristics of a R134a refrigerant self-lubricating centrifugal pump

As the primary power equipment in pump flooding cooling systems, the efficiency and performance of mechanical pumps play a crucial role in two-phase cooling systems. A high-speed centrifugal pump with self-lubricating working fluid was designed with a speed of 7500 rpm and a flow coefficient of 0.0506. The hydraulic and cavitation performance of the pump were tested with R134a as the working fluid. The results show that the working fluid pump is capable of efficiently pumping R134a with an efficiency of 40.3% and a head coefficient of 0.988 under the design condition. Within the tested range of inlet temperature from 5°C to 15°C, the flow coefficient from 0.01 to 0.105, and the height of the refrigerant tank from 1.4 m to 5 m, lower net positive suction heads available at the same flow rate will reduce the pump head, increase power consumption, and decrease efficiency. Increasing the pump speed from 3000 rpm to 7500 rpm can improve the pump's performance. At 6000 rpm, the critical cavitation number of the working fluid pump increases with the increase in flow coefficient. At 7500 rpm, the critical cavitation number has a minimum value when the flow coefficient φ = 0.0434. At the design speed and flow rate, both the critical cavitation coefficient and fracture cavitation number increase as the inlet temperature decreases. The inducer can significantly reduce the critical cavitation number of the pump. Finally, an empirical correlation considering the thermodynamic effects is proposed to predict the increase in the critical cavitation number.

Operational characteristics and performance optimizations of the organic Rankine cycle under different heat source/condensing environment conditions

The fluctuating heat sources and seasonal condensing environments are critical to the operation of Organic Rankine Cycle (ORC) under off-design conditions. This paper presents a comprehensive steady-state mathematical model developed using a newly built experimental platform. Focusing on the operational characteristics, including the evaporation pressure, condensation temperature, mass flow rate, and the performance of key equipment during the regulation of the expander, working fluid pump, and cooling water pump. Results show that the net efficiency initially increases before decreases, with both evaporation pressure and mass flow rate rising alongside the working fluid pump frequency. The quasi-two-stage single screw expander achieves an isentropic efficiency above 65 %. Additionally, flexible adjustments to the cooling water pump effectively regulate the cooling system, with timely cleaning of cooling pipelines enhancing net efficiency by up to 3.27 %. Optimization using the particle swarm algorithm improves system performance, achieving net efficiency enhancements of 1.8 % and 12.3 % under specific conditions. The novelty of this study lies in directly regulation of the expander, working fluid pump, and cooling water pump, significantly enhancing the off-design performance. This research provides valuable insights for researchers and designers, enabling flexible regulation of ORC operations to ensure efficient performance under varying conditions.

Experimental investigation on the performance of a Solar-Ocean Thermal Energy Conversion system based on the Organic Rankine Cycle

To improve the performance of the Ocean Thermal Energy Conversion (OTEC) system based on the Organic Rankine Cycle (ORC), a solar-assisted cycle is added, and the power generation experimental setup for the Solar-Ocean Thermal Energy Conversion (S-OTEC) system has been constructed. Through energy and exergy analysis, the effects of solar hot water temperature and working fluid flow rate on the components and system performance are investigated, and the performance differences between S-OTEC and OTEC at the same seawater temperature and working fluid flow rate are compared. The results show that: in the S-OTEC system, as the solar hot water temperature is increased from 54 °C to 72 °C, the isentropic efficiency of the working fluid pump and expander is improved, but the heat transfer coefficient of the heat exchanger is decreased. Futhermore, the thermal efficiency, power generation efficiency, and exergy efficiency increase in the ranges of 2.02–3.26 %, 2.93–3.15 %, and 37.93–41.01 %, respectively. When the working fluid flow rate is increased from 124.33 kg/h to 216.73 kg/h, the isentropic efficiency of the working fluid pump and expander as well as the heat transfer coefficient of the heat exchanger are improved. Additional, the thermal efficiency, power generation efficiency and exergy efficiency increase in the ranges of 2.05–2.75 %, 2.46–2.97 % and 38.01–48.13 %, respectively. What's more, the thermal efficiency, power generation efficiency and exergy efficiency of the S-OTEC system can be increased by 154.32 %, 39.33 % and 27.87 % respectively compared to the OTEC system.

