Multi-tube heat exchangers developed for hygienic/sanitary applications in the food, dairy and beverage industry. The fluids may be viscous and may also contain limited quantities of pulp and/or fibers. XLG®M Multi-tube heat exchangers are manufactured entirely from stainless steel and consist of a bundle of corrugated tubes mounted within a corrugated outer tube (which forms the outer shell). The fluid to be treated (the product) flows through the interior of the tubes forming the tube bundle and the service fluid outsider the inner tubes, through the shell.