Journal articles on the topic 'Experimental methods in fluid flow, heat and mass transfer'
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1
Krapivin, I. I., A. V. Belyaev, and A. V. Dedov. "Experimental Investigation of Boiling Heat Transfer in Freons Subjected to Forced Flow." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 4 (103) (August 2022): 59–79. http://dx.doi.org/10.18698/1812-3368-2022-4-59-79.
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At the moment there exist no methods for computing the boiling heat transfer coefficient in a fluid flow that could take into account the diversity of flow modes for a wide range of flow parameters. The majority of experimental and analytical studies were performed at low reduced pressures. Noticeably fewer investigations were carried out at high reduced pressures. At present, there are numerous empirical heat transfer computation methods developed for various freons at moderate reduced pressures and mass velocities. There also exist dedicated formulas for computing heat transfer in mini- and microchannels, obtained at low reduced pressures. Power and refrigeration systems could be fitted with mini-channel heat exchangers with custom working fluids subjected to high or moderate pressures. It is necessary to verify whether the existing methods for computing heat transfer are valid at higher reduced pressures, up to pr ≈ 0.6, in a channel with a hydraulic diameter of d ≈ 1 mm. The paper presents an overview of existing methods for calculating the heat transfer coefficient in two-phase flows; we then generalise these and compare their results to our own experimental data. We obtained said experimental data at the reduced pressures of pr = p/pcr = 0.43 and 0.56 in the mass velocity range of G = 200--1500 kg/(m2 · s). The paper describes our test bench and the experimental procedure
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Piasecka, Magdalena, Beata Maciejewska, and Paweł Łabędzki. "Development of FEM Calculation Methods to Analyse Subcooled Boiling Heat Transfer in Minichannels Based on Experimental Results." Applied Sciences 12, no. 24 (December 17, 2022): 12982. http://dx.doi.org/10.3390/app122412982.
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Even though two-phase heat transfer of refrigerants in minichannel heat sinks has been studied extensively, there is still a demand for improvements in overall thermal performance of miniature heat transfer exchangers. Experimental investigation and sophisticated heat transfer calculations with respect to heat transfer devices are still needed. In this work, a time-dependent experimental study of subcooled boiling was carried out for FC-72 flow in a heat sink, comprising of five asymmetrically heated minichannels. The heater surface temperature was continuously monitored by an infrared camera. The boiling heat transfer characteristics were investigated and the effect of the mass flow rate on the heat transfer coefficient was studied. In order to solve the heat transfer problem related to time-dependent flow boiling, two numerical methods, based on the FEM were applied, and based on the Trefftz functions (FEMT) and using the ADINA program. The results achieved with these two calculation methods were explored with an emphasis on the impact of the mass flow rate (range from 5 to 55 kg/h) on the resulting heat transfer coefficient. It was found that, with increasing mass flow, the heat transfer coefficient increased. Good agreement was found between the heat transfer coefficients, determined according to two numerical methods and the simple 1D calculation method.
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Kareemullah, Mohammed, K. M. Chethan, Mohammed K. Fouzan, B. V. Darshan, Abdul Razak Kaladgi, Maruthi B. H. Prashanth, Rayid Muneer, and K. M. Yashawantha. "Heat Transfer Analysis of Shell and Tube Heat Exchanger Cooled Using Nanofluids." Recent Patents on Mechanical Engineering 12, no. 4 (December 26, 2019): 350–56. http://dx.doi.org/10.2174/2212797612666190924183251.
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Background:: In Shell and Tube Heat Exchanger (STHX), heat is exchanged between hot water (coming from industrial outlet by forced convection) to the cold water. Instead of water, if Nano fluids are used into these tubes, then there is a possibility of improved heat transfer because of high thermal conductivity of the nanofluids. Objective:: From many literature and patents, it was clear that the study of STHX using metal oxide nanoparticles is very scarce. Therefore, the objective of the present investigation is to check the thermal performance of STHX operated with zinc oxide nanofluid and compare with water as the base fluid. Methods:: Heat transfer analysis of a shell and tube heat exchanger was carried out experimentally using Zinc oxide as a nanofluid. Mass flow rate on tube side was varied while on the shell side it was kept constant. Various heat transfer parameters like heat transfer coefficient, heat transfer rate effectiveness and LMTD (Log Mean Temperature Difference) were studied. The experimental readings were recorded after the steady-state is reached under forced flow conditions. Results:: It was found that the effectiveness improves with increase in mass flow rate of nanofluids as compared to base fluid. Conclusion:: From the obtained results, it was concluded that heat transfer enhancement and effectiveness improvement does occur with nano fluids but at the cost of pumping power.
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Akhtar, Shehnaz, Haider Ali, and Cheol Woo Park. "Thermo-Fluidic Characteristics of Two-Phase Ice Slurry Flows Based on Comparative Numerical Methods." Processes 7, no. 12 (December 2, 2019): 898. http://dx.doi.org/10.3390/pr7120898.
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Ice slurry is a potential secondary refrigerant for commercial refrigeration systems because of its remarkable thermal properties. It is necessary to optimize the heat transfer process of ice slurry to reduce the energy consumption of the refrigeration system. Thus, this study investigates the heat transfer performance of single-phase (aqueous solution) and two-phase (ice slurry) refrigerants in a straight horizontal tube. The numerical simulations for ice slurry were performed with ice mass fraction ranging from 5% to 20%. The effects of flow velocity and ice concentration on the heat transfer coefficient were examined. The results showed that heat transfer coefficient of ice slurry is considerably higher than those of single-phase flow, particularly at high flow velocity and ice content, where increase in heat transfer with a factor of two was observed. The present results confirmed that ice slurry heat transfer ability is considerably affected by flow velocity and ice concentration in laminar range. Moreover, the second part of this paper reports on the credibility three distinct two-phase Eulerian–Eulerian models (volume of fluid (VOF), mixture, and Eulerian) for the experimental conditions reported in the literature. All two-phase models accurately predict the thermal field at low ice mass fraction but underestimate that at high ice mass fractions. Regardless of the thermal discrepancies, the Eulerian–Eulerian models provide quite reasonable estimation of pressure drop with reference to experimental data. The numerical predictions from the VOF model are more accordant with the experimental results and the maximum percentage error is limited to ~20% and ~13% for thermal and pressure drop predictions, respectively.
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Ravi, Rengarajan, and Karunakaran Rajasekaran. "Experimental study of solidification of paraffin wax in solar based triple concentric tube thermal energy storage system." Thermal Science 22, no. 2 (2018): 973–78. http://dx.doi.org/10.2298/tsci160311021r.
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This paper addresses an experimental investigation of a solar based thermal energy storage system to meet current energy demand especially for milk industry in Tamil Nadu, India. A solar based energy storage system has been designed to study the heat transfer characteristics of paraffin wax where it is filled in the middle tube, with cold heat transfer fluid flowing outer tube, inner tube, and both tubes at a time during solidification process in a horizontal triple concentric heat exchanger. In this study, main concentrations are temperature distributions in the energy storage materials such as paraffin wax during solidification process and total solidification time. Three heat recovery methods were used to solidify paraffin wax from the inside tube, outside tube, and both tubes methods to improve the heat transfer between heat transfer fluid and phase change materials. The experiment has been performed for different heat transfer fluid mass-flow rates and different inlet temperatures and predicted results shows that solidification time is reduced.
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Wan, Junchi. "The Heat Transfer Coefficient Predictions in Engineering Applications." Journal of Physics: Conference Series 2108, no. 1 (November 1, 2021): 012022. http://dx.doi.org/10.1088/1742-6596/2108/1/012022.
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Abstract Most engineering applications have boundary layers; the convective transport of mass, momentum and heat normally occurs through a thin boundary layer close to the wall. It is essential to predict the boundary layer heat transfer phenomenon on the surface of various engineering machines through calculations. The experimental, analogy and numerical methods are the three main methods used to obtain convective heat transfer coefficient. The Reynolds analogy provides a useful method to estimate the heat transfer rate with known surface friction. In the Reynolds analogy, the heat transfer coefficient is independent of the temperature ratio between the wall and the fluid. Other methods also ignore the effect of the temperature ratio. This paper summarizes the methods of predicting heat transfer coefficients in engineering applications. The effects of the temperature ratio between the wall and the fluid on the heat transfer coefficient predictions are studied by summarizing the researches. Through the summary, it can be found that the heat transfer coefficients do show a dependence on the temperature ratio. And these effects are more obvious in turbulent flow and pointing out that the inaccuracy in the determination of the heat transfer coefficient and proposing that the conjugate heat transfer analysis is the future direction of development.
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Mastrullo, Rita, and Alfonso William Mauro. "Peripheral Heat Transfer Coefficient during Flow Boiling: Comparison between 2-D and 1-D Data Reduction and Discussion about Their Applicability." Energies 12, no. 23 (November 25, 2019): 4483. http://dx.doi.org/10.3390/en12234483.
