The present invention relates to an internal heat exchanger double-tube structure of an air conditioning system having an alternative refrigerant applied thereto for heat exchange between a low-temperature low-pressure refrigerant discharged from an evaporator and a high-temperature high-pressure refrigerant discharged from an condenser, the double-tube structure including: an inner pipe having a channel through which the low-temperature low-pressure refrigerant discharged from the evaporator flows; and an outer pipe surrounding the inner pipe and having a channel through which high-temperature high-pressure refrigerant flows, wherein the inner pipe has a spiral groove forming a channel on an outer side thereof, and the spiral groove is a recessed groove for generating a vortex that increase a channel volume where high-temperature high-pressure liquid flows inward and reduces a vortex of flowing fluid.

A grey water heat recovery apparatus is disclosed in which heat is transferred between a grey water stream and a fresh water stream. The apparatus comprises: a grey water flow path leading from a source inlet to a drain outlet; a plurality of heat exchangers arranged in said grey water flow path; a separator arranged upstream of said heat exchangers, arranged to separate grey water from the source inlet into a plurality of parallel sub-paths, each sub-path being lead to one of the heat exchangers; and a collector arranged downstream of said heat exchangers, arranged to reassemble the grey water from the sub-paths into a single flow path. Each heat exchanger comprises a grey water tube extending from the separator to the collector, and an outer tube surrounding at least a part of the grey water tube, the outer tube defining an annular space around the grey water tube. A fresh water flow path formed within the annular spaces around the grey water tubes in the heat exchangers has a flow direction being opposite to the flow direction of the grey water.

A refrigeration cycle device has a compressor, a radiator, an auxiliary heat exchanger, a decompressor, an evaporator, and an interior heat exchanger. The auxiliary heat exchanger performs a heat exchange between refrigerant and air and causes the refrigerant to radiate heat. The evaporator performs a heat exchange between air and refrigerant after being decompressed in the decompressor before the air is heated in the auxiliary heat exchanger. The interior heat exchanger has a first heat exchanging portion and a second heat exchanging portion and performs a heat exchange between refrigerant flowing in the first heat exchanging portion and refrigerant flowing in the second heat exchanging portion. The first heat exchanging portion is disposed in a refrigerant path between the radiator and the decompressor and is connected to the auxiliary heat exchanger in series. The second heat exchanging portion is disposed in a refrigerant path between the evaporator and the compressor.

A duct for a turbine engine, such as a gas turbine engine, can be utilized to carry a fluid from one portion of the engine to another. The duct can include a metallic tubular element having one of a varying wall thickness, a varying cross section, or a tight bend. Such a duct can be formed utilizing additive manufacturing or metal deposition on an additively manufactured mandrel.

A double pipe for a heat exchanger includes an inner pipe disposed in an outer pipe. In a straight-pipe portion of the double pipe, the inner pipe has a plurality of protruding parts extending in a helically offset manner along a longitudinal direction, an inner-circumferential surface of the outer pipe directly contacts the protruding parts, and outer-side channels are partitioned at a plurality of locations in a circumferential direction of the double pipe. The protruding parts are curved to protrude radially outward. In a cross section of the straight-pipe portion orthogonal to the longitudinal direction, the inner-circumferential surface of the outer pipe is circular, and an average value of D/L values of all the outer-side channels is 0.09-0.20, wherein D is defined as a maximum depth of each of the outer-side channels and L is defined as an arc length of each of the outer-side channels in the circumferential direction.

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 0, 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].

A heat exchanger comprising a shell having a first end and a second end, a first end plate and a second end plate defining a first volume with the shell that receives a first fluid therein, and at least one heat exchanger tube having a first end affixed to the first end plate and a second end affixed to the second end plate. The at least one heat exchanger tube extends through the second volume and including a cross-section defined by a plurality of lobes extending radially outwardly from the longitudinal center axis thereof. A first fluid passes through the first volume of the shell and a second fluid comprising a hot combustion gas passes through the at least one heat exchanger tube. The cross-section is constant along an entire length of the at least one heat exchanger tube.

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 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.

An inner pipe (2) is designed for a heat-transferring double pipe that exchanges heat between a fluid that flows through the interior of the inner pipe and a fluid that flows between the inner pipe and an outer pipe (10) that surrounds the inner pipe. The inner pipe has a first region (21) and a second region (22), which have transverse cross-sectional shapes that differ. The first region has a plurality of first protruding parts (211) that protrude outward and form a first recess-protrusion shape in which locations of the first protruding parts are offset helically in a longitudinal direction. The second region has a plurality of second protruding parts (221) that protrude outward and form a second recess-protrusion shape, in which locations of the second protruding parts are offset helically in the longitudinal direction. The number of second protruding parts is greater than the number of first protruding parts.