Heat Recovery Organic Rankine Cycle Research Articles

Design and Optimization of a Waste Heat Recovery Organic Rankine Cycle System with a Steam–Water Dual Heat Source

The organic Rankine cycle (ORC) system in plants, powered by dual steam–water heat sources, has significant power generation potential and practical research value. Herein, the conditions of 700 kPa saturated steam and 650 kPa, 90 °C water heat source are considered. Four configurations of steam–water dual heat source waste heat recovery ORC systems are proposed. The independent parameters affecting the net output power of the system are obtained by developing a mathematical model and optimizing it using the particle swarm optimization method. The results show that the location of the pinch‐point temperature difference in various ORC loops and the allowable working pressure of the heat exchanger are determinants of independent parameters. The net output powers of the conventional dual‐loop ORC (CD‐ORC), single‐loop ORC (S‐ORC), split‐flow dual‐loop ORC (SFD‐ORC), and split‐flow triple‐loop ORC SFT‐ORC systems under the optimal design parameters are 2415.73, 2168.6, 2599.62, and 2716.75 kW, respectively. In addition, S‐ORC has the highest exergy efficiency of 55.17%. SFD‐ORC and SFT‐ORC have ≈48% exergy efficiency, and CD‐ORC has the lowest exergy efficiency of 45.33%.

Thermoeconomic analysis of conventional and recuperative ORC for heat recovery of exothermic reactions

The possibility of using medium temperature (478–506 K) saturated steam from a reactor cooling system as heat source for generating electricity is evaluated in this work. Both usual Organic Rankine Cycle (ORC) and recuperative (RORC) configurations were modeled for 3 different boiler heat loads (Cases 1, 2 and 3) so that the electricity generation capacity effect on the economic performance could be evaluated. From the power cycle simulations, methanol and ethanol had shown the best performance in the ORC configuration with average First and Second Laws’ efficiencies of 16% and 44%, respectively. By adding a recuperator, most of the dry fluids have also shown similar performances. In the economic analysis, net power generation plays a major role. For Case 2 ( ≈ 250 kW net) and Case 3 ( ≈ 850 kW net), the power generation revenue was insufficient to cover the operational expenses, yielding unfeasible scenarios. However, for Case 1 ( ≈ 2.5 MW net), economic feasibility was achieved even for low operating pressures. The best power cycle thermoeconomic performance was found for methanol as working fluid. In the best scenario, an attractive internal rate of return of 14.5% was achieved for an specified electricity cost of US$ 0.0671 per kW h. • Heat from medium temperature latent heat source is recovered to power an ORC. • Optimal evaporation temperature for dry fluids in RORC configuration is defined. • Minimum temperature difference automatic adjustment during power cycle simulation. • Heat exchanger detailed design based on literature correlations. • Power cycle NPV and pay-back calculation.

Experimental investigation of combustion engine with novel jacket and flue gas heat recovery

Internal combustion engines (ICE) are utilized in a number of energy and transportation systems and with the prospect of synthetic green fuels have also secured a place in the future low emission systems. Still, aiming at the effective utilization of the fuel suggests an addition of waste heat recovery systems such as organic Rankine cycle (ORC) to boost electric efficiency. Greater widespread of the ORC integration into the ICE systems is however limited from multiple aspects. Furthermore, when these systems are employed, they are typically applied only for flue gas waste heat utilization, while the large amounts of lower temperature jacket cooling heat remain unutilized, or at the cost of high system complexity. Direct cooling of the ICE jacket by the ORC working fluid has been previously theoretically proposed to tackle some of them. Complexity of the system can be reduced while more waste heat can be effectively transferred from the ICE jacket cooling to the ORC. Here we propose further configuration of ICE waste heat sources integration into a biomass fired ORC unit, creating a multi-fuel system. Such system offers the possibility to increase the electricity demand while reducing biomass consumption. This system has been experimentally explored on a case of a 3 kWe/50 kWth micro-cogeneration ORC and an 8 kWeICE. The experimental data are evaluated in comparison to the theoretically predicted operation. A specific control system has been developed for this system to be easily operated. The results, experience and operation verification from the ICE jacket cooling with the ORC fluid can be also utilized in the construction for waste heat recovery ORC integrated to ICE for higher electrical efficiency. Integration of combined direct jacket and flue gas heat recovery increased the overall electrical efficiency of the system from about 5% for operation of standalone ORC to over 20% for full ICE power.

