Waste Heat Utilization System Research Articles

Thermal performance simulation and numerical analysis of a fuel cell waste heat utilization system for automotive application

To recover the waste heat generated by proton exchange membrane fuel cells, an onboard fuel cell waste heat utilization system used for cockpit heating was constructed in this study. The heat transfer numerical model of the system was established, and experimental data validated the feasibility of the model. Additionally, the thermal performance of the onboard fuel cell waste heat utilization system was analyzed under various operational conditions. The results indicate that the air temperature and heat transfer coefficient of the heat exchanger are positively correlated with the thermal performance of the cockpit heating, while the radiator inlet air velocity and pump speed show a negative correlation with the system’s performance. Under other steady conditions, the stabilized temperature of the cockpit is increased by 150 % when the air temperature increases from 0 °C to 40 °C, and the cockpit temperature is reduced by 20 % when the water pump speed accelerates from 100 to 300 r/min. Furthermore, under 20 °C ambient temperatures and with an inlet air velocity of 3 m/s, water pump speed of 500 r/min, and a heat exchange coefficient of 5,000 W·m−2·K−1, the fuel cell waste heat utilization system achieves an optimal waste heat utilization efficiency of 50.8 % underrated working conditions. In summary, this study offers theoretical guidance for designing and numerically evaluating a vehicular waste heat utilization system using fuel cells.

Industrial Park low-carbon energy system planning framework: Heat pump based energy conjugation between industry and buildings

The accelerating urbanization, rapid industrial development, and excessive consumption of fossil fuels pose survival challenges such as energy depletion and environmental degradation for humanity. In the context of industrial park development, constructing a low-carbon energy system, increasing the proportion of renewable energy, enhancing energy-level matching, and utilizing heat pumps for deep waste heat recovery are effective approaches to reduce fossil energy consumption and alleviate environmental pressures. Addressing issues such as diverse thermal flows in industrial sites, complex electricity-heat-cooling energy demands, and unclear industrial-building energy coupling mechanisms, this paper proposes a two-stage planning framework, comprising the following five steps: (1) constructing a waste heat utilization system centered around heat pumps, (2) establishing a mechanism for matching heat sources, equipment, and thermal sinks, (3) establishing an energy conversion model and energy quality quantification system, (4) optimizing waste heat utilization path allocation, and (5) conducting a system energy flow analysis. Case studies demonstrate that the proposed system achieves optimized matching of multiple heat sources and sinks in industrial and building scenarios through thermal integration, meeting diverse energy demands in the park, including electricity, cooling, and multi-grade heat. After coupling with traditional steam pipeline networks, the annual total cost and annual steam power consumption decrease by 33% and 39% respectively, with a waste heat contribution rate of up to 26% and a renewable energy penetration rate of up to 25%, and a waste heat recovery system payback period of 6 years. By establishing an energy quality quantification system and conducting multi-objective optimization considering losses and economic costs, this paper provides Pareto frontier solutions, offering references for engineering proposals. The proposed networked waste heat recovery system is characterized by low energy consumption and high economic efficiency, effectively integrating the energy characteristics of industrial parks and demonstrating engineering applicability.

Flexibility improvement of a coal-fired power plant by the integration of biogas utilization and molten salt thermal storage

This study presents a novel method to enhance the flexibility of coal-fired power plant (CFPP). The suggested integrated system comprises a CFPP integrated with molten salt thermal storage system and a biogas combustion and its waste heat utilization system. Molten salt can be used to heat high-pressure feedwater and expel steam into the turbine, quickly increasing the output of CFPP. The waste heat from biogas combustion is used to charge the molten salt, and further waste heat is recovered by ORC. Comparative analyses reveal compelling advantages. The power generation can be rapidly increased by 6.8 %. A substantial 1,342.45 kW increase in power generation and an impressive 9.52 % enhancement in energy efficiency. Exergy analysis demonstrates a notable 9.52 % improvement in overall exergy efficiency. The system yields an annual net income of 10,083.51 k$, boasting an exceptionally low dynamic payback period of 1.798 years and a substantial net present value of 51,427.34 k$ over its 10-year operational span. This research enhances understanding of the use of molten salt thermal storage to increase the flexibility of CFPPs and the biogas utilization.

