Search Results (73)

The utilization of thermoelectric systems within internal combustion engines has emerged as a promising approach to recuperate a portion of the energy dissipated through exhaust gases. The objective of this study is twofold: firstly, to assess the heat recovery potential of a thermoelectric generator integrated into a diesel engine, and secondly, to elucidate the impact of varying operating conditions on the efficiency of heat recovery. For this purpose, the thermoelectric generator was mounted onto the exhaust pipe of a single-cylinder diesel engine featuring a common-rail fuel injection system with pilot injection and a displacement volume of 1.12 L. The calculations were conducted under 100% engine load at 1500 RPM engine speed and three different injection timing settings (−2, STD, and +2 °CA). The optimum heat recovery efficiency was determined to be 5.02%, which was achieved under the following conditions: B50 fuel, −2 °CA injection timing, 1500 RPM engine speed, and 100% engine load. Full article

Supercritical carbon dioxide (SC-CO₂) power cycles offer a promising solution for offshore platforms’ gas turbine waste heat recovery due to their compact design and high thermal efficiency. This study proposes a novel parallel-preheating recuperated Brayton cycle (PBC) using SC-CO₂ for waste heat recovery on offshore gas turbines. An integrated energy, exergy, and economic (3E) model was developed and showed good predictive accuracy (deviations < 3%). The comparative analysis indicates that the PBC significantly outperforms the simple recuperated Brayton cycle (SBC). Under 100% load conditions, the PBC achieves a net power output of 4.55 MW, while the SBC reaches 3.28 MW, representing a power output increase of approximately 27.9%. In terms of thermal efficiency, the PBC reaches 36.7%, compared to 21.5% for the SBC, marking an improvement of about 41.4%. Additionally, the electricity generation cost of the PBC is 0.391 CNY/kWh, whereas that of the SBC is 0.43 CNY/kWh, corresponding to a cost reduction of approximately 21.23%. Even at 30% gas turbine load, the PBC maintains high thermoelectric and exergy efficiencies of 30.54% and 35.43%, respectively, despite a 50.8% reduction in net power from full load. The results demonstrate that the integrated preheater effectively recovers residual flue gas heat, enhancing overall performance. To meet the spatial constraints of offshore platforms, we maintained a pinch-point temperature difference of approximately 20 K in both the preheater and heater by adjusting the flow split ratio. This approach ensures a compact system layout while balancing cycle thermal efficiency with economic viability. This study offers valuable insights into the PBC’s variable-load performance and provides theoretical guidance for its practical optimization in engineering applications. Full article

This article describes the implemented technological solution of utilizing waste heat by upgrading the potato protein drying line and using energy recuperation in the drying plant. In this article, the technological sequence of the potato starch and potato protein production plant was analyzed and the identification of possible solutions that lead to a reduction in energy demand was described. The method of analyzing the processing data is based on existing models describing the flow of mass and energy fluxes. The authors did not seek new mathematical descriptions of the physicochemical phenomena occurring during the drying processes, and only modification of the technological line based on the current state of knowledge in process engineering has been proposed. The full heat recovery of the production line was applied, and the exhaust air after drying and the heat from the decanter leachate after centrifugation of the coagulated potato protein, from two energy-coupled starch dryers, were used as the source of recovered heat energy. Temperature measurements were taken at key process nodes, and the energy effects were estimated after the process line upgrade. The solution proposed in the article fits with circular economy, bringing notable economic and environmental benefits consisting of utilizing waste heat from technological processes in the food industry. Full article

This study examines scientific and technical solutions designed to enhance thermodynamic processes in modern aircraft turbine engines by utilizing heat exchangers. A comprehensive literature review informed the development of a conceptual design for a turbofan engine incorporating both an intercooler and a recuperator. The research included an original parametric and constrained optimization analysis conducted for two engine configurations as follows: one intended for narrow-body and the other for wide-body aircraft. The study focused on achieving the required thrust while enhancing efficiency. Results indicate that integrating heat exchangers can significantly reduce specific fuel consumption (SFC) and/or increase engine power or thrust. Moreover, the recovery of residual heat from exhaust gases through recuperation contributes to improved overall energy efficiency. The study also explores a novel cryogenic design that utilizes liquid hydrogen for cooling the intercooler, recuperator, and turbine. Although not modeled directly, this concept demonstrates the potential to increase the bypass ratio, further reduce SFC, and lower NO_x emissions. These findings highlight the promise of combined intercooling and recuperation strategies for improving both economic and environmental performance, with optimal system parameters dependent on aircraft class. The research aligns with ongoing efforts in mechanical engineering and aviation to enhance turbine engine efficiency through innovative thermal management solutions. Full article

