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1

Exergetic performance analysis of solar air heater with inverted L-shape ribs as roughness element

Chaudhari Manmohan, Sharma Sohan Lal, Debbarma Ajoy

Archives of Thermodynamics

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2023

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Vol. 44, no 3

241--267

EN

Improvement in the exegetic efficiency of a solar air heater (SAH) can be done by enhancing the rate of heat transfer. In this work, the exergetic efficiency optimization of an artificially roughened solar air heater having an inverted L-shape rib has been performed. The numerical analysis of the exergetic performance of the solar air heater was carried out at a constant heat flux of 1000 W/m2 . The study was conducted to investigate the effect of different relative roughness pitch (7.14–17.86) on the exergy losses, under the Reynolds number range of 3000 to 18 000. The roughness parameter of this geometry has been optimized and found to be among functional operating parameters like average solar intensity and temperature rise across the collector. The optimized value of relative roughness pitch is 17.86 at the isolation of 1000 W/m2 , and the parameter of temperature rise ranges from 0.005 to 0.04.

2

Thermodynamic analysis of a combined cycle power plant located in Jordan: A case study

Bataineh Khaled, Khaleel Bara A.

Archives of Thermodynamics

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2020

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Vol. 41, no 1

95--123

EN

Efficiency and electrical power output of combined cycle power plants vary according to the ambient conditions. The amount of these variations greatly affects electricity production, fuel consumption, and plant incomes. Obviously, many world countries have a wide range of climatic conditions, which impact the performance of power plants. In this paper, a thermodynamic analysis of an operating power plant located in Jordan is performed with actual operating data acquired from the power plant control unit. The analysis is performed by using first and second laws of thermodynamics. Energy and exergy efficiencies of each component of the power plant system are calculated and the effect of ambient temperature on the components performance is studied. The effects of gas turbine pressure ratio, gas turbine inlet temperature, load and ambient conditions on the combined cycle efficiency, power outputs and exergy destruction are investigated. Energy and exergy efficiencies of the combined cycle power plant are found as 45.29%, and 42.73% respectively when the ambient temperature is 34°C. Furthermore, it is found that the combustion chamber has the largest exergy destruction rate among the system components. The results showed that 73% of the total exergy destruction occurs in the combustion chamber when the ambient temperature is 34°C. Moreover, the results show that the second major exergy loss is in HRSC. The results show that the energy and exergy efficiency of the combined cycle power plant decreases as the ambient temperature increases. According to the calculation results, improvement and modification suggestions are presented.

3

Thermodynamic assessment of crude distillation units: case studies of Nigeria refineries

Osuolale Funmilayo Nihinlola, Anozie Ambrose Nwora

Archives of Thermodynamics

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2019

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Vol. 40, no 4

83--102

EN

This paper presents the results of thermodynamic analysis of the crude distillation units of two refineries in Nigeria. The analysis was intended to assess the thermodynamic efficiencies of the refineries and proffer methods of improving the efficiencies. Presented results show the atmospheric distillation units of the refineries have 33.3% and 31.6% exergetic efficiencies and 86.5% and 74.6% energetic efficiencies, respectively. Modifications of the operating and feed conditions of the refineries resulted in increased exergetic efficiencies for as much as 62.3% and 38.7% for the refineries. Thermodynamic analysis of the refineries can bring about efficiency improvement and effectiveness of the refineries.

4

Technology for development of methane-hydrate deposits jointly with receiving fresh water

Denysov Y., Klymenko V., Martynenko V., Rybicki Cz.

AGH Drilling, Oil, Gas

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2017

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Vol. 34, no. 2

531--542

EN

The technology of development of bottom gas-hydrate deposits, which allows to receive fresh water simultaneously with methane, is presented. Principal schemes are presented and methods of operation of dualpurpose plants implementing this technology and described on the basis of the methods of gas production from methane hydrates that are most prepared for practical implementation: 1) injection of warm water into the well; 2) depressive effect on the deposit; 3) replacement of methane in hydrates with carbon dioxide injected into the reservoir. The magnitude of the decrease in temperature with the depression effect on the deposit is determined. It is shown that, the amount of fresh water obtained in dual-purpose plants operating with the replacement of methane in hydrates with carbon dioxide is proportional to the coefficient of the recycling rate of CO2. For the considered schemes of dual-purpose plants, processes of decomposition of methane hydrates in the gas-hydrate formation are analyzed, an exergic efficiency estimation is performed. Such installations. The economic efficiency of a single-purpose and dual-purpose gas-producing units operating according to an approved method of depression is considered. It is shown that the most effective are dual-purpose facilities operating using the method of methane replacement in hydrates with carbon dioxide, and the coefficients of economic efficiency of dual-purpose installations are at least 1.2 times higher than similar coefficients of single-purpose gas production facilities.

5

Performance analysis of multipurpose refrigeration system (MRS) on fishing vessel

Ust Y., Karakurt A., Gunes U.

