ISSN Online: 2377-424X
ISBN Print: 1-56032-797-9
International Heat Transfer Conference 11
HEAT TRANSFER IN UPWARD MIXED CONVECTIVE FLOW OF WATER IN A VERTICAL CHANNEL
Abstract
The present work deals with the results of an experimental investigation on heat transfer in water cooled vertical pipes, for thermal-hydraulic conditions ranging from forced convective flow (where pressure gradient forces are predominant) to mixed convective flow (where buoyancy forces play a major role and natural convection has significant impact on flow conditions). The flow of water in the pipe is upwards.
Experimental data confirm the reduction in the heat transfer rate for conditions where natural and forced convection act together in upward flow, mainly due to the laminarization effect in the near-wall region (buoyancy effect) .
Because of the lacking of correlations under present conditions, a new method for the calculation of the heat transfer coefficient in upward mixed convection flow is proposed. It is based on the weil-known superposition method proposed by Churchill and valid for downflow, modified accounting for the phenomenology of the upward flow (aiding flow) in comparison with downflow conditions (opposing flow).
Experimental data confirm the reduction in the heat transfer rate for conditions where natural and forced convection act together in upward flow, mainly due to the laminarization effect in the near-wall region (buoyancy effect) .
Because of the lacking of correlations under present conditions, a new method for the calculation of the heat transfer coefficient in upward mixed convection flow is proposed. It is based on the weil-known superposition method proposed by Churchill and valid for downflow, modified accounting for the phenomenology of the upward flow (aiding flow) in comparison with downflow conditions (opposing flow).