Influence of geometric parameters on the thermal and hydrodynamic efficiency of conical pipe-in-pipe heat exchangers

RELEVANCE of this work is due to the need to study the effect of the cone apex angle on the heat transfer efficiency by comparing several variants of coil-type heat exchangers (HE) of the "pipe in pipe" type. PURPOSE. To determine the degree of influence of the angle at the cone apex on the thermohydrodynamic efficiency of heat exchangers based on spring-twisted channel.

METHODS. The calculations of the conical coil HE was performed based on theoretical research and the solution of the conjugate heat transfer problem.

RESULTS. The maximum temperature value of the heated coolant was recorded for the cylindrical HE and was 53.44 °C. At angles ranging from 0 to 50°, the temperature difference was 5.12 °C (9.6%), while the cylindrical HE was 32.3% longer. The element's length was reduced by 14% when the angle was changed from 30 to 50°. The advantage of conical HE is confirmed by a higher value of the Kirpichev factor — 17,92 against 15,70 for cylindrical analogues. Replacing a smooth pipe with a spring-twisted channel allows you to obtain a final temperature of the heated coolant of 61.3 °C, which exceeds the base indicator by 11.97 °C; the Kirpichev efficiency factor for this option is 18,32. The calculations were performed for conical coil heat exchangers of the "pipe in a pipe" type based on a spring-twisted channel with a circular cross-section. It was found that an increase in the angle at the apex of the cone has a significant impact on the heat exchange processes, with the most pronounced effect occurring in the range of 50° to 70°. Based on the obtained data, the authors assume that the angle at the apex of the cone is equal to 50°. The technical and energy feasibility of using conical HE, as well as replacing smooth pipes with spring-twisted channels, is confirmed by the results of the calculations.

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