Case Studies in Thermal Engineering最新文献

{"title":"Comprehensive study on cooling effectiveness and thermoelectric conversion of a novel helium/hydrogen-based closed Brayton cooling system for a hydrogen aero-engine","authors":"Qiurui Xin ,&nbsp;Xiaohui Bai ,&nbsp;Helong Jin ,&nbsp;Chengao Duan ,&nbsp;Yuxi Li ,&nbsp;Cunliang Liu","doi":"10.1016/j.csite.2025.105741","DOIUrl":"10.1016/j.csite.2025.105741","url":null,"abstract":"<div><div>The Brayton cycle and thermoelectric generators offer significant potential for cooling hydrogen aero-engines. However, existing research on Brayton cooling schemes integrated with thermoelectric generators (TEGs) remains limited, typically relying on assumed state parameters that are challenging to obtain. This study proposes a one-dimensional method that considers the coupling relationships between the mainstream, TEGs, and coolant, thereby investigating the cooling and thermoelectric conversion processes of aero-engines under real operating conditions. Subsequently, four cooling schemes—direct cooling (DC), Brayton cooling (BC), direct thermoelectric cooling (DTC), and Brayton thermoelectric cooling (BTC)—are analyzed. Consequently, the DC provides the best cooling performance, with the highest wall temperature of hot components below 750 K. The BC generates the highest mechanical power, reaching 124.7 kW. Furthermore, the utilization of TEGs reduces the cooling efficiency but increases the total power output of the schemes. Compared to the DC, the maximum wall temperature of the DTC increases by 496.3 K, while the thermoelectric power is the greatest, reaching 116.6 kW. The maximum wall temperature of the BTC rises by 335.5 K compared to the BC, whereas its total power output is the highest, at 142.3 kW. This study guides the cooling and waste heat utilization in hydrogen aero-engines.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105741"},"PeriodicalIF":6.4,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The real driving emissions characteristics of light-duty diesel vehicle in four typical cities with varying altitudes in China","authors":"Haojie Gao ,&nbsp;Rui Wang ,&nbsp;Zhisong Wen ,&nbsp;Xin Xiong ,&nbsp;Zhuan Zheng ,&nbsp;Shengqiang Lin ,&nbsp;Hongchun Ding ,&nbsp;Wenbin Tan","doi":"10.1016/j.csite.2025.105831","DOIUrl":"10.1016/j.csite.2025.105831","url":null,"abstract":"<div><div>Real driving emissions (RDE) tests were conducted on a China VI B compliant light-duty diesel vehicle in four cities with different altitudes. The emission factors of particle number (PN), nitrogen oxides (NOx), and carbon monoxide (CO) were calculated using the carbon dioxide (CO₂) moving average window (MAW) method and compared across different altitudes and driving stages. The tests covered urban, rural, and motorway sections in these four cities. The results showed that NO_X and CO emissions were highest in urban sections. The study also analyzed the impact of altitude, traffic conditions, and exhaust temperature on emission characteristics. The results indicated that CO and NO_X emissions increased with altitude, while PN emissions showed different trends due to aftertreatment effects. In high-altitude areas, CO and PN emissions also increased with higher cylinder and exhaust temperatures. The emissions of all pollutants were significantly lower than the China VI b emission standards. We suggest further research to optimize aftertreatment systems to better control emissions and improve efficiency under varying altitudes and route conditions.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105831"},"PeriodicalIF":6.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating the influence of heterocyclic Schiff bases as a biofuel additive on combustion, performance and emissions","authors":"Beşir Dağ ,&nbsp;Selman Aydın ,&nbsp;Ramazan Şener","doi":"10.1016/j.csite.2025.105836","DOIUrl":"10.1016/j.csite.2025.105836","url":null,"abstract":"<div><div>The growing need for cleaner and more efficient energy sources has driven extensive research into biofuels and their additives to improve combustion performance and reduce emissions. This study investigates the potential impact of heterocyclic Schiff bases as biofuel additives, exploring their effects on combustion efficiency, engine performance, and emissions characteristics in compression ignition engines. The research aims to enhance fuel efficiency and reduce emissions by leveraging the unique chemical properties of Schiff bases. Heterocyclic Schiff bases, known for their diverse chemical properties, offer a novel avenue for enhancing the combustion properties of fuels. 