Average Heat Research Articles

Comparative Analysis of Heat Exchanger Models for Phase Change Material Melting Process: Experimental and Numerical Investigation

ABSTRACTThermal energy storage systems using PCM offer promising solutions for efficient thermal applications. This study aims to provide valuable insights into the PCM melting process and compare the thermal performance of different heat exchanger models. The experimental rig is carefully designed to simulate a shell and tube heat exchanger with five longitudinal copper fins at specific conditions. Three distinct models of the heat exchanger, labeled Models A, B, and C, were examined for their heat transfer efficiency during the melting process. Numerical simulations were conducted for the three models and compared with experimental results. Model A represented the benchmark model. It had uniform fin length, location, and angle. Model B was the modified design aimed at enhancing melting progress. These modifications included a longer lower fin, a shorter side fin compared to the reference, and a lower fin angle to optimize heat transfer performance. Model C incorporates further design modifications, with a longer lower fin, a shorter top fin, and different lower fin location. Numerical simulations and experimental observations revealed significant differences in heat transfer performance among the three models. The average heat transfer rates, measured up to the critical decline point, are crucial parameters for practical applications. A comparison among the three models showed that Model B surpassed the average heat transfer rate up to the critical point of Models A and C by 10% and 4%, respectively, demonstrating its superior practical applicability.

Numerical investigation on boiling crisis characteristic of a 7-rod HCF assembly in hexagonal lattice

Helical cruciform fuel (HCF) has the advantages of larger heat transfer area, enhanced coolant mixing and self-supporting, which contribute to increasing power density and safety margins. Compared with the square lattice configuration, the hexagonal arrangement of HCF assembly is more compact, which can help achieve a higher power density. In this paper, the flow characteristics and heat transfer behaviors of HCF in hexagonal lattice were predicted at high and low vapor quality during boiling crisis based on Eulerian two-fluid model. The influence of twist pitches and cross-sections of the fuel rod on heat transfer efficiency and fuel temperature was also studied. The cross-flow intensity changed periodically with a 30° cycle at low vapor quality, and did not fluctuate periodically at high vapor quality, which decreased with the increase of flow resistance. The highest heat flux of HCF rod was the at the blade root and the lowest was at the blade tip, and the maximum to average heat flux ratio was about 1.8. The peak vapor fraction and temperature occurred at leeside side of the fuel rods. The increase of the twist pitch reduced the critical heat flux (CHF), and the increase of blade length enhanced the non-uniformity of heat flux distribution. During boiling crisis, the maximum temperature of the fuel was lower than the phase transition temperature of U-50 wt%Zr alloy, which means the cladding meltdown caused by boiling crisis will occur before phase transition of the fuel.

Spent tea leaves and tea bags - promising biofuels?

The spent tea leaves used after the extraction of liquid from processed tea are insufficiently utilized waste, rich in essential amino acids, polyphenols, alkaloids, and minerals, produced in large quantities, e.g., in tea houses, hospitals, school canteens, etc. Therefore, this study is aimed at characterizing this waste, how it is processed into pellets and how it subsequently increases its energy potential by torrefaction. The influence of the method of tea packaging, i.e., loose tea leaves or tea bags, was also considered. Several types of tea waste were processed using a pilot plant pelletizing press and torrefaction stand. The prepared pellets were characterized by mechanical parameters, such as the pellet durability index, the wettability index, water resistance, hardness, or specific bulk density, and were integrated by FTIR measurements. Furthermore, pellet’s energy parameters, such as higher heating value, lower heating value, and elemental analysis, were compared. The results show that non-torrefied pellets have an average combustion heat of 19 KJ.kg-1, while torrefied pellets have a value of 9 KJ.kg-1 higher. Overall, the study demonstrates that spent tea leaves can be converted into a sustainable source of bioenergy and presents a solution for the treatment of this waste, as well as a renewable energy option.

