Significance of Transient Exergy Terms in a New Tray Design Solar Desalination Device

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Gregory J. Kowalski ◽  
Masoud Modaresifar ◽  
Mansour Zenouzi
Keyword(s):  
Energy Recovery ◽  
Alternative Energy ◽  
Energy Systems ◽  
Second Law ◽  
Exergy Destruction ◽  
Renewable Energy Systems ◽  
Solar Desalination ◽  
Second Law Analysis ◽  
Storage Term ◽  
Variable Energy

An investigation of the transient exergy property term, exergy storage, for a new desalination tray design was performed. It was illustrated that exergy destruction rates provide a means of comparing alternative energy solutions and a measure of their sustainability. To satisfy these objectives one needs accurate calculation of exergy destruction rates. It was confirmed that neglecting the exergy storage term is not a valid approximation for the hourly and daily averaged values of the second law analysis. For a solar desalination system neglecting the exergy storage terms introduced a maximum difference in the exergy destruction rate of 7.4% and a difference of 7.3% in the daily average. In the solar desalination process with energy recovery the second law performance is greater than that for the reverse osmosis (RO) process, the chief competitor, when the exergy storage terms are correctly included in the analysis. The results demonstrate that for variable energy sources such as renewable energy systems, the second law analysis provides a measure of the sustainability of competing system and that the exergy storage terms should be included in the analysis.

Transient Exergy Analysis for Solar Desalination Processes

2013 ◽  
Author(s):  
Gregory J. Kowalski ◽  
Masoud Modaresifar ◽  
Mansour Zenouzi
Keyword(s):  
Entropy Production ◽  
Alternative Energy ◽  
Second Law ◽  
Entropy Production Rate ◽  
Production Rates ◽  
Renewable Energy Systems ◽  
Solar Desalination ◽  
Second Law Analysis ◽  
Storage Term ◽  
Variable Energy

An investigation of the transient entropy property term, entropy storage, for a desalination device was performed. It was illustrated that entropy production rates provide a means of comparing alternative energy solutions and a measure of their sustainability. To satisfy these objectives one needs accurate calculation of entropy production rates. It was confirmed that neglecting the exergy storage term is not a valid approximation for the hourly and daily averaged values of the second law analysis. For a solar desalination system neglecting the exergy storage terms introduced a maximum difference in the entropy production rate of 7.4% and a difference of 7.3% in the daily average. In the solar desalination process with heat recovery the second law performance is greater than that for the reverse osmosis process, the chief competitor, when the exergy storage terms are correctly included in the analysis. The results demonstrate that for variable energy sources such as renewable energy systems, the second law analysis provides a measure of the sustainability of competing system and that the exergy storage terms should be included in the analysis.

Teaching Power Cycles by Comparative First- and Second-Law Analysis of Their Evolution

1997 ◽  
Vol 25 (1) ◽  
pp. 13-31 ◽  
Author(s):  
William R. Dunbar ◽  
Noam Lior
Keyword(s):  
Power Plants ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Energy Systems ◽  
Thermal Engineering ◽  
Second Law ◽  
Intellectual Curiosity ◽  
Educational Approach ◽  
Power Cycles ◽  
Second Law Analysis

The teaching of power cycles in courses of thermodynamics or thermal engineering was traditionally based on first-law analysis. Second-law analysis was typically taught later, and not integrated with it. This approach leaves the student ignorant of the effect of operating parameters and cycle modifications on the accompanying exergy (availability) magnitudes and component irreversibilities, which are necessary for evaluating the potential for further system improvements. It also leaves many of the students with an ambiguous understanding of the exergy concept and its use. Consonant with the gradual changes in this educational approach, which increasingly attempt to integrate first- and second-law analysis, this paper recommends a strategy which integrates exergy analysis into the introduction and teaching of energy systems, demonstrated and made didactically appealing by an examination of the historical evolution of power plants, emphasizing the objectives for improvements, accomplishments, constraints, and consequently the remaining opportunities. Important conclusions from exergy analysis, not obtainable from the conventional energy analysis, were emphasized. It was found that this approach evoked the intellectual curiosity of students and increased their interest in the course.

