Experimental and 3D simulation study of heat and mass transfer characteristics on minichannel flat tube absorber with rhombus mesh.

Conventional circular tubes and flat plate absorbers have higher efficiency and less solution amount but suffer from poor wettability, large volume and initial cost. To further enhance the performance and miniaturization of absorption refrigeration systems, this study proposes a novel falling film absorber composed of a minichannel flat tube and rhombus aluminum mesh. The performance experiment of the novel absorber was carried out under different operating conditions, such as water vapor pressure, inlet solution temperature, and solution flow rate. Under the base test conditions, the significantly high absorption rate (0.0078 kg•m^-2•s ^-1) and over all heat transfer coefficient (1917.5 W•m^-2•K^-1) are achieved in comparison with the conventional absorbers. The volume of fraction (VOF) model was established to analyze the influence of rhombus aluminum mesh on flow and heat and mass transfer processes. The rhombus mesh improves the surface coverage ratio and the global absorption rate. The rhombus mesh induces liquid film fluctuations, which refresh the gas–liquid interface and enhance the concentration gradient, ultimately promoting the local absorption rate. The absorber exhibits the best performance when the rhombus mesh has a thickness of 0.5 mm and a size of 4 mm × 8 mm. The proposed novel compact absorber provides a potential framework for miniaturizing the absorption system.