JPH07167584A - Cleaning method of heat exchanger and double tube - Google Patents

Abstract

PURPOSE:To reduce manufacturing cost by providing a double tube which includes an outer tube and an inner tube made of polyolefin resin which is inserted into the outer tube and effect heat-exchange between cold water or hot water flowing in the outer pipe and hot water or cold water flowing in the inner pipe. CONSTITUTION:A double tube 14, which is the main part of a heat exchanger 10, is housed in a spiraled state just like a coil inside a housing 12. The double tube 14 includes an outer tube 16 which is made of a flexible material, such as soft vinyl chloride. An inner tube 18 made of polyolefin resin having a high strength, such as polybutene is inserted into the outer tube. This construction prevents the generation of such a trouble that the inner tube 18 will be damaged by the pressure of cold water flowing inside. It is, therefore, possible to eliminate the need to install a pressure control valve or the like as in a prior art, and hence simplify the structure and reduce manufacturing cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger and a double pipe cleaning method, and more particularly to a double pipe including an inner pipe for flowing hot springs or cold springs and an outer pipe for flowing cold or hot water. And a method for cleaning such double tubes.

[0002]

2. Description of the Related Art An example of a conventional heat exchanger of this type is disclosed in Japanese Utility Model Laid-Open No. 59-76876. This conventional technique includes a double pipe in which an inner pipe (inner pipe) made of smooth copper is inserted inside an outer pipe (outer pipe) made of vinyl chloride, etc. A hot water discharge line is connected to the pipe so that the water pressure of the outer pipe is set to be higher than that of the inner pipe.

[0003]

In the prior art, the water pressure of the outer pipe was set to be higher than the water pressure of the inner pipe, so that a pressure regulating valve or the like for such pressure control is necessary. However, there was a problem that the cost was high. In addition, if the inorganic or organic substances contained in the discharged hot water adhere to the internal pipe and the heat transfer or water permeability is impaired, there is no alternative but to replace the internal pipe with a new one. There was a problem that the cost was high.

Therefore, the main purpose of the first invention is to
An object of the present invention is to provide a heat exchanger that can reduce manufacturing costs. The main object of the second invention is to provide a method for cleaning a double pipe, which can reduce the maintenance cost of the system.

[0005]

A first aspect of the present invention is provided with a double pipe line which includes an outer pipe and an inner pipe made of a polyolefin resin and which is inserted into the outer pipe, and is provided with cold water flowing in the outer pipe. It is a heat exchanger that exchanges heat between hot water and hot or cold water that has flowed through the inner pipe. A second invention is a method of cleaning a double pipe including an outer pipe and an inner pipe inserted into the outer pipe, wherein hot water is poured into both the outer pipe and the inner pipe at the same time, and then cold water is flowed at the same time. This is a method of cleaning a double pipe in which the inner pipe is expanded and contracted to remove the deposits attached to the inner pipe.

[0006]

In the first aspect of the invention, since the inner pipe is formed of a polyolefin resin such as polybutene, which can exhibit high strength even under continuous internal pressure load at high temperature, cold water flowing through the inner pipe is prevented. Even if the pressure is higher than the pressure of hot water or the like flowing through the outer pipe, the problem that the inner pipe is damaged does not occur. Therefore, it is not necessary to provide a pressure adjusting valve or the like for setting the water pressure of the outer pipe higher than the water pressure of the inner pipe as in the conventional case.

In the second aspect of the present invention, hot water is flown into both the outer pipe and the inner pipe at the same time, and then cold water is flowed at the same time to expand and contract the inner pipe, thereby removing deposits attached to the inner pipe. Since the inner tube has a long life, it is not necessary to replace it.

