TECHNICAL FIELD

The invention relates to the heat engineering field specifically to heat exchangers with ribbed tubes and can be used in air coolers, heat exchangers, refrigerators, recuperators, furnaces which are applied to different fields of industry.

PREVIOUS TECHNICAL KNOWLEDGE

Heat-exchange machines are known tocontaina body, input and outputcollectors and a bundle of heat exchange straight tubes (A.G. Kasatkin, Main processes and chemical engineering machines. Alliance Publishing House, Moscow, 2008, p. 326-333). The Main disadvantages of the specified structures are insufficiently intensive heat exchange due to low heat transfercoefficient due to low flow turbulence passing both inside tubes and in intertubularspace, high material consumption and significant external dimensions.

Heat-exchange machines are known to containa body, input and outpute collectorsand a bundle of heat exchange straight tubes in the form of spatial and spiral coils installed in clearances between their laps (RF patents No. 2152574 F28D 7/02 dd 16.09.1999 and No. 2238500 F28D 7/02 dd 27.12.2002 Main disadvantages of the specified structures are complexity of coilproduction, formation of tube bundles in intertubular space, heat exchange between spacesis insufficiently intensive especially in intertubularspace, low heat transfer coefficient at 150 kkal/x*m ² ("Heat-exchange equipment of "ANOD-TTS" LLC"").

Heat-exchange machines are known to containa body, inlet and outlet collectorsand coiled tubing elements installed in clearances between coiled element laps (RF patents No. 2451875 F22B37/00, F28D7/02 dd 14.10.2010). The main disadvantage of the specified structure is insufficiently intensive heat exchange between spacesespecially duringmovement of heat-transfer sphere outside the coiled elements across the tube bundle axis and production of coiled tube bundles by means of insertion of one tube bundle into the other bundles.

The most technicallycloser to mentioned invention and achieved result is the heat exchanger with ribbed tubes, in particular an air cooler containing a body, input and output collectors with hot and cold flow input and output devices and a bundle of heat exchange straight ribbedtubes (Basis of calculation and design of air-cooling heat exchangers: Reference book, A.N. Bessonov, G.A. Dreitser, V.B. Kuntysh et al. St. Petersburg, "Nedra", 1996, p. 89-104). Main disadvantages of the specified structure is insufficiently intensive heat exchange due to low flow turbulence taking place inside the straight tubes and low heat transfer coefficient from the wall to the flow inside tubes limiting the total heat transfer coefficient. DISCLOSURE OF INVENTION

The task which shall be solved by the mentioned invention is efficient heat exchangeboth in tube side and intertubular spaceof ribbed heat exchange tube bundles with simultaneous increasing of specific area of heat exchange.

This task is solved due to the fact that in the heat-exchange machine with ribbedheat- exchange tubes, which includs a body, input and output collectorswith hot and cold flow inlet and outlet devices, at least one finned heat-exchange tube or a bundle of ribbed heat-exchange tubes according to the invention the ribbed heat-exchange tube with d diameter is made in the serpentine form with ribbingat the external surface of the serpentine-formed tube with D external ribbing diameter and LI ribthickness located at the heat-exchange serpentine-formed ribbed tube at L2 distance from each other and upon that the A serpentine amplitude of heat-exchange ribbed tube at the exterior diameter of ribbing is not less than A = D ( 2 + _{LI +} L ₂ ), and wave period of

LI ¹

P serpentine is not less than P = 2D ( 1 + _{Ll + L2} ).

Ll ¹

The heat exchange machine with ribbed heat-exchange tubes can be producedwith ribbing ofserpentine-formed heat-exchange tube representing rings with Ll length with D exterior diameter and internal diameter equal to exterior diameter d of heat-exchange tubes located at the serpentine-formed ribbed heat-exchange tube at L2 distance from each other which unifies equipment for manufacturing of ribbing and cuts down costs for producingof serpentine- formed ribbed heat-exchange tube.

The heat exchange machine with ribbed heat-exchange tubes can be made with ribbing with serpentine-formed heat-exchange tube representing vanes with Ll thickness with D exterior diameter and internal diameter equal to exterior diameter d of heat-exchange tubes with distance between the neighboring vanes equal to the vane base length, with L2 distance between the vane ranges which intensifies the flow turbulence in intertubular space due to the fact that vane edges cut the flow in the intertubular space ensuring formation of vortex in it resulting in alignment of temperature field.

The heat exchange machine with ribbed heat-exchange tubes can be made with ribbing with serpentine-formed heat-exchange pipe representing pins with Ll thickness and D-d height, with Ll distance between the neighboring pins and L2 distance between the pin rangeswhich simplifies production technology of ribbing and reduces itsmaterial consumption.

