Frontiers in Heat and Mass Transfer (FHMT), 17, 21 (2021) DOI: 10.5098/hmt.17.21 Global Digital Central ISSN: 2151-8629 1 SIMULATION AND INVESTIGATION OF NANO-REFRIGERANT FLUID CHARACTERISTICS WITH THE TWO-PHASE FLOW IN MICROCHANNEL Ammar Hassan Soheel, Omar Mahmood Jumaah, Ahmed Mustaffa Saleem * Technical Engineering College, Northern Technical University, Mosul, 41001, Iraq ABSTRACT This paper presents a simulation and investigation of the heat transfer coefficient, pressure drop, and thermal conductivity of two - phase flow. The simulation was performed of mixtures (Al2O3 nanoparticles with R134a refrigerant). The size of nanoparticles (Al2O3) which is used in this study is 30 nm and volume concentrations are 0.015 and 0.03. The two – phase flowing through a horizontal circular microchannel of (diameter 100 µm, and length 20 mm) under constant heat flux (3000 W/m 2 ) and constant wall temperature (330 K), also in this study used the inlet temperature at -20 o C and mass flow rates are 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 g/s using in the dissipation of heat from electronic circuits by evaporation. The simulation is achieved by CFD numerical model using FLUENT ANSYS version 15 software. The results indicate the best temperature, pressure drop, density and volume fraction for two-phase flow nanorefrigerant in the microchannel. The higher heat transfer coefficient and pressure drop of two-phase nanorefrigerant flow at a high volume concentration (0.03) of Al2O3 when the mass flow rate is maximum. Finally, compared heat transfer coefficient of this study with the results of Kumar et al. (2013) at variation the mass flow rate, and found the root mean square of error (10%), also compared heat transfer coefficient of this study with results of Hernández et al. (2016) at variable volume concentration of nanoparticles Al2O3, and found the root mean square of error (3.7%). Keywords: Nanorefrigerant, Tow-phase microchannel, R134a, Al2O3 nanoparticles, Heat transfer Coefficient. 1. INTRODUCTION For engineers who work over decades to develop better heat transfer in various applications, nano-fluid has become an interesting topic. A Nanofluid is a new type of heat transfer fluid that operates in conventional host fluids with nanoparticles, enhances the surface contact area, nano- refrigerants are nanofluids and host fluids are coolant. The potential of R134a to deplete global warming (GMP) and ozone (ODP) is lower than that of other coolants Singh et al. (2015). Al2O3 nanoparticles have the highest use in the cooling system, because they are not costly, easier to disperse and are not healthy and efficient in host refrigerants Patil et al. (2015). There has been more and more research in recent years on the two-phase flows of heat and fluid dynamics in microchannels. It is common knowledge that a higher heat transfer factor can be obtained at some mass velocity by reducing hydraulic diameter at the expense of greater frictional pressure drop, based on macro-scale convective heat transfer within the channels. Microchannels, for instance heat pipes, electronics and automotive condensers, are used in many different applications Cavallini et al. (2005). The system assumes complex fluid behaviors when two phases are confined into a microchannel. The predominance of surface forces (surface tension etc.) causes the two-phase flow of gas fluid in the microchannels to compare itself with conventionally large-sized tubes (>10 mm) Yue et al. (2004) as the channel diameter decreases. The temperature of an electronic device increases fairly consistently with increasing heat flow for a certain thermal resistance sink and ambient temperature. For defense electronics, this relationship is particularly problematic Lee et al. (2009). * Corresponding author. Email: ahmedmustafa@ntu.edu.iq The two phase heat sinks of the microchannel are not without inconvenience. The small hydraulic diameter is likely to result in a significant drop in the pressure and a corresponding increase in the consumption of electronic systems, which is unwanted. For microchannel heat sink design, a strong understanding of the relationship between pressure drop and flux and heat flux is crucial Lee at al. (2005). Qu et al. (2003) dedicated to the measurement and prediction in water- cooled rectangular thermal dish heating of a saturated flow boiling thermal transfer coefficient. The model predictions and heat transmission coefficients over wide ranges of flux and heat flow were well agreed. Lee et al. (2004) investigated experimentally the two-phase pressure drop and the boiling coefficient of heat transfer R14a through the rectangular heat sink used to evaporate the cooling cycle. The study showed a general increase in the total pressure drop as mass speed and heat flux increase. And for both R134a and water it offers excellent predictions when a new coefficient of the heat transfer correlation was recommended. Cavallini et al. (2005) studied experimentally the lower pressure properties of R236ea, R134a and R410A multiport mini-channel, adiabatic two-phase flow. The experimental findings indicate that the correlations provided can reasonably well forecast the gradient of R134a friction. However, R236ea and even worse data for R410A were not satisfactorily agreed. Fukagata et al. (2007) performed a two-phase air and water simulation in the microtube. They focused on the characteristics of flow and heat transfer in bladder train flow. Because the local temperature differences were slight, the Nusselt number was huge beneath the bubble and the heat transfer was also increased by the liquid tension because of the circulating stream. Yang et al. (2008) investigated the boiling of R141B flow in a horizontal rolling tube. It had been discovered that a significant impact of the phase distribution on the two-phase temperature profile and Frontiers in Heat and Mass Transfer Available at www.ThermalFluidsCentral.org