Abstract
The work summarizes the results of the exp erimental investigation of convective heat transfer and pressure loss characteristics of air flow in horizontal circular copper tube of diameters 133/22 mm. The coil wire (with diameter of 1.4 mm) was inserted in the tested tube. The helix angle changed from 4.26oc to 30.78°. The outer surface of the tube was heated by a little superheated steam (2-3°C) at one atmosphere. During the experimental work, Reynolds number changed from 60 to 4000 and Prandtl number was about 0.7. The enhancement of heat transfer for the tested tube with internal coils was higher than that of the bare tube by about 57%. However, a quantitevely increase in hydrodynamic resistance was noticed. Correlation of Nusslet number and friction coefficient has been made. It was found that the Nusslet number was strongly dependent nn Reynolds number, wherase the friction coefficient is dependant on helix angle as well as Reynolds number.
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