Статті в журналах: "Heat transfer reduction"

1

Usui, Hiromoto, and Takashi Saeki. "Drag reduction and heat transfer reduction by cationic surfactants." JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 26, no. 1 (1993): 103–6. http://dx.doi.org/10.1252/jcej.26.103.

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2

FLEISCHMAN, G. J., C. BATOR, R. MERKER, and S. E. KELLER. "Hot Water Immersion To Eliminate Escherichia coli O157:H7 on the Surface of Whole Apples: Thermal Effects and Efficacy." Journal of Food Protection 64, no. 4 (April 1, 2001): 451–55. http://dx.doi.org/10.4315/0362-028x-64.4.451.

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The effect of hot water immersion on both the reduction of Escherichia coli O157:H7 on the apple surface and internal temperatures of the apple was assessed in this study. Microbial reductions were measured experimentally, whereas internal temperatures were calculated through a mathematical analysis of experimental heat transfer data obtained from the apples. A method was developed to provide a purely surface-based inoculation of E. coli O157:H7. Rinsing produced no reduction, and treatments at 80 and 95°C produced reductions of more than 5 logs in 15 s or less. The heat transfer analysis based on experimental data was used to calculate surface heat transfer coefficients and predict temperatures throughout the apple. The analysis indicated a low heat transfer rate. Although it reduces thermal degradation, a low heat transfer rate precludes thermal-based reduction of any internalized microorganisms.

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3

Aguilar, G., K. Gasljevic, and E. F. Matthys. "Coupling Between Heat and Momentum Transfer Mechanisms for Drag-Reducing Polymer and Surfactant Solutions." Journal of Heat Transfer 121, no. 4 (November 1, 1999): 796–802. http://dx.doi.org/10.1115/1.2826068.

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Drag-reducing solutions exhibit simultaneous friction and heat transfer reductions, yet it has been widely believed that there is no direct coupling between the two. In this work, we have conducted a study to re-examine this issue, using measurements of friction and heat transfer over a wide range of flow conditions from onset to asymptotic, various pipe diameters, and several polymer and surfactant solutions. Contrary to some earlier suggestions, our tests show that no decoupling of the momentum and heat transfer mechanisms was seen at the onset of drag reduction, nor upon departure from the asymptotes, but rather that the friction and heat transfer reductions change simultaneously in those regions. For asymptotic surfactant and polymer solutions, the ratio of heat transfer and drag reductions was seen to be constant over a large range of Reynolds numbers, if modified definitions of the reduction parameters are used. In the nonasymptotic region, however, the ratio of heat transfer to drag reductions is higher and is a function of the reduction level, but is approximately the same for polymer and surfactant solutions. This variation is consistent with the concept of a direct coupling through a nonunity constant Prt, as also suggested by our local measurements of temperature and velocity profiles. We also saw that our diameter scaling technique for friction applies equally well to heat transfer. These findings allow us to predict directly the heat transfer from friction measurements or vice versa for these drag-reducing fluids, and also suggest that a strong coupling exists between the heat and momentum transfer mechanisms.

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4

Şahin, Ahmet Z., Davut Kavranoğlu, and Maamar Bettayeb. "Model reduction in numerical heat transfer problems." Applied Mathematics and Computation 69, no. 2-3 (May 1995): 209–25. http://dx.doi.org/10.1016/0096-3003(94)00128-q.

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5

Jordan, L. A., and D. van Vuuren. "Heat-constrained modelling of calcium sulphate reduction." Journal of the Southern African Institute of Mining and Metallurgy 122, no. 10 (November 4, 2022): 1–10. http://dx.doi.org/10.17159/2411-9717/1530/2022.

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A two-dimensional finite difference model has been developed to describe the reduction of kilogram quantities of dehydrated phosphogypsum. The model's scope has been limited to focus on the heat transfer and reactions that occur within a mass of material contained in a vessel inside a furnace rather than also including the effects of heat transfer to the vessel. Changes in the heat transfer properties (k, p, and Cp) are incorporated as the composition of the mass changes as the chemical reactions progress. The model is validated against experimental data, with samples heated to iooo°C at 3°C min-1 while purging with nitrogen gas. A sensitivity analysis of model predictions to the pre-exponential factor of the reaction rate constant of the main chemical reaction and the thermal conductivity of the powder bed indicated that, at the envisaged process conditions, the behaviour of the system depends much more on the rate of heat transfer than on the rate of the chemical reaction. The model demonstrated a significant increase in accuracy when the thermal conductivity was modelled to increase linearly with temperature compared to assuming a constant value.

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6

Zhu, Zhangyu, Juan Li, Hao Peng, and Dongren Liu. "Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction." Micromachines 12, no. 6 (June 3, 2021): 656. http://dx.doi.org/10.3390/mi12060656.

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Heat exchangers are general equipment for energy exchange in the industrial field. Enhancing the heat transfer of a heat exchanger with low pump energy consumption is beneficial to the maximum utilization of energy. The optimization design for enhanced heat transfer structure is an effective method to improve the heat transfer coefficient. Present research shows that the biomimetic structures applied in different equipment could enhance heat transfer and reduce flow resistance significantly. Firstly, six biomimetic structures including the fractal-tree-like structure, conical column structure, hybrid wetting structure, scale structure, concave-convex structure and superhydrophobic micro-nano structure were summarized in this paper. The biomimetic structure characteristics and heat transfer enhancement and drag reduction mechanisms were analyzed. Secondly, four processing methods including photolithography, nanoimprinting, femtosecond laser processing and 3D printing were introduced as the reference of biomimetic structure machining. Finally, according to the systemic summary of the research review, the prospect of biomimetic heat transfer structure optimization was proposed.

