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Статті в журналах з теми "Transient heat flux"

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Автор: Grafiati

Опубліковано: 30 травня 2022

Оновлено: 31 травня 2022

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1

Martins, N., H. Calisto, N. Afgan, and A. I. Leontiev. "The transient transpiration heat flux meter." Applied Thermal Engineering 26, no. 14-15 (October 2006): 1552–55. http://dx.doi.org/10.1016/j.applthermaleng.2005.11.027.

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2

Alkidas, A. C., and R. M. Cole. "Transient Heat Flux Measurements in a Divided-Chamber Diesel Engine." Journal of Heat Transfer 107, no. 2 (May 1, 1985): 439–44. http://dx.doi.org/10.1115/1.3247434.

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Transient surface heat flux measurements were performed at several locations on the cylinder head of a divided-chamber diesel engine. The local heat flux histories were found to be significantly different. These differences are attributed to the spatial nonuniformity of the fluid motion and combustion. Both local time-averaged and local peak heat fluxes decreased with decreasing speed and load. Retarding the combustion timing beyond TDC decreased the peak heat flux in the antechamber but increased the peak heat flux in the main chamber. This is attributed to the relative increase in the portion of fuel that burns in the main chamber with retarded combustion timing.

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3

Narayana, Supradeep, Salvatore Savo, and Yuki Sato. "Transient heat flux shielding using thermal metamaterials." Applied Physics Letters 102, no. 20 (May 20, 2013): 201904. http://dx.doi.org/10.1063/1.4807744.

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4

Chang, S. H., K. W. Lee, and D. C. Groeneveld. "Transient-Effects modeling of critical heat flux." Nuclear Engineering and Design 113, no. 1 (April 1989): 51–57. http://dx.doi.org/10.1016/0029-5493(89)90295-1.

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5

Buttsworth, D. R. "Transient response of an erodable heat flux gauge using finite element analysis." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 216, no. 8 (August 1, 2002): 701–6. http://dx.doi.org/10.1177/095440700221600808.

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The transient response of an erodable ribbon element heat flux gauge has been assessed using a two-dimensional finite element (FE) analysis. Such transient heat flux gauges have previously been used for measurements in internal combustion (IC) engines. To identify the heat flux from the measurements of surface temperature, it is commonly assumed that the heat transfer within these devices is one-dimensional. A corollary of the one-dimensional treatment is that only one value of the thermal product, , is needed for identification of the transient heat flux, even though erodable heat flux gauges are constructed from at least two different materials. The current results demonstrate that two-dimensional transient heat conduction effects have a significant influence on the surface temperature measurements made with these devices. For the ribbon element gauge and timescales of interest in IC engine studies, using a one-dimensional analysis (and hence a single value of ) will lead to substantial inaccuracy in the derived heat flux measurements.

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6

Fan, Chao, Yanqiang Bi, Jing Wang, Guoqing Liu, and Zhihai Xiang. "Experimental Investigation of Heat Flux Characteristics on the Thermally Induced Vibration of a Slender Thin-Walled Beam." International Journal of Applied Mechanics 12, no. 05 (June 2020): 2050053. http://dx.doi.org/10.1142/s1758825120500532.

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The spacecraft with large flexible space structures may be subject to the thermally induced vibration (TIV) due to the rapidly changed solar heat flux when it enters and leaves the eclipse, which would lead to certain spacecraft failure. This paper reports a laboratory experiment that aims to study the impact of transient characteristics of heat flux on the ground experiment of TIV. In the experiments on the TIV of a slender thin-walled beam, two different methods of providing transient heat flux were considered, and the process of entering and leaving eclipse was simulated, respectively. The experimental results demonstrate that different transient characteristics of heat flux will have large impact on the TIV of the specimen, and the ideal theoretical estimation of thermal characteristic time has limitations in practical engineering. In addition, it is found that the traditional way of simulating solar heat flux by turning on/off infrared heat lamps is not suitable for the TIV ground experiment. Instead, a transient heat flux simulation method by moving the baffle is recommended.

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7

Zarko, V. E. "Mathematical simulation of transient combustion of melted energetic materials." Chemical Bulletin of Kazakh National University, no. 3 (September 30, 2019): 4–10. http://dx.doi.org/10.15328/cb1079.

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The computer code is elaborated for numerical simulation of transient combustion of energetic materials (EM) subjected to the action of time-dependent heat flux and under transient pressure conditions. It allows studying combustion response upon interrupted irradiation (transient pressure) and under action of periodically varied heat flux (pressure) in order to determine stability of ignition transients and parameters of transient combustion. The originally solid EM melts and then evaporates at the surface. It is assumed that chemical transformations occur both in the condensed and gas phases. At the burning surface, the phase transition condition in the form of Clapeyron-Clausius law for equilibrium evaporation is formulated that corresponds to the case of combustion of sublimated or melted EM. The paper contains description of transient combustion problem formulation and several examples of transient combustion modeling. At present time a precise prediction of transient burning rate characteristics is impossible because of the lack of information about magnitude of EM parameters at high temperatures. However, the simulation results bring valuable qualitative information about burning rate behavior at variations in time of external conditions – radiant flux and pressure.

