Thermal convection heat exchanger

1,146,423. Tubular heat exchangers; heat storage apparatus. COMSTOCK & WESCOTT Inc. 10 Jan., 1967 [7 Nov., 1966], No. 1357/67. Headings F4S and F4U. A heat exchanger 10 mounted in a liquid container (26, Fig. 3) and particularly for use with heat storage apparatus comprises two heat exchange coils 16, 18 held in spaced relationship by spacers 20 between concentric inner and outer cylindrical shields 12, 14 which may be made from metal or synthetic plastic material. Heat exchange fluid enters the coils through an inlet 24 and leaves through an outlet 22. The coils are preferably connected in parallel (as shown) but alternatively may be connected in series wherein the inlet 24 and outlet 22 are situated at the same level. In operation the heat exchanger is positioned free standing in the container (26) containing a liquid, e.g. water, to be heated such that the liquid can freely circulate upwardly over the heat-exchange coils due to naturally occurring thermal convection currents. The heat-exchanger when used in conjunction with heat storage apparatus normally employs superheated steam formed in that apparatus as the exchange fluid. This, on heat exchange with the liquid in the vessel (26) condenses to water which can then be recirculated to the heat storage apparatus to be revaporized into steam. An alkali metal hydroxide composition maintained at a temperature of up to 1200‹ C. may be employed as the heat storage material in the apparatus. The temperature to which the liquid in the vessel (26) is heated may be controlled by regulating the steam flow to the heat exchanger.