Showing papers on "Thermodynamic cycle published in 1997"
Book•
01 Jan 1997
TL;DR: The seminal book on gas turbine technology has been a bestseller since it was first published as mentioned in this paper, which includes a comprehensive set of software programs that complement the text with problems and design analyses.
Abstract: This seminal book on gas turbine technology has been a bestseller since it was first published. It now includes a comprehensive set of software programs that complement the text with problems and design analyses. Software topics included are atmosphere programs, quasi-one-dimensional flow programs (ideal constant-area heat interaction, adiabatic constant-area flow with friction, rocket nozzle performance, normal shock waves, oblique shock waves), gas turbine programs (engine cycle analysis and engine off-design performance), and rocket combustion programs (Tc and PC given, He and PC given, isentropic expansion).
200 citations
TL;DR: In this paper, up-to-date thermodynamic properties for LiBr/H2O and H2O/NH3 solution are compiled and used in cycle simulation and the results form a source of reference for developing new cycles and searching for new absorbent/refrigerant pairs.
170 citations
TL;DR: In this article, the performance of a closed Brayton cycle with regeneration is evaluated using finite-time thermodynamic analysis. And the authors show that the power output can be maximized with judicious selection of parameters such as the heat exchanger surface areas and the heat conductances.
110 citations
TL;DR: In this paper, an irreversible Carnot heat engine with finite thermal capacitance rates and finite total conductance of the heat exchangers was optimized with respect to the cycle temperature ratio and the heat conductance ratio.
Abstract: Finite-time thermodynamics with an ecological criterion is applied to an irreversible Carnot heat engine with finite thermal capacitance rates of the heat reservoirs and finite total conductance of the heat exchangers. The ecological function is defined as the power output minus the loss power or the product of the environmental temperature and the entropy production rate. The ecological function is optimized with respect to the cycle temperature ratio and the heat conductance ratio. It is shown that the ecological function is a useful and important criterion for the design of an irreversible Carnot heat engine, considering not only power output but also entropy generation and thermal efficiency. The optimum values of cycle temperature ratios and conductance ratios of irreversible Carnot heat engines are presented. Moreover, from the viewpoint of the ecological function, the thermal capacitance of the cold external fluid should be larger than that of the hot external fluid and the heat conductance of the hot-end heat exchanger should be smaller than that of the cold-end heat exchanger.
87 citations
TL;DR: In this paper, the authors present analytical studies of a fractional horse-power rotary refrigeration compressor and its performance comparison with measured results, and they employ a general-purpose performance model by considering the thermodynamic cycle of the compressor and their mechanical losses.
67 citations
TL;DR: In this article, a real absorption refrigeration cycle on a temperature-entropy diagram, step-by-step idealisations of the binary mixture, together with the thermodynamic transformations are considered, in order to derive the ideal thermodynamic absorption cycle performance and temperature formulae.
Abstract: Starting from the representation of a real absorption refrigeration cycle on a temperature-entropy diagram, step-by-step idealisations of the binary mixture, together with the thermodynamic transformations are considered, in order to derive the ideal thermodynamic absorption cycle performance and temperature formulae It is demonstrated that the ideal absorption cycle is the combination of a Carnot driving cycle with a reverse Carnot cooling cycle The resorption cycle is analysed in the same manner Information is included on absorption cooling with heat recovery cycles, heat pumps and temperature amplifiers From the analysis of single-stage cycles, and by superimposing absorption cycles operating at different temperatures and utilising specific residual heat of the higher temperature sub-cycles, the performance and temperature relations of double, triple and multistage cycles are derived Special attention is given to three types of triple-stage cycle and their ideal equivalence is demonstrated and represted on the pressure-temperature-concentration (PTX) diagram A simple hybrid absorption-compression cycle is analysed and the results are compared with those of ideal cold generation cycles (combinations of driving and cooling cycles) Consideration is also given to cold generation systems Finally, the validation of the fundamental thermodynamics of absorption cycles is presented by applying an exergy analysis This paper presents the thermodynamic principles involved to obtain simple formulae, in a similar way to the Carnot cycle in order to convey the ideal theoretical limitations
60 citations
TL;DR: In this article, the Stirling heat engine operating in a closed regenerative thermodynamic cycle is analyzed and the maximum power density and efficiency are found and the compression ratio at maximum power densities is determined.
