scholarly journals Thermodynamic Performance Investigation of Commercial R744 Booster Refrigeration Plants Based on Advanced Exergy Analysis

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 354 ◽  
Author(s):  
Paride Gullo ◽  
Armin Hafner ◽  
Krzysztof Banasiak
Keyword(s):  
Exergy Analysis ◽  
Performance Enhancement ◽  
Exergy Destruction ◽  
Outdoor Temperature ◽  
Food Retail ◽  
Destruction Rate ◽  
Performance Improvements ◽  
Refrigeration Unit ◽  
Thermodynamic Performance ◽  
The One

After the recent renewed interest in CO2 as the refrigerant (R744) for the food retail industry, many researchers have focused on the performance enhancement of the basic transcritical R744 supermarket refrigeration unit in warm climates. This task is generally fulfilled with the aid of energy-based methods. However, the implementation of an advanced exergy analysis is mandatory to properly evaluate the best strategies needing to be implemented to achieve the greatest thermodynamic performance improvements. Such an assessment, in fact, is widely recognized as the most powerful thermodynamic tool for this purpose. In this work, the advanced exergy analysis was applied to a conventional R744 booster supermarket refrigerating system at the outdoor temperature of 40 °C. The results obtained suggested the adoption of a more sophisticated layout, i.e., the one outfitted with the multi-ejector block. It was found that the multi-ejector supported CO2 system can reduce the total exergy destruction rate by about 39% in comparison with the conventional booster unit. Additionally, the total avoidable exergy destruction rate was decreased from 67.60 to 45.57 kW as well as the total unavoidable exergy destruction rate was brought from 42.67 down to 21.91 kW.

scholarly journals Conventional and Advanced Exergoeconomic Analysis of a Compound Ejector-Heat Pump for Simultaneous Cooling and Heating

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3511
Author(s):  
Ali Khalid Shaker Al-Sayyab ◽  
Joaquín Navarro-Esbrí ◽  
Victor Manuel Soto-Francés ◽  
Adrián Mota-Babiloni
Keyword(s):  
Heat Pump ◽  
Exergy Analysis ◽  
Waste Heat ◽  
District Heating ◽  
Cost Comparison ◽  
Exergy Destruction ◽  
Pump System ◽  
Heat Pump System ◽  
Destruction Rate ◽  
Exergoeconomic Analysis

This work focused on a compound PV/T waste heat driven ejector-heat pump system for simultaneous data centre cooling and waste heat recovery for district heating. The system uses PV/T waste heat as the generator’s heat source, acting with the vapour generated in an evaporative condenser as the ejector drive force. Conventional and advanced exergy and advanced exergoeconomic analyses are used to determine the cause and avoidable degree of the components’ exergy destruction rate and cost rates. Regarding the conventional exergy analysis for the whole system, the compressor represents the largest exergy destruction source of 26%. On the other hand, the generator shows the lowest sources (2%). The advanced exergy analysis indicates that 59.4% of the whole system thermodynamical inefficiencies can be avoided by further design optimisation. The compressor has the highest contribution to the destruction in the avoidable exergy destruction rate (21%), followed by the ejector (18%) and condenser (8%). Moreover, the advanced exergoeconomic results prove that 51% of the system costs are unavoidable. In system components cost comparison, the highest cost comes from the condenser, 30%. In the same context, the ejector has the lowest exergoeconomic factor, and it should be getting more attention to reduce the irreversibility by design improving. On the contrary, the evaporator has the highest exergoeconomic factor (94%).

scholarly journals Advanced Thermodynamic Analysis of a Transcritical R744 Booster Refrigerating Unit with Dedicated Mechanical Subcooling

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3058 ◽  
Author(s):  
Paride Gullo
Keyword(s):  
Low Temperature ◽  
Thermodynamic Analysis ◽  
Temperature Difference ◽  
Exergy Analysis ◽  
Refrigeration System ◽  
Outdoor Temperature ◽  
Medium Temperature ◽  
High Stage ◽  
Thermodynamic Performance ◽  
Priority Needs

In this work the thermodynamic performance of a transcritical R744 booster supermarket refrigeration system equipped with R290 dedicated mechanical subcooling (DMS) was exhaustively investigated with the aid of the advanced exergy analysis. The outcomes obtained suggested that improvement priority needs to be addressed to the manufacturing of more efficient high-stage (HS) compressors, followed by the enhancement of the gas cooler/condenser (GC), of the medium-temperature (MT) evaporators, of the R290 compressor, and of the low-temperature (LT) evaporators. These conclusions were different from those drawn by the application of the conventional exergy assessment. Additionally, it was found that GC can be enhanced mainly by reducing the irreversibilities owing to the simultaneous interaction among the components. The R290 compressor would also have significantly benefitted from the adoption of such measures, as half of its avoidable irreversibilities were exogenous. Unlike the aforementioned components, all the evaporators were improvable uniquely by decreasing their temperature difference. Finally, the approach temperature of GC and the outdoor temperature were found to have a noteworthy impact on the avoidable irreversibilities of the investigated solution.

