Trilateral Flash Cycle Research Articles

Comparison of different optimized heat driven power-cycle configurations of a gas engine

Among different technologies in internal combustion engines, waste heat recovery from the lost energies has great potential to improve fuel economy and reduce CO2 emission. In the present work, to achieve the optimal design parameters for a waste heat recovery system of a gas engine, a multi-objective optimization evolutionary algorithm is employed. The system consists of different types and combinations of the Organic Rankine/Kalina cycle as the waste heat recovery system of gas engine exhaust gas and the waste heat of cooling water is recovered by the trilateral flash cycle. The objective functions are chosen to maximize exergy efficiency and minimize the specific investment cost of the system. Cyclohexane, Toluene, and Benzene have been investigated and compared to the organic Rankine cycle working fluid. To evaluate different cycle configurations and working fluids, the Pareto front solutions related to 18 studied cases are compared. Meanwhile, the “Linear Programming Technique for Multidimensional Analysis of Preference” decision-making approach has been used as an optimal point in all cases. This work is aimed to compare the optimal design operating conditions of the studied configurations to choose the best configuration for waste heat recovery from a gas engine. The results reveal that, among the decision parameters, the organic Rankine cycle turbine inlet temperature is the most important in terms of the specific investment cost of the system. Also, considering the exergy and energy efficiency of the system, organic Rankine cycle turbine inlet temperature as well as organic Rankine cycle and trilateral flash cycle turbine isentropic efficiencies are of great importance. The Pareto front comparison for each configuration indicates that toluene is the most suitable fluid for the organic Rankine cycle in all configurations. Comparing the selected optimal points in different combinations reveals that, the configuration of organic Rankine cycle with internal heat exchanger-trilateral flash cycle, due to its lower payback period and specific investment cost as well as the higher exergy efficiency and net power output in optimal point, is the prominent compared to the other combinations. Furthermore, the optimized configuration of the organic Rankine cycle with the internal heat exchanger-trilateral flash cycle shows a 14.31% increase in the exergy efficiency and an 8.2% decrease in the specific investment cost of the system compared to the base case. Employing the optimized configuration of the organic Rankine cycle with internal heat exchanger-trilateral flash cycle as waste heat recovery of the gas engine leads to a 7.8 kW increment of net power output, equivalent to an increase of 18.85% exergy efficiency of the whole system including engine and bottoming cycle. On the other hand, additional equipment to the engine, impose 3061$/kW specific investment cost which takes 2.2 years to be paid back.

Modelling and off-design performance optimisation of a trilateral flash cycle system using two-phase twin-screw expanders with variable built-in volume ratio

This research work presents a numerical chamber model of a two-phase twin-screw expander and its further integration in a one-dimensional model of a Trilateral Flash Cycle (TFC) system for low-grade heat to power conversion applications. The novel feature of the expander is the capability of changing the built-in volume ratio (BIVR) of the machine through a sliding valve in the casing that opens an additional suction port. Lowering the BIVR from 5.06 to 2.63 results in an improvement of the volumetric efficiency from 53% to 77% but also in a reduction of the specific indicated power from 4.77 kJ/kg to 3.56 kJ/kg. Parametric analysis on several degrees of freedom of the full TFC system concluded that expander speed and BIVR are the variables that mostly impact the net power output of the unit. An optimisation study enabled the net power output of the TFC system, at design point, to increase from 81 kW to 103 kW.

Experimental study on the prospect of low-temperature heat to power generation using Trilateral Flash Cycle (TFC)

In this paper, a trilateral flash cycle (TFC) based system has been developed and studied to find out its prospect for utilizing more energy and enhancing the power generation capacity. To hold simplicity and minimize the cost of system construction, an impulse turbine and a converging-diverging (CD) stationary nozzle setup have been used as the expander. The experimental study introduced impulse turbine incorporates with a stationary CD nozzle and organic working fluid, which showed a promising power generation capability from a heat source below 80 °C in spite of the increasing size of the heat exchanger, condenser, and pump. In addition to the use of proper impulse turbines, however, the power generation capacity of such type of system is basically a function of the nozzle isentropic efficiency, which lies on the nozzle geometry and the alignment with respect to the turbine. A case study on the application of the TFC system for commercial power generation in associate with economic analysis has also been included in this study which shows a payback time less than 10 years with typical operational life of 20 years, considering only 40% nozzle isentropic efficiency and by using more efficient nozzle, the capital cost per unit power generation could be minimized.

