Numerical and Experimental Investigation Into the ...

Cong Qi School of Electric Power Engineering, China University of Mining and Technology, Xuzhou 221116, China e-mail: [email protected]

Yongliang Wan School of Electric Power Engineering, China University of Mining and Technology, Xuzhou 221116, China e-mail: [email protected]

Lin Liang School of Electric Power Engineering, China University of Mining and Technology, Xuzhou 221116, China e-mail: [email protected]

Zhonghao Rao School of Electric Power Engineering, China University of Mining and Technology, Xuzhou 221116, China e-mail: [email protected]

Yimin Li1 School of Electric Power Engineering, China University of Mining and Technology, Xuzhou 221116, China e-mail: [email protected]

Numerical and Experimental Investigation Into the Effects of Nanoparticle Mass Fraction and Bubble Size on Boiling Heat Transfer of TiO2–Water Nanofluid Considering mass transfer and energy transfer between liquid phase and vapor phase, a mixture model for boiling heat transfer of nanofluid is established. In addition, an experimental installation of boiling heat transfer is built. The boiling heat transfer of TiO2– water nanofluid is investigated by numerical and experimental methods, respectively. Thermal conductivity, viscosity, and boiling bubble size of TiO2–water nanofluid are experimentally investigated, and the effects of different nanoparticle mass fractions, bubble sizes and superheat on boiling heat transfer are also discussed. It is found that the boiling bubble size in TiO2–water nanofluid is only one-third of that in de-ionized water. It is also found that there is a critical nanoparticle mass fraction (wt.% ¼ 2%) between enhancement and degradation for TiO2–water nanofluid. Compared with water, nanofluid enhances the boiling heat transfer coefficient by 77.7% when the nanoparticle mass fraction is lower than 2%, while it reduces the boiling heat transfer by 30.3% when the nanoparticle mass fraction is higher than 2%. The boiling heat transfer coefficients increase with the superheat for water and nanofluid. A mathematic correlation between heat flux and superheat is obtained in this paper. [DOI: 10.1115/1.4033353] Keywords: nanofluid, boiling bubble, boiling heat transfer, nanoparticle mass fraction

1

Introduction

Boiling heat transfer is an important heat transfer process in many heat transfer equipment. Many researchers have investigated the boiling heat transfer of pure water by numerical and experimental methods [1–9], respectively. Due to less and less energy in the world, it is necessary for us to produce new mediums with high heat transfer performance. A new stable fluid, nanofluid, was firstly produced by adding metal (or metallic oxide) nanoparticles into water in 1995. Compared with common fluid, nanofluid has many merits. Firstly, nanofluid has a higher heat transfer coefficient [10]. Secondly, Brownian movement between nanoparticles can disturb the laminar boundary layer and can enhance the heat transfer [11]. Lastly, it is easy for us to produce stable nanofluid, because the flow behaviors of nanoparticles like a pure fluid [12]. Nanofluid is widely applied in the field of boiling heat transfer. Boiling heat transfer of nanofluid is investigated by many researchers. However, different conclusions are obtained. Compared with water, some studies have shown enhancement, some studies have shown degradation, and some studies have shown little changes. Table 1 shows the boiling heat transfer enhancement of nanofluid. From Table 1, it can be seen that some studies have shown enhancement. Liu et al. [13] experimentally investigated the boiling heat transfer of CuO–water nanofluid in a miniature flat heat pipe with microgrooves, and found that the boiling heat 1 Corresponding author. Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 10, 2015; final manuscript received April 5, 2016; published online May 3, 2016. Assoc. Editor: Amy Fleischer.

Journal of Heat Transfer

transfer of CuO–water nanofluid with mass fraction wt.% ¼ 1% increased about 25%. Shi et al. [14] experimentally investigated the pool boiling heat transfer of Fe–water and Al2O3–water nanofluids at a horizontal plate surface, and found that Fe–water and Al2O3–water nanofluids enhanced the boiling heat transfer by 60% at best. Wen and Ding [15] carried out an experiment to investigate the boiling heat transfer of c-alumina–water nanofluid, and nanofluid with mass fraction wt.% ¼ 1.25% showed enhancement up to 40%. Qi et al. [16] experimentally investigated the boiling heat transfer of Al2O3–water nanofluid, and nanofluid with mass fraction wt.% ¼ 1% showed enhancement up to 28%. Truong [17] carried out a boiling heat transfer experiment heated by stainless steel wire, and the experimental results showed that Al2O3–water and SiO2–water nanofluids enhanced the boiling heat transfer by 68%. Ahn et al. [18] experimentally investigated the effect of nanostructured surface on pooling boiling heat transfer of MWCNTs-PF-5060 nanofluid, and found that the nanofluid enhanced the boiling heat transfer by 19–33%. Coursey and Kim [19] experimentally investigated the effect of surface wettability on the boiling heat transfer of Al2O3–water nanofluid and observed that nanofluid increased the boiling heat transfer by 37%. Chopkar et al. [20] built an experimental facility and studied the boiling heat transfer of ZrO2–water nanofluid, and the experimental results showed that ZrO2–water nanofluid increased the boiling heat transfer. Kathiravan et al. [21] found that the boiling heat transfer of carbon nanotubes–water nanofluid with volume fraction 0.25 vol% increased up to 1.75-fold. Soltani et al. [22] found that Al2O3–water nanofluid increased the boiling heat transfer by 30%. Kim et al. [23] investigated the boiling heat transfer of Al2O3– water, ZrO2–water, and SiO2–water nanofluids heated by stainless steel wire, and observed that nanofluid improved the boiling heat transfer.

