Experimental Investigation of Heat Transfer to Nanofluids

Author(s):  
Klaudia Chmiel-Kurowska ◽  
Grzegorz Dzido ◽  
Andrzej Gierczycki ◽  
Andrzej B. Jarze˛bski

Experimental investigations of convective heat transfer in nanofluid based on the Cu (approx. 0.15% and 0.25% vol.) nanoparticles synthesized in polyol process were conducted at constant heat flux conditions. A 30% increase in average heat transfer coefficient was found against the results obtained for a pure host liquid (ethylene glycol). Even more significant increase was in the entrance region.

2021 ◽  
Vol 2119 (1) ◽  
pp. 012171
Author(s):  
V V Cheverda ◽  
T G Gigola ◽  
P M Somwanshi

Abstract The spatiotemporal distribution of the temperature inside a constantan foil during impacting spray is resolved experimentally in the present work. The received infrared image sequence will be used to find the local and average heat transfer coefficient of the foil. In the future, the results obtained will be used to calculate the heat flux in the region of the contact line of each drop.


2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Avijit Bhunia ◽  
C. L. Chen

The necessity for an efficient thermal management system covering large areas is growing rapidly with the push toward more electric systems. A significant amount of research over the past 2 decades has conclusively proved the suitability of jet, droplet, or spray impingement for high heat flux cooling. However, all these research consider small heat source areas, typically about a few cm2. Can a large array of impingement pattern, covering a much wider area, achieve similar heat flux levels? This article presents liquid microjet array impingement cooling of a heat source that is about two orders of magnitude larger than studied in the previous works. Experiments are carried out with 441 jets of de-ionized water and a dielectric liquid HFE7200, each 200 μm diameter. The jets impinge on a 189 cm2 area surface, in free surface and confined jet configurations. The average heat transfer coefficient values of the present experiment are compared with correlations from the literature. While some correlations show excellent agreement, others deviate significantly. The ensuing discussion suggests that the post-impingement liquid dynamics, particularly the collision between the liquid fronts on the surface created from surrounding jets, is the most important criterion dictating the average heat transfer coefficient. Thus, similar thermal performance can be achieved, irrespective of the length scale, as long as the flow dynamics are similar. These results prove the scalability of the liquid microjet array impingement technique for cooling a few cm2 area to a few hundred cm2 area.


1969 ◽  
Vol 9 (04) ◽  
pp. 375-377 ◽  
Author(s):  
Antonio Romero-Juarez

Interest in temperature logs has been renewed recently. One of the main problems of temperature logs in injection wells is that of determining the zones that are taking fluids. A great step toward solving this problem has been reported in a recent paper. paper. The purpose of this paper is to point out another aim of temperature logging namely, that of relating the flow rate in water injection wells to some characteristics of the temperature logs. It has been stated that a factor of 6:1 gives approximate values in converting into B/D. The factor F, which has been found empirically, may be explained from theoretical considerations and because of this, it may be estimated more accurately. It has been shown that, for flow of a liquid ,............................(1) where .......................(2) a quantity that is different from zero. Eq. 1 can be written as ,..................................(3) which shows that, as is defined in Ref. 2, is identical to A. For injection down casing, the over-all heat transfer coefficient, U, may be considered infinite. Therefore, ...................................(4) Considering the wellbore as a linear point source, ....................(5) or, if ........................................(6) .......................(7) It has been observed that surprisingly good results are obtained by using the values k = 33.6 Btu/day-ft-F and a = 0.96 sq ft/day for different locations. Taking the values p = 350 lb/bbl, c = 1 Btu/lb-F, one obtains: ........................(8) It should be noted that the lower curve of Fig. 1 of Ref. 3 does not agree, for low values of t, with the solution .........................(9) corresponding to the constant heat flux line source and for this reason the graph should be used with caution. Eq. 8 has been plotted in Fig. 1 for three values of the external radius r'. It may be used to estimate the rate of water injection down casing from the shape of the injecting temperature log above the zone of entry of fluids. P. 375


Author(s):  
P. Razi ◽  
M. A. Akhavan-Behabadi

An experimental investigation has been carried out to study the heat transfer characteristics of CuO-Base oil nanofluid flow inside horizontal flattened tubes under constant heat flux. The nanofluid flowing inside the tube is heated by an electrical heating coil wrapped around it. The convective heat transfer coefficients of nanofluids are obtained for laminar fully developed flow inside round and flattened tubes. The effect of different parameters such as Reynolds number, flattened tube internal height, nanoparticles concentration and heat flux on heat transfer coefficient is studied. Observations show that the heat transfer performance is improved as the tube profile is flattened. The heat transfer coefficient is increased by using nanofluid instead of base fluid. Also, it can be concluded that decreasing the internal height of the flattened tubes and increasing the concentration of nanoparticles both contribute to the enhancement of heat transfer coefficient.