Energy, Exergy, Exergoeconomic and Emergy-Based Exergoeconomic (Emergoeconomic) Analyses of a Biomass Combustion Waste Heat Recovery Organic Rankine Cycle.

In recent decades, there has been an increasing trend toward the technical development of efficient energy system assessment tools owing to the growing energy demand and subsequent greenhouse gas emissions. Accordingly, in this paper, a comprehensive emergy-based exergoeconomic (emergoeconomic) method has been developed to study the biomass combustion waste heat recovery organic Rankine cycle (BCWHR-ORC), taking into account thermodynamics, economics, and sustainability aspects. To this end, the system was formulated in Engineering Equation Solver (EES) software, and then the exergy, exergoeconomic, and emergoeconomic analyses were conducted accordingly. The exergy analysis results revealed that the evaporator unit with 55.05 kilowatts and the turbine with 89.57% had the highest exergy destruction rate and exergy efficiency, respectively. Based on the exergoeconomic analysis, the cost per exergy unit , and the cost rate of the output power of the system were calculated to be 24.13 USD/GJ and 14.19 USD/h, respectively. Next, by applying the emergoeconomic approach, the monetary emergy content of the system components and the flows were calculated to evaluate the system’s sustainability. Accordingly, the turbine was found to have the highest monetary emergy rate of capital investment, equal to , and an output power monetary emergy of . Finally, a sensitivity analysis was performed to investigate the system’s overall performance characteristics from an exergoeconomic perspective, regarding the changes in the transformation coefficients (specific monetary emergy).

Experimental and numerical analysis on low-temperature off-design organic Rankine cycle in perspective of mass conservation

Experimental and numerical studies on the low-temperature heat recovery organic Rankine cycle operating in off-design conditions are conducted for the in-depth understanding of the system's underlying mechanisms in terms of mass conservation. Experimental data sets were obtained from a 1 kW lab-scale organic Rankine cycle test bed using R245fa as the working fluid. The effects of several boundary conditions, including charged mass, are thoroughly examined under low-temperature heat source within the range of 65–95 °C. Numerical models of the heat exchangers are developed by applying the discretization method to predict the captured mass inside the phase-changing components and validated within 5% error range. By the integration of experimental and numerical methods, unprecedented and critical results covering the pressure formation process, mass distribution, and liquid receiver modeling are derived from the analysis which could not be discovered through previous approaches. The unconventional thermodynamic state of the working fluid inside the liquid receiver is revealed in detail and a passive design is suggested for the liquid receiver model. An improved solver architecture is proposed for the complete development of a fully deterministic off-design organic Rankine cycle simulation model, where the reality-based logics obtained from the key findings are projected into the novel model.

Experimental validation of a multiple model predictive control for waste heat recovery organic Rankine cycle systems

