JP2012032033A - Indirect type hot air generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly thermally efficient indirect type hot air generator suitable for miniaturization.SOLUTION: The indirect type hot air generator includes a housing having an inlet for heated air and a combustion gas outlet on one side and an outlet for heated air and a combustion gas supply source on the other side, and a plurality of pipes disposed in the housing in parallel to each other and in a zigzag form. One end in each of the plurality of pipes is connected to the combustion gas supply source and the other end is connected to the combustion gas outlet with a folded part for direction reversal between the one end and the other end. A gap between the pipes that are adjacent to each other in a zigzag form is shorter than a gap between the pipes on the upper side and on the lower side with the folded part between which are the closest to each other, and the pipes satisfy a formula L/D≥200 where L represents a length and D represents an inner diameter.

Description

  The present invention relates to a hot air generator, and more particularly, to an indirect hot air generator that heats a gas such as air to be heated without directly contacting it with a high-temperature combustion gas.

  Conventionally, a hot air generator has been used as a heat source for drying high-quality plating and coating, or for drying chemicals and foods. Among them, indirect hot air generators that indirectly heat a heated gas such as air using a partition type heat exchanger, the combustion gas and the heated gas are not in direct contact with each other. As seen in Patent Documents 1 to 4, various proposals have been made so far.

  However, as far as the present inventors know, these conventional indirect hot air generators have a net calorific value obtained by subtracting the latent heat of evaporation of water present in unit mass fuel and water generated during combustion from the total calorific value. As a standard, the thermal efficiency is usually as low as about 60 to 80%, and even those with good thermal efficiency remain at about 90%. Since the hot air generator burns gaseous fuel or liquid fuel and heats the gas such as air to be heated by the combustion heat, the low thermal efficiency means from the viewpoint of effective use of energy resources Is not preferred.

  On the other hand, in order to increase the thermal efficiency, it may be possible to increase the heat exchange area of the heat exchanger built in the hot air generator, but the equipment becomes complicated and large, which is expected to cause practical problems. At present, the improvement effect of thermal efficiency is not recognized.

Japanese Patent Laid-Open No. 7-19602 Japanese Patent Laid-Open No. 10-111087 JP 2001-4272 A JP 2002-372308 A

  The present invention has been made to solve the above-described problems in the conventional indirect hot air generator, and has an object to provide an indirect hot air generator that has high thermal efficiency and is suitable for downsizing. To do.

  The present inventors have conducted intensive research and trial and error in order to solve the above problems. As a result, a plurality of pipes are used as partition walls of the heat exchanger, they are arranged in a staggered manner with a relatively narrow gap between them, hot combustion gas is passed through the pipes, and pipes are placed outside the pipes. When a heated gas such as air is flowed from an orthogonal direction, the flow velocity of the heated gas increases when passing through a relatively narrow gap between the tubes arranged in a staggered pattern, and the surroundings pass through the gap. It was found that intense vortex flow was generated with the heated gas, and heat was rapidly transferred from the tube surface to the heated gas as if the heated gas was passed with a large air volume. At the same time, when the length and the inner diameter of the tube are set to L / D ≧ 200, the combustion gas temperature drops below the dew point while passing through the tube. The water vapor contained in the combustion gas condenses and turns into water, so that the latent heat of the water vapor contained in the combustion gas can be effectively transferred to the heated gas as the condensation heat. It has been found that extremely high thermal efficiency exceeding 100% can be obtained.

  That is, the present invention includes a housing having an inlet for a heated gas and a discharge port for a combustion gas on one side and an outlet for the heated gas and a supply source for the combustion gas on the other side; A plurality of pipes parallel to each other; the plurality of pipes are arranged in a staggered pattern with alternating heights, and one end of each pipe is connected to the combustion gas supply source. In addition, the other end is connected to the combustion gas discharge port, and has a folded portion that reverses the direction in the middle of the one end and the other end, and a gap W between the tubes adjacent to each other in a staggered manner. Is shorter than the nearest tube-to-tube gap V between the upper side and the lower side across the folded portion, and the length of each of the plurality of tubes is L and the inner diameter is D. By providing an indirect hot air generator with L / D ≧ 200 It is intended to solve the foregoing problems.