Polish Maritime Research

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2016

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nr 2

48--56

EN

The use of efficient refrigerator/freezers helps considerably to reduce the amount of the emitted greenhouse gas. A two-circuit refrigerator-freezer cycle (RF) reveals a higher energy saving potential than a conventional cycle with a single loop of serial evaporators, owing to pressure drop in each evaporator during refrigeration operation and low compression ratio. Therefore, several industrial applications and fish storage systems have been utilized by using multipurpose refrigeration cycle. That is why a theoretical performance analysis based on the exergetic performance coefficient, coefficient of performance (COP), exergy efficiency and exergy destruction ratio criteria, has been carried out for a multipurpose refrigeration system by using different refrigerants in serial and parallel operation conditions. The exergetic performance coefficient criterion is defined as the ratio of exergy output to the total exergy destruction rate (or loss rate of availability). According to the results of the study, the refrigerant R32 shows the best performance in terms of exergetic performance coefficient, COP, exergy efficiency, and exergy destruction ratio from among the other refrigerants (R1234yf, R1234ze, R404A, R407C, R410A, R143A and R502). The effects of the condenser, freezerevaporator and refrigerator-evaporator temperatures on the exergetic performance coefficient, COP, exergy efficiency and exergy destruction ratios have been fully analyzed for the refrigerant R32.

6

Parallel feed water heating repowering of a 200 MW steam power plant

Ahmadi G. R., Toghraie D.

Journal of Power Technologies

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2015

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Vol. 95, nr 4

288--301

EN

In this paper, feed water heating repowering of Shahid Montazeri steam power plant has been studied in three different modes. Efficiencies of energy and exergy have been selected as objective functions. Cycle-tempo software was used for simulations. In the first case, a low pressure heat recovery heat exchanger and a EGT-RLM600-PC gas turbine were used. Efficiencies of energy and exergy increase to 3.8% & 3.79% respectively and cooling tower water temperature difference increases to 0.652°C. In the second case, a high pressure heat recovery heat exchanger and a Siemens (KWU) V64.3 gas turbine were used. Efficiencies of energy and exergy increase to 6.68% and 6.65% respectively. In the third case, both heat recovery heat exchangers are and Westinghouse-401 gas turbines were used. Efficiencies of energy and exergy increase to 8.93% & 9.05% respectively. This is the best plan in terms of efficiency and cycle power promotion.

7

Investigations of the innovation model of exergy effectiveness of air conditioning system for operating cleanrooms

Harasym D., Labay V.

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

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2015

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z. 62, nr 4

129--140

EN

Innovation mathematical research model of the existing central straight flow air conditioning system for operating cleanrooms with the aim of computer estimation of its energy effectiveness by virtue exergetic output-input ratio depending on different factors, which have influence on its work was presented in this article. The dependence of exergetic output-input ratio ηå of the existing air conditioning system on temperature difference between the inside and the supplied air Δts=tin - ts was defined thanks to this model. It was noticed that at the given temperature difference between indoor and supplied air Δts the change in temperature of outdoor air practically don’t causes the change in exergetic outputinput ratio. The chosen air conditioning system should be preferably used at higher temperature difference between indoor and supplied air, for example at Δts = 9.0°C, that will give the opportunity to gain the highest exergetic outputinput ratio, which means to gain the most advantageous economical variant of exploitation of the chosen air conditioning system.

PL

W artykule zaprezentowano innowacyjny matematyczny model do analizy istniejącego systemu klimatyzacji z centralnym bezpośrednim przepływem wykorzystany w czystych pomieszczeniach, w celu określenia metodą numeryczną jego skuteczności energetycznej oraz zyski egzergi w stosunku wyjście-wejście zależny od różnych czynników. Na podstawie tego modelu określono zależność stosunku ηe egzergii wyjścia-wejścia istniejącego systemu klimatyzacji od różnicy temperatur Δts=tin - ts powietrza wewnętrznego i dostarczonego. Zauważono, że przy danej różnicy temperatur Δts wewnątrz pokojowy i powietrza dostarczanego, zmiana temperatury powietrza zewnętrznego nie powoduje zmiany w egzergii stosunku wyjście-wejście. Przedstawiony system klimatyzacji daje najlepsze efekty przy zastosowaniu go w wyższych różnicach temperatur wewnętrznej i powietrza dostarczanego, na przykład przy Δts= 9.0°C, system klimatyzacji uzyskuje najwyższą egzergię stosunku wyjście - wejście, który oznacza najbardziej korzystny ekonomicznie wariant eksploatacji wybranego systemu klimatyzacji.

8

Conceptual Design and Performance Analysis of an Exhaust Gas Waste Heat Recovery System for a 10000TEU Container Ship

Zheshu Ma Zheshu, Dong Yang Dong, Qiang Guo Qiang

Polish Maritime Research

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2012

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nr 2

31-38

EN

According to operation characteristics of the main engine 9K98ME-C7, a combined turbines-exhaust gas waste heat recovery system is proposed to recover waste heat and increase system energy efficiency. Thermodynamic models based on the first thermodynamic law and the second thermodynamic law are formulated. The superheated steam yield, the total electric power yield, the first thermodynamic law efficiency, the exergy efficiency at different exhaust gas boiler working pressure, and the variation of the exergy efficiency under different feed water temperature and different steam turbine back pressure are analyzed. Thermodynamic results indicate that the most appropriate exhaust gas boiler pressure is 0.8MPa for studied main engine and the total thermal efficiency with combined turbines arrangement has climbed up to 53.8% from 48.5%.