Enhancement of heat transfer in a vertical shell and tube heat exchanger using air injection and new baffles: Experimental and numerical approach

Abstract

Vertical shell and tube heat exchangers play a critical role in many industrial processes, and their importance lies in their high heat transfer efficiency, versatility, compact size, easy maintenance, and longevity. To improve the hydrothermal performance, this research investigates the influences of air bubbles injection inside the shell with disc and ring baffles with circular holes, which is the first time to be addressed. The experiments used a fixed oil mass flow rate with 0.23 kg/s inside the tube sides and various cold water flow rates on the shell side within the 0.15–0.23 kg/s range. Three baffles’ configurations, such as single segmental (SSB), disc and ring (DRB), and disc and ring with circular holes (DRCHB), were investigated with different volume flow rates of air bubbles injection in the shell experimentally. A numerical model is performed and validated for the three baffles shapes. The performance parameters such as number of transfer units, effectiveness, heat transfer coefficient, pressure drop, and performance evaluation criterion are studied. The experimental findings showed that efficacy improved with the increase of the cold-water mass flow rates, whereas the DRCHB baffle shape with air injection)10 × 10−5 m3/s(achieved the highest effectiveness with an enhancement rate of 202% to 231%. The DRCHB configuration with maximum air injection has the highest values of the number of transfer units, heat transfer coefficient, and performance evaluation criterion compared to the other baffles configurations moreover, the pressure drop is the smallest in this case DRCHB without air injection. The numerical results showed that both novel configurations (DRB and DRCHB) have more uniform velocity and temperature distributions compared to the segmental baffles, which may effectively increase the hydrothermal performance.