Energy and Exergy Efficiency of the Brazilian Passenger Vehicle Fleet – 1970-2017

AbstractThis research work focused on the evaluation of energy and exergy in the convective drying of potato slices. Experiments were conducted at four air temperatures (40, 50, 60 and 70°C) and three air velocities (0.5, 1.0 and 1.5 m/s) in a convective dryer, with circulating heated air. Freshly harvested potatoes with initial moisture content (MC) of 79.9% wet basis were used in this research. The influence of temperature and air velocity was investigated in terms of energy and exergy (energy utilization [EU], energy utilization ratio [EUR], exergy losses and exergy efficiency). The calculations for energy and exergy were based on the first and second laws of thermodynamics. Results indicated that EU, EUR and exergy losses decreased along drying time, while exergy efficiency increased. The specific energy consumption (SEC) varied from 1.94 × 105 to 3.14 × 105 kJ/kg. The exergy loss varied in the range of 0.006 to 0.036 kJ/s and the maximum exergy efficiency obtained was 85.85% at 70°C and 0.5 m/s, while minimum exergy efficiency was 57.07% at 40°C and 1.5 m/s. Moreover, the values of exergetic improvement potential (IP) rate changed between 0.0016 and 0.0046 kJ/s and the highest value occurred for drying at 70°C and 1.5 m/s, whereas the lowest value was for 70°C and 0.5 m/s. As a result, this knowledge will allow the optimization of convective dryers, when operating for the drying of this food product or others, as well as choosing the most appropriate operating conditions that cause the reduction of energy consumption, irreversibilities and losses in the industrial convective drying processes.

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A comparative energy and exergy efficiency study of hemispherical and single-slope solar stills

Environmental Science and Pollution Research ◽

10.1007/s11356-021-13161-9 ◽

2021 ◽

Author(s):

Mohammed El Hadi Attia ◽

Abd Elnaby Kabeel ◽

Abdelkader Bellila ◽

Athikesavan Muthu Manokar ◽

Ravishankar Sathyamurthy ◽

...

Keyword(s):

Exergy Efficiency ◽

Energy And Exergy

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Energy and Exergy Efficiency Analysis of Fluid Flow and Heat Transfer in Sinter Vertical Cooler

Energies ◽

10.3390/en14154522 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4522

Author(s):

Zude Cheng ◽

Haitao Wang ◽

Junsheng Feng ◽

Yongfang Xia ◽

Hui Dong

Keyword(s):

Heat Transfer ◽

Energy Efficiency ◽

Fluid Flow ◽

Waste Heat ◽

Exergy Efficiency ◽

Inlet Temperature ◽

Operational Parameters ◽

Flow And Heat Transfer ◽

Maximum Value ◽

Energy And Exergy

In order to fully understand the energy and exergy transfer processes in sinter vertical coolers, a simulation model of the fluid flow and heat transfer in a vertical cooler was established, and energy and exergy efficiency analyses of the gas–solid heat transfer in a vertical cooler were conducted in detail. Based on the calculation method of the whole working condition, the suitable operational parameters of the vertical cooler were obtained by setting the net exergy efficiency in the vertical cooler as the indicator function. The results show that both the quantity of sinter waste heat recovery (SWHR) and energy efficiency increased as the air flow rate (AFR) increased, and they decreased as the air inlet temperature (AIT) increased. The increase in the sinter inlet temperature (SIT) resulted in an increase in the quantity of SWHR and a decrease in energy efficiency. The air net exergy had the maximum value as the AFR increased, and it only increased monotonically as the SIT and AIT increased. The net exergy efficiency reached the maximum value as the AFR and AIT increased, and the increase in the SIT only resulted in a decrease in the net exergy efficiency. When the sinter annual production of a 360 m2 sintering machine was taken as the processing capacity of the vertical cooler, the suitable operational parameters of the vertical cooler were 190 kg/s for the AFR, and 353 K for the AIT.

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Energy and exergy analysis of a downstream single-row air washer at different droplet diameters for air cooling application

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211064573 ◽

2022 ◽

pp. 095440622110645

Author(s):

Minhua Huang ◽

Haiqiao Wang ◽

Feng Tian ◽

Junxin Huang ◽

Shiqiang Chen ◽

...

Keyword(s):

Performance Indicator ◽

Droplet Diameter ◽

Exergy Efficiency ◽

Air Cooling ◽

Design Calculation ◽

Outlet Temperature ◽

Single Row ◽

Energy And Exergy ◽

Water Gas ◽

Gas Ratio

This study proposes a downstream single-row air washer for air cooling. The theoretical energy and exergy balance models were established at different droplet diameters and verified by the experimental data. Based on the abovementioned theoretical relationship, the single performance indicator of heat exchange efficiency (HEE) and exergy efficiency was quantitatively analyzed; a comprehensive analysis method of two indicators was proposed, combining HEE and exergy efficiency, and a numerical simulation was carried out. Results show that the smaller the droplet diameter and the larger the water–air ratio, the lower the dry-bulb temperature of the outlet air and the higher the HEE and exergy flux destruction. When the droplet diameter is less than 440 μm, the droplet diameter does not affect exergy efficiency and dry-bulb temperature. When the droplet diameter is larger than 440 μm, the droplet diameter is positively correlated with the air outlet dry-bulb temperature and exergy efficiency; in contrast, the water–gas ratio is negatively correlated with the air outlet dry-bulb temperature. An engineering case reveals that when the air outlet temperature is less than 34°C, the critical water–gas ratio can be set as 2.6 (mass ratio). At this time, the HEE is more than 90%, the exergy efficiency is more than 60%, and the critical value of droplet diameter is 440 μm. The research results provide an essential theoretical basis for the optimization of engineering design calculation.

