Experimental study of heat transfer and pressure drop analysis of the air/water two-phase flow in a double tube heat exchanger equipped with dual twisted tape turbulator: Simultaneous usage of active and passive methods

•Simultaneous use of active and passive methods for enhancing the thermal performance of a double tube heat exchanger was investigated.•Air bubbles injection and twisted tape insert were used as active and passive method to increase heat transfer in a double tube heat exchanger.•Heat transfer in the heat exchanger equipped with dual twisted tape turbulators in the presence of bubble injections was significantly more than the simple one.•Heat transfer in the modified heat exchanger is up to 2.02 times the heat transfers of a plain heat exchanger.