Waste heat recovery systems are today considered as a valuable solution to increase energy efficiency of industrial applications and heavy-duty vehicles, as it uses a thermodynamic organic Rankine cycle system to recover the heat losses to produce electrical or mechanical power. Optimal performance of such machines is often achieved at conditions where complex time-varying nonlinear dynamics are encountered, making the automatic control strategy a fundamental element to maximise the energy efficiency. In this paper the development of a multiple model predictive controller suitable for industrial implementation is presented, and its effectiveness is experimentally validated for the task of maximising output power of a 11kWel small-scale ORC power unit used in a waste heat recovery application. The main advantage of the proposed controller is the possibility to use different model structures to describe local dynamics without increasing complexity of the optimisation problem. Additionally, experimental results illustrate that the entire operating range of the system might be classified in two regions, a quasi-linear and a highly nonlinear region for ‘high’ and ‘low’ superheating degrees respectively. Closed-loops tests lead to the conclusion that a single linear model predictive controller might only be used under suboptimal operation of low power production (on the quasi-linear region for ‘high’ superheating), otherwise leading to poor performance or even instability. Alternatively, the proposed strategy keeps the cycle stable over the entire range of conditions and allows to increase the net electrical energy produced by at least 6%, even under drastic waste heat source variations, when operating closer to the minimum allowed superheating degree.

Optimized Working Fluid for Waste Heat Recovery Organic Rankine Cycle

Optimized Working Fluid for Waste Heat Recovery Organic Rankine Cycle

Investigation of an integrated powering system for clean locomotives with solid-oxide fuel cell with heat recovery organic Rankine cycle

In this paper, a novel integrated solid-oxide fuel cell-based powering system with heat recovery for operating an ammonia organic Rankine cycle is introduced and analyzed thermodynamically. The application of this system is intended for clean locomotives. A thermodynamic model that is based on energy and exergy analyses is presented for this integrated system. The results of the analysis show a significant increase in the power output of the organic Rankine cycle that can reach a value of 239.2 kW which is up from 87.74 kW for a system without fuel cell heat recovery. Furthermore, the overall energy and exergy efficiencies have improved up to values of 74.22% and 71.95%, respectively. The parametric studies are performed to focus on investigating parameters of heat recovery and their effects on the overall performance of the integrated system as well as electric power production.

Two-Stage Radial Turbine for a Small Waste Heat Recovery Organic Rankine Cycle (ORC) Plant

Looking at the waste heat potential made available by industry, it can be noted that there are many sectors where small scale (< 100 kWe) organic Rankine cycle (ORC) plants could be applied to improve the energy efficiency. Such plants are quite challenging from the techno-economic point of view: the temperature of the primary heat source poses a low cutoff to the system thermodynamic efficiency. Therefore, high-performance components are needed, but, at the same time, they have to be at low cost as possible to assure a reasonable payback time. In this paper, the design of a two-stage radial in-flow turbine for small ORC industrial plants is presented. Compared to commonly applied mono-stage expanders (both volumetric and dynamic), this novel turbine enables plants to exploit higher pressure ratios than conventional plants. Thus, the theoretical limit to the cycle efficiency is enhanced with undoubted benefits on the overall ORC plant performance. The design process involved 1D/2D models as well as 3D Computational Fluid Dynamic ones. After the design of the preliminary configuration, sensitivity analyses were carried out varying the most relevant geometric parameters for design performance improvement. Thereafter, the stages were both analyzed in off-design conditions giving their performance maps. Moreover, a stage stacking procedure was applied to obtain the overall turbine behavior.

Full-admission radial turbine for waste heat recovery organic Rankine cycles

Organic Rankine Cycle (ORC) plants are interesting systems for power production by Waste Heat Recovery (WHR), although their application, especially for small/medium plants, could be not economically convenient. This is due to the inherent low thermodynamic cycle efficiency connected to the temperature of the heat source. Therefore, to avoid further penalizations, plant components (especially the turbine) should reach high performance both at nominal and off-design conditions. The paper deals with the design (from a 1-D to a fully 3-D level) of a full-admission radial-inflow turbine for a WHR ORC plant with a power output less than 50 kW. A parametric study was carried out to improve the turbine performance varying the most relevant geometric parameters, and the most promising geometry was analyzed in off-design conditions.

Multiobjective Optimization of a Plate Heat Exchanger in a Waste Heat Recovery Organic Rankine Cycle System for Natural Gas Engines.

