THE STUDY OF HEAT TRANSFER INTENSITY AND AERODYNAMIC DRAG INSIDE A FLAT PIPE

Abstract

It is know that a heat exchange tube with a flat-oval profile has excellent thermal and aerodynamic characteristics in contrast to a round tube. Thus, with the same planes, a flat tube has a significant increase in thermal and aerodynamic efficiency compared to a round tube, which is widely used in industry. However, at present, there are a limited number of publications on the study of heat transfer and aerodynamics inside a flat pipe.
 In this paper, we present the methodology and results of the study of heat transfer and aerodynamic drag in a pipe, and describe the experimental stand for such studies.
 The experiments performed in a flowing wind tunnel with an internal diameter of 36 mm, operating in an open-loop circuit. The working medium is air drawn from the laboratory room. The prototype was a steel pipe with a flat-oval profile, 320 mm long, 30x15 mm cross section, and 2 mm wall thickness.
 The created experimental stand allows us to study the heat transfer and aerodynamic drag of a flat pipe under the boundary condition q=const. An electric heater ensured this condition, which is a nichrome wire with a diameter of 0.6 mm wound along the entire length of the pipe and insulated from the external environment.
 The experiments were carried out in the range of Reynolds numbers (10.5 - 55.0) 103 and dissipated powers (50 - 150) W. The average air temperature in the pipe was set in the range (20 - 55) 0C, and the average temperature of the pipe wall was set in the range (24 - 140) 0C in accordance with the electric power supplied to the heater.
 Empirical correlations proposed for determining the intensity of heat transfer and aerodynamic drag inside a flat pipe. The data had compared with a round tube. The results had analyzed, and it had shown for the first time that the intensity of heat transfer and aerodynamic drag in a flat-oval pipe is 1.1 to 1.2 times and 1.4 to 1.7 times higher, respectively.