Heat Transfer最新文献

{"title":"Validation of Magnesium Oxide Additive Effects on Diesel Engine Performance Through Crystal Structure and Thermal Stability Analyses","authors":"Erdal Çılğın","doi":"10.1002/htj.23250","DOIUrl":"https://doi.org/10.1002/htj.23250","url":null,"abstract":"<div>\u0000 \u0000 <p>This study investigates the effects of magnesium oxide (MgO) nanoparticles on combustion performance and emissions in diesel engines. MgO's well-ordered crystal structure, high thermal stability, and oxygen-carrying capacity positively influence engine performance. The effects of 50 and 100 mg/L MgO concentrations were compared, showing up to a 5% improvement in brake thermal efficiency at 100 mg/L. Additionally, reductions of 8% in CO and 10% in HC emissions were achieved. MgO's crystal structure contributed to higher combustion temperatures, leading to lower harmful emissions. However, an increase in NO_<i>x</i> emissions was observed, indicating the need for careful balancing between performance improvements and emission control. These results highlight MgO as an efficient and environmentally friendly fuel additive.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1665-1680"},"PeriodicalIF":2.8,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143380389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combined Impacts of Thermal and Mass Stratification on Unsteady MHD Parabolic Flow Along an Infinite Vertical Plate With Periodic Temperature Variation and Variable Mass Diffusion","authors":"Digbash Sahu,&nbsp;Rudra Kanta Deka","doi":"10.1002/htj.23240","DOIUrl":"https://doi.org/10.1002/htj.23240","url":null,"abstract":"<div>\u0000 \u0000 <p>This study investigates the dynamics of unsteady MHD parabolic flow along an infinite vertical plate, with a focus on the impacts of thermal and mass stratification under periodic temperature variations and variable mass diffusion. Utilizing the Laplace transform technique for deriving exact solutions, this research innovatively integrates both thermal and mass stratification effects without resorting to approximations. The main objective is to assess how these stratifications influence flow dynamics, temperature, and concentration profiles in environments with varying magnetic fields. The study contrasts these findings against classical non-stratification cases, offering a detailed comparison of fluid behavior under different conditions. Results indicate that thermal and mass stratifications substantially decrease velocity and stabilize temperature profiles, pointing to a damping effect on fluid motion while also controlling diffusion processes. These stratifications lead to higher Nusselt and Sherwood numbers, suggesting improved heat and mass transfer efficiencies. In contrast, the absence of stratification results in higher velocities and less stable temperature and concentration distributions. The findings underscore the significant role of stratification in optimizing fluid dynamics and enhancing the efficiency of heat and mass transfer processes, providing crucial insights for engineering and environmental applications where such conditions prevail.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1638-1649"},"PeriodicalIF":2.8,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143380463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Magnetic Field and Slip Conditions on Flow in a Rotating Porous Channel With Viscous Dissipation","authors":"Vineet Kumar Verma,&nbsp;Abdul Faiz Ansari","doi":"10.1002/htj.23241","DOIUrl":"https://doi.org/10.1002/htj.23241","url":null,"abstract":"<div>\u0000 \u0000 <p>This study examines the steady flow of an electrically conducting fluid through a rotating porous channel bounded by stationary, impermeable horizontal plates at constant temperature. The primary aim is to explore the combined effects of a magnetic field, wall slip conditions, and viscous dissipation. The channel rotates at a constant angular velocity, with slip conditions applied at the walls. A pressure gradient drives the primary flow, while rotation generates the secondary flow. Analytical solutions for velocity profiles and volumetric flow rates are obtained, and the temperature distribution is calculated using MATLAB's “bvp4c” function. The research offers novel insights into the behavior of primary and secondary flow velocities under different Hartmann and Taylor numbers, emphasizing the impact of slip conditions. Additionally, the influence of the Eckert number on temperature is analyzed in conjunction with these parameters. These findings contribute valuable theoretical perspectives for enhancing cooling systems in rotating machinery using conductive fluids in porous channels. This study opens avenues for future research to investigate unsteady flow conditions and the effects of variable magnetic fields and rotational speeds on fluid behavior in rotating porous channels.