Double Heat Research Articles

Influence of a Novel Double Tempering Process on the Microstructure and Mechanical Properties of Cu-Alloyed Austempered Ductile Iron with Possible Nano (Micro)-Characterization Using Neutron Beam Techniques

In this paper, a novel method for the double heat treatment of ductile iron was applied. Ten sets of specimens (three specimens in each set) of ductile cast iron (DCI) containing 0.51% wt. Cu were prepared and converted to austenitic ductile iron. All specimens were austenitized at 850 °C for 60 min and annealed at 420 °C, 331 °C and 250 °C for 120, 68 and 30 min, respectively. Five sets of samples were then annealed at 500 °C for 60 min, creating a novel double heat treatment process for annealing. Finally, all specimens were slowly cooled in air at ambient temperature. Tensile strength, hardness and elongation were measured in all specimens to compare the specimens with and without subsequent tempering. A microstructural analysis was also performed, which showed that the microstructure changed for the specimens that were subsequently tempered with. The results show that specimens with subsequent tempering have slightly higher hardness, a small decrease in tensile strength and significantly higher elongation. In addition, specimens with subsequent tempering exhibit more uniform mechanical properties compared to specimens without subsequent tempering. The use of neutron beam techniques was proposed to further characterize the newly formed microstructure after subsequent tempering.

Numerical investigation of laminar heat transfer and fluid flow characteristics of Al2O3 nanofluid in a double tube heat exchanger

PurposeThe purpose of the study is to numerically investigate the characteristics of laminar heat transfer and fluid flow in a double tube heat exchanger (DTHE) using water-aluminum oxide (Al2O3) nanofluid. The study examines the effects of nanofluid in both counter and parallel flow configurations. Furthermore, an exergy analysis is conducted to assess the impact of nanofluid on exergy destruction.Design/methodology/approachThe single-phase method has been used for Al2O3 nanoparticles in water as base fluid in a laminar regime for Reynolds numbers from 400 to 2,000. The effects of nanoparticle volume fractions (0 to 0.1), Nusselt number, Reynolds number, heat transfer coefficient, pressure drop, performance evaluation criteria (PEC) and the impact of counter and parallel flow direction have been studied.FindingsThe findings indicate that the incorporation of nanoparticles into the water enhances the heat transfer rate of DTHE. This enhancement is attributed to the improved thermal properties of the working fluid and its impact on the thermal boundary layer. Nusselt number, heat transfer coefficient, and PEC increase by approximately 19.5%, 58% and 1.2, respectively, in comparison to pure water. Conversely, the pressure drop experiences a 5.3 times increase relative to pure water. Exergy analysis reveals that nanofluids exhibit lower exergy destruction compared to pure water. The single-phase method showed better agreement with the experimental results compared to the two-phase method.Originality/valueDimensionless correlations were derived and validated with experimental and numerical results for the Nusselt number and PEC for both counter and parallel flow configurations based on the Reynolds number and nanoparticles volume fraction with high accuracy to predict the performance of DTHE without performing time-consuming simulations. Also, an exergy analysis was performed to compare the exergy destruction between nanofluid and pure water.

Assessment of cooling performance of mini/micro-channel stacked double layer heat sink

A study is accomplished here to investigate the performance of a novel double-layer mini/micro-channel stacked heat sink (DL-MMCHSHS). The hydraulic diameter and aspect ratio of mini-channel heat sink are 0.12 cm and 3, respectively. The width of the fins between two channels is 0.04 cm. The total width of two runners is the same, and its width is 1.44 cm. The heat dissipation potential of this new type of heat sink is investigated. It was observed that the pressure loss is reduced by using the DL-MMCHSHS instead of a single-layer micro-channel heat sink (SL-MCHHS). The reduction in the pressure loss reduces the pumping power, which leads to decrease in operating costs of the system. For the total flow rate of 345.69 cm3/min, the pressure loss reduces about 35.41% by using the DL-MMCHSHS instead of a SL-MCHHS. The uniformity index in the range of 0.077 to 0.192 is achieved in this study. For the total flow rate of 346.64 cm3/min, the uniformity index enhances about 60% with boosting the flow rate ratio from 0.5 to 3.5. For the total flow rate of 1039.26 cm3/min, the thermal resistance increases about 76.22% as the flow rate ratio increases from 0.5 to 3.5.