Performance Enhancement in LICL–H2O and LIBR–H2O Absorption Cooling Systems Through an Advanced Exergy Analysis

2021 ◽  
pp. 2150007
Author(s):  
Parth Mody ◽  
Jatin Patel ◽  
Nishant Modi ◽  
Bhargav Pandya
Keyword(s):  
Exergy Analysis ◽  
Research Study ◽  
Performance Enhancement ◽  
Lithium Bromide ◽  
Second Law Of Thermodynamics ◽  
Cooling Systems ◽  
Absorption Cooling ◽  
Thermodynamic Performance ◽  
System Components ◽  
Chloride Water

This research study compares the thermodynamic performance of 10[Formula: see text]kW lithium chloride–water (LiCl–H2O) and lithium bromide–water (LiBr–H2O) absorption cooling systems through first and second law of thermodynamics. Further, the exergy degradations happening in each component have been split into unavoidable and avoidable exergy degradations as well as endogenous and exogenous exergy degradations through advanced exergy analysis. Pressure–temperature–concentration ([Formula: see text]–[Formula: see text]–[Formula: see text] diagrams are drafted to clarify the real, ideal, and unavoidable cycles for LiCl–H2O and LiBr–H2O absorption cycles. Moreover, this paper exhibits the sensitivity of various system components towards the generator, condenser, and absorber temperature for both pairs. Energetic observation proves that LiCl–H2O pair is 10% more efficient as compared to LiBr–H2O pair. Exergetically, LiBr–H2O cycle struggles with additional (nearly 13.45%) exergy destruction than LiCl–H2O cycle. The major contribution (around 70% to 80%) of irreversibility comes from the generator and absorber. Comprehensively, the parametric partitions of irreversibility rate in each component provide broad indications to prioritize the system components for enhancements.

scholarly journals Comparison of Exergy and Advanced Exergy Analysis in Three Different Organic Rankine Cycles

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 586 ◽  
Author(s):  
Shahab Yousefizadeh Dibazar ◽  
Gholamreza Salehi ◽  
Afshin Davarpanah
Keyword(s):  
Exergy Analysis ◽  
Feed Water ◽  
Exergy Destruction ◽  
Real Potential ◽  
Water Heaters ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Organic Rankine Cycles ◽  
Advanced Analysis ◽  
The One

Three types of organic Rankine cycles (ORCs): basic ORC (BORC), ORC with single regeneration (SRORC) and ORC with double regeneration (DRORC) under the same heat source have been simulated in this study. In the following, the energy and exergy analysis and the advanced exergy analysis of these three cycles have been performed and compared. With a conventional exergy analysis, researchers can just evaluate the performance of components separately to find the one with the highest amount of exergy destruction. Advanced analysis divides the exergy destruction rate into unavoidable and avoidable, as well as endogenous and exogenous, parts. This helps designers find more data about the effect of each component on other components and the real potential of each component to improve its efficiency. The results of the advanced exergy analysis illustrate that regenerative ORCs have high potential for reducing irreversibilities compared with BORC. Total exergy destruction rates of 4.13 kW (47%) and 5.25 kW (45%) happen in avoidable/endogenous parts for SRORC and DRORC, respectively. Additionally, from an advanced exergy analysis viewpoint, the priority of improvement for system components is given to turbines, evaporators, condensers and feed-water heaters, respectively.

scholarly journals Evaluation of Two-Column Air Separation Processes Based on Exergy Analysis

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6361
Author(s):  
Muhammad Haris Hamayun ◽  
Naveed Ramzan ◽  
Murid Hussain ◽  
Muhammad Faheem
Keyword(s):  
Large Scale ◽  
Exergy Analysis ◽  
Separation Process ◽  
Air Separation ◽  
Scale Production ◽  
Exergy Destruction ◽  
Separation Processes ◽  
Distillation Columns ◽  
Operational Conditions ◽  
Destruction Rate

Cryogenic air separation processes are widely used for the large-scale production of nitrogen and oxygen. The most widely used design for this process involves two distillation columns operating at different pressures. This work focuses on the selection of suitable cryogenic air separation process by evaluating seven alternative designs of the two-column air separation process based on detailed exergy analysis. The feed conditions (500 tons/h, and 50% relative humidity of air), product purities (99 mole% for both nitrogen and oxygen), and operational conditions (pressures of both distillation columns) are kept same in all designs. The two cryogenic distillation columns in each configuration are heat-integrated to eliminate the need for external utilities. Steady-state simulation results are used to calculate the exergy efficiency (%) of each equipment as well as its contribution toward the overall exergy destruction rate (kW) of the process. The results show that the compression section is a major source of exergy destruction, followed by the low-pressure column, and the multi-stream heat exchanger. A Petlyuk-like configuration, labeled as C1, provides the lowest exergy destruction rate.

