scholarly journals Energy and Entropy Analyses of a Pilot-Scale Dual Heating HDH Desalination System

Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1282
Author(s):  
Dahiru U. Lawal ◽  
Saad Abdul Jawad ◽  
Mostafa H. Sharqawy ◽  
Mohamed A. Antar
Keyword(s):  
Entropy Generation ◽  
Rate Ratio ◽  
Heat Rate ◽  
Pilot Scale ◽  
Entropy Analysis ◽  
Water Heater ◽  
Air Heater ◽  
First Case ◽  
Heated Humidification ◽  
Order Of Magnitude

This study focuses on energy and entropy analysis to theoretically investigate the performance of a pilot scale dual heated humidification-dehumidification (HDH) desalination system. Two cases of HDH systems are considered in the analysis. The first case is a dual heated (DH) cycle consisting of 1.59 kW air heater and 1.42 kW water heater with a heat rate ratio of 0.89 (CAOW-DH-I). Whereas the second case is a dual heated HDH cycle comprising of 1.59 kW air heater and 2.82 kW water heater with a heat rate ratio of 1.77 (CAOW-DH-II). As a first step, mathematical code was developed based on heat and mass transfer and entropy generation within the major components of the system. The code was validated against the experimental data obtained from a pilot scale HDH system and was found to be in a good agreement with the experimental results. Theoretical results revealed that there is an optimal mass flowrate ratio at which GOR is maximized, and entropy generation is minimized. Furthermore, the degree of irreversibility within the humidifier component is low and approaches zero, while the specific entropy generation within other components are relatively high and are of the same order of magnitude. Entropy analysis also showed that the dual heated system with heat rate ratio greater than unity is better than the one with heat rate ratio less than unity.

Second-Law Analysis of a Two-Phase Self-Pumping Solar Water Heater

1992 ◽  
Vol 114 (3) ◽  
pp. 188-193 ◽  
Author(s):  
H. A. Walker ◽  
J. H. Davidson
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Hot Water ◽  
Solar Water Heater ◽  
Total Entropy ◽  
Water Heating ◽  
Water Heater ◽  
Two Phase ◽  
Solar Water ◽  
Order Of Magnitude

Entropy generated by operation of a two-phase self-pumping solar water heater under Solar Rating and Certification Corporation rating conditions is computed numerically in a methodology based on an exergy cascade. An order of magnitude analysis shows that entropy generation is dominated by heat transfer across temperature differences. Conversion of radiant solar energy incident on the collector to thermal energy within the collector accounts for 87.1 percent of total entropy generation. Thermal losses are responsible for 9.9 percent of total entropy generation, and heat transfer across the condenser accounts for 2.4 percent of the total entropy generation. Mixing in the tempering valve is responsible for 0.7 percent of the total entropy generation. Approximately one half of the entropy generated by thermal losses is attributable to the self-pumping process. The procedure to determine total entropy generation can be used in a parametric study to evaluate the performance of two-phase hot water heating systems relative to other solar water heating options.

scholarly journals Thermohydraulic Performance and Entropy Generation of a Triple-Pass Solar Air Heater with Three Inlets

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6399
Author(s):  
Nguyen Minh Phu ◽  
Ngo Thien Tu ◽  
Nguyen Van Hap
Keyword(s):  
Reynolds Number ◽  
Air Temperature ◽  
Entropy Generation ◽  
Solar Air Heater ◽  
Minimum Entropy ◽  
Air Heater ◽  
The Third ◽  
Thermohydraulic Efficiency ◽  
The Difference ◽  
Minimum Entropy Generation

In this paper, a triple-pass solar air heater with three inlets is analytically investigated. The effects of airflow ratios of the second and third passes (ranging from 0 to 0.4), and the Reynolds number of the third pass (ranging from 8000 to 18,000) on the thermohydraulic efficiency and entropy generation are assessed. An absorber plate equipped with rectangular fins on both sides is used to enhance heat transfer. The air temperature change in the passes is represented by ordinary differential equations and solved by numerical integration. The results demonstrate that the effect of the third pass airflow ratio on the thermohydraulic efficiency and entropy generation is more significant than that of the second pass airflow ratio. The difference in air temperature through the collector shows an insignificant reduction, but the air pressure loss is only 50% compared with that of a traditional triple-pass solar air heater. Increasing the air flow ratios dramatically reduces entropy generation. Multi-objective optimization found a Reynolds number of 11,156 for both the airflow ratio of the second pass of 0.258 and airflow ratio of the third pass of 0.036 to be the an optimal value to achieve maximum thermohydraulic efficiency and minimum entropy generation.

