A scraped surface heat exchanger is disclosed which includes a heat exchange cylinder and a vertically disposed rotating drum positioned within the cylinder having pivotal scraping elements on the periphery thereof for scraping the cylinder interior surface. The cylinder and drum define an annular product flow chamber through which product is pumped in heat transfer relationship to the cylinder. The heat transfer cylinder is surrounded by a thermally insulated jacket which in combination with the cylinder defines an annular flow chamber for circulation of a heat transfer medium to facilitate cooling or heating of product passing through the product flow chamber. The drum is mounted on a shaft which is journaled in a bearing at only one end, requiring utilization of only a single seal to seal the bearing from the product being heated or cooled. An indicator element integral with a carrier to which a rotating seal element is attached moves as the seal wears to provide a visual indication of seal wear. The carrier is designed such that the net product force acting on the carrier is in a direction tending to urge the relatively moving seal element together. Rotary agitating elements are provided at the inlet to the annular product flow chamber to distribute product, which is introduced at a single point, to the entirety of the inlet end of the annular product flow chamber. A mixing chamber located between the outlet end of the annular product flow chamber and the outlet of the heat exchanger is provided with cooperating stationary and rotary agitator elements to mix the product, thereby assuring uniform temperature distribution of product leaving the heat exchanger. A temperature sensor is mounted to the inner end of one of the stationary agitator elements to monitor the temperature of the material leaving the heat exchanger.
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