JPS58136988A - Heat exchanger for heat recovery of drain - Google Patents

Abstract

PURPOSE:To make a heat exchanger of small-size and to improve an efficiency of its operation by a method wherein a pipe with helical fins is arranged at the inner circumference of a casing being contcted to the outer circumference of the fins in the heat exchanger for use in recovering heat in steam generator to the boiler refilling water and then the drain is fed into the pipe and the refilling water is supplied to the outside of the pipe. CONSTITUTION:A drain passage pipe 20 with helical fins 16 is arranged in such a way as their outer circumferences are contacted to the inner circumference of the cylindrical casing 13, resulting in making a heat exchanger 5. With this arrangement, the drain is introduced or fed into the pipe 20 at the upper part thereof and then the boiler refilling water 18 is fed into the casing 13. The water stored in the refilling water passage 21 accepts the heat from the drain 20 to raise its temperature and then the hot water is collected at the upper part of the drain pipe. Then, a feeding of the refilling water 18 pushes the hot water 19 out of the pipe. With this arrangement, the refilling water is transformed into a disturbed flow by the helical fins 16, resulting in making an improved thermal efficiency as well as manufacturing a small-sized heat exchanger.

Description

DETAILED DESCRIPTION OF THE INVENTION (Subject of the Invention) The present invention relates to a heat exchanger used to transfer and recover heat of condensate generated in steam equipment or the like to make-up water for a boiler.

(Prior Art) Japanese Unexamined Patent Publication No. 56-42002 discloses a device that uses a heat exchanger to transfer heat from multiple lines to make-up water for a boiler and recover it. In the heat exchanger of this device, the part through which the drain flows is made of a spirally wound fin tube. When winding the tube in a spiral shape, depending on the diameter of the tube,
Since the diameter of the helix is determined, the cross-sectional area of the heat exchanger is relatively large.

On the other hand, since the make-up water passage in the heat exchanger is relatively short and straight from the bottom to the top, it is necessary to increase the length of the heat exchanger in order to obtain the desired heat exchange. be. Therefore, when the amount of condensate generated is small, this heat exchanger is too large and corresponds to a pressure vessel, requiring strict management.

(Technical Problem) A technical problem of the present invention is to provide a heat exchanger that has good heat exchange efficiency and is small in size.

(Structure and operation) The structure of the drain heat recovery heat exchanger of the present invention is as follows. A spiral fin is formed on the outer periphery of the pipe through which the drain flows. This finned tube is inserted into a cylindrical member so that the outer circumference of the fins contacts the inner circumferential wall of the member. Both ends of the cylindrical member are closed with flanges or the like. Therefore, makeup water enters through the inlet at one end of the casing, flows spirally around the drain pipe along the fins, and flows out through the outlet at the other end.

Since the spiral make-up water passage is provided with fins between the straight drain pipe and the casing in this way, the diameter of the heat exchanger is only several times the diameter of the drain pipe. In addition, the make-up water flows through a very long spiral path while receiving heat while in contact with the fins, so heat exchange is efficient.

It is desirable to use this heat exchanger by installing it vertically.

This is because the high-temperature water added to the interior stays there, improving the efficiency of heat exchange. However, even if installed horizontally, the make-up water passage is formed in a spiral shape, so the reduction in heat exchange efficiency is relatively small. Moreover, a plurality of heat exchangers can be installed in parallel or in series.

(Example) Next, the illustrated example will be described. FIG. 1 schematically shows a drain heat recovery device using a heat exchanger according to the present invention and a piping system.

In FIG. 1, a water supply pump 4 and a heat exchanger 5 are arranged in a water supply line 3 extending from a water supply tank 1 to a boiler 2. A predetermined amount of makeup water is secured in the water tank 1 using a ball tap 6 or the like. The water supply pump 4 automatically operates based on a signal from a means for detecting overcast conditions in the boiler 2, such as a water level detector 7. A heat exchanger 5 is disposed between a water supply pump 4 and a boiler 2 in a water supply line 3.

The heat exchanger 5 has a drain pipe 8 to which condensate, ie, drain, generated in steam-using equipment (not shown) is guided. It is preferable that the heat exchanger 5 is installed in a vertically elongated manner, that makeup water is introduced into the lower part and taken out from the upper part, and drain is introduced from the upper part and taken out from the lower part. It is preferable that the portion 9 of the drain pipe 8 that exits the heat exchanger 5 rises again to the upper part of the heat exchanger 5, and the sub-pressure regulating valve 10 is attached thereto. - The next pressure regulating valve may be something like a spring-biased check valve; - it opens when the pressure on the next side (heat exchanger side) exceeds a set pressure due to the elastic force of the spring, and closes when less than that. This is to maintain a high pressure on the primary side. Check valves 11 and 12 are arranged before and after the heat exchanger 5 in the water supply line 3.