Comparative Experimental Study on Effect of Copper Wire Helical Wound Steel Tube with 2.5” Full Length Insert on Performance of Double Pipe Steel Tube Heat Exchanger

Abstract: A comparative experimental study was conducted to explore the hydrothermal behavior of a double tube heat exchanger with copper wire helical wound steel tubes and plane steel tubes with and without twisted tap inserts of pitch length 2.5 inches. In comparison to helical tubes, corrugated tubes, and many other more compact tube type heat exchangers, straight tube heat exchangers offer advantages since the construction of the heat exchanger tubes is easier. In the current work, the fluid-to-fluid heat exchange is considered, with a flow rate ranging from 15 to 75 liters/hour. Constant wall temperature or constant heat flux ideas are used in the majority of investigations on heat transfer coefficients. The efficiency, overall heat transfer coefficient, and impact of hot water flow rate with constant cold water flow rate for straight steel tube and copper wire helical wrapped steel tube heat exchangers in parallel flow and counter flow configurations were investigated and compared. Utilizing a 2.5" full length clockwise twisted tape insert, both layouts were created. The measurements were carried out in a constant state. When the hot water flow rate is increased while maintaining the cold water flow rate constant, the efficiency of the heat exchanger drops for both the straight steel and the copper wire helical wound steel tube. Compared to a plane steel tube heat exchanger, the copper wire helical wound steel tube heat exchanger has a better efficiency. The test findings demonstrate that inserting inserts causes pressure drop. With 2.5" clockwise twisted tape inserts wrapped in helical copper wire, steel tube was able to transmit heat more quickly than other arrangements.

Environmental, economic and exergy analysis of separation of ternary azeotrope by variable pressure extractive distillation based on multi-objective optimization

In this work, the ternary azeotrope of tert-butyl alcohol/ethyl acetate/water is separated by extractive distillation (ED) to recover the available constituents and protect the environment. Based on the conductor like shielding model and relative volatility method, ethylene glycol was selected as the extractant in the separation process. In addition, in view of the characteristic that the relative volatility between components changes with pressure, the multi-objective optimization method based on nondominated sorting genetic algorithm II optimizes the pressure and the amount of solvent cooperatively to avoid falling into the optimal local solution. Based on the optimal process parameters, the proposed heat-integrated process can reduce the gas emissions by 29.30%. The heat-integrated ED, further coupled with the pervaporation process, can reduce gas emission by 42.36% and has the highest exergy efficiency of 47.56%. In addition, based on the heat-integrated process, the proposed two heat pump assisted heat-integrated ED processes show good economic and environmental performance. The double heat pump assisted heat-integrated ED can reduce the total annual cost by 28.78% and the gas emissions by 55.83% compared with the basis process, which has a good application prospect. This work provides a feasible approach for the separation of ternary azeotropes.

Numerical analysis of fluid type and flow mass rate on logarithmic temperature difference and heat transfer coefficient of double pipe heat exchanger

This CFD and statistical article aims to evaluate the impact of fluid type and flow mass rate on the log-mean temperature difference (ΔTLM) and the heat transfer coefficient (Ushell) in a double tube heat exchanger (DPHEX) using computational fluid dynamics (CFD) and statistical analysis. ANSYS Fluent software was utilized to conduct CFD calculations. CFD analyses were implemented using Taguchi L8 orthogonal array containing two variables such as the fluid types and the flow mass rates. The levels of fluid types were considered as water-liquid, ethylene-glycol, engine-oil, and benzene-liquid. The levels of fluid types were decided as 1.1 kg/s to 1.5 kg/s. To determine the optimal levels of variables and their impacts on the ΔTLM and Ushell in DPHEX, analysis of Signal to Noise (S/N) ratio was employed. Analysis of Variance (ANOVA) was also utilized to decide the effective variables and their percentage contribution rates on the outcomes. The CFD result obtained using the optimum levels of variables were compared with Taguchi estimation result. According to the study, the highest effects were obtained using ethylene-glycol, engine-oil, water-liquid, and benzene-liquid on the highest log-mean temperature difference values, respectively. In addition, the highest heat transfer coefficient values were found utilizing water-liquid, benzene-liquid, ethylene-glycol, and engine-oil, respectively. Increasing flow mass rate from 1.1 kg/s to 1.5 kg/s causes an increase in both outcomes. The study provides a reference for resolving issues that may arise in the production of experimental DPHEXs.

