Mohammad Tarawneh

Performance study of a domestic refrigerator powered by a photovoltaic generator

A small refrigerator (110 W) operated by a photovoltaic generator was used in this study. The performance of the refrigerator was exhibited in several figs where the power (P, in W), the capacity (cap, in W) and the coefficient of performance (COP) were treated as the dependent parameters. The evaporating temperature (Te, in °C) and the condensing temperature (Tc, °C) were used as the independent parameters. Experimental results showed that solar energy system using deep discharge batteries with inverter is an attractive substitute for the mains power; the performance curves indicated an acceptable performance of the unit. Daily energy consumption by this refrigerator reaches about 0.5 kW h/day. For a building of 50 offices a 25 kW h/day can be extracted from such systems. This will reduce CO2 emission of around 15 kg/day (5.5 tons per year).

Dimensional analysis and empirical correlations for heat transfer and pressure drop in condensation and evaporation processes of flow inside micropipes: case study with carbon dioxide (CO2)

In this paper, the experimental results of the convection heat transfer coefficient and pressure drop values during condensation and evaporation of CO2 were obtained at different operating conditions for flow inside micropipes. Reynolds number (ReD) ranged between 2000 and 15000. The dimensional analysis technique was utilized to develop correlations for Nusselt numbers and pressure drops. A comparison between experimental and correlated results was carried out. The results showed that for the condensation process, the bias errors were 5.25% and 0.4% for pressure drops and Nusselt number respectively. Consequently, Average Standard Deviation (ASD) values reached 17.94% and 4.62% for both respectively. On the other hand, for the evaporation process, the Nusselt number error was 3.8% with an ASD of 4.14%. The correlations presented in the present work can be used in calculating pressure drops and heat transfer coefficients for phase change flows in mini and micro tubes. It helps to enhance design calculations of heat exchangers, condensers and evaporators

Double vortex generators for increasing the separation efficiency of the air separator

This article presents a numerical analysis of multi–phase flow with powerful swirling streams in a cylindrical separator equipped with two vortex generators in an attempt to predict the separation efficiency of an air–water mixture. New design of a cylindrical separator is introduced for air–water mixture. The mixture multiphase and large eddy simulation (LES) turbulence models were applied. Images that concern velocity field, pressure, and volume fraction are introduced. Air phase is trapped and localized along the centerline of the separator and then migrates toward the upper exit hole, while water phase is distributed and rotated along the wall, then confined at the mid–separator due to two strong clock–wise centrifugal forces before it is expelled through its exit at mid of separator. It was found that the separation efficiency at constant Reynolds number of 8×10 with two feeding volume fractions of 95% and 90% are 97.8% and 96.1%, respectively. Also, the separation efficiency at constant feeding volume fraction of 95% with two Reynolds numbers of 2×10 and 8×10 are 98.6% and 97.8%, respectively. It is revealed that the separation efficiency will increase as the Reynolds number increases and/or increasing the volume fraction.

Parameters Affecting Heat Transfer During Condensation Inside Micropipes: Surface Tension Effect. Paper II

Experimental and analytical investigation was carried out to show the effect of surface tension on the heat transfer coefficient of gas flow inside micropipe heat exchangers during the condensation process. An empirical correlation was formulated for the coefficient of the convective heat transfer. A comprehensive comparison between the experimental results with published correlations in the literature and that obtained by the developed correlation was conducted. The results showed that the predicted heat transfer coefficient of the proposed correlation was closer to the experimental results than any other correlation, a finding related to the consideration of the surface tension.

Simplified Correlation Equations of Heat Transfer Coefficient During Phase Change Flow Inside Tubes Filled With Porous Media

In this work an easy to use, simple and direct equations were formulated and tested. Heat transfer coefficients of phase change fluid flow were examined in this work. The considered fluid flow encountered convection heat flux inside rigid tubes filled with porous media. During the flow, phase change was assumed. Experimental work was conducted using Carbon dioxide as fluid.An analytical method using exponential non dimensional analysis was used. The Buckingham π theorem and method of indices was used to obtain simplified formula for the convection heat transfer coefficient and for the Nusselt number.Two different correlations can be extracted from this formula; one for the evaporation process and the other for the condensation process.Copyright