Fluid separator for a displacement machine and a method for separating lubricant and working fluid in a displacement machine

A displacement machine arranged for acting on and compressing a working fluid in a vapor compression heat pump system, and being provided with a lubricant and working fluid separator,

• the displacement machine further comprising a displacer housing, a displacer arrangement displaceable within the displacer housing, a working chamber upon which the displacer arrangement acts to change its volume, at least one inner volume arranged for containing a lubricant and a working fluid, working fluid ports providing fluid communication between at least one volume external to the displacement machine and the working chamber, and a leakage path formed between the displacer arrangement and the displacer housing,
• wherein the fluid separator comprises a separator volume constrained by a shielding member, a first fluid channel providing fluid communication between the at least one inner volume and the separator volume, a second fluid channel providing fluid communication between the separator volume and a working fluid return volume, and
• wherein the fluid separator, the first fluid channel and the second fluid channel are fully contained within a volume defined by an outer boundary and completely sealed off from the environment wherein the displacement machine is geometrically fully constrained.