Results 1 - 10 of 190
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[en] In this research, a vortex generator heat exchanger is used to recover exergy from the exhaust of an OM314 diesel engine. Twenty vortex generators with 30° angle of attack are used to increase the heat recovery as well as the low back pressure in the exhaust. The experiments are prepared for five engine loads (0, 20, 40, 60 and 80% of full load), two exhaust gases amount (50 and 100%) and four water mass flow rates (50, 40, 30 and 20 g/s). After a thermodynamical analysis on the obtained data, an optimization study based on Central Composite Design (CCD) is performed due to complex effect of engine loads and water mass flow rates on exergy recovery and irreversibility to reach the best operating condition. - Highlights: • A vortex generator heat exchanger is used for diesel exhaust heat recovery. • A thermodynamic analysis is performed for experimental data. • Exergy recovery, irreversibility are calculated in different exhaust gases amount. • Optimization study is performed using response surface method
[en] This paper shows a possible way to achieve a thermoeconomic optimization of combined cycle gas turbine (CCGT) power plants. The optimization has been done using a genetic algorithm, which has been tuned applying it to a single pressure CCGT power plant. Once tuned, the optimization algorithm has been used to evaluate more complex plants, with two and three pressure levels in the heat recovery steam generator (HRSG). The variables considered for the optimization were the thermodynamic parameters that establish the configuration of the HRSG. Two different objective functions are proposed: one minimizes the cost of production per unit of output and the other maximizes the annual cash flow. The results obtained with both functions are compared in order to find the better optimization strategy. The results show that it is possible to find an optimum for every design parameter. This optimum depends on the selected optimization strategy
[en] This communication presents thermodynamic methodology for the performance evaluation of combustion gas turbine cogeneration system with reheat. The energetic and exergetic efficiencies have been defined. The effects of process steam pressure and pinch point temperature used in the design of heat recovery steam generator, and reheat on energetic and exergetic efficiencies have been investigated. From the results obtained in graphs it is observed that the power to heat ratio increases with an increase in pinch point, but the first-law efficiency and second-law efficiency decreases with an increase in pinch point. The power to heat ratio and second-law efficiency increases significantly with increase in process steam pressure, but the first-law efficiency decreases with the same. Results also show that inclusion of reheat, provide significant improvement in electrical power output, process heat production, fuel-utilization (energetic) efficiency and second-law (exergetic) efficiency. This methodology may be quite useful in the selection and comparison of combined energy production systems from thermodynamic performance point of view
[en] This paper presents the results of a theoretical investigation on the influence of different heat transfer correlations for finned-tubes to the dynamic behavior of a heat recovery steam generator (HRSG). The investigation was done for a vertical type natural circulation HRSG with 3 pressure stages under hot start-up and shutdown conditions. For the calculation of the flue gas-side heat transfer coefficient the well known correlations for segmented finned-tubes according to Schmidt, VDI and ESCOATM (traditional and revised) as well as a new correlation, which was developed at the Institute for Energy Systems and Thermodynamics, are used. The simulation results show a good agreement in the overall behavior of the boiler between the different correlations. But there are still some important differences found in the detail analysis of the boiler behavior. - Research highlights: → Numerical simulation is performed to explore the influence of different heat transfer correlations for finned-tubes to the dynamic behavior of a heat recovery steam generator. → Differences in the steam generator behavior are found. → In the worst case the boiler can lead to unfavorable operation conditions, e.g. reverse flow.
[en] Single Stage Heat Transformer (SSHT) is a device to recovery waste heat by a thermodynamic cycle. In this paper an experimental SSHT prototype was analyzed. This prototype operates with Water/Carrol mixture. Four test runs were carried out in order to evaluate the performance. The heat powers were measured from 0.99 to 1.35 kW for the generator, 0.97–1.33 kW for the condenser, 0.99–1.35 kW for the evaporator and 0.69–0.81 kW for the absorber. Experimental Gross Temperature Lift (GTL) was values from 18.5 to 22.2 °C and the dimensionless Coefficient of Performance (COP) was calculated for those operating conditions from 0.30 to 0.35.
