Fig. 5

PBR with a helical mixer with a H = 15 mm, named IN15 (H is decreased by 5 mm from the inner side), b H = 10 mm, named IN10 (H is decreased by 10 mm from the inner side), c H = 15 mm, named EX15 (H is decreased by 5 mm from the outer side), d H = 10 mm, named EX10 (H is decreased by 10 mm from the outer side)