Varying Heat Input Research Articles

Optimizing heat transfer performance in two-phase closed thermosyphons: A novel design and experimental evaluation.

Effective heat dissipation is crucial in various thermal management applications, including electronics, renewable energy systems, and heating and cooling systems. Two-phase closed thermosyphons (TPCTs) are recognized for their efficient heat transfer and have been widely adopted in these fields. This study presents a novel design for a TPCT that incorporates a unique internal cone-shaped tube at the evaporator. This innovative feature aims to minimize vapor-liquid interaction within the main tube, potentially leading to enhanced heat transfer efficiency. The proposed TPCT is evaluated against a conventional design using water and ethanol as working fluids. Thermal performance is assessed under varying heat inputs (50W-250W) and filling ratios (40%, 55%, 70%, 85%). The results indicate that the optimal filling ratio depends on the working fluid. Water exhibits the best performance at 55% and 85% filling ratios, whereas ethanol achieves its optimum at 70%. Notably, at a 70% filling ratio with a 50W heat input, the novel TPCT design exhibits a significant 45.7% reduction in thermal resistance compared to the conventional design. As expected, increasing heat input reduces thermal resistance but also elevates operating temperatures for both TPCTs. Notably, the novel TPCT demonstrates a significant improvement in thermal performance compared to the conventional design, particularly when using ethanol as the working fluid.

Numerical investigation of effect of fill ratio and inclination angle on a U-shaped elliptical gravity heat pipe thermal performance

As electronic devices become increasingly compact, effective thermal management is crucial for performance. This study establishes a model of a U-shaped elliptical gravity heat pipe with dual heating ends and a single cooling end. Through computational fluid dynamics (CFD) simulations, the impacts of filling ratio and inclination angle on the thermal transfer capacity for the heat pipe were investigated. The results indicate that the evaporator surface temperature and thermal resistance of the heat pipe initially decrease and then increase with an increasing filling ratio. Within the inclination range of 10? to 90?, the evaporator surface temperature and thermal resistance gradually decrease. The optimal filling ratio is found to be 65%, and the optimal inclination angle is 90?. Furthermore, it was observed that higher heat input intensifies the effects of filling ratio and inclination angle affecting heat pipe thermal performance. These findings highlight the critical role of these parameters in optimizing heat pipe performance under varying heat inputs.

Experimental investigation and quasi-steady modeling of nucleate boiling in mini-channel thermosyphons

This study explores the understanding of two-phase cooling in thermosyphons using a quasi-steady state methodology during the boiling process. A thermosyphon is built as a passive loop to dissipate heat with an evaporator and a condenser. The evaporator is made of multiple mini channels (hydraulic diameter of 1.54 mm, length of 260 mm with 7 × 2 internal ports for a Confinement number of 0.55) with HFO-1336mzz(E) as the working fluid. Different heat loads (500 – 4000 W) are generated directly on the external contact surface of the evaporator to create all the different stages of boiling, from monophasic regime to steady nucleate boiling with the Onset of Nucleate Boiling transition. The temperature evolution inside the evaporator is measured at different heights and compared with a theoretical assumption of a quasi-steady state. A characteristic time depending on critical factors such as thermal mass is determined to model the temperature during a generated heat load. A good agreement between experimental measurements and the quasi-steady model is shown. Thus, this study emphasizes tracking the temperature evolution over time within the system. This dynamic perspective offers a nuanced understanding of the system’s response to varying heat inputs, transient phases, and the onset of boiling. This characterized local behavior provides an original insight into the boiling appearing inside mini-channels. It is shown that boiling is initiated by nucleation at a few specific sites and then propagates up to a critical length due to high vapor generation, introducing a thermal lag during the boiling incipience.

