JP3300728B2 - Heat exchanger using spiral fin tubes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger using a spiral fin tube for use in an exhaust gas boiler or the like.

[0002]

2. Description of the Related Art A spiral fin tube in which a spiral fin (hereinafter simply referred to as "fin") is wound around a heat exchanger tube (hereinafter simply referred to as "bare tube") and fixed to a heat exchanger to increase heat transfer efficiency. Are arranged in a zigzag pattern to form a heat transfer surface. When manufacturing such a heat exchanger, first, the pitch of the arrangement of the bare tubes is determined, and then the heat exchanger is manufactured using a spiral fin tube having a fin specification suitable for the bare tubes having the pitch arrangement.

[0003] As a general idea in this case, as the interval between the bare tubes is reduced, the pressure loss of the fluid flowing outside the bare tubes, that is, the draft loss of a tube group formed by a number of spiral fin tubes increases. However, there was little merit in employing the spiral fin tube as a whole.

The pitch arrangement and fin specifications of the spiral fin tube have been determined as follows.

[0005] _{h f / d o> 0.45 S} D / d e> 2.0 , however, h _f is wound around the outer peripheral surface of the bare tube, the height of the fins is secured, d _o is the outside of the bare-tube Diameter and _SD are number 1
Shown in, to the flow direction of the gas, spacing of the spiral fin tube adjacent diagonally, i.e., diagonal tube pitch in the gas flow direction, d _e is the spiral fin tube,
This is the equivalent diameter calculated by Equation 2 for conversion to an equivalent bare tube without fins.

[0006]

(Equation 1)

[0007]

(Equation 2)

[0008] However, in the heat exchanger having the bare tube arrangement and the fin specification determined in this manner, the heat transfer area when the draft loss and the heat absorption of the tube group are constant is significantly reduced, compared with the present case. There is a disadvantage that the heat exchanger cannot be reduced in size and the production cost increases.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a spiral fin tube is arranged in such a manner that the heat exchange rate per unit heat transfer area is improved, and the heat transfer when the draft loss and the heat absorption amount are constant. It is an object of the present invention to provide a heat exchanger using an inexpensive spiral fin tube which has an excellent heat transfer characteristic that can be reduced by reducing the area, the volume and the weight of the heat exchanger.

[0010]

Accordingly, the spa of the present invention is provided.
A heat exchanger using an ilarfin tube is
did. (1) Spas arranged in a direction perpendicular to the gas flow direction
Pitch S of the Iralfin tube_TAnd the gas flow direction
Pitch of spiral fin tube arranged in_Lof
Ratio S_T/ S_LGas flow in the range of 1.0 to 1.4
Of spiral fin tubes adjacent in the vertical and diagonal directions
Pitch S_DAnd the spiral fin calculated by equation (2)
Tube equivalent diameter d_eRatio S_D/ D_eIs 1.6
Are arranged in the range of 2.2 from the outer surface of the bare tube.
Rolled and fixed fins in the bare tube axial direction
The spacing S and the height h of the fin on the outer peripheral surface of the heat transfer tube_fRatio S
/ H _fIn the range of 0.36 or more and 0.65 or less
I made it. (2) The height h of the fin_fAnd the outer diameter d of the heat transfer tube
_oRatio h_f/ D_oIn the range from 0.29 to 0.35
I tried to be.

[0011]

[Action] Spiral fin tube is used for the exhaust gas boiler, as compared with the general spiral fin tube for use in air-conditioning heat exchanger, a low height h _f of the fins, since the larger the spacing S of the fins It shows characteristics close to the heat transfer characteristics of bare tubes. Further, regarding the parameters S / h _f and h _f / d _o of the fin shape, it can be seen that there is an optimum region that greatly exceeds the heat transfer characteristics of the bare tube for the following reasons.

