Heat recovery type heat storage apparatus

Abstract

The invention provides a heat recovery type heat storage apparatus which makes an apparatus small-sized and compact and has a high reliability and an improved efficiency. In a heat recovery type heat storage apparatus transferring an exhaust heat contained in an exhaust gas supplied from a heat discharge apparatus so as to accumulate heat, there are provided a heat exchanger provided within an exhaust duct for discharging the exhaust gas, a compression gas source connected to the heat exchanger via an inlet pipe, and an injection portion provided at an end portion of an outlet pipe of the heat exchanger and inserted within a liquid received within a tank, and a gas is introduced to the heat exchanger from the compression gas source so as to be blown within the liquid from the injection portion.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a heat recovery type heat storage apparatus which recovers and accumulates an exhaust heat contained in an exhaust gas generated from a heat discharging apparatus such as a heat treatment furnace, an electric furnace, an engine or the like.

[0003] 2. Description of the Related Art

[0004] Conventionally, there is a heat recovery method using a partition wall type gas/gas heat exchanger, which is structured such that the air fed by a blower is supplied to a secondary side (a heat recovery side) of a heat exchanger provided in a high temperature exhaust gas and heat exchanged so as to be temperature increased, and the air having the increased temperature is used for heating, and is used for supplying hot water by further using a water/gas type secondary heat exchanger so as to produce a hot water.

[0005] Further, there has been known a matter that a heat pipe type heat exchanger is utilized as a heat exchanger, a heat of a combustion gas is transmitted to one end of a heat pipe and the heat is transmitted to another end of the heat pipe so as to heat the water around the same, thereby increasing a temperature thereof and accumulating the heat.

[0006] Further, it is described, for example, in Japanese Unexamined Patent Publication No. 4-244590 to exchange heat by using a direct contact between the exhaust gas and the liquid.

[0007] In the conventional art mentioned above, it is necessary to use the heat exchanger at two stages in order to use for supplying hot water, so that the apparatus becomes large-scaled. Further, a heat exchange efficiency is not sufficient due to the two-stage heat exchange and the temperature increase degree of water becomes low. Further, since the water temperature is increased so as to be changed to the hot water while being supplied to the secondary side, a water deposit is attached to an inner wall in a water side of the heat exchanger so as to deteriorate the heat exchange efficiency, and the heat exchanger is overheated so as to be damaged and bored, so that there is a case that the water flows into the exhaust gas and there is a risk that a vapor explosion is generated.

[0008] Further, in the structure using the heat pipe, in the case that the temperature of the exhaust gas is high, a vapor pressure of a working medium within the heat pipe is increased, so that there is a risk that the heat pipe is pressure destruction.

[0009] Further, in the structure of heat exchanger by using the direct contact between the exhaust gas and the liquid, since the exhaust gas is directly injected out into the liquid within a tank, the liquid is soiled by mists and impure materials in the exhaust gas.

BRIEF SUMMARY OF THE INVENTION

[0010] An object of the present invention is to provide a heat recovery type heat storage apparatus which solves the problems in the conventional arts mentioned above, makes an apparatus small-sized and compact and has a high reliability and an improved efficiency.

[0011] In order to achieve the object mentioned above, in accordance with the present invention, there is provided a heat recovery type heat storage apparatus transferring an exhaust heat contained in an exhaust gas supplied from a heat discharge apparatus so as to accumulate heat, comprising:

[0012] a heat exchanger provided within an exhaust duct for discharging the exhaust gas;

[0013] a compression gas source connected to the heat exchanger via an inlet pipe; and

[0014] an injection portion provided at an end portion of an outlet pipe of the heat exchanger and inserted within a liquid received within a tank,

[0015] wherein a gas is introduced to the heat exchanger from the compression gas source so as to be blown within the liquid from the injection portion.

[0016] Further, in the structure mentioned above, it is desirable that a nozzle having a small hole is provided in the injection portion.

[0017] Further, in the structure mentioned above, it is desirable that a negative pressure portion is provided by a stream of the gas passing through the injection portion, and a suction pipe is provided in the negative pressure portion.

[0018] Further, in the structure mentioned above, it is desirable that an inner wall having a lower hole and an upper hole is provided inside the tank, and the gas injected out from the injection portion is introduced to the liquid between the wall of the tank and the inner wall.