Double step heating synthesis of MIL-101(Cr) composites for water harvesting applications

Energy storage is a valuable mechanism for managing fluctuations in energy demand by allowing the distribution of energy production needed during peak demand over a more extended period. Thermal energy storage is among the most valuable categories of energy storage. The optimal sorbent material must satisfy thermal, physical, chemical, and environmental requirements for designing sorption heat storage systems. MIL-101(Cr) is a Metal-Organic Framework (MOF) with remarkable properties such as a high surface area, hydrothermal stability and good water sorbent capacity that make it a potential candidate as a working sorbent. Their physicochemical properties can be modulated by functionalizing the organic linker or by modifying its structure, improving the interaction with the target sorbate, mainly environmentally friendly and non-toxic sorbates such as water. However, good water sorption capacity is not the only characteristic to be considered when selecting the sorbent material for sorption heat storage systems. Here, we propose an alternative method to obtain a sorbent material with the objective of reducing the reaction time and achieving a good balance between the physical properties of the material, such as the density and the thermal conductivity, without substantially decreasing its water uptake capacity. For this aim, we show that structural modification of MIL-101(Cr) induced by CaCl2 and graphene oxide (GO) can improve the water sorption capacity and optical properties compared to the pristine sorbent. The MIL-101(Cr)/GO/CaCl2 composite had a higher water uptake capacity of 1.08 gwater g−1composite-1, even compared with MIL-101(Cr)/CaCl2 composite with a water uptake capacity of 0.68 gwater g−1composite. Additionally, MIL-101(Cr)/GO and MIL-101(Cr)/GO/CaCl2 sorbents tend to absorb light toward the near-infrared region and increase the temperature around twice as much compared to sorbents without GO when illuminated with a flash lamp. These results demonstrate that GO added at the MIL-101(Cr) structure allows a better distribution of CaCl2 in the MIL-101(Cr) pores and it may be advantageous in the water desorption process making use of renewable infrared radiation sources such as solar energy.

Bibliometric Study of Double Pipe Helical Coil Heat Exchanger

Bibliometric Study of Double Pipe Helical Coil Heat Exchanger

Numerical investigation and experimental verification of topological optimized double-layer mini-channels

Double-layer micro/mini channel heat sinks have great potential in the thermal management for integrated chips. In this work, two bi-objective optimization design of mini-channels is implemented using the variable density topology optimization method to get two topological single-layer mini-channel heat sinks (SL-MHSs). Among them, the SL-MHS obtained with the minimization of average temperature and power dissipation as the optimization objectives is named S1, while the SL-MHS obtained with the minimization of temperature variance and power dissipation as the optimization objectives is named S2. Then, S1 and S2 are used as the upper/lower layer of the double layer mini channel heat sink (DL-MHS), respectively. Therefore, four different topological DL-MHSs including D11, D12, D21 and D22 are achieved by assembling S1 and S2. Subsequently, the flow and thermal characteristics of the four topological DL-MHSs and conventional straight DL-MHS (C1) are studied numerically. The results show that when Re = 315, compared with C1, the maximum temperature of the substrate of the topological DL-MHSs (D11, D12, D21 and D22) can be respectively reduced by 17.0,16.6, 14.0 and 13.6 K, while the Nusselt number can be improved by 27.3%, 26.6%, 27.1% and 26.4%, respectively. Additionally, the total thermal resistance is also reduced at least 20%. However, although topological DL-MHSs produce higher pressure drop penalty, the PEC values of topological DL-MHSs are always greater than 1, which indicates that the new topological DL-MHSs is meaningful. Finally, the flow and thermal characteristics of the best one D11 are investigated experimentally. The simulated results agree well with the experimental results.