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Energy and Exergy Analyses of Tube Banks in Waste Heat Recovery Applications

Energies ◽

10.3390/en11082094 ◽

2018 ◽

Vol 11 (8) ◽

pp. 2094 ◽

Cited By ~ 7

Author(s):

Mustafa Erguvan ◽

David MacPhee

Keyword(s):

Energy Efficiency ◽

Reynolds Number ◽

Heat Recovery ◽

Waste Heat ◽

Cross Flow ◽

Exergy Efficiency ◽

Circular Cylinders ◽

Published Data ◽

Energy And Exergy ◽

Exergy Analyses

In this study, energy and exergy analyses have been investigated numerically for unsteady cross-flow over heated circular cylinders. Numerous simulations were conducted varying the number of inline tubes, inlet velocity, dimensionless pitch ratios and Reynolds number. Heat leakage into the domain is modeled as a source term. Numerical results compare favorably to published data in terms of Nusselt number and pressure drop. It was found that the energy efficiency varies between 72% and 98% for all cases, and viscous dissipation has a very low effect on the energy efficiency for low Reynolds number cases. The exergy efficiency ranges from 40–64%, and the entropy generation due to heat transfer was found to have a significant effect on exergy efficiency. The results suggest that exergy efficiency can be maximized by choosing specific pitch ratios for various Reynolds numbers. The results could be useful in designing more efficient heat recovery systems, especially for low temperature applications.

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Greenhouse gas consequences of the China dual credit policy

Nature Communications ◽

10.1038/s41467-020-19036-w ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Xin He ◽

Shiqi Ou ◽

Yu Gan ◽

Zifeng Lu ◽

Steven Victor Przesmitzki ◽

...

Keyword(s):

Greenhouse Gas ◽

Internal Combustion Engines ◽

Dual Credit ◽

Ghg Emissions ◽

Passenger Vehicle ◽

Credit Policy ◽

Modeling Framework ◽

New Energy ◽

Vehicle Fleet ◽

New Energy Vehicle

Abstract For over ten years, China has been the largest vehicle market in the world. In order to address energy security and air quality concerns, China issued the Dual Credit policy to improve vehicle efficiency and accelerate New Energy Vehicle adoption. In this paper, a market-penetration model is combined with a vehicle fleet model to assess implications on greenhouse gas (GHG) emissions and energy demand. Here we use this integrated modeling framework to study several scenarios, including hypothetical policy tweaks, oil price, battery cost and charging infrastructure for the Chinese passenger vehicle fleet. The model shows that the total GHGs of the Chinese passenger vehicle fleet are expected to peak in 2032 under the Dual Credit policy. A significant reduction in GHG emissions is possible if more efficient internal combustion engines continue to be part of the technology mix in the short term with more New Energy Vehicle penetration in the long term.

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Optimization of four models flatbread bakery machines in Iran

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-11-2018-0636 ◽

2019 ◽

Vol 30 (6) ◽

pp. 3399-3434 ◽

Cited By ~ 1

Author(s):

Soroush Sadripour ◽

Mohammad Estajloo ◽

Seyed Abdolmehdi Hashemi ◽

Ali J. Chamkha ◽

Mahmoud Abbaszadeh

Keyword(s):

Energy Consumption ◽

Exergy Efficiency ◽

Experimental Investigations ◽

Content Type ◽

Numerical Studies ◽

Excess Air ◽

High Preference ◽

Energy And Exergy ◽

Traditional Bread ◽

Wasted Energy

Purpose The purpose of this study is to reduce energy consumption in bakeries. Due to fulfill this demand, quite a few parameters such as energy and exergy efficiency, energy waste and fuel consumption by different traditional flatbreads bakeries (Sangak, Barbari, Taftun and Lavash should be monitored and their roles should not be neglected. Design/methodology/approach In the present study, experimental measurements and mathematical modeling are used to scrutinize and investigate the effects of the aforementioned parameters on energy consumption by bakeries. Findings The results show that by doing reported methods in this paper, the wasted energy of the walls can be decreased by about 65 per cent; and also, by controlling the combustion reaction to perform with 5 per cent excess air, the wasted energy of excess air declines by about 90 per cent. And finally, the energy and exergy efficiency of bakeries is increased, and as a result, the annual energy consumption of Sangak, Barbari, Taftun and Lavash bakeries diminish about 71, 59, 57 and 40 per cent, respectively. Originality/value As evidenced by the literature review, it can be observed that neither numerical studies nor experimental investigations have been conducted about energy and exergy analyses of Iranian machinery traditional flatbread bakeries. It is clear that due to a high preference of Iranians to use the traditional bread and also the popularity of baking this kind of bread in Iran, if it is possible to enhance the traditional oven conditions to decrease the loss of natural gas instead of industrializing the bread baking, the energy consumption in the country can be optimized.

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