[0019] Further, in accordance with the present invention, there is provided a heat recovery type heat storage apparatus accumulating heat by utilizing a heat within an exhaust duct, comprising:

[0020] a heat exchanger provided within the exhaust duct;

[0021] a compression gas source connected to the heat exchanger via an inlet pipe; and

[0022] an injection portion provided at an end portion of an outlet pipe of the heat exchanger and provided near an upper portion of a liquid received within a tank,

[0023] wherein a gas is introduced to the heat exchanger from the compression gas source and the gas injected out from the injection portion is blown to the liquid.

[0024] Further, in the structure mentioned above, it is desirable that the liquid is agitated by driving an agitator provided in the liquid due to a compression air supplied from the compression gas source.

[0025] Further, in the structure mentioned above, it is desirable that the compression gas supplied from the compression gas source is a gas containing an overheated vapor or mists, or a vapor.

[0026] Further, in accordance with the present invention, there is provided a heat recovery type heat storage apparatus utilizing an exhaust heat contained in an exhaust gas, wherein a heat exchanger is provided within an exhaust duct discharging the exhaust gas, a gas is introduced to the heat exchanger so as to be temperature increased, and a heat contained in gas increased the temperature is accumulated so as to be supplied to a heat utilization equipment.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0027] FIG. 1 is a schematic view of an embodiment in accordance with the present invention;

[0028] FIG. 2 is a schematic view of the other embodiment in accordance with the present invention;

[0029] FIG. 3 is a schematic view of the other embodiment in accordance with the present invention;

[0030] FIG. 4 is a schematic view of further the other embodiment in accordance with the present invention;

[0031] FIG. 5 is a schematic view of further the other embodiment in accordance with the present invention;

[0032] FIG. 6 is a schematic view of further the other embodiment in accordance with the present invention;

[0033] FIG. 7 is a schematic view of further the other embodiment in accordance with the present invention;

[0034] FIG. 8 is a schematic view of further the other embodiment in accordance with the present invention;

[0035] FIG. 9 is a schematic view of further the other embodiment in accordance with the present invention;

[0036] FIG. 10 is a schematic view of further the other embodiment in accordance with the present invention;

[0037] FIG. 11 is a schematic view of further the other embodiment in accordance with the present invention;

[0038] FIG. 12 is a schematic view of further the other embodiment in accordance with the present invention;

[0039] FIG. 13 is a schematic view of further the other embodiment in accordance with the present invention;

[0040] FIG. 14 is a schematic view of further the other embodiment in accordance with the present invention; and

[0041] FIG. 15 is a schematic view of further the other embodiment in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0042] An embodiment in accordance with the present invention is shown in FIG. 1. A furnace 2 receiving a heat source (a combustion heat or the like) 3 has an exhaust duct 4, and an exhaust gas 5 is discharged from the exhaust duct 4. The exhaust gas 5 has a large amount of exhaust heat, and the heat recovery thereof becomes important.

[0043] In FIG. 1, a heat exchanger 6 is provided in the exhaust duct 4 and a heat medium is introduced within the heat exchanger 6. As the heat medium, it is preferable to introduce a gas (an air or the like) from a compression gas source 1 via a pipe 7. The temperature of gas introduced within the heat exchanger 6 is increased due to a heat of the exhaust gas 5 given from an outer surface of the heat exchanger 6, and thereafter blown into a liquid 12 within a tank 10 from an injection portion 9 through a pipe 8. Bubbles 13 generated thereby move upward due to a buoyancy in the liquid 12 and are discharged outward from a gap between a lid 11 and the tank 10. When the bubbles 13 float up in the liquid 12, the heat contained in the bubbles 13 is given to the liquid 12. The liquid 12 having the increased temperature is transferred to the external portion by using a pump or the like, and is used for a hot water supply and a space heating or a cleaning water.

[0044] In accordance with the present embodiment, since the liquid (the water) is not flowed within the heat exchanger 6, no water deposit is generated and accordingly a heat transfer efficiency is not deteriorated. Further, there is not generated a matter that a water leakage from the heat exchanger 6 is generated and the leaked water flows within the exhaust duct 4. Further, no other heat exchangers than the metal heat exchanger 6 are required. Further, since it is possible to increase the temperature of the liquid 12 only by blowing the gas within the liquid (the water) 12 in the tank 10, and it becomes easy to accumulate the heat.

