Polymeric tube-in-shell heat exchangers with twisted tubes are provided. The heat exchanger may include one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes at least one tube twisted about its length or at least one pair of tubes twisted or wound around each other. The presently disclosed polymeric tube-in-shell heat exchangers with twisted tubes may be especially suited for applications where the use of polymer tubes offers advantages, such as in the case of acid solutions, food and beverage fluids, and carbon capture applications where the use of metal heat exchangers destroy the amines used for capture.

A sinusoidal corrugated tube-type spiral wounded heat exchanger suitable for FLNG, wherein a top of an outer cylinder has a shell-side refrigerant inlet and a bottom thereof has a shell-side refrigerant outlet; a sinusoidal corrugated tube-type liquid distributor is below the shell-side refrigerant inlet, a first sinusoidal corrugated winding tube bundle and a second sinusoidal corrugated winding tube bundle, which are heat exchanger tubes with a sinusoidal wave shape, are inside the outer cylinder, and peaks and troughs of the first sinusoidal corrugated winding tube bundle and the second sinusoidal corrugated winding tube bundle are in staggered correspondence one by one from top to bottom; a sinusoidal corrugated tube-type liquid distributor includes a one-into-two-type tube, a two-into-four-type tube, two sinusoidal corrugated tube-type liquid distribution tubes from top to bottom.

The present invention concerns a boiler, in particular a condensing boiler, said boiler comprising at least one combustion zone, and a burner arranged in correspondence with said combustion zone along a longitudinal axis, and at least one first heat exchanger adapted to encircle said burner with its internal portion facing towards said burner and directly exposed to the flame of said burner, when in use, said heat exchanger providing a steel duct, preferably stainless steel, having a spiral profile and comprising a plurality of coils having a common axis of symmetry, the axis of symmetry of said first heat exchanger coinciding with said longitudinal axis of the boiler, said boiler being characterised in that the internal portion facing towards said axis of symmetry of each coil of said first heat exchanger has a continuous depression along at least one portion of said spiral profile.