سال انتشار: ۱۳۸۶

محل انتشار: پنجمین کنگره بین المللی مهندسی شیمی

تعداد صفحات: ۱۲

نویسنده(ها):

Jafari Nasr – Petrochemical Research and Technology (NPC-RT), Affiliated of National Petrochemical Company (NPC), Tehran, Iran
Pahlavanzadeh – Faculty of Chemical Engineering of Tarbiat Modares University, Jalal Al Ahmad Highway, Tehran, Iran
Mozaffari – Petrochemical Research and Technology (NPC-RT), Affiliated of National Petrochemical Company (NPC), Tehran, Iran, Faculty of Chemical Engineering of Tarbiat Modares University, Jalal Al Ahmad Highway, Tehran, Iran

چکیده:

Tube inserts are used as heat transfer enhancement devices in applications: retrofitting and new design of shell and tube heat exchangers. In this paper, Helical-wire-coils fitted inside a round tube have been experimentally studied in order to characterize their and fouling behaviors in turbulent flow regime. The present study introduces thermo-hydraulic a new experimental method to reveal for the fouling process of CaCO3 (Crystallization mechanism for water) and to study the effect of wire coil inserts on fouling resistance of CaCO3, heat transfer coefficient and friction factor. The fouling experiments were performed with the Reynolds number set at 12,824 which is correspondent to the flow velocity of 0.66 m/s in the test section. The inlet bulk temperature was 39 o C and with average total hardness 245. By adding of calcium chloride (CaCl2) and bicarbonate sodium (NaHCO3) continuously to water tank, the average total hardness keep almost constant. Fouling resistance results report from three wire coil inserts within a geometrical range of helical pitch 0.1375<p/d<0.2813 and wire diameter 0.0238<e/d<0.0750. The heat transfer and pressure drop are results from wire coils are shown in turbulent flow regime within a wide flow range: 4000<Re<52000 and almost constant Prandtl number (Pr=3.15-4.55). We proposed a mathematical restatement on Kern and Seaton fouling model for plain and enhanced tube (with wire coil type1). Also Nusselt number and isothermal friction factor correlations are proposed for turbulent regime in terms of Reynolds number (Re>4500) and inserts geometry.