[0008]

According to the first aspect of the present invention, since the pressure adjusting valve and the like are unnecessary, the manufacturing cost can be reduced. According to the second aspect of the invention, the inner tube can be effectively cleaned, so that the maintenance cost of the system can be reduced. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A heat exchanger 10 of this embodiment shown in FIG. 1 is for heating a cold spring (or hot spring) supplied to a bath or the like to a predetermined temperature with hot water, and has a substantially cylindrical housing. Including 12. Inside the housing 12, a double pipe 14 which is a main part of the heat exchanger 10 is housed in a coiled state. The double tube 14 includes an outer tube 16 made of a flexible material such as soft vinyl chloride, polybutene, polypropylene, polyethylene, or cross-linked polyethylene. Inside the outer tube 16, polybutene, polypropylene, polyethylene is used. Alternatively, the inner tube 18 made of a polyolefin resin having high strength such as cross-linked polyethylene is inserted. A tank 20 for storing hot water is arranged in the center of the inside of the housing 12. On the other hand, outside the housing 12, the pump 2
2 and the water heater 24 are arranged at predetermined positions. The outer pipe 16, the inner pipe 18, the tank 20, the pump 22, the water heater 24, etc. are connected to the pipe 26 and the valves 30a to 30.
are connected to each other using f, etc., and at one end of the inner pipe 18,
The inlet pipe 32 for introducing the cold spring (or hot spring) is the valve 30.
A supply pipe 34 for supplying heated cold spring or hot spring to a bath or the like is connected to the other end. A water pipe 38 is provided at one end of the tank 20 and the inner pipe 18 with a ball tap 36 and a valve 30b.
The discharge pipe 4 is connected to the discharge port of the pump 22 through the discharge pipe 4.
0 is connected via a valve 30g or the like.

When heating a cold spring (or hot spring),
The valves 30a, 30c, 30d and 30f are opened, the valves 30b, 30e and 30g are closed, and the pump 22 and the water heater 24 are operated. Then, the cold spring (or hot spring) introduced from the introduction pipe 32 and the water introduced from the water pipe 38 flow in the heat exchanger 10 as shown by the broken line arrow and the solid line arrow in FIG. 2, respectively. That is, the cold spring (or hot spring) introduced from the introduction pipe 32 is given to the inner pipe 18 of the double pipe 14 through the valves 30a and 30c, and is supplied to a bath or the like not shown through the supply pipe 34. On the other hand, the water introduced from the water pipe 38 is passed through the ball tap 36 to the tank 20.
Given by the pump 22 and aspirated by the valve 22
It is given to the water heater 24 through f. The hot water heated by the water heater 24 is supplied to the outer pipe 16 of the double pipe 14 through the valve 30d and returned to the tank 20 from the outlet of the double pipe 16. In the double pipe 14, a cold spring (or hot spring) is flown through the inner pipe 18 and hot water heated by the water heater 24 is flowed through the outer pipe 16, so that the cold water (or hot spring) is heated by the hot water.
Is heated to a predetermined temperature.

When a cold spring (or hot spring) is flown through the inner pipe 18 for a long period of time, an inorganic substance or an organic substance contained in the cold spring (or hot spring) is deposited on the inner surface of the inner pipe 18, and the inner pipe 18 passes through. Water and heat transfer are impaired. Therefore, in this embodiment, such a deposit (scale) is regularly removed by heating the inner tube 18 once and then rapidly cooling it.

The operation for removing the scale will be described below. First, the valves 30c, 30d, 30e and 30
f is opened, valves 30a, 30b and 30g are closed, and pump 22 and water heater 24 are operated. Then, the hot water heated by the water heater 24 flows in the heat exchanger 10 as indicated by the solid arrow in FIG. 3, and the hot water is supplied to both the outer pipe 16 and the inner pipe 18. When the inner pipe 18 is sufficiently heated, the valves 30b and 30g are opened, the valve 30f is closed, and the water heater 24 is stopped. Then, the water (cold water) introduced from the water pipe 38 flows in the heat exchanger 10 as shown by the broken line arrow in FIG. That is, a part of the water (cold water) introduced from the water pipe 38 through the valve 30b is given to the inner pipe 18 through the valve 30c, and the rest is the valve 30.
It is provided to the outer tube 16 through e and 30d. Then, the water given to the inner pipe 18 is discharged through the supply pipe 34 to a not-shown bath or the like, and the water given to the outer pipe 16 is supplied to the tank 20, the pump 22, the valve 30g and the discharge pipe 40.
Exhausted through. In the double pipe 14, the inner pipe 18
Since cold water is supplied to both the outer pipe 16 and the outer pipe 16, the inner pipe 1
8 is rapidly cooled and contracted from both its inner and outer surfaces. The contraction of the inner pipe 18 destroys the scale attached to the inner surface of the inner pipe 18, and the scale is discharged together with water to a bath (not shown) or the like.

