A comparison of nanofluid thermal conductivity measurements by flash and hot disk techniques

32nd UIT (Italian Union of Thermo–fluid-dynamics) Heat Transfer Conference

物理学;力学

Buonomo, Bernardo^1 ; Colla, Laura^2 ; Fedele, Laura^2 ; Manca, Oronzio^1 ; Marinelli, Lorenzo^1

Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università Degli Studi di Napoli, Via Roma 29, Aversa (CE)

81031, Italy^1

Consiglio Nazionale Delle Ricerche, Istituto per le Tecnologie della Costruzione, Corso Stati Uniti 4, Padova

35127, Italy^2

关键词: Conductivity of fluids;    Enhanced conductivity;    Heat transfer efficiency;    Hot disk technique;    Measurement techniques;    Thermal conductivity measurements;    Thermal measurements;    Volumetric concentrations;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/547/1/012046/pdf
DOI  :  10.1088/1742-6596/547/1/012046

学科分类：力学，机械学

来源: IOP

【 摘 要 】

The conversion into nanofluids is considered a suitable solution to increase the heat transfer efficiency of such fluids. Several theories with an emphasis on different thermal nanofluid mechanisms have appeared to predict enhanced conductivity measurements. There are many ways to measure the thermal conductivity of fluids. Some researchers argued that the anomalous k enhancement data are caused by inaccuracies of thermal measurement methods. In this paper, measurements on thermal conductivities of nanofluid mixtures (alumina/water) by means of two different methods are accomplished, i.e. the flash and the hot disk technique. In the first method, a NETZSCH model LFA 447 NanoFlash is employed, while in the second one a Hot Disk model TPS 2500 S is used. A comparison between the results obtained from the different measurement techniques is done. Two-step method is used to prepare nanofluids with a nanoparticles volumetric concentration from 0.1% to 4%. Each mixture, at assigned volumetric concentration, is treated with a sonicator for different times and thermal conductivity is measured in the range of temperature from 20°C to 50°C. Moreover, for assigned volumetric concentration and sonication, the stability analysis is performed and thermal conductivity measurements are carried out to determine the effect of sonication time. Results show the thermal conductivity dependence on sonication time, and an asymptotic value is evaluated for each volumetric concentration.