scholarly journals Application of the Second Law of Thermodynamics in Brazilian Residential Appliances towards a Rational Use of Energy

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 616 ◽  
Author(s):  
Carlos Eduardo Keutenedjian Mady ◽  
Clara Reis Pinto ◽  
Marina Torelli Reis Martins Pereira
Keyword(s):  
Energy Efficiency ◽  
Natural Resources ◽  
Air Conditioning ◽  
Second Law Of Thermodynamics ◽  
Exergy Efficiency ◽  
Second Law ◽  
Vapor Compression ◽  
Energy Matrix ◽  
Additional Information

This article proposes the utilization of the concepts of destroyed exergy and exergy efficiency for equipment and process performance indicators that are related to the current energy planning scenario in Brazil, more specifically with energy-efficiency labelling. Several indicators associated with these concepts are discussed, including one national program that is based on labeling the energy efficiency of several residential, commercial and industrial appliances. The grades are indicated in the equipment using values from A to G. This labeling system is useful for discriminating similar technologies used for the same function; nevertheless produced by different enterprises. For this complementary analysis, two types of refrigeration methods were compared, absorption and vapor compression; however, these energy indexes alone are not sufficient parameters to select among these two technologies, because their performance indexes definition are different. To address this, our research considers the second law of thermodynamics through exergy analysis as a proper sub-index to obtain a systematic comparison between these various indicators. It is significant to highlight that seldom research studies addressed to this problem so explicitly, in an actual governmental working solution, aiming at discussing to the society the advantage of the usage of the “quality of the energy” as a complementary index to governmental and personal choices. Results indicate that it is possible to use the destroyed exergy and exergy efficiency to help select the technology that better utilizes natural resources, considering the energy matrix of the country. Appliances for water heating and air conditioning were compared from energy and exergy viewpoint, where the last gave additional information about the quality of energy conversion process, giving a completely different trend from the energy analysis alone, without the necessity to think about the energy matrix. Later this issue is addressed from both points of view. Future studies may suggest an exergy based index. The energy efficiency suggests that electrical shower (values higher than 95%) are better than gas water heaters (83% ) in using natural resources, whereas the exergy efficiency shares similar magnitudes (about 3%). A related pattern is shown for the theoretical air conditioning systems. The vapor compression systems have an energy index higher than 3, and absorption systems lower than 1. For these circumstances, the exergy efficiency shows figures nearby 30%.

Thermoeconomic Indicators of Air Conditioning in a River Ship to Change the Configuration of Their Thermal Insulation

2014 ◽  
Author(s):  
J. Fajardo ◽  
B. Sarria ◽  
M. Alvarez Guerra
Keyword(s):  
System Performance ◽  
Heat Load ◽  
Air Conditioning ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Cooling Load ◽  
Air Conditioning System ◽  
Object Of Study ◽  
The Cost

This work has as object of study the energy of a river ship air conditioning system performance, using fiberglass, polyurethane or rockwool as insulation. Thermoeconomics Indicators based on second law of thermodynamics which take into account the quality of the energy and the cost of the exergy were used for research. It was observed that: (i) by increasing the thickness of the insulation the irreversibilities decreased, (ii) increases in the destroyed exergy increased generation of cooling load costs and (iii) costs per unit of exergy of heat load and area for the generation of cooling load and for investment in exergetic insulation, were minors for polyurethane.

Thermodynamic Analysis of a Multi-Fueled Single Cylinder SI Engine

2011 ◽  
Author(s):  
M. Z. Haq ◽  
M. R. Mohiuddin
Keyword(s):  
Thermodynamic Analysis ◽  
Chemical Properties ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Si Engine ◽  
Gaseous Species ◽  
Single Cylinder ◽  
Engine Cylinder ◽  
Si Engines

The paper presents a thermodynamic analysis of a single cylinder four-stroke spark-ignition (SI) engine fuelled by four fuels namely iso-octane, methane, methanol and hydrogen. In SI engines, due to phenomena like ignition delay and finite flame speed manifested by the fuels, the heat addition process is not instantaneous, and hence ‘Weibe function’ is used to address the realistic heat release scenario of the engine. Empirical correlations are used to predict the heat loss from the engine cylinder. Physical states and chemical properties of gaseous species present inside the cylinder are determined using first and second law of thermodynamics, chemical kinetics, JANAF thermodynamic data-base and NASA polynomials. The model is implemented in FORTRAN 95 using standard numerical routines and some simulation results are validated against data available in literature. The second law of thermodynamics is applied to estimate the change of exergy i.e. the work potential or quality of the in-cylinder mixture undergoing various phases to complete the cycle. Results indicate that, around 4 to 24% of exergy initially possessed by the in-cylinder mixture is reduced during combustion and about 26 to 42% is left unused and exhausted to the atmosphere.

scholarly journals From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 361 ◽  
Author(s):  
Giedrė Streckienė ◽  
Vytautas Martinaitis ◽  
Juozas Bielskus
Keyword(s):  
Heat Pump ◽  
Entropy Generation ◽  
Energy Demand ◽  
Dynamic Modelling ◽  
Second Law Of Thermodynamics ◽  
Exergy Efficiency ◽  
Second Law ◽  
Air Handling Unit ◽  
Individual Character ◽  
Environment Temperature

