Reduction of heat transfer coefficient of air-cooled sections can reach 50 % due to imperfection of mechanical contact of steel tube and ribbed shell. For the purpose of wider introduction of L-shaped coiled tubes into industry, measurements of their contact thermal resistance (CTR) by temperature jump and heat flux in the contact zone, as well as comparison with tubes with rolled fins under otherwise equal conditions in the temperature range of 30-300°С were carried out. The research showed that in the temperature range of 150-300°С the wound tubes have considerably higher CTR than the rolled tubes. After a series of experiments, the aluminum strip of L-shaped ribbing was annealed, but heating the sample to 200°С did not lead to annealing of aluminum ribs.
