3. Lessing ring is formed by the addition of a partition across the centre of a raschig ring, which results in an area increase of about __________ percent.
6. The ends of a cylinderical vessel can be closed by a head, which can be one of the four shapes. For the same thickness, choose the one which can withstand the highest pressure.
8. Shell side heat transfer co-efficient in case of square pitch as compared to the triangular pitch under similar condition of fluid flow and tube size is