58 citations
01 Mar 1997
TL;DR: In this paper, a hybrid gas turbine cycle is proposed based on the conventional Brayton cycle for the high-temperature heat addition process while adopting the Ericsson cycle for low temperature heat rejection process, which incorporates the thermodynamic advantages of a combined gas and steam turbine (CCGT) cycle without the irreconstrainabilities of the boiler and the ancillarics of the steam turbine/condenser plant.
Abstract: A hybrid gas turbine cycle is proposed based on the conventional Brayton cycle for the high-temperature heat addition process while adopting the Ericsson cycle for the low-temperature heat rejection process. It thus incorporates the thermodynamic advantages of a combined gas and steam turbine (CCGT) cycle without the irrevcrsibilities of the boiler and the ancillarics of the steam turbine/condenser plant. Thermodynamic analysis shows that a similar overall thermal efficiency as current CCGT plant (i.e. 0.54) would be achieved at a maximum gas temperature of 1311 °C if polytropic efficiencies of 0.90 for compression and expansion could be realized and if a maximum temperature of 77 °C was obtained during isothermal compression in the bottoming Ericsson cycle.A novel method of achieving multistage isothermal compression using heat pipe technology is proposed.
57 citations
TL;DR: In this paper, the HAT cycle is compared with simple-cycle gas-turbine, recuperated (and the intercooled-recuperated) gas-to-compressed-air (EC) cycle, STIG cycle, and combined-cycle cycle.
56 citations
TL;DR: In this article, a second-law analysis based on the concept of entropic mean temperatures is developed for adsorption cycles with thermal regeneration, which is a combination of a Carnot engine cycle and a Joule heat pump cycle.
49 citations
Journal Article•
TL;DR: In this article, the performance of an irreversible Brayton heat engine was analyzed and analytical formulae related to power output, pressure ratio and efficiency of the heat engine coupled to either constant or variable-temperature heat reservoirs were derived.
Abstract: The performance of an irreversible Brayton heat engine is analysed. Analytical formulae related to power output, pressure ratio and efficiency of the heat engine coupled to either constant- or variable-temperature heat reservoirs are derived. The irreversibilities considered include heat-resistance losses in the hot- and cold-side heat-exchangers, and non-isentropic expansion and compression losses in the turbine and compressor. The optimal performance characteristics of the heat engine are obtained by optimisation of the distribution of heat conductances or heat-transfer surface areas between the heat-exchangers, and the matching of working fluid and heat reservoirs.
TL;DR: In this paper, the authors proposed a combustion chamber in which an isothermal heat addition is approximated by a converging duct featuring discrete combustion sites positioned along the streamwise direction.
Abstract: A thermodynamic study indicates that the hypothetical modification of gas-turbine engines to include two heat additions rather than one may result in significant efficiency improvements of over 4% compared with conventional engines. Specifically, the usual constant pressure heat addition would be constrained to a given temperature and then further heat addition carried out in a manner approaching an isothermal process. Owing to the limited peak combustion temperature of the overall heat addition process, the emissions of NO X may be reduced by as much as 50%, thus offering an environmental benefit as well as an efficiency advantage. This paper details the analysis of a proposed combustion chamber in which an isothermal heat addition is approximated. The combustion chamber would consist of a converging duct featuring discrete combustion sites positioned along the streamwise direction. A numerical analysis developed to assess the deviation from isothermal flow in the combustion chamber shows that a reasonable approximation of such a heat addition may be possible with two or more combustion sites. Moreover, a simplified treatment of the combustion process implies that flame stabilization at these sites is feasible.