Thermal and economic investigation of straightand U-bend double tube heat exchanger withcoiled wire turbulator

Thermal and economic investigation of straightand U-bend double tube heat exchanger withcoiled wire turbulator

Experimental and numerical study on the distribution of temperature field and residual stress in a multi-pass welded tube joint of Inconel 617 alloy

The purpose of this study is to compare the residual stress generation during hot wire gas tungsten arc welding (HW-GTAW) welding and conventional gas tungsten arc welding (GTAW) in a multi-pass pipe weld of a nickel-based superalloy. HW-GTAW yields better mechanical properties at low heat input than conventional GTAW, and decreases the accumulation of residual stress significantly. The distribution of residual stress developed in the through-thickness direction is determined experimentally using the Deep hole drilling method. As a result of the analysis, it was observed that the highest residual stress arises in Fusion Zone (FZ) and Heat Affected Zone (HAZ). In the case of conventional GTAW the hoop stress was observed to be tensile and distributed over 70% of the weld whereas only 20% of the weld is found to be under tensile hoop stress in the case of HW-GTAW along the weld center. The results show that shrinkage at the weld HAZ region affects the stresses produced at the cylinder's outer surface. The bending effect created during the welding process is primarily responsible for the distribution of residual stresses in the weld zone. A comprehensive numerical analysis has been carried out using ABAQUS software to predict the level of thermal and residual stresses in the weld zone, FZ, and HAZ in the case of both welding process. A 2D finite element models have been developed to simulate the welding process using the ABAQUS FE tool based on coupled thermal-mechanical analysis. A double ellipsoidal heat source model has been developed using a DFLUX subroutine file to simulate the welding process during the numerical analysis. The predicted residual stresses were validated with the experimentally obtained results.

Study on the Morphology, Microstructure, and Properties of 6082-T6 Aluminum Alloy Joints in MIG Welding

In this paper, metal inert gas (MIG) welding of 6082-T6 aluminum alloy with a thickness of 4 mm was simulated using a double ellipsoidal heat source. Based on the simulation results, the evolution of the microstructure, the strengthening mechanism of mechanical properties, and the corrosion characteristics of the welded joint were studied further. The thermal cycle curve of the welded joint was obtained through numerical simulation. When the heat input was 2.34–2.75 KJ/mm, the temperature of the welded joint reached the melting point of the material. With the increase in welding heat input, the weld metal (WM) organization changed from the dendrite to the cellular crystal transformation and presented a uniform distribution. The precipitation of the strengthened phase was inhibited at 2.75 KJ/mm. When the heat input changed from small to large, the tensile strength and toughness first increased and then weakened. Dimple distribution of tensile fractures was observed with a scanning electron microscope. When the welding heat input was 2.57 KJ/mm, the mechanical properties of the joint were the best. The tensile strength can reach 76.62% of the base material, and the elongation after breaking can reach 59.38% of the base material. However, it was concluded through studying electrochemical corrosion that the corrosion resistance of welded joints under this parameter was the worst. This may be caused by the presence of Cu, Fe, Si, Mg, and other compounds, and was proven to be Mg2Si through EDS analysis.

Study on Morphology, Microstructure and Properties of 6063-T6 Aluminum Alloy Joints in MIG Welding

In this paper, a metal inert gas (MIG) shielded welding method was used for high-quality welding of 6063-T6 aluminum alloy sheet with a thickness of 2.5 mm. The welding process of MIG welding was accurately simulated and the welding temperature field and thermal cycle curve were calculated using a combination of Gaussian body heat source and double ellipsoidal heat source. As the welding current increased from 75 A to 90 A, the reinforcing phase precipitated under the microstructure of the joint gradually became larger and re-solidified into the body, resulting in a reduction in mechanical properties. When the welding current is 85 A, the pitting resistance of weld forming and weld area reaches its optimum. At this time, the tensile strength of the joint is up to 110.9 MPa, the elongation is up to 16.3% and the Vickers Microhardness is up to 46.9 HV.

