The Popel Report
233
volume of water than the straight copper pipe (No. 5). The same would also apply to Test Pipe 7, since it would have overtaken the straight, smooth copper pipe (No. 5) at the point where ft = 30 cm with a value of q = 0.17 litres/s. This hypothesis can now be confirmed by the thorough analysis of the measured values of Test Pipes 2, 3 and 4 as corresponding to the facts. The straight glass pipe (No. 4) at an equal difference in height h always has a smaller output than the straight copper pipe (No. 3) and the spiral helicoid copper pipe (No. 2), but up to a difference in height of 10.5 cm Test Pipe 3 delivers more than the spiral helicoid pipe (No. 2). From here onwards, however, the performance of the spiral helicoid pipe is always superior. The conclusion, which is derived from the direction of the connecting lines of the measured values of Test Pipes 5, 6 and 7 and concerning the favourable effect of the winding and t w i s t i n g of these pipes on the flow-through process lying outside the area of measurement, is therefore proven to be correct in the cases of Test Pipes 2, 3 and 4 by the ascertained measured values. The change from the unfavourable to the favourable effects of the winding and twisting of the pipes on the flow-through process to be anticipated beyond the area of measurement of Test Pipes 5, 6 and 7 in comparison to the straight, smooth pipes, already took place in the case of Test Pipes 2, 3 and 4 within the area of measurement. It is therefore appropriate to submit these test pipes to a thorough analysis. It emerges from the values in Table 1, that the pressure gradients, the dh values at the outlet of the test stand, exhibit no uniform tendency. In order to determine whether the observed deviations are to be attributed to inaccuracies in measurement, the dh values based on the output were plotted in graph form (Diagram 6) in a double logarithmical system of co-ordinates. Whereas the connecting lines of the measured values of the straight copper pipe (No. 3) and the straight glass pipe (No. 4) have an even course, those of the spiral helicoid pipe (No. 2) and also of the test stand (No. 1), on the other hand, display characteristic oscillations. The results of these measurements thus prove that the test stand itself, due to its semi-circular, downwardly pendent configuration, triggers off a similar effect to a coiling of the pipe, which however is completely or to the greatest extent annulled by the intervening incorporation of sections of straight pipe. In the case of the inclusion of the spiral helicoid pipe (No. 2), it is not assumed that the effect of the downward hanging test pipe (No. 1) has been neutralised, but perhaps even further enhanced. Hence, in order to maintain the requisite friction loss in the test pipes required maintain the output q, it is necessary further to reduce the differences in height of the water levels around the pressure gradients present at the outlet. In Diagram 7 the outputs q dependent upon the (h - dh) values are plotted on a double logarithmical coordinate system.