Heat exchanger including furcating unit cells

A heat exchanger comprising:

• an inner wall;
• a first core portion;
• and
• a second core portion, each of the first core portion and the second core portion comprising furcating unit cells coupled with each other, each of the furcating unit cells comprising:
• a sidewall that defines several openings into an interior of a furcating unit cell;
• at least a first opening of the openings configured to be an inlet to receive a first fluid into the furcating unit cell;
• at least a second opening of the openings configured to be an outlet through which the first fluid exits the furcating unit cell;
• and
• interior passageways through the interior of the furcating unit cell that direct the first fluid into the furcating unit cell, divide flow of the first fluid into separate orthogonal flows through the interior passageways, and out of the furcating unit cell, wherein:
• the sidewalls of the furcating unit cells separate exterior volumes outside of the furcating unit cells from the interior passageways of the furcating unit cells and fluidly couple the interior passageways of the furcating unit cells with each other such that a second fluid can flow through the exterior volumes and exchange heat with the first fluid flowing through interiors of the furcating unit cells without the first fluid and the second fluid mixing with each other;
• and
• the inner wall separates the first core portion from the second core portion, wherein the first fluid and second fluid flow along both sides of the inner wall, and the inner wall prevents the first fluid and the second fluid from flowing through the inner wall.