• Energy Research

Identifying optimal pin-fin configurations is essential to analyze the full potential of utilizing nanofluids in pin-fin heat sinks for electronics cooling applications. Therefore, the present study aimed to investigate the entropy generation and hydrothermal characteristics of water-based MWCNT (Multiwalled carbon nanotubes) and MWCNT/GNP (Multiwalled carbon nanotubes/graphene nanoplatelets) nanofluids in a heat sink equipped with fins of different configurations. The forced convection of the nanofluid was simulated through the multiphase Eulerian-Lagrangian model (discrete-phase model) by including the influence of slip mechanisms (Brownian motion, thermophoresis, Saffman lift and drag forces, pressure forces, virtual mass, and gravity) and the interphase nanolayering effect. Results showed that the performance of the MWCNT and MWCNT/GNP nanofluids was the highest in the triangular pin-fin heat sink, followed by rhombus and hydrofoil pin-fin heat sinks. The streamlined shape along with the large lateral and small stream-wise interspacing between the hydrofoil and rhombus fins hindered the effective coolant distribution across the heat sinks, thereby deteriorating their heat-dissipation capacity. However, the performance evaluation criteria results of the rhombus pin-fin heat sink outperformed the other pin-fin configurations due to the lower pressure drop.

This paper presents the modelling of heat and moisture transfer in a clothes-conditioning unit with the aim of improving the moisture content distribution to the clothes. A multicomponent, non-reacting, two-phase Eulerian–Eulerian model was utilised to solve the computational model. The clothes inside the conditioning unit were modeled as retangular towels (porous medium) of uniform thickness. Mass flow distribution of air and steam through the clothes was studied by systematically varying the steam nozzle angle (30° to 75°) and air inflow grill angle (45° to 105°). The simulation results were studied to identify the impact of design parameters on the mass flow distribution inside the clothes-conditioning unit. The mass flow of steam and the air–steam mixture were calculated through each towel in the forward and reverse direction. Response surface analysis was conducted to correlate the total mass flow rate and steam mass flow rate through each towel with the design variables. Moreover, a multiobjective genetic algorithm was employed to optimise the mass flow through the clothes and ascertain the optimal design configuration. The geometric configuration with a steam nozzle angle of 45° and air grill angle of 105° resulted in optimal steam and mixture distribution.

Abstract The manuscript investigates aerodynamic performance of an airborne wind turbine with varying shell configurations in an effort to elaborate the influence of shell aerodynamics on the performance of the buoyant airborne wind turbine for operating conditions at an altitude of 400 m above the sea level. A systematic study has been conducted on the three airborne duct shapes based on the NACA-5415, NACA-9415 and NACA-5425 cambered aerofoils by considering NREL Phase IV rotor and constant airborne shell throat diameter of 4.02 m. Three dimensional steady state simulations have been performed by employing k-ω SST turbulence model for a range of wind speeds10–25 m/s at zero angle of attack (the angle between wind direction and turbine rotational axis). The performance of the studied turbines have been analysed in terms of rotor thrust coefficient, duct thrust coefficient, turbine power coefficient, swallowed mass flow rate and pressure distribution along the shell. Results demonstrate that among all the considered shell configurations, the NACA-9415 shell based turbine demonstrated highest power coefficient. Increment in the both, aerofoil camber (5–9% of chord length) and thickness (15–25% of the chord length) resulted in 2.05 and 1.45 times higher turbine power coefficient respectively in comparison to the reference aerofoil (NACA-5415) shell based turbine.

The air-side thermal-hydraulic performance of multi-louvered aluminium fin heat exchangers is investigated. A systematic numerical study has been performed to analyze the air-sde thermal hydraulic characteristics over a wide range of Reynolds number i.e., from 30 to 500. Air-side heat transfer coefficient and pressure drop were calculated and validated over the mentioned band of Reynolds numbers. The critical Reynolds number was determined numerically; and also the variation of flow pattern along with the air-side heat transfer coefficient and pressure drop in a multi-louvered heat exchanger associated with R e c r i has been reported. Moreover, a parametric study of the multi-louvered aluminium fin heat exchangers was also performed for 36 heat exchanger configurations with the louver angles (19–31°); fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm); and the geometric configuration exhibiting the highest air-side heat transfer coefficient was reported. The air-side heat transfer coefficient and pressure drop results for different geometrical configurations were presented in terms of Colburn j factor and Fanning friction factor f; as a function of Reynolds number based on louver pitch.

Abstract This manuscript is aimed at investigating the thermohydraulic characteristics of Al2O3 − Cu/water hybrid nanofluid in a micro pin-fin heat sink by implementing a multiphase Lagrangian–Eulerian approach. In modelling the nanofluid the influence of slip mechanisms i.e. Saffman lift and drag force, Brownian motion, gravity, virtual mass, thermophoresis and pressure gradient-induced force is included. In addition, the fin efficiency of the nanofluid cooled sharp and streamlined fin configurations is probed by analysing diamond, circular and elliptical fins arranged in the staggered assembly. Spherical shaped hybrid nanoparticles of 15 nm are studied for the particle volume fraction of 1%. The performance of heat sinks is evaluated by analysing the quantitative parameters including log mean temperature difference, average (Nuavg) and surface (Nus) Nusselt number. Besides, the flow streamlines, thermal and vorticity contours represent the qualitative depiction of flow and thermal distributions. Results demonstrate that utilising nanofluid optimises Nuavg enhancement to maximum values of 25.14%, 19.65% and 24% for diamond, circular and elliptical fins, respectively. The thermal efficiency of nanofluid is highest across the upstream fins and it diminishes towards the downstream fins. At the highest pressure drop, the fin efficiency of the studied fin configurations is in the order of circular, elliptical and diamond fins.