Apparatus for effecting heat exchange between a liquid and a particulate material

Apparatus (10) for heating and/or cooling a particulate material, e.g. vegetables, by heat exchange with a liquid comprises a horizontal tubular chamber (12) of waisted internal cross-section containing a rotatable mesh cylinder (20) having an auger blade (22) corotatable therein. A row of inlets (A-Q) for heat exchange liquid along the bottom of the chamber are connected via external pipe work to a row of outlets (A min -Q min ) for heat exchange liquid at the top of the chamber. Upward flow of heat exchange liquid causes suspension of particulate matter as it is conveyed through the chamber by the auger, thus minimising rubbing contact on the particulate material. The apparatus includes a heating section defined by inlets A-D, a holding section defined by inlets E to L, and a cooling section defined by inlets M to Q, all within a common chamber. Within each section, each outlet is connected externally to the alphabetically preceding inlet except for the leftmost outlet which is connected to the rightmost inlet. The heating and cooling flows recover heat via a heat exchanger (28).