Abstract
This paper aims to study the influence of hybrid nanofluid and coolant flow direction on mass and heat transfer improvement for a bubble absorber in order to reduce the absorber length required for complete absorption. Hybrid nanofluid is used as the cooling medium. A finite difference method was used to solve the system of nonlinear differential equations. The absorber length is divided into differential elements of an incremental length dL along the absorber length. A parametric study comparing two different flow configuration (co/countercurrent coolant flow direction) of the bubble absorber was conducted to gage the influence of solid volume fraction (0% <= Phi <= 2%), direction of coolant flow, type of working fluid on heat, and mass transfer enhancement. The results show that the absorption process depends on the direction of coolant flow and the type of working medium. The absorption rate with coolant in countercurrent flow direction is higher than that cocurrent flow direction. In addition, results reveal that the heat and mass transfer, the mass absorption flux, the absorber thermal load, Stanton, and Reynolds number in binary hybrid nanofluids are enhanced more than that the binary nanofluid and NH3/H2O solution, which increase the absorption rate and consequently decrease the absorber length. The type of working medium and the solid volume fraction are the key parameters. Also results reveal that an optimal absorber length is found when using binary hybrid nanofluid as a working medium.