CN201289323Y - Fin type heat exchanger for natural convection - Google Patents

Abstract

A finned heat exchanger for natural convection comprises two cold/hot medium inlet/outlet pipes communicated with an external pipeline; a heat exchange tube is communicated with the two inlet-and-outlet pipes; the heat exchange tube is in contact with heat exchange fins; the heat exchange tube and the heat exchange fins all adopt a layered structure; a clearance is reserved between every two layers; and layers of the heat exchange tube are communicated with each other through connecting elbows connected in series. By adopting the technical scheme, the heat exchanger for natural convection, which is provided by the utility model, has the beneficial effects that clearances are arranged among the heat exchange fins, so that natural convection during heat exchange is increased, and the heat exchange efficiency is high; different heat exchange fin materials can be used according to different application environments, so that the material selection is convenient, and the material consumption amount of the whole heat exchanger is reduced; the cost of the heat exchanger is further reduced; and the heat exchanger has a compacter structure, and the installation and the fixation are easier.

Description

A kind of free convection finned heat exchanger

Technical field

The utility model relates to a kind of heat exchanger, a kind of free convection finned heat exchanger of more specifically saying so.

Background technology

The heat exchanger that free convection is used in the actual engineering generally is coiled or shell and tube.Free convection coil exchanger in the outside is coiled into the spring shape to light pipe, inside and outside rib-type heat exchanger tube and carries out heat exchange, and the technology of this its making of structure is simple, but structure is not compact, and volume is big, the big and fixing difficulty of consumable quantity.Free convection tubular heat exchanger in the outside is that light pipe, inside and outside rib-type heat exchanger tube are made up by row and column, couple together with elbow again, this structure is with respect to coil exchanger, though structure is compact many, fixing also easy, but because of there being numerous elbows to connect, the technology relative complex a little, consumptive material is also big.

The utility model content

The utility model has overcome deficiency of the prior art, and a kind of heat exchange efficiency height, free convection heat exchanger that cost is low are provided.

In order to solve the problems of the technologies described above, the utility model takes following mode to realize:

A kind of free convection finned heat exchanger, comprise two cold and hot medium turnover pipes that are communicated with exterior line, be communicated with heat exchanger tube between the two turnover pipes, heat exchanger tube contacts with heat exchange fin, heat exchanger tube and heat exchange fin are hierarchy, leave the gap between each layer, be communicated with by the bridge piece series connection between each layer heat exchanger tube.

In order to increase contact area between heat exchanger tube and the heat exchange fin, improve heat exchange efficiency, heat exchanger tube laterally is interspersed in the heat exchange fin, and is expanded joint or welding between heat exchanger tube and the heat exchange fin.

In order to increase the turnover tubular elastic, the turnover pipe is provided with U type bending section.

Above-mentioned heat exchange fin is plate or ripple type or flap type.

Be fixed on the exterior object for the ease of each positioning parts and with whole heat exchanger, the heat exchanger tube sheet of fixing each heat exchange fin and heat exchanger tube is arranged in the heat exchange fin arranged outside.

Owing to adopt technique scheme, the free convection that the utility model provides has such beneficial effect with heat exchanger: between each heat exchange fin the gap is set, NATURAL CONVECTION COEFFICIENT OF HEAT when having increased heat exchange, the heat exchange efficiency height can adopt different heat exchange fin materials according to different applied environments, and selection is convenient, reduced the consumable quantity of whole heat exchanger, also further reduced the cost of heat exchanger, and more compact structure, also easier installing and fixing.

Description of drawings

Accompanying drawing 1 is the utility model embodiment cross section structure schematic diagram;

Accompanying drawing 2 is a present embodiment plan structure schematic diagram;

Accompanying drawing 3 is looked up structural representation for present embodiment;

Accompanying drawing 4 is a present embodiment left side TV structure schematic diagram.

The specific embodiment

For the ease of it will be appreciated by those skilled in the art that the utility model is described in detail below in conjunction with embodiment and accompanying drawing:

Shown in accompanying drawing 1～4, the heat exchanger that present embodiment disclosed is the free convection finned heat exchanger.This heat exchanger comprises heat exchange fin 1, is interspersed with heat exchanger tube 3 in heat exchange fin 1, and heat exchanger tube 3 is by realizing cold and hot medium circulation by turnover pipe 4,6 and exterior line.Wherein heat exchanger tube 3 laterally is interspersed in the heat exchange fin 1, in order to guarantee to be connected firmly between the two and bigger contact area, is welding or expanded joint between heat exchanger tube 3 and the heat exchange fin 1.In order to increase the elasticity of two turnover pipes 4,6, on two turnover pipes, be provided with U type bending section 41,61, this version had both strengthened the elasticity of turnover pipe, be convenient to produce to install, U type bending section can absorb the expand with heat and contract with cold distortion that produced of turnover pipe and destroys the turnover pipe to avoid expanding with heat and contract with cold or destroy heat exchanger or destroy turnover pipe fixture simultaneously.

