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In this research, a combination of passive and active heat transfer enhancements are used synergistically to assist in the increase of absorbed heat from a channel by roughened and fluctuating walls. To this end, the upper wall is artificially roughened and a fluctuating segment is added to the lower wall. Flow regime is considered to be laminar and Reynolds number is 1000 at the entrance of the channel. Combinations of various roughness geometries and fluctuations are studied. It was found that due the increase of the fluid kinetic energy and its interaction with roughened surface and elastic segment, heat transfer rate is amplified. To investigate the overall efficiency of the system, Nusselt number and friction factor are calculated and a maximum value of 37.5% increase in average Nusselt number of the midsection where elastic wall is placed has been reached by flexible plate displacement. A maximum Nusselt number increase of 167% has been observed when the elastic plate reaches its peak value. [ABSTRACT FROM AUTHOR]

Iron furnace gases, a byproduct of the steel and iron industries, have been the subject of research on employing them to power some of the factory's internal needs. The rise in fuel costs and focus on energy system sustainability have created distinct frameworks for heat loss sources and low-value fuels. In this study, iron furnace gas produced in steel and iron factories has been used to produce additional power to provide part of the domestic power consumption of these factories. The supercritical carbon dioxide cycle has been used to generate power. The results show that at the optimal point, the system has emissions of 0.52 and a net power output of 22100 kWh. Also, the system's efficiency is 38.56% and carbon dioxide emission is 0.510 tons/MWh. Also, by increasing the exhaust gas temperature by 150 degrees, it is clear that 2 MW of recycled heat can be obtained. Also, in this regard, the output work of the turbine has increased by 0.8 kW and increases the efficiency of the whole cycle by 31.5% to 37%. [ABSTRACT FROM AUTHOR]

Solar power plants have received much attention in recent years due to the use of renewable energy sources, no production of polluting gases, high concentration ratio, and proper thermal efficiency. But solar radiation's absence at night prevents the uniform and continuous production of electricity. Also, the challenge of the ever-increasing accumulation of municipal waste has caused the waste fuel-based power plants to attract the attention of many industrialized and developing countries. In the present research, a practical solution is proposed to solve the challenge of not producing electricity in solar tower power plants during the night by using waste as the input fuel of the power plant. The results obtained from the case study of the investigated cogeneration system show that the electric powers produced by the subsystems of the air Brayton cycle, the reheat Rankine cycle, and the organic Rankine cycle are equal to 4502.6 KW, 2640.3 KW, and 118 KW, respectively. The central receiver of the solar tower has the highest rate of irreversibility, accounting for 34% of the total exergy destruction rate. Based on the parametric study results, the irreversibility of the entire cogeneration system has a direct relationship with the inlet temperature of the turbine. Increasing the moisture of the waste also leads to a decrease in the temperature and percentage of syngas produced, and causes a decrease in the overall performance of the system. The net power of the cogeneration system increases first and then decreases with the increase in the temperature of the gasification process. [ABSTRACT FROM AUTHOR]

This study has suitably modified the existing heat transfer and pressure drop correction factors of the modified Bell–Delaware method used for heat exchangers with segmental baffles, taking into consideration the helical baffle geometry. These correction factors are presented in parametric formulas based on the Taborek presented procedure for segmental baffles. These formulas are functions of the geometrical and physical parameters of discontinuous helical baffles. In addition, the parametric formulas are presented graphically based on the Stehlik method. The correction design method proposed by Stehlik for the helical baffle is presented in detail and a theoretical model for shell-side heat transfer and pressure drop is developed. In general, the results show that the present model matches more closely with the graphically proposed correction factors of Stehlik. In order to calculate the shell-side heat transfer coefficient and pressure drop using the present method, a computational code has been developed by the authors. In addition, in order to examine the validity, the results of the code for a case study are compared with the results obtained from EXPRESS software and experimental formulas presented by Zhang. The results of comparison show that the proposed method is accurate and can be used by designers confidently. [ABSTRACT FROM PUBLISHER]