The increasing awareness of the need for sustainable solutions to secure future energy supplies has spurred the search for innovative approaches. Energo-Efekt Sp. z o.o. has prepared a project for the green transformation of the energy system at a producer of spirits through the rectification of raw alcohol. An installation was conceptualised to develop the system to convert energy from biomass fuels into electricity and heat. The innovation of the installation is the use of an expander—a Heliex system which is the twin-screw turbine generator converting energy in the form of wet steam into electrical power integrated with pressure-reducing valve. This system captures all or part of the available steam flow and reduces the steam pressure, not only delivering steam at the same, lower pressure but also generating rotary energy that can be used to produce electricity with the power output range of 160 to 600 kWe. Currently, the company utilises natural gas as a fuel source and acquires electricity from the external grid. Implementing the system could reduce the carbon footprint associated with the production of vodka at the plant by 97%, to 102 t CO₂ annually. This reduction would account for approximately 21% of the total carbon footprint of the entire alcohol production process. The system could also be applied to other low-power systems that produce < 250 kW, making it a viable option for use in distributed energy networks, and can be used as a model solution for other distillery plants. The transformation project dedicated to Polmos Żyrardów involves a comprehensive change in both the energy source and its management. The fossil fuels used until now are being replaced with a renewable energy source in the form of biomass. The steam and electricity cogeneration system meets the rectification process’s energy demand and can supply the central heating node. Heat recovery exchangers recuperate heat from the boiler room exhaust gases and the rectification cooling process. Potentially, all of these changes lead to the company’s energy self-sufficiency and reduce its overall environmental impact with almost zero CO₂ emissions. Full article

This research considers a preliminary comparative technical evaluation of two micro-gas turbine (MGT) systems in combined heat and power (CHP) mode (100 kWe), aimed at supplying heat to a residential community of 15 average-sized buildings located in Central Europe over a year. Two systems were modelled in Ebsilon 15 software: a natural gas case (benchmark) and an ammonia-fueled case, both based on the same on-design parameters. Off-design simulations evaluated performance over variable ambient temperatures and loads. Idealized, unrecuperated cycles were adopted to isolate the thermodynamic impact of the fuel switch under complete combustion assumption. Under these assumptions, the study shows that the ammonia system produces more electrical energy and less excess heat, yielding marginally higher electrical efficiency and EUF (26.05% and 77.63%) than the natural gas system (24.59% and 77.55%), highlighting ammonia’s utilization potential in such a context. Future research should target validating ammonia combustion and emission profiles across the turbine load range, and updating the thermodynamic model with a recuperator and SCR accounting for realistic pressure losses. Full article

The conventional urea-based process for hydrazine hydrate production faces challenges including low product yield and high energy consumption. To overcome these limitations, we propose an innovative integrated approach combining jet reactor technology with membrane separation, further enhanced through heat network optimization. Through process simulation and sensitivity analysis, the following optimal distillation parameters were identified: nine theoretical stages, feed entry at the fifth stage, a reflux ratio of 0.6, and a distillate flow rate of 354 kg/h. Systematic optimization of the heat exchanger network (HEN) using pinch technology achieved substantial energy savings, reducing hot utility consumption by 66.8% (to 1317 MJ/h) and cold utility usage by 62.7% (to 1503 MJ/h). The redesigned HEN prioritized temperature-cascaded heat recovery, enabling 67% energy recuperation from exothermic reaction streams. Operational costs decreased by 12%, underscoring the economic viability of coupling process intensification with thermal integration. This work establishes a sustainable framework for hydrazine hydrate synthesis, balancing industrial feasibility with reduced environmental impact in chemical manufacturing. Full article

