Boiling heat transfer characteristics of nanofluids in a flat heat pipe evaporator with micro-grooved heating surface

Liu, Zhenhua; Xiong, Juntao; Bao, Ran

doi:10.1016/j.ijmultiphaseflow.2007.06.009

Cited by 193 publications

(85 citation statements)

References 15 publications

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“…14) When jet impingement of a coolant takes place on a heated plate, the following cooling zones can be distinguished as a function of increasing distance from the central spot of impingement 15,16) : i) single phased forced convection, ii) nucleate transition boiling, iii) forced convection film boiling, iv) agglomerated pools and v) radiation and conduction. Zone i) been described by researchers as the area defined by a circle of 1.6-2.6 times the diameter of the jet (which is approx.…”

Section: Resultsmentioning

confidence: 99%

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Application of Water Based-TiO2 Nano-fluid for Cooling of Hot Steel Plate

Chakraborty

Das

et al. 2010

ISIJ Int.

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A nano-fluid was prepared by dispersing 0.1 wt% TiO 2 nano particles in water along with a small amount of surfactant. The performance of the nano-fluid vis-a-vis water as coolant was studied on hot steel plates by measuring the cooling curves and by appropriate metallographic investigations. Significant enhancement in cooling rate was observed for the nano-fluid which could be due to an enhancement of convective heat transfer by jet impingement, coupled with lower surface tension of the nano-fluid, as compared to water.KEY WORDS: TiO 2 nano-fluid; continuous cooling transformation diagram; micro-alloyed steel. 0.14, Al: 0.04, Si: 0.01, S: 0.005, P: 0.013, Ti: 0.029, Nb: 0.004, N: 0.0035 was placed on the sample loading base of the specially constructed experimental set-up as shown in Fig. 2. The nano-fluid was pumped from the tank through a nozzle having a diameter of 6 cm and allowed to fall at a velocity 12.6 m/s on the preheated steel plate. A centrifugal pump with a flow rate of 400 L/h and head of 10 m operated at 230 V (drive: 0.025 kW) was used. A total of nine thermocouples were placed on the surface of the plate where the nano-fluid was incident. The cooling curve of the nanofluid was obtained by plotting the average temperature from the data recorded by all the nine thermocouples versus time. The experiment was repeated by allowing a jet of water on to an equivalent steel plate under the same experimental conditions, and cooling curve of water was plotted in the same manner. A field emission gun scanning electron microscope (FEG SEM), ZEISS, SUPRA 25, Germany operated at 20 kV with EDS attachment was used to study the microstructures taken from the top impinged surfaces as well as from the cross-sections of the plates, cooled by both water and the nano-fluid. An energy dispersive spectroscopic (EDS) analysis was also carried out on the top surface of the plate on which the nano-fluid was incident. Results and DiscussionFrom Fig. 1 it can be seen that the average size of the asreceived nano particles was in the range of 30 to 50 nm. Figure 3(a) compares the temperature-time plots of the steel plate cooled by water and by water based TiO 2 nanofluid. In the same diagram the temperature time transformation diagram (TTT) and continuous cooling transformation (CCT) plots for the steel composition 4) have been superimposed. The TTT and CCT curves denote 50 % phase transformation.From Fig. 3(a) it is clearly visible that the cooling rate for the water based TiO 2 nano-fluid is much faster than that of water till the bainite start temperature is reached. This difference in the cooling rates produces very distinct changes in the microstructures of the steel plate after cooling by water and by the nano-fluid as shown in Figs. 4(a)-4(e).To begin with, the hot plate right at the onset of cooling will be in the austenite range and phase transformation will occur as cooling progresses. Clearly, polygonal ferrite grains are observed on the top surface of the steel plate where water was incident. By contrast, the sur...

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Section: Resultsmentioning

confidence: 99%

“…17) Again, The boiling heat transfer coefficient and the critical heat flux(CHF) of stable nano-fluids has been shown to increase with the increase in the value of nanoparticles, up to a concentration of 1-1.25 wt%. 14,18) …”

Section: Resultsmentioning

confidence: 99%

Application of Water Based-TiO2 Nano-fluid for Cooling of Hot Steel Plate

Chakraborty

Das

et al. 2010

ISIJ Int.

