Experimental investigation on thermal-hydraulic characteristics of narrow rectangular channels with simulated neutronic feedback

Highlights: • Experimental investigation on coupling neutronic and thermal-hydraulic was conducted. • Flow and heat transfer characteristics in rectangular channel were studied. • Both quantity and rate of introduced reactivity affected the peak of power obviously. - Abstract: Single phase forced convection flow and heat transfer of deionized water in vertical narrow rectangular channels with gap size of 1.0 mm and 2.5 mm were experimentally investigated. The integration of thermal hydraulic hardware tests with simulated neutronic feedback has been carried out in this experiment. The results indicated that the transition Reynolds number from laminar to turbulent region in the narrow rectangular channels was lower. Compared with the conventional channels, the friction factors became larger in narrow rectangular channels. Nusselt number in narrow rectangular channels was higher than that in conventional channels in both laminar region and turbulent region. Furthermore, the variations of power, friction pressure drop, friction factor, heating surface temperature, inlet/outlet temperature, Re number and Nu number in transient process were investigated with consideration of neutronic feedback. It indicated that both the quantity and rate of introduced reactivity affected the peak of power. The power peak would be lower when the same reactivity was introduced using more time, while the power variation would become much more complicated and the power peak would be sharper and higher when large reactivity was introduced in a short time. The delay effect of wall and fluid temperature to the power raise could not be ignored. The temperature peak came later than the power peak. The flow resistance decreases in a small range with the increase of power. The effects from the power rise to the heat transfer coefficient have been observed as considerably small