RU2100731C1 - Double-pipe heat exchanger - Google Patents

Abstract

FIELD: heat-power engineering; transport power engineering. SUBSTANCE: heat exchanger includes shell 1 with flat multi-passage twisted pipe 2 mounted inside it. Outer surfaces of passages are provided with system of hemispherical dimples 5 and 6 forming system of smooth projections inside passages of pipe 2 and shell 1; passages located on shell 1 are arranged spirally at twist angle equal to that of pipe 2. EFFECT: enhanced efficiency. 6 cl, 6 dwg

Description

 The invention relates to heat engineering and can be used in various industries, in particular in heat transfer equipment of transport energy with viscous heat carriers of high pressure in both paths.

Known heat exchangers of the "pipe in pipe" type (Bazhan P.I. et al. Handbook of heat exchangers. M. Mashinostroenie, 1989, p. 55, Fig. 1.15b), in which one heat carrier moves along the inner pipe and the other
along the annular space between the inner and outer pipes.

 To intensify heat transfer, as a rule, various constructive solutions are used in one of the tracts (ed. St. USSR N 328316, class F 28 F 1/10, F 28 D 7/10, 1/4/1970, ed. St. USSR N 510634, class F 28 D 7/10, 05/12/1974, aut. St. USSR N 642591, class F 28 D 7/10, 08/22/1977, aut. St. USSR N 659878, class F 28 D 7 / 10, 21.03.78, ed. St. USSR N 1702146, class F 28 D 7/10, 11.20.89), which have a relatively low energy efficiency associated with significant energy costs for pushing the coolant through the channel with activators located in it heat transfer.

 The closest in technical essence to the invention are heat-exchange elements in which screw-shaped profile tubes are used for the inner duct (Budov V.M. Dmitriev S.M. Forced heat exchangers NZU. M. Energoatomizdat, 1989, p. 50, 51, Fig. 3.6 , 3.8, p. 99, Fig. 5.1).

 Such heat exchangers are used for two-sided heating of a medium moving in an annular channel; therefore, there is no thermal contact between the pipes in them, or contact thermal resistance between them is quite large. With one-sided heat supply, the technical solution adopted reduces the compactness and energy efficiency of the heat exchanger.

 The aim of the invention is to increase compactness and reduce the mass of the heat exchanger.

The goal is achieved by the fact that the heat exchanger of the “pipe in demand” type, comprising a body and a flat multichannel swirl tube installed inside it, has a relief on their external surfaces in the form of a system of hemispherical dimples forming a system of smoothly defined protrusions inside the tube and housing channels, of which on the housing are arranged in a spiral with a twist angle Φ ₂ equal to the twist angle Φ _{1 of the} inner tube
Φ ₂ = Φ ₁ ,
end walls which fit snugly against the inner wall of the housing.

The twist angle Φ _{1 of the} flat tube is
Φ ₁ = arctan (H / πd ₁ ),
to ensure the assembly (disassembly) of the heat exchanger, the step of placing the protrusions along the inner wall of the housing is a multiple of the circumference of the inner diameter of the housing, has a value
S ₁ > (h + d _B2 ) / cosΦ ₂ ,
and the step along the spiral of their placement is greater than or equal to the diameter of the base of the protrusion
S ₂ ≥d _B2 ,
where H is the helix pitch of the twist of the inner tube;
h is the thickness of the inner swirling multi-channel tube;
S ₁ and S _{2 the} steps of the protrusions along the inner wall of the housing and along the helical axial lines of the protrusions;
d _{B2 the} diameter of the hemispherical protrusion on the inner wall of the housing;
Φ ₁ , Φ ₂ twist angles of the inner multi-channel tube and helical axial lines of the protrusions;
d ₁ inner diameter of the housing.

The height and diameter of the protrusions in the channels of the inner tube are related to the dimensions of these channels
h _B1 (0.4 0.16) d _E1 ,
d _B1 (0.55 0.8) b _K1 ,
where h _B1 , d _{B1 the} height and diameter of the protrusion in the channels of the inner tube;
d _E1 , d _K1 equivalent diameter, channel width of the inner tube.

The height and diameter of the hemispherical protrusions on the inner wall of the housing depend on the geometric dimensions of the channels formed by this wall and the outer surface of the swirling inner tube
h _B2 = (0.05 0.1) d _E2 ,
d _B2 = (10 20) h _B2 ,
where h _B2 , d _{B2 the} height and diameter of the protrusions on the inner wall of the housing;
d _{E2 is the} equivalent diameter of the channel between the housing and the inner tube.

The relative filling area of the outer surface of the inner tube with holes is 50-60%
With an increase in the relative density of the wells by more than 60%, the growth rate of the heat transfer coefficient decreases and the rate of increase in the hydraulic resistance of the channel increases markedly, which ultimately leads to a decrease in the energy efficiency of the heat exchanger (G. Kiknadze. Study of heat and mass transfer in the form of hemispherical holes on initially smooth surfaces. Report N 10774 from 10/18/86, IAE, TsIAM, KNPO Trud, p. 141).