Effect of heat input on the mechanical and metallurgical aspects of double-pulse MIG welded IN 617

In this article, an attempt is made to analyze the influence of heat input in double-pulse metal inert gas (DP MIG) welding of Inconel 617 (IN 617). IN 617 plates were joined in the butt joint configuration with 1.2 mm diameter IN 617 filler wire. Three welding trials were conducted at different heat input, viz. 31.3, 37.1, and 41.5 J/mm. Weld quality was assessed using bead geometry, tensile strength, toughness, and hardness. The changes in mechanical properties were discussed using the optical microscope, scanning electron microscope with energy dispersion spectroscopy, and backscattered energy diffraction. Substantial changes were observed in the weld tensile strength for a small variation in heat input. Molybdenum segregation was observed in all the weld samples. At lower heat input, the tensile test was reduced by 31.62% compared with base metal. Similarly, for the medium and high heat input, the tensile strength was reduced by 25.13% and 49.59%, respectively. Weld had lower toughness compared with the base metal and no significant variation was observed in toughness to changes in heat input. Hardness of the weld at all three heat inputs was almost similar to base metal. Liquation cracks were seen in the partially melted zone. At higher heat input, the lack of sidewall fusion was observed along with liquation crack.

Optimizing Elemental Transfer Predictions in Submerged Arc Welding via CALPHAD Technology under Varying Heat Inputs: A Case Study into SiO2-Bearing Flux

With the advancement of the manufacturing industry, performing submerged arc welding subject to varying welding heat inputs has become essential. However, traditional thermodynamic models are insufficient for predicting the effect of welding heat input on elemental transfer behavior. This study aims to develop a model via CALPHAD technology to predict the influence of heat input on essential elements such as O, Si, and Mn when typical SiO2-bearing fluxes are employed. The predicted data demonstrate that the proposed model effectively forecasts changes in elemental transfer behavior induced by varying welding heat inputs. Furthermore, the study discusses the thermodynamic factors affecting elemental transfer behavior under different heat inputs, supported by both measured compositions and thermodynamic data. These insights may provide theoretical and technical support for flux design, welding material matching, and composition prediction under various heat input conditions subject to submerged arc welding processes when SiO2-bearing fluxes are employed.

Thermal performance prediction of radial-rotating oscillating heat pipe by a novel fusion model: A case study of application in grinding

High temperatures in rotating machinery and machining processes necessitate effective thermal management for improving efficiency. Radial rotating oscillating heat pipes (RR-OHPs) have shown potential in enhancing heat transfer during rotating machinery operation. To facilitate the application of RR-OHPs in rotating machinery, an accurate prediction of their thermal performance is essential. This paper proposes a so-called “fusion prediction model” that combines an algorithm called GA-LightGBM and grey prediction techniques to accurately predict the thermal performance of RR-OHPs under different parameters. The GA-LightGBM optimizes hyperparameters globally though population iteration, while grey prediction explores systematic patterns using limited information. The combination of these algorithms results in a high-precision prediction with a relative error of 10%. The dataset for the model is obtained by an experiment under varying heat inputs and rotating speeds. To illustrate the application of the fusion model, we study the design of an OHP grinding wheel for enhanced heat transfer in grinding processes. The results confirm the high thermal performance of the OHP grinding wheel maintaining the maximum grinding temperature below 300 °C. Overall, this proposed prediction model is expected to expand the application of RR-OHPs and provide valuable guidance for their implementation in engineering.

Effect of heat input on the microstructure and hardness of AISI 321 stainless steel welds using ER 347 filler metal

Stainless steel is widely used in various fields, one of which is AISI 321, which is used for high-temperature applications because of its high resistance to creep and intergranular corrosion. The type of filler metal and heat input on stainless steel welds play an essential role in determining the microstructure and mechanical properties of the welded joints. The purpose of this experiment was to evaluate the microstructure and mechanical properties of AISI 321 stainless steel welds with variations in heat input. This study is expected to explore the performance of this weld joint, which can be anticipated in relevant fields. The welding method used in this experiment was Gas Tungsten Arc Welding (GTAW) with ER 347 as filler metal. Welding was carried out on three samples with a heat input of 0.92 kJ/mm, 0.64 kJ/mm, and 0.52 kJ/mm, respectively. The tests included tensile strength, Vickers microhardness, and microstructure observations. The tensile test results showed that a fracture occurred in the Base Metal (BM) area, indicating that the strength of the weld joint was higher than that in the BM. The Vickers microhardness test results showed that the Weld Metal's hardness (WM) was the highest, followed by the Heat-Affected Zone (HAZ) and BM. The welding experiment that used three variations in heat input demonstrated that higher heat input lowered the hardness of the weld joint. The microstructure observation results around the fusion line demonstrated the presence of step and ditch structures. The ditch structure indicates intergranular corrosion.