Estimation of heat source model parameters for partial penetration of TIG welding using numerical optimization method

Heat source parameters have a greater influence on the accuracy of numerical modelling for predicting residual stress and temperature field. Experimental measurements of stress and temperature during arc welding are cumbersome due to dynamic transfer of heat happening in a very short span of time. So, for modelling such a high temperature process, determining the heat source model parameters are critical. In this article, a novel method for figuring out the double ellipsoid heat distribution model’s heat source parameters is demonstrated. Here, finite element analysis (FEA) is done to predict the weld bead dimensions, thermal and structural cycles of tungsten inert gas (TIG) welding of AISI S304 stainless steel plates. 25 different sets of heat source parameters are generated for 100 and 120 A input power separately. Using this generated values, weld bead dimensions are determined from the simulation. The optimization is done with the Taguchi technique taking root mean square error (RMSE) value of heat source parameters and measured weld bead dimensions as response parameters. The model is validated using experimental data and the effects of each parameter on weld pool formation during TIG welding are also studied. Optimum values of heat source parameters for stainless steel AISI 304 at 100 A welding current are 2.3283, 2.3687 and 2.667, respectively, and that for 120 A weld current are 2.5909, 2.613 and 3.4949, respectively. The prediction of temperature and welding residual stress (WRS) distribution using optimizing heat source model parameters shows closer approximation with experimental results. The demonstrated model is very much reliable and simple to predict the heat source parameters for TIG welding with partial penetration with a very lesser number of operations and minimum error.

Development and application of a new calculation method for double spiral ground heat exchangers

This study provides a new calculation method for double spiral pipe ground heat exchangers (GHEs) and involves the combination of the analytical, infinite line source (ILS), and infinite cylindrical source (ICS) models with the capacity resistance model (CaRM). Method adopts the concept of fin efficiency, enabling it to calculate underground temperature changes easily and accurately, followed by integration into a simulation tool for ground source heat pump (GSHP) systems. Verification was done by comparing simulation results with actual operating data, measured from a zero-energy building (ZEB) in Sapporo, Japan. Analyses conducted using the new calculation method prove that simulation results can be obtained with increased precision and validity. Under conditions of instantaneous large heat injection, significant differences were observed between the simulation and the actual measurements during the initial 50 h. The number of temperature nodes in the network was increased to effectively reduce the error between simulations and measurements. Moreover, it was seen that the efficiency of double spiral pipe GHEs can be potentially improved by shortening the spiral pitch. This study thus confirms that the proposed new calculation method can be applied to future designs of GSHP systems by using thermal piles with double spiral pipe GHEs.

Numerical Simulation of Welding Temperature Field, Stress Field, and Strain Field of Fillet Joint in Different Welding Sequence

For welding temperature field, stress field, and strain field in fillet joints, using the double ellipsoid heat source, the ABAQUS software platform is used to simulate and analyze the welding process of fillet joints with four different application sequences. By setting up observation points, the study analyzed the distribution of the temperature field, stress field, and strain field of the simulated welding process for these four application cases. The results show that in the vertical weld direction, the welding sequence has a large effect on the transverse residual stress; the use of isotropic welding, butt weld first and then welded fillet weld program, the maximum total deformation and angular deformation produced are the smallest.

Performance improvement of a double tube heat exchanger using novel electromagnetic vibration (EMV) method in the presence of Al2O3-water and CuO-water nanofluid; An experimental study

In this research, the novel approach of the electromagnetic vibration (EMV) method was utilized for the first time to increase heat transfer in a double-tube heat exchanger (DTHEX). In this method, a magnetic turbulator (comprising a magnet and an oscillator) was installed inside a central tube that vibrated using an AC magnetic field. The influences of various parameters such as the geometry of the oscillator, magnet position, employing nanofluids, and fluid flow were assessed on the thermal-frictional behavior. The thermal enhancement factor (TEF) was assessed to select the optimal option. The studied options were economically evaluated based on energy efficiency. According to the results, the maximum heat transfer rate could be achieved when the magnet is positioned at 0.374. L from the tube inlet. The highest value observed for overall heat transfer was related to CuO-water 1% nanofluid, which was 277.5% more than simple heat exchanger. Also, the findings showed that heat transfer can be increased up to 13.3 times the energy used and reached to TEF = 3.92, which is a very significant number. Regarding the high potential of the EMV in reaching high thermal performance, it can be utilized as a game changer to save materials, energy, and compaction of the heat exchangers and solar systems.