TL;DR: In this paper, the authors proposed a combined absorption/compression refrigeration system, where different power generation and distribution efficiencies are considered in deriving the primary energy ratios. And they showed that up to a 10% increase in overall efficiency can be achieved using combined absorption and compression.
31 Dec 1997
TL;DR: In this article, a computer model (Cycle Analysis Simulation Tool, CAST) and a methodology have been developed to perform value analysis for small, low- to moderate-temperature binary geothermal power plants.
Abstract: A computer model (Cycle Analysis Simulation Tool, CAST) and a methodology have been developed to perform value analysis for small, low- to moderate-temperature binary geothermal power plants. The value analysis method allows for incremental changes in the levelized electricity cost (LEC) to be determined between a baseline plant and a modified plant. Thermodynamic cycle analyses and component sizing are carried out in the model followed by economic analysis which provides LEC results. The emphasis of the present work is on evaluating the effect of mixed working fluids instead of pure fluids on the LEC of a geothermal binary plant that uses a simple organic Rankine cycle. Four resources were studied spanning the range of 265/spl deg/F to 375/spl deg/F. A variety of isobutane and propane based mixtures, in addition to pure fluids, were used as working fluids. This study shows that the use of propane mixtures at a 265/spl deg/F resource can reduce the LEC by 24% when compared to a base case value that utilizes commercial isobutane as its working fluid. The cost savings drop to 6% for a 375/spl deg/F resource, where an isobutane mixture is favored. Supercritical cycles were found to have the lowest cost at all resources.
TL;DR: In this article, a general irreversible cycle model is used to investigate the optimal performance of a class of heat-driven pumps affected by the three main irreversibilities, which are finite-rate heat transfer between the working fluid and the external heat reservoirs, internal dissipation due to the working liquid and heat leakage between heat reservoirs.
Abstract: A general irreversible cycle model is used to investigate the optimal performance of a class of heat-driven pumps affected by the three main irreversibilities, which are finite-rate heat transfer between the working fluid and the external heat reservoirs, internal dissipation due to the working fluid and heat leakage between heat reservoirs. The coefficient of performance of the cycle system is taken as an objective function for optimization. Some equivalent parameters are introduced so that the relevant calculation is simplified. The coefficient of performance versus dimensionless heating load curves describing the general performance characteristics of heat-driven heat pumps are plotted. The optimal temperatures of the working fluid at the maximum coefficient of performance are determined. Moreover, it is expounded that the irreversible cycle model is very useful. The optimal performance not only of a class of irreversible heat-driven refrigerators but also of an irreversible Carnot heat pump and refrigerator may be directly analysed by using the cycle model. The results obtained may provide some new theoretical bases for the optimal design and operation of two classes of real heat pump and refrigerator systems driven by `low-grade' heat energy and `high-grade' work.
Patent•
03 Dec 1997TL;DR: In this paper, a method and apparatus for recovering energy from wastes is used to recover energy by gasifying wastes such as municipal waste such as waste, and delivering heat recovered in the heat exchanging unit to a heat cycle to generate electric energy.
Abstract: A method and apparatus for recovering energy from wastes is used for recovering energy by gasifying wastes such as municipal waste. The method comprises gasifying wastes in a fluidized-bed gasification furnace at a relatively low temperature; introducing gaseous material and char produced in the fluidized-bed gasification furnace into a melting furnace; gasifying the gaseous material and char in the melting furnace at a relatively high temperature; introducing gas produced in the melting furnace into a heat exchanging unit; and delivering heat recovered in the heat exchanging unit to a heat cycle to generate electric energy.
TL;DR: In this article, the influence of an internal heat leak on the optimal performance of heat engines is examined and the relation between optimal power output and efficiency for a steady state irreversible heat engine with irreversibilities due to external heat resistance and internal heat leakage is derived.
Patent•
02 Apr 1997
TL;DR: In this paper, a precooled vapor-liquid refrigeration cycle includes a basic vapor liquid cycle (24) and an auxiliary regenerative vapor-liquide cycle (26) having a heat exchange relationship (18') between them.