Microstructure and Micro-texture Development of Variable Frictional Heat Input Friction Stir Welded Joints of Laser Powder Bed Fusion-Made AlSi10Mg Plates

Microstructure and Micro-texture Development of Variable Frictional Heat Input Friction Stir Welded Joints of Laser Powder Bed Fusion-Made AlSi10Mg Plates

Evaluation of methods used for simulation of heat-affected zones in duplex stainless steels

The weldability of duplex stainless steels partly depends on the ferritization of the high-temperature heat-affected zone (HT-HAZ). This area is rather narrow, and it can be challenging to visualize and determine its actual impact on the properties. To address this, various methods were applied to study the grain growth and austenite reformation in the HT-HAZ of the lean duplex grade UNS S32101. Thermo-mechanical Gleeble® simulations were conducted at 1360 °C with different holding times and cooling rates. Subsequently, the grain size and ferrite content were measured on polished and etched cross-sections. Bead-on-plate welds were performed on the same heat of 6-mm plate thickness using the gas tungsten arc welding (GTAW) process. The shielding gas was Ar + 0–8% N2 to illustrate the effect of nitrogen additions on the HT-HAZ morphology. The arc was either stationary, welding at one spot for 0.5–120 s, or travelling at different speeds to generate varying heat inputs and temperature gradients. The thermo-mechanical simulations approximated the results obtained by travelling arc welding and allowed for a more comprehensive investigation. Stationary arc welding was not suitable for HT-HAZ studies as it quickly caused nitrogen depletion and resulted in significantly higher ferrite contents compared to the travelling arc welds.

Numerical Investigation on Thermal Performance of Nanofluid-Assisted Wickless Heat Pipes for Electronic Thermal Management

Abstract Heat pipes are passive heat transfer systems and serve as an effective thermal management solution for electronic devices. The adaptability of heat pipes makes these suited for a wide application range, especially in the field of electronic thermal management. The current study highlights the transient numerical analysis of wickless heat pipes (thermosyphons) for the thermal management of electronic devices. The thermal performance of the thermosyphon is analyzed using both copper oxide (CuO) and aluminum oxide (Al2O3) nanofluids with their concentrations at 1% and 5%. Deionized (DI) water is employed as a reference case for comparison. The study is carried out for variable heat inputs to the thermosyphon ranging 10–50 W for a time interval of 30 s. The idea is to analyze the effect of the evaporator heat input and the nanoparticles concentration on the temperature, heat transfer coefficient, thermal resistance, and effective thermal conductivity of the heat pipe. The results indicate that CuO nanoparticles at a 5% concentration lead to a maximum thermal resistance reduction of 4.31% at 50 W, while alumina nanoparticles at the same concentration lead to a more substantial reduction of 6.66% at the same heat load. The evaporator temperature varies between 377.52 K to 374.99 K using deionized water, and 376.95 K to 374.29 K using CuO nanofluid (at 1% concentration). The heat pipe's evaporator attains its highest convective heat transfer coefficient (437.91 W/m2K) by using alumina nanofluid with 1% nanoparticle concentration at 50 W. Moreover, the effective thermal conductivity of the heat pipe is enhanced by 5% and 7% for copper oxide and aluminum oxide nanofluids (with 5% concentration), respectively, at 50 W. Thus, the nanofluids play a significant role in improving the efficiency and reliability of electronic components. These findings demonstrate the potential of using the nanofluids in thermosyphons to enhance their thermal performance in electronic cooling applications.