A multiobjective optimization of an organic Rankine cycle (ORC) evaporator, operating with toluene as the working fluid, is presented in this paper for waste heat recovery (WHR) from the exhaust gases of a 2 MW Jenbacher JMS 612 GS-N.L. gas internal combustion engine. Indirect evaporation between the exhaust gas and the organic fluid in the parallel plate heat exchanger (ITC2) implied irreversible heat transfer and high investment costs, which were considered as objective functions to be minimized. Energy and exergy balances were applied to the system components, in addition to the phenomenological equations in the ITC2, to calculate global energy indicators, such as the thermal efficiency of the configuration, the heat recovery efficiency, the overall energy conversion efficiency, the absolute increase of engine thermal efficiency, and the reduction of the break-specific fuel consumption of the system, of the system integrated with the gas engine. The results allowed calculation of the plate spacing, plate height, plate width, and chevron angle that minimized the investment cost and entropy generation of the equipment, reaching 22.04 m2 in the heat transfer area, 693.87 kW in the energy transfer by heat recovery from the exhaust gas, and 41.6% in the overall thermal efficiency of the ORC as a bottoming cycle for the engine. This type of result contributes to the inclusion of this technology in the industrial sector as a consequence of the improvement in thermal efficiency and economic viability.

Thermal and economic analysis on vehicle energy supplying system based on waste heat recovery organic Rankine cycle

A novel vehicle energy supply system is proposed through integrating a waste heat recovery organic Rankine cycle subsystem to the conventional vehicle air conditioning subsystem. Based on an actual vehicle engine operation data at different engine load, the overall thermal and economic performances of the proposed vehicle energy supply system are investigated through comparing with the conventional and the vehicle energy supply system with a standalone waste heat recovery organic Rankine cycle subsystem, considering the influences from the ambient temperature, the working fluid selection, the turbine inlet temperature under different seasons. The analysing results indicated that the proposed vehicle energy supply system hold prominent thermal and economic performance advantages compared to that of the conventional vehicle energy supply system with a standalone waste heat recovery organic Rankine cycle subsystem. With the change of season, the proposed system showed the best overall performance in winter, the spring/autumn is the next, the summer was the worst under the rated vehicle engine load. Both the maximal gasoline oil saving rate and the minimal static payback period are obtained at a certain organic Rankine cycle evaporating pressure. The maximal gasoline oil saving rate at 9.73 kg/h, and the minimal payback period at 769 h are achieved. Moreover, Cyclo-pentane is the best working fluid of the waste heat recovery subsystem for the integrated vehicle energy supply system scheme under the operating conditions in this research.

Thermal analysis on vehicle energy supplying system based on waste heat recovery ORC

Based on the engine waste heat recovery using organic Rankine cycle (ORC), a vehicle energy-supplying system was proposed to satisfy energy demand of vehicle in every season. Based on a typical vehicle engine, the vehicle energy-supplying system based on the waste heat recovery was analyzed. The simulation results showed that reducing the log mean temperature difference (LMTD) in the first evaporator, decreasing the environment temperature and enhancing the vehicle speed are three effective methods to increase the turbine power output and fuel saving rate. In winter, the maximal fuel saving rate is achieved to satisfy the heat and power requirements of the vehicles. In spring /autumn, it could save much fuel consumption, and the power demand of vehicle could be satisfied. In summer, the minimal fuel saving rate and thermal efficiency of the bottom ORC are achieved. The maximum value of turbine power output and fuel saving rate are 14.7 kW and 0.23 respectively under the operation conditions in this paper.

Effects of ORC Working Fluids on Combined Cycle Integrated with SOFC and ORC for Stationary Power Generation

The purpose of this study is to explore the effects of working fluid on conventional combined cycle integrated with pressurized solid oxide fuel cell (SOFC) and waste heat recovery organic Rankine cycle (ORC) for stationary utility power generation. The mathematical model of a natural gas fueled design configuration is developed in Matlab and Simulink and simulated with 14 working fluids. The effluent gases of SOFC undergo combustion in the combustion chamber and it is utilized in the gas turbine, steam turbine cycle and ORC. The model is compared with those found in literature and the parametric studies of temperature, flow rate, fuel utilization factor and exhaust gas on the system efficiency are examined. Results revealed that working fluids show a closely related behavior in efficiency at low pressure ratio and high flow fraction, fuel utilization, and temperature. R-123 was found to perform the best among 14 working fluids studied, yielding a system energy efficiency of 70% in the combined cycle integrated with SOFC and ORC.