Experimental and simulation study on hygroscopic hydrogel-based thermal management of electronic device

With the increasing power of electronic devices, thermal management has become crucial for their operational efficiency and lifespan. In this work, we have demonstrated a sorption-based thermal management strategy enabled by hygroscopic hydrogel. The polyacrylamide (PAM) hydrogel impregnated with LiCl (PAM-LiCl) was attached to a silicon wafer. And Pt metal circuits were coated to the silicon wafer to measure the temperature variations under different heat flux densities. The results show that the hydrogel can effectively reduce the surface temperature. At a heating power of 0.3 W/cm2, the temperature control duration reached 30 min, with an average effective heat transfer coefficient of 65.5 W/(m2·K) and an effective heat storage density of 171 J/cm2. Additionally, we developed and validated a multiphysics model considering desorption and vapor diffusion within the hydrogel. Numerical results indicate that during the desorption cooling process, the surface heat transfer resistance and the internal diffusion resistance play a dominant role. Additionally, we analyzed the effects of material properties, structure parameters, and operating conditions on the thermal management performance. This study helps to understand the key points of sorption-based thermal management technology and guide the design and optimization of sorption-based thermal management system.

Thermodynamic study of semi-closed rankine cycle based on direct combustion of hydrogen fuel

Electrolysis of water for hydrogen-production has enormous potential. This study proposes a semi-closed Rankine cycle for efficiently utilizing direct hydrogen combustion via thermal power conversion. Unlike traditional closed Rankine cycles, combustion occurs inside the combustion chamber with hydrogen and pure oxygen, followed by a mixed heat exchange with the mainstream working fluid, water. The heat absorption process of the semi-closed Rankine cycle occurs within the working fluid and exhibits characteristics of both open and closed cycles. Thus, this cycle can combine the advantages of desirable parameters and isothermal heat rejection of the Rankine cycle. Applying the semi-closed Rankine cycle to hydrogen fuel utilization yields a higher energy efficiency, especially when coupled with a supercritical compression regeneration process. The main steam parameters were 620 °C/30 MPa, the cycle's average heat absorption temperature reached 561 °C, and its energy efficiency was 59.35%. When the main steam parameters were increased to 1200 °C/30 MPa, the average heat absorption temperature rose to 1021 °C and its energy efficiency was 68.27%, demonstrating a significant efficiency advantage. The newly proposed semi-closed Rankine cycle based on direct combustion of hydrogen fuel provides a novel and feasible path for exploring the efficient utilization of hydrogen.

Wetting dynamics and heat transfer of droplet evaporation around boiling point: Facile manipulation by surface roughness

The evaporation of water–ethanol droplets on solid surfaces has vast potential for applications in thermal management, microfluidics, and biomedical sciences, while the approach of manipulating wetting dynamics and heat transfer of droplet evaporation around the boiling point remains open for investigations. The present study proposes a facile approach: fabricating solid surfaces with diverse roughness by sandpaper milling with different grit densities, which can alter the wetting and heat transfer characteristics of droplet evaporation. We discover that when the temperature of the heated surface exceeds the droplet boiling point, the existence of bubbles affects the solid–liquid wetting state; surface roughness alters the ability of bubble departure, thus determining the solid–liquid contact and the contact line retraction time. Consequently, in this case, the solid–liquid contact area and the heat absorbed from heated surfaces for droplets changes with surface roughness, altering the droplet evaporation time and the average heat flux at the solid–liquid interface. Bridged by droplet wetting dynamics, the heat transfer of droplet evaporation above the boiling point can be manipulated by adjusting surface roughness, offering a facile approach to tuning the process of droplet evaporation in the related industrial applications.

Methyl ricinoleate droplet impact on a high temperature stainless steel surface: Dynamic behavior and heat transfer

The rapid and uniform heating of the feedstock plays a key role in pyrolysis processes. Dispersing methyl ricinoleate (MR) into spray droplets can improve the heating speed and uniformity in the pyrolysis process, which is of great benefit to the yield of the target product. This article describes the results and mechanisms of single MR droplet impacting on a heated stainless steel surface at different temperatures (385 ∼ 520 °C). Two non-contact measurement techniques, including a high-speed camera and a thermal infrared imager, were used to record the dynamic behavior and heating effects of the MR droplet on the heated surface at different temperatures, respectively. Four representative impingement states were observed during droplet impact: adhesion rebound, adhesion rebound with breakup, bouncing, and bouncing with breakup. As a result, a comprehensive map was created, based on a dimensionless analysis, describing the relationships between the typical states. Regarding the quantitative analysis, the maximum spreading factor and the dimensionless droplet residence time were linearly related to the 0.336 and 0.389 powers of the Weber number, respectively. By calculating the average heat flux of a droplet, it was found that it is related to the stainless steel surface temperature, the droplet saturation temperature, and the Reynolds number. The transient temperature at the surface of the MR droplet was measured to quantify the effectiveness of the heating. This study could provide a theoretical basis for the regulation and optimization of MR pyrolysis conditions.