The heat exchange machine with ribbed heat-exchange tubes can be made with ribbing with serpentine-formed heat-exchangetube representing spiral tape with Ll thickness with surface passed by the Archimedean spiral, with tape width equal to D-d, with L2 distance between the spiral tape coils from each other which ensures swirling in intertubular space and increases velocity of this flow resulting in additional increase of heat-transfer coefficient to the exterior surface of the serpentine-formed heat-exchange tube.

The heat exchange machine with ribbed heat-exchange tubes can be made with ribbing with serpentine-formed heat-exchange tube representing elliptical plates with LI thickness located with eccentricity so to the serpentine-formed heat-exchange tube ,so that the axis of the serpentine-formed heat-exchange tube coincides with on of the centers of the elliptical plate with maximum distance from the exterior wall of the serpentine-formed heat-exchange tube d to the top of the elliptical plate D and located at the serpentine-formed ribbed heat-exchange tube at L2 distance from each other which enables to increase the ribbing surface and heat transfer between the tubular side and intertubular space of the heat-exchange machinerespectively.

The heat-exchange machine with ribbed heat-exchange tubes can be made ribbing with serpentine-formed heat-exchange tube representing elliptical plates installed at the serpentine- formed heat-exchange tube so thatthe maximum distance from the exterior wall of the serpentine-formed heat-exchange tube to the top of the elliptical plate D is oriented towards the serpentine crest and in the area of the serpentine cavity the maximum distance from the exterior wall of the serpentine-formed heat-exchange tube to the top of elliptical plate D is oriented towards the serpentine cavity; upon that maximum use of internal space of the heat-exchange machine is provided due to increase of bend numbers of serpentine-formed heat-exchange tube resulting in increase of heat-exchange surface per unit length of the heat-exchange machine, additional flow turbulence in tube side and, as the result - to increase of coefficient of heat transfer.

The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbing of the serpentine-formed heat-exchange tube, with square form in cross-section which simplifies formation of ribbing due to pressure continuity of roller facilities to the wrought metal layer applied to the exterior surface of the serpentine-formed heat-exchange tube.

The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbing of the serpentine-formed heat-exchange tube, with trapeze form in cross-section with wide base at the exterior wall of the heat-exchange tube which enables to increase ribbing height with simultaneous improvement of its mechanical strength.

The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbing of the serpentine-formed heat-exchange tube, with alternating variable cross-section rectangles form in cross-section with wide base at the exterior wall of the heat-exchange tube and successively decreasing in proportion to movement away from the heat-exchange tube wall. The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbing of the serpentine-formed heat-exchange tube located at the heat-exchange tube wall in parallel to each other during application of the ribbing to the initially straight heat-exchange tube.

The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbing of the serpentine-formed heat-exchange tube located at the heat-exchange tube wall perpendicularly to axis of the heat-exchange tube during application of the ribbing to the initially serpentine- formed heat-exchange tube

The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbing of the serpentine-formed heat-exchange tube performed by welding of the ribbing element to the exterior surface of the serpentine-formed heat-exchange tube in case when material of ribbing and tube is homogeneous.

The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbing of the serpentine-formed heat-exchange tube performed by extrusion from the wrought material layer applied to the exterior surface of the serpentine-formed heat-exchange tube in case when the tube is made of bimetal with exterior layer of deformed metal.

Aluminum or aluminum-based alloys can be used as the wrought metal applied to the exterior surface of the serpentine-formed heat-exchange tube which reduces material consumption of the heat-exchange machine.

Copper or copper-based alloys can be used as the wrought metal applied to the exterior surface of the serpentine-formed heat-exchange tube which increases thermal conductivity of ribbing and its resistance toaggressive environments.

The heat-exchange machine with ribbed heat-exchange tubes can be made by bending prefabricated ribbed straight heat-exchange tube which significantly simplifies manufacturing technique of the heat-exchange machine.

The heat-exchange machine with ribbed heat-exchange tubes can be made by ribbing of bent straight heat-exchange tube which enables to form original non-standard designs of the heat-exchange machines.

The heat-exchange machine with ribbed heat-exchange tubes can be made with ribbed serpentine-formed heat-exchange tube, with coil form with long sections and transition zones with change of flow movement direction in the tube which enables to use similar heat-exchange machines as the structural element of the convection chamber of pipe furnace or coil-in-box condenser - box-type refrigerator. The heat-exchange machine with ribbed heat-exchange tubes made in the coil form can be without ribbing in transition zones with change of flow movement direction in the tube which simplifies its application as the structural elements of the convection chamber of pipe furnace.