A robust internal model control design for low-quality waste heat power generation systems

Recovering low-quality waste heat using industrial waste heat is challenging, and the reuse technology needs to erupt. Moreover, the gas source of low-quality waste heat is relatively volatile, which makes it challenging to keep the actual working condition of the plant stable. Therefore, it is inspiring to research the robustness of root-waste heat power generation processed measurement and control system to improve the stability of the plant operation. Hence, in this paper, we have applied uncertainty theory to analyze it and formulate the uncertainty model based on the Bode diagram. We also proposed a control method based on the uncertainty model, which combines robust control and internal model control to make the roots waste heat power generation system operate stably under the effect of external disturbances and changes of internal structure or parameters in actual operation. Experimental results show that the robust internal model control method has a speed deviation of no more than 7.9 r/min compared with the PID control method. The adjustment time to track the set value does not exceed 73.1 seconds within the allowed fluctuation range. The fluctuation variance is 30.95% of that of the PID controller. The dynamic performance is better, with strong anti-interference capability and significantly improved tracking performance. It ensures the stability of the roots-type waste heat utilization system, which is essential for future intelligent grid-connected power generation.

Design and production practice of large fluidized roasting furnace

With the expansion of the scale of zinc smelting enterprises and the progress of new equipment and technology, 152 m2 fluidized roasting furnace has been developed and applied to industrial production, with a single unit capacity of 150,000 to 170,000 tons of electrolytic zinc per year. This paper analyzes and introduces an engineering example of zinc concentrate treatment by a dual-series fluidized roasting furnace. The project was designed by China ENFI Engineering Corporation and put into operation in Hunan province of China in 2018. This paper firstly describes the process flow and main equipment of the preparation system, roasting furnace system, waste heat utilization system, dust collection system from a design perspective. Then, based on production practice, it analyzes and compares aspects such as furnace operation, actual production data, major technical and economic indicators, and the characteristics and optimization of the roasting system equipment. Finally, it is concluded that the dual-series large-scale fluidized roasting furnace has stable production, good product quality, less investment, and fewer labor requirements, which brings good economic benefits to the enterprise. Its operational experience has accumulated parameters and experience for the development of larger roasting furnaces in the future.

Numerical investigation on the erosion behavior of the honeycomb H-type finned tube heat exchanger via the discrete particle method

Serious erosion problem of the heat exchanger directly affects the safe and steady operation of waste heat utilization systems. Herein, a honeycomb H-type finned tube heat exchanger for waste heat utilization of dusty flue gas was proposed, and the collision and erosion behaviors of fly ash particles were numerically predicted via the discrete particle method (DPM). Firstly, the single factor analysis was used to investigate the effects of each structural parameter on the erosion rate. Then, the range analysis of different levels of different structural parameters was carried out via orthogonal test method. Finally, the prediction correlations of erosion rates were obtained based on multiple regression method. The results shows that the oblique tube pitch and fin pitch are negatively correlated with the erosion rate, while the slit width, fin height and fin thickness are positively correlated with the erosion rate. Among them, the fin pitch has the most significant impact on the erosion rate, while the effect of oblique tube pitch is the least. The optimized case (A4B2C3D1E4) was obtained by orthogonal experimental design. Compared with the baseline case, the maximum erosion rate of the five observation points in the optimized case decreases by the average of 33.74% with the maximum reduction of 36.32%, while the average erosion rate is reduced by the average of 37.57% and the maximum of 40.58%. The above results are contributed to the optimization of anti-erosion performance of high dust-containing flue gas waste heat utilization system and the development of efficient heat exchangers.

Application of performance dynamic equationin numerical simulation and optimization of waste heat utilization and storage system

In order to improve the current situation of double energy loss in waste heat recovery and utilization, according to the factors such as phase change temperature, thermal conductivity, phase change latent heat, economy, and safety of thermal storage materials, 70# phase change thermal storage balls produced by XX company were selected as phase change thermal storage materials, and differential scanning calorimetry was used to test and analyze them, and the melting point, freezing point and phase change latent heat value of PCM were obtained, provide data reference for simulation in the following text. The shell and tube heat exchanger is selected as the core component of the mobile heat storage system, and its heat storage and release processes are simulated using FLUENT software. The results show that when the heat transfer equipment is charged for 7 hours, almost all of the inner-heat exchangers have completed the heat supply, and only the phase change products at both sides and bottom of the heat supply have ?dead zone?, which is the major effect of heat storage. In order to improve the heat storage and release rate and break the ?bottleneck? of heat storage, the heat transfer was strengthened by changing the diameter size, arrangement, and adding fins of the heat exchange tube. The effects of straight fins, T-shaped fins, as well as the number, height, thickness, and width of fins on the heat storage performance were explored. The results indicate that, adding fins cannot only improve heat transfer efficiency, but also inhibit natural-convection. The heat storage and release time decreases to varying degrees with the increase of fin width, thickness, height, and the number of circumferential fins in a single heat exchange tube.