The stress θ generated by rapidly cooling the inner tube 18 can be expressed by θ = α · E · Δt using the linear expansion coefficient α, Young's modulus E and temperature difference Δt, and the unit length is Force F acting on the axial cross section (cross-sectional area S)
Can be represented by F = Sθ. Therefore, the maximum thickness T of the scale that can be broken can be found by finding the breaking stress of the scale. For example, the coefficient of linear expansion α is 1.2 × 10 ⁻⁴ [° C. ⁻¹ ], and the Young's modulus E is 54.
Inner tube 18 made of polybutene of 00 [kgf / cm ² ]
When (wall thickness 2 [mm]) is used, the temperature difference Δt is 50
When [° C], 0.324 [kgf / m from the above formula
m ² ], thermal stress acts, and a force F of 6.48 kg acts on the axial cross section (cross-sectional area S = 20 [mm ² ]) per length of 10 mm. If the fracture stress σ ′ of the scale attached to the inner surface of the inner pipe 18 is 3.00 [kgf / mm ² ], the maximum scale thickness T of the scale that can be destroyed by thermal expansion and contraction of the inner pipe 18
Can be calculated by the formula T = F / (10 × σ ′), and the thickness T =
0.216 [mm] can be obtained. Therefore, by examining in advance the period until the thickness of the scale reaches 0.216 [mm], it is possible to know the appropriate time for removing the scale. Since the yield point stress of the inner pipe 18 is 1.7 [kgf / mm ² ] at 20 [° C], for example, when the temperature difference Δt is 100 [° C] (thermal stress σ = 0.648 [ Even with kgf / mm ² ]), a sufficient safety factor (= 2.6) can be obtained. When the inner tube 18 is made of vinyl chloride, the thermal stress σ reaches the yield point stress.
It will be destroyed.

According to this embodiment, since the inner tube 18 is made of a polyolefin resin having high strength, there is no problem that the inner tube 18 is broken by the pressure of the cold spring flowing inside the inner tube 18. . Therefore, it is not necessary to provide a pressure adjusting valve or the like as in the conventional case, the configuration can be simplified, and the manufacturing cost can be reduced. Moreover, since the scale adhering to the inner surface of the inner pipe 18 is removed by heating the inner pipe 18 and then rapidly cooling it, the inner pipe 18
Therefore, maintenance cost can be reduced.

In the above embodiment, the housing 12
Although tap water or the like is heated by the water heater 24 arranged outside the water heater, as shown in FIG. 5, for example, a heater 42 is attached to the tank 20, and the heater 42 heats tap water or the like. You may do it. A heat exchanger 44 of another embodiment shown in FIG. 6 is for heating tap water or the like using a hot spring. In this embodiment, the double tube 1
4, the tank 20, the pump 22 and the like are connected to each other by using the pipe 26, valves 46a to 46f, check valves 48a and 48b and the like. A discharge pipe 50 is connected to one end of the inner pipe 18 through a valve 46a, and an introduction pipe 52 for introducing a hot spring and a water pipe 54 for introducing tap water are provided at the other end of the valve. 46e and 46
It is connected via f. Also, at one end of the outer pipe 16,
A water pipe 56 is connected via a valve 46b, and a supply pipe 58 is connected to the other end via a valve 46d.

