This study investigates the effect of nozzle geometry on the intermingling process. The dimensions of intermingling nozzles with single air inlets extended across the width of a rectangular yarn channel are systematically varied. Nozzles with this cross-sectional shape prove to be easy to manufacture and efficient at intermingling. The performance is evaluated by visually inspecting the intermingled yarns and by measuring the nip frequency. We have found that the performance of nozzles with large inlet widths is weakly dependent on yarn channel geometry. The performance of nozzles with the smallest air inlet widths, on the other hand, is sensitive to yarn channel geometry. The smallest and largest yarn channels we have considered give poor intermingling results. Control of the yarn path is beneficial for the success and consistency of the intermingling process. Using yarn guides to create a diagonal yarn path across the nozzle has the additional advantage of decreasing noise production. Our extended air inlet slot ensures continuous exposure of the yarn to the supply air stream across the entire width of the yarn channel in this arrangement. We also compare our designs with four industrial nozzles under identical process conditions. This study reveals similar trends for nip frequency and power consumption. The results agree with the broad trend established in the geometry study that the shape of the yarn channel is not critical, provided the air inlet is large enough.