The continuous energy transformation processes in heating, ventilation, and air conditioning systems of buildings are responsible for 36% of global final energy consumption. Tighter thermal insulation requirements for buildings have significantly reduced heat transfer losses. Unfortunately, this has little effect on energy demand for ventilation. On the basis of the First and the Second Law of Thermodynamics, the concepts of entropy and exergy are applied to the analysis of ventilation air handling unit (AHU) with a heat pump, in this paper. This study aims to develop a consistent approach for this purpose, taking into account the variations of reference temperature and temperatures of working fluids. An analytical investigation on entropy generation and exergy analysis are used, when exergy is determined by calculating coenthalpies and evaluating exergy flows and their directions. The results show that each component of the AHU has its individual character of generated entropy, destroyed exergy, and exergy efficiency variation. However, the evaporator of the heat pump and fans have unabated quantities of exergy destruction. The exergy efficiency of AHU decreases from 45–55% to 12–15% when outdoor air temperature is within the range of −30 to +10 °C, respectively. This helps to determine the conditions and components of improving the exergy efficiency of the AHU at variable real-world local climate conditions. The presented methodological approach could be used in the dynamic modelling software and contribute to a wider application of the Second Law of Thermodynamics in practice.

scholarly journals Analysis of supplemental dehumidification for increased energy efficiency of shoulder seasons based on climate change predictions in Austin Texas

2021 ◽  
Vol 2042 (1) ◽  
pp. 012182
Author(s):  
B Marshall ◽  
J Felkner ◽  
Z Nagy
Keyword(s):  
Climate Change ◽  
Energy Efficiency ◽  
Potential Energy ◽  
Energy Efficient ◽  
Air Conditioning ◽  
Energy Savings ◽  
Vapor Compression ◽  
Compression System ◽  
Vapor Compression System ◽  
American Society

Abstract This research project compared a standard vapor compression system and a standard desiccant dehumidification system with heat wheel to determine if there was some potential energy savings for “shoulder season” hours in Austin Texas. “Shoulder season” hours as defined in the paper are hours during which the dry bulb temperature falls within the American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) comfort bound but the humidity is above the comfortable humidity point. These hours are normally addressed with vapor compression systems which dehumidify by cooling the air under the comfort setpoint to dehumidify, which is wasteful of energy. The study found that for these shoulder season hours a desiccant dehumidification system was around 4.5 times more energy efficient at reaching comfort setpoints if free heating was used for drying the desiccant.

scholarly journals An Energy Efficiency Index Formation and Analysis of Integrated Energy System Based on Exergy Efficiency

2021 ◽  
Vol 9 ◽  
Author(s):  
Huiling Su ◽  
Qifeng Huang ◽  
Zhongdong Wang
Keyword(s):  
Energy Efficiency ◽  
Evaluation Model ◽  
Second Law Of Thermodynamics ◽  
Energy System ◽  
Efficiency Index ◽  
Exergy Efficiency ◽  
Energy Utilization ◽  
Utilization Efficiency ◽  
Efficiency Evaluation ◽  
Integrated Energy System

In the context of the energy crisis and environmental deterioration, the integrated energy system (IES) based on multi-energy complementarity and cascaded utilization of energy is considered as an effective way to solve these problems. Due to the different energy forms and the various characteristics in the IES, the coupling relationships among various energy forms are complicated which enlarges the difficulty of energy efficiency evaluation of the IES. In order to flexibly analyze the energy efficiency of the IES, an operation efficiency evaluation model for the IES is established. First, energy utilization efficiency (EUE) and exergy efficiency (EXE) are proposed based on the first/second law of thermodynamics. Second, the energy efficiency models for five processes and four subsystems of the IES are formed. Lastly, an actual commercial-industrial park with integrated energy is employed to validate the proposed method.

Optimization of turbojet engine cycle with dual-purpose PSO algorithm

2019 ◽  
Vol 20 (6) ◽  
pp. 604 ◽  
Author(s):  
M.R. Ahadi Nasab ◽  
M.A. Ehyaei
Keyword(s):  
Entropy Production ◽  
Pressure Ratio ◽  
Second Law Of Thermodynamics ◽  
Pso Algorithm ◽  
Optimization Method ◽  
Exergy Efficiency ◽  
Second Law ◽  
Turbine Efficiency ◽  
Turbojet Engine ◽  
Compressor Pressure Ratio

In this article, the J85-GE-21 turbojet engine for an altitude of 1000–8000 m, with the speed of 200 m/s and at 10, 20, and 40 °C, was provided, and then, based on the objective functions, the above system was optimized using particle swarm optimization method. For the purpose of optimization, the Mach number, compressor efficiency, turbine efficiency, nozzle efficiency, and compressor pressure ratio were assumed to be in the range of 0.6–1.4, 0.8–0.95, 0.8–0.95, 0.8–0.95, and 7–10, respectively. The highest exergy efficiency of 73.1% for different components of the engine at sea level and speed of 200 m/s belonged to the diffuser. Second and third to it were nozzle and combustion chamber with 68.6 and 51.5%, respectively. The lowest exergy efficiency of 4% belonged to the compressor, and the second to it was the afterburner with 11.6%. Also, the values of entropy production and efficiency of the second law of thermodynamics were 1176.99 and 479 K/W, respectively, prior to optimization, which were respectively changed to 1129 and 51.4 K/W postoptimization. Obviously, the entropy production is reduced, while the efficiency of the second law of thermodynamics is increased.

