Hossein Talebi Rostami

Bio: Hossein Talebi Rostami is an academic researcher from Amirkabir University of Technology. The author has contributed to research in topics: Heat transfer & Mechanics. The author has an hindex of 1, co-authored 3 publications receiving 3 citations.

Hydrothermal study of nanofluid flow in channel by RBF method with exponential boundary conditions

Abstract: Our study investigates the motion, temperature and volume fraction of a nanofluid that flows at a vertical channel exposed to natural and forced (mixed) convection heat transfer. The distribution function for temperature and volume fraction on the channel's wall is exponential. Nanofluid governing equations have been solved using the radial basis function method. Various parameters, including Grashof number, Brownian motion, thermophoresis parameter, plus distinct states for temperature and volume fraction functions for the channel's wall, have been probed. The results show that increasing the Grashof number by 50% will increase the fluid velocity and temperature by about 41% and 5.7% and decrease the volume fraction by 22%. In addition, it has been proved that doubling the Brownian motion parameter improves the fluid temperature and velocity by 67% and 66% and lowers the volume fraction by 53%. Moreover, increasing the thermophoresis parameter has a similar effect to the Brownian motion parameter. Finally, it has been seen that velocity, temperature and volume fraction functions strongly depend on temperature and volume fraction distribution functions on the channel's wall.

Numerically analysis of a Phase-change Material in concentric double-pipe helical coil with turbulent flow as thermal storage unit in solar water heaters

Abstract: This research investigates a 3-D double-pipe helical coil heat exchanger containing Phase-Change Material (PCM) as a thermal storage system in solar water heaters. A concentric double-pipe follows the helical profile upward and creates a heat storage unit. In the unit, water in turbulent mode flows in the inner pipe as a Heat Transfer Fluid (HTF), and RT-50 is considered PCM placed in the annulus. This heat exchanger with all related conditions is modeled in Ansys Fluent 19 software, and we used the k-ε RNG turbulence model to simulate turbulent flow. For evaluating this novel model of thermal storage unit, the impact of some critical geometrical parameters, like helical pitch, inner and outer pipe diameter, and some flow parameters, such as fluid inlet temperature and Reynolds number, have been analyzed. The most important outcomes of the investigation show that inlet temperature and inner and outer pipe diameter are critical factors for the storage system's design. A 1.5 % change in inlet temperature will enhance the melting rate by 27 %. Also, by increasing the inner pipe diameter by 42 %, the melting process was improved by 92 %, while the outer pipe diameter was inversely related to the melting rate. A 20 % increase in this parameter's value showed a 52 % reduction in the melting. Moreover, the change in the helical pitch could not significantly affect the PCM melting process, and for a 300 % increase in pitch size, the melting process increases only by 0.6 %. • PCM melting in double-pipe helical coil TES unit in a solar water heater is studied. • With turbulent HTF flow, the Reynolds number has no major effect on the melting. • Increasing HTF inlet temperature or inner coil diameter increases the melting rate. • Reducing the outer pipe diameter increases the PCM melting process. • The helical pitch has no significant effect on the melting rate.

Compound Heat Transfer Augmentation of a Shell-and-Coil Ice Storage Unit with Metal-Oxide Nano Additives and Connecting Plates

Abstract: Due to the high enthalpy of fusion in water, ice storage systems are known as one of the best cold thermal energy storage systems. The phase change material used in these systems is water, thus it is inexpensive, accessible, and completely eco-friendly. However, despite the numerous advantages of these systems, the phase change process in them is time-consuming and this leads to difficulties in their practical application. To solve this problem, the addition of nanomaterials can be helpful. This study aims to investigate the compound heat transfer enhancement of a cylindrical-shaped unit equipped with double helically coiled coolant tubes using connecting plates and nano additives as heat transfer augmentation methods. Complex three-dimensional numerical simulations are carried out here to assess the best heat exchanger material as well as the impact of various nanoparticle types, including alumina, copper oxide, and titania, and their concentrations in the PCM side of the ice storage unit. The influence of these parameters is discussed on the charging rate and the temperature evolution factor in these systems. The results suggest that using nano additives, as well as the connecting plates, together is a promising way to enhance the solidification rate by up to 29.9%.