4-Aminoantipyrine (AAP) Schiff base was synthesized as a fuel additive. The prepared AAP Schiff base was mixed homogeneously within a mixture of ethanol before being incorporated into diesel. The different blends, such as 90 % diesel +10 % ethanol (D90E10) and 90 % diesel + 10 % ethanol + 100 ppm AAP (D90E10-AAP), were prepared for the experiments. Utilizing an eddy current dynamometer, the combustion properties of fuel blends were systematically compared against diesel within a compression ignition engine operating spanning three distinct BMEP levels. Fuel additives improve the emissions and performance of the engine. In terms of cylinder pressure, knock density and mean gas temperature, it was determined that the fuel with novel additive D90E10-AAP results in improvements to diesel. The study is expected to contribute to the existing body of knowledge on this topic and provide insights into the potential applications of AAP Schiff base as a biofuel additive in the automotive industry.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105836"},"PeriodicalIF":6.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An enhanced thermal conduction model for viscous thermal interactions in circular micro-resonators supported by elastic foundations","authors":"Mohammed Alsubhi","doi":"10.1016/j.csite.2025.105846","DOIUrl":"10.1016/j.csite.2025.105846","url":null,"abstract":"<div><div>This study investigated the effects of thermoelastic coupling on the viscoelastic behavior of Kelvin-Voigt elastic circular plate resonators. The viscoelastic microsheet resonators were modeled as homogeneous, isotropic structures based on the Winkler foundation. Utilizing the modified Moore-Gibson-Thompson thermoelasticity (MGTE) model, which incorporated both limited thermomechanical diffusion and viscous effects, we solved the governing equations of the proposed system using Laplace transformation methods. Graphical representations of the results were generated using Mathematica software. The study provided detailed discussions that underscored the significant influence of viscosity, the Winkler foundation, and relaxation time on the development of more efficient and effective circular plate structures. Comparisons with previously published studies and results derived from related thermoelastic models were conducted to verify the accuracy of the findings. We found that a stiffer foundation provided stronger support, limiting the extent of deflection under applied loads while also promoting a more uniform temperature distribution in the microplate. Additionally, the viscosity coefficient has a significant impact on the behavior of flexible microplates by reducing temperature distribution, increasing deformation, and amplifying the magnitude of thermal stress. The results enable improved operational accuracy while reducing energy dissipation, making them particularly valuable for high-precision applications.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105846"},"PeriodicalIF":6.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Earth–lunar thermal effect on the temperature stability of TianQin telescope and the suppression methods","authors":"Wenbo Chang,&nbsp;Yuxiang Wang,&nbsp;Wenhai Tan,&nbsp;Guanhua Wu,&nbsp;Houyuan Chen,&nbsp;Wei Li,&nbsp;Zizheng Li,&nbsp;Fan Zhu,&nbsp;Zhu Li,&nbsp;Xuefeng Zhang,&nbsp;Shanqing Yang","doi":"10.1016/j.csite.2025.105816","DOIUrl":"10.1016/j.csite.2025.105816","url":null,"abstract":"<div><div>TianQin is a geocentric space-based gravitational wave detection mission, it will confront a more complex and variable orbital thermal environment compared to heliocentric orbit mission<em>s</em> like LISA. As one of the core payloads in TianQin, the telescope requires stringent temperature stability. Furthermore, the telescope operates as an open system directly exposed to the external environment. <em>B</em>esides the solar thermal irradiation, the earth and lunar heat irradiation exist in <em>the</em> TianQin orbit, and may enter the telescope during the observation period. Up to now, the effect of earth–lunar heat flux on the temperature stability of the TianQin telescope has not been addressed. In this article, an innovative algorithm is proposed for accelerating the Gebhart factors calculation, and the detailed evaluation from the direct earth and lunar heat flux to <em>the</em> telescope’s temperature stability <em>has</em> been accomplished. Our findings reveal that the temperature stability of <em>the</em> telescope’s secondary mirror closely approaches the level of total TianQin requirement (about 2 mK/<span><math><msqrt><mrow><mi>Hz</mi></mrow></msqrt></math></span>@0.1 mHz and 5<span><math><mi>μ</mi></math></span>K/<span><math><msqrt><mrow><mi>Hz</mi></mrow></msqrt></math></span>@2 mHz) in the absence of a baffle, especially in proximity to frequencies of the 0.1 mHz and 2 mHz. To suppress the heat flux influence, we researched the effect of the geometry and surface thermo-optical property of the baffle on the temperature stability of <em>the</em> telescope. A bunched entrance baffle is optimized by Linear Programming analysis based on the smallest laser aperture and baffle geometric size constraint and then achieved temperature stability of about 0.3 mK/<span><math><msqrt><mrow><mi>Hz</mi></mrow></msqrt></math></span> @0.1 mHz for the secondary mirror. In addition, An empirical formula derived from conic curve analysis is utilized to guide the iterative optimization of vanes. Subsequent implementation of vanes within the baffle serves to further suppress the earth and lunar heat flux disturbances, leading to an improved temperature stability of about 0.04 mK/<span><math><msqrt><mrow><mi>Hz</mi></mrow></msqrt></math></span> @0.1 mHz and 0.7 <span><math><mrow><mi>μ</mi><mi>K</mi><msqrt><mrow><mi>Hz</mi></mrow></msqrt></mrow></math></span> @2 mHz, one order of magnitude below the TianQin total requirement. The methods and results can also provide enlightenment for other similar space missions.