Laminar mixed convection heat transfer in a vented square cavity separated by a porous layer filled with different nanofluids (Fe3O4, Cu, Ag and Al2O3) has been investigated numerically. The governing equations of mixed convection flow for a Newtonian nanofluid are assumed to be two-dimensional, steady and laminar. These equations are solved numerically by using the finite volume technique. The effects of significant parameters such as the Reynolds number (10 ≤ Re ≤ 1000), Grashof number (103 ≤ Gr ≤ 106), nanoparticle volume fraction (0.1 ≤ ϕ ≤ 0.6), porous layer thickness (0 ≤ γ ≤ 1) and porous layer position (0.1 ≤ δ ≤ 0.9) are studied. Numerical simulation details are visualized in terms of streamline, isotherm contours, and average Nusselt number along the heated source. It has been shown that variations in Reynolds and Darcy numbers have an impact on the flow pattern and heat transfer within a cavity. For higher Reynolds (Re >100), Grashof (Gr > 105) numbers and nanoparticles volume fractions the heat transfer rate is enhanced and it is optimal at lower values of Darcy number (Da = 10-5). In addition, it is noticed that the porous layer thickness and location have a significant effect on the control of the heat transfer rate inside the cavity. Furthermore, it is worth noticing that Ag nanoparticles presented the largest heated transfer rate compared to other nanoparticles.

The paper presents a thermomechanical computational solid mechanics analysis (CSM) of a pipe "double omega", used in the steam superheaters in circulating fluidized bed (CFB) boilers. The complex cross-section shape of the "double omega" tubes requires more precise analysis in order to prevent from failure as a result of the excessive temperature and thermal stresses. The results have been obtained using the finite volume method for transient state of superheater. The calculation was carried out for the section of pipe made of low-alloy steel.

Various methods for steady-state and transient analysis of temperature distribution and efficiency of continuous-plate fins are presented. For a constant heat transfer coefficient over the fin surface, the plate fin can be divided into imaginary rectangular or hexangular fins. At first approximate methods for determining the steady-state fin efficiency like the method of equivalent circular fin and the sector method are discussed. When the fin geometry is complex, thus transient temperature distribution and fin efficiency can be determined using numerical methods. A numerical method for transient analysis of fins with complex geometry is developed. Transient temperature distributions in continuous fins attached to oval tubes is computed using the finite volume - finite element methods. The developed method can be used in the transient analysis of compact heat exchangers to calculate correctly the heat flow rate transferred from the finned tubes to the fluid.