Irreversibility analysis of cross flow heat exchangers

Oğulata, R. Tuğrul; Doba, Füsun; Yılmaz, Tuncay

doi:10.1016/s0196-8904(00)00020-0

Cited by 56 publications

(25 citation statements)

References 8 publications

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“…Two factors, temperature difference and frictional pressure drop, are responsible for irreversibilities in heat exchangers [8,102,103]. Yilmaz et al [103] implied that the greatest source of irreversibility in a heat exchanger comes from fluid friction in the form of pressure drop.…”

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

“…Thermodynamic analyses for the balanced cross-flow recuperative plate-type heat exchanger with unmixed fluids were done by Oğulata et al [102]. Ordόñez and Bejan [108] did a numerical optimisation for the parallel-plate heat exchanger.…”

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

“…(24) for an ideal gas in the flow channels of the heat exchanger. This equation or a similar version is also used in the literature by various authors [1,8,11,102,103,107,108] and is recommended by the authors of this paper. According to Ordóñez and Bejan [108], entropy is also generated due to the discharge at the (24)), the inlet and outlet temperatures and pressures, and the heat loss from the recuperator are required.…”

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

“…The heat loss to the environment from the surface of the recuperator can be a significant factor and it is recommended that it is included in solar thermal Brayton cycle analysis. Hesselgreaves [107], Oğulata et al [102] and Ordόñez and Bejan [108] suggested that the NTU -e (effectiveness -number of transfer units) method, based on the second law of thermodynamics, can be used to get the outlet temperatures and the total heat transfer rate from the hot fluid to the cold fluid. This is shown in the literature by Haugwitz [109] and Le Roux et al [33 -35].…”

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

“…Heat transfer and pressure losses as well as the optimisation of price, weight and size should be considered while designing the heat exchanger [102]. According to Bejan [8], heat exchanger irreversibilities can be decreased by slowing down the fluid which is traveling through the heat exchanger.…”

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

See 4 more Smart Citations

A review on the thermodynamic optimisation and modelling of the solar thermal Brayton cycle

Roux

Bello‐Ochende

Meyer

2013

Renewable and Sustainable Energy Reviews

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Many studies have been published on the performance and optimisation of the Brayton cycle and solar thermal Brayton cycle showing the potential, merits and challenges of this technology. Solar thermal Brayton systems have potential to be used as power plants in many sun-drenched countries. It can be very competitive in terms of efficiency, cost and environmental impact. When designing a system such as a recuperative Brayton cycle there is always a compromise between allowing effective heat transfer and keeping pressure losses in components small. The high temperatures required in especially the receiver of the system presents a challenge in terms of irreversibilities due to heat loss. In this paper, the authors recommend the use of the total entropy generation minimisation method. This method can be applied for the modelling of a system and can serve as validation when compared with first-law modelling. The authors review various modelling perspectives required to develop an objective function for solar thermal power optimisation, including modelling of the sun as an exergy source, the Gouy-Stodola theorem and turbine modelling.With recommendations, the authors of this paper wish to clarify and simplify the optimisation and modelling of the solar thermal Brayton cycle for future work. The work is applicable to solar thermal studies in general but focuses on the small-scale recuperated solar thermal Brayton cycle.2

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Section: Recuperator or Heat Exchangermentioning

confidence: 99%

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

Section: Recuperator or Heat Exchangermentioning

confidence: 99%

See 3 more Smart Citations

A review on the thermodynamic optimisation and modelling of the solar thermal Brayton cycle

Roux

Bello‐Ochende

Meyer

2013

Renewable and Sustainable Energy Reviews

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Thermodynamic optimisation of the integrated design of a small-scale solar thermal Brayton cycle

Roux

Bello‐Ochende

Meyer

2011

Int. J. Energy Res.

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SUMMARYThe Brayton cycle's heat source does not need to be from combustion but can be extracted from solar energy. When a black cavity receiver is mounted at the focus of a parabolic dish concentrator, the reflected light is absorbed and converted into a heat source. The second law of thermodynamics and entropy generation minimisation are applied to optimise the geometries of the recuperator and receiver. The irreversibilities in the recuperative solar thermal Brayton cycle are mainly due to heat transfer across a finite temperature difference and fluid friction. In a small-scale open and direct solar thermal Brayton cycle with a micro-turbine operating at its highest compressor efficiency, the geometries of a cavity receiver and counterflow-plated recuperator can be optimised in such a way that the system produces maximum net power output. A modified cavity receiver is used in the analysis, and parabolic dish concentrator diameters of six to 18 metres are considered. Two cavity construction methods are compared. Results show that the maximum thermal efficiency of the system is a function of the solar concentrator diameter and choice of micro-turbine. The optimum receiver tube diameter is relatively large when compared with the receiver size. The optimum recuperator channel aspect ratio for the highest maximum net power output of a micro-turbine is a linear function of the system mass flow rate for a constant recuperator height. For a system operating at a relatively small mass flow rate, with a specific concentrator size, the optimum recuperator length is small. For the systems with the highest maximum net power output, the irreversibilities are spread throughout the system in such a way that the internal irreversibility rate is almost three times the external irreversibility rate.

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Exergy efficiency analysis of a shell and tube heat exchanger condenser based on its different design parameters

Fakhrolmobasheri

Rostami

2019

Heat Trans. Asian Res.

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This paper evaluates the optimum coolant temperature considering the exergy loss in a shell and tube condenser in which vapor is at its saturated temperature. First, exergy loss was formulated mathematically and then presented as a function of operating temperatures and optimum coolant and steam mass flow rates. The optimization problem was defined by full condensation of vapor in a condenser and solved by a sequential quadratic programming method. The optimization results were obtained for an industrial condenser for two condensate temperatures of 46°C and 54°C. When the upstream steam mass flow rate increased, the optimum coolant temperature and the exergy efficiency decreased, and the exergy loss also increased simultaneously. The results showed higher values for the higher condensate temperature of 54°C compared with that for 46°C. For instance, if the condensate temperature increases from 46°C to 54°C, the coolant temperature will be increased from 16.76°C to 25.17°C. In addition, by assuming the ambient temperature of 15°C, the exergy loss will be decreased from 172.5 to 164.6 kW. A linear relationship was also shown between the exergy efficiency and the dimensionless temperature, which is presented as a ratio of the temperature difference rate between inlet cooling water and ambient temperatures to the temperature difference rate of condensate and ambient temperatures.

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Irreversibility analysis of cross flow heat exchangers

Cited by 56 publications

References 8 publications

A review on the thermodynamic optimisation and modelling of the solar thermal Brayton cycle

A review on the thermodynamic optimisation and modelling of the solar thermal Brayton cycle

Thermodynamic optimisation of the integrated design of a small-scale solar thermal Brayton cycle

Exergy efficiency analysis of a shell and tube heat exchanger condenser based on its different design parameters

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