Multi-objective optimization and exergetic analysis of a low-grade waste heat recovery ORC application on a Brazilian FPSO

This paper presents an analysis of the application of an Organic Rankine cycle (ORC) for power generation of a Brazilian FPSO (Floating Product Storage Offload). The peculiarity of this analysis is the investigation of power generation using low-temperature waste heat sources. Low-grade sources represent a significant amount of heat rejected on the platform. The primary production in the platform processes was evaluated using ASPEN-HYSYS® software v.8.6. The main sources of low-temperature residual heat were preliminarily identified, and the highest potential for energy recovery was: the heat rejected in the intercoolers and aftercoolers of the compression processes in the Main Compression Unit and the CO2 Compression Unit. For the development of this study, a computational tool was elaborated in MATLAB® to evaluate the thermodynamic performance and to predict the design of the heat exchanger of the ORC. A multi-objective optimization was conducted to verify the ORC application at the established sources. The higher net power was obtained at Main Compression Unit heat recovery, operating with R245CB2 as working fluid. This application allows to generate up to 2063 kW with a heat transfer area of 2997 m2, providing a 23.6% increase in exergy efficiency of the system. The results of this study suggest that the application of ORC cycles on FPSO platforms for heat recovery from low-temperature sources allows an essential increase in the energy and exergetic efficiency of the production processes of the platform. Although the ORC doesn’t give a substantial increase in the supply of electricity, they contribute to less gas consumption in gas turbines. In this way, contributing to a significant reduction of GHG emissions.

Thermodynamic and economic analysis of the integration of Organic Rankine Cycle and Multi-Effect Distillation in waste-heat recovery applications

The coupling of a small-scale Multi-Effect Distillation system for seawater desalination with a waste heat recovery Organic Rankine Cycle was studied. Two configurations were analysed: a hybrid serial-cascade and a cascade configuration. The heat source was a generic waste heat flow at 200 °C. Four sizes were considered for the Multi-Effect Distillation, from 500 to 2000 m3/day. The second law efficiency decreased with the desalination unit size for the hybrid configuration, while presented a maximum value in size range 500–2000 m3/day for the cascade configuration. For the serial-hybrid configuration, the second law efficiency decreased from 43.1% to 15.5% when passing from a Multi-Effect Distillation size of 500 to 2000 m3/day, while for the cascade, the values had a reduced variation between 26.2 and 21.4%. The economic analysis showed that the hybrid configuration reduced to a serial configuration, which was largely more profitable. Moreover, when the size of the Multi-Effect Distillation was smaller, the investment could be convenient also for a water price of 0.8 $/m3, and the profitability index in some configurations reached 2.4 with this water price. In most of the cases, the coupling with an Organic Rankine Cycle improved the investment and reduced the payback time.

Experimental Investigation and CFD Analysis of Heat Transfer in Single Phase Subcooler of a Small Scale Waste Heat Recovery ORC

In the present work, a detailed investigation of the single phase heat transfer mechanism in a novel subcooler of an experimental small scale waste heat recovery Organic Rankine Cycle (ORC) unit is presented. The ORC unit is operating with R134a and is designed to utilize the waste heat from the jacket water of marine diesel auxiliary internal combustion engines (ICEs). The ORC unit produces 3.7 kWel net electrical power at a cycle pressure of 25 bar and an expander inlet temperature of 82 °C. The application of subcooling in such systems is common practice, so as to ensure the cavitation-free operation of the pump.The subcooler is designed to achieve a certain level of subcooling and at the same time minimize the pressure losses on both the refrigerant and the cooling water side. A theoretical CFD model is developed to predict its operation. Based on the experimental results, a new heat transfer correlation is proposed for the single phase heat transfer inside a corrugated tube. The accuracy of the new correlation is compared with existing ones from the literature. Meanwhile, the results of the correlation are validated by the experimental data collected from the respective ORC unit, reducing the theoretical calculations maximum relative error from 2.98% to a 1.88%.