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7

Trigui, N., and Y. G. Guezennec. "Heat transfer reduction in manipulated turbulent boundary layers." International Journal of Heat and Fluid Flow 11, no. 3 (September 1990): 214–19. http://dx.doi.org/10.1016/0142-727x(90)90039-e.

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8

Liu, Lei, Qiu Yue Guo, Xin Feng Guo, Hui Qing Fan, and Zhu Hai Zhong. "The Effect of Drag-Reducing Polymer on Heat Transfer in Gas-Liquid Two-Phase Flow." Advanced Materials Research 383-390 (November 2011): 856–61. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.856.

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An experimental loop was established with API X52 steel pipes to investigate the effect of drag-reducing polymer on heat transfer in gas-liquid two-phase flow. The inner diameter of the steel pipe is forty millimeter and the test loop has four different test sections such as horizontal, inclined upward, inclined downward and vertical upward sections. The experimental results were presented. The relationship between the drag reduction efficiency and heat transfer reduction was analyzed. When the drag reduction induced by drag-reducing polymer is about 60~70%, the heat transfer between the fluid and the pipe wall obviously decreases. The heat transfer reduction can reach up to 80~90%, which is greater than the drag reduction. A new method is proposed for characterizing the effect of drag reducing polymer on the heat transfer in two-phase flow with Stanton Number.

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9

Baldauf, S., M. Scheurlen, A. Schulz, and S. Wittig. "Heat Flux Reduction From Film Cooling and Correlation of Heat Transfer Coefficients From Thermographic Measurements at Enginelike Conditions." Journal of Turbomachinery 124, no. 4 (October 1, 2002): 699–709. http://dx.doi.org/10.1115/1.1505848.

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Heat transfer coefficients and the resulting heat flux reduction due to film cooling on a flat plate downstream a row of cylindrical holes are investigated. Highly resolved two-dimensional heat transfer coefficient distributions were measured by means of infrared thermography and carefully corrected for local internal testplate conduction and radiation effects. These locally acquired data are processed to lateral average heat transfer coefficients for a quantitative assessment. A wide range variation of the flow parameters blowing rate and density ratio as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The effects of these dominating parameters on the heat transfer augmentation from film cooling are discussed and interpreted with the help of highly resolved surface results of effectiveness and heat transfer coefficients presented earlier. A new method of evaluating the heat flux reduction from film cooling is presented. From a combination of the lateral average of both the adiabatic effectiveness and the heat transfer coefficient, the lateral average heat flux reduction is processed according to the new method. The discussion of the total effect of film cooling by means of the heat flux reduction reveals important characteristics and constraints of discrete hole ejection. The complete heat transfer data of all measurements are used as basis for a new correlation of lateral average heat transfer coefficients. This correlation combines the effects of all the dominating parameters. It yields a prediction of the heat transfer coefficient from the ejection position to far downstream, including effects of extreme blowing angles and hole spacing. The new correlation has a modular structure to allow for future inclusion of additional parameters. Together with the correlation of the adiabatic effectiveness it provides an immediate determination of the streamwise heat flux reduction distribution of cylindrical hole film-cooling configurations.

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10

von Wolfersdorf, J., R. Hoecker, and C. Hirsch. "A Data Reduction Procedure for Transient Heat Transfer Measurements in Long Internal Cooling Channels." Journal of Heat Transfer 120, no. 2 (May 1, 1998): 314–21. http://dx.doi.org/10.1115/1.2824248.

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The effect of streamwise fluid temperature variation on the local heat transfer coefficient measurements in transient heat transfer tests in long channels is addressed. Previous methods are shown to result in considerable errors. A simplified model is proposed to characterize the local fluid temperature, which drives the heat transfer. With it, analytical solutions for the local wall temperature history are derived, which involve two unknowns, the local heat transfer coefficient and a lumped upstream heat transfer parameter. Using these solutions in the data reduction, these two parameters are determined from surface temperature measurements. Numerical experiments that simulate the physical experiment show the applicability and robustness of the proposed method. The method is finally demonstrated experimentally by investigating heat transfer in a smooth, square duct.

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11

Saha, A. K., Sumanta Acharya, Ron Bunker, and Chander Prakash. "Blade Tip Leakage Flow and Heat Transfer with Pressure-Side Winglet." International Journal of Rotating Machinery 2006 (2006): 1–15. http://dx.doi.org/10.1155/ijrm/2006/17079.

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A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location, where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure-side winglet exhibits a significant reduction in the leakage flow strength. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. For the flat tip, the winglet reduces the heat transfer coefficient locally by as much as 30%, while the average heat transfer coefficient is reduced by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and a 5% reduction in the pressure loss coefficient is achieved with the winglet with virtually no reduction in the average heat transfer coefficient. On the other hand, the suction-side squealer with constant width winglet shows lower heat transfer (reduction of 5.5%) and pressure loss coefficient (reduction of 26%) than its baseline counterpart.

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12

Tanda, G. "Natural Convection Heat Transfer From a Staggered Vertical Plate Array." Journal of Heat Transfer 115, no. 4 (November 1, 1993): 938–45. http://dx.doi.org/10.1115/1.2911390.