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8

Tenzer, Fabian M., Ilia V. Roisman, and Cameron Tropea. "Fast transient spray cooling of a hot thick target." Journal of Fluid Mechanics 881 (October 24, 2019): 84–103. http://dx.doi.org/10.1017/jfm.2019.743.

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Spray cooling of a hot target is characterized by strong heat flux and fast change of the temperature of the wall interface. The heat flux during spray cooling is determined by the instantaneous substrate temperature, which is illustrated by boiling curves. The variation of the heat flux is especially notable during different thermodynamic regimes: film, transitional and nucleate boiling. In this study transient boiling curves are obtained by measurement of the local and instantaneous heat flux produced by sprays of variable mass flux, drop diameter and impact velocity. These spray parameters are accurately characterized using a phase Doppler instrument and a patternator. The hydrodynamic phenomena of spray impact during various thermodynamic regimes are observed using a high-speed video system. A theoretical model has been developed for heat conduction in the thin expanding thermal boundary layer in the substrate. The theory is able to predict the evolution of the target temperature in time in the film boiling regime. Moreover, a remote asymptotic solution for the heat flux during the fully developed nucleate boiling regime is developed. The theoretical predictions agree very well with the experimental data for a wide range of impact parameters.

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9

Nakamura, Yuji, Katsuya Fukuda, Qiusheng Liu, Makoto Shibahara, and Koichi Hata. "Transient Critical Heat Flux in Vertical Small Tube." Proceedings of Conference of Kansai Branch 2018.93 (2018): 803. http://dx.doi.org/10.1299/jsmekansai.2018.93.803.

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10

Kulish, V. V., and J. L. Lage. "Fractional-Diffusion Solutions for Transient Local Temperature and Heat Flux." Journal of Heat Transfer 122, no. 2 (December 9, 1999): 372–76. http://dx.doi.org/10.1115/1.521474.

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Applying properties of the Laplace transform, the transient heat diffusion equation can be transformed into a fractional (extraordinary) differential equation. This equation can then be modified, using the Fourier Law, into a unique expression relating the local value of the time-varying temperature (or heat flux) and the corresponding transient heat flux (or temperature). We demonstrate that the transformation into a fractional equation requires the assumption of unidirectional heat transport through a semi-infinite domain. Even considering this limitation, the transformed equation leads to a very simple relation between local time-varying temperature and heat flux. When applied along the boundary of the domain, the analytical expression determines the local time-variation of surface temperature (or heat flux) without having to solve the diffusion equation within the entire domain. The simplicity of the solution procedure, together with some introductory concepts of fractional derivatives, is highlighted considering some transient heat transfer problems with known analytical solutions. [S0022-1481(00)01002-1]

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11

Goto, Takanobu, and Masaaki Suzuki. "BIE analysis of transient heat transfer driven by high heat flux." Fusion Engineering and Design 39-40 (September 1998): 317–22. http://dx.doi.org/10.1016/s0920-3796(98)00177-x.

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12

Wang, Xuwen, Qiusheng Liu, Zhiqiang Zhu, and Xue Chen. "Experiments of Transient Condensation Heat Transfer on the Heat Flux Senor." Microgravity Science and Technology 27, no. 5 (April 24, 2015): 369–76. http://dx.doi.org/10.1007/s12217-015-9427-z.

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13

Ma, Tengyue, Baosheng Wang, Xiuhuan Tang, Pan Hu, Zhenhui Ma, Xinbiao Jiang, and Huiping Guo. "Studies on heat transfer characteristics of vapor chamber under periodic-pulsed heat source." Advances in Mechanical Engineering 14, no. 4 (April 2022): 168781322210897. http://dx.doi.org/10.1177/16878132221089797.

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In a high-power microwave device, the intense electron beam causes a high-heat-flux on the collector’s inner surface which results in an instant temperature increase which eventually causes the output power to drop. The vapor chamber is one of the passive cooling devices effective for high-heat-flux heat dissipation. To study the heat dissipation capacity and the surface temperature control effect of the vapor chamber, a numerical heat transfer model of the vapor chamber is proposed based on the effective thermal conductivity method. The accuracy of the steady-state heat transfer analysis and the applicability of the transient simulation are verified by comparing with experimental data, and the heat transfer are calculated under the condition of periodic pulsed heat sources. Lastly, the transient performance of a vapor chamber relative to a copper heat spreader of the same external dimensions is investigated as a function of the wick effective thermal conductivity, pulsed heat flux, and pulse duration. The transient behavior of the vapor chambers are examined to find a performance threshold to determine if the performance is superior to that of a copper heat spreader. The present work provides a basis to understand the advantages and limitations of metal heat spreader in pulse mode operation of vapor chamber and plays a vital role in the design of improving transient performance.