Solutions for thermal energy exploitation from the exhaust of an industrial gas turbine using optimized bottoming cycles

The issues like depletion of fossil fuels and environmental concerns encourage policy makers to run different types of power plants, including gas-turbine power plants more efficiently. For this purpose, bottoming cycles can be employed to recover the low-grade thermal energy of the exhaust gases of the gas cycle. Kalina, organic Rankine, Goswami, and trilateral flash cycles were examined to be used as the second bottoming cycle of a gas-turbine power plant to scavenge low-grade thermal energy in the exhaust of an absorption refrigeration cycle as the first bottoming cycle. All alternatives to the secondary bottoming cycle were modeled and optimized by non-dominated sorting genetic algorithm II in MATLAB software considering energy and economic criteria. Then, the best alternative among optimized cycles was introduced. It was found that the best alternative is Goswami cycle, and the less desired one was Kalina cycle. Goswami cycle enabled to generate 4.26 MW of additional power as well as an additional 0.45 MW of an auxiliary cooling that reduces the required capacity of the chiller by 3.2%. The introduced foremost bottoming cycle increased the thermal efficiency of the power plant from 38.1 to 46.5%. The investments required for installation and usage of the best and worst bottoming cycle were determined to be paid back within 3.8 and 20.5 years, respectively. To have economic justification, the sold price of the best bottoming cycle (Goswami cycle) must be greater than 0.09 $.(kWh)−1 on average.

Исследование эффективности применения термогазлифта в треугольном цикле и в органическом цикле Ренкина = Baggley C. R., Read M. G. Investigation of a thermo-fluidic exchange pump in trilateral flash and organic Rankine cycles / пер. с англ. М. А. Федоровой

It is well known that large amounts of energy loss occurs at low temperature states in a wide range of industrial processes., The recovery and reuse of this energy is at the forefront of increasing the overall efficiencies of industrial systems. The aim of this paper is to investigate the effectiveness of using a Thermo-Fluidic Exchange (TFE) pump at low temperature conditions in both a SaturatedVapour Organic Rankine Cycle (SORC) and a Trilateral Flash Cycle (TFC). For some low temperature applications, TFCs have been shown to achieve higher net power output than conventional SORCs, due to their ability to extract more heat from the source fluid. This is the subject of current research as a result of advancements made in the design of positive displacement machines for operation as twophase expanders. Conventional turbines cannot be used for TFCs as they must operate in the vapour phase. One drawback of the TFC is the higher working fluid mass flow rate required. Depending on the scale of the system, this can potentially cause difficulties with pump selection. A TFE pump uses heat input to the system to increase the pressure and temperature of the working fluid, rather than the work input in a standard mechanical pump. This paper compares the net power output achievable using both mechanical and TFE pumps with SORC and TFC systems. The results suggest that the TFE pump could be a viable option for TFC systems

Influence of evaporating rate on two-phase expansion in the piston expander with cyclone separator

The trilateral flash cycle shows a greater potentiality in moderate to low grade heat utilization systems due to its potentiality of obtaining high exergy efficiency, compared to the conventional thermodynamic cycles such as the organic Rankine cycles and the Kalina cycle. The main difference between the trilateral flash cycle and the conventional thermodynamic cycles is that the superheated vapor expansion process is replaced by the two-phase expansion process. The two-phase expansion process actually consists of a flashing of the inlet stream into a vapor and a liquid phase. Most simulations assume an equilibrium model with an instantaneous flashing. Yet, the experiments of pool flashing indicate that there is a flash evaporating rate. The mechanism of this process still remains unclear. In this paper, the flash evaporating rate is introduced into the model of the two-phase expansion process in the reciprocating expander with a cyclone separator. As such, the obtained results reveal the influence of evaporating rate on the efficiency of the two-phase expander.