Introducing a Novel Air Handling Unit Based on Focusing on Turbulent Exhaust Air Energy-Exergy Recovery Potential

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Yuanzhou Zheng ◽  
Rasool Kalbasi ◽  
Arash Karimipour ◽  
Peng Liu ◽  
Quang-Vu Bach
Keyword(s):  
Energy Consumption ◽  
Energy Demand ◽  
Energy Recovery ◽  
Primary Energy ◽  
Second Law ◽  
The Novel ◽  
Heating Coil ◽  
Recovery Potential ◽  
Air Handling Unit ◽  
Second Law Analysis

Abstract A novel air handling unit (AHU) aimed at reducing energy consumption was introduced in this study. In the proposed novel AHU, the heating coil is completely removed, and therefore, no heating coil energy demand is needed. The novel AHU used primary energy recovery as well as secondary one to utilize the return air energy and exergy. Through the first energy recovery unit, the return air exergy was recovered, while in the secondary heat exchanger, return air energy was recycled. Results showed that using the novel AHU leads to a reduction in energy consumption as well as the exergy losses. Three climate zones of A, B, and C were selected to assess the novel AHU performance. From the first law viewpoint, at zone B, using novel AHU has priority over other zones, while in the second law analysis, utilizing the novel AHU at zones B and C is more beneficial. Based on the first law analysis, owing to using novel AHU, energy consumption reduced up to 55.2% at Penang climate zone. Second law analysis revealed that utilizing the novel AHU decreased the irreversibility up to 51.4% in the Vancouver climate region.

scholarly journals Investigation of an Innovative Cascade Cycle Combining a Trilateral Cycle and an Organic Rankine Cycle (TLC-ORC) for Industry or Transport Application

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3032 ◽  
Author(s):  
Xiaoli Yu ◽  
Zhi Li ◽  
Yiji Lu ◽  
Rui Huang ◽  
Anthony Roskilly
Keyword(s):  
High Temperature ◽  
System Performance ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Second Law ◽  
Exergy Destruction ◽  
Second Law Analysis ◽  
Net Power Output

An innovative cascade cycle combining a trilateral cycle and an organic Rankine cycle (TLC-ORC) system is proposed in this paper. The proposed TLC-ORC system aims at obtaining better performance of temperature matching between working fluid and heat source, leading to better overall system performance than that of the conventional dual-loop ORC system. The proposed cascade cycle adopts TLC to replace the High-Temperature (HT) cycle of the conventional dual-loop ORC system. The comprehensive comparisons between the conventional dual-loop ORC and the proposed TLC-ORC system have been conducted using the first and second law analysis. Effects of evaporating temperature for HT and Low-Temperature (LT) cycle, as well as different HT and LT working fluids, are systematically investigated. The comparisons of exergy destruction and exergy efficiency of each component in the two systems have been studied. Results illustrate that the maximum net power output, thermal efficiency, and exergy efficiency of a conventional dual-loop ORC are 8.8 kW, 18.7%, and 50.0%, respectively, obtained by the system using cyclohexane as HT working fluid at THT,evap = 470 K and TLT,evap = 343 K. While for the TLC-ORC, the corresponding values are 11.8 kW, 25.0%, and 65.6%, obtained by the system using toluene as a HT working fluid at THT,evap = 470 K and TLT,evap = 343 K, which are 34.1%, 33.7%, and 31.2% higher than that of a conventional dual-loop ORC.

Exergy Analysis of Various Absorption Heat Transformer Systems Using Classical and Modified Gouy–Stodola Equation

2015 ◽  
Vol 23 (01) ◽  
pp. 1550006 ◽  
Author(s):  
T. Goel ◽  
G. Sachdeva
Keyword(s):  
Exergy Analysis ◽  
Waste Heat ◽  
Lithium Bromide ◽  
Second Law ◽  
Operating Parameters ◽  
Classical Approach ◽  
Exergy Destruction ◽  
Second Law Analysis ◽  
Heat Transformer ◽  
Study Performance

In the present study, performance evaluation of three different configurations of absorption heat transformer (AHT) is carried out by supplying the waste heat of same mass and same temperature; and exergy analysis is done using both the classical and modified Gouy–Stodola equation. For this a mathematical model is developed for all the three arrangements in Engineering Equation Solver. Water–lithium bromide is used as a working pair. The results of exergy destruction with classical and modified Gouy–Stodola equation are compared for different systems. Further various operating parameters are varied to predict the performance of the systems on the basis of second law analysis. The result showed that the amount of hot fluid produced in absorber is more for system 3 as compared to other configurations. The irreversibility calculated by the modified approach comes out to be 25.78%, 23.60%, and 23.45% more than the exergy destruction obtained by the classical approach in the three cases, respectively. Thus, there is a need to employ the modified approach of Gouy–Stodola equation for calculating the real irreversibility which helps in predicting the scope of improvement and the performance of the system more accurately.

