Heat exchange units

Claim 1

A heat exchange unit for the delivery on intermittent demand of particulate material of low thermal conductivity comprising means defining a reservoir for particulate material comprising a base portion, upstanding side portions, and a top closure, said base portion being gas permeable, said reservoir having an inlet for supply of particulate material thereto, said reservoir also having an outlet for delivery of particulate material therefrom, means for supplying gas to the reservoir through the gas permeable base portion to fluidise the particulate material therein, at least one heat transfer member in said reservoir having a surface arranged to be in heat exchange relationship with the particulate material, means for connecting the heat transfer member to an energy source for varying the temperature of said surface, and means operable synchronously with cessation of delivery of particulate material from the reservoir outlet to reduce the gas supply to the said reservoir to an amount insufficient to fluidise the particulate material in the reservoir, whereby the bulk of the particulate material remaining in said reservoir is thermally insulated from the heat transfer member by the low thermal conductivity of the particulate material adjacent the heat transfer member, and with recommencement of delivery of the particulate material to the reservoir outlet to restore the gas supply to an amount sufficient for fluidisation, whereby the particulate material then delivered is at substantially the same temperature as the particulate material delivered prior to the gas supply reduction and restoration.