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This paper presents a critical analysis of possible data reduction procedures for the evaluation of local heat transfer coefficient during flow boiling experiments. The benchmark method using one-dimensional (1-D) heat transfer in a heated tube was compared to a new data reduction method in which both radial and circumferential contributions to the conductive heat transfer inside a metal tube are considered. Using published experimental flow boiling data, the circumferential profiles of the wall superheat, inner wall heat flux, and heat transfer coefficients were independently calculated with the two data reduction procedures. The differences between the two methods were then examined according to the different heat transfer behavior observed (symmetric or asymmetric), which in turn was related to the two-phase flow regimes occurring in a channel during evaporation. A statistical analysis using the mean absolute percentage error (MAPE) index was then performed for a database of 417 collected flow boiling data taken under different operating conditions in terms of working fluid, saturation temperature, mass velocity, vapor quality, and imposed heat flux. Results showed that the maximum deviations between the two methods could reach up to 130% in the case of asymmetric heat transfer. Finally, the possible uses of the two data reduction methods are discussed, pointing out that the two-dimensional (2-D) model is the most reliable method to be employed in the case of high-level modeling of two-phase flow or advanced design of heat exchangers and heat spreader systems.
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Madaliev, Murodil, Elmurad Yunusaliev, Akramjon Usmanov, Nodirakhon Usmonova, and Khusanboy Muxammadyoqubov. "Numerical study of flow around flat plate using higher-order accuracy scheme." E3S Web of Conferences 365 (2023): 01011. http://dx.doi.org/10.1051/e3sconf/202336501011.
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Analytical methods exist to solve the problems of hydromechanics and heat transfer, but it is not possible to obtain the solution to some inhomogeneous and nonlinear problems of hydromechanics and heat transfer by analytical methods. The solution to such problems is carried out using numerical methods. Currently, there are many textbooks and monographs on numerical methods for solving problems of hydromechanics, thermal conductivity, heat and mass transfer, and others. The article presents the results of a numerical study of the flow structure in the flow around a flat plate. The calculations are based on the numerical solution of a system of nonstationary equations using a two-fluid turbulence model. For the numerical solution of these problems, schemes of the second and fourth order of accuracy were applied. The control volume method was used for the difference approximation of the initial equations, and the relationship between velocities and pressure was found using the SIMPLE procedure. To confirm the correctness of the numerical results, comparisons were made with each other and experimental data.
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Zhang, Yudong, Aiguo Xu, Feng Chen, Chuandong Lin, and Zon-Han Wei. "Non-equilibrium characteristics of mass and heat transfers in the slip flow." AIP Advances 12, no. 3 (March 1, 2022): 035347. http://dx.doi.org/10.1063/5.0086400.
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Slip flow is a common phenomenon in micro-/nano-electromechanical systems. It is well known that the mass and heat transfers in slip flow show many unique behaviors, such as the velocity slip and temperature jump near the wall. However, the kinetic understanding of slip flow is still an open problem. This paper first clarifies that the Thermodynamic Non-Equilibrium (TNE) flows can be roughly classified into two categories: near-wall TNE flows and TNE flows away from the wall. The origins of TNE in the two cases are significantly different. For the former, the TNE mainly results from the fluid–wall interaction; for the latter, the TNE is primarily due to the considerable (local) thermodynamic relaxation time. Therefore, the kinetic modeling methods for the two kinds of TNE flows are significantly different. Based on the Discrete Boltzmann Modeling (DBM) method, the non-equilibrium characteristics of mass and heat transfers in slip flow are demonstrated and investigated. The method is solidly verified by comparing with analytic solutions and experimental data. In pressure-driven flow, the DBM results are consistent with experimental data for the Knudsen number up to 0.5. It is verified that, in the slip flow regime, the linear constitutive relations with standard viscous or heat conduction coefficients are no longer applicable near the wall. For the Knudsen layer problem, it is interesting to find that a heat flux (viscous stress) component in the velocity (temperature) Knudsen layer approximates a hyperbolic sinusoidal distribution. The findings enrich the insights into the non-equilibrium characteristics of mass and heat transfers at micro-/nano-scales.
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Gopalsamy, Vijayan, Karunakaran Rajasekaran, Logesh Kamaraj, Siva Sivasaravanan, and Metin Kok. "Influence of Dimensionless Parameter on De-Ionized Water-alumina Nanofluid Based Parabolic Trough Solar Collector." Recent Patents on Nanotechnology 13, no. 3 (January 28, 2020): 206–21. http://dx.doi.org/10.2174/1872210513666190410123503.
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Background: Aqueous-alumina nanofluid was prepared using magnetic stirrer and ultrasonication process. Then, the prepared nanofluid was subjected to flow through the unshielded receiver of the parabolic trough solar collector to investigate the performance of the nanofluid and the effects of the dimensionless parameter were determined. Methods: The experimental work has been divided into two sections. First, the nanofluid was prepared and tested for its morphology, dimensions, and sedimentation using X-Ray Diffraction and Raman shift method. Then, the nanofluids of various concentrations from 0 to 4.0% are used as heat transfer fluid in unshielded type collector. Finally, the effect of the dimensionless parameter on the performance was determined. Results: For the whole test period, depending upon the bulk mean temperature, the dimensionless parameters such as Re and Nu varied from 1098 to 4552 & 19.30 to 46.40 for air and 2150 to 7551 & 11.11 to 48.54 for nanofluid. The enhancement of thermal efficiency found for 0% and 4.0% nanoparticle concentrations was 32.84% for the mass flow rate of 0.02 kg/s and 13.26% for the mass flow rate of 0.06 kg/s. Conclusion: Re and Nu of air depend on air velocity and ambient temperature. Re increased with the mass flow rate and decreased with concentration. Heat loss occurred by convection mode of heat transfer. Heat transfer coefficient and global efficiency increased with increased mass flow rate and volume fraction. The thermal efficiency of both 0% and 4.0% concentrations became equal for increased mass flow rate. It has been proven that at high mass flow rates, the time available to absorb the heat energy from the receiver is insufficient.
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Qian, Xuejun, Seong W. Lee, and Yulai Yang. "Heat Transfer Coefficient Estimation and Performance Evaluation of Shell and Tube Heat Exchanger Using Flue Gas." Processes 9, no. 6 (May 26, 2021): 939. http://dx.doi.org/10.3390/pr9060939.
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In the past few decades, water and air were commonly used as working fluid to evaluate shell and tube heat exchanger (STHE) performance. This study was undertaken to estimate heat transfer coefficients and evaluate performance in the pilot-scale twisted tube-based STHE using the flue gas from biomass co-combustion as working fluid. Theoretical calculation along with experimental results were used to calculate the specific heat of flue gas. A simplified model was then developed from the integration of two heat transfer methods to predict the overall heat transfer coefficient without tedious calculation of individual heat transfer coefficients and fouling factors. Performance including water and trailer temperature, heat load, effectiveness, and overall heat transfer coefficient were jointly investigated under variable operating conditions. Results indicated that the specific heat of flue gas from co-combustion ranging between 1.044 and 1.338 kJ/kg·K while specific heat was increased by increasing flue gas temperature and decreasing excess air ratio. The developed mathematical model was validated to have relatively small errors to predict the overall heat transfer coefficient. A flue gas mass flow rate of 61.3–98.8 kg/h, a water flow rate of 13.7–14.1 L/min, and a parallel arrangement of two water-to-air heaters in an empty trailer were found to be optimal conditions for space heating purpose. In addition, a lower poultry litter feeding rate decreased heat loss of flue gas and increased heat gain of water, while a lower water flow rate also provided a lower maximum possible heat transfer rate with a higher actual heat transfer rate to quickly achieve heat equilibrium that ultimately improves the performance. This study demonstrates the possibility of collecting residual heat from the flue gas using the pilot-scale STHE system while outlining a systematic approach and process for evaluating its performance.
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Leão, H. L. S. L., D. B. Marchetto, and G. Ribatski. "COMPARATIVE ANALYSES OF THE THERMAL PERFORMANCE OF REFRIGERANTS R134A, R245fa, R407C AND R600a DURING FLOW BOILING IN A MICROCHANNELS HEAT SINK." Revista de Engenharia Térmica 17, no. 2 (December 28, 2018): 57. http://dx.doi.org/10.5380/reterm.v17i2.64132.