Integrated emissions management for automotive painting operations

2001 ◽  
Vol 73 (8) ◽  
pp. 1277-1280 ◽  
Author(s):  
B. R. Kim ◽  
E. M. Kalis ◽  
J. A. Adams
Keyword(s):  
Pilot Scale ◽  
Activated Carbon Adsorption ◽  
Voc Removal ◽  
Carbon Adsorption ◽  
Voc Adsorption ◽  
Volatile Organic ◽  
Spray Booth ◽  
Order Of Magnitude ◽  
Paint Sludge ◽  
Economical Feasibility

An integrated scheme has been studied to reduce gaseous (volatile organic compounds [VOCs]), liquid (scrubber water), and solid (paint sludge) emissions from automotive painting operations by converting an existing spray-booth scrubber system to a bioreactor to capture and degrade VOCs and pyrolyzing paint sludge to produce an adsorbent. This paper describes the experimental results of 1) a pilot-scale study conducted at an assembly plant to evaluate the biological VOC removal using activated-sludge bioreactors and 2) a bench-scale study on VOC adsorption on paint-sludge adsorbents. The results indicate that the biological VOC removal is technically feasible (comparable VOC removal and less energy usage as compared to the widely used, vapor phase-activated carbon adsorption/thermal oxidation process) and economically feasible (one order of magnitude cheaper) and that paint-sludge adsorbents exhibited appreciable adsorption capacity. Implementation of the scheme requires more than technical and economical feasibility. The issues to be overcome include the inertia of past practices, overall systemic thinking, and moving targets (processes and regulations).

Entropy Analysis of Mixed Convective Condensation by Evaluating Fan Velocity With a New Approach

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Dipanka Bhuyan ◽  
Asis Giri ◽  
Pradip Lingfa
Keyword(s):  
Entropy Generation ◽  
Parallel Plate ◽  
Numerical Study ◽  
Channel Length ◽  
Entropy Analysis ◽  
New Approach ◽  
Central Focus ◽  
Plate Channel ◽  
Convective Condensation ◽  
Velocity Channel

Present paper conducts an extensive numerical study on entropy analysis of mixed convective condensation inside a vertical parallel plate channel. A new approach is proposed to separate pump velocity component/Reynolds number from inlet mixed convection velocity. Influence of inlet governing parameters on condensation heat and mass transfer at different inlet pressure, velocity, channel length, and width are widely studied. The central focus of this paper is to study entropy generation under mixed convective condensation. Variation of local as well as overall entropy generation and second law efficiency for different geometric and environmental conditions are presented. For effective condenser design, present study provides two important correlations of overall volumetric entropy generation due to thermal transport and overall volumetric entropy generation due to mass transport.

Economy of Efficient Air Preheating With Extraction Steam

1962 ◽  
Vol 84 (1) ◽  
pp. 1-6
Author(s):  
M. K. Drewry
Keyword(s):  
Flue Gas ◽  
Heat Rate ◽  
Heat Rejection ◽  
Air Heater ◽  
Fixed Charges ◽  
Rate Improvement

Two per cent heat rate improvement of a 275,000 kw unit results from efficient 2-stage steam air preheaters heating to 190 F with 5 F terminal temperature differences. Condenser heat rejection and turbine leaving losses are reduced substantially. Flue-gas losses are not increased. Air heater cleanliness is improved. Maintenance is reduced. Annual coal savings after fixed charges are one half of the net added investment.

Entropy Analysis of a R32/CO2 Cascade Refrigeration Cycle

2014 ◽  
Vol 672-674 ◽  
pp. 1676-1679
Author(s):  
Jian Xiao ◽  
Ying Fu Liu
Keyword(s):  
Entropy Generation ◽  
Temperature Difference ◽  
Design Parameters ◽  
Refrigeration Cycle ◽  
Total Entropy ◽  
Entropy Analysis ◽  
Minimization Method ◽  
Entropy Generation Minimization ◽  
Cascade Refrigeration

In order to study the performance of a R32/CO2 cascade refrigeration cycle, entropy generation minimization method was adopted to get the influence of some important operating and design parameters on the performance of the system and entropy generations of each component and the whole system, such as the evaporating temperature(Te), the condensing temperature(Tk) and the temperature difference in the cascade condenser(ΔT). The results indicate that there are a maximum COP and a minimum total entropy generation of the system at the optimal condensing temperature of the cascade condenser when Te, Tk and ΔT are constant. The total entropy generations of the throttling device, the condenser and the compressor of HTC, the cascade condenser and the compressor of LTC are above 80% of the total entropy generation of the whole system.