Heat exchanger tube 3 and heat exchange fin 1 in this programme are hierarchy, all leave the gap between each layer, are communicated with by bridge piece 5 series connection between each layer heat exchanger tube 3.With many mutual heat exchanger tubes arranged side by side 3 can be set in one deck equally, each layer gone up same position place heat exchanger tube and then is together in series by bridge piece 5, forming existing parallel connection has the pipeline form of series connection again, has improved the heat exchange of cold and hot medium and heat exchange fin 1 in the heat exchanger tube 3.

For each component locations is fixed, the heat exchanger tube sheet 7 of fixing each heat exchange fin and heat exchanger tube 3 is arranged in heat exchange fin 1 arranged outside.Heat exchange tube sheet 7 can be fixed in whole heat exchanger on the exterior object by screw equally.

In the present embodiment, heat exchange fin 1 structure is a tabular, in addition also can be ripple type or flap type, and these shapes have good and heat exchange fin 1 extraneous gas or liquid heat-exchange ability equally.

In actual use, can adopt different Heat Conduction Materials according to different environment for use for heat exchange fin 1: 1) heat exchange fin 1 should be selected and heat exchanger tube 3 identical material when having electrochemical corrosion possible, as with cold-producing medium heating or cooling water the time, when heat exchanger tube 3 adopted copper pipe, heat exchange fin 1 should adopt copper fin; (2) when not having electrochemical corrosion, can select the cost of suitable heat exchange fin material with further reduction heat exchanger, during as water condensating refrigerant steam, when heat exchanger tube 3 adopted copper pipe, heat exchange fin 1 can adopt the aluminium fin to reduce the heat exchanger cost.

For heat transfer free convection, the coefficient of heat transfer of free convection side is lower, it is often far below the forced-convection heat transfer side coefficient of heat transfer, therefore if can increase the coefficient of heat transfer of heat transfer free convection side, often can increase considerably total coefficient of heat transfer, under the situation of same heat exchange amount, can reduce the consumption of materials of heat exchanger significantly.Heat transfer free convection surface coefficient of heat transfer computing formula is as follows:

$h=\frac{\mathrm{\λ}}{l}\mathrm{Nu}$ (formula 1)

Wherein: h---free convection surface coefficient of heat transfer, W/ (m ².K);

λ---the thermal conductivity factor of free convection fluid, W/ (m.K);

L---characteristic length, for the heat transfer free convection of perpendicular wall, it is the height of perpendicular wall, m;

Nu---nusselt number, the temperature of zero dimension gradient of fluid on the wall.

Nu=0.59 * (GrPr) ^0.25(formula 2)

Wherein: Gr---grashof number, a kind of tolerance of buoyancy lift and the ratio of stickiness power;

Pr---Prandtl number, a kind of tolerance of momentum diffusivity and the ratio of heat diffusion ability.

$\mathrm{Gr}=\frac{{\mathrm{<figure-callout\; id="3"\; label="gl"\; filenames="Y200820189449E00091.png,Y200820189449E00092.png"\; state="\{\{state\}\}">gl</figure-callout>}}^3\mathrm{\&alpha;\&Delta;t}}{v^2}$ (formula 3)

Wherein: g---acceleration of gravity, m/s ²

α---the coefficient of cubical expansion, 1/K;

△ t---fluid temperature (F.T.) and wall surface temperature is poor at a distance, K;

V---dynamic viscosity, m ²/ s.

$\mathrm{Pr}=\frac{\mathrm{\&eta;Cp}}{\mathrm{\&lambda;}}$ (formula 4)

Wherein: η---dynamic viscosity, Pa.s;

Cp---specific heat capacity at constant pressure, J/ (kg.K);

Can get by formula 1, formula 2, formula 3, formula 4:

$h=0.59\&times;\frac{\mathrm{\&lambda;}}{l^{0.25}}\&times;{(\frac{\mathrm{g\&alpha;\&Delta;t}}{v^2}\&times;\frac{\mathrm{\&eta;Cp}}{\mathrm{\&lambda;}})}^{0.25}$ (formula 5)

Suppose one 5 layers outside free convection finned heat exchanger, the fin height of individual layer is L, when neighbouring two-layer heat exchanger fin disconnection and two-layer up and down fin interbody spacer one segment distance, and its characteristic length l ₁=L, its free convection surface coefficient of heat transfer is designated as h1; When the neighbouring non-disconnection of two-layer heat exchanger fin, its characteristic length l ₂=5L, its free convection surface coefficient of heat transfer is designated as h2.Can get by formula 5:

$\frac{h1}{h2}=\frac{{l_2}^{0.25}}{{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="Y200820189449E00102.png"\; state="\{\{state\}\}">l</figure-callout>}}_1}^{0.25}}=5^{0.25}\&ap;1.5$

By aforementioned calculation as can be known, for one 5 layers outside free convection finned heat exchanger, the coefficient of heat transfer that adopts disconnection layering form is 1.5 times of non-disconnection layering; Therefore adopt the heat exchanger that disconnects layering can reduce consumption of materials significantly.