Abstract: A precooled vapor-liquid refrigeration cycle includes a basic vapor-liquid cycle (24) and an auxiliary regenerative vapor-liquid cycle (26) having a heat exchange relationship (18') between them. The basic cycle (24) includes a compressor (10) connected in series with a condenser (12), throttle device (14), and evaporator (16). The auxiliary cycle (26) includes a compressor (10'), condenser (12'), throttle device (14'), and a counterflow heat exchanger (18'), successively connected. The cycles each have condensers (12, 12') that are cooled by ambient air; the basic cycle is able to operate independently of the auxiliary cycle. To maximize the coefficient of performance, the basic cycle (24) operates with a small pressure differential between compressor discharge (G) and return (f). Efficiency of the basic cycle and the system COP are improved. The refrigerant leaving the condenser (12') in auxiliary cycle (26) after passing through the auxiliary throttle device (14'), flows through the heat exchanger (18') in the counterflow arrangement with the very same refrigerant stream.
TL;DR: In this paper, the authors proposed a self-regulated pressure HRSG, steam-air cooling of the turbine blades and a fully automated computerized process control to implement fast start-up and shut-down.
TL;DR: In this article, a general cycle model including several major irreversibilities existing usually in real heat transformer systems is established and used to investigate the optimal performance of a heat transformer affected by the irreversibility of finite-rate heat transfer between the working fluid and the external heat reservoirs, heat leak losses of the heated space, and internal dissipation of working fluid.
Abstract: A general cycle model including several major irreversibilities existing usually in real heat transformer systems is established and used to investigate the optimal performance of a heat transformer affected by the irreversibilities of finite-rate heat transfer between the working fluid and the external heat reservoirs, heat leak losses of the heated space, and internal dissipation of the working fluid. The coefficient of performance and the specific heating load of the cycle system are used in turn as objective functions for optimization. The maximum values of these parameters are calculated for a given total heat-transfer area of heat exchangers. The dimensionless specific heating load versus coefficient of performance curves describing the general performance characteristics of heat transformers are presented. The practical operating region of the heat transformer is discussed.
01 Jan 1997
TL;DR: In this paper, a trade-off evaluation of the Neon Brayton cycle and the Hydrogen Claude cycle has been conducted and the decision was made based on the results of these process calculation.
Abstract: In WE-NET(World Energy NET work) project, liquid hydrogen is the most expected energy carrier for the clean erergy system which doesn`t discharge carbon dioxide. For this system it is necessary to develop a large scale hydrogen liquefaction plant with high process efficiency for this system. The liquefaction capacity of 300t/day for one plant is estimated to be suitable and the target process efficiency is set to be more than 40% Carnot. Up to now Hydrogen Claude cycle, Helium Brayton cycle, Neon Brayton cycle have been studied. Based on the results of these process calculation a trade-off evaluation has been conducted. Though the Neon Brayton cycle gives the best efficiency, Hydrogen Claude cycle and Helium Brayton cycle has been chosen for further detailed study.
Journal Article•
TL;DR: In this article, the thermodynamic performance of isentropic closed regenerated Brayton refrigeration cycles coupled with constant and variable-temperature heat reservoirs has been analyzed and the relations between cooling load and pressure ratio, and between COP (coefficient of performance) and pressure ratios are derived for the two cases of heat reservoirs.
Abstract: Finite-time thermodynamic performance of isentropic closed regenerated Brayton refrigeration cycles coupled to constant- and variable-temperature heat reservoirs has been analyzed in this paper The relations between cooling load and pressure ratio, and between COP (coefficient of performance) and pressure ratio are derived for the two cases of heat reservoirs In the analysis, the sole irreversibilities are the heat resistance losses in the heat exchangers between working fluid and the high- and low-temperature heat reservoirs and in the regenerator A numerical example is also given
TL;DR: In this paper, a triple-effect cycle absorption heat pump was investigated using OSU-ABSIM, a modular steady state simulation program, where ammonia-water solution was used as the working fluid for the upper, high pressure cycle, while ammonia-water and ammonia-sodium thiocyanate solutions were investigated for the lower pressure cycle.
