scholarly journals Exergy Analysis of Fluidized Desiccant Cooling System

Entropy ◽  
2019 ◽  
Vol 21 (8) ◽  
pp. 757 ◽  
Author(s):  
Zbigniew Rogala ◽  
Piotr Kolasiński
Keyword(s):  
Exergy Analysis ◽  
Cooling System ◽  
The Other ◽  
Coefficient Of Performance ◽  
Exergy Destruction ◽  
Regenerative Heat ◽  
Design And Implementation ◽  
Air Cooler ◽  
Evaporative Cooler ◽  
Direct Evaporative Cooler

One of the main challenges in the design and implementation of fluidized desiccant cooling (FDC) systems is increasing their low COP (coefficient of performance). Exergy analysis is one of the tools especially suitable for improvement and optimization of FDC systems. The improvement of performance is impossible as long as the main sources of exergy destruction are not identified and evaluated. In this paper, the exergy analysis was applied in order to identify these components and processes of the FDC system that are mainly responsible for exergy destruction. Moreover, the exergy efficiency of a simple fluidized desiccant cooler was determined. The results showed that fluidized beds and regenerative heat exchanger were the main exergy destruction sources with a 32% and 18% share of total exergy destruction, respectively. On the other hand, the direct evaporative cooler and air cooler placed after the desorbing fluidized bed were characterized by the lowest exergy efficiencies. This work contributes to better understanding of FDC operation principles and improvement of the performance of FDC technology.

Exergy Analysis of an Ejector Cooling System by Modified Gouy–Stodola Equation

2021 ◽  
Vol 29 (03) ◽  
Author(s):  
Gulshan Sachdeva ◽  
Bharat Sharma
Keyword(s):  
Exergy Analysis ◽  
Cooling System ◽  
Exergy Loss ◽  
Coefficient Of Performance ◽  
Exergy Destruction ◽  
Evaporator Temperature ◽  
Structural Bond ◽  
Operating Variables ◽  
Exergy Method

In this paper, exergy destruction analysis of a heat-assisted ejector cooling system has been carried out using a modified Gouy–Stodola equation. The modified Gouy–Stodola equation provides a more accurate and realistic irreversibility analysis of the system than the conventional Gouy–Stodola formulation. The coefficient of structural bond (CSB) analysis has also been executed to find the component whose operating variables affect the system’s total irreversibility at the most. Exergy analysis revealed that the maximum exergy loss happens in the ejector followed by the generator and condenser. The model predicted 40.84% of total irreversibility in the ejector at the designed conditions. However, total exergy destruction is found to be the most sensitive to the evaporator temperature. The CSB value of 12.97 is obtained in the evaporator using the modified exergy method. The generator appears to be the second sensitive component with the CSB value of 2.42, followed by the condenser with the CSB value of 1.628. The coefficient of performance of the system is found to be 0.18 at the designed conditions. The refrigerant R1234yf is considered in the system.

scholarly journals Performance Evaluation of a Gravity-Assisted Heat Pipe-Based Indirect Evaporative Cooler

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 200 ◽  
Author(s):  
Krzysztof Rajski ◽  
Jan Danielewicz ◽  
Ewa Brychcy
Keyword(s):  
Mathematical Model ◽  
Heat Pipe ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Mass Transfer Processes ◽  
Air Cooler ◽  
Evaporative Cooler ◽  
The Mathematical Model ◽  
Further Development

In the present work, the effects of different operating parameters on the performance of a gravity-assisted heat pipe-based indirect evaporative cooler (GAHP-based IEC) were investigated. The aim of the theoretical study is to evaluate accurately the cooling performance indicators, such as the coefficient of performance (COP), wet bulb effectiveness, and cooling capacity. To predict the effectiveness of the air cooler under a variety of conditions, the comprehensive calculation method was adopted. A mathematical model was developed to simulate numerically the heat and mass transfer processes. The mathematical model was validated adequately using experimental data from the literature. Based on the conducted numerical simulations, the most favorable ranges of operating conditions for the GAHP-based IEC were established. Moreover, the conducted studies could contribute to the further development of novel evaporative cooling systems employing gravity-assisted heat pipes as efficient equipment for transferring heat.

scholarly journals Exergy Analysis of Adiabatic Liquid Air Energy Storage (A-LAES) System Based on Linde–Hampson Cycle

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 945
Author(s):  
Lukasz Szablowski ◽  
Piotr Krawczyk ◽  
Marcin Wolowicz
Keyword(s):  
Energy Storage ◽  
Research And Development ◽  
Large Scale ◽  
Exergy Analysis ◽  
The Other ◽  
Compressed Air ◽  
Exergy Destruction ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Discharge Pressure

