Abstract
This paper presents a theoretical investigation of the second law performance of double diffusive forced convection in microreactors with the inclusion of nanofluid and radiation effects. The investigated microreactors consist of a single microchannel, fully filled by a porous medium. The transport of heat and mass are analysed by including the thick walls and a first order, catalytic chemical reaction on the internal surfaces of the microchannel. Two sets of thermal boundary conditions are considered on the external surfaces of the microchannel; (1) constant temperature and (2) constant heat flux boundary condition on the lower wall and convective boundary condition on the upper wall. The local thermal non-equilibrium approach is taken to thermally analyse the porous section of the system. The mass dispersion equation is coupled with the transport of heat in the nanofluid flow through consideration of Soret effect. The problem is analytically solved and illustrations of the temperature fields, Nusselt number, total entropy generation rate and performance evaluation criterion (PEC) are provided. It is shown that the radiation effect tends to modify the thermal behaviour within the porous section of the system. The radiation parameter also reduces the overall temperature of the system. It is further demonstrated that, expectedly, the nanoparticles reduce the temperature of the system and increase the Nusselt number. The total entropy generation rate and consequently PEC shows a strong relation with radiation parameter and volumetric concentration of nanoparticles.
Highlights
The Second Law of Thermodynamics is amongst the most important laws of nature and plays an essential role in evaluating the available values of thermal and chemical energies
Nanoparticles were used to enhance the thermal conductivity of the base fluid and thermodynamics
Nanoparticles were used to enhance the thermal conductivity of the base fluid and internal radiation heat losses were considered within the porous section of the microreactors
Summary
The Second Law of Thermodynamics is amongst the most important laws of nature and plays an essential role in evaluating the available values of thermal and chemical energies. This law provides quantitative information about the level of irreversibility of the system and the amount of useful work destructed through a given process. Its applications to biomedical and micro-thermal systems are still in the early stages and need more investigation. Transport in microreactors has recently attracted the attention of different research communities [7,8]. Microreactors have been developed based on the advancements of micro manufacturing technology, Entropy 2017, 19, 690; doi:10.3390/e19120690 www.mdpi.com/journal/entropy
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