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An experimental study was performed to evaluate the natural convection heat transfer characteristics of an array of four staggered vertical plates. The thermal input at each plate was the same or differed from plate to plate depending on various heating modes. The effects of the interplate spacing and the plate-to-ambient temperature difference were investigated. The experiments were performed in air. Convective interactions among the plates were identified by examining the per-plate heat transfer coefficients and the local heat transfer coefficients along the vertical sides of plates. Local heat transfer results were obtained by means of the schlieren quantitative technique. Comparison of local heat transfer coefficients along the plate assembly with those of a continuous vertical plate (having the same height) showed enhancements up to a factor of two. Comparison of average heat transfer results with those for a parallel plate channel having the same exchanger size showed only little reductions in heat transfer rate, despite a 28 percent reduction in heat transfer area, with enhancements, in terms of specific heat flux, up to 30 percent.

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13

Klemeš, Jiří Jaromír, and Petar Sabev Varbanov. "Heat transfer improvement, energy saving, management and pollution reduction." Energy 162 (November 2018): 267–71. http://dx.doi.org/10.1016/j.energy.2018.08.014.

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14

Lewandowski, Witold M., and Henryk Biezk. "Reduction of convective heat transfer losses from flat surfaces." Chemical Engineering and Processing: Process Intensification 31, no. 6 (December 1992): 331–35. http://dx.doi.org/10.1016/0255-2701(92)87023-a.

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15

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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16

HARUKI, Naoto, Akihiko HORIBE, and Motohiro TORIGOE. "1307 Effect of Heat Transfer Surface on Flow Drag and Heat Transfer Reduction Effect of Surfactant Solution." Proceedings of Conference of Chugoku-Shikoku Branch 2013.51 (2013): _1307–1_—_1307–2_. http://dx.doi.org/10.1299/jsmecs.2013.51._1307-1_.

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17

Subramaniam, V., T. Dbouk, and J. L. Harion. "Topology optimization of conjugate heat transfer systems: A competition between heat transfer enhancement and pressure drop reduction." International Journal of Heat and Fluid Flow 75 (February 2019): 165–84. http://dx.doi.org/10.1016/j.ijheatfluidflow.2019.01.002.

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18

Lee, Jaehwan, Dongmin Kim, Jeongmin Mun, and Seokho Kim. "Heat-Transfer Characteristics of a Cryogenic Loop Heat Pipe for Space Applications." Energies 13, no. 7 (April 2, 2020): 1616. http://dx.doi.org/10.3390/en13071616.

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Infrared detectors on satellites and spacecraft require cooling to increase their measurement sensitivity. To efficiently cool infrared detectors in a zero gravity environment and in limited spaces, a cryogenic loop heat pipe (CLHP) can be used to transfer heat over a certain distance by the capillary forces generated from porous wicks without a mechanical power source. The CLHP presented in this study transfers the heat load to a condenser 0.5 m away from an evaporator at temperatures below −150 °C. The CLHP with two evaporators includes a subloop for initial start-up, and uses a pressure reduction reservoir (PRR) for the supercritical start-up from room to cryogenic temperature. Nitrogen is used as the working fluid to verify the thermal behavior of the CLHP, and the heat-transfer capacity according to the nitrogen charging pressure of the PRR is investigated. To simulate a cryogenic environment, the CLHP is installed inside a space environment simulator, including a single-stage GM (Gifford McMahon) cryocooler to cool the condenser. The CLHP is horizontally installed to simulate zero gravity. The heat-transfer characteristics are experimentally evaluated through the loop circulation of the CLHP.

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19

Wei, Jinjia, Yasuo Kawaguchi, Bo Yu, and Ziping Feng. "Rheological Characteristics and Turbulent Friction Drag and Heat Transfer Reductions of a Very Dilute Cationic Surfactant Solution." Journal of Heat Transfer 128, no. 10 (February 24, 2006): 977–83. http://dx.doi.org/10.1115/1.2345422.

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Turbulent friction drag and heat transfer reductions and rheological characteristics of a very dilute cationic surfactant solution, cetyltrimethyl ammonium chloride (CTAC)/sodium salicylate (NaSal) aqueous solution, were experimentally investigated at various temperatures. It was found that there existed a critical temperature above which drag and heat transfer reductions disappeared and shear viscosities rapidly dropped to that of water. It was surmised that drag and heat transfer reductions had a certain relationship with rheological characteristics and a rheological characterization of CTAC∕NaSal surfactant solutions was performed to clarify this relationship. The effects of Reynolds number and fluid temperature and concentration on drag and heat transfer reductions were qualitatively explained by analyzing the measured shear viscosity data at different shear rates and solution temperatures and concentrations. The Giesekus model was found to fit the measured shear viscosities reasonably well for different temperatures and concentrations of the surfactant solution and the model parameter values obtained by fitting were correlated with temperature at certain solution concentrations. From the correlation results, the temperature effect on viscoelasticity of surfactant solutions was analyzed to relate the rheological characteristics with drag and heat transfer reduction phenomena.

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20

Putradianto, Ristiyan Ragil, and Allen Haryanto Lukmana. "Heat Loss and Cost Reduction of Insulation Materials on Geothermal Pipes." Journal of Petroleum and Geothermal Technology 4, no. 1 (May 17, 2023): 58. http://dx.doi.org/10.31315/jpgt.v4i1.9706.

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Power plant in X field has 6 production wells with steam dominated reservoir type. Fluid flowing in pipe from the well to the plant experienced heat loss that occured due to difference in the temperature of the flowing steam and the outside that caused heat transfer from inside the pipe to the outside. Minimizing heat transfer can be done by using an insulator is installed on the outside of the pipe, in this case, Foamglas W+F Insulation The method to assess the heat loss is by calculating material properties as well as fluid properties to deterimine heat transfer rate for one well as representation of all wells. From the calculation, it can be concurred that the use of Foamglas W+F Insulation material provides reduction in heat loss of 113,61 kWh for one well with significant reduction in costs of 1.035 billion IDR per well per year. By comparing the heat loss reduction value which is almost the same, the option to replace the materials to Foamglas W+F insulation material is cheaper than adding the existing insulation thickness.