Avoidable and Unavoidable Exergetic Destruction Analysis of a Nitric Acid Production Plant

2018 ◽  
Author(s):  
J. Fajardo ◽  
H. Valle ◽  
A. Buelvas
Keyword(s):  
Nitric Acid ◽  
Catalytic Oxidation ◽  
Acid Production ◽  
Exergy Analysis ◽  
Catalytic Converter ◽  
Production Plant ◽  
Exergy Destruction ◽  
Modern Times ◽  
Destruction Rate ◽  
Nitrous Gases

Exergy analysis for Nitric acid production plants are very few and many are outdated. This study aims to support existing scientific studies and incite new investigations of exergy analysis in modern times. An advanced exergy analysis was applied to a production plant with a capacity to process 350 tons/day of nitric acid at a concentration of 55%. The catalytic oxidation of ammonia, condensation and absorption of nitrous gases are considered as the principal process in the nitric acid production. The total destroyed exergy was 46772,55 KW. The component with the greatest impact was the catalytic converter, which presented 75.1% of the total avoidable exergy destruction rate of the plant. These findings are relevant as they can potentially reduce costs of nitric acid production.

The Future of Plasma-Based Surface Engineering Techniques in Tribology (Keynote)

2005 ◽  
Author(s):  
Allan Matthews ◽  
Adrian Leyland
Keyword(s):  
Surface Engineering ◽  
Performance Enhancement ◽  
Bulk Material ◽  
Cost Savings ◽  
Cost Effective ◽  
Ceramic Coatings ◽  
Performance Improvements ◽  
Treatment Techniques ◽  
Wide Range ◽  
Macro Scale

Over the past twenty years or so, there have been major steps forward both in the understanding of tribological mechanisms and in the development of new coating and treatment techniques to better “engineer” surfaces to achieve reductions in wear and friction. Particularly in the coatings tribology field, improved techniques and theories which enable us to study and understand the mechanisms occurring at the “nano”, “micro” and “macro” scale have allowed considerable progress to be made in (for example) understanding contact mechanisms and the influence of “third bodies” [1–5]. Over the same period, we have seen the emergence of the discipline which we now call “Surface Engineering”, by which, ideally, a bulk material (the ‘substrate’) and a coating are combined in a way that provides a cost-effective performance enhancement of which neither would be capable without the presence of the other. It is probably fair to say that the emergence and recognition of Surface Engineering as a field in its own right has been driven largely by the availability of “plasma”-based coating and treatment processes, which can provide surface properties which were previously unachievable. In particular, plasma-assisted (PA) physical vapour deposition (PVD) techniques, allowing wear-resistant ceramic thin films such as titanium nitride (TiN) to be deposited on a wide range of industrial tooling, gave a step-change in industrial productivity and manufactured product quality, and caught the attention of engineers due to the remarkable cost savings and performance improvements obtained. Subsequently, so-called 2nd- and 3rd-generation ceramic coatings (with multilayered or nanocomposite structures) have recently been developed [6–9], to further extend tool performance — the objective typically being to increase coating hardness further, or extend hardness capabilities to higher temperatures.

Energy and Exergy Analysis of the Teduction Zone in a Downdraft (Biomass) Gasifier

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Avdhesh Kr. Sharma ◽  
Raj Kumar Singh
Keyword(s):  
Kinetic Models ◽  
Exergy Analysis ◽  
Internal Heat ◽  
Calorific Value ◽  
Exergy Destruction ◽  
Reduction Zone ◽  
Reactor Performance ◽  
General Validity ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

This article describes the energy and exergy analysis of the reduction zone in a downdraft biomass gasifier. A simplistic formulation for describing the pyrolysis and oxidation of these products has been presented for initialization. Equilibrium and kinetic models are used to predict the reduction products leaving the reduction zone and thus the 1st law efficiency. In the reduction zone, exergy destruction due to chemical, physical, compositional, internal heat transfer and heat loss to the surrounding has been quantified to describe 2nd law efficiency. The comparison of equilibrium and kinetic models is carried out with experimental data for general validity. Parametric analysis of char bed length and inflow temperature on gas composition, un-converted char, exergy destruction, 1st law and the 2nd law efficiency has also been carried out. Simulation results identified a critical char bed length (where all char gets consumed) for a given feedstock, which depends on residence time and reaction temperature in the reduction zone. Near critical char bed length, predictions show high calorific value of gas with relatively less exergy destruction and thus optimum reactor performance. The accuracy of the prediction depends on the validity of initial input conditions.

Sign in / Sign up

Export Citation Format

Share Document