Parametric study for small scale engine coolant and exhaust heat recovery system using different Organic Rankine cycle layouts

This paper presents the study of four different engine coolant and exhaust heat recovery Organic Rankine Cycle systems using R245fa as working fluid and scroll expander as expansion machine. The parametric investigation suggested the fluid superheating temperature has limited influence on the simple structured ORC system (ORC_sim) with overall efficiency about 6.2% and average produced power around 0.59kW under engine rated condition. The maximum rotational speed of the scroll expander is around 4000rpm under different ratio of coolant and exhaust ratio of the Yanmar engine (6.8kW), which means the designed ORC system can be easily used for electricity generation by directly connecting expander shaft to a conventional electrical generator. The BSFC reduction ratios of ICE+ORC_sim, ICE+ORCR_1 and ICE+ORC_pre under engine rated power are respectively 6.1%, 7.4% and 5.2%. And the overall effective energy efficiency by integrating ORC_sim, ORCR_1 and ORC_pre to the ICE can be improved by 6.5%, 8.0% and 5.4% under engine rated power condition.

An experimental analysis of flow boiling and pressure drop in a brazed plate heat exchanger for organic Rankine cycle power systems

Organic Rankine cycle power systems for low quality waste heat recovery applications can play a major role in achieving targets of increasing industrial processes efficiency and thus reducing the emissions of greenhouse gases. Low capacity organic Rankine cycle systems are equipped with brazed plate heat exchangers which allows for efficient heat transfer with a compact design. Accurate heat transfer correlations characterizing these devices are required from the design phase to the development of model-based control strategies. In this paper, the experimental heat transfer coefficient and pressure drop during vaporization at typical temperatures for low quality waste heat recovery organic Rankine cycle systems are presented for the working fluids HFC-245fa and HFO-1233zd. The experiments were carried out at saturation temperatures of 100°C, 115°C and 130°C and inlet and outlet qualities ranging between 0.1–0.4 and 0.5–1 respectively. The experimental heat transfer coefficients and frictional pressure drop were compared with well-known correlations and new ones are developed. The results indicated weak sensitivity of the heat transfer coefficients to the saturation temperature and were characterized by similar values for the two fluids. The frictional pressure drop showed a linear dependence with mean quality and increased as the saturation temperature decreased.

Evaluation of a small-scale waste heat recovery organic Rankine cycle

In recent years, the use of small-scale organic Rankine cycles (ORC) in exhaust gas heat recovery of reciprocating engines has been intensively studied. In this paper, the working fluid selection and experimental results of a small-scale ORC unit utilizing exhaust heat of a diesel engine are presented and discussed. Based on the working fluid selection study, siloxane MDM was evaluated as the most suitable fluid for the experimental system. The experiments were conducted with the aim of studying and analyzing the capability of the ORC process of recovering heat from the diesel engine exhaust. The high pressure MDM vapor was expanded through an expansion valve; thus, no power was extracted from the experimental setup and the main focus was on studying the performance of the process heat exchangers. The system under study was identified to be capable of efficiently recovering the waste heat of the exhaust gases, and the potential of using high molecular weight and high critical temperature fluids as the working fluids in high-temperature, small-scale ORC applications was confirmed. It was concluded that when using siloxane MDM as the working fluid, the requirements for the process sealing to withstand low vacuum conditions as well as the effective removal of non-condensable gases during the operation can be identified as one of the major challenges in achieving the targeted power output from this type of ORC systems.