Comparison of the Trilateral Flash Cycle and Rankine Cycle with Organic Fluid Using the Pinch Point Temperature

Low-temperature heat utilization can be applied to waste heat from industrial processes or renewable energy sources such as geothermal and ocean energy. The most common low-temperature waste-heat recovery technology is the organic Rankine cycle (ORC). However, the phase change of ORC working fluid for the heat extraction process causes a pinch-point problem, and the heat recovery cannot be efficiently used. To improve heat extraction and power generation, this study explored the cycle characteristics of the trilateral flash cycle (TFC) in a low-temperature heat source. A pinch-point-based methodology was developed for studying the optimal design point and operating conditions and for optimizing working fluid evaporation temperature and mass flow rate. According to the simulation results, the TFC system can recover more waste heat than ORC under the same operating conditions. The net power output of the TFC was approximately 30% higher than ORC but at a cost of higher pump power consumption. Additionally, the TFC was superior to ORC with an extremely low-temperature heat source (<80 °C), and the ideal efficiency was approximately 3% at the highest work output condition. The TFC system is economically beneficial for waste-heat recovery for low-temperature heat sources.

Investigation of a Thermo-Fluidic Exchange Pump in Trilateral Flash and Organic Rankine Cycles

It is well known that large amounts of energy loss occurs at low temperature states in a wide range of industrial processes., The recovery and reuse of this energy is at the forefront of increasing the overall efficiencies of industrial systems. The aim of this paper is to investigate the effectiveness of using a Thermo-Fluidic Exchange (TFE) pump at low temperature conditions in both a Saturated-Vapour Organic Rankine Cycle (SORC) and a Trilateral Flash Cycle (TFC).For some low temperature applications, TFCs have been shown to achieve higher net power output than conventional SORCs, due to their ability to extract more heat from the source fluid. This is the subject of current research as a result of advancements made in the design of positive displacement machines for operation as two-phase expanders. Conventional turbines cannot be used for TFCs as they must operate in the vapour phase.One drawback of the TFC is the higher working fluid mass flow rate required. Depending on the scale of the system, this can potentially cause difficulties with pump selection. A TFE pump uses heat input to the system to increase the pressure and temperature of the working fluid, rather than the work input in a standard mechanical pump. This paper compares the net power output achievable using both mechanical and TFE pumps with SORC and TFC systems. The results suggest that the TFE pump could be a viable option for TFC systems.

Analysis of the thermodynamic disequilibrium loss of the two-phase expansion process and its influence on the performance of a reciprocating expander

The screw expander and the reciprocating expander were considered as the suitable technologies to be employed as two-phase expanders of the Trilateral Flash Cycle (TFC) systems. The two-phase expansion process in the screw expander could be approximately viewed as the thermodynamic equilibrium process due to the strong disturbing and mixing between the two-phase working fluids in the chamber volume. However, for the reciprocating expander, the situation was different. The flashed vapor in the reciprocating expander cylinder was separated from liquid in the flash chamber, which would result in a significant thermodynamic disequilibrium loss. To assess this loss, the thermodynamic equilibrium model (TEM) and the flash vaporization model (FVM) were simultaneously proposed in this paper. Water was used as the two-phase working fluid. The two-phase expansion processes, the isentropic efficiencies and the output expansion works of the two models were obtained. Predicted results were analyzed and compared under different rotation speeds and injection temperatures. The results showed that when rotation speed of the expander was increased from 50 r/min to 1000 r/min, the thermodynamic disequilibrium loss was approximately increased from 5.3% to 6.3%, and when injection temperature was decreased from 523.15 K to 473.15 K, the thermodynamic disequilibrium loss was approximately increased from 4.5% to 6.2%.

One-Dimensional Modelling of a Trilateral Flash Cycle System with Two-Phase Twin-Screw Expanders for Industrial Low-Grade Heat to Power Conversion

This paper provides an overview of a one-dimensional modelling methodology for equipment and systems for heat to power conversion based on a staggered grid space discretization and implemented in the commercial software GT-SUITE®. Particular attention is given to a newly developed modelling procedure for twin-screw machines that is based on a chamber modelling approach and considers leakage paths between cells and with the casing. This methodology is then applied to a low-grade heat to power conversion system based on a Trilateral Flash Cycle (TFC) equipped with two parallel two-phase twin-screw expanders and a control valve upstream of the machines to adapt the fluid quality for an optimal expander operation. The standalone expander model is used to generate performance maps of the machine, which serve as inputs for the TFC system model. Parametric analyses are eventually carried out to assess the impact of several operating parameters of the TFC unit on the recovered power and cycle thermal efficiency. The study shows that the most influencing factors on the TFC system’s performance are the inlet temperature of the heat source and the expander speed. While the first depends on the topping industrial process, the expander speed can be used to optimize and control the TFC system operation also in transient or off-design operating conditions.