With respect to the parameter S / h _f , if S / h _f is large, the state becomes close to a bare tube, the flow velocity near the fin increases, and the heat transfer characteristics of the fin increase.
Further, when S / h _f is small, it becomes difficult for the heating gas to flow to the root portion of the fin, and as a result, the heat transfer characteristics of the fin deteriorate. Therefore, it is predicted that there is a region where the heat transfer characteristic is optimal for S / h _f .

With respect to the parameter h _f / d _o , h _f / d
Regarding _o , when _hf is low, the state becomes close to a bare tube, the flow velocity near the fin increases, and the heat transfer characteristics of the fin improve, and when _hf is high, the heating gas stops flowing to the fin root. As a result, the heat transfer characteristics of the fins are degraded, and it is predicted that there is an optimum region for h _f / d _o as well as the parameter S / h _f .

[0014] Thus, the optimal area is the fin root.
It is predicted that the flow of the heated gas will greatly affect the heat transfer characteristics.
From that, S_T/ S_LRange from 1.0 to 1.4, S_D
/ D _eRange from 1.6 to 2.2
The main cases shown in Table 1 are arranged in a zigzag arrangement.
As a result of an experiment for No, the fin spacing and fin
Height ratio S / h_fHeat transfer ratio h / h_oIn the relationship
Figure 2 shows the fin height and bare tube outer diameter.
Ratio h_f/ D_oHeat transfer ratio h / h_oThe relationship
As a result, FIG. 3 was obtained.

Here, h is the external heat transfer coefficient (kcal / m ² h ° C.) of the spiral fin tube based on the total external surface area, h _o
Indicates the external heat transfer coefficient (kcal / m ² h ° C.) of the bare tube obtained by converting the shape of the spiral fin tube into an equivalent diameter calculated by Expression 2.

From these figures, it can be seen that 0.36 ≦ S / h _f ≦
Cases No. 16, 17, 19, 2 provided with fins satisfying the condition of 0.65 and 0.29 ≦ h _f / d _o ≦ 0.35
It can be seen that the heat transfer characteristics of the spiral fin tube No. 6 are good.

Therefore, if a heat exchanger using a spiral fin tube having fins within this range is used, the draft loss of the tube group and the heat transfer area when the heat absorption amount is constant are greatly increased. , The heat exchanger volume can be reduced, and the production cost can be reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a heat exchanger using a spiral fin tube according to the present invention will be described below with reference to the drawings. FIG. 1 is a view showing one embodiment of a spiral fin tube used in a heat exchanger using the spiral fin tube of the present invention, wherein FIG. 1 (A) is a partial sectional view, and FIG. 1 (B) is a partial side view. FIG.

As shown in FIG._oThe bare tube
1 has a thickness t_f, Height h _fFin 2 is axial
Spirally wound at intervals S in the direction, and its base end is used for welding etc.
The spiral fin tube 3 is formed more firmly.
Have been.

The spiral fin tube 3
The equivalent diameter d _e to convert a bare tube having no fins has an outer diameter d _o of the bare tube 1, the thickness t _f of the fin height h _f, the outer diameter d _f and axial per inch It can be calculated from the number of fins n _f (n _f = 25.4 / S) and Equation 2.

[0021] Spiral fin tube 3 is arranged in a direction perpendicular to the inflow direction of the heating gas F in the heat exchanger, the direction of the pipe pitch perpendicular to the gas flow direction S _T, a tube pitch in the gas flow direction S _L when the tube pitch of the slant gas flow direction was S _D, 1.0 <heat exchange in a staggered arrangement in the range of _{S T / S L <1.4 1.6} <S D / d e <2.2 Housed in a vessel.

In the above, when a heating gas having a flow rate of 5 to 10 kg / m ² S is passed, the design conditions are respectively set as follows: the draft loss of the tube group is within 30 mmAq, and the heat absorption is 20.79 × 10 ^6.
Table 1 and FIGS. 2 and 3 show the experimental results when kcal / h and the width in the pipe mounting direction were 7.3 m.