Exergy Analysis of Transcritical Regenerative Organic Rankine Cycle Using Isobutane

2013 ◽  
Vol 442 ◽  
pp. 183-186
Author(s):  
Kyoung Hoon Kim
Keyword(s):  
Exergy Analysis ◽  
Organic Rankine Cycle ◽  
Internal Heat ◽  
Second Law Of Thermodynamics ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Second Law ◽  
Source Temperature ◽  
Internal Heat Exchanger ◽  
Maximum Value

Exergy analysis is performed for transcritical Organic Rankine Cycle (ORC) with internal heat exchanger based on the second law of thermodynamics. Effects of source temperature as well as turbine inlet pressure (TIP) are investigated on the exergy destructions (or anergies) of the system as well as exergy efficiency. Results show that irreversibility of the system decreases with increasing TIP or decreasing source temperature. Exergy efficiency decreases with increasing source temperature; however has a maximum value with respect to TIP.

scholarly journals ‘The optimization of a jet turbojet engine by PSO and searching algorithms’

2019 ◽  
Author(s):  
Sorush Niknamian
Keyword(s):  
Sea Level ◽  
Exergy Analysis ◽  
Pressure Ratio ◽  
Second Law Of Thermodynamics ◽  
Computer Code ◽  
Exergy Efficiency ◽  
Second Law ◽  
Combustion Chambers ◽  
Software Environment ◽  
Turbojet Engine

The turbojet engine operates on the ideal Brayton cycle (gas turbine) and consists of six main parts: diffusers, compressors, combustion chambers, turbines, afterburners and nozzles. Using computer code writing in MATLAB software environment, exergy analysis on all selected turbojet engine components, exergy analysis on J85-GE-21 turbojet engine for selective height of 10008000 meters above sea level at speeds of 200 m/s and temperatures of 10, 20 and 40 ° C have been provided and then, according to the system functions, the system is optimized based on the PSO method. For the purpose of optimization, variables of Mach number, efficiency of the compressor, turbine, nozzle and compressor pressure ratio are considered in the range of 0.6 to 1.4, 0.8 to 0.95, 0.8 to 0.95 and 7 to 10, respectively. The highest exergy efficiency of different parts of the engine at sea level with an inlet air velocity of 200 m/s corresponds to a diffuser with 73.1%. Then, the nozzle and combustion chamber are respectively 68.6% and 51.5%. The lowest exergy efficiency is related to compressor with 4%. After that, the afterburner is ranked second with 11.6%. Also, the values of entropy produced and the efficiency of the second law before optimization were 1176.99 and 479 w/k respectively and the same values after optimization were 1129 and 51.4 w/k respectively which is identified. After the optimization process, the amount of entropy produced is reduced and the efficiency of the second law of thermodynamics has increased.

scholarly journals Investigating the Effects of Parametric Variation over Performance of Boiler-Turbine Cycle

2021 ◽  
Vol 9 (8) ◽  
pp. 2620-2628
Author(s):  
Dr. S. S. L. Patel
Keyword(s):  
Adverse Effect ◽  
Energy Efficiency ◽  
Energy Loss ◽  
Ambient Temperature ◽  
Flue Gas ◽  
Environmental Temperature ◽  
Exergy Efficiency ◽  
Plant Performance ◽  
Second Law ◽  
Gas Temperature

Abstract: In this paper, the effects of variation in ambient temperature, flue gas temperature and condenser pressure over performance of boiler and turbine cycle is presented. The study is carried out with EES software. The change in ambient temperature is seriously deteriorating the boiler exergetic performance as its exergy efficiency reduces by 2.5% with increase in environmental temperature from 27C to 45C while the boiler total energy loss reduces almost 1% for same increase in ambient temperature. The turbine second law efficiency is affected slightly by ambient temperature. Increase in temperature of exhaust flue gas has adverse effect over boiler energy efficiency, which reduces by almost 1% with flue gas temperature variation from 110C to 130C. The increase in condenser pressure is reducing the turbine energy efficiency to more than 3% with variation from 0.05bar to 0.3bar. Condenser exergy efficiency is decreasing sharply with increase in its pressure. The effect of variation in condenser pressure over net output of the boiler-turbine cycle has also been studied and it is found to be decreasing with increase in condenser pressure. Keyword: Ambient temperature, Boiler-turbine cycle, Condenser pressure, Flue gas, Plant performance.

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