  The vertical distance Iv between the staggered adjacent tubes and the center of the tubes is preferably equal to or less than the outer diameter H of the tubes. When the vertical distance Iv is equal to or less than the outer diameter H of the pipe, the gap between the pipes adjacent to each other in a staggered manner becomes an appropriate size, and the flow velocity of the heated gas increases when passing through the gap, Heat is efficiently transferred from the tube surface to the heated gas. The plurality of pipes preferably have at least three folded portions between one end and the other end. By providing at least three or more folded portions, even a tube having a length longer than the inner diameter of L / D ≧ 200 can be folded compactly and placed in the housing. The indirect hot air generator can be made compact and small.

  As a supply source of the combustion gas in the indirect hot air generator of the present invention, any source may be used as long as a high-temperature combustion gas can be supplied into the plurality of pipes. From the viewpoint of being suitable for downsizing, it is preferable to use a combustion chamber provided in the housing and a burner having a tip opened in the combustion chamber as a supply source of the combustion gas. The burner may be an oil burner that burns liquid fuel, a gas burner that burns gaseous fuel, or a pulverized coal burner that burns pulverized coal, but the gas burner facilitates fuel handling. This is preferable.

  Further, the combustion gas generated by the burner may be introduced into the plurality of pipes from the front end side of the combustion chamber, but may be led into the plurality of pipes from the vicinity of the root on the burner side of the combustion chamber. Is good. When the combustion gas is led from the vicinity of the root of the combustion chamber into the plurality of pipes, the high-temperature combustion gas makes a round in the combustion chamber, and the temperature of the entire combustion chamber increases. There is an advantage that the temperature of the heated gas can be increased more uniformly.

  According to the indirect hot air generator of the present invention, the heated gas can be heated with a high thermal efficiency exceeding 100% on the basis of the true calorific value, so that an excellent advantage that significant energy saving can be realized is obtained. It is done. The indirect hot air generator of the present invention is generally used because it has a relatively simple structure and can be easily manufactured, and uses a plurality of tubes as partition walls of the heat exchanger. Compared to plate-type heat exchangers, it has the advantages of being strong against heat stress, strong, and compact and easy to downsize.

It is a front fragmentary sectional view which shows an example of the indirect type hot air generator of this invention. It is a front view of a pipe | tube. It is X-X 'sectional drawing of FIG. It is a perspective view showing the connection relation of an entrance side connection part and a pipe. It is a figure which shows the arrangement | positioning relationship in the vertical cross-section state of a pipe | tube. It is a schematic diagram which shows the flow of the to-be-heated gas which passes the clearance gap between a pipe | tube. It is a front fragmentary sectional view which shows another example of the indirect type hot air generator of this invention.

  Hereinafter, the present invention will be described in detail, but it is needless to say that the present invention is not limited to the illustrated one.

  FIG. 1 is a front partial sectional view showing an example of the indirect hot air generator of the present invention. In FIG. 1, 1 is an indirect hot air generator of the present invention, 2 is a housing, 3 is a base, 4 is a heated gas inlet provided at the lower part of the housing 2, and 5 is an upper part of the housing 2. The heated gas outlet provided, 6 is a fan that feeds the heated gas from the heated gas inlet 4 into the housing 2, and 7 is a rectifying plate having an opening in a mesh shape for allowing the heated gas to flow on average. In addition, although air is generally used as the heated gas, the heated gas is not limited to air, and may be an inert gas such as nitrogen gas, for example.

  Reference numeral 8 denotes a gas burner, and 9 denotes a combustion chamber. The gas burner 8 and the combustion chamber 9 constitute a supply source of combustion gas. As shown in the figure, the tip of the gas burner 8 opens into the combustion chamber 9, and the combustion chamber 9 has a bottomed cylindrical shape with the tip closed. 10 is an inlet side connecting portion provided in the vicinity of the burner side root of the combustion chamber 9, 11 is an outlet side connecting portion provided at the lower portion of the housing 2, and 12 is a combustion gas exhaust port provided at the lower portion of the housing 2. It is. Denoted at 13 is a drainage drain port provided in the outlet-side connecting portion 11 for discharging water condensed from the latent heat of the combustion gas by removing heat from the heat exchange.