BLOCK ENTROPY ANALYSIS OF HEART RATE VARIABILITY SIGNALS

2006 ◽  
Vol 16 (07) ◽  
pp. 2093-2101 ◽  
Author(s):  
K. KARAMANOS ◽  
S. NIKOLOPOULOS ◽  
K. HIZANIDIS ◽  
G. MANIS ◽  
A. ALEXANDRIDI ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Heat Rate ◽  
Coarse Graining ◽  
Coarse Grained ◽  
Entropy Analysis ◽  
Data Set ◽  
Novel Approach ◽  
Data Files ◽  
Block Entropy ◽  
Artery Disease

In this paper we present a novel approach to the analysis of Heat Rate Variability (HRV) data, by coarse-graining analysis using the estimation of Block Entropies with the technique of lumping. HRV time series are generated from long recordings of Electrocardiograms (ECGs) and are then filtered in order to produce a coarse-grained symbolic dynamics. Block Entropy analysis is applied to these dynamics in order to examine its coarse-grained statistics. Our data set is comprised of two subsets, one of healthy subjects and another of Coronary Artery Disease (CAD) patients. It is found that Entropy analysis provides a quick and efficient tool for the differentiation of these series according to subject category. Healthy subjects provided more complex statistics compared to patients; specifically, the healthy data files provided higher values of block Entropies compared to patient ones. We also compare these results with the Correlation Dimension Estimation in order to establish coherency. We believe that this analysis may provide a useful statistical method towards the better understanding of the human cardiac system.

scholarly journals Entropy Analysis for MHD Generalised Couette Flow in a Composite Duct

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Paresh Vyas ◽  
Ashutosh Ranjan
Keyword(s):  
Entropy Generation ◽  
Finite Thickness ◽  
Bejan Number ◽  
Entropy Analysis ◽  
Clear Fluid ◽  
Electrically Conducting ◽  
Different Temperatures ◽  
Saturated Porous Layer ◽  
Porous Interface ◽  
Porous Strata

This paper presents entropy analysis of electrically conducting Newtonian fluid flow inside a horizontal composite duct. The upper impermeable wall of the duct moves with a uniform velocity while the lower wall is porous strata of finite thickness with impermeable bottom. The upper wall and the impermeable bottom are at constant temperature but at different temperatures. The duct is divided into two regions: Region I of clear fluid and Region II of fluid saturated porous layer. Momentum and thermal regimes for clear and porous regions are matched at clear fluid-porous interface by employing suitable matching conditions. The governing equations are solved analytically. Analytical solutions obtained for velocity and temperature are utilized to compute entropy generation. The effects of pertinent parameter on temperature distribution, entropy generation, and Bejan number are portrayed graphically and discussed.

Carbon Nanotube/Polyelectrolyte Composites as Novel Actuator Materials

2000 ◽  
Vol 633 ◽  
Author(s):  
Debjit Chattopadhyay ◽  
Izabela Galeska ◽  
Ray Baughman ◽  
Anwar Zakhidov ◽  
Fotios Papadimitrakopoulos
Keyword(s):  
Carbon Nanotube ◽  
Force Generation ◽  
Aqueous Electrolytes ◽  
Micellar Structure ◽  
First Case ◽  
Order Of Magnitude ◽  
Electrochemical Cycling ◽  
Power Densities ◽  
Technological Interest ◽  
Actuation Strain

AbstractMechanical actuators that simultaneously provide high power densities and large force generation capacities are of great scientific and technological interest. Recently single wall carbon nanotube (SWNT) papers (“bucky” papers) were shown to possess significant promise as electrochemical actuators. Embedding polyelectrolytes, like Nafion™, within the nanotube matrix has the potential to address the limitations of SWNT bundling and tube slippage thus increasing force generation. In this paper two types of Nafion/SWNT composite actuators have been investigated depending on the method of fabrication. In the first case, infiltration of Nafion within SWNT paper matrix was followed by annealing at 150°C to invert Nafion's micellar structure and render it insoluble. This has resulted in a substantially exfoliated layer morphology that causes a reduction in both conductivity and actuation strain (c.a. 0.03%). In the second case, slow casting of a methanolic suspension of Nafion and SWNT soot, followed by annealing at 150°C, resulted in a more homogeneous structure. This composite, upon electrochemical cycling between -1 and +1 V in aqueous electrolytes, exhibited actuation strains (as high as 0.43%). However, these higher strains are accompanied by an order of magnitude reduction in modulus largely due to Nafion swelling.

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