The combined cooling, heating, and power system is based on the principle of energy cascade utilization, which is conducive to reducing fossil energy consumption and improving the comprehensive utilization efficiency of energy. With the characteristics of a lower expansion ratio and larger recuperation of a supercritical carbon dioxide (SCO₂) power cycle, a combined cooling, heating, and power (CCHP) system is proposed. The system is based on a SCO₂ cycle and is driven by solar energy. The system is located in Qingdao and simulated by MATLAB/Simulink software (R2022b). Firstly, the thermodynamic performance of the CCHP system at the design condition is analyzed. The energy utilization efficiency of the CCHP system is 79.75%, and the exergy efficiency is 58.63%. Then, the thermodynamic, environmental, and economic performance analyses of the system under variable conditions are carried out. Finally, the solar multiple is optimized. The results show that the minimum levelized cost of electricity is 10.4 ¢/(kW·h), while the solar multiple is 4.8. The annual primary energy saving rate of the CCHP system is 85.04%, and the pollutant emission reduction rate is 86.05%, compared with the reference system. Therefore, an effective way to reduce environmental pollution and improve the utilization efficiency of solar energy is provided. Full article

Fugitive methane emissions contained in the ventilation air (VAM) from underground coal mines make a significant contribution to the global methane emissions. These methane emissions have a high global warming potential (GWP) and should be mitigated to combat climate change. This study reports on a novel integrated recuperator reactor concept designed to mitigate these low-concentration methane streams using catalytic combustion. The paper analyzes the heat recovery aspects of the novel design and illustrates a computer-aided design approach to system development. Both computational and experimental methods were used in the investigation. The double-spiral counterflow design is shown to be able to eliminate methane from the flow stream with the feed at room temperature. A methodology is illustrated that can be used to determine the operating limits of the proposed recuperative reactor system. This system is suitable for use inside a mine. Full article

In the context of central solar receiver systems, the utilisation of S-CO₂ Brayton cycles as opposed to Rankine cycles confers a number of advantages, including enhanced efficiency, the requirement for less sophisticated turbomachinery, and a reduction in water consumption. A pivotal consideration in the design of such systems pertains to the thermal storage system. This work undertakes a comparative analysis of the performance of an S-CO₂ Brayton cycle utilising two distinct types of molten salts, namely solar salts and chloride salts (MgCl₂–KCl), as the heat transfer fluid on the thermal energy storage medium. The present study adopts an energetic and exergetic perspective with the objective of identifying areas of high irreversibility and proposing mechanisms to reduce them. The work is concluded with an analysis of the size of the different components. The overall energy efficiency is determined as 22.29 % and 23.76 % for solar and chloride salts, respectively. In the case of chloride salts, this efficiency is penalized by the higher losses in the solar receiver due to the higher operating temperature. The exergy analysis shows that using MgCl₂–KCl salts increases exergy destruction in the recuperators, lowering irreversibilities in other components. While the sizes of all components decrease when using chloride salts, the volume of the storage system increases. These results demonstrate that the incorporation of MgCl₂–KCl salts enhances the performance of S-CO₂ recompression cycles operating in conjunction with a central solar receiver. Full article

Research on temperature regulation is essential for ensuring thermal comfort and optimizing machine performance. Effective cooling systems are critical in industrial processes and everyday electronic devices in order to prevent overheating. Laser-modified heat exchangers can enhance heat dissipation without increasing weight, addressing the need for energy-efficient solutions in the market. The main aim of this experimental research was to establish an efficient method for altering the surface layer of AISI 316L stainless steel with laser pulses and to determine the effectiveness of the laser alterations to the surface layer in the context of intensifying the convective heat transfer. A series of laser-texturing processes was performed on the surface layer of AISI 316L steel using a Nd: YAG pulse laser. Selected samples were subjected to a series of measurements using a recuperator-type heat exchanger. Based on the measurements’ results, the heat transfer coefficients, α, obtained from the modified surfaces were determined. The results were compared with other data from the existing literature and those obtained from unmodified reference samples. The intensification of the convective heat transfer was achieved for 43% of the modifications conducted with a pulsed laser. The highest observed average increase in the heat transfer coefficient, α, was 16.53%. However, the effective intensification of the convective heat transfer, in some cases, was only observed for a certain range of temperatures or flow dynamics parameters. Full article