[0045] FIG. 2 shows the other structure around the tank 10 in FIG. 1. In particular, a heat transfer method within the tank 10 is different from that in FIG. 1, and is structured such that the injection portion 9 of the pipe 8 is bent so as to blow onto the liquid surface of the liquid 12. The liquid surface swings while rising and falling, and a surface area thereof is increased so as to enhance heat transfer. In comparison with a method of generating the bubbles 13 in the liquid 12 shown in FIG. 1, it is possible to increase an injection amount of the gas supplying from the pipe 8.

[0046] FIG. 3 shows the other embodiment in which the bent injection portion 9 is slightly dipped into the liquid surface portion of the liquid 12. This embodiment can commonly have both of the effects obtained by the structures shown in FIGS. 1 and 2.

[0047] FIG. 4 shows further the other embodiment in which a manifold-like structure is horizontally arranged in an end portion of the pipe 8 so as to form the injection portion 9, a plurality of small holes 9-a are provided in this manifold, and the gas having the increased temperature is blown out toward the liquid surface of the liquid 12 from the small holes 9-a. In this case, the manifold-like injection portion 9 may be formed in an annular shape. A contact area between the liquid surface and the injected gas is increased and the heat transfer is increased by forming a lot of injection holes in the manifold-like injection portion 9, and the temperature of liquid 12 is increased to a desired temperature for a short time.

[0048] FIG. 5 shows further the other embodiment and illustrates a heat transfer method within the tank 10 in an enlarged manner. This corresponds to a structure in which a suction pipe 16 is provided in the injection portion 9 in a branch manner, and an open end 16-a is dipped into the liquid 12. When the gas is injected out from the open end 16-a of the injection portion 9, an inner portion of the contact portion between the suction pipe 16 and the injection portion 9 becomes negative pressure, and the liquid 12 is sucked up from the open end 16-a. That is, a part of the liquid 12 is mixed into the high temperature gas within the injection portion 9 so as to form the mists and be injected out from an end portion of the injection portion 9. That is, the mists of the liquid 12 and the high temperature gas are efficiently heat transferred due to the direct contact so as to be blown out from the injection potion 9, and are further collided with the liquid surface of the liquid 12 so as to be heat transferred, so that a temperature increase degree of the liquid 12 is increased due to both influences. Further, the liquid 12 easily generates a convection current within the tank 10.

[0049] FIG. 6 shows further the other embodiment in which the injection portion 9 in FIG. 5 is dipped into the inner portion of the liquid 12. In this case, the gas injected out from the injection portion 9 forms the bubbles 13 so as to be blown out within the liquid 12. A temperature increase effect of the liquid 12 is increased due to a synergetic effect comprising a suction effect of the liquid 12 from the open end 16-a and a blow-out effect of the bubbles 13 from the end portion of the injection portion 9.

[0050] FIG. 7 shows further the other embodiment in which the structure having the injection portion 9 horizontally attached to a lower end of the pipe 8 is directly dipped into the liquid 12 so as to blow out the bubbles 13 into the liquid 12 from the small holes 9-a of the injection portion 9. A heat insulating material 17 is surrounded around the portion in which the pipe 8 and the injection portion 9 are in contact with the liquid 12 so as to achieve a heat insulation. It insulating material 17 is not existed, since the heat is transferred to the liquid 12 via the pipe 8 and the wall of the injection portion 9, a temperature boundary layer is generated within the wall and the temperature of the gas is reduced. Then, the temperature of the gas is reduced at a time of forming the bubbles 13 so as to be injected out from the small holes 9-a. But it is possible to prevent by insulating effect a heat exchanging capacity between the bubbles 13 and the liquid 12 from being reduced.

[0051] FIG. 8 shows further the other embodiment in which the pipe 8 is horizontally arranged, and the horizontal injection portion 9 is connected to the pipe 8 so as to insert to the liquid 12 from a side surface of the tan k 10 as illustrated. The heat insulating material 17 is wound around the injection portion 9 so as to avoid the small holes 9-a. Further, a side plate of an upper lid 11 of the tank 10 is bent downward along the side surface of the tank 10 so as to constitute a duct 11-a. Accordingly, it is possible to reduce a heat radiation loss to an ambient air due to an effect of heating the wall of the tank 10 while being in contact with the tank 10 at a time when the gas moving upward within the liquid 12 moves around the duct 11-a from the upper portion of the lid 11.