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21

Seem, J. E., S. A. Klein, W. A. Beckman, and J. W. Mitchell. "Model Reduction of Transfer Functions Using a Dominant Root Method." Journal of Heat Transfer 112, no. 3 (August 1, 1990): 547–54. http://dx.doi.org/10.1115/1.2910421.

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Transfer function methods are more efficient for solving long-time transient heat transfer problems than Euler, Crank-Nicolson, or other classical techniques. Transfer functions relate the output of a linear, time-invariant system to a time series of current and past inputs, and past outputs. Inputs are modeled by a continuous, piecewise linear curve. The computational effort required to perform a simulation with transfer functions can be significantly decreased by using the Pade´ approximation and bilinear transformation to determine transfer functions with fewer coefficients. This paper presents a new model reduction method for reducing the number of coefficients in transfer functions that are used to solve heat transfer problems. There are two advantages of this method over the Pade´ approximation and bilinear transformation. First, if the original transfer function is stable, then the reduced transfer function will also be stable. Second, reduced multiple-input single-output transfer functions can be determined by this method.

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22

Wang, ZhenHuan, XinXue Zhao, and YoungChul Kwon. "Experimental Study on Heat Transfer Performance of White Smoke Reduction Heat Exchange System." IOP Conference Series: Earth and Environmental Science 446 (March 21, 2020): 022043. http://dx.doi.org/10.1088/1755-1315/446/2/022043.

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23

Turner, J. C. R. "On the reduction by heat transfer of mass transfer from an evaporating liquid." Chemical Engineering Science 44, no. 10 (1989): 2223–24. http://dx.doi.org/10.1016/0009-2509(89)85156-5.

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24

Schneider, Brandon, Ali Koşar, Chih-Jung Kuo, Chandan Mishra, Gregory S. Cole, Robert P. Scaringe, and Yoav Peles. "Cavitation Enhanced Heat Transfer in Microchannels." Journal of Heat Transfer 128, no. 12 (February 21, 2006): 1293–301. http://dx.doi.org/10.1115/1.2349505.

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Heat transfer has been investigated in the presence of hydrodynamic cavitation instigated by 20-μm wide inlet micro-orifices entrenched inside 227-μm hydraulic diameter microchannels. Average surface temperatures, heat transfer coefficients, and pressure drops have been obtained over effective heat fluxes ranging from 39 to 558W∕cm2 at mass flux of 1814kg∕m2s under noncavitating and three cavitating conditions. Significant heat transfer enhancement has been recorded during supercavitating flow conditions in comparison to noncavitating flows with minimal pressure drop penalty. Once supercavitating conditions were reached, no apparent heat transfer augmentation was detected with the reduction of the cavitation index. Visualization of the flow morphology and the heat transfer coefficient characteristics aided in the evaluation of the dominant heat transfer mechanism under various thermal-hydraulic conditions.

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25

Lavine, A. S., and C. Bai. "An Analysis of Heat Transfer in Josephson Junction Devices." Journal of Heat Transfer 113, no. 3 (August 1, 1991): 535–43. http://dx.doi.org/10.1115/1.2910596.

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Josephson junctions are electronic devices made from superconducting materials that cycle between resistive and nonresistive states. Heat generated in the resistive state causes a temperature rise, which may adversely affect electrical behavior, by reducing the critical Josephson current. In this work, temperature distributions and resulting reductions in critical current are calculated for Josephson junctions made from low and high-temperature superconductors. It is found that an unacceptable reduction in critical current may occur for junctions made from high-temperature materials. This problem can almost certainly be overcome, but perhaps at the expense of one advantage of Josephson junctions, namely compactness.

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26

Wu, C. H., J. H. Zeng, G. R. Wu, X. Xie, and M. Zhang. "A new method for determination of the theoretical reduction amount for wide-thick slab during the mechanical reduction process." Journal of Mining and Metallurgy, Section B: Metallurgy 57, no. 1 (2021): 125–36. http://dx.doi.org/10.2298/jmmb200622010w.

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Mechanical soft reduction (MSR) is an effective method for elimination of the centerline segregation and porosity of the continuous casting steel slab, and the reduction amount is a key parameter that determines whether the MSR could be applied successfully. In the present work, a 2D heat transfer model was developed for predicting the non-uniform solidification of the wide-thick slab. The measured shell thickness by nail shooting experiment and the measured slab surface temperature by infrared camera were applied to validate the 2D heat transfer model. A new calculation method of theoretical reduction amount that could consider the influence of non-uniform solidification of the wide-thick slab was then derived. Based on the predicted temperature field by the 2D heat transfer model and the newly-proposed calculation method, the required theoretical reduction amount and reduction gradient/rate for the wide-thick slab were calculated and discussed. The difference between the newly-proposed method and the previous method, the influence of the casting speed and slab thickness on the required theoretical reduction amount and reduction gradient/rate were also investigated.

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27

Liu, Chenghong, Xueyong Ding, Hegong Liu, Xinlin Yan, Chao Dong, and Jia Wang. "Numerical Analysis on Characteristics of Reduction Process within a Pre-Reduction Rotary Kiln." Metals 11, no. 8 (July 25, 2021): 1180. http://dx.doi.org/10.3390/met11081180.