FIG. 2 is a sectional view showing the structure of the heat exchanger 5.

The casing of the heat exchanger is made by welding flanges 14, 15 to both ends of a cylindrical tube 13. The heat exchanger portion of the drain piping is made of a tube 17 having spiral fins 16 formed on its outer periphery.

The outer diameter of the fins 16 is designed to be approximately equal to the inner diameter of the cylindrical tube 13. Then, after inserting the finned tube 17 into the cylindrical tube 13, the flanges 14.15 are welded. Drain pipe 17
The ends pass through the flange 14.15 and are hermetically welded thereto. Makeup water introduction piping 18 at the bottom of the cylindrical pipe 13
Weld and attach the lead-out pipe 19 to the upper part.

Therefore, the heat exchanger 5 has a straight drain passage 20 in the center along the axis, and a spiral make-up water passage 2 around it.
1 is formed.

A drain heat recovery device as shown in FIG. 1 is mainly applied to small-capacity boilers, and feed water pumps are generally operated intermittently. - The pressure control valve 10 is set at a relatively low pressure so that the drain generated in steam-using equipment does not accumulate in the equipment. Since the drain pressure within the heat exchanger 5 is higher than that of the atmosphere, drain of 10011 iC or more flows into the drain passage 20. Since the passage portion 9 rises to the top of the heat exchanger 5, drain is always collected in the drain passage 20. When the water supply pump 4 is stopped, the makeup water passage 21
Heat exchange occurs between the make-up water remaining in the drain passage 20 and the drain in the drain passage 20. Since the fluid has a property that the higher the temperature is, the higher the fluid is located, the higher the temperature in the make-up water passage 21, the higher the temperature, and the amount of heat it retains gradually increases. On the other hand, the lower part of the inside of the drain passage 20 is lower in temperature, and the lower humidity drain is preferentially discharged.

When the water supply pump 1 is operated, the make-up water pressurized by the pump 4 flows into the heat exchanger 5 in such a way as to push out the residual high-temperature water in the heat exchanger 5, and the make-up water flows into the spiral make-up water passage 21. flows into.

The make-up water passage 21 is a long passage surrounded on three sides by the walls of the fins 16 and the drain pipe 17, and the make-up water efficiently receives heat from the drain in the darkness through which it passes. Since the make-up water passage 21 has a spiral shape, the make-up water flows in a turbulent flow, which improves heat transfer and prevents scale adhesion.

(Special effect) In a heat exchanger that stores a large number of drain tubes in a bundle in a casing, manufacturing costs are high because drilling of the head plate, cutting of the tubes, and work to secure the tubes and the head plate are required. Bulk. In the case of the present invention, the spiral finned tube can be simply inserted into the tube member of the casing.

In the present invention, by reducing the pitch of the fins of the drain pipe and lengthening the make-up water passage, the heat transfer area can be expanded, so that the efficiency of heat exchange can be improved.

In the present invention, make-up water flows through a long spiral path, creating a turbulent flow and improving heat exchange efficiency.Furthermore, it is effective in preventing scale adhesion.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a drain heat recovery device and piping system using the heat exchanger of the present invention, and FIG. 2 is a longitudinal sectional view of the heat exchanger of the embodiment of the present invention. 2: Boiler 3: Water supply line 4: Water supply pump 5: Heat exchanger 8: Drain piping 13: Cylindrical pipe forming heat exchanger gluing
17: Fin 20: Drain passage 21: Spiral make-up water passage Patent applicant procedure amendment writing method) % formula % 1. Indication of the case Japanese Patent Application No. 57-17796 2. Name of the invention Heat exchanger for drain heat recovery 3. Relationship with the case of the person making the amendment Patent applicant address: 4, 810, 8th floor, Hibiya Kokusai Building, 2-2-3 Uchisaiwai-cho, Chiyoda-ku, Tokyo Date of amendment order: May 7, 1980 5: Subject of amendment (1) Money side of the application (2) Money side of the specification 6. Contents of amendments (1) Engraving of the application (no change in content) (2) Engraving of the specification (no change in content) 7. inventory

Claims (1)

[Claims] A spiral fin is formed on the pipe through which the drain flows, and the fin is inserted so that the outer circumference of the fin touches the inner peripheral wall of the cylindrical casing of the heat exchanger, and makeup water enters from the inlet at one end of the casing and flows around the drain pipe. A heat exchanger for drain heat recovery, characterized in that the water flows spirally along the fins and flows out from an outlet at the other end.