 When the heat carrier moves in the internal channels of a flat tube, heat transfer is intensified due to swirling flow and vortex formation during the flow around a system of hemispherical protrusions, the size and shape of which provide a high heat transfer coefficient with low hydraulic resistance (G. Dreitser. Problems of creating compact tubular heat exchangers. Heat power N 3, 1995, p. 13, G. Kiknadze et al. Report, p. 142).

 The presence of partitions (ribs) dividing the living section of the tube into a series of channels leads to the development of the surface of its inner tract, which contributes to the growth of the effective heat transfer coefficient (Isachenko V.P. et al. Heat transfer. M. Energoizdat, 1981, p. 44).

 In the channel between the casing and the flat helical tube, the increase in heat transfer is caused by swirling the flow, vortex formation on the relief surfaces of the tube and the casing, and in this case the swirl stimulates vortex formation, providing preliminary swirling of the flow washing the hole or protrusion, thereby intensifying heat transfer. Good thermal contact between the end surfaces of the inner tube and the housing allows the latter to be used as an element for the development of the surface of the inner tube, which leads to a significant increase in the effective heat transfer coefficient. The same angle of rotation of the inner tube and the helical axial line of placement on the case of three-dimensional turbulators maintains a swirl of the flow along the entire length of the heat exchange element, which contributes to the intensification of heat transfer and allows to simplify the process of assembly (disassembly) of the heat exchanger.

 The use of multichannel flat tubes reduces the equivalent diameter of a single channel, and at high pressures of the internal environment it allows the use of tubes of aluminum alloys with a small wall thickness for the manufacture of a heat exchanger (Antikayn P.A. Metals and calculation of the density of boilers and pipelines. M. Energy, 1980. S. 339; Aleksandrov V. G. Bazanov B. I. Handbook of Aviation Materials and the Technology of Their Application. M. Transport, 1979, with 47, 48 and 49), which significantly reduces the mass of the heat exchanger as a whole.

 Thus, the combination of different methods of turbulization of the fluid flow used leads to the stimulation of vortex formation when flowing around the holes and smoothly defined protrusions swirl the flow, which is additionally with high energy efficiency (Belenky M. Ya. Et al. Thermohydraulic characteristics of transversely streamlined surfaces with holes. Thermal engineering, N 1, 1994, p. 49; Kuznetsov EF Intensification of heat transfer in the channels of GTU air heaters. Heavy Engineering, N 6, 1991, p. 9, Fig. 3) intensifies heat transfer and is a effect of the considered technical solution.

 In FIG. 1 and 2 show a longitudinal section and a cross section of a heat exchanger; in FIG. 3 and 4 placement of holes and protrusions on the inner tube; in FIG. 5 and 6, a scan of a portion of the surface of the housing with the location of the protrusions and a section of one of them with an indication of its main dimensions.

The pipe-in-pipe type heat exchanger comprises a housing 1 and a flat multichannel swirl tube 2 installed in it, has a relief on their outer surfaces 3 and 4 in the form of a system of hemispherical holes 5 and 6, forming a smoothly outlined system inside the channels 7 and 8 of the tube and the housing protrusions 9 and 10, of which 9 located on the housing 1 are arranged in a spiral with a twist angle Φ ₂ equal to the twist angle Φ _{1 of the} inner tube.

торцевые стенки 11 которой плотно прилегают к внутренней стенке 12 корпуса, шаг размещения выступов 9 по которой выполнен кратным внутреннему диаметру корпуса и имеет величину
S₁ > (h+d_в2)cosΦ₂,
а шаг вдоль спирали их размещения больше или равен диаметру основания выступа
S₂≥d_В2,
где H шаг винтовой линии закрутки внутренней трубки;
h толщина внутренней закрученной многоканальной трубки;
S₁ и S₂ шаги выступов по окружности внутренней стенки корпуса и вдоль винтовых осевых линий размещения выступов;
d_В2 диаметр полусферического выступа на внутренней стенке корпуса;
Φ₁, Φ₂ углы закрутки внутренней многоканальной трубки и винтовых осевых линий размещения выступов;
d₁ внутренний диаметр корпуса.

end walls 11 which fit snugly against the inner wall 12 of the housing, the pitch of the protrusions 9 along which is a multiple of the inner diameter of the housing and has a value
S _1> (h + d _c2) cosΦ ₂
and the step along the spiral of their placement is greater than or equal to the diameter of the base of the protrusion
S ₂ ≥d _B2 ,
where H is the helix pitch of the twist of the inner tube;
h is the thickness of the inner swirling multi-channel tube;
S ₁ and S _{2 the} steps of the protrusions around the circumference of the inner wall of the housing and along the helical axial lines of the protrusions;
d _{B2 the} diameter of the hemispherical protrusion on the inner wall of the housing;
Φ ₁ , Φ ₂ twist angles of the inner multi-channel tube and helical axial lines of the protrusions;
d ₁ inner diameter of the housing.