Efficiently storing energy on a large scale poses a major challenge and one that is growing in importance with the increasing share of renewables in the energy mix. The only options at present are either pumped hydro or compressed air storage. One novel alternative is to store energy using liquid air, but this technology is not yet fully mature and requires substantial research and development, including in-depth energy and exergy analysis. This paper presents an exergy analysis of the Adiabatic Liquid Air Energy Storage (A-LAES) system based on the Linde–Hampson cycle. The exergy analysis was carried out for four cases with different parameters, in particular the discharge pressure of the air at the inlet of the turbine (20, 40, 100, 150 bar). The results of the analysis show that the greatest exergy destruction can be observed in the air evaporator and in the Joule–Thompson valve. In the case of air evaporator, the destruction of exergy is greatest for the lowest discharge pressure, i.e., 20 bar, and reaches over 118 MWh/cycle. It decreases with increasing discharge pressure, down to approximately 24 MWh/cycle for 150 bar, which is caused by a decrease in the heat of vaporization of air. In the case of Joule–Thompson valve, the changes are reversed. The highest destruction of exergy is observed for the highest considered discharge pressure (150 bar) and amounts to over 183 MWh/cycle. It decreases as pressure is lowered to 57.5 MWh/cycle for 20 bar. The other components of the system do not show exergy destruction greater than approximately 50 MWh/cycle for all considered pressures. Specific liquefaction work of the system ranged from 0.189 kWh/kgLA to 0.295 kWh/kgLA and the efficiency from 44.61% to 55.18%.

Detailed Energy and Exergy Analysis for a Solar Lithium Bromide Absorption Chiller and a Conventional Electric Chiller (R134a)

2011 ◽  
Author(s):  
Yang Hu ◽  
Laura A. Schaefer ◽  
Volker Hartkopf
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Cooling System ◽  
Residential Buildings ◽  
Lithium Bromide ◽  
Building Energy ◽  
Hot Water ◽  
Exergy Destruction ◽  
Absorption Chiller ◽  
Two Stage

The Building Energy Data Book (2009) [1] shows that commercial and residential buildings in the U.S. consume 39.9% of the primary energy and contribute 39% of the total CO2 emissions. In the operation of buildings, 41.8% of building energy consumption is provided for building cooling, heating, domestic hot water, and ventilation for commercial buildings, while in residential buildings, this percentage increases to 58%. In energy system analysis, the energy approach is the traditional method of assessing the way energy is used in an operation. However, an energy balance provides no information on the degradation of energy or resources during a process. The concept of exergy combines the first law and second law of thermodynamics. The exergy analysis clearly quantifies the energy quality match between the supply and demand sides, and also addresses the exergy destruction (entropy generation) in each component. In this paper, a solar thermal driven absorption cooling system was analyzed for providing cooling to a building, the Intelligent Workplace South Zone at Carnegie Mellon University. The system includes a 52 m2 parabolic trough solar collector, and a 16 kW (4 tons) two-stage lithium bromide absorption chiller. The energy model and newly developed two-stage lithium bromide absorption chiller are programmed and integrated in Engineering Equation Solver (EES). The temperature, enthalpy, entropy, mass flow rate, and mass fraction of lithium bromide in the solar absorption system were presented in steady state operation. The exergy destruction in each component is calculated. The exergy destructions for the solar collector, generator, absorber, and heat exchangers were significantly higher than those in evaporator, condenser and expansion valves, the overall energy and exegetic efficiency were also calculated.

Exergy Analysis of a Solar-Driven Dual Parallel-Connected Ejector Refrigeration System

2016 ◽  
Vol 839 ◽  
pp. 100-106
Author(s):  
Yahya Gaafar Abdella Mohammed ◽  
Tawat Suriwong ◽  
Sakda Somkun ◽  
Timeyo Mkamanga Maroyi
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Saturated Steam ◽  
Working Fluid ◽  
Electric Heater ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
Exergetic Efficiency

Nowadays, developing solar cooling technologies, especially ejector refrigeration system, has become preferable to scientific researchers. Exergy analysis is a technique in which the basis of evaluation of thermodynamic losses follows the second law rather than the first law of thermodynamics. An experimental exergy analysis of a solar-driven dual parallel-connected ejector (DPE) refrigeration system was conducted using water as working fluid. Saturated steam with 2 bar and 120oC was provided by heat–pipe evacuated tube solar collector with an assistant of an electric heater. The saturated stream was used as a motive flow for the ejectors. The exergy destruction and exergetic efficiency of the main components of the DPE refrigeration system were determined and compared with those when using a single ejector (SE) under same operating conditions. It was found that the most irreversibilities of both systems occurred at the solar collector, electric boiler and ejectors, respectively. Also, the total irreversibility (Exergy destruction) of the system when using DPE was lower than using a SE. In additions, the exergetic efficiency of the ejector, evaporator, and overall system when using DPE were increased by 21%, 10%, and 27%, respectively. The system thermal ratio (STR) and coefficient of performance (COP) of the system using DPE compared with SE were increased by 20% and 23%, respectively.