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A comparative study of the performance of of refrigerants R134a, R407C, R245fa and R600a during flow boiling was performed for a 123x494 µm2 heat sink composed of 50 parallel rectangular microchannels. Heat transfer experimental results for heat fluxes up to 310 kW/m2, mass velocities from 300 to 800 kg/(m2 s), liquid subcoolings of 5 and 10 °C and saturation temperature close to 30 ºC were obtained. Global heat transfer coefficients (footprint) up to 10 kW/(m2 °C) were found. The liquid superheating necessary for the onset of nucleate boiling (ONB) was also characterized, and the fluids R245fa and R407C presented the highest and lowest, respectively, superheating to trigger the boiling process. Moreover, for a fixed averaged vapor quality, the average effective heat transfer coefficient increases with increasing mass velocity and liquid subcooling. The refrigerants R600a and R407C presented the highest and the lowest heat transfer coefficients, respectively. Five heat transfer predictive methods from literature provided accurate predictions of the data for R134a, R245fa and R600a, capturing most of the data trends. No one method provided accurate predictions of the heat transfer coefficient data of R407C.
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Zhao, Shu Lei, Xiao Tian Ding, Zheng Yuan Wei, and Gui Fang Liu. "Performance Test and Flow Pattern Simulation of Small Diameter Thermosyphons." Advanced Materials Research 634-638 (January 2013): 3782–87. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.3782.
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Thermal transfer behavior of small diameter thermosyphons with different fill ratio, the inner and outer temperature response at start-up, and the calculated vapor-liquid two-phase vertical flow regimes were studied. The thermosyphons were fabricated by different diameter glass tubes. The present study suggests that the best thermal conductive performance is obtained with 26% fill ratio. Inner and outer thermal behaviors were experimentally studied with innovative methods of attaching thermocouples on thermosyphon walls from both inside and outside. Experimental results indicated a very good temperature uniformity of thermosyphons. Furthermore, a 2D, planar CFD modeling using explicit Multi-Fluid VOF model in the Eulerian multiphase model was carried out to model the interaction/interface between gas and liquid as well as fluid flow movement inside the tube. Real-time vapor bubble generation, combination and vapor slug maps were derived from the simulation. A good agreement was observed between CFD acquired data and experimental observations. It is evidenced that CFD is a powerful tool to model and examine the complex flow and heat transfer in a thermosyphon.
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Galicia, Edgar Santiago, Yusuke Otomo, Toshihiko Saiwai, Kenji Takita, Kenji Orito, and Koji Enoki. "Subcooled Flow Boiling Heat Flux Enhancement Using High Porosity Sintered Fiber." Applied Sciences 11, no. 13 (June 24, 2021): 5883. http://dx.doi.org/10.3390/app11135883.
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Passive methods to increase the heat flux on the subcooled flow boiling are extremely needed on modern cooling systems. Many methods, including treated surfaces and extended surfaces, have been investigated. Experimental research to enhance the subcooled flow boiling using high sintered fiber attached to the surface was conducted. One bare surface (0 mm) and four porous thickness (0.2, 0.5, 1.0, 2.0 mm) were compared under three different mass fluxes (200, 400, and 600 kg·m−2·s−1) and three different inlet subcooling temperature (70, 50, 30). Deionized water under atmospheric pressure was used as the working fluid. The results confirmed that the porous body can enhance the heat flux and reduce the wall superheat temperature. However, higher porous thickness presented a reduction in the heat flux in comparison with the bare surface. Bubble formation and pattern flow were recorded using a high-speed camera. The bubble size and formation are generally smaller at higher inlet subcooling temperatures. The enhancement in the heat flux and the reduction on the wall superheat is attributed to the increment on the nucleation sites, the increment on the heating surface area, water supply ability through the porous body, and the vapor trap ability.
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Franco, Alessandro, and Maurizio Vaccaro. "Sustainable Sizing of Geothermal Power Plants: Appropriate Potential Assessment Methods." Sustainability 12, no. 9 (May 8, 2020): 3844. http://dx.doi.org/10.3390/su12093844.
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The paper analyzes the problem of defining the potential of geothermal reservoirs and the definition of a sustainable size of a geothermal power plant in the preliminary design phase. While defining the size of a geothermal plant, the objective is to find a compromise between renewability, technical sustainability, and economic return-related issues. In the first part of the paper the simplified lumped parameter approach based on the First-Order methods and their further evolutions and limitations is proposed. Experimental data available for some geothermal reservoirs are used for critical analysis of the simplified approaches for estimating the renewability and sustainability of the production of geothermal plants. In the second part the authors analyze methods based on theoretical heat transfer analysis supported by experimental data acquired from the geothermal field (thermal properties of the rock, porosity of the reservoir, and natural heat flux) and finally consider the numerical simulation as a method to connect the two approaches discussed before. The sustainability of geothermal power production can be estimated taking into account the energy stored in the reservoir and the thermal and fluid dynamic analysis of the reservoir. From this perspective, the numerical simulation of the reservoir can be considered as an effective method for the estimation of a sustainable mass flow rate extraction. Some specific cases are analyzed and discussed.
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Kuehn, Thomas. "Computer Simulation of Airflow and Particle Transport in Cleanrooms." Journal of the IEST 31, no. 5 (September 1, 1988): 21–27. http://dx.doi.org/10.17764/jiet.1.31.5.464773718u8051x2.
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Numerical procedures are well developed for simulating simple fluid flows and associated heat and mass transfer processes. Steady isothermal airflow in either a vertical laminar flow cleanroom or a tunnel cleanroom can be predicted accurately by using currently available simulation codes. The effects of items such as shields, process equipment, robot components, and bench design on the cleanroom airflow can be investigated by performing simulation experiments on a computer rather than physical experiments on a mockup. Design and operating parameters can be readily varied in the simulation to demonstrate their influence on the cleanroom performance. A review of existing airflow and particle transport simulation methods is presented and some recent applications to cleanroom airflow prediction are described. Advantages of computer simulation over experimental measurements and limitations are discussed, and future directions of cleanroom modeling are presented.
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Pungaiah, Sudalai Suresh, and Chidambara Kuttalam Kailasanathan. "Thermal Analysis and Optimization of Nano Coated Radiator Tubes Using Computational Fluid Dynamics and Taguchi Method." Coatings 10, no. 9 (August 20, 2020): 804. http://dx.doi.org/10.3390/coatings10090804.
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Automotive heat removal levels are of high importance for maximizing fuel consumption. Current radiator designs are constrained by air-side impedance, and a large front field must meet the cooling requirements. The enormous demand for powerful engines in smaller hood areas has caused a lack of heat dissipation in the vehicle radiators. As a prediction, exceptional radiators are modest enough to understand coolness and demonstrate great sensitivity to cooling capacity. The working parameters of the nano-coated tubes are studied using Computational Fluid Dynamics (CFD) and Taguchi methods in this article. The CFD and Taguchi methods are used for the design of experiments to analyse the impact of nano-coated radiator parameters and the parameters having a significant impact on the efficiency of the radiator. The CFD and Taguchi methodology studies show that all of the above-mentioned parameters contribute equally to the rate of heat transfer, effectiveness, and overall heat transfer coefficient of the nanocoated radiator tubes. Experimental findings are examined to assess the adequacy of the proposed method. In this study, the coolant fluid was transmitted at three different mass flow rates, at three different coating thicknesses, and coated on the top surface of the radiator tubes. Thermal analysis is performed for three temperatures as heat input conditioning for CFD. The most important parameter for nanocoated radiator tubes is the orthogonal array, followed by the Signal-to-Noise Ratio (SNRA) and the variance analysis (ANOVA). A proper orthogonal array is then selected and tests are carried out. The findings of ANOVA showed 95% confidence and were confirmed in the most significant parameters. The optimal values of the parameters are obtained with the help of the graphs.
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Deponte, H., W. Augustin, and S. Scholl. "Development of a quantification method for fouling deposits using phosphorescence." Heat and Mass Transfer 57, no. 10 (March 26, 2021): 1661–70. http://dx.doi.org/10.1007/s00231-021-03053-6.
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AbstractParticulate fouling on structured surfaces is typically quantified using the integral thermal or mass-based fouling resistance. The observed geometries may be structures that can improve the heat transfer in heat exchangers (e.g., dimples), cavities in components, or more complex geometries. However, due to limited accessibility or the requirement for a locally resolved measurement, the existing quantification methods may not be applicable to structured surfaces. For this reason, a new method is needed for the quantification for fouling deposits. In this study, dimpled surfaces were evaluated by measuring the integral thermal and mass-based fouling resistance and comparing it with the local fouling resistance inside and around the dimple. This comparison was carried out online with the Phosphorescent Fouling Quantification method developed for this purpose, using phosphorescent particles to quantify the deposited mass. The mass-based fouling resistance can be calculated using computer-aided image analysis. The measurements for the evaluation were conducted on dimpled surfaces, which produced a characteristic fouling pattern. With the new method a reduced surface coverage from up to 33.3 % was observed, which led to lower fouling resistances downstream of the dimple compared to a plain surface. These results confirm earlier numerical and experimental findings, suggesting an advantage of dimpled surfaces over other surface structures with respect to thermo-hydraulic efficiency as well as reduced fouling. Thus, the Phosphorescent Fouling Quantification method provides the possibility of calculating values for local fouling resistances on structured surfaces, as well as the possibility of optimizing surface structures to minimize fouling propensity.