Heat Strain in Different Hot Environments Hiking in Wildland Firefighting Garments.

Wildland firefighters can work at high intensity in hot environments for extended periods of time. The resulting heat strain may be modified by the environmental conditions (i.e., ambient temperature and humidity [RH]) even at equal wet-bulb globe temperatures. This investigation assessed if a hot and dry condition would create greater strain than moderate and high humidity at equivalent wet-bulb globe temperature (28°C). Twelve participants (age 24±2 y) walked at 40-50% maximum aerobic capacity for 90 and 40 min separated by a 20 min rest in dry (40°C, 20% RH), moderate-humidity (34°C, 50% RH), and high-humidity (29°C, 90% RH) conditions wearing fire resistant jacket, pants, gloves, and helmet with the neck and face exposed. Peak core temperature was higher in moderate-humidity (38.9±0.2°C, p=0.01) and high-humidity (38.9±0.6°C, p<0.01) than dry condition (38.5±0.3°C). Average net heat gain was less in dry (33±22 W) compared to moderate-humidity (38±23 W, p<0.01) and high-humidity (39±28 W, p<0.01). Peak heart rate (174±14 bpm, p=0.94), Physiological Strain Index (7.7±1.4 score, p=0.99), perceived exertion (8±2 rating, p=0.97), and Perceptual Strain Index (7.3±1.6 score, p=0.99) were not different in high-humidity compared to the dry condition (167±19 bpm, 6.9±1.3 score, 6±2 rating, 7.3±1.7 score, respectively). Whole-body sweat rate (15±6 mL/min, p=0.58) and thermal sensation (7±1 rating, p=0.37) were not different. Hiking in a humid condition while wearing protective garments creates greater exertional heat strain compared to a dry condition of equivalent wet-bulb globe temperature. Wildland firefighters should consider extra strategies to mitigate hyperthermia when humidity is high.

Performance of bread wheat advanced lines under late sowing and hydric stress during the crop season 2020-2021

Thirty four advanced bread wheat lines and cultivar Borlaug 100 were sown on January 15 and 30, 2021, at the Norman E. Borlaug Experimental Station, in the Yaqui Valley, Sonora, México. Plots consisted of 1 bed 2 m long with two rows and 0.80 m apart with two replications, and a seed density of 100 kg ha-1 with two complementary irrigations. Average daily temperature (°C), maximum, minimum, relative humidity, rainfall, heat and cold units were recorded from January 1 to May 15, 2021. The average days for heading of the group was 69 for the first sowing date and 66 for the second one, while days for physiological maturity were 99 and 90, respectively. The average plant height of the group for the first date was 97.5 cm and 94 for the second one; the sister line SOKOLL/5/W15.92/4/PASTOR//HXL7573/2*BAU/3/ WBLL1/6/SOKOLL/3/PASTOR//HXL7573/2*BAU (PTSS12SHB00020T-0TOPB-099Y-099B-25Y-020Y-0B) consistently reached the maximum height with 107.5 and 110 cm in each date, respectively. The average grain yield per plot was 294 g; line BAJ #1*2/4/BETTY/3/CHEN/AE.SQ//2*OPATA showed the highest yield with 345.4 g which was above 4.3 t ha-1, followed by SOKOLL/3/PASTOR//HXL7573/2*BAU/4/ASTREB/5/PIHA//WORRAKATTA/2*PASTOR /3/PRL/2*PASTOR, also above 4.3 t ha-1. The average hourly temperature was 18.4 °C with a maximum of 40.8 °C and a minimum of 3.9 °C, and the number of heat and cold units was 203 and 393, respectively.

Hierarchical Nano/Micro-Array Structured CuMgAl-LDH/rGO Hybrids for Remarkably Improved Flame Retardancy and Smoke Suppression Performance of Flexible Polyvinyl Chloride.

