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•Twisted tape with continuous rectangular cut edges (RCCTT) have been investigated.•Nusselt number is 2.23 and 1.63 times that of plain tube (PT) and TT respectively.•Mean friction factor is 3.5 and 1.3 times that of PT and TT respectively.•Performance factor of 1.56 is achieved, proving RCCTT as better variants of TT.•Augmented heat transfer rate with marginal penalty of pressure drop is achieved.

The absorber is a very important component of the solar concentrating collector. The overall heat loss coefficient of the flat rectangular absorber and multi-tube absorber were studied experimentally. Both absorbers were coated with ordinary dull black paint. The heat loss coefficient was comparatively 4–11% lower in the case of round pipe absorber and increased with the absorber temperature in both cases. The surface area of the multi-tube absorber was about 20% higher than the same of rectangular pipe absorber. The performance of the linear Fresnel solar concentrating device with trapezoidal cavity absorber was studied at different concentration ratios. The solar device with round pipe absorber achieved higher thermal efficiency (up to 8%) as compared to rectangular pipe absorber which may be attributed to higher absorber surface area and lower heat loss coefficient.