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14

Park, Hye-Jun, Hyun-Jung Kim, and Kyung-Hi Hong. "Transient Heat Flux Evaluation of Underwear for Protective Clothing using Sweating Manikin." Journal of the Korean Society of Clothing and Textiles 32, no. 1 (January 31, 2008): 157–65. http://dx.doi.org/10.5850/jksct.2008.32.1.157.

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15

Lund, K. O. "A Direct-Heating Energy-Storage Receiver for Dish-Stirling Solar Energy Systems." Journal of Solar Energy Engineering 118, no. 1 (February 1, 1996): 15–19. http://dx.doi.org/10.1115/1.2847900.

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Dish-Stirling solar receiver designs are investigated and evaluated for possible use with sensible energy storage in single-phase materials. The designs differ from previous receivers in utilizing axial conduction in the storage material for attenuation of the solar flux transients due to intermittent cloud cover, and in having convective heat removal at the base of the receiver. One-dimensional, time-dependent heat transfer equations are formulated for the storage material temperature field, including losses to the environment, and a general heat exchange effectiveness boundary condition at the base. The solar source flux is represented as the sum of steady and periodic cloud-transient components, with the steady component solved subject to specified receiver thermal efficiency. For the transient cloud-cover component the Fast Fourier Transform algorithm (FFT) is applied, and the complex transfer function of the receiver is obtained as a filter for the input flux spectrum. Inverse transformation results in the amplitudes and mode shapes of the transient temperature component. By adjustment of design parameters, the cloud-cover amplitude variations of the outlet gas temperature can be limited to acceptable magnitudes, thus simplifying control systems.

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16

Pasamehmetoglu, K. O., R. A. Nelson, and F. S. Gunnerson. "Critical Heat Flux Modeling in Forced Convection Boiling During Power Transients." Journal of Heat Transfer 112, no. 4 (November 1, 1990): 1058–62. http://dx.doi.org/10.1115/1.2910478.

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In this paper, a theoretical prediction of critical heat flux (CHF) during power transients in forced convective boiling is presented. The analysis is restricted to departure from nucleate boiling (DNB) type of CHF at low qualities. The developed theory is compared with the experimental data available in the literature. The agreement is exceptionally good. The new model also is compared with the semi-empirical transient CHF model in the literature.

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17

Alam, Tanweer, and Rakesh Kumar. "Heat flux measurement analysis from thin film gauge in convective heat transfer mode." Transactions of the Institute of Measurement and Control 41, no. 1 (February 22, 2018): 64–73. http://dx.doi.org/10.1177/0142331217752041.

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In many research activities related to the heated environment near the wall or surface, measurement of transient surface temperature and determination of convective heating rate is one of the most important tasks. Since the effective measurement time available for the regime to enumerate is very small, it is essential to use temperature detectors with highly sensitive, precise and instantaneous temperature measurement properties. Thin film gauges with these properties are best suited for such short duration transient surface temperature measurements. This study focuses on the establishment of new calibration technique in convection heat transfer mode. A fabricated calibration set-up is used to supply the heat flux to the thin film gauge, which is in-house built with platinum as sensing element and quartz as an insulating substrate. The heat load applied on the thin film gauge is of impact or step type. The deduction of heat flux value is carried out with recorded transient temperature data. Moreover, the numerical analysis is also carried out to get the heat flux values. The authenticity of the experimental set up and thin film gauge effectiveness is supported by the excellent agreement of the experimental and numerical results.

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18

Huang, Boyin, Peter H. Stone, Andrei P. Sokolov, and Igor V. Kamenkovich. "The Deep-Ocean Heat Uptake in Transient Climate Change." Journal of Climate 16, no. 9 (May 1, 2003): 1352–63. http://dx.doi.org/10.1175/1520-0442-16.9.1352.

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Abstract The deep-ocean heat uptake (DOHU) in transient climate changes is studied using an ocean general circulation model (OGCM) and its adjoint. The model configuration consists of idealized Pacific and Atlantic basins. The model is forced with the anomalies of surface heat and freshwater fluxes from a global warming scenario with a coupled model using the same ocean configuration. In the global warming scenario, CO2 concentration increases 1% yr−1. The heat uptake calculated from the coupled model and from the adjoint are virtually identical, showing that the heat uptake by the OGCM is a linear process. After 70 yr the ocean heat uptake is almost evenly distributed within the layers above 200 m, between 200 and 700 m, and below 700 m (about 20 × 1022 J in each). The effect of anomalous surface freshwater flux on the DOHU is negligible. Analysis of the Coupled Model Intercomparison Project (CMIP-2) data for the same global warming scenario shows that qualitatively similar results apply to coupled atmosphere–ocean GCMs. The penetration of surface heat flux to the deep ocean in the OGCM occurs mainly in the North Atlantic and the Southern Ocean, since both the sensitivity of DOHU to the surface heat flux and the magnitude of anomalous surface heat flux are large in these two regions. The DOHU relies on the reduction of convection and Gent–McWilliams–Redi mixing in the North Atlantic, and the reduction of Gent–McWilliams–Redi mixing in the Southern Ocean.