In this study, we explored the rational integration of layered double hydroxides (LDHs) with reduced graphene oxide (rGO) to create a hierarchical nano/microarray structured CuMgAl-LDH/rGO hybrid aimed at enhancing the flame retardancy and smoke suppression properties of polymer nanocomposites. The results indicated that the limiting oxygen index (LOI) value of the G-CuMgAl/polyvinyl chloride (PVC) composite reached 35.8%, reflecting a 6.4% increase compared to pristine PVC (29.4%), and achieved a UL-94 V-0 rating. Furthermore, in comparison to pristine PVC, the peak heat release rate (PHRR) of the G-CuMgAl/PVC composite was significantly reduced by 40.2%; the total heat release rate (THR) decreased by 24.3%; the maximum average heat release rate (MARHE) diminished by 41.6%; the peak smoke production (PSPR) decreased by 37.8%; the total smoke production (TSP) was reduced by 31.3%; and the average effective heat of combustion (av-EHC) decreased by 15.2%. The enhanced flame retardancy and reduced smoke production can primarily be attributed to the multiple synergistic interactions among the highly dispersed constituents and the nano/microstructures, which effectively impede the transfer of heat, mass, and O2 from various directions while preventing further combustion of the underlying matrix by creating a tortuous path in the condensed phase. Additionally, this study provides a novel perspective on the design and synthesis of structured LDHs/rGO hybrids, with the potential to enhance flame retardancy and smoke suppression properties across a broad spectrum of polymer materials.

Hybrid nanofluid flow in chamber containing heated and concentrated internal source under the effectiveness of applied magnetic field

Extensive applications of buoyancy-induced flow owing to temperature and concentration gradients have been found exclusively in diversified industrial and technological processes, such as heat exchange systems, solar collectors, heat sinks, and power plants. Additionally, installation of internal sources in confined configurations is essential in operation performance of many devices relevant to transformers, radiators, air cooling engines, fuel cells, semiconductor instruments and so forth. Furthermore, in recent decades, hybridized nanoparticles have been added to different setups to increase their efficiency. Therefore, the premier motive of current work is to examine mass and heat transport mechanisms in water-based fluids encompassed in a corrugated rectangular chamber with the induction of copper (Cu) and alumina (Al2O3) in a hybrid manner. A horizontally oriented magnetic field is assumed, along with the adjustment of a uniformly heated and concentrated source. The thermal conductivity relation proposed by Maxwell is obliged to scrutinize the performance of hybridized nanoparticles in controlling heat exchange in the domain. In this study, a power-law viscosity model is manifested along with utilization of other conservation laws and model structuring in the form of dimensionless expressions is performed by accomplishsing variables. Finite element simulations are executed by utilizing COMSOL Multiphysics 6.0 to solve developed governing equations system. The quantities of interest, such as average heat and mass fluxex, along with presentation of percentage change versus sundry factors, through graphical and tabular display. From a thorough examination, it is inferred that magnetic field plays an effective significance in controlling the excessive thermosolutal gradients. In addition, inudction of hybridized nanoparticles will positively affect thermal exchange in the base liquid compared to the situation when nanoparticles are not added. It is also deduced that average Nusselt and Sherwood numbers decreased up to 3 % and 2.4 % respectively for hydromagnetic situation (Ha = 0) in comparison to hydrodynamic case (Ha ≠ 0). Decrement in coefficients representing thermosolutal exchange reach up to 55 % and 66 % approximately against increment in number of corrugations. Induction of hybrid nanoparticles resulted in an increase in the coefficients of thermal and solutal transfer up to 14 % and 22 %, respectively, compared to the scenario where the base fluid contained no particles. For shear thinning aspects of non-Newtonain liquid, Nusselt and Sherwood numbers exceeds in comparison to Newtonian case and contrary aspects are observed for shear thickening materials.

