Experimental investigation of heat transfer and friction characteristics in circular tube fitted with various types of passive technique

Dissertant

Muhammad, Bashar Ali

Thesis advisor

Muhammad, Aqil Abd Allah
Muhyi, Rahim Joey

University

University of Technology

Faculty

-

Department

Mechanical Engineering Department

University Country

Iraq

Degree

Master

Degree Date

2013

English Abstract

The present study is to investigate experimentally the enhancement of forced convection heat transfer by means of passive techniques for a turbulent air flow in the entrance region flowing through an Aluminum test tube.

The length to diameter ratio is 30.

Reynolds number range (Red) is from 6000 to 13500 with boundary conditions of constant heat flux of (357W/m2).

The augmentation process is done by two levels at constant mass flow rate.

The first level of augmentation includes using of Nozzle- Turbulator with 0.5 diameter ratio (d/D) and with 5 pitch ratio (I/D).

Six different arrangements; convergent nozzle (CN), divergent nozzle (DN), convergent-divergent nozzle (CDN), divergent-convergent nozzle (DCN), combined convergent-divergent nozzle (combined CDN) and combined divergent-convergent nozzle (combined DCN), were taken to find the Nozzle-Turbulator arrangement that provide the highest thermal performance factor (rj), which is the ratio of Nusselt number to friction ratio at constant pumping power.

The second level of augmentation was to improve the Nozzle-Turbulator arrangement that provided the highest thermal performance factor (from the first level) by using three different modifications; perforation (triangle holes, square holes and circle holes), combining with Wire-Coil ( 8mm and 14mm coil pitch) in the core of the Nozzle-Turbulator, and combining the Nozzle-Turbulator with drilled plate.

The experimental results at the same average Reynolds number shows that at the first level of augmentation the divergent arrangement (DN) provides the highest average Nusselt number 317% and highest friction factor 17 times over that of plain tube with the highest performance factor (1.58).

While the results of the second augmentation level show the combining of Nozzle-Turbulator with the drilled plate provided the highest average Nusselt number (408%) and friction factor (35) times that provided by the plain tube with performance factor of (1.52).

On the other hand the perforated Nozzle-Turbulators with triangle holes provided (253%) for the average Nusselt number and (7.74) for the friction factor times that provided by the plain tube, but with a thermal performance factor of (1.73) which is the highest thermal performance factor among all other augmentation devices used in the present study.

For all the previous augmentation procedures a performance evaluation has been made with comparison between the augmented arrangements and the plain tube to find the effect of the inserts on average Nusselt number and friction factor with developing an empirical equation for the tested augmentation procedures.

The present work has been compared with previous works and it gives 8.4% and 9.3% deviation for the average Nusselt number and the friction factor correlations.

Main Subjects

Mechanical Engineering

Topics

• Mechanics
• Friction

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-413192