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105816"},"PeriodicalIF":6.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation on the influencing mechanism and quantitative evaluation of stirred heat effect in high-speed mechanical seals","authors":"Xuezhong Ma ,&nbsp;Xiaoxin Xiao","doi":"10.1016/j.csite.2025.105839","DOIUrl":"10.1016/j.csite.2025.105839","url":null,"abstract":"<div><div>Stirred heat is much severe in mechanical seals under high-speed conditions, which significantly affects seal's heat transfer and dissipation characteristics. A three-dimensional thermohydrodynamic numerical model consisting of the fluid film, sealed chamber and sealing rings is developed to investigate the influencing mechanism of stirred heat by the comparative analyses of fluid flow, heat generation and transfer and evaluates its influence level by the parameterized analyses about the rotational speed, flushing flow rate, sealing pressure and sealing face structure. Firstly, in terms of cooling flow, the cold fluid flow from sealed chamber into sealing gap is impeded by the high-speed shear effect of rotor outer sidewall, and a larger vortex namely a flow dead zone is generated at the spiral groove root due to the turbulent flow regime, which significantly impede the cooling level of fluid film and sealing end faces. Secondly, in terms of heat generation, because of the high-speed shear effect of rotor, a much larger effective viscosity, radial velocity gradient, turbulence intensity and turbulence dissipation rate are generated by the turbulent flow in sealed chamber, which are responsible for the significant stirred heat. Finally, in terms of heat transfer, the temperature difference between the sealing rings and sealing chamber fluid is narrowed by the stirred heat, suppressing the convective heat transfer level. The above phenomena lead to an increase in the overall and sealing face temperature rises, and a deterioration of the sealing performance. The rotational speed has the most significant impact on the stirred heat. At the most severe, temperature rise of stirred heat for seal is up to 34 %, the decrease of load-carrying capacity is up to 17 %. Increasing flushing flow rate has a positive effect on the dissipation of stirred heat. The sealing face structure hardly affects the stirred heat generation and transfer.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105839"},"PeriodicalIF":6.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143257817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic characteristics of a two-phase mechanically pumped cooling loop for avionics","authors":"Shaohuan Qi,&nbsp;Zhaohao Xu,&nbsp;Jiale Wang,&nbsp;Yu Xu","doi":"10.1016/j.csite.2025.105830","DOIUrl":"10.1016/j.csite.2025.105830","url":null,"abstract":"<div><div>Given the varying flight conditions and mission requirements that affect aircraft cold sources and heat loads, it is crucial to investigate the dynamic behavior of a two-phase mechanically pumped cooling loop (MPCL) for avionics. Here, an experimental MPCL system charged with R134a was established, and its performance was evaluated under cold source temperatures of 16–46 °C and heat fluxes of 50–150 kW/m². When the cold source temperature varies, the heating wall temperature and pressure drop are 33.7–60.0 °C and 78.0−119.6 kPa for unadjustable pump mode, and they are 34.1–60.0 °C and 59.6−124.6 kPa for adjustable pump mode. When heat load starts, the heating wall temperature and pressure drop rapid rise, and then stabilize. For low temperature start-up, the heating wall temperature is lower, but the pressure drop is usually higher compared to high temperature start-up. When heat load jumps, heating wall temperature and pressure drop rise and then stabilize regardless of pump mode. The pump mode has a minor impact on the heating wall temperature, but the pressure drop is greater in adjustable mode than in unadjustable mode. The findings indicate the designed MPCL can always tend to be stable when the cold source or heat load change.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105830"},"PeriodicalIF":6.