Arc-shaped fin phase change heat accumulator

Abstract

The arc-shaped fin phase change heat accumulator comprises a shell pipe and a heat conduction fluid flow channel, the heat conduction fluid flow channel is located in the center of the shell pipe, a plurality of fin sets are arranged on the outer side wall of the heat conduction fluid flow channel, and each fin set comprises a straight fin and a plurality of arc-shaped branch fins. The straight fins are arranged in the radial direction of the heat conduction fluid flow channel, the arc-shaped branch fins are fixedly connected with the straight fins, and the bending direction of the arc-shaped branch fins is opposite to the heat conduction fluid flow channel. The arc radius of the arc-shaped branch fins is gradually decreased from the arc-shaped branch fins far away from the heat-conducting fluid flow channel to the arc-shaped branch fins close to the heat-conducting fluid flow channel, and the space between the shell pipe and the heat-conducting fluid flow channel is filled with phase change heat storage materials. The phase-change heat storage device is simple in structure, convenient to machine and manufacture and low in cost, and efficient heat exchange between the heat-conducting fluid in the heat-conducting fluid flow channel and the phase-change heat storage material outside the heat-conducting fluid flow channel is achieved.

Description

Technical Field

[0001] The invention relates to a phase-change heat accumulator, in particular to an arc-shaped fin phase-change heat accumulator. Background Art

[0002] The development of clean energy and the utilization of low-grade industrial waste heat have received more and more attention. However, industrial waste heat and the most common solar energy output among renewable energy sources are intermittent and unstable, making thermal energy storage technology the focus of attention in solving the utilization of new energy and low-grade industrial waste heat. Latent heat energy storage has attracted attention for its advantages such as high energy storage density and small volume space. This system not only has high energy density, but also can achieve approximately constant temperature control during the heat storage and release process, thereby effectively avoiding the energy loss caused by temperature changes in traditional energy storage methods.

[0003] Traditional latent heat storage systems have limitations in heat exchange efficiency, which restricts their performance in practical applications. How to quickly and efficiently transfer the heat of the heat transfer fluid to the PCM (phase change material) has always been a hot topic of research. In traditional latent heat storage systems, the heat of the high-temperature fluid in the central heat transfer fluid flow channel is transferred to the PCM through rectangular fins to improve the thermal efficiency of the system. However, due to the low thermal conductivity of common phase change thermal storage materials, the PCM melting rate is slow in areas far away from the rectangular fins and the walls of the central heat transfer fluid flow channel, and the thermal efficiency of the system is poor. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a curved fin phase change heat accumulator to solve the problem of slow melting rate of PCM far away from the rectangular fins and the wall of the central heat transfer fluid flow channel and poor system thermal efficiency.

[0005] The technical solution of the present invention is as follows: an arc-shaped fin phase change heat accumulator, comprising an outer shell tube and a heat transfer fluid flow channel, wherein the heat transfer fluid flow channel is located at the center of the outer shell tube, and the outer side wall of the heat transfer fluid flow channel is provided with a plurality of fin groups, wherein the fin groups include straight fins and a plurality of arc-shaped branched fins, wherein the straight fins are arranged radially along the heat transfer fluid flow channel, the arc-shaped branched fins are fixedly connected to the straight fins, and the bending direction of the arc-shaped branched fins is away from the heat transfer fluid flow channel, and the arc radius of the arc-shaped branched fins decreases from the arc-shaped branched fins away from the heat transfer fluid flow channel to the arc-shaped branched fins close to the heat transfer fluid flow channel, and phase change heat storage material is filled between the outer shell tube and the heat transfer fluid flow channel.

[0006] Furthermore, the spacing between the arc-shaped fins in the fin group is an arithmetic progression, and the spacing between the two arc-shaped fins closest to the heat transfer fluid flow channel is the smallest.

[0007] Furthermore, the arc radius of the arc-shaped fins in the fin group is an arithmetic progression, and the arc radius of the arc-shaped fin closest to the heat transfer fluid flow channel is the smallest.

[0008] Furthermore, the fin groups are equally distributed in the circumferential direction of the heat transfer fluid flow channel.

