Enhancing convective heat transfer for laminar flow in a tube by inserting a concentric inner tube and controlling concurrent flows: a numerical assessment

Abstract

The present study demonstrates, via a numerical simulation, the feasibility of achieving enhanced forced convection heat transfer of laminar water flow in an isoflux heated circular tube by inserting a concentric circular tube and controlling the concurrent flow distribution through the resulting concentric double-tube duct. Under identical operation conditions to those for the parent single-tube flow configuration, including the inlet fluid temperature, the total volumetric flow rate, the length of heated section, as well as the wall heat flux imposed, numerical simulations have been undertaken for the thermally developing convective heat transfer characteristics of water flow in the concentric double-tube duct featuring geometrically by three different relative radius ratio ro (= 1.2, 1.5, 1.8), compared with its parent single-tube duct of lh,ST = 0.1 at ReST = 100, 500, and 1000, respectively. In terms of the local and length-averaged heat transfer effectiveness gauged against that obtained for the parent single-tube duct, numerical results clearly demonstrate that the double-tube duct of smaller ro operating with relative larger flow rate than that in the inner tube can serve as highly effective heat transfer enhancement configuration.