scholarly journals Energy and Exergy Evaluation of a Two-Stage Axial Vapour Compressor on the LNG Carrier

Entropy ◽  
2020 ◽  
Vol 22 (1) ◽  
pp. 115 ◽  
Author(s):  
Igor Poljak ◽  
Josip Orović ◽  
Vedran Mrzljak ◽  
Dean Bernečić
Keyword(s):  
Average Energy ◽  
Exergy Efficiency ◽  
Dual Fuel ◽  
Two Stage ◽  
Ambient Temperatures ◽  
Second Stage ◽  
Energy And Exergy ◽  
Compressor Performance ◽  
Main Engine ◽  
Compressor Efficiency

Data from a two-stage axial vapor cryogenic compressor on the dual-fuel diesel–electric (DFDE) liquefied natural gas (LNG) carrier were measured and analyzed to investigate compressor energy and exergy efficiency in real exploitation conditions. The running parameters of the two-stage compressor were collected while changing the main propeller shafts rpm. As the compressor supply of vaporized gas to the main engines increases, so does the load and rpm in propulsion electric motors, and vice versa. The results show that when the main engine load varied from 46 to 56 rpm at main propulsion shafts increased mass flow rate of vaporized LNG at a two-stage compressor has an influence on compressor performance. Compressor average energy efficiency is around 50%, while the exergy efficiency of the compressor is significantly lower in all measured ranges and on average is around 34%. The change in the ambient temperature from 0 to 50 °C also influences the compressor’s exergy efficiency. Higher exergy efficiency is achieved at lower ambient temperatures. As temperature increases, overall compressor exergy efficiency decreases by about 7% on average over the whole analyzed range. The proposed new concept of energy-saving and increasing the compressor efficiency based on pre-cooling of the compressor second stage is also analyzed. The temperature at the second stage was varied in the range from 0 to −50 °C, which results in power savings up to 26 kW for optimal running regimes.

Experimental investigation of an active inclined solar panel absorber solar still - Energy and Exergy analysis

2021 ◽  
Author(s):  
Mohamed Thalib Mohamed Rafeek ◽  
Vimala Muthu ◽  
Muthu Manokar Athikesavan ◽  
Ravishankar Sathyamurthy ◽  
Abd Elnaby Kabeel
Keyword(s):  
Mass Flow ◽  
Average Energy ◽  
Electrical Energy ◽  
Exergy Efficiency ◽  
Solar Panel ◽  
Water Yield ◽  
Flow Rates ◽  
Pv Panel ◽  
Energy And Exergy ◽  
Mass Flow Rates

Abstract The objective of the current study is to investigate the performance of the Inclined Solar Panel Basin Still (ISPBS) incorporated with a Spiral Tube Collector (STC) for various mass flow rates of water (mf). The maximum potable water yield of 8.1, 6.9 and 6.1 kg is obtained for different mass flow rates of 1.8, 3.2 and 4.7 kg/hr in each instance. Also, for mf values of 1.8, 3.2 and 4.7 kg per hour, the daily average energy and exergy efficiency of the ISPBS is recorded to be 47.9, 39.3 and 31.02 % and 9.8, 7.9 and 5.6 % in each instance. The average electrical, energy and exergy efficiency of the PV panel is noted to be 6.5, 7.1 and 7.5 %, 15.67, 17.1 and 18.04 % and 20.03, 22.21 and 23.36 % for mf values of 1.8, 3.2 and 4.7 kg/hr in each instance. The rise in mf causes a drop in the fresh water production yield, thermal, exergy and overall thermal effectiveness and an enhancement in the power production of the panel, electrical, thermal, exergy and overall exergy efficiency of the system.