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19

Holmberg, D. G., and T. E. Diller. "High-Frequency Heat Flux Sensor Calibration and Modeling." Journal of Fluids Engineering 117, no. 4 (December 1, 1995): 659–64. http://dx.doi.org/10.1115/1.2817319.

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A new method of in-situ heat flux gage calibration is evaluated for use in convective facilities with high heat transfer and fast time response. A Heat Flux Microsensor (HFM) was used in a shock tunnel to simultaneously measure time-resolved surface heat flux and temperature from two sensors fabricated on the same substrate. A method is demonstrated for estimating gage sensitivity and frequency response from the data generated during normal transient test runs. To verify heat flux sensitivity, shock tunnel data are processed according to a one-dimensional semi-infinite conduction model based on measured thermal properties for the gage substrate. Heat flux signals are converted to temperature, and vice versa. Comparing measured and calculated temperatures allows an independent calibration of sensitivity for each data set. The results match gage calibrations performed in convection at the stagnation point of a free jet and done by the manufacturer using radiation. In addition, a finite-difference model of the transient behavior of the heat flux sensor is presented to demonstrate the first-order response to a step input in heat flux. Results are compared with shock passing data from the shock tunnel. The Heat Flux Microsensor recorded the heat flux response with an estimated time constant of 6 μs, which demonstrates a frequency response covering DC to above 100 kHz.

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20

Alassar, Rajai, Mohammed Abushosha, and Mohammed El-Gebeily. "TRANSIENT HEAT CONDUCTION FROM SPHEROIDS." Transactions of the Canadian Society for Mechanical Engineering 38, no. 3 (September 2014): 373–89. http://dx.doi.org/10.1139/tcsme-2014-0027.

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We study the unsteady heat conduction from a spheroid (prolate or oblate) initially heated and then left to cool in an unbounded medium of constant temperature. We present two solutions of the problem. The first makes use of the spheroidal wave functions as basis. The second, which is numerical, is obtained by expanding the dimensionless temperature in terms of Legendre functions and then solving the resulting set of differential equations in the radial direction using an implicit finite difference scheme. The two solutions are further verified by comparing them to the limiting case of a sphere. We study the effect of the axis ratio on the time development of temperature inside the spheroid and the heat flux across the surface.

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21

Cui, Miao, Kai Yang, Yun-fei Liu, and Xiao-wei Gao. "Inverse Estimation of Transient Heat Flux to Slab Surface." Journal of Iron and Steel Research International 19, no. 11 (November 2012): 13–18. http://dx.doi.org/10.1016/s1006-706x(13)60014-x.

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22

Meingast, U., L. Reichelt, and U. Renz. "Measuring transient wall heat flux under diesel engine conditions." International Journal of Engine Research 5, no. 5 (October 2004): 443–52. http://dx.doi.org/10.1243/1468087042320960.

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23

Sanderson, S. R., and B. Sturtevant. "Transient heat flux measurement using a surface junction thermocouple." Review of Scientific Instruments 73, no. 7 (July 2002): 2781–87. http://dx.doi.org/10.1063/1.1484255.

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24

Khatib-Rahbar, M., and E. G. Cazzoli. "Flow Excursion-Induced Dryout at Low Heat Flux Natural Convection Boiling." Journal of Heat Transfer 108, no. 2 (May 1, 1986): 425–32. http://dx.doi.org/10.1115/1.3246941.

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Flow excursion-induced dryout at low heat flux natural convection boiling, typical of liquid metal fast breeder reactors, is addressed. Steady-state calculations indicate that low-quality boiling is possible up to the point of the Ledinegg instability, leading to flow excursion and subsequent dryout in agreement with experimental data. A flow regime-dependent critical heat flux relationship based upon a saturated boiling criterion is also presented. Transient analyses indicate that premature flow excursion cannot be ruled out and the boiling process is transient dependent. Analysis of a loss-of-flow transient at high heat flux forced convection shows a significantly faster flow excursion leading to dryout, which is in excellent agreement with the results of the two-dimensional THORAX code.

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25

Chen, J. C., and K. K. Hsu. "Heat Transfer During Liquid Contact on Superheated Surfaces." Journal of Heat Transfer 117, no. 3 (August 1, 1995): 693–97. http://dx.doi.org/10.1115/1.2822632.

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Several boiling regimes are characterized by intermittent contacts of vapor and liquid at the superheated wall surface. A microthermocouple probe was developed capable of detecting transient surface temperatures with a response time better than 1 ms. The transient temperature data were utilized to determine the time-varying heat flux under liquid contacts. The instantaneous surface heat flux was found to vary by orders of magnitude during the milliseconds of liquid residence at the hot surface. The average heat flux during liquid contact was found to range from 105 to 107 W/m2 for water at atmospheric pressure, as wall superheat was varied from 50 to 450°C.