Thermodynamic appraisal of utilizing compressor in double effect absorption heat transformer

In the current appraisal, three various designs of employing compressors in double-effect heat transformers are presented and evaluated from exergy and energy standpoints and collated with the simple configuration of mentioned designs. Water-LiBr is utilized as an operating fluid in noticed systems. As a function of the unit temperatures, the gross temperature lift, pressure ratio (R),and the efficiency of the economizer, a numerical model is also introducedto prognosticatethe irreversibility, exergy coefficient of performance (ECOP),coefficient of performance (COP), and the exergy destruction in each and every one of the key components (EF). The findings show that the generator has the highest exergy destruction, accounting for around 46.06% of the total exergy destruction. Additionally, a decrease in the temperature of the absorber increases the ECOP and COP. The outcomes indicate that systems utilizing water-LiBr as operating fluid have a higher outlet temperature of the absorber as well as higher condenser temperature and lower coefficient of performance (COP). the results showed that, Regarding the simple DEAHT curve, the COP slowly diminishes at low absorber-evaporator temperatures and rapidly at absorber temperatures more than 144.5 °C. Also, Utilizing the compressor in the basic design of the DEAHT unit results in improving the absorber temperature.

Economic and Environmental Assessment of a Novel Integrated Three-Column Extractive Distillation Process for Recycling Organics from Wastewater

For diluted wastewater with azeotropes discharged from chemical plants, it is important to design a sustainable extractive distillation process to achieve efficient separation. By separating the dilute wastewater containing isopropanol and acetonitrile, it is proved that the four-column extractive distillation processes with a preconcentration column and a novel three-column process containing an integrated column with preconcentration and solvent recovery function can achieve energy conservation and cost reduction. At the same time, heat integration and heat pump-assisted technologies were further used to intensify the proposed processes. The proposed processes are evaluated in terms of economy, energy consumption, and CO2 emissions. The results display that the double heat pump-assisted extractive distillation process can obtain 75.10% energy saving and the heat integration of the extractive distillation process with a preheater can save 69.45% cost, compared with the conventional extractive distillation process.

Possible evidence for geomagnetic intensity anomaly around 5500 BP from archaeomagnetic analyses of San Jacinto pottery, Caribbean Colombia

San Jacinto archaeological site in Northern Colombia hosts America's oldest pottery, radiometrically dated between 5940 ± 60 BP and 5190 ± 40 BP. Eleven ceramic fragments were subjected to detailed archaeomagnetic and archaeointensity investigation. Alternating field and thermal demagnetization, as well as magnetic mineralogy experiments, were carried out before double heating paleointensity determination to select the most suitable samples. Magnetic susceptibility vs. temperature curves revealed that magnetite and hematite grains are the main carriers of the thermoremanent magnetization. However, the contribution of hematite in total remanence seems to be negligible. Thirty-six samples corresponding to six pottery fragments were selected for Thellier-type paleointensity determinations. Mean intensity values range from 50.7 ± 4.7 to 65.3 ± 11.9 μT while virtual Axial Dipole Moments vary from 12.6 ± 1.2 to 16.2 ± 2.9 × 1022 Am2, indicating high geomagnetic field strength compared to values predicted by global geomagnetic models. This represents the first evidence of relatively high archaeointesities before 1000 BC. Similar or even higher geomagnetic strengths are observed in the Levant around 1100–800 BC and SW Pacific Region at 1450 AD. The actual cause of such anomalously high intensity, often attributed to the processes in the vicinity of the Core-Mantle Boundary, is still not fully understood.