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The reduction process inside the ore pre-reduction rotary kiln involves a series of physicochemical reactions, and in-depth understanding of the reduction behavior is helpful to improve the product quality and productivity. This paper reports a three-dimensional steady state mathematical model based on computational fluid dynamics, which considers heat transfer, mass transfer and chemical reactions inside the rotary kiln. A user-defined functions (UDFs) program in C language is developed to define physical parameters and chemical reactions, and calculate the heat and mass transfer between freeboard and bed regions. The model is validated by measurement data and is then used to investigate the detailed information inside the rotary kiln. The results show that there is a temperature gradient in the bed, which is maximal near the kiln tail and decreases gradually as the reduction process progresses. The result also confirms that the reduction of FeO to Fe is the limiting step of the whole reduction process because this reaction requires a higher reduction potential. Furthermore, the influence of C/O mole ratio and fill degree are analyzed by comparing the average bed temperature, reduction potential and metallization ratio.

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28

Zhang, Yu, Zhentao Zhang, Junling Yang, Yunkai Yue, and Huafu Zhang. "A Review of Recent Advances in Superhydrophobic Surfaces and Their Applications in Drag Reduction and Heat Transfer." Nanomaterials 12, no. 1 (December 23, 2021): 44. http://dx.doi.org/10.3390/nano12010044.

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Inspired by the superhydrophobic properties of some plants and animals with special structures, such as self-cleaning, water repellent, and drag reduction, the research on the basic theory and practical applications of superhydrophobic surfaces is increasing. In this paper, the characteristics of superhydrophobic surfaces and the preparation methods of superhydrophobic surfaces are briefly reviewed. The mechanisms of drag reduction on superhydrophobic surfaces and the effects of parameters such as flow rate, fluid viscosity, wettability, and surface morphology on drag reduction are discussed, as well as the applications of superhydrophobic surfaces in boiling heat transfer and condensation heat transfer. Finally, the limitations of adapting superhydrophobic surfaces to industrial applications are discussed. The possibility of applying superhydrophobic surfaces to highly viscous fluids for heat transfer to reduce flow resistance and improve heat transfer efficiency is introduced as a topic for further research in the future.

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29

Sheikhzadeh, Ghanbar Ali, S. H. Musavi, and N. Sadoughi. "Effect of a Shield on Mixed Convection in a Rectangular Enclosure with Moving Cold Sidewalls and a Heat Source on the Bottom Wall." Defect and Diffusion Forum 297-301 (April 2010): 584–89. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.584.

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In this work, the mixed convention of air inside a rectangular cavity with moving cold sidewalls is studied numerically. A constant flux heat source is attached to the bottom wall of the cavity. A thin thermal shield is located at a specific distance above the heat source. The governing equations are solved using appropriate numerical methods. A parametric study has been conducted and the effects of heat source length, its location and the shield distance from the source on the heat transfer have been investigated. The results show that the heat dissipation increases as the heat source and the shield are moved up to a certain distance towards either sidewall. However, moving them beyond this limiting distance results in the reduction of heat dissipation. It is shown that the presence of shield results in the reduction of the heat transfer coefficient. However, for the normalized distance of the shield from the heat source greater than , the shield’s effect on the reduction of the heat transfer coefficient is less than.

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30

왕쩐후안 and 권영철. "Experimental Study on Heat Transfer Performance of White Heat Reduction Heat Exchange System under Winter Conditions." Journal of the Korean Society of Mechanical Technology 20, no. 3 (June 2018): 321–26. http://dx.doi.org/10.17958/ksmt.20.3.201806.321.

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31

Ding, Lei, Li Xu, Ling Ling Liu, Jin Li Qiao, and Yu Yu Liu. "Effect of Heat-Treatment on the Activity of Nickel Phthalocyanine Catalysts for Oxygen Reduction Reaction in Acid and Alkaline Electrolytes." Advanced Materials Research 535-537 (June 2012): 2104–7. http://dx.doi.org/10.4028/www.scientific.net/amr.535-537.2104.

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Effect of heat-treatment on the activity of nickel phthalocyanine (NiPc) catalysts for oxygen reduction reaction (ORR) was studied in both acid and alkaline electrolytes. The catalytic activity was found to depend strongly on the electrolyte and heat treatment temperature. High ORR activity was demonstrated on 40%NiPc/C electrode in 0.1M KOH solution, and the heat-treatment of 800oC is optimal for the catalyst synthesized. Further using rotating disk electrode (RDE) measurements and Koutechy-Levich analysis, the overall electron transfer number in the catalyzed ORR on 40%NiPc/C was found to be 2.8, suggesting the catalyzed ORR proceeds via both the 2e- transfer reduction and the 4e- transfer reduction.

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TSUTSUI, Takayuki, Tamotsu IGARASHI, and Hajime NAKAMURA. "Drag Reduction and Heat Transfer Enhancement of a Square Prism." JSME International Journal Series B 44, no. 4 (2001): 575–83. http://dx.doi.org/10.1299/jsmeb.44.575.

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33

Wang, Yi, Bo Yu, Jacques L. Zakin, and Haifeng Shi. "Review on Drag Reduction and Its Heat Transfer by Additives." Advances in Mechanical Engineering 3 (January 2011): 478749. http://dx.doi.org/10.1155/2011/478749.

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34

Saeki, Takashi, Keiji Tokuhara, and Toshio Matsumura. "0513 Drag reduction and heat transfer of cationic surfactant solutions." Proceedings of the Fluids engineering conference 2009 (2009): 235–36. http://dx.doi.org/10.1299/jsmefed.2009.235.

