Effect of orifice pressure drop on burn-out heat flux in parallel channels

As exemplified in the case of boiling water reactors, orificing at the inlet of each channel is considered to be effective in suppressing flow instability in parallel channels. It is also expected that such orificing should affect the burn-out heat flux in parallel channels. In this experiment, the burn-out heat flux in parallel channels was measured by varying the single phase (orifice) pressure drop and other conditions (flow rate and inlet temperature) in atmospheric pressure. It was found as a result that burn-out heat flux generally becomes higher as the single phase pressure drop is increased under fixed conditions of flow rate and inlet temperature. In one certain case however, the burn-out heat flux became higher with decrease of the single phase pressure drop. This was probably due to the large effect of natural circulation caused by the low flow rate of that particular case. (author)