Mohammad Layeghi

A numerical analysis of forced convective heat transfer from an elliptical pin fin heat sink with and without metal foam inserts is conducted using three-dimensional conjugate heat transfer model. The pin fin heat sink model consists of six elliptical pin rows with 3 mm major diameter, 2 mm minor diameter, and 20 mm height. The Darcy–Brinkman–Forchheimer and classical Navier–Stokes equations, together with corresponding energy equations are used in the numerical analysis of flow field and heat transfer in the heat sink with and without metal foam inserts, respectively. A finite volume code with point implicit Gauss–Seidel solver in conjunction with algebraic multigrid method is used to solve the governing equations. The code is validated by comparing the numerical results with available experimental results for a pin fin heat sink without porous metal foam insert. Different metallic foams with various porosities and permeabilities are used in the numerical analysis. The effects of air flow Reynolds number and metal foam porosity and permeability on the overall Nusselt number, pressure drop, and the efficiency of heat sink are investigated. The results indicate that structural properties of metal foam insert can significantly influence on both flow and heat transfer in a pin fin heat sink. The Nusselt number is shown to increase more than 400% in some cases with a decrease in porosity and an increase in Reynolds number. However, the pressure drop increases with decreasing permeability and increasing Reynolds number.

An experimental investigation was conducted in a six-cylinder, four-stroke diesel engine to establish the effects of Multi Wall Carbon Nano Tubes (MWCNT) with the dosing levels from 2.5 to 30 ppm with the waste vegetable oil (WVO) methyl esters fuel that was produced using the transestrification process, and subsequently, the WVO methyl ester was blended with diesel fuel in the proportion of 80% of diesel and 20% biodiesel by volume (B20). The Carbon nanotubes (with nano-structure (1/3) Chiral Metal and (2/3) semiconductor zigzag particles with the length of 10 m and diameter of 5 nm with purity rate of 95%) were blended with the biodiesel fuel. The CNTs were blended with the biodiesel with the aid of ultrasonicator. The whole investigation was conducted in the diesel engine using the following fuels: neat diesel fuel (D100), 20% biodiesel and 80% diesel by volume (B20), as well as B20 and CNT blended fuels accordingly. The experimental results revealed a considerable enhancement in the performance parameters for the CNT blended biodiesel fuels compared to the neat biodiesel and neat diesel fuel (power increased up to 17%, torque increased 18%, bsfc decreased 38.5%). Emission parameters for the CNT blended decreased compared to neat diesel and neat biodiesel fuels (HC decreased up to 22%, CO emission decreased 14%). CNT nano-additives are considered as a propitious fuel-borne catalyst to improve the fuel properties, owing to their enhanced surface area/volume ratio, quick evaporation and shorter ignition delay characteristics that help to improve the performance parameters of engine and decrease emissions.