Investigation of Single-Phase Immersion Cooling for Modern Data Centers

Compact servers with a high energy density are the result of the telecommunications industry's rapid advancement. Innovative cooling solutions are required due to the expanding scale of data centers and related cooling needs. Servers in the data center might be cooled via immersion cooling by immersing them in a thermally conductive die electric fluid. In this study, three distinct dielectric liquids were used with variable circulation rates to examine the effectiveness of single-phase immersion cooling with varying heat inputs of 300, 400 and 500 Watts. Deionized water, white mineral oil and propylene glycol were the three dielectric fluids being considered, at circulating rates of 1, 2 and 3 litres per minute. Among the three fluids tested, deionized water consistently outperformed the others by maintaining the lowest outlet temperature across various heat inputs and flow rates. The average heat transfer coefficient for deionized water was calculated as the highest, with a value of 349.29 W/m²·K. Propylene glycol had an intermediate heat transfer coefficient, which was 194.69 W/m²·K, and mineral oil exhibited the lowest heat transfer coefficient at 74.44 W/m²·K.

Optimizing heat transfer efficiency in electronic component cooling through fruit waste-derived phase change material

This study focuses on the development and evaluation of heat sinks designed for the thermal management of electronic components operating under low-temperature conditions. Two distinct heat sink configurations were investigated: one featuring a hollow structure without fins and the other incorporating equidistant triangular fins. These heat sinks were subjected to varying heat input levels of 35 W, 40 W, and 45 W. To enhance thermal performance, various thermal enhancement techniques were employed, including the integration of phase change materials, graphene nanoparticles, and nanoparticles coated with dragon fruit extract. The results of this investigation revealed significant improvements in the heating-cooling cycle. It was observed that the heating effectiveness of the heat sink increased by 23 %, 11 %, and 6.8 %, respectively, when employing dragon fruit extract-coated nanoparticles in conjunction with phase change material. After increasing the heat input to 40 W, the heating and cooling cycle of the heat sink containing PCM and without fins was reduced by 18 %. Coating the nanoparticles with dragon fruit extract reduced the heating and cooling cycle time by 37 % compared to the heat sink without fins and PCM included. Further optimisation studies substantiated these findings, affirming the efficacy of the proposed approach. In summary, incorporating dragon fruit extract-coated graphene nanoparticles demonstrated a noteworthy enhancement in the heating-cooling cycle, proportionate to the applied heat input, within the context of finned heat sinks employed for electronic component thermal management.

Effect of reducing heat input on autogenous TIG welding of Ti–6Al–4V alloy

3 mm-thick Ti–6Al–4V alloy plates were welded in butt joint configuration through autogenous TIG welding method using a trailing gas shielding arrangement. After attaining full penetrated weld joint with appropriate heat input, subsequent experiments were conducted by reducing the heat input, which was obtained through combination of higher welding current and scan speed. An in-depth microstructural analysis of the weld joint executed under different heat input conditions shows a strong correlation with the microhardness, tensile strength, and flexural strength of the weld joint. A significant improvement in the mechanical properties of the weld joint was perceived for employing lower heat input. Alteration in the primary-α, primary-β, and martensite-α phases, due to the variation in heat input, amended the mechanical properties of the weld joint under lower heat input condition. With the reduction of heat input from 0.406 to 0.232 kJ/mm, the tensile and flexural strengths of the weld joint increased from 1020 to 1070 MPa, and from 1015 to 1950 MPa, respectively. The tensile strength of the joint reached up to 98% of the base material at minimum heat input (0.232 kJ/mm). The experimental results show the potential of TIG welding for joining Ti–6Al–4V alloy under low heat input condition.