This study proposes an innovative system for recovering waste heat from exhaust air after a regenerative thermal oxidiser process, integrating a Carnot battery and photovoltaic (PV) modules. The Carnot battery incorporates an organic Rankine cycle (ORC) with a recuperator, thermal energy storage (TES), and heat pump. Waste heat is initially captured in TES, with additional energy extracted by a heat pump to increase the temperature of a secondary fluid, effectively charging TES from both direct and indirect sources. The stored heat enables electricity generation via ORC. The result of this study shows a heat pump COP between 2.55 and 2.87, the efficiency of ORC ranging from 0.125 to 0.155, and the power-to-power of the Carnot battery between 0.36 and 0.40. Moreover, PV generates 1.35 GWh annually, primarily powering the heat pump and ORC system pump. The proposed system shows a total annual net generation of 4.30 GWh. Economic evaluation across four configurations demonstrates favourable outcomes, with a return on investment between 25% and 160%. The economic evaluation examined configurations with and without the PV system and recuperation process in the ORC. Results indicate that incorporating the PV system and recuperator significantly increases power output, offering a highly viable and sustainable energy solution. Full article

This article analyses the possibility of using hydrogen as fuel in furnaces used in the metallurgical industry. The research was conducted for a selected continuous furnace. For this purpose, based on actual measurements, a heat balance of the furnace was prepared to determine its energy indicators. These values were used to verify the developed numerical model in IPSEpro 7.0 software. Numerical calculations were performed for three variants: pure natural gas; 30% hydrogen, 70% natural gas; and 100% hydrogen. The determined values of gas and combustion air streams allowed for achieving the assumed charge temperature in the heating technology. Calculations of the impact of the excess combustion air ratio on process parameters were also carried out. It was found that no changes are required in the exhaust gas removal system, but verification of the fan supplying air to cool the exhaust gases before the recuperator is necessary. The amount of hydrogen required to fuel the continuous furnace also increases significantly (nearly threefold), which may also affect operating costs. At the same time, the emission of carbon dioxide into the atmosphere is completely reduced, which may be an important criterion when considering modernization options for heating furnaces in the metallurgical industry. Full article

The Supercritical Carbon Dioxide Brayton Cycle (sCO₂-BC) is a highly efficient and eco-friendly alternative for marine propulsion. The adoption of sCO₂-BC aligns with the industry’s focus on sustainability and can help meet emission regulations. In this context, the current study introduces a cascade system that harnesses the exhaust gases from a marine Gas Turbine Propulsion System to serve as a heat source for a bottoming Supercritical Carbon Dioxide Brayton Cycle (sCO₂-BC), which facilitates an onboard heat recovery system. The investigation primarily focuses on the recompression cycle layouts of the sCO₂-BC. To assess the performance of the bottoming cycle layouts and the overall cascade system, various parameters of the recompression sCO₂-BC are analyzed. These parameters include the mass flow rate of CO₂ in the bottoming cycle and the effectiveness of both the low-temperature recuperator (LTR) and the high-temperature recuperator (HTR). For conducting the cycle simulations, two codes are built and integrated; this first code models the thermodynamic cycle, while the second code models the recuperators. The research shows that incorporating the sCO₂ Brayton Cycle as a bottoming cycle has the potential to greatly improve the efficiency of the entire system, increasing it from 54% to 59%. Therefore, it provides a useful framework for advancing energy-efficient gas turbine systems and future research. Full article

Due to increasing emissions and global warming, in parallel with the increasing world population and energy needs, IMO has introduced severe rules for ships. Energy efficiency on ships can be achieved using the organic and inorganic Rankine cycle (RC) driven by exhaust heat from marine diesel engines. In this study, toluene, R600, isopentane, and n-hexane as dry fluids; R717 and R718 as wet fluids; and R123, R142b, R600a, R245fa, and R141b as isentropic fluids are selected as the working fluid because they are commonly used refrigerants, with favorable thermal properties, zero ODP, low GWP and are good contenders for this application. The cycle and exergy efficiencies, net power, and irreversibility of marine diesel engine exhaust-driven simple RC and RC with a recuperator are calculated. For dry fluids, the most efficient fluid at low turbine inlet temperatures is n-hexane at 39.75%, while at high turbine inlet temperatures, it is toluene at 41.20%. For isentropic fluids, the most efficient fluid at low turbine inlet temperatures is R123 with 23%, while at high turbine inlet temperatures it is R141b with 23%. As an inorganic fluid, R718 is one of the most suitable working fluids at high turbine inlet temperatures of 300 °C onboard ships with a safety group classification of A1, ODP of 0, and GWP100 of 0, with a cycle efficiency of 33%. This study contributes to significant improvements in fuel efficiency and reductions in greenhouse gas emissions, leading to more sustainable and cost-effective maritime operations. Full article