P and P are hollow tubes that function as partition walls of the heat exchanger, arranged horizontally in a staggered manner, parallel to each other, and alternately changing in height. Is connected to the inlet side connecting portion 10, and the lower end which is the other end is connected to the outlet side connecting portion 11. Although only two pipes P are shown in FIG. 1, as will be described later, the indirect hot air generator 1 of this example includes 13 pipes P. The cross section of the tube P is preferably circular, and all the 13 tubes P are preferably the same shape, the same size, and the same length.

  As shown in the figure, the pipe P has a horizontal straight part m and a folded part r bent with a relatively small radius of curvature, and after proceeding linearly and horizontally, in the folded part r, The direction is inverted 180 degrees, and while meandering, the inlet side connection portion 10 and the outlet side connection portion 11 are connected and accommodated in the housing 2 in a compactly folded state. Thus, in the indirect hot air generator 1 of the present invention, each pipe P itself has the folded portion r, and the combustion gas flowing in the pipe P is in the shape of the folded pipe P. The direction of the flow is reversed at the turn-back portion r and flows to the outlet side connection portion 11 while meandering in the limited space in the housing 2, so that a header (collecting pipe) is not required. It is possible to have a very simple structure.

  In this example, the number of the folded portions r provided in the middle of the upper end and the lower end of the pipe P is six, but the number of the folded portions r is not limited to six, and is seven or more. Also, the number may be 5 or less. However, a relatively long pipe P of L / D ≧ 200 is compactly provided in the housing 2 with a moderate flow resistance in the housing 2 and, as will be described later, the length of the pipe P is L and the inner diameter is D. From the viewpoint of accommodating in the inside, it is desirable to provide at least three folded portions r. s is a spacer that keeps the gap between the plurality of pipes P constant.

  When the gas burner 8 is ignited, a high-temperature combustion gas accompanied by a flame is jetted into the combustion chamber 9 from the opening at the front end of the gas burner 8, hits the closed front end of the combustion chamber 9, and changes its direction. It flows into the inlet side connection part 10 opened in the vicinity of the root side and is led into the pipe P. The combustion gas that has passed through the inside of the pipe P and has been deprived of heat and whose temperature has dropped passes through the outlet side connecting portion 11 and is discharged from the combustion gas discharge port 12 to the outside. On the other hand, the heated gas fed into the housing 2 from the heated gas inlet 4 by the fan 6 is averaged in the horizontal plane by the rectifying plate 7 and then passes through the gap between the tubes P and P. , P is heated from the surface of P. Subsequently, the heated gas passes through the periphery of the combustion chamber 9 disposed in the upper part of the housing 2, is further heated, and becomes hot air, and is led from the heated gas outlet 5 to appropriate locations. It is used for

  In the indirect hot air generator 1 according to the present invention, as described above, the gas burner 8 and the combustion chamber 9 which are supply sources of the combustion gas are positioned at one upper portion of the housing 2, and the heated gas inlet 4 is located in the housing 2. The combustion gas flows in the pipe P from the upper side to the lower side of the housing 2. On the other hand, the heated gas such as air flows through the housing 2 from below to exchange heat with each other, so that it is a counter-flow heat exchanger as a whole. Therefore, the temperature of the heated gas flowing around the pipe P gradually decreases from the upper end to the lower end of the pipe P, and is fed into the housing 2 from the heated gas inlet 4 at a portion close to the outlet side connection portion 11. The heated gas that has just been brought to near room temperature flows around the pipe P and takes heat from the pipe P. In particular, in the indirect hot air generator 1 of the present invention, as will be described later, the heated gas rapidly takes heat away from the surface of the pipe P. Therefore, in the portion close to the outlet side connection portion 11 of the pipe P, The temperature of the combustion gas flowing through the gas becomes below the dew point, and the contained water vapor is condensed, and the heat of condensation can be transmitted to the heated gas. Water produced by the condensation of water vapor is discharged from the discharge port 13 to the outside.