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26

Roedig, M., I. Kupriyanov, J. Linke, X. Liu, and Zh Wang. "Simulation of transient heat loads on high heat flux materials and components." Journal of Nuclear Materials 417, no. 1-3 (October 2011): 761–64. http://dx.doi.org/10.1016/j.jnucmat.2010.12.139.

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27

Kung, Kuang Yuan, and H. M. Srivastava. "Analytic transient solutions of a cylindrical heat equation with oscillating heat flux." Applied Mathematics and Computation 195, no. 2 (February 2008): 745–53. http://dx.doi.org/10.1016/j.amc.2007.05.019.

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28

Kumar, R., A. K. Vashishth, and S. Ghangas. "Phase-Lag Effects in Skin Tissue During Transient Heating." International Journal of Applied Mechanics and Engineering 24, no. 3 (August 1, 2019): 603–23. http://dx.doi.org/10.2478/ijame-2019-0038.

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Abstract A three-phase-lag (TPL) model is proposed to describe heat transfer in a finite domain skin tissue with temperature dependent metabolic heat generation. The Laplace transform method is applied to solve the problem. Three special types of heat flux are applied to the boundary of skin tissue for thermal therapeutic applications. The depth of tissue is influenced by the different oscillation heat flux. The comparison between the TPL and dual-phase-lag (DPL) models is analyzed and the effects of phase lag parameters (τq, τt and τv) and material (k*) on the tissue temperature distribution are presented graphically.

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29

Zhou, Nianyong, Hao Feng, Muhao Xu, and Enhai Liu. "Heat transfer performance and influences of spray cooling under quenching." Thermal Science, no. 00 (2020): 349. http://dx.doi.org/10.2298/tsci200825349z.

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In this study, a closed-loop spray cooling system using R134a as the working fluid was established. The heat transfer characteristics and influencing mechanism of transient spray cooling were studied. The transient spray cooling curve under quenching was built accurately. The results show that the vapor film suppressed time tsup is the main period that the spray cooling must pass through. The flow rate and the sub-cooling of R134a have little effect on the cooling rate but the critical heat flux, which are mainly affected by chamber pressure. The transient Jacob number Ja+ decreases with the increases of chamber pressure. As Ja+ decreases, the growth of vapor film is inhibited, then the tsup reduces in consequence. The surface temperature drop point and critical heat flux increases with the rise of chamber pressure. The maximum critical heat flux is 70.08 W/cm2in this experiment.

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30

Childs, P. R. N., J. R. Greenwood, and C. A. Long. "Heat flux measurement techniques." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 213, no. 7 (July 1, 1999): 655–77. http://dx.doi.org/10.1177/095440629921300702.

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Heat flux measurement is used in the field of fluid mechanics and heat transfer to quantify the transfer of heat within systems. Several techniques are in common use, including: differential temperature sensors such as thermopile, layered resistance temperature devices or thermocouples and Gardon gauges; calorimetric methods involving a heat balance analysis and transient monitoring of a representative temperature, using, for example, thin-film temperature sensors or temperature sensitive liquid crystals; energy supply or removal methods using, for example, a heater to generate a thermal balance; and, finally, by measurement of mass transfer which can be linked to heat transfer using the analogy between the two. No one method is suitable to all applications because of the differing considerations of accuracy, sensitivity, size, cost and robustness. Recent developments including the widespread availability and application of thin-film deposition techniques for metals and ceramics, allied with advances in microtechnology, have expanded the range of devices available for heat flux measurement. This paper reviews the various types of heat flux sensors available, as well as unique designs for specific applications. Critical to the use of a heat flux measurement technique is accurate calibration. Use of unmatched materials disturbs the local heat flux and also the local convective boundary layer, producing a potential error that must be compensated for. The various techniques in common use for calibration are described. A guide to the appropriate selection of a heat flux measurement technique is provided according to the demands of response, sensitivity, temperature of operation, heat flux intensity, manufacturing constraints, commercial availability, cost, thermal disturbance and acceleration capability for vibrating, rotating and reciprocating applications.

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31

Zumbrunnen, D. A. "Transient Convective Heat Transfer in Planar Stagnation Flows With Time-Varying Surface Heat Flux and Temperature." Journal of Heat Transfer 114, no. 1 (February 1, 1992): 85–93. http://dx.doi.org/10.1115/1.2911272.

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Impinging flows are used in a variety of applications where effective and localized heat transfer is mandated by short residence times or by space constraints, as in cooling materials moving along a conveyor or removing heat dissipated within microelectronic circuitry. A wide selection of heat transfer correlations is available for steady-state conditions. However, instantaneous heat transfer coefficients can differ significantly from steady-state values when temporal variations occur in the surface heat flux or surface temperature. Under these conditions, the temperatures of fluid layers near the surface are affected preferentially due to their proximity to the temporal variation. A theoretical model is formulated to assess the importance of a time-varying surface heat flux or temperature on convective heat transfer in a steady, planar stagnation flow. A governing equation for the transient heat transfer response is formulated analytically from the boundary layer equations for momentum and energy conservation in the fluid. Numerical solutions to the governing equation are determined for ramp and sinusoidal changes in the surface heat flux or temperature. Results indicate that the time response is chiefly governed by the velocity gradient in the free stream and to a lesser extent by the Prandtl number. Departures from steady-state Nusselt numbers are larger for more rapid transients and smaller or comparable in size to the magnitude of the imposed variation at the surface.

