Showing papers on "Thermal efficiency published in 2020"

A state of art review and future viewpoint on advance cooling techniques for Lithium–ion battery system of electric vehicles

Abstract: Electric Vehicles (EVs) have emerged as most promising means of transport owing to the low operational costs, high speed, and energy-efficient battery technologies, where battery thermal management system (BTMS) is possibly the most crucial element of an EV. During the charging/discharging mode of EVs, a major focused area for the researcher is to maintain the optimal working temperature range of the batteries and reduce both the maximum temperature and temperature difference. Suitable and effective cooling methods can significantly reduce the adverse effect of the high surface temperature of battery cells and efficiently augments the battery thermal efficiency, improves the safety of EVs, and increase the service life. In this context, this work presents a detailed state of the art review of different BTMS technologies, including natural and forced air-cooling techniques, direct and indirect liquid cooling methods, and cooling by heat pipes. It is found that the air-cooled BTMS possesses advantageous features such as safe, consistent, and simple design, but the lower heat capacity and thermal efficiency of the air as a cooling medium restricts its application to a low capacity battery. This leads to employment of forced air-cooled BTMS under high charging/discharging rate, in which air flows through the channels inside the battery packs to provide the optimum cooling. Liquid-cooled BTMS is also emerging as one of the most promising cooling technologies, which requires attention to the sealing cover during the design stage to avoid leakages. The integration of metal plates with the mini channel can effectively improve the cooling performance, but the weight of the system is a major concern. Liquid metals, nanofluids, and boiling liquids are considered as the most prominent battery cooling methods owing to their higher thermal conductivity. The advancement in hybrid cooling using fins, nanofluids, PCM along with micro channels-based cooling will significantly improve the battery performance under high charging/discharging rate and attention should be given to compact design with a cheaper cost.

Investigation of energy performance in a U-shaped evacuated solar tube collector using oxide added nanoparticles through the emitter, absorber and transmittal environments via discrete ordinates radiation method

Abstract: This work is a three-dimensional numerical study of a U-shaped evacuated tube solar collector employing different types of oxide nanofluids including water–Al2O3, water–CuO and water–TiO2 under the steady-state condition. The simulation is performed using the single-phase method for nanofluid modeling, the DO method for radiation modeling, incompressible and fluid flow laminar regime. The thermo-physical properties of the water are considered as a function of temperature ranging from 0 to 150 °C. The obtained results showed that increasing both length and diameter of the U-shaped tubes of the solar collector enhances its thermal efficiency. Moreover, it is found that using oxide nanofluids results in an enhancement in the collector thermal performance which using water–CuO nanofluid causes 13.8, 1.5 and 1.3% higher collector thermal efficiency in comparison with employing pure water, water–TiO2 and water–Al2O3 nanofluids, respectively. It is also observed that the working fluid heat capacity plays an important role in the thermal performance of the evacuated tube solar collector.

Energy, exergy and emission analysis on a DI single cylinder diesel engine using pyrolytic waste plastic oil diesel blend

Abstract: Depletion of fossil fuels and stringent emission norms focus attention to discover an evitable source of alternative fuel in order to attribute a significant compensation on conventional fuels. Besides, waste management policies encourage the valorization of different wastes for the production of alternative fuels in order to reduce the challenges of waste management. In this context, pyrolysis has become an emerging trend to convert different wastes into alternate fuel and suitable to be used as a substitute fuel for CI engines. The current investigation provides a sustainable and feasible solution for waste plastic management by widening the gap between global plastic production and plastic waste generation. It investigates the performance and emission of a single cylinder DI four stroke diesel engine using waste plastic oil (WPO) derived from pyrolysis of waste plastics using Zeolite-A as catalyst. Engine load tests have been conducted taking waste plastic oil and subsequently a blend of waste plastic oil by 10%, 20%, and 30% in volume proportions with diesel as fuel. The performance of the test engine in terms of brake thermal efficiency is found marginally higher and brake specific fuel consumption comparatively lowest for 20% WPO-diesel blend than pure diesel. The NOx and HC emission is found lower under low load condition and became higher by increasing the load as compared to diesel. Fuel exergy was significantly increasing after blending of WPO with pure diesel, but exergetic efficiency of the blended fuels followed the reverse trend. However, increase in load of the engine improved the exergetic efficiency. The 20% WPO–diesel blended fuel is found suitable to be used as an alternative fuel for diesel engine.