Analyze the beneficial effect that adopts finned heat exchanger below again: ignore each dirtiness resistance, each heat transfer resistance, the overall heat-transfer coefficient computing formula is as follows:

$\frac{1}{K}=\frac{1}{\mathrm{ho}\&times;\frac{\mathrm{Ao}}{\mathrm{Ai}}}+\frac{1}{\mathrm{hi}}$ (formula 6)

Wherein: K---total exchange coefficient of the heat exchanger, W/ (m ².K);

Ho---heat exchanger outside free convection heat transfer coefficient, W/ (m ².K);

The inboard forced convection heat transfer coefficient of hi---heat exchanger, W/ (m ².K);

The appearance heat transfer area of Ao---unit length heat exchanger tube, m ²/ m;

The interior table heat transfer area of Ai---unit length heat exchanger tube, m ²/ m.

The total heat exchange computing formula of heat exchanger:

Q=KF △ T (formula 7)

Wherein: Q---total heat exchange amount, W;

F---total heat exchange area, m ²

△ T---total heat transfer temperature difference, K.

Obviously, by formula 6 as can be seen, when in heat exchanger during with finned replacement light pipe, Ao increases, and the K value also can increase; Simultaneously since ho much smaller than hi, therefore the K value can enlarge markedly when Ao increases.After the K value increases, by formula 7 as can be seen, under the situation of same heat exchange amount and heat transfer temperature difference, can reduce needed total heat exchange area; By practical engineering calculation as can be known, because the tube wall of needed fin approaches increase considerably (Ao can increase by tens times) that reaches unit pipe range heat exchange area, can reduce the consumption of materials of heat exchanger significantly; As a heat exchange amount is the Teat pump boiler free convection condensing heat exchanger that is used to add hot water of 7KW, and when adopting the bronze pan tube form, the copper consumption is 9.3kg, and when adopting disconnection layering copper pipe copper fin heat exchanger, same effect copper consumption is 4.2kg; Therefore outside free convection can reduce the consumption of materials of heat exchanger significantly when adopting finned heat exchanger with heat exchanger.

As described in Figure 2, different places adopts the beneficial effect of different fin materials: with above-mentioned heat exchange amount be 7KW, the Teat pump boiler free convection condenser that is used to add hot water is example: when outside free convection when disconnecting the layering finned heat exchanger and be used to add hot water, need to adopt copper pipe copper fin pattern, its copper consumption is 4.2kg (wherein the copper pipe amount is 0.98kg, and the copper fin amount is 3.22kg); When this heat exchanger is used for cooling refrigeration agent steam, can adopt the copper pipe aluminum fin pattern, its copper consumption is 0.98kg, the aluminium consumption is 0.99kg; Therefore, when when different places adopts unlike material, can reduce the consumption of materials of heat exchanger again significantly

Present embodiment is the preferable implementation of the utility model, need to prove, is not breaking away under the prerequisite of the utility model design any conspicuous replacement all within the utility model protection domain, all belongs to the infringement trip and is.

Claims (5)

1. free convection finned heat exchanger, comprise two the cold and hot medium turnover pipes (4,6) that are communicated with exterior line, be communicated with heat exchanger tube (3) between the two turnover pipes, heat exchanger tube contacts with heat exchange fin (1), it is characterized in that: described heat exchanger tube and heat exchange fin are hierarchy, leave the gap between each layer, be communicated with by bridge piece (5) series connection between each layer heat exchanger tube.

2. free convection finned heat exchanger according to claim 1 is characterized in that: described heat exchanger tube laterally is interspersed in the heat exchange fin, is expanded joint or welding between heat exchanger tube and the heat exchange fin.

3. free convection finned heat exchanger according to claim 2 is characterized in that: the turnover pipe is provided with U type bending section.

4. free convection finned heat exchanger according to claim 3 is characterized in that: described heat exchange fin is plate or ripple type or flap type.

5. according to each described free convection finned heat exchanger in the claim 1～4, it is characterized in that: the heat exchanger tube sheet (7) of fixing each heat exchange fin and heat exchanger tube is arranged in the heat exchange fin arranged outside.

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