Gas absorption into a drop in the presence of an acoustic field

Abstract The present work considers acoustically enhanced gas absorption into a liquid drop accompanied by a homogeneous first order chemical reaction. The mass conservation equation was solved for the flow inside the drop induced by acoustic streaming both analytically and numerically. Two cases were considered: An analytical solution was presented for the case of high Peclet numbers, while the case of arbitrary Peclet numbers was solved numerically. The high Peclet number case is applicable for high circulation rates and serves as an upper limit on the rate of mass transfer into the drop. It also provides a check for the numerical solution. The results indicate that the effect of the acoustic field on mass transfer is especially beneficial for absorption processes without chemical reaction, or with reactions of moderate rates. The enhancement for these processes for Peclet numbers of 500–1000 was 3.3–3.5 as compared to absorption without an acoustic field. For processes with fast chemical reactions the benefits of using an acoustic field are limited, with enhancement factors in the range of 1.5–2.3.