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32

Jen, Tien-Chien, Sunil Eapen, and Gustavo Gutierrez. "Nonlinear Numerical Analysis in Transient Cutting Tool Temperatures." Journal of Manufacturing Science and Engineering 125, no. 1 (February 1, 2003): 48–56. http://dx.doi.org/10.1115/1.1536173.

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In any cutting processes, the temperature distribution in the cutting tool is intrinsically three-dimensional and very steep temperature gradient can be generated in the vicinity of the tool-chip interface. In this region, where the maximum temperature occurs, the effect of temperature dependent thermal properties may become important. The full three-dimensional nonlinear transient heat conduction equation is solved numerically using a control volume approach to study these nonlinear effects on cutting tool temperatures. The extremely small size of the heat input zone (tool-chip interface), relative to the tool insert rake surface area, requires the mesh to be dense enough in order to obtain accurate solutions. This usually requires very intensive computational efforts. Due to the size of the discretized domain, an optimized algorithm is used in the solution of the problem to significantly reduce the required computing time. This numerical model can be used for process development in an industrial setting. The effect of two different heat flux input profiles, a spatially uniform plane heat flux and a spatially nonuniform parabolic heat flux at the tool-chip interface, on the tool temperatures are also investigated in the present study. Some recommendations are given regarding the condition when these nonlinear effects cannot be ignored.

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33

Miao, Shuangshuang, Jiajia Sui, Yulong Zhang, Feng Yao, and Xiangdong Liu. "Experimental Study on Thermal Performance of a Bent Copper-Water Heat Pipe." International Journal of Aerospace Engineering 2020 (June 30, 2020): 1–10. http://dx.doi.org/10.1155/2020/8632152.

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Vapor-liquid phase change is regarded as an efficient cooling method for high-heat-flux electronic components. The copper-water bent heat pipes are particularly suited to the circumstances of confined space or misplaced heat and cold sources for high-heat-flux electronic components. In this paper, the steady and transient thermal performance of a bent copper-water heat pipe is studied based on a performance test system. The effects of cooling temperature, working conditions on the critical heat flux, and equivalent thermal conductivity have been examined and analyzed. Moreover, the influences of heat input and working conditions on the thermal response of a bent heat pipe have also been discussed. The results indicate that the critical heat flux is enhanced due to the increases in cooling temperature and the lengths of the evaporator and condenser. In addition, the critical heat flux is improved by extending the cooling length only when the operating temperature is higher than 50°C. The improvement on the equivalent thermal by increasing the heating length is more evident than that by increasing cooling length. It is also demonstrated by the experiment that the bent copper-water heat pipe can respond quickly to the variation of heat input and possesses superior transient heat transfer performance.

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34

Hager, J. M., S. Simmons, D. Smith, S. Onishi, L. W. Langley, and T. E. Diller. "Experimental Performance of a Heat Flux Microsensor." Journal of Engineering for Gas Turbines and Power 113, no. 2 (April 1, 1991): 246–50. http://dx.doi.org/10.1115/1.2906555.

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The performance characteristics of a heat flux microsensor have been measured and analyzed. This is a new heat flux gage system that is made using microfabrication techniques. The gages are small, have high frequency response, can measure very high heat flux, and output a voltage directly proportional to the heat flux. Each gage consists of a thin thermal resistance layer sandwiched between many thermocouple pairs forming a differential thermopile. Because the gage is made directly on the measurement surface and the total thickness is less than 2 μm, the presence of the gage contributes negligible flow and thermal disruption. The active surface area of the gage is 3 mm by 4 mm, with the leads attached outside this area to relay the surface heat flux and temperature signals. Gages were made and tested on glass and silicon substrates. The steady and unsteady response was measured experimentally and compared with analytical predictions. The analysis was performed using a one-dimensional, transient, finite-difference model of the six layers comprising the gage plus the substrate. Steady-state calibrations were done on a convection heat transfer apparatus and the transient response was measured to step changes of the imposed radiative flux. As an example of the potential capabilities, the time-resolved heat flux was measured at a stagnation point with imposed free-stream turbulence. A hot-film probe placed outside the boundary layer was used to provide a simultaneous signal showing the corresponding turbulent velocity fluctuations.

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35

Ivanovic, Ivana, Aleksandar Sedmak, Marko Milos, Aleksandar Zivkovic, and Mirjana Lazic. "Numerical study of transient three-dimensional heat conduction problem with a moving heat source." Thermal Science 15, no. 1 (2011): 257–66. http://dx.doi.org/10.2298/tsci1101257i.

