A comprehensive review on double pipe heat exchangers

Advanced heat removal technologies are critical for high-performance automotive engines. The conventional fluids being used today are based on a mixture of distilled water (DW) and ethylene glycol (EG), which widens the operational temperature range but at the same time limits the heat removal. Therefore, the use of nanofluids for improving heat transfer performance has soared over the past few years. The problem is that most of the reports highlight the short-term heat transfer results which may not be true over time. In this paper, a suggested best practice for analyzing the usage of nanofluids in heat transfer applications is presented, specifically for an actual car radiator. This work investigates the use of aluminum oxide (Al2O3) and titanium dioxide (TiO2) nanoparticles dispersed in DW and EG at 50:50 volumetric proportions. The choice of these oxide-based nanofluids is motivated by their anti-corrosive properties that are usually not analyzed or discussed in most of the articles. Furthermore, the emphasis is given on the presentation of a comprehensive characterization of the nanofluids including thermophysical properties (size, density, viscosity, thermal conductivity, corrosive behavior) and long-term stability (zeta potential) which are essential for an end-user to have. The results showed a maximum enhancement of the thermal performance by 24.21% using Al2O3 at a volume fraction of 0.3%. Friction factor and performance evaluation criterion (PEC) for the radiator experiments are calculated in order to determine the penalty in the pressure drop and to evaluate it properly. Finally, it is found that the values of PEC lie in the range of 1.03–1.31 which indicates significant flow enhancement.

Enhancing the performance of automotive radiators using nanofluids

The problem of laminar forced convection flow of nanofluids has been thoroughly investigated for two particular geometrical configurations, namely a uniformly heated tube and a system of parallel, coaxial and heated disks. Numerical results, as obtained for water-γAl 2 O 3 and Ethylene Glycol-γAl 2 O 3 mixtures, have clearly shown that the inclusion of nanoparticles into the base fluids has produced a considerable augmentation of the heat transfer coefficient that clearly increases with an increase of the particle concentration. However, the presence of such particles has also induced drastic effects on the wall shear stress that increases appreciably with the particle loading. Among the mixtures studied, the Ethylene Glycol -γAl 2 O 3 nanofluid appears to offer a better heat transfer enhancement than water- γ/Al 2 O 3 ; it is also the one that has induced more pronounced adverse effects on the wall shear stress. For the case of tube flow, results have also shown that, in general, the heat transfer enhancement also increases considerably with an augmentation of the flow Reynolds number. Correlations have been provided for computing the Nusselt number for the nanofluids considered in terms of the Reynolds and the Prandtl numbers and this for both the thermal boundary conditions considered

Heat transfer enhancement by using nanofluids in forced convection flows

Single phase heat transfer and pressure drop analysis of a dimpled enhanced tube

A new heat transfer correlation for transition and turbulent fluid flow in tubes

Aerodynamic study of formula SAE car

Single phase flow heat transfer and pressure drop measurements in doubly enhanced tubes

Automotive radiators cool the engine coolant preventing heat seizure due to thermal expansion. Since both the coolant pump and radiator fan are parasitic devices (power has to be supplied by the engine), radiators with lower air-side and coolant pressure drop deploying coolants with superior thermo-physical characteristics that consume lower engine power need to be designed. Hence, augmented radiators with better overall heat transfer enhancement using improved tube-side and air-side geometries that emit fewer emissions, save energy and can be easily fabricated, tested and analysed are necessary. This review addresses this issue. Specially designed and fabricated air-side fins and flat extruded coolant tubes have significantly improved the thermal performance of engine cooling systems. This article reviews the state-of-the-art in experimental testing and computational modeling of enhanced radiators which can be deployed with high performance vehicles and their superiority over conventional radiators. Unlike other reviews which focused solely on coolant tube and air-side design and spacing, flow velocities and pressure drops, this article will also focus on the impact of nano-coolants on improving the thermal efficiency of radiators while summarizing the efficacy of aerodynamically efficient air-side fins like delta-winglets in reducing air-side pressure drop. This article aims to consolidate the available literature in the 21st century (experimental and analytical) for enhanced radiators equipped with unconventional coolants and aerodynamically designed air-side fins and should serve as a single reference for practicing engineers and graduate students.

Contemporary trends in thermo-hydraulic testing and modeling of automotive radiators deploying nano-coolants and aerodynamically efficient air-side fins

Bird strike, also known as avian ingestion, is the collision between a bird and an aircraft. Bird strikes have always been a cause of worry in the aeronautical industry: Aircraft both old and new have suffered from bird strikes. Jet engine ingestion occurs when the bird hits the jet engine of an aircraft and gets sucked in. Given that the fan blades rotate at a high rpm, bird strike on a fan blade causes its displacement into the adjacent blade. This leads to a cascading failure, wherein the entire system fails, thereby resulting in a lot of damage. In this article, we intend to investigate the construction of the fan blade and eventually strengthen its' resistance to bird strikes.

Bird strike analysis of jet engine fan blade

Ever-rising fuel costs necessitate design of fuel-efficient vehicles. Consequently, modern vehicle manufacturers are focused on designing low aerodynamic drag vehicles which would in-turn reduce the fuel consumption. This study analyses the contribution of external rear-view mirrors to the total drag force and the overall sound pressure level at the A, B and C pillars, while optimising the external rear-view mirror design accordingly. Solid Works renditions of external rear-view mirror models mounted on a reference luxury sedan were analysed using a commercially available computational fluid dynamic package ANSYS FLUENT. A different approach was followed to carry out the empirical flow visualisation and predict sound pressure levels. The aerodynamic characterisation of the vehicle was done utilising the widely used shear stress transport turbulence model, while the analysis of wind noise and the contributing vortices employed a large eddy simulation. This approach significantly reduced computational time ...

Yagnavalkya Mukkamala

Papers

Aerodynamic study of formula SAE car

Single phase flow heat transfer and pressure drop measurements in doubly enhanced tubes

Contemporary trends in thermo-hydraulic testing and modeling of automotive radiators deploying nano-coolants and aerodynamically efficient air-side fins

Bird strike analysis of jet engine fan blade

Computational aero-acoustic modelling of external rear-view mirrors on a mid-sized Sedan