Longitudinal vortex generation is a well-known passive technique for thinning the thermal boundary layer and hence enhancing the heat transfer, but its performance while considering the thickness is essentially unknown. In this study, a single triangular shaped winglet type vortex generator having finite thickness is analyzed in a plate fin heat exchanger with triangular inserts as secondary fins. The vortex generators are mounted on bottom and top plates of the heat exchanger and triangular inserts forms a channel, each representing the symmetry for the gas-side element of the compact heat exchanger. Heat transfer and pressure drop is computed to determine the effectiveness of the vortex generator while varying its thickness, size, and angle of attack under confined laminar flow condition. In addition the winglet is tilted from vertical at an angle known as acute angle and it was found to produce two longitudinal vortices which better did the thinning of boundary layer. It is shown that adding thickness to triangular winglet and mounting at ψ = 45°, augment heat transfer along the channel wall as high as 19.7% with a corresponding increase of 7.8% in pressure loss.