Experimental investigation of natural convection heat transfer in narrow vertical rectangular channel heated from both sides

The heat transfer characteristics of the natural convection regime through a vertical rectangular channel simulating a cooling channel of typical material testing reactor have been experimentally investigated. Experiments are performed on demineralized water as coolant passing under atmospheric pressure through narrow rectangular channel of 80 cm length, 7 cm width and 2.7 mm gap thickness under different heat fluxes ranging from 2.7 kW/m2 to 26.8 kW/m2 that covers almost all possible heat fluxes in the single-phase liquid. The measured local Nusselt number values are compared with the predictions of two correlations for both natural and combined natural and forced convection regimes respectively. The comparison shows the need for developing new correlation to represent the obtained experimental results and to be utilized for the prediction of the local Nusselt number in thermal–hydraulics and safety analysis of the reactor. The developed correlation fits the experimental data within 5.8% relative standard deviation.

► Natural convection heat transfer of water in narrow rectangular vertical channel is investigated.
► The measured Nu values are compared with both natural and combined convection correlations.
► A relative standard deviation of 32.7% and 15.5% is achieved for both correlations respectively.
► A new correlation with 5.8% relative standard deviation is developed.