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IN THIS ISSUE

### Research Papers

J. Thermal Sci. Eng. Appl. 2019;11(4):041001-041001-11. doi:10.1115/1.4041877.

The oscillatory flows are often utilized in order to augment heat transfer rates in various industrial processes. It is also a well-known fact that nanofluids provide significant enhancement in heat transfer at certain conditions. In this research, heat transfer in an oscillatory pipe flow of both water and water–alumina nanofluid was studied experimentally under low frequency regime laminar flow conditions. The experimental apparatus consists of a capillary tube bundle connecting two reservoirs, which are placed at the top and the bottom ends of the capillary tube bundle. The upper reservoir is filled with the hot fluid while the lower reservoir and the capillary tube bundle are filled with the cold fluid. The oscillatory flow in the tube bundle is driven by the periodic vibrations of a surface mounted on the bottom end of the cold reservoir. The effects of the frequency and the maximum displacement amplitude of the vibrations on thermal convection were quantified based on the measured temperature and acceleration data. It is found that the instantaneous heat transfer rate between de-ionized (DI) water (or the nanofluid)-filled reservoirs is proportional to the exciter displacement. Significantly reduced maximum heat transfer rates and effective thermal diffusivities are obtained for larger capillary tubes. The nanofluid utilized oscillation control heat transport tubes achieve high heat transfer rates. However, heat transfer effectiveness of such systems is relatively lower compared to DI water filled tubes.

Commentary by Dr. Valentin Fuster
J. Thermal Sci. Eng. Appl. 2019;11(4):041002-041002-9. doi:10.1115/1.4042352.

The contribution of the current study is to investigate the mixed convection in an inclined nanofluid filled cavity saturated with a partially layered non-Darcy porous medium. Moreover, due to the advantage of the particle-based methods, we presented the improved version of an incompressible smoothed particle hydrodynamics (ISPH) method. The current ISPH method was improved in boundary conditions treatment using renormalization kernel function. In the current investigation, we assumed that the inclined cavity is filled with a Cu-water nanofluid. The upper half of the cavity is saturated with a non-Darcy porous medium. Here, one domain approach is used for coupling the nanofluid and the porous medium layer. The cooled top wall of the cavity is carrying a tangential unit velocity and the bottom wall is heated. The other two wall sides are adiabatic at zero velocity. Here, we investigated the effects of the Richardson parameter $Ri0.0001–100$, Darcy parameter Da $10−5–10−2$, an inclination angle $α0–90deg$ and a various solid volume fraction $ϕ0–0.05$ on the heat transfer of a Cu-water nanofluid. The obtained results showed that the average Nusselt number decreases as the Richardson number increases. An addition of 1–5% Cu nanoparticles slightly increased the overall heat transfer rate.

Commentary by Dr. Valentin Fuster
J. Thermal Sci. Eng. Appl. 2019;11(4):041003-041003-9. doi:10.1115/1.4041878.

Vegetable oil is considered as one among the promising alternatives for diesel fuel as it holds properties very close to diesel fuel. However, straight usage of vegetable oil in compression ignition (CI) engine resulted in inferior performance and emission behavior. This can be improved by modifying the straight vegetable oil into its esters, emulsion, and using them as a fuel in CI engine showcased an improved engine behavior. Waste cooking oil (WCO) is one such kind of vegetable oil gained a lot of attraction globally as it is generated in a large quantity locally. The present investigation aims at analyzing various parameters of single cylinder four stroke CI engine fueled with waste cooking oil biodiesel (WCOB), waste cooking oil biodiesel water emulsion (WCOBE) while the engine is operated with a constant speed of 1500 rpm. Furthermore, an attempt is made to study the impact of nanofluids in the behavior of the engine fueled with WCOB blended with nanofluids (WCOBN50). This work also explored a novel method of producing nanofluids using one-step chemical synthesis method. Copper oxide (CuO) nanofluids were prepared by the above mentioned method and blended with waste cooking oil biodiesel (WCOBN50) using ethylene glycol as a suitable emulsifier. Results revealed that brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) of WCOBN50 are significantly improved when compared to WCOB and WCOBE. Furthermore, a higher reduction in oxides of nitrogen (NOx), carbon monoxide (CO), hydrocarbon (HC), and smoke emissions were observed with WCOBN50 on comparison with all other tested fuels at different power outputs. It is also identified that one-step chemical synthesis method is a promising technique for preparing nanofluids with a high range of stability.

Commentary by Dr. Valentin Fuster

### Errata

J. Thermal Sci. Eng. Appl. 2019;11(4):047001-047001-1. doi:10.1115/1.4032332.

The first author’s affiliation and corresponding author should be listed as follows:

Topics: Exergy , Optimization , Wheels
Commentary by Dr. Valentin Fuster