[0023]

[Table 1]

As shown in Table 1 and FIGS.
36 <S / h _f <0.65 and 0.29 <h _f / d _o <
In this embodiment the range of 0.35, it was found that extravascular heat transfer coefficient ratio h / h _o> 1.23 is obtained.

On the other hand, 0.36 < S / h _f < 0.
Be in the range of _{65, h f / d o =} 0.22 in the case N
o18, and 0.29 <h _f / d _o <be in a range of 0.35, S / h _f = 0.34 in case No24 or S
/ H _f = 0.35 as the case No30 of, in the case where one of the range is out, it was found that the h / h _o can not be obtained substantially 1.0 degree and good heat transfer characteristics.

The case No. 30 of the present embodiment and the case No. 30 of the comparative example in which the outer diameter of the bare tube 1 matches the case No.
As a result, it was found that the draft loss of Case Nos. 16 and 17 did not increase as compared with that of Case No. 30.

As described above, when the spiral fin tube having the fins 2 in the range of the present embodiment is used,
The heat exchange rate per unit heat transfer area is improved. On the other hand, if the heat exchange rate can be increased and the heat transfer area can be reduced, the spiral fin tube 3 provided in the heat exchanger can be used.
Can be reduced, so that the depth of the heat exchanger can be reduced and the height of the fins 2 can be reduced.

As a result, regarding the heat transfer area, the total weight of the fins 2 and the bare tube 1 and the volume of the heat exchanger,
As shown in Table 2 in which the present examples Nos. 16 and 17 were compared with the comparative example case No. 30, it was found that the value of the present example could be significantly reduced as compared with that of the comparative example.

[0029]

[Table 2]

As described above, in the heat exchanger using the spiral fin tube of the present embodiment, since the heat transfer area, the volume of the heat exchanger, and the weight of the fin and the tube can be greatly reduced, the heat exchanger has a significant effect. Cost reduction has become possible.

In this embodiment, the materials of the bare tube 1 and the fin 2 are carbon steel (SPCC).
It has been found that the same effect can be relatively obtained when a low alloy steel such as 1 to 3% Cr steel or a SUS material is used.

[0032]

As described above, according to the heat exchanger using the spiral fin tube of the present invention, both the volume and the weight of the heat exchanger can be greatly reduced by the structure shown in the claims. Low draft loss, excellent heat transfer characteristics,
A heat exchanger using spiral fins can be used, and a significant cost reduction can be achieved as compared with a conventional one.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a spiral fin tube used in a heat exchanger using the spiral fin tube of the present invention, and FIG. 1 (A) is a partial cross-sectional view showing an arrangement, and FIG. ) Is a partial side view,

FIG. 2 is a diagram showing the relationship of h / h _o to the S / h _f,

FIG. 3 is a diagram showing a relationship between h _f / d _o and h / h _o .

[Explanation of symbols]

 1 bare tube 2 fin 3 spiral fin tube

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takayuki Maeda 1-1, Akunouramachi, Nagasaki City Inside Nagasaki Shipyard, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-1-159597 (JP, A) JP-A-4-306468 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) F28F 1/36 F22B 37/10 F28D 1/00 F22B 1/18

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the spiral fin tube is set at 1.0 <
And in a staggered array of _{S T / S L <1.4,1.6 <} S D / d e <2.2, in the heat exchanger using the spiral fin tube, the spiral fin tube 0.36 <S A spiral fin tube formed by fixing a spiral fin formed by: / h _f < 0.6 0.29 < h _f / d _o < 0.35 to the outer peripheral surface of a bare tube. The heat exchanger used. However, S _T; orthogonal direction to the gas flow direction tube pitch (mm) S _L; the spiral fin tube; gas flow direction of the tube pitch (mm) S _D; gas flow direction to the diagonal tube pitch (mm) d _e equivalent diameter (mm) S; spiral fin spacing (mm) h _f; spiral fin height (mm) d _o; the outer diameter of the bare tube (mm)