İmalat Ön Astar Kaplamanın S235JR Çeli̇ği̇ni̇n MAG ve SAW Yöntemleriyle Kaynaklanabi̇lirliği Üzeri̇ndeki̇ Etki̇sinin Karşılaştırmalı Olarak İncelenmesi̇

The outcome of a welding process relies on various factors, one of which is the heat input at the welded joint. Consequently, the thermal conductivity of the plates to be welded holds significant importance, just like the selection of the welding technique. This research investigates the impact of applying Metal Active Gas (MAG) and Submerged Arc Welding (SAW) methods on differently coated (shop-primer) plates, as well as un-coated S235JR structural steel plates. The study explores how these applications, with varying heat inputs, affect the mechanical and microstructural properties of the materials. Filler metal of SG2/S2 non-alloy steel grade wires was employed. The variable parameters chosen included surface conditions, coating thickness, and heat input. It was observed that altering the coating thicknesses and welding methods led to welding defects. Non-destructive tests indicated that surface conditions and welding methods somewhat influenced the weld joint. Specimens with a thickness of 75 µm exhibited poor performance in tensile, impact, and bending tests. Fractography studies validated these findings.

Microstructural evolution and mechanical properties of rapidly solidified thin-strip continuous cast AA5182 Al-Mg alloy under varying heat inputs in friction stir welding

Microstructural evolution and mechanical properties of rapidly solidified thin-strip continuous cast AA5182 Al-Mg alloy under varying heat inputs in friction stir welding

Simultaneous power generation and heat recovery within a novel thermosyphon heat pipe: An experimental study and correlation development

The unique concept of generating electricity from a thermosyphon heat pipe (THP) utilizing an oscillating magnet in the adiabatic section was successfully examined experimentally. Generating electrical power while the THP operates is a revolutionary approach to improving its performance. In this regard, an energy harvesting module, including a magnet, was designed, built, and installed into the adiabatic section of the THP. The investigation was performed for four filling ratios ranging from 10 to 40%, while water served as the working fluid. In addition, the effect of variation of heat input on the performance of both THP and oscillating magnet thermosyphon heat pipe (OM-THP) was studied. Results demonstrated a negligible difference between the thermal resistances of OM-THP and THP before dry-out. The presence of the oscillating magnet causes dry-out to occur sooner; however, OM-THP still has electrical power generation during stable operation in the range of 50–125 W of heat inputs. According to the results, raising the filling ratio delays the drying of OM-THP. At 20% filling ratio and 100 W heat input, the highest average peak-to-peak open circuit voltage was 1 V. Besides, new correlations are presented to predict the induced voltage and thermal performance of the THP and OM-THP. The proposed correlations can predict the thermal resistances of THP and OM-THP, and the induced voltage of OM-THP with RSQ values of 0.91, 0.79, and 0.94, respectively.

Comparative Analysis of Welding Mechanical Properties FCAW Welding Joint of A36 and A53

A36 and A53 steels are low carbon steel with relatively similar carbon percentage, respectively 0,25-0,30% and 0,25-0,29%. Both steels are often used within the marine industry. The objective of this research is to figure out the effect of the variation of the groove angle and the heat input to the process of welding two different steel plates towards a metallography, tensile, and bending test with E71T electrode, as well as figuring out the groove angle and heat input to weld 18 mm thick steel plates. The variation of the groove angle used are 55°, 60°, and 70° with heat input variation of 140 and 180 A. Results of this experimental study shows that specimen with groove angle 70° and heat input 180 A with the largest sum of HAZ length, which is 8,4 mm, as well as the largest perlite phase, which are respectively, 67% within A36 base metal, 65% on A36 HAZ, 62% on weld metal,63% on A53 HAZ, and 66% on A53 base metal. The largest open defect value in bending tests is 1.87 mm owned by specimens with groove angle of 55° and heat input of 140 A.

