Deposit forming wire fin and tube heat exchanger. The heat exchanger (l a) comprises a heat exchange tube (3) and at least one wire fin (2) comprising a plurality of helically formed turns of wire (2a) disposed over the heat exchange tube along the length thereof. The heat exchange tube is made of a material having high thermal conductivity and the wire fin is made of a springy material having high thermal conductivity. The exchange tube is at an angle of 0 to 30° with respect to the horizontal and a portion of each of the turns of the fin is freely supported on a portion of the heat exchange tube in thermal contact therewith. The heat exchanger has high heat transfer efficiency and can be used continuously for a long period. It is simple to manufacture, cost effective, reliable and flexible and versatile in use. (Fig 8).