[0052] FIG. 9 shows further the other embodiment in which a casing 18 is provided in the middle of the pipe 7 through which the gas passes, a vane 19 is provided within the casing 18, the gas is blown to the vane 19 so as to rotate the vane 19, and the rotation is transmitted to an agitator 21 attached to a lower portion thereof via a shaft 20 so as to agitate the liquid 12. The liquid 12 is well agitated due to a synergetic effect comprising an agitating effect of the liquid 12 and a swinging effect of the bubbles 13 injected out from the injection portion 9, the heat contained in the gas is transferred to the liquid 12, and the temperature increase effect thereof is increased.

[0053] FIG. 10 shows further the other embodiment in which the vane 19 having the casing 18 is provided in the pipe 8 portion in a back flow side of the heat exchanger 6. This structure has an advantage that a new modification work is applied only to a part around the tank 10 and the pipe 8 arranged near the same.

[0054] FIG. 11 shows further the other embodiment in which an inner wall 30 is vertically arranged near a side wall inside the tank 10 and a lower hole 31 and an upper hole 32 are respectively provided in a lower portion and an upper portion thereof. The injection portion 9 connected to the pipe 8 is provided in a lower portion of a liquid 12-a existing between the side wall inside the tank 10 and the inner wall 30 so as to blow the bubbles 13 into the liquid 12-a. A liquid level of the liquid 12-a is ascended due to a mixture of the bubbles 13, and the liquid 12-a increased temperature by the heat exchanger is leaked out from the upper hole 32 disposed in the upper portion so as to be flowed out to an opposite space 12. On the contrary, the liquid 12 enters the small space 12-a from the lower hole and reaches the portion near the injection portion 9, whereby the same cycle is repeated. It is desirable that a position and a size of the upper hole 32 provided in the upper portion of the inner wall 30 are determined on the basis of a density of the liquid 12 and a flow rate of the gas injected out from the injection portion 9. Accordingly, the liquid 12-a and the bubbles 13 are sufficiently heat exchanged in the longitudinally long heat transfer space constructed by the tank 10 and the inner wall 30, and the temperature increase degree is increased.

[0055] FIG. 12 shows further the other embodiment in which two inner walls 30 and 30-a are provided inside the tank 10 and the injection portions 9 and 9-a are provided in the respective small spaces. Lower holes 31 and 31-a and upper holes 32 and 32-a are respectively provided in lower portions and upper portions of the inner walls 30 and 30-a. Further, upper walls 33 and 33-a are provided in upper portions of the inner walls 30 and 30-a as occasion demands, thereby reducing a rebound of the bubbles 13 and the liquid 12-a. Further, the inner walls 30 and 30-a may be formed as one sheet of inner cylinder and may be annularly arranged inside the tank 10.

[0056] FIG. 13 shows further the other embodiment with respect to the injection portion 9 in which an underwater nozzle 40 having a lot of small holes 41 is provided in an end portion of the outlet pipe 8. Accordingly, a lot of small bubbles 13 are injected and dispersed into the liquid 12, and a heat exchange property is improved.

[0057] FIG. 14 shows further the other embodiment with respect to the injection portion 9 in which a pump 42 is provided so as to introduce the liquid 12 within the tank 10 by the suction pipe 16 and inject the liquid 12 to the injection portion 9 via a discharge pipe 43 by a narrow injection pipe 44. The liquid 12 formed in fine particles by the injection pipe 44 is scattered in the high temperature gas and the heat exchange property is improved.

[0058] As mentioned above, since the structure is made such that the gas/gas heat exchanger is provided in the exhaust gas, however, the compression air (obtained by utilizing the compression air source for the plant or the like) is introduced within the heat exchange passage in the secondary side (the heat recovery side) so as to be heat exchanged and temperature increased, the high temperature air is directly blown into the liquid (the water or the like) so as to be heat exchanged, and the temperature of the liquid is increased, the heat exchange efficiency is improved, there is no risk that the combustion loss of the heat exchanger, the vapor explosion, the pressure breakage or the like is generated, and the liquid is not soiled by the mists and the impure material in the exhaust gas.