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35

Bashtovoi, V. G., M. S. Krakov, and E. M. Taits. "HEAT TRANSFER ENHANCEMENT AND DRAG REDUCTION IN MAGNETOFLUID-COATED CHANNELS." Numerical Heat Transfer, Part A: Applications 20, no. 4 (December 1991): 395–408. http://dx.doi.org/10.1080/10407789108944829.

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36

Pinnau, René, and Alexander Schulze. "Model reduction techniques for frequency averaging in radiative heat transfer." Journal of Computational Physics 226, no. 1 (September 2007): 712–31. http://dx.doi.org/10.1016/j.jcp.2007.04.024.

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37

Yu, Jiu Yang, Li Jun Liu, Wei Lin, Qian Liu, Wen Hao Yang, Si Hao Nie, and Yi Wen Chen. "Numerical Simulation and Field Synergy Analysis of Flow and Heat Transfer in a Vibratory Tube." Advanced Materials Research 516-517 (May 2012): 949–53. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.949.

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The present paper focuses on the analysis of transient heat transfer and flow in a vibratory tube. The characteristics of flow and heat transfer are investigated by dynamic mesh of CFD (computational fluid dynamics) software FLUENT, the velocity and temperature distributions in a vibration cycle are analyzed by field synergy theory. The results indicate that the vibration parameters have great effect on heat transfer, and the tube vibration leads to heat transfer enhancement or reduction. Moreover, the optimum heat transfer performance inside tubes is obtained in a half-cycle when time phase is 90°.

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38

Su, Yu. "Finite Element Simulation of Enhanced Cooling Cutting of Stainless Steel." Applied Mechanics and Materials 312 (February 2013): 445–49. http://dx.doi.org/10.4028/www.scientific.net/amm.312.445.

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This paper develops a 2D finite element model for the enhanced cooling cutting of stainless steel. The enhanced cooling effect is modeled with a convective heat transfer coefficient assigned to a heat transfer window of cutting zone. Five convective heat transfer coefficients are defined to simulate different enhanced cooling effects. The simulation results suggest that increase of convective heat transfer coefficient results in a very small reduction of maximum tool-chip interface temperature, even when a very large convective heat transfer coefficient is used. In addition, no significant effect on cutting force and thrust force is observed with the increase of convective heat transfer coefficient.

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39

Lemanov, V. V., M. A. Pakhomov, V. I. Terekhov, and Z. Travnicek. "Non-stationary convective heat transfer in an air synthetic impinging jet. Experiment and numerical simulation." Journal of Physics: Conference Series 2119, no. 1 (December 1, 2021): 012024. http://dx.doi.org/10.1088/1742-6596/2119/1/012024.

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Abstract An unsteady local heat transfer in an air synthetic non-steady-state jet impingement onto a flat plate with a variation of the Reynolds number, nozzle-to-plate distance and pulses frequency is experimentally and numerically studied. Measurements of the averaged and pulsating heat transfer at the stagnation point are conducted using a heat flux sensor. The axisymmetric URANS method and the Reynolds stress model are used for numerical simulations. For local values of heat transfer, zones with the maximum instantaneous value of heat flux and heat transfer coefficient are identified. The heat transfer increases at relatively low nozzle-to-plate distances (H/d ≤ 4). The heat transfer decreases at high distance from the orifice and target surface. An increase in the Reynolds number causes reduction of heat transfer.

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40

INABA, Hideo, Naoto HARUKI, Akihiko HORIBE, Naoyuki FURUMOTO, Toru NAKATA, and Kenji SATO. "306 Heat Transfer Characteristics of Plate Type Heat Exchanger with Water Flow Reduction Surfactant." Proceedings of Conference of Chugoku-Shikoku Branch 2001.39 (2001): 91–92. http://dx.doi.org/10.1299/jsmecs.2001.39.91.

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41

Jiang and, Y., and J. M. Floryan. "Influence of Heat Transfer at the Interface on the Thermocapillary Convection in the Adjacent Phase." Journal of Heat Transfer 125, no. 1 (January 29, 2003): 190–94. http://dx.doi.org/10.1115/1.1535448.

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Thermocapillary convection in a cavity is considered. It is shown that when the cavity is heated through its sides, reduction of heat transfer across the interface leads to an increase of the interface deformation. When the same cavity is heated through the interface, similar reduction of heat transfer across the interface results in diminished convection and reduced interface deformation.

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42

Bezaatpour, Mojtaba, and Mohammad Goharkhah. "A novel heat sink design for simultaneous heat transfer enhancement and pressure drop reduction utilizing porous fins and magnetite ferrofluid." International Journal of Numerical Methods for Heat & Fluid Flow 29, no. 9 (September 2, 2019): 3128–47. http://dx.doi.org/10.1108/hff-12-2018-0810.