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A numerical study of transient three-dimensional heat conduction problem with a moving source is presented. For numerical solution Douglas-Gunn alternating direction implicit method is applied and for the moving heat source flux distribution Gaussian function is used. An influence on numerical solution of input parameters figuring in flux boundary conditions is examined. This include parameters appearing in Gaussian function and heat transfer coefficient from free convection boundaries. Sensitivity of cooling time from 800 to 500?C with respect to input parameters is also tested.

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36

Xiao, Dong, and Hongli Ren. "Interdecadal changes in synoptic transient eddy activity over the Northeast Pacific and their role in tropospheric Arctic amplification." Climate Dynamics 57, no. 3-4 (April 3, 2021): 993–1008. http://dx.doi.org/10.1007/s00382-021-05752-6.

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AbstractArctic amplification refers to the greater surface warming of the Arctic than of other regions during recent decades. A similar phenomenon occurs in the troposphere and is termed “tropospheric Arctic amplification” (TAA). The poleward eddy heat flux and eddy moisture flux are critical to Arctic warming. In this study, we investigate the synoptic transient eddy activity over the North Pacific associated with TAA and its relationship with the subtropical jet stream, and propose the following mechanism. A poleward shift of the subtropical jet axis results in anomalies of the meridional gradient of zonal wind over the North Pacific, which drive a meridional dipole pattern of synoptic transient wave intensity over the North Pacific, referred to as the North Pacific Synoptic Transient wave intensity Dipole (NPSTD). The NPSTD index underwent an interdecadal shift in the late 1990s accompanying that of the subtropical jet stream. During the positive phase of the NPSTD index, synoptic eddy heat flux transports more heat to the Arctic Circle, and the eddy heat flux diverges, increasing Arctic temperature. This mechanism highlights the need to consider synoptic transient eddy activity over the North Pacific as the link between the mean state of the North Pacific subtropical upper jet and TAA.

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37

Prajapati, Yogesh K., Manabendra Pathak, and Mohd Kaleem Khan. "Transient Analysis of Microchannel Heat Sink during Single Phase and Flow Boiling Conditions." Applied Mechanics and Materials 819 (January 2016): 101–6. http://dx.doi.org/10.4028/www.scientific.net/amm.819.101.

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In the present work, an experimental investigation has been made to analyze the performance of microchannel heat sink under transient operating conditions. The transient analysis has been made by estimating the response time for different input heat flux and coolant mass flow rate. Analysis has been made for rectangular cross-section microchannels fabricated on a copper block of size 25.7 × 12 × 10 mm3. Twelve (12) numbers of microchannels are fabricated in the copper block. The width and depth of individual channels are 400 μm and 750 μm respectively. Performance analysis has been made for both single phase and flow boiling conditions of the coolant flow using deionized water as coolant. Experiments have been performed for coolant mass flux (G) range of 90 - 250 kg/m2s and input heat flux (q) range of 20 - 300 kW/m2 respectively. It has been observed that at constant input heat flux, response time decreases with the increase in coolant mass flux during single phase cooling. However this trend is not strongly followed during the two-phase or flow boiling cooling condition.

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38

Tung, V. X., and V. K. Dhir. "Experimental Study of Boiling Heat Transfer From a Sphere Embedded in a Liquid-Saturated Porous Medium." Journal of Heat Transfer 112, no. 3 (August 1, 1990): 736–43. http://dx.doi.org/10.1115/1.2910448.

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Boiling heat transfer from a sphere embedded in a porous medium composed of nonheated glass particles was studied under steady-state and transient quenching conditions. In the experiments, the diameter of the nonheated glass particles forming the porous layers was varied parametrically. Freon-113 was used as the test liquid. Experimental results showed that the maximum heat flux increased monotonically with increasing glass particle diameter and approached an asymptotic value corresponding to the maximum heat flux obtained in a pool free of glass particles. It was also observed that the minimum heat flux was nearly insensitive to the particle size and the film boiling heat transfer coefficient increased slightly with decreasing particle size. In the nucleate boiling region, the heat transfer coefficient showed a much weaker dependence on wall superheat in the presence of particles. Transient data indicated that the surface temperature was not uniform during quenching. Therefore, different maximum heat fluxes were obtained depending on the location of the thermocouple whose temperature history was employed in recovering the transient boiling curve. However, for some applications, cooling rates predicted by imposing the steady-state boiling curve may not be in large error.

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39

Min Han Htet, Rie SAKAMOTO, Katsuya FUKUDA, and Qiusheng LIU. "407 Transient Boiling Critical Heat Flux on Horizontal Vertically-Oriented Ribbon with Treated Surface in Pool of Water." Proceedings of Conference of Kansai Branch 2015.90 (2015): 118–21. http://dx.doi.org/10.1299/jsmekansai.2015.90.118.

