JPS6042594A - Heat exchanger with fins - Google Patents

Abstract

PURPOSE:To obtain a heat exchanger utilizing the expansion effect of heat transfer surfaces at its maximum, by fitting fins of different specifications to each part of a heat transfer pipe, making allowable surface temperature at the uppermost limit. CONSTITUTION:The highest surface temperature ''te'' in a fin 25 has its practical limit by the properties and concentration of a heating medium fluid and mixed substance used for a heat exchanger, and the optimum temperature can be calculated from the experiential data in the past. Fins 20, 21, and 22 are respectively fitted to the parts 17, 18, and 19 of a unit heat transfer pipe 1' which has a length L1. The fin 20 is made of thick plate in order to keep its surface temperature below the limit value, and the number of fins is small in order to make the sectional area of flow paths small and to hold down the cost for fin material in low price. In regard to the fins 21 and 22, thickness and the number of plates are determined by the temperature in the fluid at the inlet port which has been cooled down during transmission, and the fins must be designed so that the required amount of heat can be secured by the fins 20, 21, and 22 as a whole. The parts ''l17'' and ''m18'' of a heat transfer pipe 1' are made of bare pipe, while the fin 23 is fitted to the part ''n19'' so that its surface temperature is to be below the limit value, based on the temperature in the inlet air which has been cooled down while it was passing through the bare pipe parts ''l17'' and ''m18''.

Description

[Detailed description of the invention] Metallic fins (O-holes) are attached to heat transfer surfaces with low heat transfer coefficients, such as the gas side heat transfer surface of a heat exchanger and the liquid side heat transfer surface with a low flow rate. It is common to use a so-called fin heat exchange device that increases the amount of heat transfer.

In the case of a fin (=1 cooling wall), it is natural that the temperature of the fin becomes higher iJA in proportion to the distance from its root to the tip, and the physical properties of the fluid in contact with it or
Depending on the physical properties of the mixed materials, degrees, etc., there will be a bare heat transfer wall surface and a fin 4 heat transfer surface.

Subtle differences in the degree of dirt adhesion occur due to temperature differences on each fin surface, and if the temperature exceeds the temperature at the high temperature part of the fin tip, scale and dirt develop from that part, causing problems in operation. .

The present invention solves the above problems and provides a lean, compact, finoy, and j heat exchanger that optimally exhibits the fin effect in accordance with its surrounding atmosphere. That is, depending on the physical properties or concentrations of the heat transfer wall or fin surface in the middle of the flow path in the device, the heating medium fluid in contact with it, or the substance mixed therein, Alternatively, the heat exchange wall can be made of a combination of bare walls and finned walls to prevent scale and dirt caused by excessive surface temperatures of the heat transfer walls and fins in the heat exchange device. Furthermore, the present invention proposes a heat exchange device that maximizes the effect of enlarging the heat transfer surface by adding different fins to each part with a two-limited allowable surface temperature.

A specific example will be explained.

An example of a conventional configuration of a compressor intercooler or aftercooler is shown in FIGS. 1 and 2, and is assumed to be an intercooler that cools compressed air of T to tbl.

The high-temperature air T enters the inlet chamber 7 from 9 and flows into the pipe port 3 of the multi-pipe l airtightly attached to the pipe seat 14.

Fins 2 are attached to the inside of the tube 1 as an enlarged heat transfer surface. The water is cooled by the cooling water in the extra-tubular chamber 5, collected in the outlet chamber 8 from the tube outlet 4, and has a temperature of 1. / is discharged. 6 is the torso, ・12.

, 13 are cooling water pipes and outlets, and 11 is a flow path partition.

16 is the length of the tube plate interval, and 15 is the length L of the fin attachment part of the tube 1.
Indicates l.

Figure 6 is an explanatory diagram of the surface temperature distribution of the fin, and is an illustration of the surface temperature distribution of the fin 2.
5. Inner pipe surface 26. The height W of the fin layer and the thickness of the fin layer are 2 Yb, and its surface temperature distribution curve is shown by 29.

The surface temperatures at the tip and root of the fin are ta, tl, +, respectively.
When the temperature difference from the compressed air temperature T is θa and θ, respectively, and the fin efficiency is g, the average temperature difference is g θ.