Experimental study on a two-stage rolling piston CO2 compressor based on p–V indicator diagrams

2011 ◽  
Vol 226 (4) ◽  
pp. 995-1003 ◽  
Author(s):  
J Yang ◽  
Z Qi ◽  
J Chen ◽  
Z Chen
Keyword(s):  
Experimental Study ◽  
Operating Conditions ◽  
Test Rig ◽  
Two Stage ◽  
Second Stage ◽  
Compressor Inlet ◽  
Compressor Performance ◽  
Overall Efficiency ◽  
Rolling Piston ◽  
Discharge Pressure

In this article, a new two-stage rolling piston CO2 compressor was developed. A test rig was designed to measure the performance of this compressor. Based on the measured p–V indicator diagram, the distributions of indicated power and compressor performance under various operating conditions have been analysed in detail. It is shown that the discharge passage loss of the first stage and the suction passage loss of the second stage are much higher than other losses for the tested compressor. The overall efficiency of the tested compressor decreases by 1.2 per cent with the decrease of the discharge pressure at the same suction conditions. It is also found that the superheating at the compressor inlet has very small (0.3 per cent) effect on the compressor performance.

scholarly journals Three Approaches to Low-Duty Turbo Compressor Efficiency Exploitation Evaluation

2020 ◽  
Vol 10 (10) ◽  
pp. 3373
Author(s):  
Igor Poljak ◽  
Ivica Glavan ◽  
Josip Orović ◽  
Vedran Mrzljak
Keyword(s):  
Operating Regime ◽  
Boiler Load ◽  
Energy And Exergy ◽  
Compressor Performance ◽  
Turbo Compressor ◽  
Liquid Natural Gas ◽  
Compressor Efficiency ◽  
Operating Regimes ◽  
Isentropic Efficiency ◽  
Diagram Techniques

This paper presents three approaches for isentropic, energy, and exergy evaluations of a low-duty liquid natural gas (LNG) vapor turbo compressor during exploitation on a conventional LNG carrier. The evaluation was conducted on the measured performance parameters under 22 various turbo compressor operating regimes. The turbo compressor performance was evaluated in the temperature span from −69 to −105 °C and during changes in the rpm of the main propulsion turbine and, consequently, the main boiler load. The results show that the highest measured turbo compressor isentropic efficiency is in agreement with the manufacturer specifications, equaling 75.23% at a main propulsion turbine rpm of 53.5. At the highest measured loads and rpm, the turbo compressor energy and exergy efficiencies reach the highest values of 57.81% and 28.51%, respectively. In each observed operating regime, the influence of the ambient temperature change on the turbo compressor exergy efficiency was investigated. At the lowest and the highest measured loads, turbo compressor energy and exergy flow streams are presented in a Sankey diagram. Techniques for cargo temperature maintenance during the ship voyage are presented, as the results show that low suction gas temperatures influence turbo compressor efficiency.

A Numerical Analysis of the Effects of Liquid Carryover on the Performance of a Two-Stage Centrifugal Compressor

2018 ◽  
Author(s):  
Chaitanya V. Halbe ◽  
Walter F. O’Brien ◽  
William T. Cousins ◽  
Vishnu Sishtla
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Computational Method ◽  
Cfd Analysis ◽  
Compression Process ◽  
Two Stage ◽  
Two Phase ◽  
Droplet Dynamics ◽  
Second Stage ◽  
Compressor Performance

To extend the current understanding of the effects of liquid carryover on compressor performance, a detailed analysis including the aerothermodynamics of the compression process and the flow field within the compressor is required. This paper presents a CFD analysis of a two-stage, in-line centrifugal compressor, operating in a two-phase flow environment of a single constituent, refrigerant R134a. The computational method implemented in this analysis accounts for the real gas behavior, and also incorporates the effects of interphase heat, mass and momentum transfer, as well as the droplet dynamics. The investigations revealed that liquid carryover altered the flow field within the compressor, causing both stages to operate at off-design conditions. This effect was observed to be more pronounced for the second stage. The overall effects of liquid carryover were shown to be detrimental to the compressor performance. Increasing the amount of liquid carryover resulted in further lowering of the performance. On the other hand, the effects of the size of the ingested droplets were seen to be negligible.