Thermo-economic comparative analysis of a simple and cascaded organic Rankine power plants fired by rice husks

The application of organic working fluids in the Organic Rankine Cycle (ORC) has been demonstrated to be an attractive option for shifted integrated power and heat production. The procedure allows for the implementation of low-temperature heat sources, which provides advantages in small-scale uses. This study models the organic Rankine cycle for use with rice husk waste from a typical agricultural farm. The comparative analysis of agro-fired simple and cascaded organic Rankine power plants. Toluene and R245fa were considered as the working fluids for both simple and cascaded ORCs. Basic thermodynamic and economic governing equations were utilized in the analyses and embedded in the Engineering Equation Solver. The net powers, energy, exergy, and economic analyses of the two ORCs form the basis for comparison. Afterward, sensitivity analysis was carried out to ascertain the effects of variability of pertinent parameters on the plants. Results revealed that the net power output, thermal and exergy efficiencies of the simple and cascade ORC plants were 1.154 MW, 15.53% and 20.38%, and 1.599 MW, 21.51%, and 28.23%, respectively. The largest exergy destruction rate was obtained in the combustion chamber (1531 kW), and the least exergy destruction was recorded in the recirculation working fluid pump (1.073 kW). The simple ORC showed better economic performance as reflected in the unit cost of energy of 35.11 N/kWh as against 37.68 N/kWh of the cascaded ORC. The proposed energy system has the potential for a viable business enterprise based on the favorable Federal Government of Nigeria's fiscal and energy policies.

Synergetic mechanism of organic Rankine flash cycle with ejector for geothermal power generation enhancement

With the decrease of installed capacity, the problem of high working fluid pump power and low system efficiency is serious in organic Rankine cycle (ORC), and meanwhile, the matching between heat source and system also deteriorates. In this study, an organic Rankine flash cycle with ejector (EORFC) is proposed to eliminate the pump at the condenser outlet, thereby improving the above problem. A parametric study of the effects of the evaporating temperature, flashing temperature, evaporator outlet dryness and entrainment ratio on the thermodynamic and techno-economic performance of the organic Rankine flash cycle (ORFC) and EORFC are investigated. A comparative analysis for the two systems is further carried out, and meanwhile, R601, R601a, R245ca and R123 are comparably examined. The results show that when the net power output is the optimal, the net power output, thermal efficiency and exergy efficiency of the EORFC are averagely 3.26%, 6.96% and 1.96% higher than that of ORFC. The heat exchanger is the main component that increase the investment cost and exergy destruction, and the introduction of ejector can effectively improve them. Considering the two systems at the same operating conditions, the EORFC always has better thermal efficiency and levelized energy cost, while has higher net power output and exergy efficiency at high entrainment ratio and low pump isentropic efficiency. The multi-objective optimization indicates that the EORFC has better performance on the exergy efficiency and levelized energy cost, and R601 is suggested as the working fluid for the EORFC and ORFC.

Operation Control and Performance Analysis of an Ocean Thermal Energy Conversion System Based on the Organic Rankine Cycle

The development and utilization of marine renewable energy is an important measure for achieving energy conservation, emissions reduction and carbon neutrality. Ocean thermal energy is the most stable energy among all the types of marine renewable energy. This paper built a simulation model of an ocean thermal energy conversion system based on actual device specifications by Aspen and MATLAB and put forward a corresponding control strategy. The opening control signal of the control valve at the turbine inlet was the condenser inlet pressure in this paper, and the frequency control of the working fluid pump depended on the evaporating pressure and flow rate of the working fluid. This paper analyzed the key operating parameter changes of the system under different working conditions. According to the analysis results, the turbogenerator in this system was able to generate 50 kW power for about 8 months per year. The highest net output power of the Organic Rankine Cycle was 47.3 kW; the highest cycle thermal efficiency was 3.2%.

