Prediction of Heat Transfer and Fluid Flow Effects on Entropy Generation in a Monolithic Catalytic Converter Using Large-Eddy Simulation

Abstract

In the present work, heat transfer and fluid flow and their effects on entropy generation in a realistic catalytic converter of a Lada Niva 21214 vehicle are studied using large eddy simulation. At first, the pressure drop over the catalytic converter is measured for dry air at constant temperature (T=298 K), different volumetric flow rates, and extrapolated to large volumetric flow rates for dry air (T=298 K) and for the exhaust gas under realistic engine conditions (T=900 K) using the Darcy–Forchheimer relation. Then, coupled heat and fluid flow phenomena inside the catalytic converter are analyzed for nonreacting isothermal conditions and nonreacting conditions with conjugate heat transfer by using the large-eddy simulation. The predicted pressure drop agrees well with the measured and extrapolated data. Based on the obtained numerical results, the characteristic flow features are identified, namely: the impinging flow with stagnation, recirculation, flow separation and laminarization within the fine ducts of the monolith, which depends on the heat transfer through temperature-dependent thermophysical properties of exhaust gas. Moreover, due to high-velocity gradients at the wall of the narrow ducts in the monolith, entropy production by viscous dissipation is observed predominantly in the monolith region. In contrast, entropy production due to heat transport is relatively small in the monolith region, while it overwhelms viscous dissipation effects in the pipe regions.

Estimation of Entropy Generation in a SCR-DeNOx System with AdBlue Spray Dynamic Using Large Eddy Simulation

“…In this regard, Figure 6 shows the estimated profile of the entropy production rate due to the viscous dissipation (see Equation ( 24 )) at SOI = 50 ms along the middle sectional plane. As pointed out in some previous contributions in the research group of authors [ 21 , 33 , 34 , 49 ], the entropy generation is essentially a sub-grid scale phenomena and the total entropy production associated with sub-grid scale is considerably higher. As evident in Figure 6 , a higher value can be seen along the spray surface and spray impingement region characterized by a strong velocity gradient.…”

“…Additionally, such a method has been successfully utilized to investigate various technical configurations and physical processes, as reported in [ 17 , 19 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. More recently, the entropy generation based analysis of monolithic catalytic converter using LES was carried out by Li et al [ 34 ] to understand especially the turbulent flow transition and to characterize the single phase flow inside the SCR monolith, namely the impinging flow with stagnation, re-circulation, flow separation and laminarization. A recent review can be found in [ 35 ] related to the entropy generation analysis in thermo-fluid systems which involve chemical reactions or combustion.…”

Entropy Generation in Peristaltic Transport of Hybrid Nanofluids with Thermal Conductivity Variations and Electromagnetic Effects

“…Recent studies [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ] have considered peristalsis of nanofluids/hybrid nanofluids, demonstrating the increasing interest in this area of research. Additionally, several investigations [ 14 , 15 , 16 ] have analyzed the entropy generation and flow characteristics of nanofluids, but few have considered hybrid nanofluids.…”

A New Perspective on Cooking Stove Loss Coefficient Assessment by Means of the Second Law Analysis

“…Losses in the internal flow field of a technical application like energy conversion in a woodburning stove can from now be assumed to be losses of flow exergy. The notion on the quality of energy and its change during thermodynamic processes is today well addressed in many contributions, to name just a few, [ 30 , 31 , 32 , 33 , 34 , 35 , 36 ].…”