Heat transfer coefficient and thermal performance of heat pipe with R134a/mineral oil nanodiamond+Fe3O4 hybrid nanorefrigerant

Experimental research has been done on the heat transfer coefficient and thermal performance of heat pipe operating with R134a/mineral oil (5:1% weight percent) based nanodiamond+Fe3O4 hybrid nanorefrigerants. The in-situ growth approach was used to create the hybrid nanoparticles, which were subsequently characterized by X-ray diffraction. Using a vibrating sample magnetometer, the prepared sample magnetic measurement was determined. The studies were conducted with varying heat inputs of 100, 150, and 200 W and with particle loadings of 0.1%, 0.5%, and 1.0%, respectively. The results show that when using hybrid nanofluids instead of base fluid, the wall temperatures at the evaporator and condenser sections of heat pipe are lower. At a heat supply of 200 W, the average temperature in evaporator and condenser sections are reduced by 30.08% and 19.21%, respectively. At [Formula: see text] = 1.0% vol. loading and 200 W, the thermal resistances in the evaporator and condenser sections drop to 24.58% and 21.74%, respectively. In comparison to the base fluid, the heat transfer coefficients of the evaporator and condenser are greater to 37.08% and 30.24%, respectively, at a heat input of 200 W. The thermal performance of the heat pipe is enhanced by employing the hybrid nanoparticles based nanorefrigerant, and it is also increased with increasing particle loadings.

Microstructures and properties of a novel 115 mm thick 08Cr9W3Co3VNbCuBN heat-resistant steel tube joints welded by shielded metal arc welding

A novel heat-resistant steel tube, 08Cr9W3Co3VNbCuBN (G115), is the primary choice for crucial components of ultra-supercritical (USC) thermal power plants. In this paper, the 115 mm thick G115 steel tube was welded successfully by shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW), and the microstructures and mechanical characteristics of joint were studied. The results indicated that the microstructure of the weld zone (WZ) was mostly ferrite and martensite, and the content of ferrite at the weld root was 19.9% lower than that at the weld center. However, at the weld toot the grain size was reduced by about 20%, and the content of M23C6 was increased by 30.9%. Previous austenite grain boundaries (PAGBs) and martensite occurred in the heat-affected zone (HAZ) because to varying heat input, and a tiny quantity of fine Cu-rich phase precipitated from the root of HAZ. The hardness distribution of joint from the base metal (BM) to WZ demonstrated a low to high phenomena, with the average hardness of the BM being 235 HV and the average hardness of WZ being enhanced by 1.16 times. The fine secondary phases precipitated and diffused in the WZ, therefore reinforcing the martensite and improving its mechanical properties. The average impact absorption energy of the weld zone was 43.89 J, and the average impact energy of the HAZ was 54.57 J, both of which were sufficient to fulfill the actual standard (>31 J). The fracture morphology revealed a complex fracture mechanism with dimples and cleavages on the surface of joint, and the toughness was positive. The causes of the decrease in hardness and the rise in toughness might be the Cu-rich phase precipitated from the root of HAZ. Furthermore, the corrosion resistance of the welded joint (WZ: Icorr = 10.542 μA cm−2, HAZ: Icorr = 11.241 μA cm−2) was lower than that of the BM (Icorr = 9.4844 μA cm−2).

Increasing the Corrosion Resistance in the UNS S32750 Super Duplex Steel Welded Joints through Hybrid GTAW-Laser Welding and Nitrogen.

The development of techniques to improve the welding of super duplex steels is necessary in order to ensure that the phase balance and properties of the material are not affected during this process. Hybrid arc-laser welding is a perfect combination of the advantages of both processes, producing deeper weld beads with more balanced phases than the pulsed laser process. Here, the objective was to improve the corrosion resistance of UNS S32750 weld beads by increasing the volumetric austenite percentage in the fusion zone (FZ) with a hybrid process of GTAW (gas tungsten arc welding) and pulsed laser Nd-YAG (neodymium-doped yttrium aluminum garnet). Welds were performed in bead on plate conditions with fixed laser parameters and a varying heat input introduced through the GTAW process. Additionally, welds within a nitrogen atmosphere were performed. After base metal characterization, an analysis of the FZ and heat affected zone were performed with optical microscopy, scanning electron microscopy and critical pitting tests (CPT). The synergy between the thermal input provided by the hybrid process and austenite-promoting characteristic of nitrogen led to a balanced volumetric austenite/ferrite fraction. Consequently, the results obtained in CPT tests were better than conventional welding processes, such as laser or GTAW solely.