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Singh, Prashant. "Errors Incurred in Local Convective Heat Transfer Coefficients Obtained through Transient One-Dimensional Semi-Infinite Conduction Modeling: A Computational Heat Transfer Study." Energies 15, no. 19 (September 23, 2022): 7001. http://dx.doi.org/10.3390/en15197001.
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In typical turbulent flow problems, detailed heat transfer coefficient (h) maps obtained through short-duration experiments are based on inverse heat transfer methods that take the wall temperatures measured via liquid crystals or infrared thermography as input, and an error minimization routine is adopted to determine the best value of h that satisfies the wall temperature temporal evolution under a certain change in fluid temperature. A common practice involves modeling the solid as a one-dimensional semi-infinite medium by selecting the solid material that has low thermal conductivity and low thermal diffusivity. However, in certain flow scenarios, the neglection of the lateral heat diffusion may lead to significant errors in the deduced h values. It is imperative to understand the reasons behind large errors that may be incurred by using the 1D heat conduction assumption in order to accurately determine high-resolution h maps for better heat exchanger designs in a wide range of thermal management applications. This paper presents a computational heat transfer study on different jet impingement scenarios to demonstrate the errors incurred in the determination of h when calculated under the assumption of one-dimensional (1-d) heat conduction into a solid. To this end, three different cases are studied: (a) single jet, (b) array jet (theoretical distribution), (c) array jet (experimental distribution), along with three different mainstream temperature evolution profiles representing step change, moderately fast transient and slow transient nature of flow driving the heat transfer in the solid. A known distribution of heat transfer coefficient (“true h”) for each of the three cases is considered, and three-dimensional transient heat diffusion equations were solved to populate temperatures of each node in the solid at every time step. It is found that stagnation zones’ h1d calculations were lower than the “true h” while the low heat transfer zones exhibited significantly higher h1d compared to the “true h”. For the array jet (experimental distribution) case, it was observed that errors can be as high as 10% in certain low heat transfer zones. Different data reduction procedures, configurations, and conditions explored in this study indicate that a suitable balance can be achieved if shorter time durations in transient experiments are used as a reference for tracking in h1d calculations to keep the deviations from the “true h” low.
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Vontas, Konstantinos, Manolia Andredaki, Anastasios Georgoulas, Nicolas Miché, and Marco Marengo. "The Effect of Hydraulic Diameter on Flow Boiling within Single Rectangular Microchannels and Comparison of Heat Sink Configuration of a Single and Multiple Microchannels." Energies 14, no. 20 (October 14, 2021): 6641. http://dx.doi.org/10.3390/en14206641.
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Phase change heat transfer within microchannels is considered one of the most promising cooling methods for the efficient cooling of high-performance electronic devices. However, there are still fundamental parameters, such as the effect of channel hydraulic diameter Dh whose effects on fluid flow and heat transfer characteristics are not clearly defined yet. The objective of the present work is to numerically investigate the first transient flow boiling characteristics from the bubble inception up to the first stages of the flow boiling regime development, in rectangular microchannels of varying hydraulic diameters, utilising an enhanced custom VOF-based solver. The solver accounts for conjugate heat transfer effects, implemented in OpenFOAM and validated in the literature through experimental results and analytical solutions. The numerical study was conducted through two different sets of simulations. In the first set, flow boiling characteristics in four single microchannels of Dh = 50, 100, 150, and 200 μm with constant channel aspect ratio of 0.5 and length of 2.4 mm were examined. Due to the different Dh, the applied heat and mass flux values varied between 20 to 200 kW/m2 and 150 to 2400 kg/m2s, respectively. The results of the two-phase simulations were compared with the corresponding initial single-phase stage of the simulations, and an increase of up to 37.4% on the global Nu number Nuglob was revealed. In the second set of simulations, the effectiveness of having microchannel evaporators of single versus multiple parallel microchannels was investigated by performing and comparing simulations of a single rectangular microchannel with Dh of 200 μm and four-parallel rectangular microchannels, each having a hydraulic diameter Dh of 50 μm. By comparing the local time-averaged thermal resistance along the channels, it is found that the parallel microchannels configuration resulted in a 23.3% decrease in the average thermal resistance R¯l compared to the corresponding single-phase simulation stage, while the flow boiling process reduced the R¯l by only 5.4% for the single microchannel case. As for the developed flow regimes, churn and slug flow dominated, whereas liquid film evaporation and, for some cases, contact line evaporation were the main contributing flow boiling mechanisms.
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Vontas, Konstantinos, Manolia Andredaki, Anastasios Georgoulas, Nicolas Miché, and Marco Marengo. "The Effect of Hydraulic Diameter on Flow Boiling within Single Rectangular Microchannels and Comparison of Heat Sink Configuration of a Single and Multiple Microchannels." Energies 14, no. 20 (October 14, 2021): 6641. http://dx.doi.org/10.3390/en14206641.
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Phase change heat transfer within microchannels is considered one of the most promising cooling methods for the efficient cooling of high-performance electronic devices. However, there are still fundamental parameters, such as the effect of channel hydraulic diameter Dh whose effects on fluid flow and heat transfer characteristics are not clearly defined yet. The objective of the present work is to numerically investigate the first transient flow boiling characteristics from the bubble inception up to the first stages of the flow boiling regime development, in rectangular microchannels of varying hydraulic diameters, utilising an enhanced custom VOF-based solver. The solver accounts for conjugate heat transfer effects, implemented in OpenFOAM and validated in the literature through experimental results and analytical solutions. The numerical study was conducted through two different sets of simulations. In the first set, flow boiling characteristics in four single microchannels of Dh = 50, 100, 150, and 200 μm with constant channel aspect ratio of 0.5 and length of 2.4 mm were examined. Due to the different Dh, the applied heat and mass flux values varied between 20 to 200 kW/m2 and 150 to 2400 kg/m2s, respectively. The results of the two-phase simulations were compared with the corresponding initial single-phase stage of the simulations, and an increase of up to 37.4% on the global Nu number Nuglob was revealed. In the second set of simulations, the effectiveness of having microchannel evaporators of single versus multiple parallel microchannels was investigated by performing and comparing simulations of a single rectangular microchannel with Dh of 200 μm and four-parallel rectangular microchannels, each having a hydraulic diameter Dh of 50 μm. By comparing the local time-averaged thermal resistance along the channels, it is found that the parallel microchannels configuration resulted in a 23.3% decrease in the average thermal resistance R¯l compared to the corresponding single-phase simulation stage, while the flow boiling process reduced the R¯l by only 5.4% for the single microchannel case. As for the developed flow regimes, churn and slug flow dominated, whereas liquid film evaporation and, for some cases, contact line evaporation were the main contributing flow boiling mechanisms.
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Yin, Qin, and Hong-Hai Liu. "Drying Stress and Strain of Wood: A Review." Applied Sciences 11, no. 11 (May 29, 2021): 5023. http://dx.doi.org/10.3390/app11115023.
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Wood drying stress causes various drying defects, which result from the wood microstructure and the transfer of heat and mass during the drying. It is the fundamental way to solve the problem of defects to clarify the law and mechanism of wood stress and strain development during drying. In this paper, based on the defects of wood drying, the theory and experimental testing methods of drying stress and strain were summarized. Meanwhile, artificial neural networks (ANN) and their application in the wood drying field were also investigated. The traditional prong and slicing methods were used practically in the research and industry of wood drying, but the stress changes in-process cannot be trapped. The technologies of image analysis and near-infrared spectroscopy provide a new opportunity for the detection of drying stress and strain. Hence, future interest should be attached to the combination of the theory of heat and mass transfer and their coupling during drying with the theory of microscopic cell wall mechanics and macroscopic drying. A more complete image acquisition and analysis system should be developed to realize the real-time monitoring of drying strain and cracking, practically. A more feasible and reasonable prediction model of wood drying stress and strain should be established to achieve the accuracy of the prediction.
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Thonon, Maxime, Laurent Zalewski, Stéphane Gibout, Erwin Franquet, Gilles Fraisse, and Mickael Pailha. "Experimental Comparison of Three Characterization Methods for Two Phase Change Materials Suitable for Domestic Hot Water Storage." Applied Sciences 11, no. 21 (November 1, 2021): 10229. http://dx.doi.org/10.3390/app112110229.
