共查询到20条相似文献,搜索用时 15 毫秒
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Experimental shell-side heat transfer and pressure drop in gas flow for spiral-wound LNG heat exchanger 总被引:1,自引:0,他引:1
Bengt O. Neeraas Arne O. Fredheim 《International Journal of Heat and Mass Transfer》2004,47(2):353-361
A test plant has been constructed for measurements of local heat-transfer coefficients and frictional pressure drops on the shell side of spiral-wound LNG heat exchangers. Measurements have been performed with gas flow, liquid film flow and two-phase shear flow. This paper focuses on the measurements and the results from the gas flow measurements. 221 gas flow heat-transfer measurements and 80 gas flow frictional pressure drop measurements have been performed at a Re-number range of 5000-170 000 with nitrogen, methane, ethane and methane/ethane mixture as test fluids. 相似文献
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Unal Akdag A. Feridun Ozguc 《International Journal of Heat and Mass Transfer》2009,52(11-12):2667-2672
Heat transfer from a surface having constant heat flux subjected to oscillating flow in a vertical annular liquid column is investigated experimentally. The oscillation of water column in annuli is created using a piston cylinder mechanism. The experiments are carried out for four different oscillation frequencies, three amplitudes and three heat fluxes while the other parameters remain constant. The cycle-averaged values are considered in the calculation of heat transfer using the control volume approximation. Based on the experimental data, an empirical equation is obtained for the cycle averaged Nusselt number as a function of kinetic Reynolds number and dimensionless amplitude. 相似文献
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M. Mehrabi S.M. PesteeiT. Pashaee G. 《International Communications in Heat and Mass Transfer》2011,38(4):525-532
In this paper an Adaptive Neuro-Fuzzy Inference System (ANFIS) is used for modeling the effect of important parameters on heat transfer and fluid flow characteristics of helicoidal double-pipe heat exchangers using some numerically investigated and compared with those to experimental results for training and test data. In this way, overall heat transfer coefficient (Uo) and inner and annular pressure drop (ΔPin, ΔPan) are modeled with respect to the variation of inner and annular dean number (Dein, Dean), inner and annular Prandtl number (Prin, Pran) and pitch of coil (B) which are defined as input (design) variables. Then, we divided these data into train and test sections in order to accomplish modeling. We instructed ANFIS network by 75% of numerical-validated data. Twenty-five percent of primary data which had been considered for testing the appropriateness of the models was entered into ANFIS network models and results were compared by two statistical criterions (R2, RMSE). Considering the results, it is obvious that our proposed modeling by ANFIS is efficient and valid and it can be expanded for more general states. 相似文献
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Experimental investigation into convective heat transfer of nanofluids at the entrance region under laminar flow conditions 总被引:2,自引:0,他引:2
Dongsheng Wen 《International Journal of Heat and Mass Transfer》2004,47(24):5181-5188
This paper reports an experimental work on the convective heat transfer of nanofluids, made of γ-Al2O3 nanoparticles and de-ionized water, flowing through a copper tube in the laminar flow regime. The results showed considerable enhancement of convective heat transfer using the nanofluids. The enhancement was particularly significant in the entrance region, and was much higher than that solely due to the enhancement on thermal conduction. It was also shown that the classical Shah equation failed to predict the heat transfer behaviour of nanofluids. Possible reasons for the enhancement were discussed. Migration of nanoparticles, and the resulting disturbance of the boundary layer were proposed to be the main reasons. 相似文献
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为了获得翅片间距Pf对平直翅片管换热器的传热与阻力特性的影响规律,根据相似模化原理对3种不同Pf的平直翅片管换热器进行了试验研究。结果表明:雷诺数Rea在4 000~8 000范围内,努赛尔数Nua数随Rea的增大而增加,欧拉数Eua随Rea的增大而降低;同一Rea下,Nua随Pf减小而增加,但增加不明显,Eua随Pf增大而降低;同一Rea下,Pf越大,综合流动传热性能越好,但实际换热面积会减小,需综合考虑。研究成果可为汽轮发电机平直翅片管换热器的结构和性能优化提供依据。 相似文献
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This communication documents the experimental investigation of the theoretical model for predicting the thermal performance of parallel flow microchannel heat exchangers subjected to external heat flux. The thermal model investigated in this communication is that previously developed by the authors of this communication; Mathew and Hegab [B. Mathew, H. Hegab, Application of effectiveness-NTU relationship to parallel flowmicrochannel heat exchangers subjected to external heat transfer, International Journal of Thermal Sciences 31 (2010) 76–85]. The validity of the theoretical model with respect to microchannel profile, hydraulic diameter, heat capacity ratio and degree of external heat transfer is checked. The microchannel profiles investigated are trapezoidal and triangular with hydraulic diameter of 278.5 and 279.5 μm, respectively. The influence of hydraulic diameter is analyzed using trapezoidal microchannels with hydraulic diameters of 231 and 278.5 μm. Experiments are conducted for heat capacity ratios of unity and 0.5 using the heat exchanger employing the trapezoidal microchannel with hydraulic diameter of 278.5 μm for purposes of validating the model. Experiments are done for all heat exchangers for two different levels of external heat transfer; 15% and 30% of the maximum possible heat transfer. Irrespective of the parameter that is investigated the experimental data are found to perfectly match with the theoretical predictions thereby validating the thermal model investigated in this communication. 相似文献
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《International Communications in Heat and Mass Transfer》2006,33(4):529-535
In the present investigation nanofluids containing CuO and Al2O3 oxide nanoparticles in water as base fluid in different concentrations produced and the laminar flow convective heat transfer through circular tube with constant wall temperature boundary condition were examined. The experimental results emphasize that the single phase correlation with nanofluids properties (Homogeneous Model) is not able to predict heat transfer coefficient enhancement of nanofluids. The comparison between experimental results obtained for CuO / water and Al2O3 / water nanofluids indicates that heat transfer coefficient ratios for nanofluid to homogeneous model in low concentration are close to each other but by increasing the volume fraction, higher heat transfer enhancement for Al2O3 / water can be observed. 相似文献
