Showing papers on "Thermodynamic cycle published in 2006"
TL;DR: The organic rankine cycle (ORC) was defined as a bottoming cycle in this article, which refers to the power cycle that uses waste industrial heat for power generation by supplementing heat from any f...
359 citations
TL;DR: In this paper, a model quantum heat engine operating in an Otto cycle is analyzed, where the working medium is composed of an ensemble of harmonic oscillators and changes in volume correspond to changes in the curvature of the potential well.
Abstract: The unavoidable irreversible loss of power in a heat engine is found to be of quantum origin. Following thermodynamic tradition, a model quantum heat engine operating in an Otto cycle is analysed, where the working medium is composed of an ensemble of harmonic oscillators and changes in volume correspond to changes in the curvature of the potential well. Equations of motion for quantum observables are derived for the complete cycle of operation. These observables are sufficient to determine the state of the system and with it all thermodynamical variables. Once the external controls are set, the engine settles to a limit cycle. Conditions for optimal work, power and entropy production are derived. At high temperatures and quasistatic operating conditions, the efficiency at maximum power coincides with the endoreversible result . The optimal compression ratio varies from in the quasistatic limit where the irreversibility is dominated by heat conductance to in the sudden limit when the irreversibility is dominated by friction. When the engine deviates from adiabatic conditions, the performance is subject to friction. The origin of this friction can be traced to the noncommutability of the kinetic and potential energy of the working medium.
270 citations
TL;DR: Theoretical analysis of a solar energy-powered Rankine thermodynamic cycle utilizing an innovative new concept, which uses supercritical carbon dioxide as a working fluid, is presented in this article.
171 citations
TL;DR: In this paper, the authors proposed a quasi-combined cycle with a supercritical CO2 Rankine-like cycle and a CO2 Brayton cycle, interconnected by the heat transfer process in the recuperation system.
169 citations
TL;DR: In this article, a new combined cycle was proposed to produce both power and cooling simultaneously with only one heat source and using ammonia-water mixture as the working fluid, and the simulation of the cycle was carried out in the process simulator ASPEN Plus.
160 citations
TL;DR: In this paper, a comprehensive treatment of the thermodynamics of cyclic magnetic refrigeration processes is presented, starting with a review of the work, heat and internal energy of a magnetized specimen in a magnetic field, and a list of thermodynamic potentials is given.
Abstract: A comprehensive treatment of the thermodynamics of cyclic magnetic refrigeration processes is presented. It starts with a review of the work, heat and internal energy of a magnetized specimen in a magnetic field, and a list of the thermodynamic potentials is given. These are based on the very recent discovery of an alternative Kelvin force. It is shown that this force is compatible with the internal energy proposed by Landau and Lifshitz. New formulas for the specific enthalpies are presented. Cyclic processes are discussed in detail, e.g. the Brayton, Ericsson and Carnot cycles. Magnetic refrigeration and magnetic heat pump cycles are preferably designed by applying the cascade or/and regeneration principle. Cascade systems allow wider temperature ranges to be obtained. The main objective of this article is to yield a theoretical basis for an optimal design of new magnetic refrigeration and heat pump devices.
152 citations
TL;DR: In this article, a hydrate-based refrigeration system based on a novel conceptual design is presented, which forms a closed cycle, which is more or less analogous to the conventional vapor-compression refrigeration cycle.
152 citations
TL;DR: In this article, the thermodynamics of a solar thermochemical cycle for the capture of CO2 from air are analyzed, and two approaches are examined: (1) a closed-material cycle that delivers pure CO2; and (2) an open material cycle that, additionally, co-produces hydrogen.
135 citations
Patent•
17 Aug 2006
TL;DR: In this paper, the authors describe a power plant system that can recover at least a portion of the fuel storage energy associated with a storage system for supplying fuel to the power plant systems.
Abstract: Power plant systems and processes are described that enable recovery of at least a portion of the fuel storage energy associated with a storage system for supplying fuel to the power plant systems. A first embodiment of an energy-recovery power plant system includes at least one fuel storage container and at least one expander that can receive fuel from the fuel storage container at a first pressure and provide the fuel to the power plant at a second pressure that is lower than the first pressure. A second embodiment of an energy-recovery power plant system includes a first conduit fluidly coupling the fuel storage container and the power plant for delivering fuel from the fuel storage container to the power plant and at least one regenerative thermodynamic cycle engine thermally coupled to the first conduit such that heat may be exchanged between the fuel and a working fluid for the regenerative thermodynamic cycle engine.