  In the indirect hot air generator 1 of this example, the heated gas outlet 5, the gas burner 8 and the combustion chamber 9 as the combustion gas supply source are located in the upper part of the housing 2, and the heated gas inlet 4 And the combustion gas discharge port 12 is located in the lower part of the housing 2, but as long as a counterflow type heat exchanger is constituted as a whole, this positional relationship may be reversed. That is, for example, the heated gas inlet 4 and the combustion gas discharge port 12 are arranged in the upper part which is one side of the housing 2, and the heated gas outlet 5, the gas burner 8 and the combustion chamber 9 which are the supply source of the combustion gas. May be arranged in the lower part which is the other side of the housing 2.

  FIG. 2 is a front view showing only the pipe P taken out, and an enlarged view of the right side view of the pipe P is also shown in the lower right. As shown in the figure, the pipe P has a horizontal straight part m and a folded part r, and is bent in the vertical direction by 180 degrees with a relatively small radius of curvature at the folded part r. Is meandering in a vertical plane and compactly folded. The straight line portion m does not necessarily need to be horizontal, and may be slightly inclined from the horizontal, and the folding angle at the folded portion r may be slightly larger than 180 degrees.

  Pt is the upper end of the pipe P, Pb is the lower end of the pipe P, and z in each of them is connected to the inlet side connecting part 10 and the outlet side connecting part 11 and connected to the inlet side connecting part 10 and the outlet side connection. It is a part inserted into the part 11. Therefore, in the pipe P, the part functioning as the partition wall of the heat exchanger is a part obtained by removing the z part from both ends of the pipe P. In this specification, the length L of the pipe P is the length of the pipe P. In P, the length of the part which functions as a partition of a heat exchanger shall be pointed out. D is the inner diameter of the pipe P, and H is the outer diameter of the pipe P.

  In the indirect hot air generator of the present invention, the ratio of L and D, that is, L / D is preferably 200 or more, more preferably 300 or more. When L / D is less than 200, it is usually difficult to achieve a thermal efficiency exceeding 100% on the basis of the true calorific value, although it depends on the air flow rate of the fan 6 and the flow path resistance in the housing 2. is there. In the indirect hot air generator of the present invention, the length L of the pipe P is relatively longer than the inner diameter D, but as described above, the pipe P has at least three folded portions r having a small radius of curvature. Therefore, the pipe P can be accommodated in the housing 2 in a state of being folded into a compact shape, and the indirect hot air generator can be easily miniaturized.

  3 is a cross-sectional view taken along the line X-X ′ of FIG. 1, and the same members as those in FIG. 1 are denoted by the same reference numerals. As shown in FIG. 2, the plurality of pipes P are arranged in a horizontal direction in the housing 2 and are arranged in a zigzag pattern in which the height changes alternately. In addition, as described with reference to FIG. 2, the straight line portion m and the folded portion r in each tube P are in the same vertical plane, and the tubes P are parallel to each other. In this example, the adjacent pipe P and the pipe P are in contact with each other or almost in contact with each other at the turn-back portion r, and are extremely densely arranged. In this example, the number of pipes P arranged in the housing 2 is 13, but the number of pipes P is not particularly limited as long as the heated gas can be heated with high thermal efficiency. What is necessary is just to set it as an appropriate number according to the heat exchange capability calculated | required by the indirect type hot air generator 1. FIG. However, in the indirect hot air generator of the present invention, it is important that the heated air is jetted into a wider space by increasing the flow velocity by passing through the gap between the adjacent pipes P. At least 3 or more are necessary, and 5 or more are preferably arranged.

  FIG. 4 is a perspective view showing the connection relationship between the inlet side connecting portion 10 and the pipe P. FIG. As shown in the figure, the inlet side connection portion 10 is formed with connection ports 10h into which the upper ends of the pipes P are inserted by the number of the pipes P. Although not shown in the drawing, the outlet side connection portion 11 is also formed with the same number of connection ports 11h as the number of the tubes P into which the lower end of the tube P is inserted, similarly to the inlet side connection portion 10.

