Exergy Destruction In Various Components Research Articles

Energy and exergy analysis of solar stills with micro/nano particles: A comparative study

In this paper, a theoretical comparative study between modified solar stills (MSSs) and classical solar still (CSS) was carried out, based on the productivity and the thermal properties. The MSSs contain brackish water mixed with either graphite or copper oxide (CuO) micro/nano particles. Cost estimations of solar still desalination by using micro/nano particles was estimated. exergy destruction in various components of the solar still (SS) were calculated, analyzed and discussed. The exergy loss during the day time comprises the exergy destruction in the main components of the SS like basin plate, brine water, glazier plate and insulation material. The hourly convective, evaporative and radiative heat transfer coefficients (HTCs) with and without micro/nano particles were determined. The exergy destruction in various components of the SS have been analyzed and a solution was suggested. Results revealed that the exergy of evaporation, energy efficiency and exergy efficiency of MSSs were higher than that of the classical one. The daytime energy efficiencies of MSSs with graphite and CuO were 41.18% and 38.61%, respectively, but for the CSS was only 29.17%. The diurnal productivity of the MSSs was increased by 41.18% and 32.35% for graphite and CuO, respectively, compared with CSS. Moreover, the diurnal exergy efficiencies of MSSs were 4.32% and 3.78% for graphite and CuO respectively, while exergy efficiency for CSS was 2.63%. Furthermore, the costs of water production were found to be approximately 0.20, 0.21 and 0.24 RMB/L (1 RMB = 0.15 US $) when using MSS with CuO, MSS with graphite and CSS, respectively.

Performance analysis of combined cycle power plant

Combined cycle power plants (CCPPs) are in operation with diverse thermodynamic cycle configurations. Assortment of thermodynamic cycle for scrupulous locality is dependent on the type of fuel available and different utilities obtained from the plant. In the present paper, seven of the practically applicable configurations of CCPP are taken into consideration. Exergetic and energetic analysis of each component of the seven configurations is conducted with the help of computer programming tool, i.e., engineering equation solver (EES) at different pressure ratios. For Case 7, the effects of pressure ratio, turbine inlet temperature and ambient relative humidity on the first and second law is studied. The thermodynamics analysis indicates that the exergy destruction in various components of the combined cycle is significantly affected by the overall pressure ratio, turbine inlet temperature and pressure loss in air filter and less affected by the ambient relative humidity.

Energy and exergy analysis of a super critical thermal power plant at various load conditions under constant and pure sliding pressure operation

The objective of this paper is to perform an energetic and exergetic analysis on a 660 MWe coal fired supercritical thermal power plant at 100%, 80% and 60% of normal continuous rating (NCR) conditions under constant pressure as well as pure sliding pressure operation and to highlight the benefits of the latter over the former. The energetic input, energetic output, exergetic input, exergetic output, energetic and exergetic efficiencies of various components of the supercritical thermal power plant are estimated at 660 MWe, 528 MWe and 396 MWe load under both constant pressure as well as pure sliding pressure operation. Also the energy losses and exergy destruction in various components of a power plant i.e. Boiler, high pressure turbine (HPT), intermediate pressure turbine (IPT), low pressure turbine (LPT), condenser, gland steam coolers, condensate extraction pumps, low pressure heaters (LPH), drip pumps (DP), deaerator (D), boiler feed pump (BFP) and high pressure heaters (HPH) have been calculated. The results have shown that the boiler has the maximum rate of exergy destruction than any other component in the power plant. After the boiler, turbine has the maximum rate of exergy destruction than any other component of the power plant. The study reveals that there is a significant reduction in the rate of exergy destruction at part load conditions for the turbine in case of sliding pressure operation in comparison to constant pressure operation. The rate of exergy destruction in the turbine at 100%, 80% and 60% of NCR conditions is 49.16 MW/43.22 MW/43.92 MW for constant pressure operation and 47.66 MW/37.88 MW/28.94 MW respectively. The BFP power input reduces by 9.39%, 21.52% and 42.5% respectively at 100%, 80% and 60% of NCR conditions if the unit runs in sliding pressure mode compared to constant pressure mode.

Exergy analysis of the regenerative gas turbine cycle using absorption inlet cooling and evaporative aftercooling

AbstractThis paper provides an exergy analysis to investigate the effects of pressure ratio, turbine inlet temperature, compressor inlet temperature and ambient relative humidity on the thermodynamic performance of a regenerative gas turbine cycle using absorption inlet cooling and evaporative aftercooling. Combined first and second law analysis indicates that the exergy destruction in various components of the gas turbine cycle is significantly affected by compressor pressure ratio and turbine inlet temperature, and slightly varies with the compressor inlet temperature and ambient relative humidity. It also indicates that the maximum exergy destroyed in the combustion chamber; which represents over 60% of the total exergy destruction in the overall system. The net work output, first law efficiency, and second law efficiency of the cycle significantly varies with the change in the pressure ratio, turbine inlet temperature, compressor inlet temperature and ambient relative humidity.