110 citations
TL;DR: In this article, an exergy-based approach is applied to a sub-cooled and superheated vapor compression refrigeration system for determining the optimum heat exchanger areas with the corresponding optimum subcooling and super-heating temperatures.
94 citations
TL;DR: In this paper, an alternative physical model for the detonation cycle handling propagating detonations in a purely thermodynamic fashion was presented, and the Fickett-Jacobs cycle was used to compute an upper bound to the amount of mechanical work that can be obtained from detonating a given mass of explosive.
Abstract: Propagating detonations have recently been the focus of extensive work based on their use in pulse detonation engines [1]. The entropy minimum associated with Chapman–Jouguet (CJ) detonations [2] and its potential implications on the thermal efficiency of these systems [3] has been one of the main motivations for these efforts. The notion of applying thermodynamic cycles to detonation was considered first by Zel’dovich [4], who concluded that the efficiency of the detonation cycle is slightly larger than that of a cycle using constant-volume combustion. More recently, Heiser and Pratt [3] conducted a thermodynamic analysis of the detonation cycle for a perfect gas using a one-γ model of detonations. Other studies have used constant-volume combustion as a surrogate for the detonation process [5]. This work presents two main contributions. First, we present an alternative physical model for the detonation cycle handling propagating detonations in a purely thermodynamic fashion. The Fickett–Jacobs (FJ) cycle is a conceptual thermodynamic cycle that can be used to compute an upper bound to the amount of mechanical work that can be obtained from detonating a given mass of explosive. Second, we present computations of the cycle thermal efficiency for a number of fuel-oxygen and fuel-air mixtures using equilibrium chemistry, and we discuss the strong influence of dissociation reactions on the results.
TL;DR: In this article, the thermodynamic performance of an air standard dual cycle with heat transfer loss, friction like term loss and variable specific heat of working fluid is analyzed, and the relationship between the power output and the compression ratio is derived by detailed numerical examples.
Journal Article•
TL;DR: In this paper, various indirect power cycle options for a helium cooled gas cooled fast reactor (GFR) with particular focus on a supercritical indirect cycle are investigated as an alternative to a helium-cooled direct cycle GFR.
TL;DR: In this article, the performance of solar energy powered transcritical cycle using supercritical carbon dioxide for a combined electricity and heat generation, is studied experimentally, and the experimental set-up consists of evacuated solar collectors, pressure relief valve, heat exchangers and CO2 feed pump.
Abstract: In this paper, the performance of solar energy powered transcritical cycle using supercritical carbon dioxide for a combined electricity and heat generation, is studied experimentally. The experimental set-up consists of evacuated solar collectors, pressure relief valve, heat exchangers and CO2 feed pump. The pressure relief valve is used to simulate operation of a turbine and to complete the thermodynamic cycle. A complete effort was carried out to investigate the cycle performances not only in summer, but also in winter conditions. The results show that a reasonable thermodynamic efficiency can be obtained and COP for the overall outputs from the cycle is measured at 0.548 and 0.406, respectively, on a typical summer and winter day. The study shows the potential of the application of the solar energy powered cycle as a green power/heat generation system. Copyright © 2006 John Wiley & Sons, Ltd.
TL;DR: In this paper, the available work potential that atmospheric air acquires while passing through the collector has been determined and analyzed, and the dependence of the work potential on the air flowing into the air collector from the heat gained inside the collector, air humidity and atmospheric pressure as a function of elevation are determined.
TL;DR: The Framatome ANP VHTR design for electricity production is based on an indirect cycle coupled to an “off-the-shelf” combined cycle gas turbine as mentioned in this paper.
TL;DR: In this paper, a new parameter, termed the effective COP, is used to relate the gain in cooling to the compromise in work production, which implies that per unit of cooling production, nearly equal amounts of work are compromised for combined operation.
01 Aug 2006
TL;DR: In this article, the authors describe the design, modeling, initial build and testing of a novel thermoelectric power generator (TPG), incorporating state-of-the-art material technology with optimized thermal management.
