Abstract: An air liquefier and separator of air constituents for a liquid air engine. Its unique structure captures the ambient air and guides it through guide vanes into a bank of spiral tubes or channels where the air is completely contained while being liquified and separated into its constituents. The spiral tubes or channels provide a compact heat exchanger design with long tube length or channel length for efficient heat transfer and liquefying of the air which is accomplished by a flow of liquid hydrogen flowing either inside a concentric tube inside the air condensing tube or flowing in a tube or channel with a common wall in contact with the air condensing tube or channel. The liquefier can easily be designed to be an integral part of a liquid air jet engine installation.