Exergy analysis of gas turbine trigeneration system for combined production of power heat and refrigeration

A conceptual trigeneration system is proposed based on the conventional gas turbine cycle for the high temperature heat addition while adopting the heat recovery steam generator for process heat and vapor absorption refrigeration for the cold production. Combined first and second law approach is applied and computational analysis is performed to investigate the effects of overall pressure ratio, turbine inlet temperature, pressure drop in combustor and heat recovery steam generator, and evaporator temperature on the exergy destruction in each component, first law efficiency, electrical to thermal energy ratio, and second law efficiency of the system. Thermodynamic analysis indicates that exergy destruction in combustion chamber and HRSG is significantly affected by the pressure ratio and turbine inlet temperature, and not at all affected by pressure drop and evaporator temperature. The process heat pressure and evaporator temperature causes significant exergy destruction in various components of vapor absorption refrigeration cycle and HRSG. It also indicates that maximum exergy is destroyed during the combustion and steam generation process; which represents over 80% of the total exergy destruction in the overall system. The first law efficiency, electrical to thermal energy ratio and second law efficiency of the trigeneration, cogeneration, and gas turbine cycle significantly varies with the change in overall pressure ratio and turbine inlet temperature, but the change in pressure drop, process heat pressure, and evaporator temperature shows small variations in these parameters. Decision makers should find the methodology contained in this paper useful in the comparison and selection of advanced heat recovery systems.

Combined First and Second-Law Analysis of Gas Turbine Cogeneration System With Inlet Air Cooling and Evaporative Aftercooling of the Compressor Discharge

A conceptual gas turbine based cogeneration cycle with compressor inlet air cooling and evaporative aftercooling of the compressor discharge is proposed to increase the cycle performance significantly and render it practically insensitive to seasonal temperature fluctuations. Combined first and second-law approach is applied for a cogeneration system having intercooled reheat regeneration in a gas turbine as well as inlet air cooling and evaporative aftercooling of the compressor discharge. Computational analysis is performed to investigate the effects of the overall pressure ratio rp, turbine inlet temperature (TIT), and ambient relative humidity φ on the exergy destruction in each component, first-law efficiency, power-to-heat ratio, and second-law efficiency of the cycle. Thermodynamic analysis indicates that exergy destruction in various components of the cogeneration cycle is significantly affected by overall pressure ratio and turbine inlet temperature, and not at all affected by the ambient relative humidity. It also indicates that the maximum exergy is destroyed during the combustion process, which represents over 60% of the total exergy destruction in the overall system. The first-law efficiency, power-to-heat ratio, and second-law efficiency of the cycle significantly vary with the change in the overall pressure ratio and turbine inlet temperature, but the change in relative humidity shows small variations in these parameters. Results clearly show that performance evaluation based on first-law analysis alone is not adequate, and hence, more meaningful evaluation must include second-law analysis. Decision makers should find the methodology contained in this paper useful in the comparison and selection of advanced combined heat and power systems.

Thermodynamic performance assessment of an indirect intercooled reheat regenerative gas turbine cycle with inlet air cooling and evaporative aftercooling of the compressor discharge

This study provides a computational analysis to investigate the effects of cycle pressure ratio, turbine inlet temperature (TIT), and ambient relative humidity (φ) on the thermodynamic performance of an indirect intercooled reheat regenerative gas turbine cycle with indirect evaporative cooling of the inlet air and evaporative aftercooling of the compressor discharge. Combined first and second-law analysis indicates that the exergy destruction in various components of gas turbine cycles is significantly affected by compressor pressure ratio and turbine inlet temperature, and is not at all affected by ambient relative humidity. It also indicates that the maximum exergy is destroyed in the combustion chamber; which represents over 60% of the total exergy destruction in the overall system. The net work output, first-law efficiency, and the second-law efficiency of the cycle significantly varies with the change in the pressure ratio, turbine inlet temperature and ambient relative humidity. Results clearly shows that performance evaluation based on first-law analysis alone is not adequate, and hence more meaningful evaluation must include second-law analysis. Decision makers should find the methodology contained in this paper useful in the comparison and selection of gas turbine systems. Copyright © 2006 John Wiley & Sons, Ltd.