Numerical investigation on thermal-hydraulic performance of air preheater equipped with helical inserts

Abstract

In the present work, a numerical study has been done for the air preheater equipped with different types of helical inserts inside the tubes with segmental baffles in shell. The simulations have been carried out to analyse the heat transfer rate in terms of heat transfer coefficient and friction factor with ANSYS 18.0. The air preheater is divided into two sections shell side and tube side, which contains ambient air and flue gases respectively. The air preheater consists of 34 tubes with a length of 3 m. In the present study, three different types of inserts are investigated with a pitch to diameter ratio (p/d) of 2, 1.7 and 1.4, and the number of turns of 100, 87 and 73, respectively. The insert under study is helical shaped with circular cross-section of diameter 20 mm. Four different values of Reynolds number are used in the range of 4000–24,000. The effects of pressure drop, heat transfer coefficient on different pitch to diameter ratio (p/d) 2, 1.7 and 1.4 of inserts and on the plain tube are discussed in this present work. The results of an air preheater with inserts in tubes get higher value of heat transfer coefficient as compared to the plain tubes. The thermal performance factor of air preheater with inserts of (p/d = 1.4) shows higher factor of 2.31 as compared to the plain tubes at low Reynolds number.