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Purpose With development of the modern electronic and mechanical devices, cooling requirement has become a serious challenge. Innovative heat transfer enhancement methods are generally accompanied by undesirable increase of pressure drop and consequently a pumping power penalty. The current study aims to present a novel and easy method to manufacture a mini heat sink using porous fins and magnetite nanofluid (Fe3O4/water) as the coolant for simultaneous heat transfer enhancement and pressure drop reduction. Design/methodology/approach A three-dimensional numerical study is carried out to evaluate the thermal and hydrodynamic performance of the mini heat sink at different volume fractions, porosities and Reynolds numbers, using finite volume method. The solver specifications for discretization of the domain involve the SIMPLE, second-order upwind and second order for pressure, momentum and energy, respectively. Findings Results show that porous fins have a favorable effect on both heat transfer and pressure drop compared to solid fins. Creation of a virtual velocity slip on the channel-fin interfaces similar to the micro scale conditions and the flow permeation into the porous fins are the main mechanisms of pressure drop reduction. On the other hand, the heat transfer enhancement is attributed to the increase of the solid-fluid contact area and the improvement of the flow mixing because of the flow permeation into the porous fins. An optimal porosity for maximum convective heat transfer enhancement is obtained as a function of Reynolds number. However, taking both pressure drop and heat transfer effects into account, the overall heat sink performance is shown to be improved at high of Reynolds numbers, volume fractions and fin porosities. Research limitations/implications Thermal radiation and gravity effects are ignored, and thermal equilibrium is assumed between solid and fluid phases. Originality/value A maximum of 32 per cent increase of convective heat transfer is achieved along with a maximum of 33 per cent reduction in the pressure drop using porous fins and ferrofluid in heat sink.

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43

Chen, A.-Li, Zheng-Yang Li, Tian-Xue Ma, Xiao-Shuang Li, and Yue-Sheng Wang. "Heat reduction by thermal wave crystals." International Journal of Heat and Mass Transfer 121 (June 2018): 215–22. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2017.12.136.

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44

Tamayo, Enrique Torres, José W. Morales, Mauro D. Albarracín, Héctor L. Laurencio, Israel P. Pachacama, Brayan I. Guacapiña, and Wilson M. Román. "Cooling Temperature and Heat Transfer Coefficients in Cylindrical Heat Exchangers." International Journal of Mechanics 15 (December 28, 2021): 254–59. http://dx.doi.org/10.46300/9104.2021.15.29.

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The parameters behavior that characterize the process was carried out through an experimental investigation to obtain the cooling temperature, heat transfer coefficients and the heat flow in mineral coolers. The values of water temperature, water flow and mineral temperature were recorded at the inlet and outlet of the cylindrical cooler. Experiments were carried out with five values of the mass flow, keeping the cylinder revolutions constant. The calculation procedure for the system was obtained, in the mineral coolers the heat transfer by conduction, convection and evaporation predominates as a function of the cooling zone. A reduction in temperature is shown with increasing length, the lowest temperature values were obtained for a mass flow of 8 kg/s. The mineral outlet temperature should not exceed 200 oC, therefore it is recommended to work with the mass flow less than 10 kg/s that guarantees the cooling process.

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45

Guo, Lei, Shusheng Zhang, and Jing Hu. "Flow boiling heat transfer characteristics of two-phase flow in microchannels." AIP Advances 12, no. 5 (May 1, 2022): 055219. http://dx.doi.org/10.1063/5.0095786.

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A set of experimental platforms with widths of 0.5, 1.0, 1.5, and 2.0 mm was established to explore the mechanism of flow boiling bubble dynamics in microchannels, focusing on heat transfer characteristics, pressure loss, and two-phase flow pattern identification. Bubble flow, restricted bubble flow, and dry area were observed in all four channels. The appearance of flow pattern was related to flow rate and channel width. Under the condition of the same channel width, the initial heat flux of subcooled boiling gradually increased with increase in flow rate, and this change trend was close to the linear trend. Under the same flow rate, the initial heat flux of subcooled boiling increased with decrease in channel width. This condition was due to the faster flow rate of the working medium in the narrow channel, resulting in decrease of heating time. The increase in bubble generation frequency directly led to the increase in the wall heat transfer coefficient and the decrease in the bubble separation diameter. Mathematical analysis showed that under the condition of small flow, reduction of channel size led to reduction of the total wall heat transfer coefficient. In this condition, reduction of channel size cannot enhance heat transfer. With increasing volume flow rate, the range of hydrodynamic control area increased and the index decreased. When the flow rate was large, the total heat transfer coefficient increased greatly with the decrease in channel size. The theoretical values were in good agreement with the experimental data.

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46

Karayiannis, T. G., and J. D. Tarasuk. "Natural Convection in an Inclined Rectangular Cavity With Different Thermal Boundary Conditions at the Top Plate." Journal of Heat Transfer 110, no. 2 (May 1, 1988): 350–57. http://dx.doi.org/10.1115/1.3250491.

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Natural convection inside a rectangular cavity with different temperature boundary conditions on the cold top plate was studied using a Mach-Zehnder interferometer for θ = 15, 45, and 60 deg to the horizontal. At θ = 60 deg coupling with external forced convection and non-coupled heat transfer from a cavity with an isothermal top plate was studied. In all experiments the bottom hot plate was isothermal. The Rayleigh number Ra was varied from subcritical to 6×105 and the cavity aspect ratio ARx, from 6.68 to 33.4. The Reynolds number of the external forced flow Redh was constant and approximately equal to 5.8×104. It was found that for Ra ≲ 3×104 the differing thermal boundary conditions at the top plate did not affect the local or average heat transfer rates from the cavity. For Ra ≳ 3×104 coupling at the top plate compared to the non-coupled case resulted not only in a reduction in the variation of the local heat transfer rates at the cold plate, but also in a significant reduction in the variation of the average transfer rates from hot and cold plates of the cavity. Forced convection at the top plate as compared to natural convection resulted only in a small reduction in the heat transfer coefficient at the cold plate. Correlation equations for coupled and noncoupled average heat transfer rates are presented.

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47

Razak, N. F. D., M. S. M. Sani, and W. H. Azmi. "Heat Transfer Augmentation in Heat Exchanger by using Nanofluids and Vibration Excitation - A Review." International Journal of Automotive and Mechanical Engineering 17, no. 1 (March 30, 2020): 7719–33. http://dx.doi.org/10.15282/ijame.17.1.2020.19.0574.