Abstract: This paper describes the design, modeling, initial build and testing of a novel thermoelectric power generator (TPG), incorporating state of the art material technology with optimized thermal management. A numerical model simulates the operation of the device and facilitates its design. Advanced multi-parameter, gradient-based optimization techniques are used to better understand the interactions between various design variables and parameters in order to progress towards an optimal TPG design. The device, made up of a series of segmented elements each comprised of up to three different materials, combines thermal isolation in the direction of flow with high power density thermoelectric (TE) material integrated directly into the heat exchanger device. Electrical current runs parallel to the heat source and sink surfaces in the device, allowing the integration of the TE material with multiple geometric degrees of freedom. This design attribute coupled with the thermal isolation thermodynamic cycle, allows each element of the TE device to be optimized semi-independently. Each p- and n-type element can have different aspect ratios (cross-sectional area divided by thickness) so that each material layer of each element has the highest possible ZT for each temperature range. The increased design flexibility helps address TE material compatibility issues associated with segmented elements and fluid flow that ordinarily degrade performance. Eliminating the impact of thermal expansion mismatch while still maintaining excellent thermal and electrical contacts is also a design goal. Additional design considerations are also discussed, including electrical and thermal connector design and minimizing interfacial resistances. The device described is suitable for both waste heat recovery and primary power applications. Initial test results from prototype builds are discussed
TL;DR: In this article, the authors characterized the amount of heat leakage as a percentage of the fuel's energy and derived a more realistic and precise relationship between fuel's chemical energy and the heat leakage through the resulting temperature.
TL;DR: In this article, a thermo-ecological performance analysis of an irreversible intercooled and regenerated closed Brayton heat engine exchanging heat with variable-temperature thermal reservoirs is presented.
Abstract: A thermo-ecological performance analysis of an irreversible intercooled and regenerated closed Brayton heat engine exchanging heat with variable-temperature thermal reservoirs is presented. The effects of intercooling and regeneration are given special emphasis and investigated in detail. A comparative performance analysis considering the objective functions of an ecological coefficient of performance, an ecological function proposed by Angulo-Brown and power output is also carried out. The results indicate that the optimal total isentropic temperature ratio and intercooling isentropic temperature ratio at the maximum ecological coefficient of performance conditions (ECOPmax) are always less than those of at the maximum ecological function ( ) and the maximum power output conditions ( ) leading to a design that requires less investment cost. It is also concluded that a design at ECOPmax conditions has the advantage of higher thermal efficiency and a lesser entropy generation rate, but at the cost of a slight power loss.
Patent•
12 Oct 2006
TL;DR: In this article, a high-efficiency heat cycle system including a compressor, a first turbine, first and second heat exchangers 7 and 8, an expander, and a composite heat cycle power generator using the high efficiency heat cycle was described.
Abstract: A high-efficiency heat cycle system including a compressor, a first turbine, first and second heat exchangers 7 and 8, a first pump, and an expander, and a composite heat cycle power generator using the high-efficiency heat cycle system. Working gas Fg compressed in the compressor (C) drives a first turbine (S) and is thereafter cooled by passing through a heat dissipating side of a first heat exchanger (7) and then raised in pressure by a first pump (P) to form high-pressure working liquid Fe, the high-pressure working liquid is expanded and evaporated in an expander (K) to form working gas Fg, said working gas Fg is heated by passing through a heat receiving side 82 of the second heat exchanger before being introduced into the compressor C. A heat dissipating side 81 of the second heat exchanger comprises a heat dissipating portion of a refrigerating machine or a heat dissipating portion for waste heat from a heating machine.
Patent•
03 Nov 2006
TL;DR: In this paper, a dual thermodynamic cycle system was proposed that utilizes the liquid-to-gas phase transitions of a cryogenic fluid such as liquid nitrogen and a working fluid (214) such as sulfur hexafluoride to drive prime movers.
Abstract: Systems and methods for converting thermal energy, such as solar energy, from a localized thermal energy source to another form of energy or work comprise dual thermodynamic cycle systems (202, 210, 216 and 206, 208, 214, 228222, 212) that utilize the liquid-to-gas phase transitions of a cryogenic fluid (202) such as liquid nitrogen and a working fluid (214) such as sulfur hexafluoride to drive prime movers (216, 222). Heat transfer (204, 211) between the fluids as they undergo the phase transitions is used to increase the energy in the system and its work output, and improve system efficiency.
TL;DR: In this article, a detailed parametric study of an irreversible regenerative Brayton refrigerator cycle using the new thermoeconomic approach is presented, where the external irreversibility is due to finite temperature difference between the cycle and the external reservoirs while the internal irreversibilities are due to the nonisentropic compression and expansion processes and the regenerative loss.