Exergetic Analysis and Assessment of Industrial Furnaces

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Hakan Caliskan ◽  
Arif Hepbasli
Keyword(s):  
Maximum Rate ◽  
Exergy Analysis ◽  
Heating Furnace ◽  
The Other ◽  
Flue Gases ◽  
Exergy Destruction ◽  
Furnace Temperature ◽  
Radiant Tube ◽  
Exergetic Analysis ◽  
Exergy Losses

This study presents exergy analysis of a natural gas-fired radiant tube-heating furnace. In the analysis, actual data over a test period of 3 h were used. Exergy efficiencies, destructions, losses, and entropy generation of the furnace were determined. For an average furnace temperature of 666.6°C, average exergy efficiency value was calculated to be 9.6%. The exergy destruction rate was obtained to be 5.34 kW while exergy rates of the flue gases, exergy losses, and exergy steel were 12.53 kW, 44.28 kW, and 6.6 kW, respectively. On the other hand, the exergy rate of the product (steel) was found to be between 4.61 kW and 9.88 kW over the 15 min test periods, and it reached a maximum rate at the end of the second hour.

Enthalpy and Exergy Analysis of Domestic Desiccant Air Conditioner With Cooling Dehumidification and Heating Humidification Using Process Simulator

2011 ◽  
Author(s):  
Shun Hirano ◽  
Yoshinori Hisazumi ◽  
Tsukasa Hori ◽  
Tsutomu Wakabayashi ◽  
Akira Kishimoto ◽  
...  
Keyword(s):  
Exergy Analysis ◽  
Cooling Capacity ◽  
Air Conditioner ◽  
Air Conditioners ◽  
Evaporative Cooler ◽  
Humidified Air ◽  
Process Simulator ◽  
Exergy Analyses ◽  
Direct Evaporative Cooler ◽  
Exergy Losses

To popularize the use of desiccant air conditioners in residences, a system that can supply cooled and dried air in summer as well as heated and humidified air in winter is proposed. An evaporative cooler that affords an increase in cooling capacity and the amount of humidification is used in this system. The results of the enthalpy and exergy analyses, performed using a process simulator, showed that significant exergy losses occurred at the blower, heater, and desiccant rotor. In addition, exergy loss occurred at the direct evaporative cooler in heating humidification. Furthermore, it was found that there exists an optimal water temperature that yields peak exergy efficiency from the desiccant rotor.

Exergetic Analyses of a Particular Absorption Cooling System

2012 ◽  
Vol 326-328 ◽  
pp. 641-646 ◽  
Author(s):  
Nahla Bouaziz ◽  
D. Lounissi ◽  
Lakdar Kairouani ◽  
M. El Ganaoui
Keyword(s):  
Exergy Analysis ◽  
Cooling System ◽  
Working Fluid ◽  
Exergy Destruction ◽  
Mass Energy ◽  
Intermediate Pressure ◽  
Absorption Cooling ◽  
Energy And Exergy ◽  
Absorption Cycle ◽  
Absorption Cooling System

The objective of this work is to present an exergy analysis of a novel absorption configuration using water-ammonia as working fluid. The proposed configuration operates at three pressure levels. The absorber is at an intermediate pressure (Pint). A thermodynamic model based on the mass energy and exergy balances is developed for this purpose. The parameters analyzed are the refrigeration systems performance (COP), the exergy efficiency, the global exergy destruction in the system, the exergy destruction and the irreversibility in different components. The effects of generator, absorber, condenser and evaporator on the performance of the system are examined. Numerical results highlight the great importance of the intermediate pressure on the performance of the system and specially on reducing the operating generator temperature. Consequently, the intermediate pressure is directly responsible on the adaptability of the proposed cooling absorption cycle to low enthalpy sources.

Daily Exergy Assessment of LiBr-Water Absorption Chiller Used for Solar Cooling

2010 ◽  
Author(s):  
Cenk Onan ◽  
Derya B. O¨zkan
Keyword(s):  
Renewable Energy ◽  
Environmental Temperature ◽  
Cooling System ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Exergy Destruction ◽  
Solar Cooling ◽  
Dead State ◽  
Absorption Cooling ◽  
Absorption Cooling System

In today’s society in which energy costs are high, the use of renewable energy sources has gained importance in cooling and heating systems. In recent years, solar cooling, which is a type of renewable energy source, is increasing rapidly in use in Europe. A solar assisted absorption cooling system was designed for acclimatizing villas in Mardin, Turkey, and the performance of the system under different temperatures was analyzed using Matlab. The cooling load of the villas was calculated assuming a cooling season of May 15 to September 15. The cooling capacity was calculated to be 106 kW. Changes in the coefficient of performance, the capacity of the hot water driven absorption cooling system and the exergy destruction values of the system according to our country’s meteorological data were calculated using Matlab. The amounts of inlet and outlet exergy were calculated separately for each component. Calculations were performed for two dead state temperatures: 25 °C and the environmental temperature, which is a more realistic approach. Therefore, the effect of varying the dead state temperature on the results was determined. It is observed that the greatest source of exergy destruction in the system was the solar collectors and the second greatest source of exergy destruction was the generator. The hourly distributions of exergy destruction values are given in a table. The effects of environmental temperature and solar insulation were stated for the optimization of energy and exergy in the combined system, which are planned to be established.

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