Interaction Effects of a Lower Heated Tube on Pool Boiling of R-124 from an Upper Horizontal Tube.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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An investigation of the interaction effects of a lower heated tube on pool boiling of pure R-124 from an upper horizontal tube was conducted at a saturation temperature of 2.2 deg C. The test tubes used were 1 smooth tubes and 2 deformed surface TURBO-B enhanced tubes. The effects of tube spacingconfiguration and lower tube heat flux on the heat transfer performance of the upper tube were investigated. For both tube arrays, the enhancing effect of bubbles from a lower tube was dramatic. This enhancement increased as lower tube heat flux increased. However, when upper tube heat fluxes were greater than 20 kWsq. meters all enhancement disappeared. For a smooth tube array in natural convection, the effect of a lower heated tube on the heat transfer from an upper tube was small. In nucleate boiling, a PD of 1.8 gave the best upper tube heat transfer performance and a vigorously nucleating lower tube eliminated upper tube hysteresis. With the lower tube unheated and an upper tube heat flux of greater than 3 kWm2, the performance using R-124 was generally better than for R-114. With a nucleating lower tube at lO kWsq. meters, again the performance of R-124 was better, but only for upper tube heat fluxes of greater than 40 kWsq. meters. For a TURBO-B tube array, a 30 degree offset of the upper tube reduced the upper tube heat transfer performance compared to the in-line configurations. This may indicate bubbles depart TURBO-B tubes differently than smooth tubes.
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