Design and optimization of a cold energy and waste heat utilization system for LNG-powered ships with post-combustion carbon capture

The introduction of dual-carbon targets has accelerated LNG fuel adoption on vessels and driven the advancement of carbon capture technologies. This study?s aim is a 37000-deadweight tonnage liquified natural gas dual-fuel powered ship, for which chemical absorption carbon capture is applied, utilizing flue gas and liquified natural gas to supply the process?s heat and cold energy. Then a system with efficient utilization of energy and carbon capture for the LNG dual-fuel ship is designed, coupling the waste heat onboard with transcritical CO2 and organic Rankine cycle on the principle of energy cascade utilization. The system is simulated using Aspen HYSYS and the exergy analysis is carried out for this system. Then the working fluid is optimized for the system. After that, through the genetic algorithm, the system?s operating parameters are further optimized. Additionally, the system?s economic analysis is also performed. It is shown that the scheme?s exergy efficiency reaches 39.98%, and the expected cost-recovery cycle is 4.75 years.

Study on hydro-thermal coupling heat transfer performance of flue gas-water heat exchanger

The finned tube heat exchanger is the core component of the flue gas waste heat utilization system. In order to optimize and control the heat transfer efficiency of the heat exchanger in real time under smart heating conditions, we use the entransy dissipation thermal resistance as a kernel index to assess its heat exchange performance, and Trnsys simulation software is employed to figure out the influence of heat exchanger operating parameters (flue gas inlet velocity) and fin structure parameters (fin height, fin pitch) on heat exchanger heat transfer characteristics. The results show that in a reasonable range, increasing the flue gas inlet velocity can decrease the irreversible loss of heat transfer, obviously improving the heat transfer effect. The pitch and height of the fin also have a large impact on the performance of heat transfer. To significantly promote the performance of the heat exchanger, it is useful to reduce the pitch of the fin and increase the fin height within a reasonable range.

Retracted: Modeling and Optimization of Ship Waste Heat Utilization System Based on Genetic Algorithm and Sensing

Retracted: Modeling and Optimization of Ship Waste Heat Utilization System Based on Genetic Algorithm and Sensing

Performance of different HDH desalination units powered by diesel engine generator waste heat

Diesel generators used for off-grid power generation and other applications waste a significant amount of input power as heat (about 65%), contributing to global warming. To mitigate this, waste heat recovery and utilization systems can be employed. The current study, focuses on utilizing waste heat from a 2.5 MW diesel generator for freshwater production through integrated humidification dehumidification (HDH) systems. Four different HDH system layouts are investigated, considering factors such as dehumidifier and humidifier effectiveness, temperature differentials, mass flowrate ratio, and ambient temperature. The aim is to analyze and optimize the system's pure water productivity, recovery ratio, specific entropy generation, and gained output ratio. The results show that the layout featuring an air heated – air heated cycle (AH-AH) performs the best, with the highest productivity and gained output ratio of 234.48 m3/day and 3.01, respectively. On the other hand, the water heated – water heated cycle (WH-WH) layout exhibits lower performance. The study demonstrates the potential to recover 46–70% of the waste heat, significantly improving the diesel engine's utilization factor from 36% to 68%. The proposed system also proves cost-effective, with freshwater production costing as low as 0.62 $/m3 when utilizing waste heat, compared to 4.11 $/m3 and 13.96 $/m3 when using steam or electric heating elements. Furthermore, the integrated system helps reduce the environmental impact by minimizing waste heat discharge into the environment and thus contributes to mitigating global warming.