Second Law Analysis of Aerodynamic Losses: Results for a Cambered Vane With and Without Film Cooling

2012 ◽  
Author(s):  
Phil Ligrani ◽  
Jae Sik Jin
Keyword(s):  
Surface Roughness ◽  
Mach Number ◽  
Turbulence Intensity ◽  
Film Cooling ◽  
Chord Length ◽  
Second Law ◽  
Exergy Destruction ◽  
Freestream Turbulence ◽  
Second Law Analysis ◽  
Aerodynamic Losses

Results of second law analysis of experimentally-measured aerodynamic losses are presented for a cambered vane with and without film cooling, including comparisons with similar results from a symmetric airfoil. Included are distributions of local entropy creation, as well as mass-averaged magnitudes of global exergy destruction. The axial chord length of the cambered vane is 4.85 cm, the true chord length is 7.27 cm, and the effective pitch is 6.35 cm. Data are presented for three airfoil Mex distributions (including one wherein the flow is transonic), magnitudes of inlet turbulence intensity from 1.1 percent to 8.2 percent, and ks/cx surface roughness values of 0, 0.00108, and 0.00258. The associated second law aerodynamics losses are presented for two different measurement locations downstream of the vane trailing edge (one axial chord length and 0.25 axial chord length). The surface roughness, when present, simulates characteristics of the actual roughness which develops on operating turbine airfoils from a utility power engine, over long operating times, due to particulate deposition and to spallation of thermal barrier coatings (TBCs). Quantitative surface roughness characteristics which are matched include equivalent sandgrain roughness size, as well as the irregularity, non-uniformity, and the three-dimensional irregular arrangement of the roughness. Relative to a smooth, symmetric airfoil with no film cooling at low Mach number and low freestream turbulence intensity, overall, the largest increases in exergy destruction occur with increasing Mach number, and increasing surface roughness. Important variations are also observed as airfoil camber changes. Progressively smaller mass-averaged exergy destruction increases are then observed with changes of freestream turbulence intensity, and different film cooling conditions. In addition, the dependences of overall exergy destruction magnitudes on mainstream turbulence intensity and freestream Mach number are vastly different as level of vane surface roughness changes. When film cooling is present, overall mass-averaged exergy destruction magnitudes are significantly less than values associated with increased airfoil surface roughness for both the cambered vane and the symmetric airfoil. Exergy destruction values (associated with wake aerodynamic losses) for the symmetric airfoil with film cooling are then significantly higher than data from the cambered vane with film cooling, when compared at a particular blowing ratio.

Differences Between Second Law Analysis and Pinch Technology

1995 ◽  
Vol 117 (3) ◽  
pp. 186-191 ◽  
Author(s):  
D. A. Sama
Keyword(s):  
Heat Exchanger ◽  
Energy Recovery ◽  
Maximum Energy ◽  
Global Optimum ◽  
Second Law ◽  
Heat Exchanger Network ◽  
Second Law Analysis ◽  
Heat Exchanger Networks ◽  
Pinch Technology ◽  
Correct Design

The use of second law analysis to design a heat exchanger network is compared with the pinch technology approach. Differences between the two methods are identified and discussed in the light of claims made by practitioners of pinch technology. Second law insights are used to easily identify and correct design errors in a heat exchanger network, and to design maximum energy recovery networks. More importantly, it is found that use of the second law provides an understanding of the process which is totally absent in the pinch technology approach. The claims that pinch technology can find global optimum solutions, that only pinch technology can find maximum energy recovery heat exchanger networks, and that pinch technology is a form of second law analysis, are considered, discussed, and shown to be invalid.

scholarly journals Design Analysis on Transient, Steady-State and Fault Condition of the Grid connected Renewable Energy Systems and its Correction Techniques

2021 ◽  
Vol 7 (09) ◽  
pp. 211-216
Author(s):  
R Sekar, Suresh D S and H Naganagouda
Keyword(s):  
Steady State ◽  
Alternative Energy ◽  
Electrical Power ◽  
Energy Systems ◽  
Renewable Energy Systems ◽  
Electrical Stress ◽  
Technical Issues ◽  
Bus Structure ◽  
The Common ◽  
Alternative Energy Resources

In the recent years, using the existing electrical resources to meet the electrical power demand is a challenging one. To address the issues, an alternative energy resources are bringing together to support the existing resources. And it is known that integrating the electrical resources together having lot more technical issues because of their unique features. So bringing them into the common platform and making them together is a wise solution. This paper also an attempt to address one of the issues on the electrical resources integration in the common DC bus structure. In the common bus, various loads with different ratings use to be connected and its recurrent changes such as ON and OFF are not in the control. Due to this the electrical stress in the common bus will increase. In order to minimize the variations a compensation mechanism must be used for avoiding the disturbance during transient, steady-state and fault conditions.

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