JPS6162788A - Air preheater - Google Patents

Abstract

PURPOSE:To improve an efficiency of heat exchanger with an increased speed of fluid by a method wherein an area of flow passage of the heat exchanging fluid is decreased by an orifice plate and a spacer rod in the heat exchanger. CONSTITUTION:Pipes 9 are inserted into orifice plates 11 arranged near the inlet port and outlet port of a preheater so as to regulate and uniformly distribute the ignition gas and the holes 11a for passing the ignition gas are formed. The clearance between the pipes has spacer bars 10 arranged between both orice plates 11 at the inlet and outlet ports. The ignition gas is passed through the ignition gas inlet ports 5 and enters the heat exchanger, flows out of the pipes 9 and then flows out from the ignition gas outlets 6. At this time, since the orifice plates 11 narrow the flow passages, the ignition gas is smoothed and flows along the pipes 9. The arrangement of the spacer bars 10 causes an effect along the pipes 9 to be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air preheater attached to a burner section of a Stirling engine, etc.

[Conventional technology]

Conventionally, there has been a device of this type as shown in FIG.

The device shown in FIG. 4 is called a plate heat exchanger, and in the figure, 1 is an outer flange that also serves as the outer case of the air preheater.

2 is an inner flange facing a combustion chamber 4 which will be described later, and 3 is an element which is a plate-fin type heat exchanger, the details of which are shown in FIG. 4 is a combustion chamber where combustion is performed by the burner; 5 is a combustion gas inlet into which the combustion gas generated in the combustion chamber 4 flows; 6 is a combustion gas outlet through which this combustion gas flows out; 7 is air for supplying to the burner. The fresh air inlet 0.8 into which the heat exchanged burner supply air flows is the fresh air outlet through which the heat-exchanged burner supply air flows out.

Fig. 6 shows another conventional device, which is called a shell & tube type heat exchanger. 2 is an inner flange facing the combustion chamber 4, and 9 is a pipe through which air to be supplied to the burner flows. In addition, the combustion chamber 4
．． Combustion gas population 5. Combustion gas outlet 6. Lower with fresh air.

and fresh air outlet 8 are similar to those shown in FIG. In FIGS. 4 and 6, solid line arrows indicate the flow of air, and broken line arrows indicate the flow of combustion gas.

Next, the operation will be explained. In Figure 4, the burner (
(not shown), combustion gas is created in the combustion chamber 4. This combustion gas (approximately 1200℃) has a combustion gas population of 5
The combustion gas enters through the element 3 and flows out through the combustion gas outlet 6. On the other hand, air is introduced from the fresh air intake lower, and while passing through the element 3, heat is exchanged by heat radiation and conduction, and the air is heated to approximately 500 to 600°C. The fresh air then flows out from the fresh air outlet 8 and is used as supply air for the burner. By heating the air before combustion in this way, combustion efficiency is increased and complete combustion is facilitated.

Next, in the apparatus of FIG. 6, the combustion gas generated in the combustion chamber 4 enters from the combustion gas port 5, flows outside the pipe 9, and exits from the combustion gas outlet 6. On the other hand, air is introduced from the fresh air intake lower and flows inside the pipe 9. During this time, the air undergoes heat exchange through heat radiation and conduction from the pipe surface, flows out from the fresh air outlet 8, and is used as supply air for the burner.

[Problem that the invention seeks to solve]

Since the conventional air preheater is configured as above,
In the device shown in Figure 4, element 3 is required to increase the amount of heat exchange.
It is necessary to increase the area of the heat exchanger, and the entire heat exchanger becomes large. Furthermore, in the structure shown in Figure 4,
There is space that does not contribute to heat exchange. In the apparatus shown in FIG. 6 as well, since the pipes 4 are arranged at equal pitches, the gaps between the outer pipes become large, and there are spaces that do not contribute to heat exchange. In order to obtain the necessary amount of heat exchange in such a device, the number of pipes must be increased, but if the number of pipes is increased, the overall size of the heat exchanger increases as described above.

This invention was made in view of the above points, and an object of the present invention is to provide an air preheater that improves the heat transfer coefficient of a shell and tube heat exchanger and can obtain the required amount of heat exchange with a small number of pipes. It is said that

[Means for solving problems]

The air preheater according to the present invention is provided with an orifice plate near the inlet and outlet of a shell-and-tube type heat exchanger in which a hole is formed through which a pipe is inserted and through which a heat exchange fluid flows. A spacer zelkova is arranged between the two plates.

[Effect]

In this invention, the flow path area of the heat exchange fluid is reduced compared to the conventional one by means of an orifice plate and a spacer provided in the heat exchanger, and the velocity of the fluid is increased to improve the heat exchange efficiency.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1(a) is a sectional side view of an air preheater according to an embodiment of the present invention, FIG. 1(b) is a plan view thereof, and FIG. 2 is a partially enlarged sectional view of the air preheater. In the figure,
1 is the outer flange that also serves as the outer case of the air preheater, 2
The inner flange 9 facing the multi-combustion chamber 4 is a pipe through which air to be supplied to the burner flows.

Combustion chamber 4. Combustion gas population 5. Combustion gas outlet 6. The fresh air inlet lower and the fresh air outlet 8 are similar to those shown in FIG. 11 is installed near the inlet and outlet of this preheater to rectify the combustion gas.