Analysis of the intake process and its influence on the performance of a two-phase reciprocating expander

Two-phase expansion is of great interest to enhance the efficiency of conventional sub-critical organic Rankine cycle (ORC). However, the design of highly-efficient expanders to handle two-phase expansion is still an open topic in the literature. In this paper, an experimentally validated thermodynamic model was employed to investigate the two-phase expansion process in a reciprocating expander with a flash chamber for Trilateral Flash Cycle (TFC) applications. An intake ratio, ε, defined as the intake time to the expansion time has been proposed to analyze the suction process of saturated liquid and the corresponding intake losses. The evolutions of temperature, pressure, and quality during the expansion process have been simulated, and the intake losses have been quantified from the indicated diagrams. Moreover, parametric analyses on the influence of the intake ratio for different rotational speeds, mean inlet flow velocities, inlet port diameters, and intake mass values have been performed. The isentropic efficiency and the power output of the expander have been calculated and discussed under different operating conditions. Finally, a correlation for estimating the intake losses has been developed.

Investigation of the performance of modified organic Rankine cycles (ORCs) and modified trilateral flash cycles (TFCs) assisted by a solar pond

Solar pond is a type of solar collector that stores solar energy in the form of heat. The solar pond can be used as a low-temperature heat source for electricity generation. In this paper, to find the most suitable power cycle for power generation from the solar pond, the performance of the Organic Rankine Cycle (ORC), Trilateral Flash Cycle (TFC) and their modified forms with an open feed liquid heater and an internal heat exchanger for different working fluids was investigated. Water was considered as the heat transfer fluid which transfers the stored heat from the solar pond to the working fluid of the cycle. The results indicate that in all cases, the energy and exergy efficiency of the ORC is higher than those of the TFC. The regenerative ORC with both open feed liquid heater and internal heat exchanger that works with R123, as the working fluid, has the best performance and the highest output power among all the examined cycles. By reducing the mass flow rate of the heat removal working fluid, energy and exergy efficiency of the cycle increased. The optimum mass flow rate in which the maximum power is generated is 0.1082 kg/s and 0.1224 kg/s for the ORCs and the TFCs that work with R123, respectively.

Exergo-economic analysis of different power-cycle configurations driven by heat recovery of a gas engine

In the present work a 34.3 kW stationary gas engine considered as prime-mover of bottoming thermodynamic cycles. The waste heat recovery cycles of engine exhaust gas consist of several configurations of organic Rankine cycle and combination of Rankine/Kalina cycles, also the engine jacket water heat is recovered by trilateral flash cycle. The performance of bottoming cycles was investigated from thermodynamic and thermo-economic points of view. For the organic Rankine cycle, three fluids including Benzene, Toluene and Cyclohexane have been compared. Also, considering that the trilateral flash cycle is a suitable cycle for heat recovery from a low temperature heat source due to its better matching between the temperature profiles of cycle working fluid and heat source fluid, this cycle is considered as bottoming waste heat recovery cycle for engine jacket water. In order to compare different working fluids and cycle configurations, three objective functions including energy efficiency, exergy efficiency and specific investment cost for the 18 studied cases are compared. The results reveal that, energy, exergy efficiency and specific investment cost of all configurations with toluene as working fluid of organic Rankine cycle is the highest and least compared to the other working fluids, respectively. But for configuration Rankine with Open Feed Heater-Kalina-Trilateral Flash Cycle, benzene fluid is better in terms of specific investment cost, however the energy and exergy efficiency of this cycle is also maximal with toluene fluid. Also, the results depict that configurations Rankine with Internal Heat exchanger – Trilateral Flash Cycle and Rankine with Open Feed Heater_Kalina_Trilateral Flash Cycle thermodynamically, and configurations Rankine with Internal Heat exchanger – Trilateral Flash Cycle and Rankine with Open Feed Heater – Trilateral Flash Cycle exergo-economically show the better performance. In this regard, employing configurations Rankine with Internal Heat exchanger – Trilateral Flash Cycle, Rankine with Open Feed Heater-Kalina – Trilateral Flash Cycle and Rankine with Open Feed Heater – Trilateral Flash Cycle in base mode leads to 6.85 kW, 6.48 kW and 6.54 kW increment in net power produced imposing 3318 $/kW, 4090 $/kW and 3377 $/kW specific investment cost, respectively.

