Abstract
Due to the low efficiency and high energy consumption in air impinging freezer, two kinds of nozzle structures were compared with the aim of finding the best structure and improving the Nusselt number and heat transfer uniformity. The results showed that when the H/DE was in the range of 2-12, the average Nusselt number on the steel strip surface under the circular funnel nozzle was higher than that under the circular orifice nozzle, which was higher with about 5.41% to 15.10%. The change of the average Nusselt number on the steel strip surface under both two kinds of nozzle structures were greatly influenced by the H/DE and was less affected by the cross flow. The heat transfer uniformity index ? on the steel strip surface under the circular funnel nozzle was lower than that under the circular orifice nozzle with 7.06%-34.52% lower. As the H/DE increasing, the ? different between the two kinds of nozzle structures was gradually decreased. The circular funnel nozzle was recommended to reduce the freezing time.
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