TL;DR: In this paper, a heat engine operating on the afterburning Ericsson cycle was proposed, whose principle is heat addition to the cycle by an afterburner in which fuel is burned with the low-pressure air working fluid exhausted by the expander and resulting combustion gases are used in a countercurrent heat exchanger continually heating.
Abstract: This invention is a heat engine operating on the afterburning Ericsson cycle whose principle is heat addition to the cycle by an afterburner in which fuel is burned with the low-pressure air working fluid exhausted by the expander The resulting combustion gases are used in a countercurrent heat exchanger continually heating (1) the air expanding in the expander and (2) further upstream the high-pressure air (compressed by the compressor) in the regenerator The ideal efficiency of this cycle is the Carnot cycle efficiency between the same top and bottom temperatures Practical engines are more efficient than those in which heat addition takes place upstream of the expander All moving parts are only exposed to clean air, and expander valves can be operated at temperatures comparable to current internal combustion engines Liquid or gaseous fuels can be used and control of speed and power is simple, based on keeping engine temperatures constant With the low-pressure continuous combustion, pumping and sealing problems are easily solved, engine noise level is low, and air-polluting emissions are minimal Dual-cylinder engines with synchronized alternating pistons give rise to completely constant afterburner conditions which avoid thermal transients and facilitate engine operation The performance of afterburning Ericsson cycle engines exceeds that of current internal combustion engines, in terms of thermal efficiency and specific fuel consumption
TL;DR: In this paper, an innovative gas turbine cycle is studied, which can offer several advantages from the point of view of environmental friendship and peakload shaving capabilities; however, water injection produces a power boosting effect (at the expense of a small decrease in efficiency).
TL;DR: De Ruyck et al. as mentioned in this paper proposed a new evaporative cycle layout that is shown to have a performance similar to the HAT cycle, but where the saturation tower has been eliminated.
Abstract: A new evaporative cycle layout is disclosed that is shown to have a performance similar to the HAT cycle, but where the saturation tower has been eliminated. This new cycle is a result of a combined exergetic and composite curve analysis discussed in a previous paper, assuming one intercooler and no reheat (De Ruyck et al., 1995). The new cycle uses two-phase flow heat exchange in the misty regime, which is a well-known process. Existing aeroderivative gas turbine equipment can be adapted for application of this cycle, which therefore needs a minimum of development.
TL;DR: In this article, the influence of bypass heat leak on the optimal performance of a combined refrigeration cycle is examined by adding a heat leak term into an endoreversible combined cycle.
TL;DR: In this paper, the optimal performance of a corrugated, collector-driven, irreversible Carnot heat engine and an absorption refrigerator was investigated using the technique of energetic optimization, and a minimum operating parameter and a relation between the maximum overall efficiencies were obtained for the systems under consideration.
TL;DR: In this paper, the thermodynamic efficiencies of selected HFCs (hydrofluorocarbons) have been investigated for applications in binary geothermal conversion systems and their interactions with sensible heat sources were considered.
TL;DR: In this article, a sinusoidal model is proposed to analyze the thermodynamic processes of gas parcels oscillating in a regenerator, where the regenerator is considered equivalent to a bundle of capillary tubes with large thermal capacities.
Abstract: A sinusoidal model is proposed to analyze the thermodynamic processes of gas parcels oscillating in a regenerator. The regenerator is considered equivalent to a bundle of capillary tubes with large thermal capacities. With perfect thermal contact between the gas and tube wall and the proper phase shift between velocity and pressure, the overall effect of a gas parcel oscillating in the capillary in one cycle is that it absorbs heat from one lengthwise part of the wall and delivers heat to the other part of the wall within its range of displacement. Each gas parcel working in the regenerator undergoes a thermodynamic cycle. When the work flow is in the same direction as the temperature gradient of the regenerator, it undergoes a heat engine cycle. Otherwise it undergoes a refrigeration cycle. The regenerator can work as a heat engine or as a refrigerator.