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This study presents an experimental comparison of three characterization methods for phase change materials (PCM). Two methods were carried out with a calorimeter, the first with direct scanning (DSC) and the second with step scanning (STEP). The third method is a fluxmetric (FM) characterization performed using a fluxmeter bench. For the three methods, paraffin RT58 and polymer PEG6000, two PCM suitable for domestic hot water (DHW) storage, were characterized. For each PCM, no significant difference was observed on the latent heat and the total energy exchanged between the three characterization methods. However, DSC and STEP methods did not enable the accurate characterization of the supercooling process observed with the FM method for polymer PEG6000. For PEG6000, the shape of the enthalpy curve of melting also differed between the experiments on the calorimeter—DSC and STEP—methods, and the FM method. Concerning the PCM comparison, RT58 and PEG6000 appeared to have an equivalent energy density but, as the mass density of PEG6000 is greater, more energy is stored inside the same volume for PEG6000. However, as PEG6000 experienced supercooling, the discharging temperature was lower than for RT58 and the material is therefore less adapted to DHW storage operating with partial phase change cycles where the PCM temperature does not decrease below 52 °C.
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Luzi, Giovanni, and Christopher McHardy. "Modeling and Simulation of Photobioreactors with Computational Fluid Dynamics—A Comprehensive Review." Energies 15, no. 11 (May 27, 2022): 3966. http://dx.doi.org/10.3390/en15113966.
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Computational Fluid Dynamics (CFD) have been frequently applied to model the growth conditions in photobioreactors, which are affected in a complex way by multiple, interacting physical processes. We review common photobioreactor types and discuss the processes occurring therein as well as how these processes have been considered in previous CFD models. The analysis reveals that CFD models of photobioreactors do often not consider state-of-the-art modeling approaches. As a comprehensive photobioreactor model consists of several sub-models, we review the most relevant models for the simulation of fluid flows, light propagation, heat and mass transfer and growth kinetics as well as state-of-the-art models for turbulence and interphase forces, revealing their strength and deficiencies. In addition, we review the population balance equation, breakage and coalescence models and discretization methods since the predicted bubble size distribution critically depends on them. This comprehensive overview of the available models provides a unique toolbox for generating CFD models of photobioreactors. Directions future research should take are also discussed, mainly consisting of an extensive experimental validation of the single models for specific photobioreactor geometries, as well as more complete and sophisticated integrated models by virtue of the constant increase of the computational capacity.
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Du Toit, Charl Gabriël. "Area of the Intersection between a Sphere and a Cylindrical Plane." Mathematical and Computational Applications 27, no. 5 (September 16, 2022): 79. http://dx.doi.org/10.3390/mca27050079.
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A proper understanding of the porous structure of packed beds of spheres is imperative in the analysis and design of the processes involving fluid flow and heat and mass transfer. The radial variation in porosity is of specific interest. When the positions and sizes of the spheres are known, the radial variation in porosity can be determined using volume-based, area-based, or line-based approaches. Here, the focus is on the area-based methods which employ the intersections between the spheres and selected cylindrical planes to determine the radial variation in porosity, focusing specifically on the calculation of the area of the curved elliptic intersection between a sphere and a cylindrical plane. Using geometrical considerations, analytical integral expressions have been derived based on the axial direction, angular direction, or the radial direction as independent variables. The integral expressions cannot be integrated analytically and have been evaluated using approximations or numerical integration. However, only indirect validation of the calculation of the intersection area has been provided by comparing the radial porosity profiles obtained with experimental data. This study provides direct validation of the calculated area through refined numerical integration of the primary integral expressions and the evaluation of the area employing computer-aided design software.
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Gorobets, V., O. Obodovych, V. Trokhanyak, and A. Serdyuk. "Rotary-pulsation apparatus for preparation of liquid grain feed." Energy and automation, no. 5(51) (October 28, 2020): 15–31. http://dx.doi.org/10.31548/energiya2020.05.015.
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Existing feed devices use methods of grinding grain and other components of the feed mixture in hammer crushers, which requires significant costs of mechanical (electrical) energy. Therefore, it is necessary to develop devices with a high degree of impact on the treated environment, which increases productivity and reduces energy consumption in technological processes. Such devices include rotor-pulsation devices, the principle of operation of which is based on the method of discrete-pulse energy input. The basis of this method is a multifactorial effect on the treated liquid homogeneous or heterogeneous medium, which consists of pressure pulsations, changes in fluid flow rate, intense cavitation, developed turbulence, hard cumulative effects, as well as high shear forces. The purpose of the study is to conduct a comprehensive analysis of kinematic and dynamic characteristics and establish the features of discrete-pulse energy input in the dispersion of grain mixtures in a rotary pulsation apparatus and develop on this basis energy-saving technology and equipment for liquid grain feed. A numerical and experimental study of heat and mass transfer processes in rotary pulsation apparatus for the preparation of liquid grain feed has been carried out. The basic hydraulic and thermal characteristics of such devices are received and geometrical characteristics of such device are defined. Experimental samples of the device for rectangular round shape of openings in the rotor-stator system are developed and made. Experimental studies of such characteristics as particle size distribution of grain feed mixture, power consumption in feed production and temperature change of water-grain mixture during its processing have been carried out.
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Aliukov, Sergei, and Konstantin Osintsev. "Mathematical Modeling of Coal Dust Screening by Means of Sieve Analysis and Coal Dust Combustion Based on New Methods of Piece-Linear Function Approximation." Applied Sciences 11, no. 4 (February 10, 2021): 1609. http://dx.doi.org/10.3390/app11041609.
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This study focuses on the development of new methodological approaches to dust-preparation and burning of separated particles, including through the use of polyfractional ensembles. Coal dust screening by means of sieve analysis is described in standard methods. However, in order to further use the results obtained during mathematical modeling of particle motion in fuel-air mixture and exothermal reactions of oxidation while burning in a torch, it must be possible to differentiate and integrate continuous functions. The methodology is based on the continuity of particle motion in a mixture with air in the calculation of aerodynamic and heat-mass exchange processes in a torch. The paper employs new scientific approaches to transforming and normalizing a continuously differentiable function described by the Gauss curve. We propose to combine mathematical modeling of such functions with methods of approximation of piece-linear functions developed by Professor S. V. Aliukov. The implementation of such methods helps reduce calculation errors of particle size and deviations thereof from average equivalent diameter and to avoid the Gibbs effect while differentiating. The paper contains analytical calculations based on the proposed method and experimental data. Quantitative and qualitative results of comparing analytical and experimental data are also presented. We provide recommendations on the further use and extension of the range of the results obtained in a computer simulation of fuel production and burning processes in a torch.
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Guillard, Tony, Gilles Flamant, Jean-Franc¸ois Robert, Bruno Rivoire, Joseph Giral, and Daniel Laplaze. "Scale up of a Solar Reactor for Fullerene and Nanotube Synthesis." Journal of Solar Energy Engineering 124, no. 1 (March 1, 2001): 22–27. http://dx.doi.org/10.1115/1.1434263.
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Conventional methods for the synthesis of fullerenes and carbon nanotubes such as laser or electric arc ablation have failed when the process is scaled up. Our ultimate goal is to scale a solar process up from 2 to 250 kW; this paper shows that our method for achieving this scale-up is valid because we were able to predict process performance variables at the 50 kW level from preliminary experimental results from 2 kW experiments. The key parameters that characterize this process are the carbon soot mass flow rate and the desired product yield. The carbon soot production rate is a function of the target temperature and this can be predicted in a straightforward way from a heat transfer model of the larger system. The yield is a more complicated function of specific reactor variables such as patterns of fluid flow, residence times at various temperatures, and the reaction chemistry, but we have found that for fullerenes it depends primarily on the concentration of carbon vapor in the carrier gas, the target temperature and the temperature distribution in the cooling zone. Using these parameters, we scaled our process up to 50 kW and compared the predicted results to the measured performance. A graphite target 6 cm in diameter was vaporized in an argon atmosphere and a reduced pressure of 120–240 hPa with a solar flux density in the range 600-920W/cm2. Vaporization rates as high as 50 g/h were measured with a fullerene production rate equal to about 2 g/h, i.e., the expected results.
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Gordon, R., and Y. Levy. "Optimization of Wall Cooling in Gas Turbine Combustor Through Three-Dimensional Numerical Simulation." Journal of Engineering for Gas Turbines and Power 127, no. 4 (September 20, 2005): 704–23. http://dx.doi.org/10.1115/1.1808432.