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

2019 ◽  
Author(s):  
Rafael Mosquim ◽  
Carlos Eduardo Keutenedjian Mady
Keyword(s):  
Exergy Efficiency ◽  
Passenger Vehicle ◽  
Energy And Exergy ◽  
Vehicle Fleet

An Enhanced Two Stage MMSE Equalizer for Coded FBMC/OQAM Systems

2019 ◽  
Vol 10 (1) ◽  
pp. 69-82 ◽  
Author(s):  
Mohammad Rizk Assaf ◽  
Abdel-Nasser Assimi
Keyword(s):  
Error Propagation ◽  
Channel Model ◽  
Error Correcting Codes ◽  
Two Stage ◽  
Probability Of Error ◽  
Second Stage ◽  
Different Types ◽  
Mmse Equalizer ◽  
And Performance ◽  
Ici Cancellation

In this article, the authors investigate the enhanced two stage MMSE (TS-MMSE) equalizer in bit-interleaved coded FBMC/OQAM system which gives a tradeoff between complexity and performance, since error correcting codes limits error propagation, so this allows the equalizer to remove not only ICI but also ISI in the second stage. The proposed equalizer has shown less design complexity compared to the other MMSE equalizers. The obtained results show that the probability of error is improved where SNR gain reaches 2 dB measured at BER compared with ICI cancellation for different types of modulation schemes and ITU Vehicular B channel model. Some simulation results are provided to illustrate the effectiveness of the proposed equalizer.

scholarly journals Correction to: A comparative energy and exergy efficiency study of hemispherical and single-slope solar stills

2021 ◽  
Author(s):  
Mohammed El Hadi Attia ◽  
Abd Elnaby Kabeel ◽  
Abdelkader Bellila ◽  
Athikesavan Muthu Manokar ◽  
Ravishankar Sathyamurthy ◽  
...  
Keyword(s):  
Exergy Efficiency ◽  
Energy And Exergy

scholarly journals Correction to: Energy and exergy efficiency analysis of solar still incorporated with copper plate and phosphate pellets as energy storage material

2021 ◽  
Author(s):  
Rajendra Prasad Arani ◽  
Mohammed El Hadi Attia ◽  
Wael Al-Kouz ◽  
Asif Afzal ◽  
Muthu Manokar Athikesavan ◽  
...  
Keyword(s):  
Energy Storage ◽  
Efficiency Analysis ◽  
Copper Plate ◽  
Exergy Efficiency ◽  
Solar Still ◽  
Storage Material ◽  
Energy And Exergy ◽  
Energy Storage Material

Personalised attraction recommendation for enhancing topic diversity and accuracy

2021 ◽  
pp. 016555152199980
Author(s):  
Yuanyuan Lin ◽  
Chao Huang ◽  
Wei Yao ◽  
Yifei Shao
Keyword(s):  
Real World ◽  
Information Overload ◽  
Two Stage ◽  
Misclassification Cost ◽  
Second Stage ◽  
Low Visibility ◽  
Recommendation Diversity ◽  
Optimisation Model ◽  
Definition Of ◽  
Improved Methods

Attraction recommendation plays an important role in tourism, such as solving information overload problems and recommending proper attractions to users. Currently, most recommendation methods are dedicated to improving the accuracy of recommendations. However, recommendation methods only focusing on accuracy tend to recommend popular items that are often purchased by users, which results in a lack of diversity and low visibility of non-popular items. Hence, many studies have suggested the importance of recommendation diversity and proposed improved methods, but there is room for improvement. First, the definition of diversity for different items requires consideration for domain characteristics. Second, the existing algorithms for improving diversity sacrifice the accuracy of recommendations. Therefore, the article utilises the topic ‘features of attractions’ to define the calculation method of recommendation diversity. We developed a two-stage optimisation model to enhance recommendation diversity while maintaining the accuracy of recommendations. In the first stage, an optimisation model considering topic diversity is proposed to increase recommendation diversity and generate candidate attractions. In the second stage, we propose a minimisation misclassification cost optimisation model to balance recommendation diversity and accuracy. To assess the performance of the proposed method, experiments are conducted with real-world travel data. The results indicate that the proposed two-stage optimisation model can significantly improve the diversity and accuracy of recommendations.

scholarly journals Energetic and exergetic analysis of a convective drier: A case study of potato drying process

2020 ◽  
Vol 5 (1) ◽  
pp. 563-572
Author(s):  
Iman Golpour ◽  
Mohammad Kaveh ◽  
Reza Amiri Chayjan ◽  
Raquel P. F. Guiné
Keyword(s):  
Energy Consumption ◽  
Research Work ◽  
Specific Energy Consumption ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Energy Utilization ◽  
Convective Drying ◽  
Drying Time ◽  
Energy And Exergy ◽  
Exergy Losses

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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