Impact of nanoparticle shape on the thermal performance of eco-friendly soybean-based nanofluids in cooling titanium alloys

Ecofriendly soybean coolant offers a sustainable alternative to conventional coolants, providing excellent thermal performance while reducing environmental impact. Its biodegradable nature and low toxicity make it a safe choice for various cooling applications, promoting greener industrial practices. This study investigates the thermal performance of eco-friendly soybean nanofluids dispersed with alumina and molybdenum disulfide (MoS2) nanoparticles for cooling a titanium alloy block. The investigations are conducted using single and dual nozzle setup to assess the impact of nanoparticle shape, volume fraction and Reynolds number on heat transfer characteristics of ecofriendy coolant. The discretization is conducted using the finite volume method, and the Nusselt number is calculated from the convective heat transfer coefficient. Results show that platelet-shaped nanoparticles exhibit superior thermal conductivity and heat transfer performance compared to spherical and cylindrical shapes. Increasing the volume fraction of MoS2 platelet-shaped nanoparticles from 0.5% to 6% results in a reduction of the average temperature distribution of the titanium block by 26.53% in the single-nozzle setup and 28.87% in the dual-nozzle configuration. The dual nozzle arrangements significantly enhance heat dissipation, with MoS2 nanoparticles decreasing the temperature distribution by 9.24% in the single-nozzle setup and 15.78% in the dual-nozzle setup compared to alumina nanoparticles. Optimal thermal performance is observed at elevated Reynolds numbers, where platelet-shaped MoS2 nanoparticles achieve the highest Nusselt numbers. Specifically, incorporating MoS2 cylindrical-shaped nanoparticles into soybean oil at higher Reynolds numbers improves average heat transfer by up to 29.16% when compared to cylindrical alumina nanoparticles. The enhancements in heat transfer for spherical and platelet-shaped MoS2 nanoparticles are 37.51% and 46.66%, respectively, relative to cylindrical alumina particles. This research offers crucial guidance on developing and enhancing sustainable coolants, revealing the significance of nanoparticle shape in optimizing thermal performance and paving the way for cleaner production processes that prioritize environmental responsibility.

Numerical Study on Heat Transfer Characteristics of Jet Impingement by using MgO Nanofluid

Liquid impingement jet can provide high local heat transfer coefficients between the impinged liquid and the targeted surface. Jet impingement is utilized in the applications which is related to rapid cooling and better control of high temperature in many applications. The studies are carried out numerically by using ANSYS Workbench 18.2. Hexagonal meshing and Shear-Stress Transport (SST) turbulence model is used in the numerical simulation. By using SST turbulence model, the effect of jet Reynolds number, nanofluid volume concentration on the average heat transfer coefficient of the target plate is analysed and discussed. For the effect of varying the Reynolds number, it is observed that the surface average heat transfer coefficient increases at least 76.18% as the Reynolds number increases from 5000 to 10000. Moreover, the heat transfer coefficient increases as the volume concentration increases from 0% to 5%. It is also observed that when the nanofluid with higher thermal conductivity will results in higher heat transfer coefficient where the MgO nanofluid showed the highest heat transfer coefficient. As a conclusion, by increasing Reynolds number, volume concentration and thermal conductivity of nanofluid, the heat transfer coefficient can be enhanced.

Characterization of Bread Wheat Genotypes Using SSR Markers for Terminal Heat Tolerance

Wheat is a major global food crop, but its productivity is increasingly threatened by terminal heat stress due to climate change. This study aimed to characterize the genetic diversity and heat tolerance of widely grown bread wheat genotypes using SSR markers to identify heat-tolerant cultivars adaptable to various regions in Bangladesh. A total of 15 genotypes were screened, and 13 polymorphic SSR (Simple Sequence Repeats) markers were used to determine the genetic similarity and categorize genotypes based on their heat tolerance. The molecular analysis revealed 13 polymorphic SSR markers that produced distinct PCR (Polymerase Chain Reaction) bands across the different genotypes. By the conclusion of the study, bread wheat genotypes were categorized as either tolerant or sensitive to heat, and the genetic similarity among the varieties was assessed using molecular markers. The genetic similarity coefficients obtained from the SSR primer screening ranged from 0.00 to 0.925. The lowest genetic distance (0.000) was found in Nadi 2 vs BAW1147 variety pair indicating that they are genetically similar to each other. Comparatively higher genetic distance (0. 925) was observed between BAW 1290 vs BARI Gom 28. The dendrogram divided the fifteen genotypes into two main groups, A and B, both formed at a similar coefficient of 0.05. Group A included seven genotypes and was further divided into two clusters, while Group B comprised eight genotypes, which were also divided into two clusters. The categorization of the genotypes was based on the average Heat Susceptibility Index (HSI), Thousand Grain Weight (TGW), grain yield, and the relative reduction in TGW and grain yield under stress conditions compared to timely sown conditions, aligning with the molecular data. Among the fifteen genotypes, BARI Gom 25, BARI Gom 26, BARI Gom 27, BARI Gom 28, BARI Gom 29, BARI Gom 30, and BARI Gom 31 demonstrated their adaptability to late sown conditions. The heat tolerance observed in these genotypes, as indicated by their SSR marker scores, is anticipated to provide valuable insights for molecular breeding studies focused on heat resistance.