Numerical investigations of a Trilateral Flash Cycle under system off-design operating conditions

The current research presents a comprehensive model of a 100 kWe Trilateral Flash Cycle TFC system composed of sub-modules for the plate heat exchangers and twin-screw expanders to assess and identify the operating parameters that mostly affect the TFC performance at off-design conditions. The modelling approach for heat exchangers and piping is based on 1D CFD while considering the operating maps for pump and expander. The simulation process takes into account variations of the heat source temperature and mass flow rate from the design point. The TFC performance is analysed in terms of efficiency and power output while the expander performance is discussed in terms of volumetric and isentropic efficiencies. A sensitivity analysis is carried out to assess the most suitable parameter for control purposes and system performance optimisation. The results point out a large sensitivity of the inlet quality at the expander due to the revolution speed of the machine but also the off-design behaviour of the heater.

Waste Heat Recovery in the EU industry and proposed new technologies

In the European Union (EU), industrial sectors use 26% of the primary energy consumption and are characterized by large amounts of energy losses in the form of waste heat at different temperature levels. Their recovery is a challenge but also an opportunity for science and business. In this study, after a brief description of the conventional Waste Heat Recovery (WHR) approaches, the novel technologies under development within the I-ThERM Horizon 2020 project are presented and assessed from an energy and market perspectives. These technologies are: heat to power conversion systems based on bottoming thermodynamic cycles (Trilateral Flash Cycle for low grade waste heat and Joule-Brayton cycle working with supercritical carbon dioxide for high temperature waste heat sources); heat recovery devices based on heat pipes (flat heat pipe for high grade radiative heat sources and condensing economizer for acidic effluents).

Trilateral Flash Cycle (TFC): a promising thermodynamic cycle for low grade heat to power generation

Energy crisis, fossil fuel depletion and growing environmental concern pushing not only for new source of energy but also developing advance technology for power generation. Besides conventional heat sources, low grade heat source of below 100 °C temperature like solar thermal, geothermal or waste heat has a good potential to become a sustainable source of power. Organic Rankine Cycle is the widely use thermodynamic power cycle for low grade heat to power generation where low boiling point pressurised organic working fluid is vaporised and expands through a turbine fed generator thus outputting usable electrical energy. The used fluid then returns to a reservoir before it is condensed and forced through the same process again via a high-pressure pump. Another thermodynamic cycle namely Trilateral Flash Cycle (TFC) which is nothing but a modified ORC where the organic working fluid is heated up to the saturation temperature under high pressure rather than evaporated. In this paper, an analytical comparative study on ORC and TFC shows that TFC has about at least 50% more power generation potential than that of conventional ORC for the same heat source and heat sink conditions if the heat source temperature is just below 100 °C. TFC even has the potential of power generation from the heat source below 80 °C where ORC is not economically viable.

A parametric analysis to evaluate the performance metrics of power generation system involving Trilateral Flash Cycle using three different working fluids for low grade waste heat

With the accelerated growth in population and technology progress in day-to-day life, the traditional fuels demands have increased significantly. Despite the execution of many renewable sources (solar, wind, geothermal, biomass), the modern issues such as high investment and power costs have slowed down their development. In this context, improvisation of the existing power generation ways is required by evolving a highly effective thermal system to extract renewable energy available for low grade waste heat. At present, many of the applicable practices are engrossed on high temperature heat extraction rather than low-grade heat in spite of being expensive. In this work, innovative technology has been recommended by amalgamation of the Trilateral Flash Cycle (TFC) with an expander (reaction turbine) in a binary system to offer improved operation, economical and broader employment of the existing resources. TFC can extract heat more efficiently from hydrothermal means to improve power generation directly and decrease the emissions of greenhouse gas. A theoretical analysis using a computer based model for TFC with simple reaction turbine for three proposed diameters at various rotational speeds and operating fluids is performed. Results of output powers and turbine efficiencies of the recommended system are compared. Also, this design concludes the optimum design factors for the turbine under explicit operational settings and the factors affecting the efficiency and nozzle flow area are discussed for the TFC system.

