Numerical study of thermo-hydraulic characteristics of turbulent flow in finned-tube heat exchanger fitted with rotary tube-insert; three-bladed

In this study, the effect of tube-insert as a passive method to increase tankless gas water heater (TGWH) performance was evaluated numerically. Different stationary and rotary tube-inserts are tested in the current work; they included two size of stationary star tube-insert (small and large), two-bladed tube-insert with four different length of pitch ۷۵, ۱۰۰, ۱۵۰ and ۲۰۰ mm, three blade angle ۴۰, ۵۵ and ۷۰ degree and three-bladed tube-insert. To analyze the efficiency and effectiveness of TGWH, the fluid flow in heat exchanger of TGWH was modeled using the commercial software ANSYS CFX. The results show that the use of both rotating two and three-bladed tube insert improves heat transfer and their thermal performance coefficient is also desirable and more than ۱.۰

Keywords:

Rotary tube-insert , Three-bladed tube-insert , Gaslight water heater , Nusslet number , Thermal performance factor