Improvements to heat exchangers

A heat exchanger assembly comprises a tubular casing (1) housing product conduit pipe (8) and a rod (14) extending through each pipe (8). The rod (14) being reciprocatingly moveable along the pipe (8) and having a scraping means (15) projecting from it such that upon reciprocation of the rod (14) within the pipe (8) the scraping means (15) will scrape product residues from the inner walls of the product conduit (8), allowing improved heat transfer to be achieved whilst the assembly continues to operate.