The invention relates to a scraped surface heat exchanger (100) comprising a heat exchanging wall (20) having an cylindrical inner surface (21) with a radius (R + ´), a shaft (10) being rotatable mounted inside of and concentrically to the inner surface (21) of the heat exchanging wall (20) and having at least one gap portion (10A) with an outer surface (11) and a radius (R), and at least one scraping member (40) supported by the shaft (10) and extending to the inner surface (21) of the heat exchanger wall (20), characterised in that the at least one or the gap portions (10A) with an outer surface (11) and a radius (R) extend over at least 60% of the circumference of the shaft (10).
