A heat exchanger has an outer tube and an inner tube extending through a lumen of the outer tube. The outer tube has a spiral corrugation and an inner surface of the corrugation contacts or is in proximity to an exterior surface of the inner tube to define a spiral annular channel in an annular space between the inner tube and outer tube.

The production method for producing a rifled tube, which includes a plurality of first helical ribs on its inner surface, includes: a steps of: preparing a steel tube; and producing a rifled tube by performing cold drawing on a steel tube by using a plug which includes a plurality of second helical ribs, the plug satisfying Formulae and:
0.08 <W(AB)N/(2A)<0.26(1)
0.83<S(AB)N/(2M)<2.0(2)
where, W is a width of a groove bottom surface of the helical groove; A is a maximum diameter of the plug; B is a minimum diameter of the plug; N is a number of the second helical ribs; S is the width of the groove bottom surface; and M is a pitch of adjacent second helical ribs.

Disclosed are a stainless steel having a new composition, which has properties of low strength as compared with a conventional stainless steel, that includes, percent by weight, C: 0.03% or less, Si: exceeding 0 to 1.7% or less, Mn: 1.5 to 3.5%, Cr: 15.0 to 18.0%, Ni: 7.0 to 9.0%, Cu: 1.0 to 4.0%, Mo: 0.03% or less, P: 0.04% or less, S: 0.04% or less, N: 0.03% or less, residue: Fe, and incidental impurities, and has an austenite matrix structure and an average diameter of 30 to 60 m, and a system such as an air conditioner including the stainless steel thereof.

A method, apparatus and system for fluid heat recovery, more commonly known as a heat exchanger, transfers heat ordinarily lost down a drain to preheat incoming fluid, so that heating systems use less energy to heat incoming fluid. The fluid heat recovery apparatus includes a helical fluid outflow pipe with discharge fluid traveling within it, and a fluid inflow tube embedded within helical channel depressions and between the helical ridge fins of the fluid outflow pipe that contacts the fluid inflow tube outer walls to the surrounding fluid outflow pipe outer wall helical channel depressions and helical ridge fins, and connects to fluid supply lines, thereby transferring heat to incoming fluid that flows in a counter current, then parallel, then counter current direction with respect to the helical fluid outflow pipe flow.

A heat exchanger includes a distributor, and a first heat transfer tube and a second heat transfer tube connected in parallel with each other with respect to the distributor. The first heat transfer tube is disposed above the second heat transfer tube. The first heat transfer tube has a first inner circumferential surface, and at least one first groove recessed relative to the first inner circumferential surface and arranged side by side in a circumferential direction of the heat transfer tube. The second heat transfer tube has a second inner circumferential surface, and at least one second groove recessed relative to the second inner circumferential surface and arranged side by side in a circumferential direction. An internal pressure loss of the first heat transfer tube is smaller than an internal pressure loss of the second heat transfer tube.

A double pipe heat exchanger and a method of manufacturing the same are provided. The double pipe heat exchanger including an outer pipe and an inner pipe having a first flow channel therein and having an outer diameter smaller than an inner diameter of the outer pipe and inserted into the outer pipe to form a second flow channel between the inner pipe and the outer pipe includes a plurality of first grooves formed in a spiral shape in a lengthwise direction at an outer circumferential surface of the inner pipe to enable the second flow channel to have at least partially a spiral shape and at least one second groove each formed in a portion between two first grooves adjacent to an outer circumferential surface of the inner pipe and formed along the first groove.

A heat exchanger includes: a heat transfer pipe in which refrigerant flows; and a spiral groove formed at an inner peripheral surface of the heat transfer pipe. A height of an inner wall of the groove in a radial direction of the heat transfer pipe is equal to or greater than 0.1 [mm], and when a wetted edge length of the heat transfer pipe is S, an inclination angle between a pipe axis direction of the heat transfer pipe and a longitudinal direction of the groove in a section of the heat transfer pipe parallel with the pipe axis direction is , and a length of the heat transfer pipe is L, the inclination angle is an acute angle, and a wetted area SL/cos of the heat transfer pipe satisfies SL/cos 0.5 [m2].

There is provided a heat exchanger adapted to exchange heat between a first fluid and a second fluid. The heat exchanger comprises an outer tubular body, an inner body, a first inlet, a first outlet, a second inlet and a second outlet. The outer tubular body has an inner surface. The inner body is arranged inside the outer tubular body and has an outer surface facing the inner surface of the outer tubular body, leaving free a gap between the inner surface of the outer tubular body and the outer surface of the inner body. The first inlet and the first outlet are arranged to provide a first flow path for the first fluid from the first inlet to the first outlet via a first channel and via a second channel. The second inlet and the second outlet are arranged to provide a second flow path from the second inlet to the second outlet for the second fluid in the gap between the inner surface of the outer tubular body and the outer surface of the inner body. The outer tubular body comprises the first channel. The inner body comprises the second channel. The inner body and the second channel are rotatable relative to the outer tubular body and the first channel.

The flow reactor includes three flow passages including a first flow passage, a second flow passage, and a third flow passage which spirally circulate within a space formed between an inner tube and an outer tube. The flow passages are compartmented by an inner heat transfer body and an outer heat transfer body. The heat transfer bodies spirally circulate, have a screw-like cross-sectional shape in an axial cross-sectional view, and are assembled in a screw-like configuration. By changing the shapes of a male-thread portion and a female-thread portion, the flow passage area of the first flow passage is changed, the second flow passage and the third flow passage are spirally formed, and heat exchange and reaction take place through the heat transfer bodies.

A non-circular coolant passage is disclosed, which includes one or more walls axially defining a flow path; an inlet connecting to a first end of the flow path; and an exit connecting to a second end of the flow path, wherein a size of a passage cross-section varies in the axial direction. In certain exemplary embodiments the passage cross-section size varies uniformly, while in others the passage cross-section size varies incrementally. In certain exemplary embodiments, an angular orientation of the passage cross-section varies in the axial direction. The cross-section angular orientation can vary uniformly, incrementally, or a combination of both. In still other embodiments, both the size of the passage cross-section and the angular orientation of the passage cross-section vary in the axial direction. In these embodiments, the passage cross-section size and/or the angular orientation of the passage cross-section can vary uniformly, incrementally, and/or a combination of the two.