Various Ways of Adiabatic Expansion in Organic Rankine Cycle (ORC) and in Trilateral Flash Cycle (TFC)

Abstract For energy production and conversion, the use of thermodynamic cycles is still the most common way. To find the optimal solution is a multiparametric optimization problem, where some parameters are related to thermodynamic and physical chemistry, while others are associated with costs, safety, or even environmental issues. Concerning the thermodynamic aspects of the design, the selection of the working fluid is one of the crucial points. Here, we are going to show different types of adiabatic expansion processes in various pure working fluids, pointing out the ones preferred in Organic Rankine Cycles or in Trilateral Flash Cycles. The effect of these expansions on the layout of the cycles will also be presented. Finally, we are giving a few thumb-rules, derived from thermodynamic studies, useful for energy engineers to select the proper working fluid for a given thermal system.

Experimental study of converging-diverging nozzle to generate power by Trilateral Flash Cycle (TFC)

Recovering heat from low grade heat resources for producing power is of high demand and interest. For this purpose, the an experimental study of converging-Diverging nozzle to generate power in Trilateral Flash Cycle (TFC) is investigated in this paper. In the proposed system, performance of a designed and manufactured to recover the heat and convert the heat energy to mechanical energy has been investigated. In this system, Isopentane, which is selected to be the working fluid due to its low boiling temperature, is heated by low temperature hot water and pumped through a two-phase flow nozzle, where the energy conversion takes place. In the nozzle, part of the liquid evaporates and the accelerated mixture exits the nozzle and impacts on a Pelton turbine bucket shape target. The high potential of power generation from low temperature heat resources is demonstrated through theoretical analysis. Generated force of high speed flow out of two phase nozzle has been experimentally measured in lab scale test rig and isentropic efficiency of the nozzle has been calculated based exit speed of the working fluid. Around 45% isentropic efficiency has been shown From the test results. In addition, 1.5 N–4 N force increase was detected by increasing temperature of working fluid from 30 °C to 70 °C correspondingly. The results of this experiment can be applied on a power plant waste heat as a case study, where the increased energy conversion efficiency is demonstrated on the binary cycle.

Impact of different clearance heights on the operation of a water-flooded twin-screw expander—experimental investigations based on indicator diagrams

Twin-screw expanders offer a high potential for energy conversion in the lower and medium power range, for instance in Rankine cycle systems for exhaust heat recovery. With the aim of minimising internal leakages within the expander and lubricating moving machine parts, an auxiliary liquid can be carried with the main flow or liquid working fluid can be fed to the twin-screw expander. Moreover, the operation of twin-screw expanders in Rankine cycle systems at high liquid mass fractions and in trilateral flash cycles is predicted to be a very promising application for expanders in lower power ranges. Thus, a fundamental understanding of the operation of liquid-flooded twin-screw expanders is mandatory. This paper presents results of an experimental investigation into a water-flooded twin-screw expander prototype SE 51.2 designed at the Chair of Fluidics at TU Dortmund University. On the one hand, the aspect of a two-phase working fluid is discussed considering integral characteristic numbers such as mass flow, delivery rate, and effective isentropic efficiency. On the other hand, in order to explain the influence mechanisms of a two-phase working fluid on the operating behaviour of the twin-screw expander, indicator diagrams are recorded by means of high-resolution pressure transmitters to determine indicated power. Hence, mechanical and hydraulic losses, indicated isentropic efficiency, and mechanical efficiency of the twin-screw expander can be calculated. In order to determine the influence of the narrow clearance on the hydraulic losses and the clearance sealing effect in terms of a two-phase working fluid, a systematic variation of the rotor-tip clearance height is carried out. As a result of the investigations, a water surge at the rotor tip is proved to be a significant mechanism affecting hydraulic losses in a water-flooded twin-screw expander.