Abstract: A heat pump with high coefficient of performance. The heat pump includes a compressor (6), a condenser (2), and an evaporator (5). The condenser (2) is connected to a water accumulator (3). A pump (15) circulates the water from the accumulator and through the condenser (2). The evaporator (5) is connected to a heat medium of a suitable kind with which heat exchange takes place. The evaporator includes a plurality of relatively short tubes (22) connected in parallel. Each tube at the lower end thereof includes separation means for oil, which is directed via a separate duct (26) to a separate oil inlet of the compressor (16). The tubes of the evaporator includes restrictions (22b) spaced along the length of the tubes. The restrictions are accomplished by the tubes being compressed while rotated. The rotations are preferably in different directions in adjacent compressions.