Experimental investigations of flow boiling heat transfer performance in finned micro-channels

The flow boiling heat transfer and pressure drop in rectangular-finned micro-channels (i.e. micro-channel with rectangular fins) were experimentally investigated at five different fin-heights. At three different mass fluxes and a range of heat fluxes, heat transfer coefficients and pressure drops in the micro-channels were measured. The flow patterns during the flow boiling process were visualized to estimate the flow regime transitions in the micro-channels. The experimental results showed that the micro-channel with 500 μm height fins (i.e. tip clearance = 100 μm) performs the highest heat transfer and shows the highest resistance to flow boiling instability among the studied cases. Compared to the smooth micro-channel, the averaged heat transfer coefficient in the micro-channel with 500 μm height fins has been improved by up to 133.9 % at the same wall temperature. Compared to the micro-channel with 600 μm height fins (i.e. tip clearance = 0 μm), the averaged heat transfer coefficient in the micro-channel with 500 μm height fins has been improved by up to 45.8 %. At the initial point of flow instability, the micro-channel with 500 μm height fins has the highest pressure drop fluctuation frequency, the highest surface wetting frequency, and the lowest pressure drop variation coefficient among the studied cases. However, the micro-channel with 600 μm height fins has the lowest pressure drop fluctuation frequency and highest pressure drop variation coefficient, hence experiencing the longest dry-out process among the studied cases.

Enhancement of turbulent heat transfer by using CuO nano-particle and twisted tape

AbstractA computational model is developed to investigate the convective heat transfer properties and the fluid flow characteristics of cupric oxide - water nano-fluid in a horizontal circular pipe aiming to provide insights into optimizing heat transfer in such systems. A twisted tape with varied twist ratios is inserted. This quantitative investigation used five Reynolds number from 4,000 to 12,000 under a uniform heat flux scenario of 25,000 W m−2. All experiments were performed as a single-phase fluid with cupric oxide values of 0, 0.4, 1, and 2% by volume. By reducing the twist ratio and increasing volume concentration, the average heat transfer coefficient of cupric oxide-water nano-fluid was improved. For a twist ratio of 4D, the maximum heat transfer improvement was 228% greater than the plain pipe. The presence of twisted tape with modest step ratios causes the friction factor to grow.

Prediction of the Flame Characteristics of an Industrial Gas Turbine Operated With CO2-Diluted Air Through a High-Fidelity Numerical Analysis: A Comparison Between Flamelet Generated Manifolds and Artificially Thickened Flame

Abstract In light of the global commitment to decarbonize industrial processes, carbon capture and storage (CCS) plays a pivotal role in mitigating greenhouse gas emissions from gas turbine (GT) power generation processes. Achieving an efficient GT–CCS coupling requires the employment of high percentages of exhaust gas recirculation (EGR) to maximize the CO2 content at the CCS inlet. Nevertheless, such operating conditions pose critical challenges for conventional combustion systems due to reduced oxygen levels associated with higher EGR, limiting engine operability. To address this challenge, the development of innovative technical solutions is essential to extend the combustor operational capabilities at high EGR rates. For this goal, a significant number of computational fluid dynamics (CFD) simulations are required to identify the flame stability limits across various EGR levels and burner designs. It is imperative, in this context, to minimize computational costs while maintaining high accuracy. In this work, a comprehensive comparative study of an extended version of the flamelet generated manifolds (FGM) and the artificially thickened flame (ATF) model is performed through a large eddy simulation (LES)-based CFD analysis. The investigation is performed within the context of an industrial lean-premixed burner manufactured by Baker Hughes, operating with natural gas and CO2-diluted air at atmospheric pressure. While the extended-FGM has been previously presented by the authors in a study on the same test rig under standard air conditions, the current work aims to extend its application to critical oxygen-depleted conditions, where near-blowout phenomena such as flame liftoff and length elongation may become significantly pronounced. Numerical validation is carried out through a direct comparison of the computed averaged heat release, representing the flame topology, with detailed OH* chemiluminescence images from a test campaign conducted by the technology for high temperature (THT) Lab of the University of Florence. The experimental data will serve as the primary benchmark for assessing the models’ effectiveness in capturing the main dynamics of such critical operating conditions. Furthermore, potential disparities in both thermal and flow fields at the burner exit region between the two models will be discussed.