The height and diameter of the protrusions 10 in the channels 7 of the inner tube are associated with the geometric dimensions of these channels
h _B1 = (0.04 0.16) d _E1 ,
d _B1 = (0.55 0.8) b _K1 ,
and the height and diameter of the protrusions 9 on the inner wall 12 of the housing depend on the geometric dimensions of the channels 8 formed by this wall and the outer surface 4 of the swirling inner tube 2
h _B2 = (0.05 0.1) d _E2 ,
d _B2 = (10 20) h _B2 ,
where d _{1 the} inner diameter of the housing
h _B1 , d _{B1 the} height and diameter of the protrusion in the channels of the inner tube;
d _E1 , d _K1 equivalent diameter, channel width of the inner tube;
h _B2 , d _{B2 the} height and diameter of the protrusions on the inner wall of the housing;
d _{E2 is the} equivalent diameter of the channel between the housing and the inner tube;
h the thickness of the inner swirling multi-channel tube.

The relative filling area of the outer surface of the inner tube with holes is 50-60%
During the operation of the heat exchanger, one heat carrier (arrow 13) enters the channels 7 of the swirling inner tube 2, twists, washes the surface of the smoothly defined protrusions 10 and is removed from the inner tube (arrow 14).

 The second heat carrier (arrow 15) is sent to the channels 8 between the housing 1 and the inner tube 2, twisted by the last and smoothly outlined protrusions 9 and helically placed on the housing and, washing the relief surfaces of the housing and the inner tube, it is removed (arrow 16) from the heat exchanger.

 The technical and economic effect of the invention lies in the fact that due to the intensification of heat transfer in the channels of the inner tube and the housing, the heat transfer coefficient increases, therefore, with a constant heat flow, the surface of the heat exchanger decreases, the compactness of the heat exchanger increases, and its mass decreases.

Claims (5)

1. A pipe-in-pipe type heat exchanger comprising a housing and a flat multi-channel twisted tube installed in it, characterized in that it has a relief in their outer surfaces in the form of a system of hemispherical dimples, forming a system of smoothly defined protrusions inside the channel of the tube and the housing, of which the housing is arranged in a spiral with a twist angle Φ ₂ equal to the twist angle Φ _{1 of the} inner tube Φ ₂ = Φ ₁ .
2. The heat exchanger according to claim 1, characterized in that the end walls of the flat tube fit snugly against the inner wall of the housing. 3. The heat exchanger according to claim 1, characterized in that the angle Φ _{1 of the} twist of the flat tube is
Φ ₁ = arctan (H / πd ₁ ),
the pitch of the protrusions on the inner wall of the housing is a multiple of the circumference of the inner diameter of the housing, has a value
S ₁ > (h + d _B2 ) / cosΦ ₂ ,
and the step along the spiral of their placement is greater than or equal to the diameter of the base of the protrusion
S ₂ ≥ d _{in 2} ,
where H is the pitch of the helix of the twist of the inner tube;
h is the thickness of the inner swirling multi-channel tube;
S ₁ , S ₂ steps of the protrusions on the inner wall of the housing and along the helical axial lines of the protrusions;
d _{in 2 the} diameter of the hemispherical protrusion on the inner wall of the housing;
Φ ₁ , Φ ₂ - twist angles of the inner multi-channel tube and helical axial lines of the protrusions;
d ₁ inner diameter of the housing. 4. The heat exchanger according to claims 1 to 3, characterized in that the height and diameter of the protrusions in the channels of the inner tube are related to the dimensions of these channels
h _{in 1} (0.04 0.16) d _{e 1} ;
d _{at 1} (0.55 0.8) b _{to 1} ,
where h _{in 1} , d _{in 1} height and diameter of the protrusion in the channels of the inner tube;
d _{e 1} , b _{to 1} equivalent diameter and channel width of the inner tube. 5. The heat exchanger according to claims 1 to 4, characterized in that the height and diameter of the hemispherical protrusions on the inner wall of the housing depend on the geometric dimensions of the channels formed by this wall and the outer surface of the twisted inner tube
h _{in 2} (0.05 0.1) d _{e 2} ;
d _{at 2} (10 20) h _{at 2} ,
where h _{in 2} , d _{in 2 the} height and diameter of the protrusions on the inner wall of the housing;
d _{e 2} equivalent diameter of the channel between the housing and the inner tube.  6. The heat exchanger according to claims 1 to 5, characterized in that the relative filling area with holes in the outer surface of the inner tube is 50-60%

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