An expansion device having a passageway formed orderly by a tubular inlet portion, a tubular throat portion and a tubular outlet portion, with a closing element arranged in the throat portion, the closing element adapted to cause a Joule-Thomson expansion and cooling of an at least partially gaseous fluid that is supplied at a predetermined pressure (P1), where in the inlet portion a direction means is provided for directing the fluid according to a flow direction that is generally at an angle with respect to the longitudinal axis of the inlet portion, in order to reduce the friction of the at least partially gaseous fluid when flowing through the throat portion at the closing element, in order to approximate the transformation to a reversible isentropic transformation more closely than what is possible with the known lamination valves.