Abstract: The detailed parametric study of an irreversible regenerative Brayton refrigerator cycle using the new thermoeconomic approach is presented in this paper. The external irreversibility is due to finite temperature difference between the cycle and the external reservoirs while the internal irreversibilities are due to the nonisentropic compression and expansion processes and the regenerative loss. The thermoeconomic objective function defined as the cooling load per unit cost is optimized with respect to the state point temperatures for a typical set of operating conditions. The power input and cooling load are found to be decreasing functions of the expansion outlet temperature (T1), while it is the reverse in the case of COP. On the other hand, there are optimal values of the temperature T1, cooling load, power input and COP at which the cycle attains the maximum objective function for a typical set of operating parameters. Again, the objective function, COP and cooling load further enhance, while the power input goes down, as the various values of the effectiveness or efficiency components are increased.
TL;DR: In this article, the performance of air cycle refrigerator driving air conditioning system integrated desiccant system is evaluated and the system feasibility is examined, the system has such characteristics that safe material of air and water are used as a refrigerant, waste heat from air cycle fridge performs the regeneration of descant material for energy saving.
Abstract: This study presents theoretical investigation on the performance of air cycle refrigerator driving air conditioning system integrated desiccant system. Total system performance is evaluated and the system feasibility is examined. The system has such characteristics that (1) safe material of air and water are used as a refrigerant, (2) waste heat from air cycle refrigerator performs the regeneration of desiccant material for energy saving. It has been clarifying that (1) controlling the evaporative cooling process in air washer, the system can operate for a wide range of cooling loads, (2) the total coefficient of performance on air conditioning system is better than the conventional vapor compression system with reheating coil, and (3) the system performance highly depends on the ratio of the amount of outdoor intake air to the supply air.
TL;DR: In this paper, the optimal ecological performance of a universal endoreversible steady flow heat engine cycle consisting of a constant thermal capacity heating branch, a thermal capacity cooling branch and two adiabatic branches with heat transfer loss is derived by taking an ecological optimisation criterion as the objective.
Abstract: SYNOPSIS The optimal ecological performance of a universal endoreversible steady flow heat engine cycle consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches with heat transfer loss is derived by taking an ecological optimisation criterion as the objective, which consists of maximising a function representing the best compromise between the power output and exergy loss rate of the heat engine. Some special examples are discussed. A numerical example is given to show the effects of heat reservoir temperature ratio on the ecological criterion versus the efficiency characteristic of the cycle. The results include the performance characteristics of endoreversible steady flow Diesel, Otto, Atkinson and Brayton cycles. The results can provide some theoretical guidance for the design of practical engines.
TL;DR: In this article, the performance of the Bose-Stirling refrigeration cycle is investigated, based on the equation of state of an ideal Bose gas, which is different from other thermodynamic cycles such as the Carnot cycle, Ericsson cycle, Brayton cycle, Otto cycle, Diesel cycle and Atkinson cycle.
TL;DR: In this article, a coal-based combined cycle power plant, which consists of a PCFB partial gasification unit and an atmospheric circulating fluidized bed (ACFB) char combustion unit, was investigated.
Abstract: In the present paper thermodynamic analyses, i.e. both energy and exergy analyses have been conducted for a coal based combined cycle power plant, which consists of pressurized circulating fluidized bed (PCFB) partial gasification unit and an atmospheric circulating fluidized bed (ACFB) char combustion unit. Dual pressure steam cycle is considered for the bottoming cycle to reduce irreversibilities during heat transfer from gas to water/steam. The effect of operating variables such as pressure ratio, gas turbine inlet temperature on the performance of combined cycle power plant has been investigated. The pressure ratio and maximum temperature (gas turbine inlet temperature) are identified as the dominant parameters having impact on the combined cycle plant performance. The work output of the topping cycle is found to increase with pressure ratio, while for the bottoming cycle it decreases. However, for the same gas turbine inlet temperature the overall work output of the combined cycle plant increases up to a certain pressure ratio, and thereafter not much increase is observed. The entropy generation, the irreversibilities in each component of the combined cycle and the exergy destruction/losses are also estimated. Copyright © 2005 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors proposed a quasi-combined cycle with a supercritical CO 2 Rankine type cycle and a CO 2 Brayton cycle, interconnected by the heat transfer process in the recuperation system.