Thermodynamic and economic analysis of a conceptual system combining medical waste plasma gasification, SOFC, sludge gasification, supercritical CO2 cycle, and desalination

In order to improve the utilization of energy in solid waste, we propose a coupled system consisting of medical waste plasma gasification, solid oxide fuel cell (SOFC), sewage sludge gasification (SSG), supercritical carbon dioxide cycle (S–CO2) and multi-stage flash (MSF) desalination. The medical waste is plasma gasification and purified to produce clean syngas, which is used by the SOFC to generate electricity. the exhaust from the SOFC is mixed with crude gas from the sludge gasification to fully combust and release chemical energy while increasing the exhaust temperature. Finally, the high-temperature energy enters the waste heat utilization system consisting of S–CO2 and seawater desalination to be fully utilized. A thermodynamic and economic analysis of the proposed system shows that the hybrid system has a net power generation efficiency of 41.66%, an energy utilization efficiency of 64.95%, and an exergy efficiency of 41.25%. The plasma gasifier and SOFC are the main sources of exergy loss, accounting for 62.45% of the total destroyed exergy. The DPP of the project is only 4.4 years over a 20-year operating cycle, with an NPV of 117,652.81k$. This study demonstrates the advantages and benefits of the project in terms of solid waste resource utilization.

Використання термоакустичних технологій в суднових гібридних енергетичних установках з паливними комірками

Recently, hybrid power plants have gained significant popularity in marine energy systems. These power plants, in addition to traditional thermal engines, include electrochemical power generation systems based on fuel cells. Hybrid marine power plants represent a relatively new technical solution for the maritime fleet, driven by strict environmental emission regulations imposed by international organizations. These regulations primarily target greenhouse gas (GHG) emissions, such as carbon oxides, methane, nitrogen oxides, and other compounds. An analysis of the current state of marine energy and its development trends concludes that the problem lies in the working processes of thermal engines, which are based on fuel combustion. Achieving ecological cleanliness in maritime transport is possible by transitioning to new principles of mechanical energy production that do not rely on chemical fuel combustion. Fuel cells, which generate electricity through electrochemical processes, have the potential to solve this problem. However, the implementation of such electrochemical generators requires a systematic approach to the development of schematic solutions capable of achieving a synergistic effect. The subject of the research is the regularities and parameters of energy exchange processes in hybrid power plants. This study focuses on hybrid power plants with electrochemical generators based on proton exchange membrane fuel cells (PEM FC). The effective operation of hybrid power plants involves the utilization of waste heat from ship equipment. PEM FC is the most widely used type of fuel cell in energy and transportation sectors. The operating temperatures of PEM FCs, depending on their type, range from 60 to 80°C or 120 to 200°C, which poses a challenge for the development of efficient waste heat utilization systems. The aim of the research is to develop waste heat utilization schemes for hybrid power plants with PEM FCs using thermoacoustic heat engines. The study establishes that electrochemical generators can be integrated into the thermal system of modern power plants, and the application of thermoacoustic heat engines expands the potential of waste heat utilization systems. Low-temperature thermoacoustic engines have the capability to convert waste heat generated by PEM FC systems into mechanical work, thereby increasing the overall efficiency of hybrid power plants by 8 to 15%.

Study of Power Generation System Utilizing Waste Heat from Marine Engine - Evaluating Effectiveness of HFO-1234yf

In this study, cycle calculations were performed to investigate the characteristics of cycle thermal efficiency and turbine output in a power generation system using waste heat from a marine engine with HFO-1234yf as a working fluid.

Study on flue gas waste heat utilization system optimization of a new 1000MW unit

In this paper, the flue gas waste heat utilization system in a new 1000MW unit was as the research object, and the numerical simulations on the flue flow field and resistance characteristics of the low-temperature economizer for four operating conditions without guiding device or with three kind guiding devices was carried out by computational fluid dynamics software, and the correctness of the numerical simulation result was verified by the guaranteed value of the low-temperature economizer manufacturer. The results show that: The simulation result was basically consistent with the guaranteed value of the low-temperature economizer manufacturer, which was shown the correctness of the simulation calculation; the flue gas flow of low-temperature economizer without guiding device was unevenly distributed, with high-speed area and ash prone area; the additional guiding devices can reduce the inlet deflection angle of the low-temperature economizer, which can effectively reduce the speed deviation and improve the flow field distribution; The effect of flow equalization and resistance characteristics of the guiding devices first decreases and then increases with the number of guiding devices; The unreasonable selection of the number and position of the guiding devices will cause the flue gas to rush on the flue and cause the risk of flue vibration. In order to promote the realization of the transformation purpose, the improvement effect of the guiding devices should be simulated and calculated before the transformation.