The average surface degree of 1 degree is indicated by tm. The surface temperature 1a at the fin tip is expressed as a linear equation (a hyperbolic function), and depending on the fin element, it can be considerably higher than the fin root temperature t.

d is the heat transfer coefficient of the fins λ is the thermal conductivity of the fins Small amounts of oil and fine dust mixed in the compressed air naturally adhere to the parts, and as a so-called dirt coefficient, they impair the heat transfer effect and create a thin layer of dirt. The heat conduction is.

It is much worse than metal fins, so its outermost surface locally becomes hotter than the above-mentioned mountain pass, approaching the air temperature T in that area, and as the operation time becomes longer, the fin tip near the inflow part, which is the worst condition part. It is natural that carbonized scale is created starting from this, and the amount of scale and the area of adhesion are gradually expanded, which causes troubles such as functional deterioration of the heat exchange device.

The maximum surface temperature 1e of the fin mentioned above has a practical limit depending on the physical properties of the heating medium fluid and mixed substances, and degrees a, and cannot be determined comprehensively, but based on conventional experience, a comparative value Calculating it as a container is an item.

This invention solves the above-mentioned troubles.

Depending on the partial atmosphere of the heat transfer wall and fin,
It is designed to exhibit the optimum fin effect.

The principle explanatory diagrams of this invention are shown in Fig. 3, Fig. 4, Fig. 5, and
It is shown in FIG.

First, a case where a finned pipe having the structure shown in FIG. 3, FIG. 4, or FIG. 5 is inserted in place of the heat transfer tube of the conventional heat exchanger described above will be explained with reference to the following.

As an example, the finned length L1 of the unit heat exchanger tube 1' is divided into three sections and 7? , m, and n, and are numbered 17, 18.19, respectively. 17. The fins in the 18. and 19 parts are 20 and 21, respectively.
.

22, the fin 20 has a thick plate thickness, high fin efficiency, and a surface temperature below the above-mentioned limit value.

Reduce the number of fins to prevent the cross-sectional area of the flow path from becoming too small and the cost of fin materials to rise too high. For the fins 21 and 22, the number of fins 20, 21.2 is calculated by calculating the number of fins 20, 21.
2. It is designed to ensure the required amount of heat exchange as a whole.

Figure 5 shows / 17 and m 18 sections are bare pipes, and based on the transient inflow air of the cooler that has passed through those sections, n
An example is shown in which the fin n is attached to the 19th part with its surface temperature being below the above-mentioned limit value.

Further, the concentration of water vapor mixed in the compressed air and its dew point temperature, as well as the above-mentioned upper limit temperature, cannot be overlooked by the fins. A small amount of condensation on the surface of the heat transfer surface dramatically increases heat transfer, and generally has a positive effect on the dirt on the heat transfer wall surface mentioned above. There is also the possibility of fostering

Growth in wet film thickness conversely increases heat transfer resistance.

Therefore, it is necessary to prevent the growth of water droplets and water films. As described above, the purpose is to make the fin elements different according to the conditions caused by the temperature change in the heat exchange channel, and to optimize the enlarged heat transfer surface effect. That is, the fin elements such as the shape and dimensions of the fin, the material, the minimum fin gap, etc. are selected rationally.

The above-mentioned example illustrates the case of an inner tube fin.

The gist of the invention encompasses all heat exchange devices using finned heat transfer walls, regardless of whether the fins are inside a tube or are attached to an external membrane.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventionally used compressor intercooler, FIG. 2 is a sectional view of its heat exchanger tubes, and FIG. 3 is a fin division diagram of the unit heat exchanger tube of the present invention. Figure 4 is a cross-sectional view of the fin attached to the divided portion of Figure 3. Figure 5 is a cross-sectional view of the fin with a different configuration from Figure 4.
The figures each show an explanatory diagram of the surface temperature distribution of the fins. DESCRIPTION OF SYMBOLS 1... Heat exchanger tube 2... Conventional fin 1'... Fin division diagram of the unit heat exchanger tube of this invention 17, 18, 19
...1 division range each J, m, n addition, 21, 2
2... Fin blades attached to division 17, 18, and 19 respectively... Fin 25 attached to division 19... Fin cross section 26... Fin root wall n...
・Fin height: 1/2 of fin thickness: Fin surface temperature distribution patent applicant: Kiyoshi Konaka −

Claims (1)

[Claims] Depending on the surface temperature of the heat transfer wall or fin in the middle of the flow path in the device, the physical properties of the heating medium fluid in contact with it, or its mixed substances, or the temperature of the heat exchange wall in each section, A fin-4 heat exchange device in which the heat exchange walls have a mixed structure of a bare wall and a wall with fins.