Assessment of spatial distribution of schools in the northern area of Riyadh city

This paper aims to study the distribution of three types of schools in the northern area of Riyadh city in Saudi Arabia in order to uncover the aspects of imbalance distribution of schools over the 4 districts of the study area (Almalqa, Sahafa, Jasmine and Narges neighborhoods) in addition to assess the extent of compatibility between the number of schools in each district and the density of population residing in it. The used dataset is built up of mainly tow datasets for schools and districts covering the study area. This research has utilized MS Excel, ArcGIS and QGIS software and applied the Point-to-Polygon overlay to locate the three types of schools in their corresponding districts and three types of analysis were applied which are the average nearest neighbor, heat map, and district classification based on population ratio with the aim of exploring the clustering patterns of schools as well as classifying the districts based on the density of schools relative to population. The study concludes that there is a spatial disparity in the distribution of schools, mainly in terms of their density, in the different districts due to the variation in population. Moreover, a notable inequality of the distribution of schools with respect to the population has been found.

Investigation of heat transfer characteristics and optimization design of platen superheaters in the furnace of a 350 MWe supercritical CFB boiler

With the scale-up of circulating fluidized bed (CFB) boilers, the size of the platen heating surface within the furnace increases. Deformation, crack, and tube explosion of the platen heating surface threaten the safe and stable operation of CFB boiler. Large wall temperature deviation and overtemperature of partial tubes of heating surfaces are two of main reasons resulting in above problems. To identify the causes of large wall temperature deviation and decrease them, the heat transfer characteristics and wall temperature distribution uniformity of platen superheaters in the furnace of a 350 MWe supercritical CFB boiler were studied by experimental tests, and the structure of the high temperature superheater was optimized by numerical simulation to improve the temperature distribution uniformity. The steam parameters and wall temperatures of the platen superheaters were measured at boiler loads of 50 % BMCR, 75 % BMCR, and 100 % BMCR. The heat transfer coefficient, heat flux, and wall temperature uniformity of the platen superheaters were analyzed. At 100 % BMCR boiler load, the average heat transfer coefficient and heat flux of the medium temperature superheater IIs were 165.5 W/(m2·°C) and 56 kW/m2, respectively; while those of the high temperature superheaters were 179.7 W/(m2·°C) and 53.2 kW/m2, respectively. The wall temperature distribution uniformity among six medium temperature superheater IIs or six high temperature superheaters was relative good, while the temperature distribution uniformity of a single platen superheater required improvement. An optimized structure of the high temperature superheater was obtained from eight structures by numerical simulation, achieving a steam temperature deviation of less than 8 °C at the boiler load of 100 % BMCR.

Study on the inverse problem of thin slab continuous casting mold based on fluid-solid coupled heat transfer

The thin slab continuous casting (TSCC) process employs a funnel-shaped mold, introducing increased complexity to both the structure and heat transfer of the mold, as well as the cooling water channels. This paper presents a three-dimensional fluid-solid coupled model for calculating the heat flux in a thin slab mold. The model is calculated and validated based on temperature data collected from molds and cooling water in the plant. The results show that the deviations of the wide face average heat flux and cooling water temperature difference from the measured values are 3.49 % and 1.1 %, respectively, demonstrating good agreement. Moreover, the influence of the thin slab mold geometry on heat transfer is explored. The heat flux values calculated in this model are approximately 13 % lower than those in the simplified model in the upper part of the original funnel area, and 2–7% lower in the lower part. Therefore, this model reflects the heat flux's three-dimensional characteristics of the funnel-shaped mold, offering a novel approach to calculating the heat flux of the thin slab mold.