Influence of thermal stability on organic Rankine cycle systems using siloxanes as working fluids

• An off-design model with fluid decomposition parameters was established. • The influence of MM thermal decomposition on the ORC system was evaluated. • MM decomposition reduced the net power and efficiency of ORC system obviously. • MM decomposition may lead to incomplete evaporation and evaporator acid corrosion. The organic Rankine cycle (ORC) is an efficient power generation technology that has been widely used in renewable energy utilization and industrial waste heat recovery. The thermal stability of working fluids has a significant effect on the fluid selection and system design of ORC systems. In this study, an off-design model of an ORC system was established with hexamethyldisiloxane (MM) as the working fluid, and the effects of the MM thermal stability on the system were analyzed. The results showed that the effect of MM thermal decomposition on the cold source and working fluid pump was limited. The outlet temperature of the evaporator decreased with MM decomposition, which might lead to incomplete evaporation of working fluids and possible damage to the expander. The outlet temperature of the heat source also decreased with MM decomposition, which led to lower outlet temperatures than the acid dew point limit temperature. Both of these results can affect the safe operation of ORC systems. The net power and thermal efficiency of the system decreased with increasing thermal decomposition ratios of MM. The net power and thermal efficiency decreased by 7.48% and 10.72% respectively in the model of this study with a 10% decomposition ratio.

Performance analysis of ORC low temperature waste heat power generation system

For 90~180°C low temperature waste heat resources, three different types of organic working fluids, benzene, isopentane and R245fa are selected from the perspectives of safety, environmental protection and physical properties of working fluid. The mathematical models of the system are established through MATLAB and REFPROP and the influence of the evaporation temperature on the performance of the ORC low temperature waste heat power generation system is studied. The results show that the thermal efficiency and net output power of the system increase with the increase of evaporation temperature; the evaporation pressure of CFC-type working fluids is relatively low; the net output power and thermal efficiency of HFC and HC-type working fluids are generally relatively low. The evaporator has the largest irreversible loss in the system, followed by the condenser and expander while the working fluid pump has the smallest irreversible loss.

Identifying the key system parameters of the organic Rankine cycle using the principal component analysis based on an experimental database

The organic Rankine cycle (ORC) is a promising technology for medium-and-low temperature heat utilization. However, the mechanism of how system parameters affect output have been investigated very little in the experimental aspect. Experimental investigation on the impact of each system parameter on system performance requires decoupling these system parameters. In this work, a series of experiments are conducted on a 10 kW scale ORC experiment setup. Statistical analysis is performed to identify a key parameter subset based on an experimental database. 6 system parameters, including temperature (Te) and pressure (pe) at the evaporator outlet, temperature (Tc) and pressure (pc) at the condenser inlet, expander shaft efficiency (ηSSE), and working fluid pump efficiency (ηP) are obtained. Combined with the ORC net power output and thermal efficiency, an experimental database of system operation conditions is constructed. Subsequently, the principal component analysis (PCA) of ORC is conducted based on the experimental database. Prediction models are developed using multi-linear regression (MLR), back propagation artificial neural network (BP-ANN), and support vector regression (SVR). Finally, accounting for the prediction performance of models and system parameter inter-correlation behavior, the key parameter subset is determined with the exhaustive feature selection method. The results imply that the key parameter subset is (pe, ηP, pc, ηSSE). Further removing or including more system parameters would reduce the accuracy of prediction models. In addition, the MLR models are slightly less accurate than the more sophisticated BP-ANN and SVR models.

Introducing machine learning and hybrid algorithm for prediction and optimization of multistage centrifugal pump in an ORC system

The isentropic efficiency of the working fluid pump has a significant impact on the overall performance of the organic Rankine cycle (ORC) system. Based on machine learning, this paper proposes an experimental data-driven isentropic efficiency prediction model. Meanwhile, S-fold cross validation algorithm and smoothing factor circulation screening technology are used to improve the predictive ability of the model. The prediction accuracy of the optimized model and the unoptimized model are compared with each other. The influence of several operating parameters on isentropic efficiency are analyzed. In addition, with intelligent algorithm, the boundary values of operating parameters are determined. The genetic algorithm (GA) and particle swarm optimization (PSO) are combined into a GA-PSO hybrid algorithm. Subsequently, the hybrid algorithm is integrated with the machine learning model to predict and optimize the isentropic efficiency under full operating conditions. The highest isentropic efficiency reaches up to 58.73%. The prediction and optimization of the isentropic efficiency of multistage centrifugal pump under full operating conditions provides not only a useful guidance on assuming pump efficiencies in theoretical analysis, but also a meaningful reference for obtaining the optimum overall operating performance of the ORC system.