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Nanofluids are used in heat exchanger system as efficient heat transfer fluids to improve heat transfer performance by passive method. Besides, another special active technique by implementing the low or high frequency vibration, which was used in heat exchanger to enhance the heat transfer performance. This paper reviews the heat transfer augmentation in heat exchanger by using nanofluids, vibration excitation of low and high frequency vibration. The use of nanofluids in heat exchanger system can provide better effective thermal conductivity compared to the conventional coolants. The presence of nanosize particles in nanofluids performed better mixing flow with higher thermal properties compared to pure fluids. Additionally, the active method by inducing low and high frequency vibration technology was applied in heat exchanger system. The heat transfer augmentation by vibration excitation was resulted from the mitigation of the fouling resistance on the surface of the tube wall. It was found that vibration excitation not only increase the heat transfer rate, but also might be a solution for fouling reduction. Hence, there is a great potential of using nanofluids together with vibration excitation simultaneously in heat exchanger system to improve the heat transfer performance.

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Chicherin, Stanislav. "Analysis of procedures for heating, ventilation and air conditioning for transfer to low-temperature heat supply." Stroitel stvo nauka i obrazovanie [Construction Science and Education], no. 3 (September 30, 2019): 8. http://dx.doi.org/10.22227/2305-5502.2019.3.8.

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Introduction. Renovation of housing stock supposes construction of new buildings, where the main utilities consuming heat energy will be heating and hot water supply (HWS) systems. Under such conditions the task of heat consumption reduction by transfer to low-temperature and use of the associated procedures is relevant. Materials and Methods. Research was performed on the basis of residential and administration buildings designed within the whole Russia, the facilities were selected based on the year of putting into operation and their purpose. The source of data concerning buildings became documents included into the scope of the design and detailed documentation: plans, drawings and explanatory notes. As meeting the demands of hot water supply makes the main contribution to daily nonuniformities of heat energy consumption, the attention was paid to equipment of hot water supply systems. For calculations, the commercial product of Microsoft Office Excel 2010 was used. Results. During selection of roof boiler house as a source of heat supply increase in consumption of equivalent fuel in relation to the variant of connection to heat power plant operating on solid fuel by 187,314 tons of fuel oil equivalent is possible. General refusal from power-and-heat generation complicates operation of large district heat supply systems. The design parameters of coolant in building heating system differ from project to project: from 95/70 °С, used everywhere till the beginning of the XXI century, up to 90/65 °С corresponding to existing practice of designing or 80/60 °С as at the facility in Sevastopol. Reduction of design temperatures by 5 % is insufficient to decrease general heat consumption of the building. Reduction of heat consumption is explained by selection of advanced materials for pipeline heat insulation. Use of automation diagrams for heat points on the basis of regulator ECL Comfort 310 contributes to improvement of hydraulic control for heating systems, however, concealed automation results in violation of high-quality mode for heat network control and decrease of coolant parameters on adjacent (often non-automated) consumers. Conclusions. Supplement of central high-quality control by local constant temperature/variable flow control at individual heat unit and installation of temperature controllers on heating radiators with mechanical thermostatic head have potential for reduction of the heat energy volume used ineffectively. Increase in level of controllability for heating system together with cheaper and responsive automation systems are basic conditions for increase in quality of heat supply in future.

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Qu, Qifeng, Hongwei Zhu, Huan Sun, and Haorong Xu. "Simulation Study on the Effect of Different Fin Spacing on Heat Transfer in Microcolumn Radiator." Journal of Physics: Conference Series 2503, no. 1 (May 1, 2023): 012057. http://dx.doi.org/10.1088/1742-6596/2503/1/012057.

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Abstract In this paper, the heat transfer of microcolumn radiators with different spacing and arrangement was studied. Under the condition of constant heat flux qw , linear arrangement (LA) and cross arrangement (CA) were used to simulate the heat transfer of 10 fin spacing under different mass flow rates. The results show that Nusselt Nu and fin heat transfer coefficient hfin reduce with the increase of the transverse spacing and reduce with the increase of the vertical spacing. The Nusselt Nu and fin heat transfer coefficient hfin with the reduction of the fin spacing, and the changing trend does not change with the change of heat flux qw.

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Łęcki, Marcin, Dariusz Andrzejewski, Artur N. Gutkowski, and Grzegorz Górecki. "Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions." Energies 14, no. 13 (June 23, 2021): 3779. http://dx.doi.org/10.3390/en14133779.

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Plate fin-tube heat exchangers are widely used in air conditioning and refrigeration systems and other industry fields. Various errors made in the manufacturing process can result in the formation of an air gap between the tube and fin. Several numerical simulations were carried out for a symmetric section of plate fin-tube heat exchanger to study the influence of air gap on heat transfer under periodic flow conditions. Different locations and sizes of an air gap spanning 1/2 circumference of the tube were considered for the range of airflow velocities. Velocity and temperature fields for cases with air gap were compared with ideal thermal contact cases. Blocking of heat flow by the gap leads to the reduction of heat transfer rate. Fin discontinuity in the front of the tube causes the smallest reduction of the heat transfer rate in comparison to the ideal tube-fin contact, especially for thin slits. The rear gap position is the worst in the smallest gap range. Therefore, reversing the flow direction can lead to up to a 15% heat transfer increase, if mainly the rear gaps are present. The introduction of a thin slit in the front of the tube leads to convective heat transfer enhancement, which should be further investigated.

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