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1562-1573"},"PeriodicalIF":2.8,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of Hydrothermal Flow and Performance of Heat Transfer in 3D Pipes Based on Varying Dimple Structure Configurations","authors":"Saad Raad Al-Haidari,&nbsp;Ahmed Ramadhan Al-Obaidi","doi":"10.1002/htj.23244","DOIUrl":"https://doi.org/10.1002/htj.23244","url":null,"abstract":"<div>\u0000 \u0000 <p>In the current work, the study examines the flow patterns and heat transfer capabilities of tubes with various spherical dimple configurations. A numerical analysis, supported by experimental validation on a reference model, was conducted on a circular tube with an alternating flow path. The primary goal was to enhance the thermal performance of circular tubes by inducing mixing and vortex flows. The impact of three design factors on thermal–hydraulic performance was investigated, dimple pipe diameter (DPD), dimple group number (DGN), and number of dimples (NODs). Dimpled tubes consistently outperformed smooth tubes in heat transfer due to increased flow mixing and separation. Both increasing the Reynolds number and decreasing the design factors led to the formation of mixing and vortex patterns. The performance evaluation factor (PEF) varied across different dimple configurations. For DPD, PEF ranged from 1.14 to 1.33; for DGN, it ranged from 1.15 to 1.28; for NOD, it ranged from 0.95 to 1.21, all within a Reynolds number range of 4000–15,000. At a Reynolds number of 6000, all three configurations of DPD, DGN, and NOD outperformed the smooth pipe in terms of the Nusselt number. For DPD, Nusselt number improvements ranged from 25.7% to 30.8%, and friction factors increased by 21% to 67%. DGN configurations exhibited a wider range of Nusselt number enhancement from 25% to 49.6%, and friction factor increase from 37% to 72%. NOD configurations also demonstrated consistent improvements, with Nusselt number increases ranging from 27.35% to 31% and friction factor increases from 42% to 74%. Spherical dimples can significantly enhance the thermal–hydraulic performance of tubes, so the best configuration depends on the specific application, and the highest performance, with a 1.33 increase in PEF, was achieved with a dimple diameter of 2 mm (DPD = 2 mm) and a dimple density of four dimples per unit area (NOD = 4).</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1589-1610"},"PeriodicalIF":2.8,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143380225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Interface Bonding on Optimizing the Heat Transfer in Substrate Board With an Array of Heat Sources","authors":"Y. Aditya Varma,&nbsp;N. Rino Nelson,&nbsp;S. P. Venkateshan","doi":"10.1002/htj.23243","DOIUrl":"https://doi.org/10.1002/htj.23243","url":null,"abstract":"<div>\u0000 \u0000 <p>Effective heat distribution in electronic circuitry is essential to improve the performance and life of electronic components such as chips. This study presents a numerical analysis of heat transfer on a substrate board populated with an array of discrete heat sources, assumed to be placed in a horizontal air channel for forced convection cooling. The analysis of electronic packages is performed, taking into consideration the effect of thermal contact conductance (TCC) between the heat source (chip) and the substrate board. The dependence of the temperature distribution on the Reynolds number of air at the inlet and the heating power from the heat source is investigated for inlet velocities ranging from 0.6 to 1.4 m/s and observed to be significant. Temperature and heat transfer coefficient are observed to systematically increase with the increase in the heat dissipation from the heat source. Two configurations—inline and staggered—are analyzed, with the staggered configuration showing superior cooling performance. This improvement is attributed to the fact that staggered arrangements expose fewer heat sources to pre-heated air before it exits the system. Additionally, the location of the heat source reaching the highest temperature is found to be highly dependent on the TCC of the bonding material between the heat source and the substrate. A hybrid optimization strategy is employed, by combining Artificial Neural Network (ANN) and Genetic Algorithm (GA) for optimizing the location of heat sources. ANN is used for predicting the temperature distribution, subsequently followed by GA to minimize the maximum temperature attained by the heat generating source by varying other control variables like TCC thickness, inlet velocity, and heat generation. The thickness of the bonding layer is varied from 0.225 to 0.271 mm and the heat generation is varied from 1000 to 2000 W/m². Among them, TCC is observed to be an important parameter controlling the optimum location of heat generating sources. The results obtained from the proposed hybrid optimization strategy are compared with the simulation results and observed to be reasonably close.