Print ISSN: 1813-0526

Online ISSN: 2220-1270

Current Issue
Volume 24, Issue 1

Volume 24, Issue 1, Winter and Spring 2019, Page 1-100


Simulation of two phase natural convective heat transfer in a loop thermosyphon

Raqeeb Rajab

AL-Rafdain Engineering Journal (AREJ), Volume 24, Issue 1, Pages 1-6
DOI: 10.33899/rengj.2019.163108

This research includes experimental investigation and theoretical simulation which is manufactured locally in a laboratory to assess the characteristics of the two-phase convective heat transfer and performance of a loop thermosiphon. Practical experiments were performed using pure water, hydrocarbon fluid (acetone) and a mixture of both fluids with determined weight ratios used as working fluids. The experimental results of average heat transfer coefficient that were theoretically simulated under the same boundary conditions in both cases to study the effect of the kind of working fluid on the period required to reach the steady state condition and to achieve high performance within the best design conditions of the experimental rig. A comparison was made between the simulation and experimental results and an acceptable agreement was shown. It is worth mentioning that the Computational Fluid Dynamic analysis (CFD) with Engineering Equations Solver (EES) were used in the theoretical simulation.

Experimental Study of the Scour Depth at Downstream Weirs Has Different Holes

Maryam Mohammad; Ghania Hayawi

AL-Rafdain Engineering Journal (AREJ), Volume 24, Issue 1, Pages 17-22
DOI: 10.33899/rengj.2019.163111

An experimental study was carried out  to deal with using a weir with circular holes to control the scour occurs behind it. The holes are located near the bed of the channel, their geometric details had been changed in its size, number and their distance from the bed of the channel. The channel bed was lined by crushed gravel with average diameter 11.1 cm. The thickness of the crushed gravel layer was 22 cm and its length was 4 m. There is 18 cases were conducted. Which the diameter of the holes were 1.6, 2.3, 3 cm, and for each size of them, the distance of the holes was 0, 0.25 or 0.5 cm, their number was one or three. These cases were compared with the case of using weir with no hole. The main hydraulic variable was the discharge, which five different discharges were  flowed for each case. The total number of the experiments was 95. The dimensions of the scour hole behind the weir was measured as well as the water surface elevation in the upstream of the weir.
The analysis indicated that the discharge plays the main role to increase the size of the scour hole. Using the weir with holes helps to decrease the scour occurs behind it, because the flow from holes interrupted the flow fallen from over the weir then some of its energy was dissipated. The diameter of the weir's hole that caused the smallest scour was 0.115 cm, while the most effective distance of the this hole to cause the same effect was 0.5 cm, among all the studied cases. Due to its height increases the dissipation of the energy of the falling flow.

Improvement Water Productivity for Wheat Crop at Mosul Area

Rand Huseen; Dr. Younis Hassan; Dr.Eman Sheet

AL-Rafdain Engineering Journal (AREJ), Volume 24, Issue 1, Pages 23-29
DOI: 10.33899/rengj.2019.163112

This study aimed to optimize the yield of wheat crop under rainfed Agriculture at Mosul zone in Iraq . this can be reached by the selection of proper time of seeding time which gives the best crop yield for rainfed Agriculture or by adding one supplementary irrigation of selected depth and time which gives the maximum yield or best economical return.
In this study we generated data base using program (Aquacrop) for wheat yield with rainfall depth during the season for rainfall agriculture with rainfall depth +supplementary irrigation by using one irrigation during the season with depth (25,50,100)mm adding to one week of the season which is 23 week with initial water content between field capacity and wilting point with three date to begin the agriculture season the results showed that the optimal seeding time for the rainfed Agriculture is 15 December which gives 257.5 kg/ha yield and the next is 15 November 250.5 kg/ha and 15 January 89 kg/ha, For supplementary Agriculture the best time of the irrigation is the first week of the season with a depth change inversely with rain depth and the best seeding time is 15 November.