Lightweight anti-pressing electric water heater liner structure

Abstract

The application provides a light-weight and pressure-resistant electric water heater inner container structure, which comprises an upper end cover, a middle barrel and a lower end cover, the upper end cover is connected to the upper end of the middle barrel, and the lower end cover is connected to the lower end of the middle barrel, wherein the middle barrel is in a cylindrical structure, the upper end cover and the lower end cover are vertically symmetrical, the upper end cover is in a semi-elliptical shape in the vertical section through the central axis of the middle barrel, the height of the upper end cover is h1, the inner diameter of the middle barrel is R, the ratio of the major axis to the minor axis of the upper end cover is k1=R / h1, and k1=1.30-1.85; the upper end cover and the lower end cover are made of the same material and have the same thickness, the yield strength of the material of the upper end cover is σ1, the thickness of the upper end cover is t1, the yield strength of the material of the middle barrel is σ2, and the thickness of the middle barrel is t2; t2

Description

Technical Field

[0001] This invention relates to the field of electric water heater inner tank design and manufacturing technology, and in particular to a structure for an electric water heater inner tank that achieves lightweighting through thinning while possessing sufficient pressure resistance. Background Technology

[0002] The inner tank of an electric water heater is the main component used for water storage and is classified as a pressure vessel. Most electric water heater inner tanks on the market are made of enamel-lined steel and are welded together from three parts (the middle tank and two end caps). Because electric water heaters are subjected to internal pressure during operation, pressure resistance is a crucial technical requirement for the inner tank. Depending on the manufacturer, the inner tank undergoes pulse pressure tests of 0.85–1.1 MPa and single-stage extreme pressure tests of approximately 3 MPa. The goal is to prevent deformation or minimal deformation after a certain number of pressure tests to avoid damage to the enamel layer that could lead to leaks.

[0003] On the other hand, in order to save materials and reduce costs, the method of thinning materials is usually adopted. However, simply thinning the materials will inevitably lead to a decrease in the ability to withstand pressure. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an electric water heater inner tank structure that can achieve lightweight design while ensuring sufficient pressure resistance.

[0005] The technical problem it aims to solve can be addressed through the following technical solutions.

[0006] A lightweight, pressure-resistant electric water heater inner tank structure includes an upper end cover, a middle tank, and a lower end cover. The upper end cover is connected to the upper end of the middle tank, and the lower end cover is connected to the lower end of the middle tank. The middle tank is cylindrical, and the upper and lower end covers are symmetrical. In a vertical section passing through the central axis of the middle tank, the upper end cover is semi-elliptical.

[0007] The height of the end cap is h1; the inner diameter of the middle barrel is R; the ratio of the major and minor axes of the end cap ellipse is k1 = R / h1;

[0008] The upper and lower end caps are made of the same material and have the same thickness. The yield strength of the material of the upper end cap is σ1, and the thickness of the upper end cap is t1. The yield strength of the material of the middle barrel is σ2, and the thickness of the middle barrel is t2. Where t2 < t1, and satisfies t2 = t1 * (σ2 / σ1)^0.5 * (0.1116k1 + 0.7141).

[0009] In a preferred embodiment of the present invention, σ2≥σ1.

[0010] As a further improvement to this technical solution, the middle barrel may be made of the same or different ceramic steel material as the upper end cap, as long as the corresponding material performance requirements are met.

[0011] In a preferred embodiment of the present invention, k1 = 1.30 to 1.85.

[0012] As a preferred embodiment of the present invention, k1 = 1.30 to 1.645.

[0013] Preferably, the upper end of the middle bucket is welded to the upper end cap as a single unit, and the lower end of the middle bucket is welded to the lower end cap as a single unit.

[0014] Furthermore, given the different thicknesses of the middle barrel and the upper and lower end caps, during welding, adjacent middle barrels are welded to the upper or lower end caps with the center aligned.

