A momentum integral model is developed to predict the size and maximum recirculating mass flow rate for the central recirculation zone produced by a swirling flow in a sudden expansion as a function of expansion ratio, swirl intensity, and inlet velocity profile shape. Experimental measurements of velocity profiles in the recirculating flow are presented for three different expansion ratios and are used to validate the model. The model is shown to give good agreement with the measurements. The recirculation rate is found to increase roughly linearly with inlet swirl intensity and expansion size.