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Comparison of a dual-fuel internal combustion engine performance for CNG and gasoline fuels

100%

Ameri M. , Kiaahmadi F. , Khanaki M. M.

tom Vol. 92, nr 4

214--226

In this paper, comparison of a dual-fuel internal combustion engine performance for CNG and gasoline fuels is evaluated at the steady-state condition by application of energy and exergy analysis using the experimental test results. The energy and exergy balances are calculated at different engine speeds. The results show that the energy and exergy of the heat rejection for gasoline and CNG fuels increases with increasing engine speed and the exergy efficiencies are slightly higher than the corresponding energy efficiencies. Moreover, the results show that the exergy efficiency for gas-fuel is higher than the gasoline-fuel exergy efficiency at all engine speeds. The results show that due to volumetric efficiency drop, power and torque of the gas-fuel engine is lower than gasoline-fuel one. Furthermore, the specific fuel consumption of the gas-fuel engine is lower than gasoline-fuel one. The results of this study have revealed that the most important source of the system inefficiency is the destruction of exergy by irreversible processes, mostly by the combustion. Moreover, it should be noted that liquid fuels like gasoline have many important advantages like much greater volumetric energy density, ease of transport and storage, which have made them as the preferred fuels for IC engines.

Entropy generation and thermodynamic analysis of solar air heaters with artificial roughness on absorber plate

100%

Prasad R. K. , Sahu M. K.

Archives of Thermodynamics

2017

tom Vol. 38, no. 3

23--48

This paper presents mathematical modelling and numerical analysis to evaluate entropy generation analysis (EGA) by considering pressure drop and second law efficiency based on thermodynamics for forced convection heat transfer in rectangular duct of a solar air heater with wire as artificial roughness in the form of arc shape geometry on the absorber plate. The investigation includes evaluations of entropy generation, entropy generation number, Bejan number and irreversibilities of roughened as well as smooth absorber plate solar air heaters to compare the relative performances. Furthermore, effects of various roughness parameters and operating parameters on entropy generation have also been investigated. Entropy generation and irreversibilities (exergy destroyed) has its minimum value at relative roughness height of 0.0422 and relative angle of attack of 0.33, which leads to the maximum exergetic efficiency. Entropy generation and exergy based analyses can be adopted for the evaluation of the overall performance of solar air heaters.

Vibrational effect on heat transfer and entropy generation in a circular porous cavity

80%

Mahmud S. , Fraser R. A.

tom Vol. 9, no 3

523-533

We investigate the nature of heat transfer and entropy generation for natural convection in a two-dimensional circular section enclosure vibrating sinusoidally perpendicular to the applied temperature gradient in a zero-gravity field. The enclosure is assumed to fill with porous media. The Darcy momentum equation is used to model the porous media. The full governing differential equations are simplified with the Boussinesq approximation and solved by a finite volume method. Whereas the Prandtl number Pr is fixed to 1.0. Results are presented in terms of the average Nusselt number (Nuav), entropy generation number (Nsav), Bejan number (Beav), and kinetic energy (KEav).