[0059] In this case, in the embodiments mentioned above, it is desirable in view of the cost or the like to employ not only the air and the nitrogen but also the overheated vapor generated from the boiler, the vapor including the fine liquid particles (the mists), the vapor obtained by reheating the drain water of the boiler. Further, it is desirable in view of the efficiency and the cost to use the gas having a residual pressure after being once used for rotating a working machine in a cascade manner. Further, it is desirable in view of improving an efficiency if a latent heat storage type accumulating container is charged within the tank 10 so as to increase a heat accumulating capacity.

[0060] As mentioned above, in accordance with the present invention, since the gas is introduced into the heat exchanger within the exhaust duct so as to be temperature increased, and the heat of the gas having the increased temperature is accumulated so as to be utilized, the apparatus can be made small-sized and compact, and it is possible to obtain the heat recovery type heat accumulating apparatus having a high reliability and an improved efficiency.

[0061] FIG. 15 is a schematic view of further the other embodiment in accordance with the present invention. This corresponds to an embodiment in the case of recovering an exhaust gas of a heat treatment furnace so as to accumulate heat. This heat treatment furnace shows a case of putting a part 84 to be applied a heat treatment such as an annealing or the like on a belt-conveyor (made of steel) 81 and heating to a predetermined temperature while moving it, and recovering an exhaust heat generated at a time of cooling thereafter so as to accumulate heat. The part 84 is put on the belt-conveyor 81 moved by driving wheels 82 and 83 attached to a supporting table 80 and moves toward a right side from a left side within a furnace surrounded by a heat insulating cover 92. In a left half portion within the furnace surrounded by the cover 92, the part is heated to a high temperature by a radiating type main burner (using a butane gas, a liquefied petroleum gas (LPG) and the like for a fuel) 85. The radiating type burner is structured such as to be formed in a pipe shape, burn the fuel within the pipe so as to heat the pipe, and heat the part 84 due to a radiant heat given from an outer surface of the heated pipe. In this embodiment, a metamorphic gas (a mixture of O2, CO2, H2 and the like) generated due to the combustion of the fuel within the pipe is taken out so as to introduce to a cooling apparatus (not shown) and be cooled to a predetermined temperature (a dew point is controlled to a minus temperature), and the metamorphic gas (a neutral gas) is introduced within the furnace surrounded by the right cover 92, thereby preventing the part 84 from being oxidized. In the radiating type main burner mentioned above, there is a case that an amount of heat is insufficient and a temperature control within the furnace can not be sufficiently executed, however, in this case, there is a case that a half of the main burner employs the illustrated radiating type burner for producing the metamorphic gas and another half is replaced by an electric heater. In accordance with the heating system mentioned above, when the heated part 84 moves to a right space, an ambient temperature within the furnace is reduced by the cooling device 86 cooled by the water or the like, and the part 84 is suitably cooled at an outlet. The part 84 drops to the lower portion in a terminal portion of the furnace, however, is stored within a bucket 93 prepared therebelow. The part 84 finishes the heat treatment along the processes mentioned above, however, in order to prevent an oxidizing air from entering within the furnace surround by the cover 92 from right and left open ports so as to oxidize the part 84, auxiliary burners 87 and 88 are provided in an inlet cover 94 and an outlet cover 95 so as to burn the fuel generated from the auxiliary burners 87 and 88 by the oxidizing air, thereby preventing the oxygen from entering. However, since the exhaust heat is discharged from smoke ducts 89 and 90 and an exhaust duct 91 connected thereto, it is important to recover the heat. In this embodiment, the heat exchanger 6 in accordance with the present invention is provided within the inlet cover 94 and the outlet cover 95, the gas is introduced from the pipe 7 to the inner portion thereof, and thereafter the gas is blown into the liquid within the tank 10 via the pipe 8. Accordingly, the exhaust heat is accumulated in the liquid 12. The tank 10 in accordance with this embodiment is formed as a circulating structure separated into a side that the bubbles 13 move upward and a side that the liquid 12 moves downward, thereby achieving a structure having an improved heat exchanging property. Needless to say, heat exchange manner in this embodiment may be applied the structure of FIG. 1 to FIG. 14. The heat is effectively used for heating a room or a cleaning water at a desired time. In this embodiment, since the gas is introduced within the heat exchanger 6, the water leakage is not generated and the vapor explosion is not generated even if the heat exchanger 6 is broken. Accordingly, no damage is generated in the part 84.