A review on recent developments in thermal performance enhancement methods of flat plate solar air collector

Abstract: The recent studies on thermal performance enhancement of the flat plate solar air collectors are critically reviewed primarily regarding the absorber surface modifications, multiple-passes of air, porous absorbers, air-jet impingement on absorber surface, integration of heat storage materials, dual-purpose hybrid collectors and hybrid photovoltaic/thermal solar collectors. The formation of a laminar viscous layer over the surface causes poor heat transfer to airflow. Enhanced heat transfer surface area and residence time of air are vital factors for heat transfer augmentation using baffles, turbulators, roughness, and obstacles. The streamwise pitch ratio of the jet plate has the maximum contribution to friction and, subsequently, the heat transfer. The thermal efficiency of finned and porous absorber varies from 71.4% to 93%. The integration of phase change material and fins with solar air collector enhance daily thermal efficiency by 0.1%–4%, increasing further with honeycomb and porous structures. The application of agriculture waste as sensible heat storage material is an effective alternative to replace conventional materials. Electrical and thermal efficiencies of hybrid solar collector increased with the addition of thermal energy storage by 9% and 5%, which further enhanced by 3% with the addition of fins into the phase change materials. Thermo-economic performance of the dual-purpose collector and hybrid photovoltaic/thermal solar air collector is comparatively cost-effective with environmental benefits. This review article provides an insight into the recent critical findings on the thermal performance enhancement of the flat plate solar air collector to stimulate further developments towards the betterment of sustainable development.

Hierarchical Porous Aluminophosphate-Treated Wood for High-Efficiency Solar Steam Generation.

Abstract: Solar steam generation as a promising solar energy conversion technology has attracted considerable interest in achieving seawater desalination and water purification. Although wood with fast water transportation and excellent heat localization has drawn particular interest in regard to its application for solar steam generation, challenges still remain in terms of its complicated processing techniques and relatively low efficiency. Here, we propose a facile, cost-efficient, and scalable brushing method to prepare an aluminophosphate-treated wood (Wood@AlP) solar steam generation device. The aluminophosphate compound deposited on the wood surface can not only be considered as the Lewis acid catalyst capable of accelerating the formation of the carbon layer but also provide an aluminophosphate layer with a hierarchical porous structure, which is beneficial for broad solar absorption and vapor escape. On the other hand, benefiting from the natural hydrophilicity, low thermal conductivity, and excellent water transportation of wood, the obtained Wood@AlP device can float on seawater and exhibit a high solar thermal efficiency of 90.8% with a net evaporation rate of 1.423 kg m-2 h-1 under 1 sun illumination.

Enhancement in Combustion, Performance, and Emission Characteristics of a Diesel Engine Fueled with Ce-ZnO Nanoparticle Additive Added to Soybean Biodiesel Blends

Abstract: This study considered the impacts of diesel–soybean biodiesel blends mixed with 3% cerium coated zinc oxide (Ce-ZnO) nanoparticles on the performance, emission, and combustion characteristics of a single cylinder diesel engine. The fuel blends were prepared using 25% soybean biodiesel in diesel (SBME25). Ce-ZnO nanoparticle additives were blended with SBME25 at 25, 50, and 75 ppm using the ultrasonication process with a surfactant (Span 80) at 2 vol.% to enhance the stability of the blend. A variable compression ratio engine operated at a 19.5:1 compression ratio (CR) using these blends resulted in an improvement in overall engine characteristics. With 50 ppm Ce-ZnO nanoparticle additive in SBME25 (SBME25Ce-ZnO50), the brake thermal efficiency (BTE) and heat release rate (HRR) increased by 20.66% and 18.1%, respectively; brake specific fuel consumption (BSFC) by 21.81%; and the CO, smoke, and hydrocarbon (HC) decreased by 30%, 18.7%, and 21.5%, respectively, compared to SBME25 fuel operation. However, the oxides of nitrogen slightly rose for all the nanoparticle added blends. As such, 50 ppm of Ce-ZnO nanoparticle in the blend is a potent choice for the enhancement of engine performance, combustion, and emission characteristics.