The heat-exchange machine with ribbed heat-exchange tubes made in the coil form and without ribbing in transition zones with change of flow movement direction in the tube can be made with location of transition zones outside the body e.g. in a convection chamber of a pipe furnace.

During flow passing in intertubular space of the heat-exchange machine with ribbed heat- exchange tubes in parallel to the bundle of the ribbed serpentine-formed heat-exchange tubes the body of the heat-exchange machine can be also in the serpentine form repeating the form of the bundle of the ribbed serpentine-formed heat-exchange tubes which eliminates available zones with absence of heat transfer between the heat exchanging flows and increases flow velocity in intertubular space of the heat-exchange machine resulting in increase coefficient of heat transfer in intertubular space of the heat-exchange machine.

Upon flow passing in intertubular space of the heat-exchange machine with ribbed heat- exchange tubes perpendicularly to the bundle of the ribbed serpentine-formed heat-exchange tubes the bundle of the ribbed serpentine-formed heat-exchange tubes can be located in the body in horizontal plane of serpentine formation and the body of the heat-exchange machine can be also made in the serpentine form repeating the bundle form of the ribbed serpentine-formed heat- exchange tubes.

Making the bundle of ribbed heat-exchange tubes in the serpentine form using tube bends in the vertical or horizontal plane enables to create turbulence for the flow passing inside the tube. The serpentine form of the tubes of the ribbed heat exchange tube bundle results in velocities of local flow currents inside tubes becoming variable where in the tube bend area at the section internal as to the bend the local velocities decrease and at the outer sections they increase which results in flow turbulence due to non-uniformity of speed behavior of local currents and then upon flow transition to the area of the next bend the local current pattern is changed to the opposite one.

The flow turbulence is highly effective method of heat transfer enhancement as it allows increasing the coefficient of heat transfer with low growth of flow resistance. Upon excessive distance between the tube bends (high serpentine wave amplitude) the turbulence originated at the tube bend fades out and the rest tube section up to the next bend will be slightly different by flow structure from the straight tube. So the serpentine wave amplitude of the ribbed heat exchange tube bundle at A disc tops shall minimum so far as it is allowed by the design of the ribbed serpentine-formed tube and upon that it can not be less than A = D x ( 2 + _{Ll +} ),

CI ¹ and P wave period shall be respectivelynot less than P = 2D x ( 1+ rrrn— )■

Ll ¹

When making the ribbed heat exchange tube bundle in the serpentine form in addition to turbulence of the flow passing inside tubes as compared to straight ribbed tubes used in a prototype the length of the ribbed tubes located in the same body of the machine is increased due to bends and the area of heat exchangerespectively increases

When making the ribbed heat exchange tube bundle in the serpentine form in the horizontal plane it is appropriate to make the body of the heat exchange machine in the serpentine form also in the vertical plane. In this case the cavities in the body are closed and the heat exchange intensifies.

The achieved technical result is intensification of heat exchange due to turbulence of the flow passing inside the ribbed heat exchange tubes made in the serpentine form in the vertical or horizontal plane, the heat exchange area increases at the same time as compared to the prototype using straight ribbed tubes.

LIST OF DRAWINGS

The invention is explained by figures 1-8:

a bundle of the ribbed heat exchange tubes in the serpentine form in the vertical plane is represented in figure 1 ;

a bundle of the ribbed heat exchange tubes in the serpentine form in the horizontal plane is represented in figure 2;

a structural fragment of the ribbed heat exchange tube 25 mm diameter with 55 mm ribbing diameter, 1 mm ribthickness and 3.5 mm ribspacing made in the serpentine form in the vertical plane is represented in figure 3;

a photo of experimental-industrial heat exchange section with the ribbed heat exchange tube bundle in the serpentine form in the horizontal plane is represented in figure 4;

a photo of a fragment experimental-industrial heat exchange section with the ribbed heat exchange tube bundle in the serpentine form in the horizontal plane is represented in figure 5; a fragment of the convection chamber of pipe furnace with the coil made of ribbed serpentine-formed heat exchange tubes not ribbed in transition zones is represented in figure 6; a refrigerator with the ribbed heat exchange tube bundle in the serpentine form in the horizontal plane (top view and axonometric perspective) in represented in figure 7;

a refrigerator with the ribbed heat exchange tube bundle in the serpentine form in the horizontal plane (top view and axonometric perspective) in represented in figure 8. In figures 1 -2, 6-8: 1 - bundle of ribbed serpentine-formed heat exchange tubes, 2 - ribbed serpentine-formed heat exchange tube, 3 - chamber, 4 - inlet nozzle, 5 - outlet nozzle.

