Influences of Star Tube Insert on Thermal Performance Characteristics in Turbulent Flows in Gas Water Heater

In this work، the effects of star tube insert as one of the best passive method for enhancement heat transfer in gas water heater are studied. The effects of this tube insert with step 2، 3 and 4. 5 cm on flow characteristics and thermal performance of the gas water heater are investigated using finite volume method. In the cases studied (Reynolds numbers between 5800 and 18600)، Nu Number is obtained much higher than the gas water heater without tube insert. As the average Nu Number in the range of Re Number is 1. 91، 1. 755 and 1. 592 for step 2، 3 and 4. 5، respectively، compared to plain tube without tube insert. In order to evaluate the pressure drop with an increase in heat transfer due to tube insert، the thermal performance factor is used. The Results show that the overall effect of the star tube inserts with different steps on the gas water heater performance is desirable.