  When assembling the indirect hot air generator 1 of the present invention, as shown in FIG. 4, one end of the required number of pipes P is inserted into the connection port 10h of the inlet side connection portion 10 and fixed, and the other end Need only be inserted into the connection port 11h of the outlet side connection part 11 and fixed. The staggered arrangement of the plurality of pipes P and the interval between them are determined by the arrangement and the interval between the connection port 10h of the inlet side connection portion 10 and the connection port 11h of the outlet side connection portion 11, and the structure is simple. In addition, it can be assembled very easily. Furthermore, since a plurality of tubes are used as the partition walls of the heat exchanger, for example, compared to a plate-type heat exchanger, it is resistant to thermal stress, is robust, and can be manufactured at a relatively low cost. Benefits are gained. In addition, what is necessary is just to arrange | position the spacer which fixes the space | interval between each pipe | tube P if necessary.

  FIG. 5 is a diagram showing an arrangement relationship of the pipe P in a vertical cross-sectional state in the indirect hot air generator 1 of the present invention. In the figure, C is the center of the pipe P, H is the outer diameter of the pipe P, D is the inner diameter, “upper side” is the upper side of the folded portion r, and “lower” is the lower side of the folded portion r. It shows that there is. As shown in the figure, the “upper” tubes P, P, P... Are alternately arranged in a staggered shape, and in this example, the vertical direction between the centers C of adjacent tubes P is arranged. The distance Iv is equal to 1/2 of the outer diameter H of the pipe P, and the horizontal distance Ih between the centers C of the adjacent pipes P is slightly larger than the outer diameter H of the pipe P. Therefore, in this example, the adjacent pipes P are in a state of being substantially in contact with each other at the folded portion r. This arrangement relationship is the same for the pipes P, P, P. The distance Iv may be equal to the outer diameter H so that the adjacent pipes P are in contact with each other at the turn-back portion r.

  W indicates a gap between adjacent pipes P arranged in a staggered pattern, and V indicates a gap between the pipe P and the pipe P that is closest between the upper side and the lower side across the folded portion r. Show. As shown in the figure, in the indirect hot air generator 1 of the present invention, it is important that W is shorter than V. That is, the gap W between the adjacent pipes P arranged in a staggered pattern is larger than the gap V between the pipe P and the pipe P closest to the upper side and the lower side across the folded portion r. By being short, the heated gas flowing from the bottom to the top between the pipes P, P, P..., As schematically shown in FIG. 6, the pipes P, P, P,. After passing through the relatively narrow gap W, the relatively wide space between the upper pipes P, P, P... And the lower pipes P, P, P. It spouts into the space, generates a violent vortex accompanying the surrounding heated gas, and rapidly from the surface of the tubes P, P, P ... as if the heated gas was passed with a large air volume. It is possible to take away heat.

  W may be shorter than V, and there is no particular limitation on the ratio of V to W, ie, V / W, but V / W is preferably 2.5 to 30.0, more preferably 5. 0 to 20.0. If V / W is less than 2.5, the difference between W and V is not so great, the increase in the flow velocity of the heated gas when passing through the gap W, and the surrounding heated air after passing through the gap W The generation of a vigorous vortex accompanying the water is not sufficient, which is not preferable. On the other hand, if V / W exceeds 30.0, the height of the indirect hot air generator in the vertical direction becomes undesirably large.

  The gap W between the adjacent pipes P arranged in a staggered manner can be adjusted by adjusting the vertical distance Iv between the centers C of the adjacent pipes P shown in FIG. it can. In the example shown in FIG. 5, Iv is ½ of the outer diameter H of the pipe P, that is, 0.5H, but the distance Iv is not limited to 0.5H. Adjacent pipes P and pipes P are arranged in a staggered manner, and a gap W between adjacent pipes P and the pipes P arranged in a staggered pattern is formed between the upper side and the lower side across the folded portion r. Shorter than the gap V between the closest pipes P and P, preferably V / W is in the range of 2.5 to 30.0, more preferably V / W is in the range of 5.0 to 20.0. As far as possible, there is no particular limitation on the distance Iv.

  Further, the gap W between the adjacent tubes P arranged in a staggered manner can be adjusted by adjusting the horizontal distance Ih between the centers C of the adjacent tubes P shown in FIG. it can. In the example shown in FIG. 5, the distance Ih is slightly larger than the outer diameter H of the pipe P, and is set in the range of 1.0H to 1.1H, preferably in the range of 1.01H to 1.02H. The distance Ih is such that the gap W is shorter than the gap V, preferably V / W is in the range of 2.5 to 30.0, more preferably V / W is in the range of 5.0 to 20.0. As long as there is no particular restriction.