[0015] The inner tank structure using the above technical solution is optimized through inner tank structure design and high-strength thinning of the middle tank. A matching calculation formula for the yield strength and thinning thickness of the thinned material is proposed. This provides a design concept for an electric water heater inner tank that can achieve lightweighting through material thinning while ensuring sufficient pressure resistance. This achieves the technical goal of ensuring sufficient pressure resistance while thinning the material of the middle tank. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the inner tank structure of the lightweight, pressure-resistant electric water heater of the present invention;

[0017] 1 - Top cap, 2 - Bottom cap, 3 - Middle bucket Detailed Implementation

[0018] Reference Figure 1 The inner tank of the lightweight, pressure-resistant electric water heater provided by this invention, as shown in the central cross-sectional shape of the inner tank, consists of three parts: an upper end cover 1, a middle tank 3, and a lower end cover 2. The upper and lower end covers 1 and 2 are arranged symmetrically (and structurally completely symmetrical), and are made of the same material and have the same thickness. The middle tank 3 can be made of the same or different ceramic steel material as the upper and lower end covers, and its thickness is less than that of the end covers. The two end covers are connected to the middle tank by welding, and the diameter of the end covers and the inner wall of the middle tank are consistent.

[0019] The middle bucket 3 adopts a cylindrical structure; on any vertical cross-section passing through the central axis of the middle bucket, the upper end cap 1 is symmetrically arranged with respect to the central axis, forming a structure with a semi-elliptical cross-section; the height of the upper and lower end caps is h1 (half of the minor axis of the ellipse); the inner radius (inner diameter) of the middle bucket is R (half of the major axis of the ellipse), and the height of the middle bucket is h2; the ratio of the major and minor axes of the end cap ellipse is k1 = R / h1, k1 = 1.30~1.85, and k1 is preferably 1.30~1.645.

[0020] The yield strength of the upper and lower end cap materials is σ1, and the thickness of the end cap is t1; the yield strength of the middle barrel material is σ2, and the thickness of the middle barrel is t2; where σ2≥σ1, t2<t1, and satisfying t2=t1*(σ2 / σ1)^0.5*(0.1116k1+0.7141).

[0021] The inner liner maintains sufficient pressure resistance while reducing the thickness of the middle barrel material.

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0023] Comparative example:

[0024] The comparative example is selected from a certain model of electric water heater on the market. The inner tank design of this water heater has an end cap aspect ratio k1 = 1.962, a thickness t1 = 1.8 mm, and a middle tank thickness t2 = 1.8 mm. Both materials have the same yield strength, σ1 = σ2 = 245 MPa. Pressure tests were conducted at 1.1, 1.6, and 3 MPa respectively, and the maximum equivalent plastic strain of the inner tank was calculated to be 0, 0, and 1.86E-03, respectively.

[0025] Example 1:

[0026] The aspect ratio of the upper and lower end caps is k1 = 1.85, the end cap thickness is t1 = 1.8 mm, and the yield strength of the end cap material is σ1 = 245 MPa; the thickness of the middle tank is t2 = 1.8 mm, and the yield strength of the middle tank material is σ2 = 245 MPa. Pressure tests at 1.1, 1.6, and 3 MPa were conducted, and the maximum equivalent plastic strain of the inner liner was calculated to be 0, 0, and 5.78E-04, respectively. The deformation under pressure was significantly reduced simply by optimizing the aspect ratio.

[0027] Example 2:

[0028] The aspect ratio of the upper and lower end caps is k1 = 1.85, the end cap thickness is t1 = 1.8 mm, and the yield strength of the end cap material is σ1 = 245 MPa; the thickness of the middle tank is t2 = 1.5 mm, and the yield strength of the material is σ2 = 299 MPa. Pressure tests at 1.6 MPa and 3 MPa were conducted, and the maximum equivalent plastic strain of the inner liner was calculated to be 0 and 8.45E-04, respectively. Even when the thickness of the middle tank material was reduced from 1.8 mm to 1.5 mm, and the material strength increased from 245 MPa to 299 MPa, the deformation under pressure was still significantly reduced compared to the control group.

[0029] Example 3:

[0030] The aspect ratio of the upper and lower end caps is k1 = 1.645, the end cap thickness is t1 = 1.8 mm, and the yield strength of the end cap material is σ1 = 245 MPa; the thickness of the middle barrel is t2 = 1.8 mm, and the yield strength of the middle barrel material is σ2 = 245 MPa. Pressure tests at 1.1, 1.6, and 3 MPa were conducted, and the maximum equivalent plastic strain of the inner liner was calculated to be 0, 0, and 4.68E-05, respectively. Based on Example 2, the aspect ratio k1 was further optimized to 1.645, resulting in a significant reduction in pressure deformation.