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Srbislav B. Genić Branislav M. Jaćimović Marko S. Jarić Nikola J. Budimir Mirko M. Dobrnjac 《International Journal of Heat and Mass Transfer》2012,55(15-16):4295-4300
This paper presents the results of experimental research on shell-side heat transfer coefficient concerning 3 heat exchangers with helical coils. Measurements were carried in laboratory and the following correlation was found to be adequate Nu = 0.50 ? Re0.55 ? Pr 1/3 ? (η/ηw)0.14 where Re and Nu are based on shell-side hydraulic diameter. 相似文献
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Heat transfer augmentation in heat exchangers has been a key research topic in recent times. Over the years, many methods have been proposed for heat transfer enhancement, such as providing fins, changing the cross-sectional area of tubes, vortex generator, twisted tape inserts, and so forth. In addition to the above-mentioned techniques, corrugation of tubes was also proposed by a few authors who demonstrated that this method could effectively increase the heat transfer rate. To address the same in this study, the different corrugation profiles have been created with the help of CATIA software for the study. The simulations were performed using ANSYS R19.2. The results so obtained were used to calculate the various thermal and hydraulic perfoallrmance parameters of the heat exchanger with the help of macros created in MS Excel. The result shows that the use of corrugation on the inner tube of the heat exchanger increased the heat transfer coefficient, fanning friction factor, and rate of cooling by 5%–21%, 90%–355%, and 25.67%–157.40%, respectively, in case of the plain double-pipe heat exchanger for the mass flow rate variation of 5–25 kg/min. It is also observed that the smooth tube has more thermohydraulic performance as 1.2152. 相似文献
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Heat transfer and pressure drop characteristics are investigated here using experimental and analytical techniques for a dimple plate heat exchanger. The analysis uses the log mean temperature difference method (LMTD) in all its calculations. Whilest the shell side flow highly resembles the flow over a rough or wavy plate, the tube side passage in these represents the flow over short hexagonal tube banks with the flowing across the sectional areas between the hexagons having the shape of a benzene ring. Local and global experimental measurements are carried out around the heat exchanger. Furthermore, analytical models for both sides of the heat exchanger were obtained from the literature. Reasonable cross match between experimental and analytical results could be obtained. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Three-dimensional simulations of four louver-tube junction geometries are performed to investigate the effect on louver and tube friction and heat transfer characteristics. Three Reynolds numbers, 300, 600 and 1100, based on bulk velocity and louver pitch are calculated. Strong three-dimensionality exists in the flow structure in the region where the angled louver transitions to a flat landing adjoining the tube surface, whereas the flow on the angled louver far from the tube surface is nominally two-dimensional. Due to the small spatial extent of the transition region, its overall impact on louver heat transfer is limited, but the strong unsteady flow acceleration on the top louver surface augments the heat transfer coefficient on the tube surface by over 100%. In spite of the augmentation, the presence of the tube lowers the overall Nusselt number of the heat exchanger between 25% and 30%. Comparisons with correlations derived from experiments on full heat exchanger cores show that computational modeling of a small subsystem can be used reliably to extract performance data for the full heat exchanger. 相似文献
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N. García-Hernando A. Acosta-Iborra U. Ruiz-Rivas M. Izquierdo 《International Journal of Heat and Mass Transfer》2009,52(23-24):5433-5446
This work presents an experimental analysis of the hydrodynamic and thermal performance of micro-heat exchangers. Two micro-heat exchangers, characterized by microchannels of 100 × 100 and 200 × 200 μm square cross-sections, were designed for that purpose. The fluid used was deionized water and there was no phase change along the fluid circuit. The fluid pressure drop along the heat exchanger and the heat transfer were measured and corrections were made to isolate the contribution of the microchannels. The results were compared with the predictions of the classical viscous flow and heat transfer theory. The main conclusions show that the experimental results fit well with these theories. No effects of heat transfer enhancement or pressure drop increase were observed as a consequence of the small scale of the microchannels. 相似文献
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《International Journal of Heat and Mass Transfer》1987,30(8):1663-1672
The wall-particles heat transfer coefficient has been measured in small-scale rotary drum heat exchangers. Experiments have been conducted with nine granular materials of different nature, with particle diameters ranging from 194 μm to 4mm. The effects of rotational speed (1–40 rev min−1), filling degree (4–17%) and drum diameter (0.25 and 0.485 m) have been investigated. The experimental data have been correlated by a semi-empirical relationship, that includes a contact resistance at the wall, the heat capacity of the particles immediately adjacent to the wall and the heat penetration resistance of the bulk of the particle bed. The contact resistance is shown to be due to the roughness of the particles. A mean roughness height of 12 μm provides a good fit to the measured coefficients. 相似文献
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L. Perez B. Ladevie P. Tochon J.C. Batsale 《International Journal of Heat and Mass Transfer》2009,52(1-2):407-414
The present probe is developed in order to accurately estimate in situ not only the convective exchange coefficient but also the fouling thickness of heat exchangers from a reliable transient state estimation method.The originality of the estimation method consists in considering a global response time of the system in fouling conditions to be compared to clean conditions. The sensitivity function is then built from the experimental signal without precise knowledge about the model or the absolute thermophysical properties. The reliability of the method is demonstrated in theoretical cases and with calibrated experiments. 相似文献