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This paper is concerned with improving the prediction reliability of CFD modeling of gas turbine combustors. CFD modeling of gas turbine combustors has recently become an important tool in the combustor design process, which till now routinely used the old “cut and try” design practice. Improving the prediction capabilities and reliability of CFD methods will reduce the cycle time between idea and a working product. The paper presents a 3D numerical simulation of the BSE Ltd. YT-175 engine combustor, a small, annular, reversal flow type combustor. The entire flow field is modeled, from the compressor diffuser to turbine inlet. The model includes the fuel nozzle, the vaporizer solid walls, and liner solid walls with the dilution holes and cooling louvers. A periodic 36 deg sector of the combustor is modeled using a hybrid structured/unstructured multiblock grid. The time averaged Navier-Stokes (N-S) equations are solved, using the k-ε turbulence model and the combined time scale (COMTIME)/PPDF models for modeling the turbulent kinetic energy reaction rate. The vaporizer and liner walls’ temperature is predicted by the “conjugate heat transfer” methodology, based on simultaneous solution of the heat transfer equations for the vaporizer and liner walls, coupled with the N-S equations for the fluids. The calculated results for the mass flux passing through the vaporizer and various holes and slots of the liner walls, as well as the jet angle emerging from the liner dilution holes, are in very good agreement with experimental measurements. The predicted location of the liner wall hot spots agrees well with the position of deformations and cracks that occurred in the liner walls during test runs of the combustor. The CFD was used to modify the YT-175 combustion chamber to eliminate structural problems, caused by the liner walls overheating, that were observed during its development.
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Liang, Yuchen, Guang Feng, Xiaogang Li, Haoran Sun, Wei Xue, Kunpeng Zhang, and Fengping Li. "Simulation Analysis of Nanosecond Laser Processing of Titanium Alloy Based on Helical Trepanning." Applied Sciences 12, no. 18 (September 8, 2022): 9024. http://dx.doi.org/10.3390/app12189024.
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Titanium alloy is a type of high-strength material that is difficult to process. In particular, in the aerospace field, the processing accuracy of titanium alloy is high. Recently, laser processing has emerged as a new technology with high processing precision. However, the laser processing methods have obvious differences in processing accuracy and effect. Among them, the laser spiral scanning method plays an important role in welding and drilling, but owing to the complexity of the laser molten pool behavior, there have been limited studies on the material removal mechanism based on laser spiral scanning. To understand the variable process of titanium alloy melt pool in laser spiral scanning processing, a light heat conduction model with mass transfer source term was simulated. The effects of laser power, scanning speed, and scanning path on the morphology were studied. The simulation results show that the unit energy density was the main factor for material removal, and the distribution of the material temperature affected the size of the recast layer. The experimental and simulation results were compared, and good agreement between them was observed. This study can provide a research foundation for the further application of laser spiral scanning technology.
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Rajavel, Rangasamy, and Kaliannagounder Saravanan. "Heat transfer studies on spiral plate heat exchanger." Thermal Science 12, no. 3 (2008): 85–90. http://dx.doi.org/10.2298/tsci0803085r.
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In this paper, the heat transfer coefficients in a spiral plate heat exchanger are investigated. The test section consists of a plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot water (hot fluid) is varying from 0.5 to 0.8 kg/s and the mass flow rate of cold water (cold fluid) varies from 0.4 to 0.7 kg/s. Experiments have been conducted by varying the mass flow rate, temperature, and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the Nusselt number which can be used for practical applications is proposed.
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Speetjens, M. F. M., and A. A. Van Steenhoven. "Heat and Mass Transfer Made Visible." Defect and Diffusion Forum 312-315 (April 2011): 713–18. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.713.
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Heat and mass transfer in fluid flows traditionally is examined in terms of temperature and concentration fields and heat/mass-transfer coefficients at fluid-solid interfaces. However, heat/mass transfer may alternatively be considered as the transport of a passive scalar by the total advective-diffusive flux in a way analogous to the transport of fluid by the flow field. This Lagrangian approach facilitates heat/mass-transfer visualisation in a similar manner as flow visualisation and has great potential for transport problems in which insight into (interaction between) the scalar fluxes throughout the entire configuration is essential. This ansatz furthermore admits investigation of heat and mass transfer by well-established geometrical methods from laminar-mixing studies, which offers promising new research capabilities. The Lagrangian approach is introduced and demonstrated by way of representative examples.
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Nallusamy, S. "Characterization of Al2O3/Water Nanofluid through Shell and Tube Heat Exchangers over Parallel and Counter Flow." Journal of Nano Research 45 (January 2017): 155–63. http://dx.doi.org/10.4028/www.scientific.net/jnanor.45.155.
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Nanotechnology has become one of the fastest growing scientific and engineering disciplines. Nano fluids have been established to possess enhanced thermal and physical properties such as thermal conductivity, thermal diffusivity, viscosity and convective heat transfer coefficients. The aim of this research article is to analyze the overall heat transfer coefficient by doing an experimental investigation on the convective heat transfer and flow characteristics of a nano fluid. In this research, an attempt was made for the nano fluid consisting of water and 1% volume concentration of Al2O3/water Nano fluid flowing in a parallel flow, counter flow in shell and tube heat exchanger under laminar flow condition. The 50nm diameter Al2O3nanoparticles are used in this investigation and was found that the overall heat transfer coefficient and convective heat transfer coefficient of nano fluid to be slightly higher than that of the base liquid at same mass flow rate and inlet temperature. Three samples of dissimilar mass flow rates have been identified for conducting the experiments and their results are continuously monitored and reported. The experimental analysis results were concluded that the heat transfer and overall heat transfer coefficient enhancement is possible with increase in the mass flow rate of fluid and Al2O3/water nano fluid on a comparative basis.
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Purandare, Pramod, Mandar Lele, and Raj Gupta. "Experimental investigation on heat transfer and pressure drop of conical coil heat exchanger." Thermal Science 20, no. 6 (2016): 2087–99. http://dx.doi.org/10.2298/tsci140802137p.
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The heat transfer and pressure drop analysis of conical coil heat exchanger with various tube diameters, fluid flow rates, and cone angles is presented in this paper. Fifteen coils of cone angles 180? (horizontal spiral), 135?, 90?, 45?, and 0? (vertical helical) are fabricated and analysed with, same average coil diameter, and tube length, with three different tube diameters. The experimentation is carried out with hot and cold water of flow rate 10 to 100 L per hour (Reynolds range 500 to 5000), and 30 to 90 L per hour, respectively. The temperatures and pressure drop across the heat exchanger are recorded at different mass flow rates of cold and hot fluid. The various parameters: heat transfer coefficient, Nusselt number, effectiveness, and friction factor, are estimated using the temperature, mass flow rate, and pressure drop across the heat exchanger. The analysis indicates that, Nusselt number and friction factor are function of flow rate, tube diameter, cone angle, and curvature ratio. Increase in tube side flow rate increases Nusselt number, whereas it reduces with increase in shell side flow rate. Increase in cone angle and tube diameter, reduces Nusselt number. The effects of cone angle, tube diameter, and fluid flow rates on heat transfer and pressure drop characteristics are detailed in this paper. The empirical correlations are proposed to bring out the physics of the thermal aspects of the conical coil heat exchangers.
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Kumar Gaur, Rohit, Dr Shashi Kumar Jain, and Dr Sukul Lomash. "Experimental Investigation on Triple Concentric Tube Heat Exchanger with Helical Baffles." SMART MOVES JOURNAL IJOSCIENCE 6, no. 11 (November 25, 2020): 14–20. http://dx.doi.org/10.24113/ijoscience.v6i11.324.
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A heat exchanger is a device used to transfer thermal energy between two or more liquids, between a solid surface and a liquid, or between solid particles and a liquid at different temperatures and in thermal contact where shell and tube heat exchangers contain a large number of tubes packed in a jacket whose axes are parallel to those of the shell. Heat transfer occurs when one fluid flows into the pipes while the other flows out of the pipes through the jacket. In industry, three-tube heat exchanger tubes are used as condensers, evaporators, sub cooler, heat recovery heat exchangers, etc. The three concentric tube heat exchanger is a constructively modified version of the double concentric tube heat exchanger as an intermediate tube adds some advantages over the double tube heat exchangers in that it is larger tube surface area heat transfer per unit of length. In the present study, the triple tube heat exchanger is further modified by inserting helical baffle over the surface of one of the tubes and observed turbulence flow which may lead to high heat transfer rates between the fluids of heat exchanger. Further, the Reynolds number, Nusselt number, friction factor of the flow at different mass flow rates of the hot fluid while keeping a constant mass flow rate of cold and normal temperature fluids were calculated. It was found that as the mass flow rate of the fluid increases the Reynolds number increases, the turbulence in the flow will increase which will cause the intermixing of the fluid, higher the rate of intermixing, more will be the heat transfer of the system.
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Gopal, Arumugam, Prabhakaran Duraisamy, and Thirumarimurugan Marimuthu. "Experimental Investigation on Heat Transfer and Pressure Drop Characteristics of Food Additive in Dimple Plate Heat Exchanger." Revista de Chimie 73, no. 3 (July 29, 2022): 97–109. http://dx.doi.org/10.37358/rc.22.3.8539.
