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In this study the influence of Brownian motion models on fluid-flow, heat transfer, and entropy generation in nanofluid forced convection with variable properties has been numerically inspected in a enclosure with central heat source. The governing equations were solved by finite volume method and SIMPLER algorithm. The numerical study was carried out for Reynolds numbers between 10 and 1000 and nanoparticles volume fraction between 0 and 0.04. The numerical results show that for all investigated models the average Nusselt number increases by nanoparticle volume fraction increment in all Reynolds number. The overall entropy generation behavior is similar to average Nusselt number variation for all inspected models. Among all analyzed models the estimation of Maxwell-Brinkman and Das-Vajjha are mainly closed to each other.

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A novel microencapsulated phase change material (PCM) with a Palmitic acid (PA) core and Copper (II) carbonate (CuCO 3 ) shell was successfully fabricated through a self-assembly method. Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to determine the chemical compositions, crystalloid phase, microstructure and morphology of PA@CuCO 3 microcapsules, respectively. The thermal properties and thermal stability of microcapsules were determined by differential scanning calorimetry (DSC) and a thermogravimetric analysis (TGA). The XRD and FT-IR results indicated the presence of all of the characteristic peaks of PA and CuCO 3 and proved that no chemical reaction had occurred between them. The SEM images showed a regular spherical morphology with rough surfaces for the PA@CuCO 3 microcapsule with average diameters ranged from 1.5 to 2 μm, and the TEM image confirmed the PA core to have been well encapsulated by CuCO 3 . In the DSC analysis results, the microcapsules indicated similar phase change behaviors as those of pristine PA, and the typical samples were melted at 66.9°C with a latent heat of 48.85 J/g and frozen at 55.7°C with a latent heat of 43.29 J/g for a microencapsulation ratio of 43.92%. TGA analyses indicated that the thermal stability of the PA was further improved due to the protection of the PA core encapsulated by the CuCO 3 shell.[a] Dr.step degradation behavior over a temperature range of 200-310°C, which is attributed to the decomposition of PA and CuCO 3 , respectively. It is clear from Figure 5 (parts b, c, and d) that the PA@CuCO 3 microcapsule samples all exhibited a maximum weight loss at higher temperatures in comparison with the pristine PA, which indicates that the CuCO 3 shells can improve the thermal stability of PA in the microcapsule.Using DSC, the phase change behaviors and latent heats of the pristine PA and PA@CuCO 3 microcapsules with different core/shell mass ratios were investigated. Figures 6 and 2 3 4 5 6 7 8