عنوان مقاله [English]
In this study, the effect of tube-insert as a passive method to increase heat transfer, instant gaslight water heater performance was evaluated. The simulation results revealed that for rotary tube-insert with different cross section shapes. The article present a numerical study of turbulent heat transfer and flow characteristics inelliptical tube equipped with two-bladed rotary tube-insert. Seven different tube-insert are tested in the current work; they included the two-bladed tube-insert with four different length of pitch 75, 100, 150 and 200 mm and three blade angle 40, 55 and 70 degree. In this study, the effect of tube-insert as a passive method to increase heat transfer, instant gaslight water heater performance was evaluated. To analyze the efficiency and effectiveness tube-insert geometric parameters and physical parameters of the flow, steady and incompressible flow gaslight water heater, using the commercial software ANSYS CFX 14 was modeled. Turbulent flow regime of the fluid is used. The numerical simulation is performed using SST turbulence model and wall function near the walls in ANSYS CFX to study the phenomena of flow field in a elliptical tube with helical blade rotors. The SIMPLE algorithm pressure-velocity coupling method, the standard pressure,
the high resolution scheme discretization scheme for momentum, energy are selected in the simulation. The results of the simple tube compared with the theoretical Gnielinski and Petukhov relationship for validate of results. Using modeling results, performance parameters such as the coefficient of friction, heat transfer coefficient, and thermal performance has been calculated and
analyzed. Effect of Tube-insert geometric parameters such as the length and angle of blades were evaluated on performance gaslight boilers. Reynolds numbers range from 3580 to 14320 is investigated. The average coefficient of thermal performance for gaslight water heater equipped with two-bladed tube-insert with length of pitch 75, 100, 150 and 200 mm, respectively, 1/017,
1/027, 1/033 and 1/042have been. By observing the results and compare them two-blade tube-insert with blade angle 55 and 70 degrees with an average coefficient of thermal performance 1/215 and 1/193 best performance in gaslight water heater have been studied. Therefore, the use of rotary tube-insert as a passive method can significantly increase heat transfer in the heat exchangers. The increase in flow velocity of the heat exchanger tube equipped with a rotary tube-insert reduce friction and prevent the accumulation of fouling. This method can also be used in heat exchangers.