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The present study attempts to examine the heat transfer and pressure drop aspects of a 11-channel dimple plate heat exchanger with hot water as the hot fluid and sodium benzoate (food preservative) as the cold fluid. The outcome of the mass flow rate of hot and cold fluids on the convective heat transfer coefficient and overall heat transfer coefficient were investigated. Furthermore, the effect of Reynolds number on the pressure drop and the Nusselt number were observed. The experimental results demonstrated that when the mass flow rate of the cold fluid increases, so does the overall heat transfer coefficient and the convective heat transfer coefficient. Convective heat transfer coefficient, overall heat transfer coefficient, pressure drop and Nusselt number were increased when sodium benzoate concentration is varied (0.2, 0.4, 0.6% w/w). A correlation is obtained on the basis of experimental results to estimate the Nusselt number as a function of Reynolds and Prandtl number.
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Amburi, Prudhvi Krishna, G. Senthilkumar, and Ibsa Neme Mogose. "Heat Transfer Augmentation: Experimental Study with Nanobubbles Technology." Advances in Materials Science and Engineering 2022 (July 19, 2022): 1–3. http://dx.doi.org/10.1155/2022/5885280.
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The experimental research on heat transfer characteristics is an ever-ending scheme since the life of all thermoelectronic devices relies on the effective management of thermal energy. In some cases, the gradient of temperature for heat transfer is to be minimum to avoid energy loss, but also there are numerous applications where the requirement of heat transfer to be maximum and could be achieved with a higher temperature difference between the heat transfer medium. In our current research, distilled water-ethylene glycol heat transfer fluid (HTF) was tested with different inlet mass flow rates and temperature as the hot fluid. Atmospheric air was chosen as the cold fluid. The natural convection heat transfer rate between hot and cold fluid streams was analyzed with and without the generation of micronanobubbles in the hot fluid. It was observed that compared to the base heat transfer fluid, the nanobubbles heat transfer fluid resulted in a 10–12% increase in heat transfer rate at hot fluid inlet temperatures of 28°C, 30°C, 32°C, 34°C, and 36°C. The method of generation of nanobubbles in HTF and their behavior are also highlighted.
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Piasecka, Magdalena, and Krzysztof Dutkowski. "Novel Numerical Methods in Heat and Mass Transfer." Energies 15, no. 7 (April 4, 2022): 2635. http://dx.doi.org/10.3390/en15072635.
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The Special Issue entitled “Novel Numerical Methods in Heat and Mass Transfer” focuses on such issues as CFD modeling of fluid flow, heat transfer characteristics, mass transfer, phase-change and heat exchangers. The Guest Editors of this Special Issue, under the support and auspices of the publishing house, and through its editors, invited the authors to publish their latest achievements in the area of numerical methods used in the area of heat and mass transfer. A short overview of the successful invited submission articles devoted to the above-mentioned subject is presented with the hope that these valuable works will be of interest to a wide range of readers, as the topic is important and worth further scientific attention.
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Rangasamy, Rajavel. "Experimental and numerical studies of a spiral plate heat exchanger." Thermal Science 18, no. 4 (2014): 1355–60. http://dx.doi.org/10.2298/tsci130317131r.
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An experimental and numerical study of heat transfer and flow characteristics of spiral plate heat exchanger was carried out. The effects of geometrical aspects of the spiral plate heat exchanger and fluid properties on the heat transfer characteristics were also studied. Three spiral plate heat exchangers with different plate spacing (4mm, 5mm and 6 mm) were designed, fabricated and tested. Physical models have been experimented for different process fluids and flow conditions. Water is taken as test fluid. The effect of mass flow rate and Reynolds number on heat transfer coefficient has been studied. Correlation has been developed to predict Nusselt numbers. Numerical models have been simulated using CFD software package FLUENT 6.3.26. The numerical Nusselt number have been calculated and compared with that of experimental Nusselt number.
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He, Bing Qiang, and Chun Ling Liao. "Study of Impact of Gas Cooler Cooling Circuit on Heat Transfer Performance." Applied Mechanics and Materials 236-237 (November 2012): 224–29. http://dx.doi.org/10.4028/www.scientific.net/amm.236-237.224.
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Experimental study on the structure and characteristics of cooling circuit of full-aluminum parallel flow gas cooler. The experimental tests on the built cell-type and ternary GCMCPF are conducted. In the heat transfer processes of the cooler with different circuit structures, the impact of CO2 refrigerant side flow resistance and the mass flow on the heat transfer performance of gas cooler is measured. The results show that the ternary type GCMCPF structure can enhance the heat transfer for CO2 fluid at the weak heat transfer area in the cell-type GCMCPF. Within a certain range of mass flow, the former heat transfer is 1.5 times the later one, and the structural sizes of GCMCPF can be reduced in the same requirements for heat transfer.
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Kotian, Shreyas, Nachiket Methekar, Nishant Jain, and Pritish Naik. "Heat Transfer and Fluid Flow in a Double Pipe Heat Exchanger, Part I: Experimental Investigation." Asian Review of Mechanical Engineering 9, no. 2 (November 5, 2020): 7–15. http://dx.doi.org/10.51983/arme-2020.9.2.2482.
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Double pipe heat exchangers have assumed importance over the years owing to their simple construction, ease of maintenance and cleaning, and extensive use in applications involving sensible heating or cooling of process fluids. In this present study, a detailed comparison is made between the theoretical results and experimental data of the performance parameters of the heat exchanger. Experiments were performed for 60 ≤ Re ≤ 240 for two different inlet temperatures of the hot fluid, 50°C, and 70°C keeping the inlet temperature of the cold fluid constant at 31°C. Graphs were plotted between various performance parameters such as overall heat transfer coefficient, effectiveness, NTU, outlet temperatures of the hot and cold streams against mass flow rates of the fluid. Lastly, a comparison was done between the theoretical data and experimental results and they showed good accordance with a mean deviation of 10-12%.
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Wilk, Joanna, Sebastian Grosicki, and Robert Smusz. "Mass/Heat Transfer Analogy Method in the Research on Convective Fluid Flow through a System of Long Square Mini-Channels." Materials 15, no. 13 (June 30, 2022): 4617. http://dx.doi.org/10.3390/ma15134617.
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The paper presents the results of experimental investigations of mass transfer processes with the use of the limiting current technique. This experimental work analyzed the not fully developed entrance laminar region. The tested case refers to the convective fluid flow through a system of nine long, square mini-channels that are 2 mm wide and 100 mm long. The method used in the measurements allows one to determine mass transfer coefficients during the electrolyte flow by utilizing electrochemical processes. The received mass transfer coefficients were applied to the analogous heat transfer case. The Chilton–Colburn analogy between mass and heat transfer was applied. The obtained results, in the form of the dependence of Nusselt number within the function of Reynolds and Prandtl numbers, can be a useful formula in the design and analysis of heat transfer processes in mini heat exchangers.
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Dharmalingam, R., K. K. Sivagnanaprabhu, J. Yogaraja, S. Gunasekaran, and R. Mohan. "Experimental Investigation Of Heat Transfer Characteristics Of Nanofluid Using Parallel Flow, Counter Flow And Shell And Tube Heat Exchanger." Archive of Mechanical Engineering 62, no. 4 (December 1, 2015): 509–22. http://dx.doi.org/10.1515/meceng-2015-0028.
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Abstract Cooling is indispensable for maintaining the desired performance and reliability over a very huge variety of products like electronic devices, computer, automobiles, high power laser system etc. Apart from the heat load amplification and heat fluxes caused by many industrial products, cooling is one of the major technical challenges encountered by the industries like manufacturing sectors, transportation, microelectronics, etc. Normally water, ethylene glycol and oil are being used as the fluid to carry away the heat in these devices. The development of nanofluid generally shows a better heat transfer characteristics than the water. This research work summarizes the experimental study of the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and 1% Al2O3 (volume concentration) nanoparticle flowing in a parallel flow, counter flow and shell and tube heat exchanger under laminar flow conditions. The Al2O3 nanoparticles of about 50 nm diameter are used in this work. Three different mass flow rates have been selected and the experiments have been conducted and their results are reported. This result portrays that the overall heat transfer coefficient and dimensionless Nusselt number of nanofluid is slightly higher than that of the base liquid at same mass flow rate at same inlet temperature. From the experimental result it is clear that the overall heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate. It shows that whenever mass flow rate increases, the overall heat transfer coefficient along with Nusselt number eventually increases irrespective of flow direction. It was also found that during the increase in mass flow rate LMTD value ultimately decreases irrespective of flow direction. However, shell and tube heat exchanger provides better heat transfer characteristics than parallel and counter flow heat exchanger due to multi pass flow of nanofluid. The overall heat transfer coefficient, Nusselt number and logarithmic mean temperature difference of the water and Al2O3 /water nanofluid are also studied and the results are plotted graphically.
