Subfreezing heat exchanger with separate melt fluid

A heat exchanger comprising:

• a first side opposite a second side;
• a third side opposite a fourth side, wherein the third side and the fourth side extend from the first side to the second side;
• a cold layer comprising:
• a first closure bar on the third side extending from the first side to the second side;
• a second closure bar on the fourth side extending from the first side to the second side;
• and
• a cold passage between the first closure bar and the second closure bar, wherein the cold passage comprises an inlet on the first side;
• a hot layer adjacent the cold layer, the hot layer comprising:
• a third closure bar on the second side extending from the third side to the fourth side;
• a closure tube on the first side extending from the third side to the fourth side, wherein the closure tube comprises a heating fluid passage extending from the third side to the fourth side;
• and
• a hot passage between the third closure bar and the closure tube, wherein the hot passage comprises an inlet on the third side and an outlet on the fourth side.

A method of preventing ice accretion on an inlet of a cold layer of a heat exchanger comprising:

• directing a cold flow through the inlet of the cold layer at a first side of the heat exchanger and out an outlet of the cold layer at a second side of the heat exchanger;
• directing a hot flow through an inlet header of a hot layer at a third side of the heat exchanger and out the outlet header of the hot layer at a fourth side of the heat exchanger;
• and
• directing a heating fluid through a tube located on the first side of the heat exchanger, wherein the heating fluid heats the inlet of the cold layer of the heat exchanger.