Experimental study on hydraulic resistance of finned tube assembly of the air heat exchangers in fast reactors

UDC: 
УДК 621.039.587

Issue of journal:

Abstract: 

The emergency heat removal systems (EHRS) of fast reactors include independent air heat exchangers (AHE), where heat is transferred to air. The heat transfer tubes with the outside one-thread spiral fins are arranged in the in-line order. The tube pitch is 69,0 mm across the flow and 64,5 mm parallel to it. Across the cooling air flow there are 9 tube modules in the tube assembly, that is 18 finned tubes are cooled by the air flow. The finned tubes are inclined to the cross-section of the heat exchanger at an angle of ±1,5°. The air flow in the full-size system (air heat exchanger – suction pipe) is produced by means of natural convection pressure.
The full-size finned tube assembly was simulated roughly. The length of each tube was 500 mm. A cross row had 5 tubes: 4 standard ones and one tube cut lengthways with a 2-mm-thick mill. The last tube with half cross-section served as a displacer and was fixed to the shell with rectangular cross-section. The cross-section of the air flow channel of the model before the tube assembly measured 500´343 mm2. Lengthwise, the tube assembly had 18 rows. Both before and after the tube assembly there were test sections with 4 pressure taps in each. Before the first test section there was an inlet section with meshes. At the entrance to the working section there was a convergent nozzle. After the outlet test section there was a section where rectangular cross-section of the flow channel changed into circular cross-section. Lengthwise, the last element of the working section was a tube having an inner diameter of 320+(0÷0,5) mm. The tube was 3000 mm long and was calibrated as a flowmeter.
Pressure drops along the tube assembly and total pressure head in the center of the flowmeter tube were measured using МЕТRАN-100 and МЕТRАN-150. In a series of experiments measurements were also taken of the air temperature for the flow and the testing stand hall, of atmospheric pressure, of air humidity.
Experimental results were processed and presented as a function of Re. The obtained linear dependence is true in the range of Reynolds numbers 2600 – 8700. The average air velocity at the midpoint of the tube assembly length was used as the velocity scale and the outside diameter of the tube without fins (d = 0,022 m) was used as the linear scale. Results presented in the figure were used to form experimental data array for design code verification. The evaluated result uncertainty was within 5%

References: 
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