Thermal characterization for perforated tube bundle immersed in a thin enclosure

Dissertant

Yasin, Nabil J.

Thesis advisor

Karam Allah, Abd al-Hasan Abd
Fayid, Ikhlas M.

University

University of Technology

Faculty

-

Department

Department of Electromechanical Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2009

English Abstract

The effect of perforated (number and geometry of perforation), Tinned tube-bundle, immersed in an enclosure which represents an integral collector storage system (ICS) and the angle of iridirtatian of the enclosure on natural convection heat transfer have been experimentally and numerically investigated.

The experimental Study included manufacturing nine models of tube bundle heat exchangers and a thin enclosure having similar dimensions to the real solar collector.

Heat transfer coefficients for the bundles consisted of (24) identical brass tubes (arranged in three identical seis) contained in a thin enclosure of aspect ratio 9.3:1 and inclined at different inclination angle (15°, 30° ,45° and 60°) were obtained for a range of transient operating modes.

The nine models were ctassified to smooth and finned (medium type) tubes which classified into three groups , without perforation, perforated fins with circular perforation, and perforated fins with equilateral triangular perforation .The fins were perforated with one, two, (three only for circular) and four perforations.

Three groups of experiments representing three modes of (ICS)operation were conducted, discharge, charge and combined charge with discharge for initial isothermal and initial stratified conditions with variable values of discharge (0.09, 0.15, 0.2) kg / s and variable charging (220, 440, 660, 900 )Wm.

A three dimensional numerical simulation was carried nut for (smooth tube) using the package FLUENT (6.3.26).

The solution involves two conditions.

The first one was for isothermal enclosure at 353°K.

With all boundaries adiabatic.

The second condition represented applied heat flux on the upper surtacc (900 W / m3) with all other boundaries, are adiabatic.

Both cases were simulated for enclosure inclination angle of (45°).

The experimental results show that that the bundle- finned perforated with two triangular perforations lead to increase the Nusselt number by ( 56.6 %), comparing with that of smooth tube and by 93.3 % for a similarly configured single tube.

The Nusselt number increases with increasing of inclination angle up to the angle (45f.

A number of correlations for the : Nusselt with Rayleigh numbers were obtained according to the type of the heat exchanger and the inclination angle, also a general correlation for the overall Nusselt number with the geoirietrk values lord the tubs correlated as : Nua = 1.552 [/top-sin(9.( AT)'1]02 for 9.U104 < Ran <1.8 x l06 The correlation is found to be close to the experimental results with a difference not more than (8%) and suitable for use with other cases, studied in pervious literatures with a maximum difference of a-bout (13 %).

I the 3-0 numerical simulation shows that the behavior of the temperature distribution in the enclosure agrees well with the experimental work, The correlation based oft the numerical results shows a difference with that of the experimental results.

The applied constant heat flux on the top face of the enclosure leads to increase of the maximum difference water temperature outside the sinking plume.

Main Subjects

Mechanical Engineering

Topics

• Fluid dynamics
• Thermodynamics

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305140