In figure 3: 1 - serpentine-formed heat exchange tube, 2 - fins.

BRIEF DESCRIPTION OF DRAWINGS

According to figure 1 and 8 the bundle of the ribbed serpentine-formed heat exchange tubes 1 consists of ribbed heat exchange tubes 2 in the serpentine form in the vertical plane, chambers 3 with inlet nozzle 4 and outlet nozzle 5 are installed from opposite sides of the serpentine-formed tubes.

According to figure 2 and 7 the bundle of the ribbed serpentine-formed heat exchange tubes 1 consists of ribbed heat exchange tubes 2 in the serpentine form in the horizontal plane, chambers 3 with inlet nozzle 4 and outlet nozzle 5 are installed from opposite sides of the serpentine-formed tubes.

According to figure 3 fins 2 at the serpentine-formed heat exchange tube 1 due to design features have different distances between the ribtops.

Heat exchange machines with installed bundle of the ribbed serpentine-formed heat exchange tubes work as follows.

A bundle of the serpentine-formed ribbed heat exchange tubes 1 is installed in the heat exchange section of a standard air cooler with available fan and diffuser with collection for air supply. The body of the heat exchange section as shown in figures 4 and 7 is made in the serpentine form in the horizontal plane repeating the serpentine form of ribbed tubes 2. Such design prevents air flow breakthrough through the space formed upon installation of ribbed tubes in the serpentine form in the horizontal plane. Air flow is directed by the fan via the diffuser to the exterior surface of the ribbed serpentine-formed heat exchange tubes 2 passing through the bundle of ribbed heat exchange tubes 1. Air flow removes heat of the cooled space passing through tubes 2 due to which air is heated and removed from the machine. The cooled spacecan be liquids, gases and condensable vapors which are fed through the inlet nozzle 4 installed in the chamber of heat exchange section 3 in bundle 1 consisting of serpentine-formed ribbed heat exchange tubes 2. Moving in internal channels of tubes 2 the space is cooled and removed through outlet nozzle 5. Making the ribbed tube in the serpentine form unlike the straight tube of the prototype results in increase of heat exchange area due to tube elongation and additional intensification of heat exchange caused by flow turbulence of the cooled space. A bundle of ribbed heat exchange tubes made in the serpentine form both in the vertical (figures 2. 8) and in the horizontal plane (figures 1, 7) can be used for gas cooling. A bundle of ribbed heat exchange tubes made in the serpentine form in the horizontal plane shall be used for liquid cooling, for provision of tube discharge upon shutdown and repair of the air cooler. A bundle of ribbed heat exchange tubes made in the serpentine form in the horizontal plane shall be used for vapor cooling and condensation to eliminate formation of liquid plugs in tube bend points and to ensure tube discharge upon shutdown and repair of the air cooler.

Upon application of the bundle of the ribbed serpentine-formed heat exchange tubes 1 for process flow heating e.g. in pipe furnaces the bundle is installed in the body of the machine with inlet and outlet channels for supply of gaseous heat carrier. The heat carrier is flue gases formed upon fuel burning in electric power installations (furnaces, gas turbine plants etc.) which come inside the machine body through the inlet channel and passing over the external surface of the ribbed serpentine-formed heat exchange tubes 2 from all sides give up their heat to the heated space passing inside tubes 2 in consequence of which they are cooled and removed from the machine through the outlet channel of the machine. The heated space are liquids and gases which are fed through the inlet nozzle 4 installed in the chamber of heat exchange section 3 in bundle 1 consisting of serpentine-formed ribbed heat exchange tubes 2. Moving in internal channels of tubes 2 the heated space takes heat from the heat carrier, heated and removed through outlet nozzle 5. Making the ribbed tube in the serpentine form unlike the straight tube of the prototype results in increase of heat exchange area due to tube elongation and additional intensification of heat exchange caused by flow turbulence of the heated space. A bundle of ribbed heat exchange tubes made in the serpentine form both in the verticaland in the horizontal plane can be used for gas heating. A bundle of ribbed heat exchange tubes made in the serpentine form in the horizontal plane shall be used for liquid heating, for provision of tube discharge upon shutdown and repair of the machine. In the same way the ribbed serpentine-formed heat exchange tubes 1 are installed instead of straight sections of tubing coil in the convection chamber of heating furnaces as shown in figure 1.

