Interaction effects of a lower heated tube on pool boiling of R-124 from an upper horizontal tube
Yusician, Joseph E.
Marto, Paul J.
Memory, Stephen B.
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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 spacing/configuration 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 kW/sq. 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 P/D 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 kW/m2, the performance using R-124 was generally better than for R-114. With a nucleating lower tube (at lO kW/sq. meters), again the performance of R-124 was better, but only for upper tube heat fluxes of greater than 40 kW/sq. 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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