When heating tap water, the valve 46 is used.
a, 46b, 46c, 46d and 46e are opened,
The valve 46f is closed and the pump 22 is activated. Then, the hot spring introduced from the introduction pipe 52 and the water introduced from the water pipe 56 flow in the heat exchanger 44 as shown by solid arrows and broken arrows in FIG. 7, respectively. That is, the hot spring provided to the inner pipe 18 through the valve 46e is discharged through the valve 46a, while the tap water provided to the outer pipe 16 through the valve 46b and the check valve 48a is stored in the tank 20, the pump 22, the valve 46d and the tap water. It is supplied to a predetermined place through the supply pipe 58. At this time, a part of the tap water discharged from the pump 22 is partially discharged from the circulation path 60, the valve 46c, and the check valve 48b.
To the outer tube 16 again. In the double pipe 14, a hot spring flows through the inner pipe 18 and tap water flows through the outer pipe 16, so that the hot water heats the tap water to a predetermined temperature.

When the scale adheres to the inner surface of the inner pipe 18, the valve 46f is opened to allow tap water to flow into the inner pipe 18 and increase the flow velocity in the inner pipe 18 to remove the scale. In this embodiment also, for example, the heater 62 (FIGS. 8 and 9) is provided in the tank 20, and the inner pipe 18 is provided.
The scale may be removed by heating and then rapidly cooling.

The operation of removing the scale will be described below. First, the valves 46a, 46c and 46e are opened, the valves 46b, 46d and 46f are closed,
Then, the pump 22 and the heater 62 are operated. Then, the hot spring introduced from the introduction pipe 52 flows as shown by the solid line arrow in FIG. 8, the hot water heated by the heater 62 flows as shown by the broken line arrow in FIG. 8, and the inner pipe 18 moves to the inner and outer surfaces thereof. Heated from both. When the inner tube 18 is sufficiently heated, the valves 46b, 46d and 46f are opened, the valves 46c and 46e are closed, and the heater 62 is turned off. Then, the water pipe 54
The water introduced from flows as shown by the solid line arrow in FIG.
The water introduced from the water pipe 56 flows as shown by the broken line arrow in FIG. 9, the inner pipe 18 is rapidly cooled from both its inner surface and outer surface, and the inner surface of the inner pipe 18 is changed in the same manner as in the previous embodiment. The scale adhered to is destroyed and removed.

[Brief description of drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention.

FIG. 2 is a piping diagram of the embodiment shown in FIG.

FIG. 3 is an illustrative view showing a flow of hot water when the inner pipe is heated in the embodiment of FIG.

FIG. 4 is an illustrative view showing a flow of water when cooling the inner pipe in the embodiment of FIG.

FIG. 5 is an illustrative view showing a state in which a heater is used instead of the water heater in the embodiment of FIG.

FIG. 6 is an illustrative view showing another embodiment of the present invention.

FIG. 7 is a piping diagram of the embodiment shown in FIG.

FIG. 8 is an illustrative view showing a flow of hot water when the inner pipe is heated in the embodiment of FIG.

FIG. 9 is an illustrative view showing a flow of water when the inner pipe is cooled in the embodiment of FIG.

[Explanation of symbols]

 10, 44 ... Heat exchanger 12 ... Housing 14 ... Double pipe 16 ... Outer pipe 18 ... Inner pipe 20 ... Tank 22 ... Pump 24 ... Water heater

Claims (2)

[Claims] 1. A double pipe line comprising an outer pipe and an inner pipe made of a polyolefin resin, which is inserted into the outer pipe, and comprises cold water or warm water flowing in the outer pipe and the inner pipe. A heat exchanger designed to exchange heat with hot or cold water. 2. A method for cleaning a double pipe including an outer pipe and an inner pipe inserted into the outer pipe, wherein hot water is poured into both the outer pipe and the inner pipe at the same time, and then cold water is simultaneously fed. A method for cleaning a double pipe, wherein the inner pipe is expanded and contracted by flowing a flow of water to remove deposits attached to the inner pipe.