C 2016 by ASME Copyright V

AUGUST 2016, Vol. 138 / 081503-1

Downloaded From: http://heattransfer.asmedigitalcollection.asme.org/ on 11/04/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use

Table 1 Boiling heat transfer enhancement of nanofluid Author Liu et al. [13] Shi et al. [14] Wen et al. [15] Qi. et al. [16] Truong [17] Ahn et al. [18] Coursey and Kim [19] Chopkar et al. [20] Kathiravan et al. [21] Soltani et al. [22] Kim et al. [23] Bang and Chang [24] Das et al. [25] Jackson [26] Milanova and Kumar [27] Zhou [28] Sajith et al. [29] Trisaksri and Wongwises [30] Kim et al. [31] Vassallo et al. [32] You et al. [33]

Nanofluid

Concentration (vol%)

CuO–water Fe–water and Al2O3–water c-Al2O3–water c-Al2O3–water Al2O3–water and SiO2–water MWCNTs-PF-5060 Al2O3–water ZrO2–water CNTs–water Al2O3–water Al2O3–water, ZrO2–water and SiO2–water Al2O3–Water Al2O3–water Au–water Al2O3–water, SiO2–water and CeO2–water Cu–acetone Al2O3–water and CuO–water TiO2–R141b Al2O3–water SiO2–water Al2O3–water

From Table 1, it can be seen that some studies have shown degradation. Bang and Chang [24] observed degradation in the boiling heat transfer for Al2O3–water nanofluid. Das et al. [25] experimentally investigated the boiling heat transfer of Al2O3– water nanofluid in a cartridge heater and found that the Al2O3– water nanofluid decreased the boiling heat transfer by 10–40%. Jackson [26] investigated the boiling heat transfer of Au–water nanofluid and the results showed deterioration in the boiling heat transfer. Milanova and Kumar [27] found that Al2O3–water, SiO2–water, and CeO2–water nanofluids decreased the boiling heat transfer. Zhou [28] investigated the boiling heat transfer of subcooled Cu–acetone nanofluid in a horizontal Cu tube and obtained the conclusion that the subcooled Cu–acetone nanofluid showed deterioration in the boiling heat transfer. Sajith et al. [29] experimentally investigated the boiling heat transfer of Al2O3– water and CuO–water nanofluids heated by NiCr wire and observed that the two kinds of nanofluids showed degradation in the boiling heat transfer. Trisaksri and Wongwises [30] experimentally investigated the nucleate pool boiling heat transfer on the outside of the horizontal tube submerged in TiO2–R141b nanofluid and found that the TiO2–R141b nanofluid decreased the boiling heat transfer. From Table 1, it can be also seen that some studies have shown few changes. Kim et al. [31] investigated the pool boiling heat transfer of Al2O3–water nanofluid and found that the boiling heat transfer of Al2O3–water nanofluid was almost the same with that of pure water. Vassallo et al. [32] investigated the pool boiling heat transfer of SiO2–water nanofluid and found that there were no appreciable differences in heat transfer between SiO2–water nanofluid and pure water. You et al. [33] investigated the boiling heat transfer of Al2O3–water nanofluid at the pressure of 2.89 psia and found that there were few changes in the boiling heat transfer between Al2O3–water nanofluid and pure water. The results of above published literatures are shown in Table 1. It can be seen from Table 1 that researchers obtained the conclusion that nanofluid showed degradation at high nanoparticle fractions (from vol% ¼ 1 to vol% ¼ 5), and obtained the conclusion that nanofluid showed enhancement at low nanoparticle fractions (less than vol% ¼ 0.5%). There are few researches on the problem whether there is a critical mass fraction between the enhancement and the degradation of boiling heat transfer. The innovations of this paper are as follows: (1) the paper revealed the effects of critical nanoparticle mass fraction on boiling heat transfer of nanofluid and studied the enhancement and the degradation of boiling heat transfer. (2) The paper revealed the effects of boiling bubble size 081503-2 / Vol. 138, AUGUST 2016

0.155