Thermal economy analysis of flue gas waste heat utilization system of 1000MW secondary reheat unit

Deep utilization of flue gas waste heat is an important means to ameliorate the power generation productivity of coal-fired units. Aiming at the waste heat cascade utilization system which is composed of “air preheater bypass + two-stage low-temperature coal economizer + thermal primary air temperature regulating device” proposed in a certain project, using the energy balance method and the equivalent enthalpy drop method, the mathematical model of the impact of waste heat utilization devices at all levels on the unit economy is established from the boiler efficiency and steam engine heat rate. Combined with the rated operation data of the unit, the thermal economy of the system is analyzed. The results show that the bypass of the air preheater and the temperature regulating device of the hot primary air can effectively improve the utilization efficiency of the waste heat of the flue gas at the tail of the boiler, the coal consumption of power supply can be reduced by 3.47 g/kWh under rated working conditions.

General performance evaluation method of the heat aided liquid air energy storge system with waste heat utilization

As a large-scale energy storage technology, liquid air energy storge (LAES) system is considered as a promising route to solve the instability of renewable energy. The heat aided LAES system with waste heat utilization (WHU) has been widely concerned for the high electrical efficiency. However, there is no unified theoretical evaluation method for such systems. In this study, the WHU-LAES systems are generalized and unified, and a comprehensive evaluation factor (efficiency improving ability) is proposed. The specific influence modes of the added heat energy on the WHU-LAES system are analyzed: the “allocation effect” shows the heat energy redistribution in the air expansion (AE) subsystem and the follower waste heat utilization system due to the heat integration in the AE subsystem; the “gain effect” is brought by the simultaneous heat integration of the “power increase” subsystems and “consumption reduction” subsystems; the “superposition effect” is revealed and shows the efficiency improving ability is comprehensively determined by the direct benefit, the explicit influence, the “allocation effect” and the “gain effect”. In the end, the efficiency improving ability is applied to the supplementary heat characteristic analysis and the comprehensive evaluation of 8 cases of WHU-LAES systems, which proves the effectiveness of the comprehensive evaluation factor.

Can green hydrogen and waste heat utilization improve energy conservation and emission reduction of coal-based cogeneration processes?

Power-to-gas offers a new path for carbon emission reduction by integrating renewable energy hydrogen with traditional chemical process. However, its application is limited by the product fluctuation and high cost of green hydrogen. To further improve the level of energy conservation and emission reduction, this research explored the novel integration process of large-scale green hydrogen system and coal-based cogeneration process. The green hydrogen with a low fluctuation was obtained from the wind-solar coupled power equipped with conservative energy storage system. The results showed that the carbon emission was significantly reduced by 9.2%, while the total operating cost was increased by 18.7%. To alleviate the high operating cost caused by green hydrogen, various waste heat utilization systems were introduced to decrease the utilities consumption. It was found that the total site waste heat utilization was capable of further reducing carbon emission by 13.3%, and the increase in total operating cost can be controlled within 15.3%. Economic analysis proved that the expensive cost could be saved by lower hydrogen usage or hydrogen cost. By incorporating waste heat utilization, the cost increase could be as low as 6.0% and 4.8% under 50% green hydrogen flowrate or 40% energy storage system. With the progress of renewable energy hydrogen production and waste heat utilization technology, the proposed integration process will be more environmentally friendly and economically feasible in the future.

System Performance and Pollutant Emissions of Micro Gas Turbine Combined Cycle in Variable Fuel Type Cases

This study focuses on an investigation of the operating performance and pollutant emission characteristics of a micro gas turbine combined cycle using biomass gas, replacing natural gas. The models of both recuperative cycle micro gas turbines with a waste heat utilization system and a micro gas-steam turbine combined cycle system are established. When the gas turbine works at 100 kW and the same types of fuel are burnt, the recuperative cycle system consumes less fuel than the gas-steam combined cycle system. The electric efficiency of the recuperative cycle system can reach more than 29%, which is higher than 24% of the gas-steam combined system. The combined cycle thermal efficiency of the recuperative system is as high as 66%, with 36% waste heat utilization efficiency. The electrical efficiency of the recuperative cycle system in the biomass gas case decreases, while that of the gas-steam combined cycle system undergoes little change. When the gas turbine power output increases from 50 kW to 100 kW, the electrical efficiency and combined cycle thermal efficiency increases, but the thermal efficiency of waste heat utilization of recuperative cycle decreases, the NOX and SO2 emissions gradually rise. Under the same working conditions, the NOX emissions of the recuperative cycle system are greater than that of the steam-gas combined cycle system.

Numerical Simulation Study on Water Distribution for Waste Heat Utilization System with Jacketed Coke Oven Riser

Numerical Simulation Study on Water Distribution for Waste Heat Utilization System with Jacketed Coke Oven Riser