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1574-1588"},"PeriodicalIF":2.8,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143380221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetohydrodynamic Natural Convection in a Circular Dome-Shaped Enclosure","authors":"K. Venkatadri","doi":"10.1002/htj.23245","DOIUrl":"https://doi.org/10.1002/htj.23245","url":null,"abstract":"<div>\u0000 \u0000 <p>The design of flow structures plays a crucial role in enhancing natural convective heat transfer within enclosures. By optimizing the geometry of enclosures to influence flow structures, we can significantly improve their natural convective heat transfer performance. Specifically, the dome-shaped wall can alter flow direction, improving flow circulation and natural convection. The current study conducts a numerical investigation of the laminar flow and natural convective heat transfer of air within a dome-shaped enclosure, while also considering the impact of a magnetic field. The analysis encompasses the interaction between magnetic field and buoyancy-driven flow. Governing equations for momentum, energy, and angular momentum are formulated, integrating the influence of the Lorentz force. The working fluid <i>Pr</i> = 0.71 is considered in this study. The equations are transformed into dimensionless form using key parameters, such as the buoyancy number (<i>Ra</i>) and Hartmann number (<i>Ha</i>). The modeled partial differential equations were carried out with a vorticity-stream function algorithm to explore the influence of magnetic field strength on the flow and thermal characteristics. Results indicate significant alterations in flow patterns and temperature distribution behavior under varying magnetic field and Rayleigh number. The interaction between buoyancy and magnetic fields plays a critical role in determining the heat transfer characteristics of an incompressible fluid, with <i>Ra</i> enhancing, and <i>Ha</i> suppressing, convective efficiency. Heat transfer enhancement of 82.84% is noticed for a Rayleigh number ranging from 10³ to 10⁴, while a 48.316% decrement is found for a Hartmann number ranging from 0 to 10 with <i>Ra</i> = 10⁵. The transition from a magnetically dominated regime (high <i>Ha</i>) to a thermally driven regime (low <i>Ha</i>) leads to a shift from a uniform temperature field to one with more complex thermal layering and mixing, which is reflected in the varying shapes and amplitudes of the Nusselt number distributions. At higher <i>Ha</i> values, magnetic forces dominate, significantly suppressing buoyancy-driven convection, and reducing the intensity of thermal mixing.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1611-1622"},"PeriodicalIF":2.8,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational Analysis and Experimental Investigation of the Performance of an Evacuated Tube Solar Air Heater Incorporating Therminol-55 as a Thermal Energy Storage Medium","authors":"Adarsh Abi Mathew,&nbsp;Neeta Mandhare","doi":"10.1002/htj.23226","DOIUrl":"https://doi.org/10.1002/htj.23226","url":null,"abstract":"<div>\u0000 \u0000 <p>The evacuated tube solar air heaters (ETSAHs) are gaining popularity today because of their reduced heat loss capability. A performance evaluation of the evacuated tube solar collector (ETSC) using a thermal energy storage (TES) facility was carried out during the study. A new heat pipe (HP) system with a TES unit directly integrated into it was used in the study along with ETSAH. The novel HP system directly stores the thermal energy and is capable of heating the air uniformly from all directions. Therminol-55 (T-55) was the sensible heat storage material integrated inside a common condenser HP system. The solar collector's performance was evaluated at air flow rates ranging from 0.003 to 0.02 kg/s. The HP and T-55 exhibited a maximum temperature of 121°C and 127°C. The highest temperature of the air leaving ETSAH-TES was 128°C. ETSAH-TES delivered hot air over 100°C continuously for 7 h. The results depict that even when solar energy was erratic, the HP developed in this research supplied a continuous hot air flow. The average energy and exergy efficiency achieved was 37.87% and 2.8%, respectively. T-55 can store a maximum of 1920 kJ of energy. With a standard deviation ranging from 0.2% to 1.87%, the ETSC-TES numerical analysis is in excellent agreement with experimental results.