Effect of working fluids on the performance of phase change material storage based direct vapor generation solar organic Rankine cycle system

Working fluids can play a critical role in the working of an organic Rankine cycle system. A direct vapor generation solar organic Rankine cycle embedded with phase change material storage is analyzed in this study. The system comprised of an array of evacuated flat plate collectors, phase change material based thermal storage, expander, condenser, and organic working fluid pump. The storage tank model is modeled using a finite difference method in MATLAB programming environment while the 1D model of ORC system is used to evaluate the system performance. After a careful screen, 12 dry and isentropic working fluids were selected and their impact on the performance of the heat storage tank and the overall system is evaluated. The results show that the system efficiencies increase and decrease with the increment and decrement in the critical temperature of the working fluid. Moreover, the rise and fall of working fluid temperature, phase change material temperature, and the quantity of energy stored and released generally increase with an increase in the critical temperature of the working fluid. At the evaporation temperature of 10 °C higher and lower than the melting point temperature of the phase change material, Benzene has achieved the highest system efficiencies of 10.7% & 10.4% during charging and discharging mode, respectively. However, the maximum the rise and fall of working fluid temperature, phase change material temperature, and the quantity of energy stored and released during charging and discharging mode is attained by Heptane which is found to be 5.35 °C & 7.34 °C, 0.48 °C & 0.44 °C and 13.81 MJ & 23.04 MJ, respectively. Heptane has shown overall best performance among the selected working fluids and found to be feasible for phase change material storage based direct vapor generation solar ORC system.

Investigation on improvement potential of ORC system off-design performance by expander speed regulation based on theoretical and experimental exergy-energy analyses

In this paper, the potential of expander speed regulation for optimization of ORC system adaptability to off-design working conditions has been explored through experiments. According to the obtained results, it has been found that there existed two different optimal speeds: optimal power speed (rop), optimal efficiency speed (roee/rote) which could endow the ORC system with maximum output power or highest thermoelectric/exergy efficiency. For working conditions of tw = 70, 73, 80 °C, power of expander at rop has been increased by 199.1%, 137.4%, 6.5% compared with the power output at design speed (rds). The thermoelectric efficiency at rote was 11.1%, 27.7% higher than that at rop and rds. To further investigate the influences of expander speed on the performance, energy and exergy analyses were conducted based on theoretical calculation and experiment results within the range of 400–1600 r/min. The results showed that actual exergy destruction of expander and working fluid pump was closely related to expander speed. Gaps between theoretical and actual exergy destruction rates proved that optimization of expander and working fluid pump would be more effective for the ORC system performance.

Domestic Organic Rankine Cycle-Based Cogeneration Systems as a Way to Reduce Dust Emissions in Municipal Heating

Environmental issues are nowadays of great importance. In particular air and water quality should be kept at as high levels as possible. Energy conversion systems and devices which are applied for converting the chemical energy contained in different fuels into heat, electricity and cold in the industry and housing are sources of different gases and solid particle emissions. Medical data show PM2.5 dust in particular is highly dangerous for human health. Therefore, limiting the number of low-quality fuel combustion processes is a key issue of modern energy policy. Statistical data show that domestic heating systems account for a large share of the total emissions of PM2.5 and PM10 dust. For example in Poland in 2017, the share of households in the total annual emissions of PM2.5 dust was equal to ca. 35.8%, while the share of PM2.5 emission in industry (i.e., power generating plants, industrial power plants and technologies) was equal to only 23.6%. A possible way of solving this problem is by the successful replacement of old domestic furnaces by combined heat and power (CHP) or multigeneration boilers which can be used for heating the rooms and sanitary water and generating electricity and cold. Such systems can possibly contribute in the future to significant reductions of dust emissions and air pollution in urban and rural areas by limiting the number of low-quality fuel combustion processes. This article presents design considerations and experimental results related to a domestic micro-CHP unit which is based on organic Rankine cycle (ORC) technology. The main aim of the design works and experiments was therefore the analysis of the possibility of integrating the ORC system with a standard domestic central heating gas-fired boiler. The specially designed micro-ORC system was implemented in the laboratory and experiments were performed using this test stand. The main design aims of the test-stand were: low operating pressure, small working fluid flow, low price and compact dimensions. To meet these aims, volumetric machines were chosen as the expander and working fluid pump. The experimental results were positive and show that it is possible to integrate an ORC system with a standard domestic central heating gas boiler. For different heat source temperatures, the obtained expander power ranged from 109 W to 241 W and the thermodynamic cycle efficiency ranged from 4.3% to 8.8%. These positive research results were achieved partly thanks to the positive features of the different system subassemblies.