A bundle of the serpentine-formed ribbed heat exchange tubes 1 can be also installed inside the body of the box cooler with available nozzles for inlet and outlet of cooling space e.g. recycling water. The coolant via inlet nozzle enters inside the body of the box cooler passing over the external surface of the ribbed serpentine-formed heat exchange tubes 2 from all sides, removes excessive heat from the cooled spacepassing inside tube 2 and removed from the machine via the outlet nozzle. The cooled space can be liquids, gases and condensable vapors which are fed through the inlet nozzle 4 installed in the chamber of heat exchange section 3 in bundle 1 consisting of serpentine-formed ribbed heat exchange tubes 2. Moving in internal channels of tubes 2 the space is cooled and removed through outlet nozzle 5. Making the ribbed tube in the serpentine form unlike the straight tube of the prototype results in increase of heat exchange area due to tube elongation and additional intensification of heat exchange caused by flow turbulence of the cooled space. A bundle of ribbed heat exchange tubes made in the serpentine form both in the vertical (and in the horizontall plane can be used for gas cooling. A bundle of ribbed heat exchange tubes made in the serpentine form in the horizontal plane shall be used for liquid cooling, for provision of tube discharge upon shutdown and repair of the air cooler. A bundle of ribbed heat exchange tubes made in the serpentine form in the horizontal plane shall be used for vapor cooling and condensation to eliminate formation of liquid plugs in tube bend points and to ensure tube discharge upon shutdown and repair of the air cooler.

Dimensions of the ribbed heat exchange tube in the serpentine form are represented in figure 3 according to the proposed invention. The ribbed heat exchange tube d=25 mm is made in the serpentine form with ribbing at the external surface of the serpentine-formed tube with external diameter of ribbing D=55 mm and ribthickness Ll=l mm located at the ribbed serpentine-formed heat exchange tube at L2=3,5 mm spacing and upon that the serpentine amplitude of the ribbed heat exchange tube to external diameter of ribbing is A=155 mm, according to the proposed invention this value shall benot less than

A = 55 x (2 +T+ 3^ ) ⁼ 125,7mm, and wave period of the serpentine P=200 mm, according to

l ¹

the proposed invention this value shall be not less then P = 2D x (1+ _L I + L2 ) ⁼

Ll ¹ =2x55 x (1 + _{1 +} ) = 141,4 mm.

l ¹

Comparison of the air-cooled heat exchanger produced according to the proposed invention (fig. 4) with the known heat exchange machine using the heat exchange section with straight tube with welded ribbing has confirmed higher efficiency of the proposed heat exchange machine and shown that water is cooled to 1-4 °C below, outgoing air temperature is by 5-6 °C higher, tube length and heat exchange surface area in 1.23 bigger than the prototype. Test results are represented in table 1 and 2. The section

with the straight The section with the

Item pipe and serpentine beading welded fins in pipe in this invention prototype

Size, mm Width 400, length 2000, height 350

Serpentine

Sidewalls Gentle

configuration

Package of The lid is

The lid is divided by section divided by a

The lid and holed a curved baffle baffle

baffle

Performed three consecutive moves liquid to 12 pipes in each turn

Material and

Steel welded

beading

Surface roughness

8 8 factor

Package of Diameter of ribs,

47 47 beading mm

Pitch between ribs,

1 1 mm

Thickness of ribs,

1 1 mm

Diameter 20,

Size, mm

wall thickness 2,5

Amplitude of serpentine 100 mm

Package of pipe Straight

Period serpentine 300 mm

Number of pipes

12/36 (checkered) during liquid/total

Package of

Length of one pipe,

pipe 2000 2460

mm

Number of

(vertical) moves 3 section

Length stroke of

6,00 7,38 liquid, m

Total length of

72,00 88,60 pipes, m

Surface area of pipe, m 50,40 62,00

Table 1 The section with the

The section with the straight pipe and

Item serpantin beading pipe

welded fins in

in this invention prototype

Rate of throughput,

3,7 5,0 10,0 3,7 5,0 10,0 m ³ /h

Pressure drop, kPa Not more than 15,0 Not more than 21 ,0

Cooling

environment Inlet temperature, °C 73

-water

Outlet temperature, °C 63 65 66 59 62 65

Temperature drop, °C 10 8 7 13 1 1 8

Rate of throughput,

12,5

m ³ /h

Pressure drop, kPa Not more than 0,68

Heated

environment Inlet temperature, °C 30

-air

Outlet temperature, °C 53-55 59-60

Temperature drop, °C 23-25 29-30

Table 2

Thus making the ribbed heat exchange tubes in the serpentine form results in heat exchange intensification due to turbulence of flow passing inside the ribbed heat exchange tubes and in increasing of heat exchange area of the machine.