Numerical analysis of thermal stresses and strains of annular finned tube bundle in turbulent flow regime

Abstract

In this paper, the effect of turbulent flow on the thermal stresses and strains created in an annular finned-tube bundle is studied. The finite volume method and the transition SST model, along with the SIMPLE algorithm, are used to solve the flow equations, and the finite element method is used to solve the thermal stress equations in solid. The results obtained from the effective stress and strain in the annular fins bundle show that despite the temperature difference of less than 1 degree between the base and the edge of the fin, the amount of thermal stresses cannot be ignored and the asymmetric distribution of temperature in the fins leads to the shear stresses which play a key role in determining the maximum position of the effective stresses in some rows. The results show that the amount of effective stress and strain in the third and fourth rows are significantly smaller than the first and second rows. The results also show that the highest amount of the effective stress occurs in the first row and the fin base at zero-degree angle, the value of which is 0.6 MPa. The predominance of the tangential stresses at the fin base in this row is the cause of this issue. However, in the second fins onwards, although the tangential stresses are still higher, the greater asymmetry of the temperature around the fins in these rows leads to comparability of the shear stresses with tangential stresses and creates the maximum effective stress at angles other than zero degree. Therefore, according to the results of this paper, the analysis of the flow around the annular fins is necessary to calculate thermal stress and strains and it determines the vulnerable points in each tube row. It is natural that with increasing temperature difference between the base and the edge of the fin and with increasing fin hight, the importance of these studies increases.