نور محسن جاسم الحسناوي

A numerical study was conducted to examine the heat transfer and pressure drop of the metal foam-wrapped array heat exchanger. Effects of geometrical parameters, including arrangement of metal foam heat exchanger (two arrangement: fully-filled of metal foam while other have a gap between metal foam and the chamber walls), porosity, and the pore density on the thermal hydraulic performance of copper metal foam heat exchanger are examined. Numerical modelling was done considering the thermal non-equilibrium energy model and the Darcy-Forchheimer flow model for metal foam heat exchangers in the Star-CCM+ program version 2019. Four types of metal foams at fixed dimensional thickness of 0.91 with variable properties were adopted, where the pores density was 5PPI & 20PPI and the porosity was 89% and 95%. The heat exchanger system is simulated over a range of Reynolds number, based on tube diameter, from 1333 to 6555 with tubes heated at a constant wall temperature. The layout and geometry of the foam heat exchangers were compared with bare tube heat exchanger. It was found that At low porosity 89%, the configuration of metal foam heat exchanger that have pores density of 5PPI gives higher thermal performance (higher area goodness factor ratio) than 20 PPI. Also, decreasing porosity from 95% to 89% enhancement in the thermal performance was achieved. However, the metal foam heat exchanger that has a gap between metal foam and the chamber walls gave better thermal performance as compared with fully-filled foam heat exchanger.

The polydispersed nature of the spray is captured through the use of probability density functions based on the maximum entropy method to stand for the complete atomization characteristics of spray dynamics. The droplet and velocity size distributions are practical tools for the analysis of sprays cooling. The special benefit of the model is a Eulerian based which is less computationally intensive when compared to models that are based on the Lagrangian approach that tracks droplet parcel. The accuracy of using Lagrangian approach in polydispersed phase is always accurately less than Eulerian approach because it depends on the number of parcels while in Eulerian approach it depends on the proposed continuous distribution function. The main intent of the current work is to evaluate the capability of using the model for the initial predictions of the droplet size and velocity distribution for liquid nitrogen spray of solid-cone pressure swirl nozzle. The use of liquid injection pressure cases of up to 0.6MPa and spray cone angles of just 30◦ from three different sets of experimental data. The results being characterized are spray drop size distribution, liquid volume fraction and spray cone angle values. The unsteady analyses of the effect of injection pressure are studied on the cryogenic liquid nitrogen. The numerical results show that the maximum entropy method applies to liquid cryogenic spray and indicates that the model reacts correctly to changes in different injection pressures. Comparisons are also made with measured drop size distribution data that are reasonably captured and the spray cone angle is found to be in good agreement during initial and far-field spray angles.

Interphase momentum exchange of a polydispersed two-phase flow is numerically studied by using a model based on interfacial drag effects of a bulk liquid, ligaments, and droplets entrained in the air flow. A power-law relation is proposed between the droplet velocity and its diameter. The dispersed phase is modeled using the methodology of spray moments of the drop size distribution. All the equations are solved in a Eulerian framework using the finite volume approach, and the phases are coupled with the source terms. The proposed dependence accurately simulates the droplet behavior because droplets with larger diameters experience a higher drag and generally have higher velocities than smaller droplets. The model shows reasonable agreement with experimental and numerical data on the spray tip penetration and Sauter mean radius.

Fuel atomization in diesel compression ignition engines is significantly affected on the performance, evaporation, self-ignition, and emissions of the engine. Therefore, the quality of the spray atomization has to study at first. Algae-Derived renewable diesel fuel in a single hole nozzle atomizer has been chosen as an alternative fuel for diesel. The differences in physical properties of algae-derived renewable diesel, biodiesels (from palm and cooked oil) and pure diesel are effected on both spray characteristics and the internal nozzle flow. Numerical simulations are presented in this study using Eulerian-Eulerian technique to model the spray-gas interaction. The spray moments model has been used to characterize the spray parameters. First, the model is validated against the spray tip penetration of diesel spray characteristics obtained from the experimental data conducted in house-code using constant volume spray chamber and the results show a good agreement. Then, comparisons were made among the selected fuels. The numerical simulations show that the algae-derived renewable diesel is very similar to pure diesel and can be used as an alternative fuel.

There are no numerical research paper attempts to simulate the break-up mechanism of droplets in the spray development. In particular, the work described here refers to study and quantify the break-up of droplets regime and their effects on the spray behavior. With this purpose, the model parameters results, based on droplet break-up model proposed by Reitz and Diwakar [1] and momentum flux calculations are performed. The parameters that are used in the droplet break-up model are stored in the code as properties. These properties are saved in every computation cell. The parameters are Weber number, break-up time and stable droplet diameter. The numerical simulation is implemented as Eulerian-Eulerian approach. The spray moments theory is used for the liquid phase. Finally the study is implemented in a conceptual model to investigate the possible benefits of the droplet break-up model. A good agreement for the numerical results are compared with the experimental data for the spray tip penetration.

The aim of this paper is to provide information concerning the effect of low co-flow velocity on the turbulent diffusion flame for a simple type of combustor, a numerical simulated cases of turbulent diffusion hydrogen-air flame are performed. The combustion model used in this investigation is based on chemical equilibrium and kinetics to simplify the complexity of the chemical mechanism. Effects of increased co-flowing air velocity on temperature, velocity components (axial and radial), and reactants have been investigated numerically and examined. Numerical results for temperature are compared with the experimental data. The comparison offers a good agreement. All numerical simulations have been performed using the Computational Fluid Dynamics (CFD) commercial code FLUENT. A comparison among the various co-flow air velocities, and their effects on flame behavior and temperature fields are presented.