2018 ◽  
Vol 70 ◽  
pp. 02001
Author(s):  
Tadeusz Bohdal ◽  
Henryk Charun ◽  
Marcin Kruzel ◽  
Małgorzata Sikora

This article presents the results of experimental research of heat transfer coefficient in air cooled vertical pipe minichannels during R404A, R407C and R410A high-pressure refrigerants condensation. The study determined local and average heat transfer coefficient values in full range of vapour quality, x = 0 ÷ 1. On the basis of experimental investigations, the dependence of heat transfer on the vapour quality x, mass flux density G and minichannel's internal diameter dw was obtained.


2016 ◽  
Vol 33 (6) ◽  
pp. 1714-1728 ◽  
Author(s):  
Hsien-Hung Ting ◽  
Shuhn-Shyurng Hou

Purpose – The purpose of this paper is to numerically investigate the convective heat transfer of water-based CuO nanofluids flowing through a square cross-section duct under constant heat flux in the turbulent flow regime. Design/methodology/approach – The numerical simulation is carried out at various Peclet numbers and particle concentrations (0.1, 0.2, 0.5, and 0.8 vol%). The finite volume formulation is used with the semi-implicit method for pressure-linked equations algorithm to solve the discretized equations derived from the partial nonlinear differential equations of the mathematical model. Findings – The heat transfer coefficients and Nusselt numbers of CuO-water nanofluids increase with increases in the Peclet number as well as particle volume concentration. Also, enhancement of the heat transfer coefficient is much greater than that of the effective thermal conductivity at the same nanoparticle concentration. Research limitations/implications – Simulation of nanofluids turbulent forced convection at very high Reynolds number is worth for further study. Practical implications – The heat transfer rates through non-circular ducts are smaller than the circular tubes. Nevertheless, the pressure drop of the non-circular duct is less than that of the circular tube. This study clearly presents that the nanoparticles suspended in water enhance the convective heat transfer coefficient, despite low volume fraction between 0.1 and 0.8 percent. Adding nanoparticles to conventional fluids may enhance heat transfer performance through the non-circular ducts, leading to extensive practical applications in industries for the non-circular ducts. Originality/value – Few papers have numerically studied convective heat transfer properties of nanofluids through non-circular ducts. The present numerical results show a good agreement with the published experimental data.


2021 ◽  
Vol 2101 (1) ◽  
pp. 012037
Author(s):  
Junli Guo ◽  
Jin Zou ◽  
Changlin Yang ◽  
Deping Lu ◽  
Lefei Sun

Abstract The calculation of temperature field in the mold is important for the study of solidification process of liquid steel. In order to calculate the accurate temperature field of slab in the mod, the boundary condition of heat transfer in the mold should be determined before the calculation of slab temperature. In this paper, the relationship among the average heat transfer coefficient in the mold, the physical properties of steel, the cast condition and the cooling condition is derived according to the energy conservation equation and the Fourier law of heat conduction. Furthermore, the method for determining the parameters related to the formula of boundary heat flux is introduced. Results indicate that the average heat transfer coefficient in the mold ranges from 450 to 2000 W·(m2oC)−1 for conventional caster with a casting speed ranging from 0.8 and 1.8 m·min-1. The average heat transfer coefficient increases with the increase of casting speed. Besides, the casting speed has an effect on the parameters in the formula of calculating boundary heat flux, which indicates that the casting speed and the cooling condition should be taken into consideration for determining parameters related to the formula of calculating surface heat flux in the mold.


2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1323-1332
Author(s):  
Stanislaw Lopata ◽  
Pawel Oclon ◽  
Tomasz Stelmach ◽  
Pawel Markowski

Cross-flow heat exchangers with elliptical tubes are often used in industrial application. In comparison with round tubes, the elliptical tubes have a better aero-dynamic shape, which results in a lower pressure drop of working fluid flowing through the inter-tubular space of heat exchanger. Also, a higher heat flux is transferred from gas to the wall of such a tube due to the more intense heat exchange process. To prove this thesis, the values of the heat transfer coefficient from the wall of the elliptical pipe to the water flowing inside were determined, using the data from the conducted measurements. This study presents also research stand with a vertically positioned tube. In order to obtain a constant heat flux through the wall of elliptical tube, a resistance wire is used, evenly wound on the external surface of tube measuring section. The use of thermal insulation minimized heat loss to the environment to a negligible value. Installed K-type thermocouples allowed one to obtain, for various measurement conditions, the temperature distribution within the elliptical tube wall (for a given cross-section) and the water flowing inside it (in a given cross-section, at different depths, for both axes of the ellipse). The design of the stand allows such measurements in several locations along the length of the measurement section. The measurement results were used to verify numerical calculations. The relative error of the heat transfer coefficient value determined on the basis of CFD calculations using the SST-TR turbulence model in relation to the one determined on the basis of the measurement data is about 11%.


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