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143257811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental study on the solar heating and night sky radiative cooling properties of biochar","authors":"Haiwei Xie,&nbsp;Jianyun Luo,&nbsp;Yan Zhang,&nbsp;Jiajuan Yan,&nbsp;Yuhao Qing","doi":"10.1016/j.csite.2025.105832","DOIUrl":"10.1016/j.csite.2025.105832","url":null,"abstract":"<div><div>Daytime solar heating and nighttime radiative cooling are of great significance to global energy conservation and carbon neutrality because of their low cost, zero energy consumption and environmentally friendly characteristics. In this study, a new radiation material, walnut shell biochar (WBS), was proposed and its performance in daytime solar heating and nighttime radiative cooling was studied. The experimental results indicate that WBS exhibits a maximum absorption rate of 95.93 % within the solar radiation spectrum, along with an average emissivity of 92.45 % in the atmospheric transmission window. When utilizing a low-density polyethylene film cover plate with a thickness of 10 μm and employing 50 mesh of WBS, the combined effect of daytime solar heating and nighttime radiative cooling is optimized. Under conditions where the solar radiation intensity reaches 750 W/m², the surface temperature of WBS is observed to be 63.3 °C higher than that of the ambient temperature. Conversely, on clear nights, this surface temperature drops to be 15.5 °C lower than that of its surroundings. This research provides valuable technical support for developing integrated processes that leverage both daytime heating and nighttime radiative cooling.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105832"},"PeriodicalIF":6.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermodynamic and economic analysis, optimization of SOFC/GT/SCO2/ORC hybrid power systems for methanol reforming-powered ships with carbon capture","authors":"Shouguang Yao ,&nbsp;Xuan Yan ,&nbsp;Minjie Xia ,&nbsp;Chuang Wang ,&nbsp;Shaofan Wang","doi":"10.1016/j.csite.2025.105840","DOIUrl":"10.1016/j.csite.2025.105840","url":null,"abstract":"<div><div>To realize the efficient use of energy and reduction of emissions of the power system of ocean-going vessels, a 25,000-ton chemical ship is used as the subject of this study. A hybrid power system containing carbon capture based on methanol external reforming of solid oxide fuel cell coupled with gas turbine is proposed, further to achieve efficient energy use and reduce carbon emissions, the power system combines a supercritical CO₂ cycle with an organic Rankine cycle in order to optimize the utilization of waste heat, and chemical absorption method for carbon capture. The proposed novel power system is analyzed for the impact of important factors of each system on performance of the system, and thermodynamic and economic analyses and evaluations are carried out. Ultimately, a genetic algorithm-based approach was employed to optimize the system's performance through multi-objective optimization, aiming for the best possible outcome. The optimized outcome shows that the system's net output power has reached 4743.81 kW, which fully satisfies the power requirements of the target vessel. Additionally, it achieves a carbon capture rate of 81.52 %, an energy efficiency of 60.56 %, and the cost of electricity production is 0.08727 $/kWh. The system realizes excellent thermodynamic performance and economy.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"67 ","pages":"Article 105840"},"PeriodicalIF":6.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143257810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A multi-criteria optimization for a radial heat sink with semicircular fins based on the design of experiments approach","authors":"Yousif Hashim Hussein ,&nbsp;Tahseen Ahmad Tahseen ,&nbsp;Abdulrazzak Akroot ,&nbsp;M.A.H. Mithu ,&nbsp;Ammar M. Abdulateef","doi":"10.1016/j.csite.2024.105727","DOIUrl":"10.1016/j.csite.2024.105727","url":null,"abstract":"<div><div>Radial fins play a crucial role in enhancing energy efficiency and supporting sustainable industrial practices by optimizing heat transfer, aligning with the Sustainable Development Goals (SDGs). Addressing the need for high-efficiency systems to reduce greenhouse gas emissions, this study highlights the importance of optimizing factors in a General Factorial Design (GFD). Factors were coded and scaled within the range of +1 to −1, accounting for variations in the units of independent variables. This study utilized the Nusselt number and thermal resistance, along with an effective regression analysis, to develop a novel predictive model. Key performance indicators included R², adjusted R², predicted R², coefficient of variation (CV), and parameter separation from the best-fit results. The proposed model demonstrated remarkable accuracy in predicting the Nusselt number, with values of R², predicted R², adjusted R², and CV at 98.15 %, 97.08 %, 94.87 %, and 2.44 %, respectively. For thermal resistance, the corresponding values were 97.91 % for predicted R², 96.70 % for adjusted R², 94.21 % for CV, and 3.33 % for parameter separation. Therefore, it is evident that the proposed model is highly accurate in predicting semicircular radial heat sink performance, offering a robust tool for future heat sink designs and sustainable thermal management systems.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105727"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}