Browsing by Author "Elsaid, Ashraf Mimi"

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Enhancement of cooling characteristics and optimization of a triple concentric-tube heat exchanger with inserted ribs
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2017-10) Elsaid, Ashraf Mimi; Halim, M. A; Gomaa, Abdalla
Experimental and numerical investigation of the triple concentric-tube heat exchanger with inserted ribs has been carried out. The purpose is to evaluate the performance characteristics of the triple tube heat exchanger with rib inserts. The investigation key design parameters involve water mass flow rate, flow pattern, temperature variation, rib height and rib pitch. Numerical CFD modeling is developed using FLUENT commercial code and validation criteria is done to extend the study parameters with extra ranges. The results revealed that, the insertion of ribs to the inner annulus fluid flow of the triple tube heat exchanger participate a significant enhancement of the convective heat transfer. Higher performance index is obtained at higher rib pitch and lower rib height. A set of empirical expressions with the dimensionless design parameters have been predicted based on the obtained data. (C) 2017 Elsevier Masson SAS. All rights reserved.
Performance characteristics of a chilled water spirally coiled finned tube in cross flow for air conditioning applications
(SAGE PUBLICATIONS LTD, 2013) Gomaa, Abdalla; Aly, Wael I; Elsaid, Ashraf Mimi
In the present study, the thermo-fluid characteristics of a spirally coiled finned tube in cross flow were experimentally investigated. This investigation covered different design parameters such as curvature ratio, air velocity, flow direction, fin pitch and flow rate of chilled water on performance characteristics of the spirally coiled finned tube. The purpose was to evaluate this kind of the spirally finned-tube cooling coils with particular reference to bare coiled tube. Six test specimens were designed and manufactured with curvature ratios of 0.027, 0.03, 0.04, tube pitches of 18, 20, 30 mm and fin pitches of (33, 22, 11 mm). Experiments were carried out in a pilot wind tunnel with air Reynolds number ranging from 35,500 to 245,000. Two types of chilled water flow directions entering the spiral coil were tested at Reynolds number ranging from 5700 to 25,300, the first was inward flow direction and the other was to outward flow direction. The results revealed that the inward flow direction has significant enhancement effect on the Nusselt number compared with outward flow direction by 37.0% for tube pitch of 18 mm and curvature ratio of 0.027. The decrease of fin pitch enhances the Nusselt number by 21.92% on expense of friction factor by 10.9%. In the case of spirally coiled bare tube, the decreasing of the curvature ratio increases air side Nusselt number by 33.69% on expense of friction factor by 18.36%. General correlations of Nusselt number and air friction factor for bare and finned spirally coiled tube were correlated based on reported experimental data.
Thermal performance of the chilled water spirally coiled finned tube in cross flow for air conditioning applications
(ELSEVIER SCIENCE BV, 2012-03) Eid, Eldesuki I; Elsaid, Ashraf Mimi
The thermal performance of spirally coiled finned tube in cross flow was investigated experimentally. The effects of curvature ratio, flow direction, fin pitch and flow rate of chilled water and air on thermal characteristics of spirally coiled finned tube have been studied. Six test sections with curvature ratios of 0.027, 0.03, 0.04, tube pitches of 18, 20, 30 mm, and fin pitches of 33, 22, 11 mm were used. The experiments were done using a pilot wind tunnel with air Reynolds number range 35,500-245,000. Innermost and outermost flow directions of chilled water with Reynolds number range 5700-25,300 have been investigated. The innermost flow direction has significant enhancement effect on the Nusselt number compared with outermost flow direction. The decrease of fin pitch enhances the Nusselt number on expense of pressure drop. Decreasing the curvature ratio increases air side Nusselt number on expense of pressure drop. A set of empirical expressions for predicting the friction factor and the Nusselt number for air flow across the spiral coils have been regressed based on the obtained data in the present experiments. (C) 2011 Ain Shams University. Production and hosting by Elsevier B.V. All rights reserved.