Real-time realization of Dynamic Programming using machine learning methods for IC engine waste heat recovery system power optimization

This study aims to present a method for real-time realization of Dynamic Programming algorithm for power optimization in an organic Rankine Cycle waste heat recovery system. Different from existing studies, for the first time machine learning algorithms are utilized to extract the rules from offline Dynamic Programming results for optimal power generation. In addition, for the first time a single state Proper Orthogonal Decomposition and Galerkin Projection based reduced order model is combined with Dynamic Programming for its high accuracy and low computation cost. For a transient driving cycle, Dynamic Programming algorithm is utilized to generate the optimal working fluid pump speed. A total of eleven state-of-art machine learning algorithms are screened to predict this pump speed. Random Forest algorithm is then selected for its best pump speed prediction accuracy. A rule-based method is added to the Random Forest model to improve energy recovery. As one of the main discoveries in this study, in the rule extraction process, the Random Forest model reveals that the time delayed exhaust gas mass flow rate and exhaust temperature improve the rule extraction accuracy. This observation points out the difference between steady state and transient optimization and that the steady state optimization results do not necessarily hold true in transient conditions. Another key observation is that Random Forest – rule-based method retrieves 97.2% of the energy recovered by offline Dynamic Programming in a validation driving cycle. In addition, the inclusion of rule-based method significantly increases the Random Forest model’s energy recovery from 66.5% to 97.2%. This high accuracy means that the machine learning models can be used to extract Dynamic Programming rules for real-time application.

Performance Analysis of a Multistage Centrifugal Pump Used in an Organic Rankine Cycle (ORC) System under Various Condensation Conditions

In an organic Rankine cycle (ORC) system, the working fluid pump plays an important role in the system performance. This paper focused on the operating characteristics of a multistage centrifugal pump at various speeds and condensation conditions. The experimental investigation was carried out to assess the influence of the performance of the pump by the ORC system with special attention to actual net power output, thermal efficiency as well as back work ratio (BWR). The results showed that an increase in the pump speed led to an increase in the mass flow rate and expand in the operating range of the outlet pressure. The mass flow rate decreased nonlinearly with the increase of the outlet pressure from 0.22 to 2.41 MPa; the electric power consumption changed between 151.54 and 2409.34 W and the mechanical efficiency of the pump changed from 7.90% to 61.88% when the pump speed varied from 1160 to 2900 r/min. Furthermore, at lower pump specific speed the ORC system achieved higher thermal efficiency, which suggested that an ultra-low specific speed pump was a promising candidate for an ORC system. The results also suggested that the effects of condensation conditions on the pump performance decreased with the pump speed increasing and BWR was relatively sensitive to the condensation conditions, especially at low pump speed.

A flexible and multi-functional organic Rankine cycle system: Preliminary experimental study and advanced exergy analysis

In the present study, a novel and flexible experimental facility of an organic Rankine cycle system is constructed. Four extra heat exchangers than traditional test bench are equipped for the system performance testing with different evaporator and condenser or heat transfer examinations of the evaporator and condenser. The combination of an expansion valve and a cooler is designed to simulate the expander with desired type and expansion characteristic. Meanwhile, a scroll expander is installed in parallel. Preliminary investigations are motivated to explore the operating characteristics of the novel experimental facility under different conditions and to quantitatively discover the system improvement potentials for further optimizations. After the steady-state operation evaluation, the system is investigated by varying the heat source temperature and heat sink temperature as well as the working fluid pump stroke. The constant expander isentropic efficiency scenario is simulated through the combination of the expansion valve and cooler, and it is also validated by the installed expander. Results show that the power output of the system and electricity consumption of the working fluid pump are in the ranges of 2.42–3.55 kW and 0.44–0.49 kW, respectively, and the system thermal efficiency varies from 5.2% to 7.3%. Moreover, the system is then deeply explored by using exergy analyses to reveal the potential for performance improvement. The conventional exergy analysis tells that the evaporator has the largest exergy destruction. However, the advanced exergy analysis gives a more realistic improvement potential and suggests that the expansion process should be firstly improved.

