Mass transfer at the external surface of a horizontal spiral tube exchanger placed at the bottom of a stirred tank was investigated by using the dissolution of copper in acidified dichromate technique under different considerations of (i) reactor configuration (i.e., presence of baffles, spiral tube distance from the tank bottom, spiral tube diameter and pitch, impeller geometry), (ii) acidified dichromate solution properties, and (iii) mixing intensity (i.e., impeller rotational speed). It is revealed that mass transfer increases with increasing mixing intensity, spiral tube pitch, and with the presence of baffles. The larger the spiral tube diameter, the lower the mass transport. The results, for spiral tube placed at the tank bottom, in case of axialand radial-flow impellers were correlated by dimensionless correlations with an average deviation of 11% and 9%, respectively. Applications of the current results include (i) design of a spiral tube heat exchangers in agitated vessels, (ii) design of catalytic heat exchanger/reactor suitable for exothermic reactions involving heat-sensitive materials, and (iii) design of semi-continuous spiral tube membrane equipment suitable for processes such as dialysis and ultrafiltration. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.