JPH0125998B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of manufacturing a PTFE tube bundle for a heat exchanger. Technical background of the invention and its problems Conventionally, multi-tubular heat exchangers made of metals such as stainless steel, nickel, and copper have been widely used as heat exchangers. Although such metal heat exchangers have high thermal conductivity and overall heat transfer coefficient, they have problems such as insufficient corrosion resistance against acid solutions and the tendency for scale to adhere to the surface. Ta. For this reason, multi-tubular heat exchangers made of fluororesin have been developed. This fluororesin heat exchanger has a structure in which a large number of fluororesin heat exchanger tubes are bundled together and integrated into a honeycomb shape by heat fusion at both ends, and has excellent heat resistance and chemical resistance. It also has the advantage of having a smooth surface that prevents scale from adhering to it. However, in the above-mentioned fluororesin heat exchanger, it is necessary to integrate the ends of a large number of fluororesin tubes into a honeycomb shape by heat fusion, so it is necessary to use fluororesin tubes that have heat-melting properties. It was necessary to use it. For this reason, examples of fluororesin include FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene),
PFA (perfluoroalkoxy group - equivalent to polytetrafluoroethylene with OR _f introduced into the side chain)
However, tetrafluoroethylene (PTFE), which has the best mechanical strength, heat resistance, chemical resistance, and stain resistance, could not be used in practice. This is because heat-sealing PTFE tubes together was not easily accomplished because PTFE is extremely non-stick.
Furthermore, even if a tube bundle made of PTFE were obtained, the tubes would not be sufficiently integrated, resulting in gaps between the tubes, resulting in poor sealing performance and insufficient mechanical strength. It could not be used effectively as a heat exchanger. By the way, if it is possible to create a tube bundle for a heat exchanger made of PTFE with sufficient mechanical strength and sealing performance, compared to a tube bundle for a heat exchanger made of FEP or PFA,
It is expected that a heat exchanger with even better mechanical strength, heat resistance, chemical resistance, and stain resistance will be obtained. Purpose of the Invention The present invention provides a method for achieving mechanical strength among fluororesins.
Heat resistance, chemical resistance (corrosion resistance), and stain resistance (property that prevents the adhesion of scale, etc.)
Using PTFE tubes, which have particularly excellent properties in terms of non-adhesive properties, the ends of each tube are integrated into a honeycomb shape with no gaps between the tubes to achieve sealing and mechanical properties. The present invention aims to provide a method for manufacturing tube bundles for heat exchangers with excellent mechanical strength. In order to achieve such an object, the method for manufacturing a shell-and-tube heat exchanger according to the present invention is such that the inside is filled with a deformable heat-resistant solid material, and the outer periphery of both ends is filled with a heat-melting fluororesin. A plurality of polytetrafluoroethylene tubes with a fixed,
Next, by heating both ends, each tube is integrated, and the outer frame sleeve and each tube are integrated. DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to specific examples shown in the drawings. A multi-tubular heat exchanger 1 according to the present invention, as shown in the front view in FIG. and a PTFE outer frame sleeve 3 fitted around both ends of this tube.
The side portions of each tube are integrated with each other at both ends by heat-melting fluororesin (not shown). Further, the tube 2 and the outer frame sleeve 3 are similarly integrated with heat-melting fluororesin. In this way, each tube 2 and the outer frame sleeve 3 are integrated at both ends with heat-melting fluororesin, and each tube 2 is originally cylindrical, but at both ends, the plan view is
As shown in the figure, it is preferable that the material deforms during heat bonding to form a honeycomb shape. The heat-melting fluororesin used to integrate the PTFE tubes with each other and with the PTFE outer frame corresponds to polytetrafluoroethylene with a perfluoroalkoxy group - OR _f introduced into the side chain. PFA (structural formula

[Formula] In the formula, R _f is a fluorinated alkyl group), FEP (structural formula:

[Formula]), EPE resin (multi-component copolymer of tetrafluoroethylene, hexafluoropropylene, and perfluorovinyl ether), etc. are used. Next, a method for manufacturing a shell-and-tube heat exchanger according to the present invention will be explained. The method of manufacturing a multi-tube heat exchanger made of PTFE according to the present invention is based on the principle that a PTFE outer frame sleeve is provided at the end of a plurality of PTFE tubes, and when this outer frame sleeve is heated, the PTFE The purpose is to press the PTFE tubes together and press the outer sleeve to the tubes using the expansion pressure generated as the outer sleeve thermally expands, and at the same time deform the tubes to form a honeycomb structure. but
If the PTFE tube is used as is, the tube will be deformed or destroyed beyond use due to the expansion pressure of the PTFE outer frame sleeve.
Furthermore, the PTFE tubes are not sufficiently integrated with each other, making it impossible to achieve a complete seal. Therefore, in the present invention, a shell-and-tube heat exchanger is manufactured by the method described below. First, a deformable solid heat-resistant material is filled inside a PTFE tube. This is due to the expansion pressure generated by heating the PTFE outer sleeve.
This is to prevent the PTFE tube from being significantly deformed or destroyed. This deformable solid heat-resistant material is
It is preferable that the PTFE tube is not destroyed by the expansion pressure of the PTFE outer frame sleeve, and that the PTFE tube has enough fluidity to form a honeycomb structure. Specifically, powdered or granular materials are preferred. For example, glass beads, metal powder, inorganic salts, etc. are used. Next, a heat-melting fluororesin is provided on the outer periphery of both ends of the thus obtained plurality of PTFE tubes whose interiors are filled with a heat-resistant material. This hot-melt fluoropolymer serves to integrate the PTFE tubes together. To provide a heat-melting fluororesin on the outer periphery of both ends of the tube, a heat-melting fluororesin film is wrapped around the outer periphery of both ends of the PTFE tube, or a heat-melting fluororesin tube is coated with a PTFE tube. This can be achieved by covering the tube. In this case, it is not necessarily necessary to provide heat-melting fluororesin on the outer periphery of both ends of all PTFE tubes, and as long as the PTFE tubes are integrated, the outer periphery of both ends of some PTFE tubes may be It is not necessary to provide a heat-melting fluororesin. Note that either the step of filling the inside of the PTFE tube with a heat-resistant material or the step of providing a thermoplastic fluororesin on the outer periphery of the end of the tube may be performed first. Next, as shown in FIG. 3, a plurality of PTFE tubes 2 each having a thermofusible fluororesin (not shown) provided on the outer periphery of both ends are gathered together so that both ends are almost aligned. A PTFE outer frame sleeve 3 is fitted around the outer frame, and the outer periphery of this outer frame sleeve is fixed with a fixing frame 4 such as a metal mold. At this time, it is desirable that the outer diameter of the outer frame sleeve be at least 90% or more, preferably 95% or more, of the fixed frame inner diameter. Also, it is desirable to use a PTFE outer frame sleeve with a thick wall and a large outer diameter.
If the outer diameter of the PTFE outer sleeve is less than 90% of the fixed frame inner diameter, it is undesirable because the expansion pressure generated when the outer sleeve is heated is difficult to sufficiently reach the inside. If it is small, it is also not preferable because the expansion pressure is difficult to apply to the inside. A thermofusible fluororesin tube or film is provided for the inner diameter area of the outer sleeve.
The total cross-sectional area of the PTFE tube is preferably 80% or more, preferably 80-85% or more. Further, at this time, in order to effectively apply the expansion pressure generated when heating the outer frame sleeve to the inside, it may be preferable to press the upper surface of the outer frame sleeve. Next, both ends of the PTFE tube are heated from outside the PTFE outer frame sleeve, for example, by a heater 5 provided outside the fixed frame. The heating temperature at this time is 327, which is the melting point of PTFE.
It is preferable that the temperature is slightly higher than ℃, specifically,
Preferably, it is heated to a temperature of 330° to 400°C. When the PTFE outer frame sleeve and PTFE tube are heated by the heater 5, the PTFE is heated to the fixed frame 4.
Due to the expansion pressure generated at this time, the PTFE tube and the outer frame sleeve are pressed together and integrated, and the tube is deformed into a honeycomb shape.
There is no gap between each tube, and a multi-tube heat exchanger with excellent sealing properties, mechanical strength, chemical resistance, etc. can be obtained. Effects of the Invention As explained above, according to the present invention, a heat-melting fluororesin is provided at the end of a non-adhesive PTFE tube, and a plurality of
We bundled PTFE tubes, filled the inside of each tube with a heat-resistant material, and fixed the tube bundle with a PTFE outer frame sleeve around the outer circumference of the tube bundle.This end was heated, so it was easy to heat. By effectively utilizing the accompanying expansion pressure of the tubes, it becomes possible to firmly join the ends of each tube without any gaps. Moreover, at this time, since the tube ends are filled with a heat-resistant material, the tube ends do not collapse each other, forming a uniform honeycomb shape, and the mechanical strength of the tube ends is also improved. Therefore, the tube bundle thus obtained can be preferably used for a heat exchanger.

[Brief explanation of drawings]

FIG. 1 is a front view of a tube bundle for a heat exchanger according to the present invention, FIG. 2 is a plan view of the end thereof, and FIG. 3 is an illustration of the manufacturing process of the tube bundle for a heat exchanger according to the present invention. FIG. 1... Multi-tube heat exchanger, 2... PTFE tube, 3... PTFE outer frame sleeve, 4... Fixed frame, 5... Heater.

Claims (1)

[Claims] 1. A plurality of polytetrafluoroethylene tubes each filled with a deformable solid heat-resistant material and provided with a heat-melting fluororesin on the outer periphery of both ends are gathered together so that both ends are almost aligned. ,
A polytetrafluoroethylene outer sleeve is fitted around both ends, the outer periphery of the outer sleeve is fixed, and then both ends are heated to integrate each tube and the outer sleeve. For heat exchangers, characterized by
Method for manufacturing PTFE tube bundles.