Enhancing Forced Convection Heat Transfer in Annular Tubes by Using Aluminum Mesh Layers.

Sultan, Ahmed Abd El-Razik Ahmed; Sultan, Gamal Ibrahim Ahmed

doi:10.21608/bfemu.2021.147084

Enhancing Forced Convection Heat Transfer in Annular Tubes by Using Aluminum Mesh Layers.

Document Type : Research Studies

Authors

Mechanical Power Engineering Department., Faculty of Engineering., El-Mansoura University., Mansoura., Egypt.

10.21608/bfemu.2021.147084

Abstract

An experimental investigation of heat transfer and pressure drop for turbulent flow of air in an annular tube of 48.1 mm outside diameter and 24.4 mm inside tube diameter are conducted. The inner tube, which is made of polished aluminum, heated under constant heat flux and winded by aluminum mesh-layers, while the outer tube is made of plastic (PVC) and insulated from outside with glass wool. Mesh-layers are used as an augmentative device with different thickness (2.3 ≤ t ≤11.9 mm). Reynolds number varied between 3000 and 20000 and Prandtle number was about 0.7. Friction factor are found to be 2.14 : 106.8 times the empty annular tube values, while Nusselt number are found to be 1.8: 3.7 times the empty annular tube at the same Reynolds number. The Nusselt numbers are found to be 1.29: 5.2 times the empty annular tube values based on constant pumping power and constant heat transfer area, a maximum reduction in pumping power of 76% can be achieved with augmented annular tubes. It is concluded that the use of this class of augmentative device is generally more effective for the case when mesh-layers thickness (t) is nearly equal to 2.3 mm (t/_ᵟ = 0.1925, where _ᵟ_{is annular gap thickness).}Finally, correlations are developed for the prediction of friction factors and Nusselt number.

Main Subjects