[0062] In this case, the cooling water is introduced into the cooling device 86 within the cover 92, however, the temperature of the cooling water is increased due to the heat of the gas within the cover 92 and it is necessary to recover the heat. In this embodiment, in the case of connecting a pipe 105 with a pipe 104 to a pipe 102 in a branched manner, introducing the water having the increased temperature into the tank 10 from a pipe 106 with a valve 107 or a pipe 108 with a valve 109 and blowing the bubbles 13 having the increased temperature into the liquid 12 within the tank 10 so as to heat, the heat is used for a preheating of the liquid 12.

[0063] Further, in the case of changing the cooling device 86 to an air cooling type from a water cooling type, introducing the gas (or the vapor) into the cooling device 86 so as to recover the heat, thereafter directly blowing the gas (or the vapor) into the tank 10 or introducing to the pipe 7 so as to flow to the heat exchanger 6, and further heating to form the high temperature gas (or vapor) so as to inject to the tank 10, further more effects can be obtained.

[0064] In this case, in this embodiment, the heat exchanger 6 for recovering the heat may be provided in the smoke dusts 89 and 90 and the exhaust dust 91 in addition to the inlet cover 94 and the outlet cover 95.

Claims

1. A heat recovery type heat storage apparatus transferring an exhaust heat contained in an exhaust gas supplied from a heat discharge apparatus so as to accumulate heat, comprising:

a heat exchanger provided within an exhaust duct for discharging said exhaust gas;

a compression gas source connected to said heat exchanger via an inlet pipe; and

an injection portion provided at an end portion of an outlet pipe of said heat exchanger and inserted within a liquid received within a tank,

wherein a gas is introduced to said heat exchanger from said compression gas source so as to be blown within said liquid from said injection portion.

2. A heat recovery type heat storage apparatus as claimed in claim 1, wherein a nozzle having a small hole is provided in said injection portion.

3. A heat recovery type heat storage apparatus as claimed in claim 1, wherein a negative pressure portion is provided by a stream of the gas passing through said injection portion, and a suction pipe is provided in said negative pressure portion.

4. A heat recovery type heat storage apparatus as claimed in claim 1, wherein an inner wall having a lower hole and an upper hole is provided inside said tank, and the gas injected out from the injection portion is introduced to the liquid between the wall of said tank and said inner wall.

5. A heat recovery type heat storage apparatus accumulating heat by utilizing a heat within an exhaust duct, comprising:

a heat exchanger provided within said exhaust duct;

a compression gas source connected to said heat exchanger via an inlet pipe; and

an injection portion provided at an end portion of an outlet pipe of said heat exchanger and provided near an upper portion of a liquid received within a tank,

wherein a gas is introduced to said heat exchanger from said compression gas source and said gas injected out from said injection portion is blown to said liquid.

6. A heat recovery type heat storage apparatus as claimed in claim 1, wherein the liquid is agitated by driving an agitator provided in said liquid due to a compression air supplied from said compression gas source.

7. A heat recovery type heat storage apparatus as claimed in claim 5, wherein the liquid is agitated by driving an agitator provided in said liquid due to a compression air supplied from said compression gas source.

8. A heat recovery type heat storage apparatus as claimed in claim 1, wherein the compression gas supplied from said compression gas source is an overheated vapor a gas containing or mists or a vapor.

9. A heat recovery type heat storage apparatus as claimed in claim 5, wherein the compression gas supplied from said compression gas source is an overheated vapor or a gas containing mists or a vapor.

10. A heat recovery type heat storage apparatus utilizing an exhaust heat contained in an exhaust gas, wherein a heat exchanger is provided within an exhaust duct discharging said exhaust gas, a gas is introduced to said heat exchanger so as to be temperature increased, and a heat of the gas increased temperature is accumulated so as to be supplied to a heat utilization equipment.

11. A heat recovery type heat storage apparatus as claimed in claim 1, wherein said heat recovery heat exchanger is provided in an exhaust heat generating portion of a heat treatment furnace executing a heat treatment of a part.