Effect of number of supports on the bending of absorber tube of parabolic trough concentrator

The circumferential non-uniformity in the temperature of absorber tube of parabolic trough leads to bending of the tube. The absorber tube is considered to be equidistantly supported at various points along the length. An analytical expression is presented in the current work for finding the bending and the results are compared with the experimental measurements. Further, the effect of number of supports and spacing between them on the shape of bent tube is analyzed using analytical equations. It is found that, keeping spacing between adjacent supports fixed, as number of supports and length of tube increase, the maximum bending does not vary beyond a certain length of tube. For the chosen system (keeping spacing between adjacent supports as 4 m), the results show that if lengths of tubes are larger than 16 m, the maximum bending remains same. The shape of bent tube is symmetric around the mid length. For one half of the tube, the bending is towards the vertex line of trough for the portion lying between 1st and 2nd support. It is away from the vertex line for the portion lying between 2nd and 3rd support and so on up to the mid length of the tube.