A new heat transporter is described, the tiltpipe liquid thermosiphon (TLT). In service, a straight, sealed pipe, filled with liquid, is maintained in a tilted orientation. By means of the contained liquid, heat is received from a heat source at the lower end of the pipe, transported to the elevated end, and delivered to a heat sink. The heat transport rate and the temperature distribution in the TLT were studied over a wide range of tilts, with water as the liquid, contained in a steel pipe. At its optimum tilt the TLT combined a high heat transport rate with virtually no temperature degradation in the water from end-to-end of the pipe. In both of these criteria the TLT far exceeded the performance of the unit in vertical orientation, the only one examined by previous investigators. Another characteristic difference between the tilted and the vertical unit was that at any given pipe cross section in the heat transport region (i.e., between the heat source and the heat sink), the water in the tilted pipe had a higher temperature near the top of the cross-section than near the bottom. With vertical orientation there was no such temperature difference. The experimental results with the TLT, particularly in the region of the optimum tilt, were explainable in terms of a liquid thermosiphon mechanism, but a unique one. It was inferred that there was cyclical countercurrent flow of contiguous streams in a single pipe with a warmer, less dense water stream flowing axially upward through a top segment of the pipe cross-section and, separated by a quiescent interfacial plane, a cooler, more dense water stream flowing axially downward, through a bottom segment. It followed that at the pipe terminals each stream reversed itself, becoming its opposite by virtue of heat receipt/delivery at the heat source/sink. The contiguous, countercurrent flow pattern described above was confirmed visually at the optimum tilt of eleven degrees by observation of water flow inside a clear plastic tube added to the midsection of the steel pipe. The streams were rendered visible by injections of soluble coloring material in the water at the elevated and lowered ends of the pipe.

Sidney Loeb

Papers

The tiltpipe liquid thermosiphon