Abstract: A novel liquefied natural gas (LNG) fueled power plant is proposed, which has virtually zero CO 2 and other emissions and a high efficiency. Natural gas is fired in highly enriched oxygen and recycled CO 2 flue gas. The plant operates in a quasi-combined cycle mode with a supercritical CO 2 Rankine type cycle and a CO 2 Brayton cycle, interconnected by the heat transfer process in the recuperation system. By coupling with the LNG evaporation system as the cycle cold sink, the cycle condensation process can be achieved at a temperature much lower than ambient, and high-pressure liquid CO 2 ready for disposal can be withdrawn from the cycle without consuming additional power. Good use of the coldness exergy and internal exergy recovery produced a net energy and exergy efficiencies of a base-case cycle over 65% and 50%, respectively, which can be increased up to 68% and 54% when reheat is used. Cycle variants incorporating reheat, intercooling, and reheat+intercooling, as well as no use of LNG coldness, are also defined and analyzed for comparison. The approximate heat transfer area needed for the different cycle variants is also computed. Besides electricity and condensed CO 2 , the byproducts of the plant are H 2 O, liquid N 2 and Ar.
TL;DR: In this article, a general model of an irreversible Ericsson refrigeration cycle employing paramagnetic materials as the working substance is presented, in which multi-irreversibilities such as finite-rate heat transfer, regenerative loss, heat leak, efficiency of regenerator and internal irreversibility resulting from magnetic working substances are taken into account.
Abstract: A general model of an irreversible Ericsson refrigeration cycle employing paramagnetic materials as the working substance is presented, in which multi-irreversibilities such as finite-rate heat transfer, regenerative loss, heat leak, efficiency of regenerator and internal irreversibility resulting from magnetic working substances are taken into account. On the basis of the general thermodynamic properties of paramagnetic materials and the optimal-control theory, the optimal mathematical expressions of cooling load, coefficient of performance and power input of the irreversible Ericsson refrigeration cycle using paramagnetic materials as the working substance are derived. By means of a numerical approach, the influence of the heat leak, the internal irreversibility, the efficiency of regenerator, the ratio of the magnetic fields on the cyclic performance characteristics of the refrigeration cycle are revealed and discussed in detail. Some important performance bounds, e.g. the maximum cooling load and the corresponding coefficient of performance, the maximum coefficient of performance and the corresponding cooling load, are determined and evaluated. Furthermore, several special cases may be deduced from the primary results in this paper. The conclusions obtained in the present paper are more general and useful than those existing in literature and can provide some new important information for the optimal design and performance improvement of magnetic refrigerators.
01 Jan 2006
TL;DR: In this article, the authors describe the fundamental effects of inlet flow distortion on the performance of gas turbines and evaluate their performance with an integrated parallel compressor model, showing that the performance loss due to distortion is small since the efficiency values in the two sectors are only a bit lower than the efficiency at a comparable operating point with clean inlet flows.
Abstract: The main problem with aircraft engine inlet flow distortion is its effect on the stability of the compression system. However, distortion does also influence the performance delivered by the propulsion system. There are two fundamentally different reasons for the change in performance: First there is the impact of the flow distortion on the component efficiencies and thus the thermodynamic cycle and second there are performance changes due to actions of the control system. This paper describes how the fundamental effects of inlet flow distortion on the performance of gas turbines can be evaluated with any engine performance program that employs an integrated parallel compressor model. This sort of simulation is a valuable tool for evaluating the basic effects of complex flow phenomena on the performance of a gas turbine. It delivers fundamentally correct answers since even the most complex flow structures obey the laws of mass and energy conservation and that’s all what the overall system simulation is about. In the parallel compressor model both pressure and temperature distortions are quantified with coefficients which relate the pressure (respectively temperature) in the spoiled sector to the value in the clean sector. In single compressor engines the static pressure at the exit of the clean sector equals that of the distorted sector. This hypothesis does not hold true with multi-compressor engines because the short inter-compressor ducts, which often contain struts or vanes, do not allow the mass flow transfer over the sector borders which would be required for balancing the static pressures. The degree of aerodynamic coupling of compressors in series can be described in the performance simulation program by a coupling factor. From the engine system simulation results it becomes clear why inlet flow distortion has only a minor impact on the thermodynamic cycle if the comparison of the two operating conditions (with clean and distorted inlet flow) is made at the properly averaged engine inlet conditions. For each compressor the parallel compressor theory yields two operating points in the map, one for the clean sector and one for the spoiled sector. The performance loss due to distortion is small since the efficiency values in the two sectors are only a bit lower than the efficiency at a comparable operating point with clean inlet flow. However, the control system of the engine can react to the inlet flow distortion in such a way that the thrust delivered changes significantly. This is particularly true if a compressor bleed valve or a variable area nozzle is opened to counteract compressor stability problems. Especially using re-circulating bleed air to increase the surge margin of a compressor affects the performance of the engine negatively. Two examples show clearly that the pro and cons of re-circulating bleed can only be judged with a full system simulation, looking at the surge line improvement alone can be misleading.Copyright © 2006 by ASME