The plate 11 is an orifice plate for even distribution, and a hole 11a is formed in the plate 11 through which the pipe 9 is inserted and through which the combustion gas is circulated. A spacer rod 10 is disposed in the gap between the pipes 9 and between the inlet and outlet orifice plates 11, and is made of heat-resistant sedamic or metal. In addition,
In FIGS. 1 and 2, solid line arrows indicate the flow of air, and broken line arrows indicate the flow of combustion gas.

Next, the effects will be explained. Combustion gases are created in the combustion chamber 4 by a burner (not shown). This combustion gas (approximately 1200° C.) enters the heat exchanger section through the combustion gas port 5, flows outside the pipe 9 and exits through the combustion gas outlet 6. At this time, since the flow path is narrowed by the orifice plate 11, the combustion gas is rectified and flows along the pipe 9. Furthermore, the effect of the spacer rod 10 along the pipe 9 is promoted. on the other hand,
Air is introduced from the fresh air intake lower and flows inside the pipe 9. During this time, heat is exchanged through heat radiation and conduction from the pipe surface. At this time, as the high-temperature combustion gas flows along the pipe 9 as described above, the heat exchange between the high-temperature combustion gas and the pipe 9 is promoted, and thereby the heat exchange of the air flowing inside the pipe 9 is also promoted. . The heat-exchanged air then flows out from the fresh air outlet 8 and is used as supply air for the burner.

Here, a mechanism for promoting heat exchange will be described, and the effects of this embodiment will be explained in more detail.

First, when the flow rate is constant and the flow path area decreases as in this example, the continuity equation % formula % ρ1: Density of the heat exchange fluid when the flow path area decreases.
(kg/rrr) A1: Channel area (after reduction) [-] ρO: Density of heat exchange fluid before channel area decreases
(kg/n?) Ao: Flow path area (before reduction) [-] ul: Flow velocity (after reduction) (m/s) u
o: Flow velocity (before decrease) (m/S) If ρ1 - ρO, it can be seen that u゛1 (flow velocity) increases.

Next, the Nusselt number, a dimensionless quantity indicating the ease of heat transfer, is N u
= 0.023ReQ8-P rQ4 (Dittus-Boelter equation regarding turbulent thermal heat transfer in a circular tube)% formula% d: Representative length (m) C: Kinematic viscosity coefficient (n?/s) a: Temperature conductivity
(nf/3), it can be seen that as the flow rate U increases, the Nu number also increases and the heat exchange rate increases.

Further, in this embodiment, forced convection heat transfer is promoted by disturbing the flow.

In this way, the orifice plate 11 and the spacer rod 1
By providing 0, the heat transfer coefficient is improved, and therefore, the required amount of heat exchange can be obtained with a small number of pipes, and the device can be downsized.

In the above embodiment, air was flowed into the pipe and high-temperature combustion gas was flowed around the pipe, but the reverse may be used.

Further, in the above embodiment, no processing is applied to the outer surface of the pipe, but as shown in FIG. The exchange rate can be further improved. Further, the position and number of orifice plates are not limited to those in the above embodiment.

Furthermore, although the outer surface of the spacer rod is not processed in any way in the above embodiment, protrusions may be provided thereto to promote turbulence and further improve the heat exchange rate.

〔Effect of the invention〕

As described above, according to the present invention, in a shell and tube type air preheater, an orifice plate for rectifying and distributing the heat exchange fluid is provided near the inlet and outlet, and the gap between the vias 1 is provided. Since the spacer rods are provided, the heat transfer coefficient of the heat exchange section can be significantly improved compared to the conventional one, and the required amount of heat exchange can be obtained with a small number of pipes, which has the effect of making the device more compact.

[Brief explanation of drawings]

FIG. 1 (al is a sectional side view of an air preheater according to an embodiment of the present invention, FIG. 1 (bl is a sectional view taken along the line rb-rb, and FIG. 2 is a partially enlarged sectional view of the air preheater, Fig. 3 is a diagram showing another embodiment of the present invention, Fig. 4 T8) is a cross-sectional side view of a conventional plate type air preheater, and Fig. 4 0:I) is its IV.
b-I! 5 is a detailed view of the element of the air preheater shown in FIG. 4, and FIG. figure(
bl is a sectional view taken along the line ■b--b. . 9... Pipe (tube), 10... Spacer rod,
11... Orifice plate, 12... Coil. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent: Ken Hayase, Patent Attorney - Figure 1 (Q) Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Procedural amendment (voluntary) 1. Indication of case Japanese Patent Application No. 183440/1983 2
, Title of the invention Air preheater 3, Person making the amendment 5, Detailed description of the invention in the specification to be amended.

Claims (5)

[Claims] (1) In a shell and tube type air preheater, an orifice plate is provided near the inlet and outlet of the air preheater in which holes are formed through which tubes are inserted and heat exchange fluid is circulated, and between each tube. An air preheater characterized in that a spacer rod is disposed between the two orifice plates. (2) The air preheater according to claim 1, characterized in that the outer surface of the tube is provided with turbulence means for disturbing the flow of the heat exchange fluid. (3) The air preheater according to claim 2, wherein the turbulence means is a wire wound spirally around the outer surface of the tube. (4) Claim 2, wherein the turbulence means is a fin fixed to the outer surface of the tube.
Air preheater as described in section. (5) The air preheater according to claim 1, wherein the spacer rod has a protrusion on its outer surface.