Sensitivity analysis of operation parameters on the system performance of organic rankine cycle system using orthogonal experiment

In the present study, a 1 kW-scale experimental system which can be switched between BORC (basic organic Rankine cycle) and RORC (organic Rankine cycle with a regenerator) is employed. In order to analyze the influence of working parameters on the system performance quantitatively, the range analysis based on orthogonal design is adopted. The selected three system parameters are: the temperature at the inlet of the expander, temperature at the outlet of the condenser and the plunger travel of working fluid pump. For the system performance, six indices are selected, including the thermal efficiency, the back-work ratio, output power of the expander, pump work consumption, network and the mass flow of the working fluid. The optimal and worst level constitutions of factors for the six indices are concluded, the orders of the three factors' sensitivity to the six indices are also obtained. The results show that the temperature at the inlet of the expander is the dominant factor of the thermal efficiency, the back-work ratio, output power of the expander, and network. While the plunger travel of the working fluid pump is the dominant factor of pump work consumption and the mass flow of the working fluid.

Transient response of waste heat recovery system for hydrogen production and other renewable energy utilization

In this paper, a 1 kW ORC experimental system is built. Using R123 as the working fluid, transient responses of Basic ORC (BORC) and ORC with a regenerator (RORC) are both tested under critical conditions. A total of four experiments are carried out, including: (1) Case 1: the working fluid pump is suddenly shut down; (2) Case 2: the working fluid is overfilled or underfilled; (3) Case 3: the torque of the expander is suddenly loss. (4) Case 4: the cooling water pump is suddenly shut down. All the major quantities such as the output power and torque of the expander, temperatures and pressures at the inlet and outlet of the expander, temperatures at the inlet and outlet of the condenser are measured. The transient responses of the two systems under the controlled critical conditions are tested and compared, some physical explanations are provided. It is found that RORC is more stable than BORC because of the regenerator. Regenerator should act as a “pre-heater” or “pre-cooler” under the critical conditions thus improving the stability of RORC. When the working fluid in the system is underfilled or leaked, the system performance is extremely unstable. Otherwise, when the working fluid is overfilled, the trend of the curves are similar to the optimal working condition but with weaker performances. We also find that if the working fluid pump is shut down when working fluid is overfilled, the rotation speed and shaft power output of the expander will increase significantly, the unique phenomenon can be used to estimate whether the working fluid in the system is overfilled.

Design and dynamic investigation of low-grade power generation systems with CO2 transcritical power cycles and R245fa organic Rankine cycles

This paper deals with the dynamic experimental investigation on low-grade power generation systems with CO2 transcritical power cycles (T-CO2) and R245fa organic Rankine cycles (ORC). These two systems were heated indirectly by exhaust gases of an 80 kWe micro-turbine CHP unit through a hot thermal oil system. The main components of each test system included a plate-type gas generator/evaporator, a turboexpander with high speed generator, a finned-tube air cooled condenser and a liquid pump. Both test rigs were fully commissioned and instrumented from which comprehensive dynamic experimental investigations were conducted to examine the effects of some important dynamic operational processes on system performance. These included the system start-up, variation of working fluid pump speed, change of thermal oil pump speed and system shutdown. These can lead to fully understand the dynamic and inertia behaviours of the system operations and thus to obtain robust controls. The experimental results reveal that working fluid mass flow rates are affected significantly by the start-up and shutdown processes, followed by the temperatures and pressures at turbine inlets and outlets. The research outcomes can contribute significantly to understand the system dynamic operating processes and thus instruct the system controls and safety operations.

Experimental study and performance analysis of a hydraulic diaphragm metering pump used in organic Rankine cycle system

In this paper, a performance test of a hydraulic diaphragm metering pump using R123 is conducted. The interaction relationships of key parameters of the pump and its influence on the performance of the ORC system are analyzed. The application feasibility of the pump has been proved by comparison to previous studies. The results indicate that the mass flow rate of the pump varies from 0.23 t/h to 2.06 t/h and is mostly independent of outlet pressure. Both power input and actual efficiency of the pump increase with stroke; the actual efficiency reaches up to a maximum of 88.27%. The specific speed decreases with the increase of outlet pressure. Moreover, the actual net power output and thermal efficiency of the ORC system increase with evaporating temperature. Actual net power output is more sensitive than thermal efficiency to stroke. The thermal efficiency presents a nonlinearly rapid decline trend with the increase of specific speed. Back work ratio (BWR) can reach up to a maximum of 0.93. Thus, the power input of working fluid pump is not negligible in the ORC system and the assumptions of actual efficiency of pump should be dependent on experimental results according to various operating conditions.