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1543-1561"},"PeriodicalIF":2.8,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143380977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimization of Conductive Partitions on the Mixed Convection in a Vented Cavity","authors":"Nihal Uğurlubilek,&nbsp;Zerrin Sert,&nbsp;Fatih Selimefendigil,&nbsp;Hakan F. Öztop","doi":"10.1002/htj.23200","DOIUrl":"https://doi.org/10.1002/htj.23200","url":null,"abstract":"<div>\u0000 \u0000 <p>Numerical estimation for the impacts of the conductive partitions having different positions on the mixed laminar convection of air in a 2D vented enclosure was examined. The variable parameters are accepted as Reynolds number (<i>Re</i> = 10–1000), Richardson number (<i>Ri</i> = 0–5), and size of the partition (0.25<i>H</i>, 0.5<i>H</i>, and 0.75<i>H</i>). Twelve cases having several partition arrangements were analyzed. It was observed that excellent convection control can be obtained by using conductive partitions depending upon the <i>Re</i> and <i>Ri</i> combinations. Generally, at small <i>Re</i>, the mean <i>Nu</i> was not affected by the variation of geometry and <i>Ri</i> at small <i>Re</i>. The highest <i>Nu</i> is achieved in Case 12, a cavity with two partitions having a length of 0.75. At <i>Re</i> = 1000, the rate of increase in <i>Nu</i> at <i>Ri</i> = 0, 1, and 5 are obtained at 2.085, 1.868, and 1.43 according to the bare cavity, respectively. In addition, the effect of the solid–fluid thermal conductivity ratio (<i>K</i> = 0.002, 0.2, 1, 5, and 40) on heat transfer was investigated for Case 12. Empirical power-law Nusselt number correlation was derived for a 2D vented cavity with/without conductive partitions. In conclusion, the maximum heat transfer enhancement rate is obtained in the vented cavity with two length partitions of 0.75. At <i>Re</i> = 1000, the increases in heat transfer rate (<i>Nu</i>/<i>Nu</i>₀) for <i>Ri</i> = 0, 1, and 5 are 2.085, 1.87, and 1.43 times higher, respectively, compared with the bare cavity. In terms of effectiveness, Case 12 is the optimum case after Case 0.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1530-1542"},"PeriodicalIF":2.8,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143380976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance of North Wall Modified Passive and Active Greenhouse Groundnuts Dryers","authors":"Shimpy,&nbsp;Mahesh Kumar,&nbsp;Vishal Sahu,&nbsp; Mahesh,&nbsp;Shravan Yadav,&nbsp;Aman Saini","doi":"10.1002/htj.23237","DOIUrl":"https://doi.org/10.1002/htj.23237","url":null,"abstract":"<div>\u0000 \u0000 <p>An even-span greenhouse groundnuts dryer having a reflective north wall has been developed and tested under passive and active modes. The effects of varying sample mass (580, 880, and 1180 g) on the thermal and enviro-economic performance indicators of the dryer have been investigated. The Nusselt number expression, embodied energy (EE), and capital cost (<i>C</i>_c) were used for thermal, environmental, and economic assessment of the dryer. The drying behavior of the groundnuts samples has also been estimated using the moisture ratio in drying models. Thermal indicators were observed to increase with increased sample mass and were found higher under active mode. The values of EE and <i>C</i>_c of the dryer under passive and active modes were 145.24 and 158.42 kWh, and INR 1257.11 and INR 2157.11, respectively. Enviro-economic indicators were also observed to improve with increased sample mass and were comparable for both the passive and active modes. The moisture ratio for all the samples shows an excellent fit with the Midilli–Kucuk model. An average Midilli–Kucuk model has been recommended to predict the drying behavior of groundnuts in the developed greenhouse dryer.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1517-1529"},"PeriodicalIF":2.8,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143380942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermally Intense Cilia Generated Motion of Two-Phase Biological Fluid in a Vertical Tube Under Wall Properties","authors":"Mubbashar Nazeer,&nbsp;Muna Al-Razgan,&nbsp;Yasser A. Ali,&nbsp;Talib K. Ibrahim,&nbsp;Nargiza Kamolova,&nbsp;Manish Gupta","doi":"10.1002/htj.23225","DOIUrl":"https://doi.org/10.1002/htj.23225","url":null,"abstract":"<div>\u0000 \u0000 <p>The exact solution is obtained for the unsteady fluid–particle suspension model of Rabinowitsch fluid through a vertical tube having ciliated walls. The flow inside the tube is produced by the metachronal waves of cilia. The lubricant approach is used to produce the solution of fluid phase velocity, particle phase velocity, stream function, and temperature. The pressure rise is calculated through a numerical analytical technique. The graphs are constructed to explore the characteristics of the velocity of both phases, thermal analysis, trapping phenomena, pressure gradient, and pressure rise. It is known that the slip parameter diminishes the velocity of both phases. The thermal slip parameter and density number upsurge the thermal profile. The particle phase velocity is less than the fluid phase. The present analysis can be useful in biomedical engineering to construct the heart and lung machines that are used to pump blood in arteries.</p>\u0000 </div>","PeriodicalId":44939,"journal":{"name":"Heat Transfer","volume":"54 2","pages":"1506-1516"},"PeriodicalIF":2.8,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143381063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}