This paper describes an investigation of flow structure and heat transfer by free convection in an open ended inclined cylindrical thermosyphon with application to an evacuated tube solar collector. The flow structure was visualised by thymol blue dye and rheoscopic tracer particles. The temperature profiles were measured by a traversing thermocouple rake. During uniform heating of the tube a significant stagnant region was observed in the bottom of the tube, the length of which decreased with the increase of the wall temperature. For the case of differential heating with top half of the tube cross-section at a temperature higher than the bottom half, there was no stagnant region. When the top half was heated at a temperature lower than the bottom half there was a significant region of cellular motion in the bottom end of the tube. An inactive recirculating region in an evacuated tube solar collector and other open thermosyphons may decrease the effectiveness of the heat transfer through the open end of the tube.
|Title of host publication||ASME-JSME Thermal Engineering Joint Conference|
|Place of Publication||Tokio|
|Publisher||Japan Society of Mechanical Engineers|
|Number of pages||8|
|Publication status||Published - 1987|