[0031] Example 4:

[0032] The aspect ratio of the upper and lower end caps is k1 = 1.645, the end cap thickness is t1 = 1.8 mm, and the yield strength of the end cap material is σ1 = 245 MPa; the thickness of the middle barrel is t2 = 1.46 mm, and the yield strength of the middle barrel material is σ2 = 299 MPa. Through a 3 MPa pressure test, the maximum equivalent plastic strain of the inner liner was calculated to be 1.96E-04. Reducing the thickness of the middle barrel material from 1.8 mm to 1.46 mm and increasing the material strength from 245 MPa to 299 MPa resulted in a significant reduction in deformation under pressure compared to Example 2.

[0033] Example 5:

[0034] The aspect ratio of the upper and lower end caps is k1 = 1.3, the end cap thickness is t1 = 1.8 mm, and the yield strength of the end cap material is σ1 = 245 MPa; the thickness of the middle tank is t2 = 1.4 mm, and the yield strength of the middle tank material is σ2 = 299 MPa. Through a 3 MPa pressure test, the maximum equivalent plastic strain of the inner liner was calculated to be 0. When the thickness of the middle tank material is reduced from 1.8 mm to 1.4 mm, and the material strength is increased from 245 MPa to 299 MPa, no plastic strain occurs during pressure testing.

[0035] Example 6:

[0036] The aspect ratio of the upper and lower end caps is k1 = 1.3, the end cap thickness is t1 = 1.8 mm, and the yield strength of the end cap material is σ1 = 245 MPa; the thickness of the middle tank is t2 = 1.21 mm, and the yield strength of the middle tank material is σ2 = 400 MPa. Through a 3 MPa pressure test, the maximum equivalent plastic strain of the inner liner was calculated to be 0. When the thickness of the middle tank material is reduced from 1.8 mm to 1.21 mm, and the material strength is increased from 245 MPa to 400 MPa, no plastic strain occurs during pressure testing.

[0037] Table 1 below shows a comparison of the performance and parameters of each embodiment and comparative example.

[0038] Table 1:

[0039]

[0040]

[0041] Referring to Table 1, as can be seen from the above embodiments, based on the method of the present invention, the weight reduction of the middle barrel by 16.7% to 33.3% can be achieved while ensuring sufficient pressure resistance.

Claims

1. A light-weight, pressure-resistant electric water heater liner structure, comprising an upper end cover, a middle barrel and a lower end cover, the upper end of the middle barrel being connected with the upper end cover, and the lower end of the middle barrel being connected with the lower end cover, characterized in that, The middle barrel has a cylindrical structure, and the upper and lower end caps are symmetrical. In the vertical cross-section passing through the central axis of the middle barrel, the upper end cap is semi-elliptical. The height of the end cap is h1; the inner diameter of the middle barrel is R; the ratio of the major and minor axes of the end cap ellipse is k1 = R / h1; The upper and lower end caps are made of the same material and have the same thickness. The yield strength of the material of the upper end cap is σ1, and the thickness of the upper end cap is t1. The yield strength of the material of the middle barrel is σ2, and the thickness of the middle barrel is t2. Where t2 < t1, and satisfies t2 = t1 * (σ2 / σ1)^0.5 * (0.1116k1 + 0.7141).

2. The lightweight, pressure-resistant electric water heater inner tank structure according to claim 1, characterized in that, σ2≥σ1.

3. The lightweight, pressure-resistant electric water heater inner tank structure according to claim 1, characterized in that, The middle bucket is made of ceramic steel material that is the same as or different from that of the top cover.

4. The lightweight, pressure-resistant electric water heater inner tank structure according to claim 1, characterized in that, k1＝1.30～1.85。 5. The lightweight, pressure-resistant electric water heater inner tank structure according to claim 1, characterized in that, k1＝1.30～1.645。 6. The lightweight, pressure-resistant electric water heater inner tank structure according to claim 1, characterized in that, The upper end of the middle barrel is welded to the upper end cap, and the lower end of the middle barrel is welded to the lower end cap.

7. The lightweight, pressure-resistant electric water heater inner tank structure according to claim 6, characterized in that, When welding the middle barrel to the upper or lower end cap, the center of the wall thickness on both sides of the weld should be aligned.

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