[en] An equipment flow sheet has been developed for a mobile pilot-plant (MPP) to produce environmentally clean steam. The unit consists of a single-stage heat transformer (SSHT) coupled to a mechanical vapour recompression system (MVR) with a nominal output capacity of 260 kg/h of saturated steam at 3 bar absolute pressure for a liquid feed at a temperature of 80oC. It is proposed to have the unit on skids to be transported by a pickup truck or lorry to various industrial locations for demonstration and training purposes, in order to acquaint industrialists with an environmentally clean and energy-efficient technology. (author)
[en] This paper aims at proposing a simplified method for the evaluation of the potential heat energy saving in existing industrial systems through technology optimisation and improved heat recovery. For this purpose heat network analysis is carried out using guided redesign of the technology based on process integration. This results in an improvement in the internal heat exchange consequently minimising the exit exergy and in this way reducing the energy supply. For further efficiency improvement the application of enhanced low-grade heat recovery is proposed using direct phase contact heat exchange and pre-humidification of the boiler combustion air at the expense of waste heat. The application of the method and the resulting potential efficiency improvement is presented. A medium-sized company which produces sliced cooked meats is used as an example. This is a very typical case study for the food industry, represented mainly by Small to Medium-sized Enterprises (SMEs), which have relatively low energy efficiency due to non-optimisation of the heat network and substantial waste heat and effluent emissions. A substantial energy efficiency improvement is achieved resulting in about 30% heat saving at 12.1% reduced fuel consumption. Further hot water production at 70 °C corresponding to 61% of the original steam production is available without additional fuel consumption, if required. Finally a reduction of 1.9 times effluent and up to 2.7 times NOx gas emissions is estimated. - Highlights: • Comparative exergy analysis for potential waste heat reduction is discussed. • Simplified method for efficiency improvement is proposed. • The method is applied to an industrial case study. • Improved low grade waste heat recovery technique is presented
[en] Heat recovery from automotive engines has been predominantly for turbo-charging or for cabin heating. Studies relative to application of the recovered heat to run absorption chillers is scarce. In this project, a 10.55 kW (three ton) absorption chiller was modified for hot gas intake and matched to a 2.8 L V6 internal combustion engine. Mathematical model and experimental test results suggest that the concept is thermodynamically feasible and could significantly enhance system performance depending on part-load of the engine. However, possible challenges during transient operations as well as issues related to scalability and reliability require further investigation
[en] The use of gas turbines for power generation has increased in recent years and is likely to continue to increase in the medium term. This paper describes and compares several power generation cycles which have been developed to take advantage of the gas turbine's thermodynamic characteristics. Emphasis has been given to systems involving heat recovery from the gas turbine's exhaust and these include the combined, Kalina, gas/gas recuperation, steam injection, evaporation and chemical recuperation cycles. Thermodynamic and economic characteristics of the various cycles are considered in order to establish their relative importance to future power generation markets. The present dominance of the combined cycle as the preferred option for a new plant is thought likely to continue. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)
[en] Considering energy requirements for major bulk polymer, low density polyethylene (LDPE) as an energy intensive process, the potential savings are proposed. The polymerization operations need electric and thermal energy in significant amounts. Usually in an conventional system, electric energy is supplied from grid, and thermal from boilers. The efficiency of such system could be improved by using simultaneous production of electric and thermal energy (CHP), as well as waste heat recovery. Considering the polymerization data in presented article a calculation methodology for evaluating the primary energy consumption for both options i.e. CHP and separate production of heat and power is presented. As a result of proposed combined heat and power scheme (CHP) achieved saving in purchased electric energy is 17.6%. Also, the waste heat streams has been recognized as a potential energy efficiency improving option. Therefore a thermodynamic analysis for conventional and CHP is carried out. The obtained results show savings in range of 5-7.3% for conventional and 16-24% for CHP scheme