Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Micropolar nanofluid flow with MHD and viscous dissipation effects towards a stretching sheet with multimedia feature

To promote radiation electrical MHD activation energy thermal extrusion manufacturing system efficiency by using Carreau-Nanofluid with parameters control method

Latent heat storage (LHS) is considered as the most promising technique for thermal energy storage, due to its high energy storage density and nearly constant working temperature. However, the lower thermal conductivity of the phase change material (PCM) used in LHS system seriously weakens thermal energy charging and discharging rates. In order to improve the thermal performance of LHS system, a lot of research on performance enhancement have been carried out. This review paper will concern on the development of PCMs and performance enhancement methods for LHS system in the last decade. The available enhancement methods can be classified into three categories: using high thermal conductivity additives and porous media to enhance PCM thermal conductivity, using finned tubes and encapsulated PCMs to extend heat transfer surface, using multistage or cascaded LHS technique and thermodynamic optimization to improving the heat transfer uniformity. The comparative reviews on PCMs, corresponding performance enhancement methods and their characteristics are presented in present paper. That will help in selecting reliable PCMs and matching suitable performance enhancement method to achieve the best thermal performance for PCM based LHS system. In addition, the research gaps in performance enhancement techniques for LHS systems are also discussed and some recommendations for future research are proposed.

A review of phase change material and performance enhancement method for latent heat storage system

In order to saving thermal energy, latent heat thermal energy storage systems (LHTESS) can be utilized. Common phase change material (PCM) has low thermal conductivity. In this paper, CuO nanoparticles have been used to enhance the performance of LHTESS. CuO–water nanofluid properties are estimated by means of KKL. This unsteady process has been simulated by Finite element method. Results prove that solidification process is accelerated by adding CuO nanoparticles in to pure PCM. As number of undulations increases average temperature and total energy profiles reduce while solid fraction profile increases. Also, it can be concluded that highest rate of solidification is obtained for dp = 40 nm.

Numerical simulation for solidification in a LHTESS by means of nano-enhanced PCM

A numerical simulation was performed to investigate the effects of longitudinal vortices on the heat transfer enhancement of a laminar flow in a rectangle duct mounted with rectangular winglet pair...

https://journals.sagepub.com/doi/pdf/10.1177/1687814016648244

Numerical study of heat transfer enhancement by rectangular winglet vortex generator pair in a channel

Using the process parameter description, we analyzed the difference between the characteristics of laminar convections through parallel plain planes with uniform temperature and heat flux. The results show the following. (1) On the wall surface of the developing region, under uniform heat flux boundary condition, the heat flux normal to the wall surface is transported through a convection process although the velocity is zero; the velocity gradient contributes to this transport, but under uniform temperature boundary condition, the heat flux normal to the wall surface is transported through a difussion process. (2) Inside the flow of the developing region, whether under uniform temperature or heat flux boundary condition, the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process, and the contributions of velocity and velocity gradient are dependent on the thermal boundary condition. (3) On the wall surface of the fully developed region, under uniform heat flux boundary condition, the heat flux normal to the wall surface is transported through a convection process; the velocity gradient contributes to this transport, but under uniform temperature boundary condition, the heat flux normal to the wall surface is transported through a diffusion process. (4) Inside the flow of the fully developed region, under uniform temperature boundary condition, the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process, and the velocity and velocity gradient contribute to these transports; under uniform heat flux boundary condition, the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process. Furthermore, the transport of the heat flux along the main flow direction is a no-net convection process; the velocity gradient contributes to the transport of the heat flux only in the normal direction of the wall surface. (5) Simply because the maximum velocity gradient component on the wall surface contributes to the transport of the heat flux normal to the wall surface under uniform heat flux boundary condition, it does not contribute to this transport under uniform temperature boundary condition; thus, the heat transfer intensity under uniform heat flux boundary condition is stronger than that under uniform temperature boundary condition.

Liang-Bi Wang

Papers

Numerical study of heat transfer enhancement by rectangular winglet vortex generator pair in a channel

Differences between laminar convections through parallel plain planes with uniform wall temperature and heat flux in terms of process parameter

A new experimental method to study the convective heat transfer characteristics of the interior passages of ventilated disc brakes

The reason that fluid flow dissipates the same energy but obtains different convective heat transfer intensity

Experimental Study on Heat Transfer Performances of Flat Tube Bank Fin Heat Exchanger Using Four Different Fin Patterns