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“…The working fluid properties, such as the thermal conductivity and surface tension; the heat transfer surface properties, such as the material, wettability, orientation, and surface roughness and finally the system properties, such as system pressure and the fluid surface interaction have significant influence on two phase heat transfer mechanism [29]. Many experimental studies are performed to identify NF effect on two phase heat transfer and they indicate that NFs can enhance or deteriorate heat transfer performance [30][31][32][33]. But, it is observed in nearly every study that a complex nano/micro porous layer of the nanoparticles forms on the surface of heated surface [32][33][34][35][36][37].…”

Section: Resultsmentioning

confidence: 99%

“…The presence of this porous layer and its characteristics has an important impact on evaporation/boiling heat transfer through changes in heated surface properties. It is reported that the presence of this layer alters the surface wettability and roughness and number of nucleation site present on the surface [29][30][31][32][33][34][35][36][37]. The reduction in evaporator wall temperature for decreasing heat flux at heat pipe with 5 wt.% of NF compared with other cases may be attributed to the effect of NFs on vapor bubble formation by bombarding the vapor bubbles by nanoparticles during their formation [38], the increase of active nucleation site density and bubble departure frequency [28,[39][40][41].…”

Section: Resultsmentioning

confidence: 99%

“…During recent years, nanofluids (NFs) have been suggested as working fluids to enhance heat pipes thermal performance. Various types of NFs with different concentrations, particle sizes and shapes have been used and interesting results on thermal performance enhancement are achieved [1][2][3][4][5][6][7][8][9]. Liu and Zhu [10] studied effects of aqueous CuO NFs on thermal performance of a horizontal mesh heat pipe experimentally.…”

Section: Introductionmentioning

confidence: 99%

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Thermal performance of screen mesh heat pipe with Al2O3 nanofluid

Ghanbarpour

Nikkam

Khodabandeh

et al. 2015

Experimental Thermal and Fluid Science

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a b s t r a c tThis study presents the effect of Al 2 O 3 nanofluid (NF) on thermal performance of screen mesh heat pipe in cooling applications. Three cylindrical copper heat pipes of 200 mm length and 6.35 mm outer diameter containing two layers of screen mesh were fabricated and tested with distilled water and water based Al 2 O 3 NF with mass concentrations of 5% and 10% as working fluids. To study the effect of NF on the heat pipes thermal performance, the heat input is increased and then decreased consecutively and the heat pipes surface temperatures are measured at steady state conditions. Results show that using 5 wt.% of Al 2 O 3 NF improves the thermal performance of the heat pipe for increasing and decreasing heat fluxes compared with distilled water, while utilizing 10 wt.% of Al 2 O 3 NF deteriorates the heat pipe thermal performance. For heat pipe with 5 wt.% Al 2 O 3 NF the reduction in thermal resistance of the heat pipe is found to be between 6% and 24% for increasing and between 20% and 55% for decreasing heat fluxes, while the thermal resistance increased between 187% and 206% for increasing and between 155% and 175% for decreasing steps in heat pipe with 10 wt.% of Al 2 O 3 NF.

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Experimental comparative study of heat pipe performance using CuO and TiO₂nanofluids

Manimaran

Palaniradja

Alagumurthi

et al. 2013

Int. J. Energy Res.

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SUMMARY In recent years, developing an energy efficient conventional heat pipe is more important because of the development of electronics and computer industries. To enhance the thermal performance of heat pipe, different nanofluids have been widely used. In this paper, an experimental investigation of heat transfer performance of heat pipe has been conducted using three different working fluids such as DI water, CuO nanofluid and TiO2 nanofluid. The heat pipe used in this study is made up of copper layered with two layers of screen mesh wick for better capillary action. The Parameters considered in this study are heat input, angle of inclination and evaporator fill ratio. The concentration of nanoparticle used in this study is of 1.0 wt.%. From the experimental results, comparisons of thermal performance were made between the heat pipes using various working fluids. Among various fill ratio charged, the heat pipe shows good thermal performance when it is operated at 75% fill ratio for all working fluids. However, the heat pipe operated with CuO nanofluid showed higher results compared with TiO2 nanofluid and DI water. Copyright © 2013 John Wiley & Sons, Ltd.

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Boiling heat transfer characteristics of nanofluids in a flat heat pipe evaporator with micro-grooved heating surface

Cited by 193 publications

References 15 publications

Application of Water Based-TiO2 Nano-fluid for Cooling of Hot Steel Plate

Application of Water Based-TiO2 Nano-fluid for Cooling of Hot Steel Plate

Thermal performance of screen mesh heat pipe with Al2O3 nanofluid

Experimental comparative study of heat pipe performance using CuO and TiO₂nanofluids

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Boiling heat transfer characteristics of nanofluids in a flat heat pipe evaporator with micro-grooved heating surface

Cited by 193 publications

References 15 publications

Application of Water Based-TiO2 Nano-fluid for Cooling of Hot Steel Plate

Application of Water Based-TiO2 Nano-fluid for Cooling of Hot Steel Plate

Thermal performance of screen mesh heat pipe with Al2O3 nanofluid

Experimental comparative study of heat pipe performance using CuO and TiO2nanofluids

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Product

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Experimental comparative study of heat pipe performance using CuO and TiO₂nanofluids