Abstract: A heat exchanger comprises a vertically arranged circular-cylindrical holder closed at its upper end and at its lower end, and a pipe coaxially arranged within the holder. A fin is secured to the inner pipe and consists of a plurality of interconnected lamellae extending radially from the pipe, the fin being helically wound around the pipe so that the adjacent lamellae of successive turns of the resulting helix overlap each other in part, viewed in the circumferential direction of the pipe. A capillary passage is located in each lamella above the surface of an underlying lamella in a position shifted with respect to the capillary passage of the underlying lamella.

Abstract: An absorption heat pump comprising a generator which is provided with a condensation pipe (59) comprising a lower generating section (79) and an adjoining upper rectifying section (81). The upper section (81) is filled with a thermally insulating gas (87) which separates the generating section (79) from the rectifying section (81). Thus, a simple construction is obtained, in which the rectifier is integrated in the generator.

Abstract: An absorption heat pump comprising a heat-mass-exchanger (57) which is arranged in an absorber (3) and has a metal pipe (77) to which a metal fin is secured. The metal fin consists of a number of interconnected lamellae (81) which are helically wound around the pipe (77), while adjacent lamellae (81) of successive turns overlap each other in part, viewed in the circumferential direction of the pipe (77). The finned pipe (77) yields a comparatively strong heat-mass transfer in the absorber (3).

Abstract: The invention relates to a coffee maker comprising a water reservoir (1), a filter device (2) and a flow heater (3) for heating water from the water reservoir for delivery to the filter device. A problem associated with coffee makers is the deposit of scale in the flow heater. It is proposed to provide a coffee maker with means (13, 14) for adding a small amount of coffee extract to the water before it enters the flow heater (3). Coffee extract naturally contains phosphoric-acid-like compounds which inhibit the crystal growth of metal salts in the water. Preferably, coffee extract is fed continuously from the filter device (2) to the water reservoir (1).