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40

Jing, Yan, and Qang Han Fang. "A New Grinding Heat Flux Distribution Developed by Theoretical Derivation." Advanced Materials Research 774-776 (September 2013): 1160–63. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.1160.

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Heat flux distribution has an important influence on grinding thermal field, therefore an accurate heat flux distribution model must be established in order to precisely simulate the grinding process. A new heat flux distribution model was developed by theoretical derivation in this paper. In order to simulate the transient grinding thermal field, finite element models were created, applied with the new, uniform and triangular heat flux models respectively. Comparisons between the distributions of temperatures and temperature histories calculated from numerical simulations using the three different models were also made in this paper.

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41

Mohammed, Hussein, Hanim Salleh, and Mohd Yusoff. "The transient response for different types of erodable surface thermocouples using finite element analysis." Thermal Science 11, no. 4 (2007): 49–64. http://dx.doi.org/10.2298/tsci0704049m.

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The transient response of erodable surface thermocouples has been numerically assessed by using a two dimensional finite element analysis. Four types of base metal erodable surface thermocouples have been examined in this study, included type-K (alumel-chromel), type-E (chromel-constantan), type-T (copper-constantan), and type-J (iron-constantan) with 50 mm thick- ness for each. The practical importance of these types of thermocouples is to be used in internal combustion engine studies and aerodynamics experiments. The step heat flux was applied at the surface of the thermocouple model. The heat flux from the measurements of the surface temperature can be commonly identified by assuming that the heat transfer within these devices is one-dimensional. The surface temperature histories at different positions along the thermocouple are presented. The normalized surface temperature histories at the center of the thermocouple for different types at different response time are also depicted. The thermocouple response to different heat flux variations were considered by using a square heat flux with 2 ms width, a sinusoidal surface heat flux variation width 10 ms period and repeated heat flux variation with 2 ms width. The present results demonstrate that the two dimensional transient heat conduction effects have a significant influence on the surface temperature history measurements made with these devices. It was observed that the surface temperature history and the transient response for thermocouple type-E are higher than that for other types due to the thermal properties of this thermocouple. It was concluded that the thermal properties of the surrounding material do have an impact, but the properties of the thermocouple and the insulation materials also make an important contribution to the net response.

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42

Azerou, B., B. Garnier, and J. Lahmar. "Thin film heat flux sensors for accurate transient and unidirectional heat transfer analysis." Journal of Physics: Conference Series 395 (November 26, 2012): 012084. http://dx.doi.org/10.1088/1742-6596/395/1/012084.

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43

Reichelt, L., U. Meingast, and U. Renz. "Calculating transient wall heat flux from measurements of surface temperature." International Journal of Heat and Mass Transfer 45, no. 3 (January 2002): 579–84. http://dx.doi.org/10.1016/s0017-9310(01)00157-0.

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44

Chen, Y., F. Arbeiter, V. Heinzel, and G. Schlindwein. "Transient conjugated heat transfer within IFMIF high flux test module." Nuclear Engineering and Design 249 (August 2012): 172–79. http://dx.doi.org/10.1016/j.nucengdes.2011.07.051.

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45

Buttsworth, David R., Robert Stevens, and C. Richard Stone. "Eroding ribbon thermocouples: impulse response and transient heat flux analysis." Measurement Science and Technology 16, no. 7 (June 15, 2005): 1487–94. http://dx.doi.org/10.1088/0957-0233/16/7/011.

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46

Manjhi, Sanjeev Kumar, and Rakesh Kumar. "Stagnation point transient heat flux measurement analysis from coaxial thermocouples." Experimental Heat Transfer 31, no. 5 (February 12, 2018): 405–24. http://dx.doi.org/10.1080/08916152.2018.1431738.

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47

Deng, Huachao, Bo Yan, Honghong Su, Xiaomin Zhang, and Xin Lv. "Study on transient heat flux intensity factor with interaction integral." International Journal of Thermal Sciences 146 (December 2019): 106014. http://dx.doi.org/10.1016/j.ijthermalsci.2019.106014.

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48

Orlande, H. R. B., and M. N. O¨zis¸ik. "Transient Thermal Constriction Resistance in a Finite Heat Flux Tube." Journal of Heat Transfer 117, no. 3 (August 1, 1995): 748–51. http://dx.doi.org/10.1115/1.2822639.

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49

Polat, S., A. R. P. Van Heiningen, and W. J. M. Douglas. "Sensor for transient heat flux at a surface with throughflow." International Journal of Heat and Mass Transfer 34, no. 6 (June 1991): 1515–23. http://dx.doi.org/10.1016/0017-9310(91)90293-n.

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50

Feng, Z. C., J. K. Chen, Yuwen Zhang, and Stephen Montgomery-Smith. "Temperature and heat flux estimation from sampled transient sensor measurements." International Journal of Thermal Sciences 49, no. 12 (December 2010): 2385–90. http://dx.doi.org/10.1016/j.ijthermalsci.2010.08.004.

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