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Bediako, Ernest Gyan, Petra Dančová, and Tomáš Vít. "Flow Boiling Heat Transfer of R134a in a Horizontal Smooth Tube: Experimental Results, Flow Patterns, and Assessment of Correlations." Energies 15, no. 20 (October 12, 2022): 7503. http://dx.doi.org/10.3390/en15207503.
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This study presents an extensive evaluation of heat transfer characteristics, flow patterns, and pressure drop for saturation pressures ranging from 460–660 kPa in a horizontal smooth tube of 5 mm internal diameter using R134a as the working fluid. The effect of saturation pressures for mass fluxes of 150–300 kg/m2s and heat fluxes of 8.26–23.3 kW/m2 which are typical of refrigeration and air conditioning applications are also investigated. Flow patterns observed during the study are predicted with a well-known flow pattern map of Wojtan et al. The experimental results are compared with seven (7) correlations developed based on different theories to find which correlation best predicts the experimental data. The results show that, at low mass flux, increasing saturation pressure results in an increased heat transfer coefficient. This effect is more pronounced in the low vapor quality region and the dominant mechanism is nucleate boiling. At high mass flux, increasing saturation pressure leads to an insignificant increase in the heat transfer coefficient. At this high mass flux but low heat flux, the heat transfer coefficient increases with vapor quality, indicating convective boiling dominance. However, for high heat flux, the heat transfer coefficient is linear over vapor quality, indicating nucleate boiling dominance. Pressure drop is observed to decrease with increasing saturation pressure. Increasing saturation pressure increases the vapor quality at which the flow pattern transitions from intermittent flow to annular flow. The flow patterns predicted are a mixture of slug and stratified wavy and purely stratified wavy for low mass fluxes. For increased mass fluxes, the flow patterns predicted are slug, intermittent, annular, and dryout. Cooper’s model was the best predictor of the experimental data and the trend of heat transfer coefficient.
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Yudakov, A. A., and O. N. Tsybul'skaya. "Experimental Study of Heat and Mass Transfer in a Swirling Gas Flow." Heat Transfer Research 37, no. 8 (2006): 663–73. http://dx.doi.org/10.1615/heattransres.v37.i8.20.
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Yong, Junhyeok, Junggyun Ham, Ohkyung Kwon, and Honghyun Cho. "Experimental Investigation of the Heat Transfer Characteristics of Plate Heat Exchangers Using LiBr/Water as Working Fluid." Energies 14, no. 20 (October 17, 2021): 6761. http://dx.doi.org/10.3390/en14206761.
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In this study, the heat exchange characteristics of water–LiBr solutions used as working fluid in a plate heat exchanger (PHE) were experimentally investigated at various concentrations. To analyze the heat transfer characteristics under LiBr/water conditions, a brazing type plate heat exchanger was installed, and the LiBr concentration on the high-temperature side was controlled at 56%, 58%, 60% and 60%. The results showed that the average heat transfer rate under water/water conditions was higher than that under LiBr/water conditions and the average heat transfer rate decreased as the LiBr concentration on the hot side increased. In addition, under both water/water and LiBr/water conditions, the average heat transfer rate and overall heat transfer coefficient increased as the mass flow rate of the working fluid on the hot side increased. When LiBr was used, the Reynolds number (Re) of LiBr on the hot side was more than nine times lower than that of water at the same mass flow rate owing to the influence of the increased viscosity. Based on the data obtained from the water/water and LiBr/water experiments, a correlation for predicting the Nusselt number (Nu) on the hot side in a wide range was developed.
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Singh, Sanjeev, and Rajeev Kukreja. "An Experimental Investigation of Flow Patterns During Condensation of HFC Refrigerants in Horizontal Micro-Fin Tubes." International Journal of Air-Conditioning and Refrigeration 27, no. 01 (March 2019): 1950010. http://dx.doi.org/10.1142/s201013251950010x.
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Condensation heat transfer coefficients and flow regimes in two different horizontal micro-fin tubes are examined during the condensation of refrigerants R-134a and R-410A. The present investigation has focused on determination and prediction of condensation heat transfer coefficients and finding the interrelation between heat transfer coefficients and the prevailing flow regimes. During flow visualization, flow regimes have been captured using borosilicate glass tube at inlet and outlet of the test condenser using high speed digital camera. Stratified, stratified wavy, wavy annular, annular, slug and plug flows have been observed at different mass fluxes and vapor qualities of the refrigerants. The observed flow regimes are compared with the existing flow regime maps proposed by Breber et al. [Prediction of horizontal tube side condensation of pure components using flow regime criteria, J. Heat Transfer 102 (1980) 471–476], Tandon et al. [A new flow regime map for condensation inside horizontal tubes, J. Heat Transfer 104 (1982) 763–768.] and Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] flow regime map shows good agreement with experimental data.
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Guangbin, Yu, Gao Dejun, Chen Juhui, Dai Bing, Liu Di, Song Ye, and Chen Xi. "Experimental Research on Heat Transfer Characteristics of CuO Nanofluid in Adiabatic Condition." Journal of Nanomaterials 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/3693249.
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The laminar convective heat transfer behavior of CuO nanoparticle dispersions in glycol with the average particle sizes (about 70 nm) was investigated experimentally in a flow loop with constant heat flux. To enhance heat exchange under high temperature condition and get the more accurate data, we try to improve the traditional experimental apparatus which is used to test nanofluid heat transfer characteristics. In the experiment five different nanoparticle concentrations (0.25%, 0.50%, 0.80%, 1.20%, and 1.50%) were investigated in a flow loop with constant heat flux. The experimental results show that the heat transfer coefficient of nanofluid becomes higher than that of pure fluid at the same Reynolds number and increased with the increasing of the mass fraction of CuO nanoparticles. Results also indicate that at very low volume concentrations nanofluid has no major impact on heat transfer parameters and the pressure of nanofluids increased by the mass fraction increase.
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Khan, Abdullah, Imran Shah, Waheed Gul, Tariq Amin Khan, Yasir Ali, and Syed Athar Masood. "Numerical and Experimental Analysis of Shell and Tube Heat Exchanger with Round and Hexagonal Tubes." Energies 16, no. 2 (January 12, 2023): 880. http://dx.doi.org/10.3390/en16020880.
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Shell and tube heat exchangers are used to transfer thermal energy from one medium to another for regulating fluid temperatures in the processing and pasteurizing industries. Enhancement of a heat transfer rate is desired to maximize the energy efficiency of the shell and tube heat exchangers. In this research work, we performed computational fluid dynamics (CFD) simulations and experimental analysis on the shell and tube heat exchangers using round and hexagonal tubes for a range of flow velocities using both parallel flow and counter flow arrangements. In the present work, the rate of heat transfer, temperature drop, and heat transfer coefficient are computed using three turbulence models: the Spalart–Allmaras, the k-epsilon (RNG), and the k-omega shear stress transport (SST). We further utilized the logarithmic mean temperature difference (LMTD) method to compute the heat transfer and mass flow rates for both parallel and counter flow arrangements. Our results show that the rate of heat transfer is increased by introducing the hexagonal structure tubes, since it has better flow disruption as compared to the round tubes. We further validated our simulation results with experiments. For more accurate results, CFD is performed in counter and parallel flow and it is deduced that the rate of heat transfer directly depends upon the velocity of fluids and the number of turns of the tube.
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Azari, Ahmad, Abdorrasoul Bahraini, and Saeideh Marhamati. "A CFD technique to investigate the chocked flow and heat transfer characteristic in a micro-channel heat sink." International Journal of Computational Materials Science and Engineering 04, no. 02 (June 2015): 1550007. http://dx.doi.org/10.1142/s2047684115500074.
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In this research, a Computational Fluid Dynamics (CFD) technique was used to investigate the effect of choking on the flow and heat transfer characteristics of a typical micro-channel heat sink. Numerical simulations have been carried out using Spalart–Allmaras model. Comparison of the numerical results for the heat transfer rate, mass flow rate and Stanton number with the experimental data were conducted. Relatively good agreement was achieved with maximum relative error 16%, and 8% for heat transfer and mass flow rate, respectively. Also, average relative error 9.2% was obtained for the Stanton number in comparison with the experimental values. Although, the results show that the majority of heat was transferred in the entrance region of the channel, but the heat transfer in micro-channels can also be affected by choking at channel exit. Moreover, the results clearly show that, the location where the flow is choked (at the vicinity of the channel exit) is especially important in determining the heat transfer phenomena. It was found that Spalart–Allmaras model is capable to capture the main features of the choked flow. Also, the effects of choking on the main characteristics of the flow was presented and discussed.