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The purpose of this study is the identification of the best method to apply the body force in the lattice Boltzmann method (LBM). In the simulation of mixed convection, especially for large Richardson number flows in a square cavity.

First, three methods for applying the body force were compared to each other in the LBM. Then, an LBM-based code was written in the FORTRAN language using these three methods. Next, that code was used to simulate natural/mixed convection in a two-dimensional cavity to evaluate the methods for applying the body force. Finally, the optimum way for applying the body force was used for the simulation of free convection heat transfer in a concentric annulus with Rayleigh number in a range of 1,000 to 50,000, and mixed convection heat transfer in a concentric annulus with Rayleigh number in a range of 10,000 to 50,000 and Reynolds number in a range of 100 to 400.

Mixed convection heat transfer was simulated in a two-dimensional cavity with Richardson number in a range of 0.0001 to 100. The results which were obtained in low Richardson number flows have shown good adaptation to the available data. However, the results of large Richardson number flows, for example, Ri = 100, have shown a significant difference to the available data. Investigations revealed that this difference was due to the method of applying the body force. Therefore, the choice of the best way to apply the body force was investigated. Finally, for the large Richardson number flows, the best method to apply the body force has been identified among the several techniques.

To the authors’ knowledge, the effects of methods for applying the body force were not investigated in the cavities mixed convection, even though there are numerous investigations conducted on mixed convection with the LBM. In this study, the effects of techniques to apply the body force were investigated in large Richardson number flows. Finally, the best method to apply the body force is distinguished between several techniques for the large Richardson number mixed convection flows.

The purpose of this paper is to investigate thermohydraulic characteristics of turbulent flow of water (4,000 = Re = 10,000) in a rectangular channel equipped with perforated chevron plat-fin (PCPF) with different vortex generators (VGs) shapes.

First, three general shapes of VGs including rectangular, triangular and half circle, are compared to each other. Then, the various shapes of rectangular VGs, (horizontal, vertical and square) and triangular VGs, (forward, backward and symmetric) are evaluated. To comprehensively evaluate the thermohydraulic performance of the PCPF with various VG shapes, the relationship between the Colburn factor and the friction factor (j/f) is presented, then a performance index (η) is applied using these factors.

Results show that the enhanced models of the PCPF, which are equipped with VGs, have higher values of j/f ratio and η as compared with the reference model (R). Further, the half-circle VG with the lowest pressure drop values (about 2.4% and 4.9%, averagely as compared with the S and ST vortex generators), shows the highest thermohydraulic performance among the proposed shapes. The maximum of performance index of 1.14 is found for the HC vortex generator at Re = 4,000. It is also found that the square and forward triangular VGs, have the best thermohydraulic performance among the rectangular and triangular VGs respectively and the highest performance index of 1.13 and 1.11 are reported for these VGs.

The thermohydraulic performance of the PCPF with different vortex generators VGs shapes have been investigated.

The purpose of this paper is to study the effects of using different Brownian models on natural and mixed convection fluid flow and heat transfer inside the square enclosure filled with the AlOOH–water nanofluid.

Due to fulfill of this demand, five different models for the effective thermal conductivity and viscosity of the nanofluid are considered. The following results are presented for the Ra=10⁷ to 10¹⁰ and Ri=0.01 to 100, whereas the volume fraction of the nanoparticles is varied from φ = 0.01 to 0.04.

According to the obtained results, increasing of Rayleigh number and reduction of Richardson number leads to the higher values of the average Nusselt number and entropy generation. Also, it is realized that, variation trend of the average Nusselt number and entropy generation in all cases is increasing by growing the volume fraction. It is found that the obtained average Nusselt numbers and entropy generations with Koo and Kleinstreuer are the highest among all the studied cases, and it is followed by Patel, Vajjha and Das, Corcione and Maxwell–Brinkman models, respectively.

Based on the results of present investigation, the Nusselt number difference predicted between the Maxwell–Brinkman model (as constant-property model) and Koo and Kleinstreuer model is about 7.84 per cent at 0.01 per cent volume fraction and 5.47 per cent at 0.04 per cent volume fraction for the Rayleigh number equal to 107. The entropy generation difference predicted between the two above studied model is about 8.05 per cent at 0.01 per cent volume fraction and 5.86 per cent at 0.04 per cent volume fraction for the Rayleigh number equal to 107. It is observed that using constant-property model has a significant difference in the obtained results with the results of other variable-property models.

Electronic components’ efficiency is the cornerstone of technology progress. The cooling process used for electronic components plays a main role in their performance. Embedded high-conductivity material and provided microchannel heat sink are two common cooling methods. The former is expensive to implement while the latter needs micro-pump, which consumes energy to circulate the flow. The aim of this study is providing a new configuration and method for improving the performance of electronic components.

To manage these challenges and improve the cooling efficiency, a novel method named Hybrid is presented here. Each method's performance has been investigated, and the results are widely compared with others. Considering the micro-pump power, the supply of the microchannel flow and the thermal conductivity ratio (thermal conductivity ratio is defined as the ratio of thermal conductivity of high thermal conductivity material to the thermal conductivity of base solid), the maximum disk temperature of each method was evaluated and compared to others.

The results indicated that the Hybrid method can reduce the maximum disk temperature up to 90 per cent compared to the embedded high thermal conductivity at the same thermal conductivity ratio. Moreover, the Hybrid method further reduces the maximum disk temperature up to 75 per cent compared to the microchannel, at equivalent power consumption.

The information in this research is presented in such a way that designers can choose the desired composition, the limited amount of consumed energy and the high temperature of the component. According to the study of radial-hybrid configuration, the different ratio of microchannel and materials with a high thermal conductivity coefficient in the constant cooling volume was investigated. The goal of the investigation was to decrease the maximum temperature of a plate on constant energy consumption. This aim has been obtained in the radial-hybrid configuration.