Thermal evaluation of a heat pipe working with n-pentane-acetone and n-pentane-methanol binary mixtures

Abstract: In the present study, a set of experiments were accomplished to appraise the thermal performance and heat transfer of n-pentane-acetone and n-pentane-methanol mixtures inside a gravity-assisted thermosyphon heat pipe. Pure n-pentane, acetone and methanol were also tested as the carrying fluid to produce some reference data. The heat pipe was manufactured from copper with length and diameter of 290 and 20 mm, respectively. The effect of multiple factors covering the input heat to the evaporator section, the filling ratio of the carrying fluid, heat pipe tilt angle and also the type of the carrying fluid on temperature distribution and thermal performance of the heat pipe was investigated. The results demonstrated that the thermo-physical properties of the carrying fluid were the key factor controlling the heat pipe efficiency. The vapour pressure and boiling temperature of the carrying fluid controlled the thermal efficiency of the system such that for n-pentane-acetone, the highest thermal efficiency was obtained. Also, it was identified that the filling ratio of the system is a key operating factor such that the value of the filling ratio was small for the evaporative carrying fluid (binary mixtures), while it was large for the non-evaporative carrying fluids. Also, heat pipe tilt angle was impressed by the type of the carrying fluid; the optimum tilt angle was 55 degree for the binary mixtures, while it was 65° for the pure liquids.

Effect of Zinc Oxide Nano-Additives and Soybean Biodiesel at Varying Loads and Compression Ratios on VCR Diesel Engine Characteristics

Abstract: The present investigation is directed towards synthesis of zinc oxide (ZnO) nanoparticles and steady blending with soybean biodiesel (SBME25) to improve the fuel properties of SBME25 and enhance the overall characteristics of a variable compression ratio diesel engine The soybean biodiesel (SBME) was prepared using the transesterification reaction Numerous characterization tests were carried out to ascertain the shape and size of zinc oxide nanoparticles The synthesized asymmetric ZnO nanoparticles were dispersed in SBME25 at three dosage levels (25, 50, and 75 ppm) with sodium dodecyl benzene sulphonate (SDBS) surfactant using the ultrasonication process The quantified physicochemical properties of all the fuels blends were in symmetry with the American society for testing and materials (ASTM) standards Nanofuel blends demonstrated enhanced fuel properties compared with SBME25 The engine was operated at two different compression ratios (185 and 215) and a comparison was made, and best fuel blend and compression ratio (CR) were selected Fuel blend SBME25ZnO50 and compression ratio (CR) of 215 illustrated an overall enhancement in engine characteristics For SBME25ZnO50 and CR 215 fuel blend, brake thermal efficiency (BTE) increased by 232%, brake specific fuel consumption (BSFC) were reduced by 2666%, and hydrocarbon (HC), CO, smoke, and CO2 emissions were reduced by 32234%, 2821% 2255% and 2166%, respectively; in addition, the heat release rate (HRR) and mean gas temperature (MGT) improved, and ignition delay (ID) was reduced In contrast, the NOx emissions increased for all the nanofuel blends due to greater supply of oxygen and increase in the temperature of the combustion chamber At a CR of 185, a similar trend was observed, while the values of engine characteristics were lower compared with CR of 215 The properties of nanofuel blend SBME25ZnO50 were in symmetry and comparable to the diesel fuel