  As described above, in the indirect hot air generator 1 of the present invention, the vortex flow as shown in FIG. 6 is generated by the flow of the heated gas, and in addition to the rapid removal of heat from the surface of the tube P, the L Since the length L of the pipe P is longer than the inner diameter D when / D ≧ 200 or more, the temperature of the combustion gas flowing in the pipe P is less than the dew point at a location close to the outlet side connection portion 11 and included. The condensed water vapor is condensed, and the heat of condensation can be transmitted to the heated gas. Although it depends on the ratio of W / V and the air volume of the heated gas that passes through the housing 2, the present inventors have confirmed that the indirect hot air generator of the present invention has a true thermal efficiency. Thermal efficiency exceeding 100% on the basis of the calorific value and about 105 to 108% can be realized.

  FIG. 7 is a front partial sectional view showing another example of the indirect hot air generator 1 of the present invention. The same reference numerals are given to the same members as before. In the indirect hot air generator 1 of the present example, the heated gas inlet 4 and the combustion gas discharge port 12 are arranged in the upper part of the housing 2, opposite to the indirect hot air generator 1 shown in FIG. In addition, the heated gas outlet 5, the gas burner 8 as the combustion gas supply source, and the combustion chamber 9 are arranged in the lower part as the other side of the housing 2. As a result, the upper end of the pipe P is connected to the outlet side connecting portion 11, and the lower end is connected to the inlet side connecting portion 10. As described above, in the indirect hot air generator 1 of the present invention, the combustion gas and the heated gas may be exchanged while forming a counter flow as a whole, and the heated gas inlet 4 and the combustion gas outlet 12, the heated gas outlet 5 and the combustion gas supply source may be located on one side and the other side of the housing 2, respectively, and either one may be arranged on the upper part or the lower part of the housing 2.

  As described above, according to the indirect hot air generator of the present invention, it is possible to provide a hot air generator that is simple and easy to assemble, is small and compact, and has high thermal efficiency. According to the indirect hot air generator of the present invention, while being indirect heating, it is possible to realize a high thermal efficiency exceeding 100% on the basis of the true calorific value and as high as 105 to 108%, and generating clean hot air extremely efficiently. Can do. Further, since more energy can be used than directly transferring the combustion heat of the fuel to the heated gas, the energy saving effect is enormous, and it has great industrial applicability.

DESCRIPTION OF SYMBOLS 1 Indirect type hot air generator 2 Housing 3 Base 4 Heated gas inlet 5 Heated gas outlet 6 Fan 7 Current plate 8 Burner 9 Combustion chamber 10 Inlet side connection part 11 Outlet side connection part 12 Combustion gas discharge port 13 Drainage port P Tube H Tube outer diameter D Tube inner diameter L Tube length W, V Gap

Claims (4)

A housing having a heated gas inlet and a combustion gas outlet on one side and a heated gas outlet and a combustion gas supply source on the other; parallel to each other, arranged horizontally in the housing A plurality of tubes; the plurality of tubes are arranged in a zigzag pattern with alternately changing heights, and one end of each tube is connected to the combustion gas supply source and the other end is Connected to the combustion gas discharge port, and has a folded portion that reverses the direction in the middle of the one end and the other end, and a gap W between the tubes adjacent to each other in a staggered pattern L / D ≧ 200 when the length of each of the plurality of pipes is L and the inner diameter is D, which is shorter than the gap V between the pipes closest to the upper and lower sides. An indirect hot air generator.   2. The indirect hot air generator according to claim 1, wherein the plurality of pipes have at least three folded portions between the one end and the other end.   3. The indirect hot air generator according to claim 1, wherein the supply source of the combustion gas is a combustion chamber provided in a housing and a burner having a tip opened in the combustion chamber.   One end of the plurality of tubes is connected to the one end of the combustion gas by one of the inlet side connecting portions that open to the burner side root of the combustion chamber and the other is connected to the one end of the plurality of tubes. Connected to a supply source; one end opening to the outside of the housing and the other end connected to the other end of the plurality of tubes, the other end of the plurality of tubes is exhausted of the combustion gas. The indirect hot air generator according to claim 3 connected to the outlet.

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