The impact of end effects in parabolic trough collector pilot set-ups

Parabolic trough concentrators (PTC) are special kind of heat exchangers formed of parabolic curved mirrors that focuses the direct/beam radiation from the sun onto a heat collection element that runs through the focal line of the concentrator. The PTC has to be oriented in one of the existing tracking modes to track the beam radiation. The focused radiant energy from the sun is absorbed through the heat collection element and transferred to heat transfer fluid which flows through the absorber tube. In most of the tracking modes, the sun rays incident at an angle and will therefore come to the focus a little beyond the length of the absorber tube. Hence the absorber tube should be long enough to intercept the reflected solar radiation. This paper helps in calculating the increase in absorber tube length on both sides to intercept about 95 % reflected solar radiation for smaller size parabolic troughs. This end effect study will be significant for pilot or small scale set-ups in obtaining consistent test results.