[0009] Furthermore, the number of fin groups is no less than three.

[0010] Furthermore, each arc-shaped fin in the fin group is arranged symmetrically with the straight fin as a symmetry plane.

[0011] Furthermore, the arc angles of the arc-shaped fins in the fin group are the same, and are all 40° to 50°, for example, 40°, 45°, or 50°.

[0012] Furthermore, the phase change thermal storage material is a crystalline hydrated salt or paraffin or fatty acid phase change material.

[0013] Furthermore, an end plate is provided at the end of the arc-shaped fin phase-change heat accumulator, and the end plate is sealedly connected to the outer shell tube and the heat transfer fluid flow channel respectively.

[0014] Furthermore, the outer shell tube is coated with heat insulating material.

[0015] Compared with the prior art, the advantages of the technical solution provided by the present invention are:

[0016] The present invention rapidly transfers the heat of the heat-conducting fluid to the phase-change thermal storage material through each fin group to promote its melting, and stores the heat in the form of latent heat for subsequent reuse. The present invention has a simple structure, is easy to process and manufacture, and has a low cost. The arc-shaped fins embedded in the straight fins can effectively promote the melting of the phase-change thermal storage material away from the traditional rectangular straight fins, and realize the efficient heat exchange between the heat-conducting fluid in the heat-conducting fluid flow channel and the phase-change thermal storage material outside the heat-conducting fluid flow channel, greatly improving the thermal efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of the arc-shaped fin phase change heat accumulator of Example 1.

[0018] Figure 2 This is a schematic diagram of the cross-sectional structure of the arc-shaped fin phase change heat accumulator of Example 1.

[0019] Figure 3 This is a schematic diagram of the cross-sectional structure of the arc-shaped fin phase change heat accumulator of Example 1 (with dimension markings).

[0020] Figure 4 This is a schematic diagram of the cross-sectional structure of the arc-shaped fin phase change heat accumulator of Example 2.

[0021] Figure 5 Schematic diagram of the cross-sectional structure of the phase change heat accumulator of the comparative example.

[0022] Figure 6 It is the evolution diagram of the liquid phase fraction of the heat storage tank of the embodiment and the comparative example.

[0023] Figure 7 It is a comparison chart of the comprehensive performance of the heat accumulator of the embodiment and the comparative example. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading this description, various equivalent modifications to this description by those skilled in the art fall within the scope defined by the claims attached to this application.

[0025] Example 1, please combine Figures 1 to 3 As shown, the arc-shaped fin phase change heat storage device of this embodiment includes a shell tube 1 and a heat transfer fluid flow channel 2. The heat transfer fluid flow channel 2 is located in the center of the shell tube 1. The heat transfer fluid in the heat transfer fluid flow channel 2 is water, ethanol or propanol. The shell tube 1 can be coated with a heat insulation material. The diameter of the shell tube 1 is R out =35mm, the diameter of the heat transfer fluid channel 2 is R in =10mm.

[0026] The outer wall of the heat transfer fluid flow channel 2 is evenly distributed with four groups of fins along the axial direction. Each fin group includes a straight fin 3 and three arc-shaped sub-fins 4, wherein the straight fin 3 is arranged along the radial direction of the heat transfer fluid flow channel 2, the arc-shaped sub-fins 4 are fixedly connected to the straight fins 3, and each arc-shaped sub-fin 4 is symmetrically arranged with the straight fin 3 as the symmetry plane. The bending direction of the arc-shaped sub-fin 4 is opposite to the heat transfer fluid flow channel 2, and the arc radius of the arc-shaped sub-fin 4 decreases from the arc-shaped sub-fin 4 away from the heat transfer fluid flow channel 2 to the arc-shaped sub-fin 4 close to the heat transfer fluid flow channel 2. In this embodiment, the arc angles of the arc-shaped sub-fins 4 in the fin group are the same, and are all 45°. In other embodiments, it can be 40° or 50°. The spacing L of the arc-shaped sub-fins 4 in the fin group i (i=1,2,3) is an arithmetic progression, and its common difference d=L i-1 -L i (i=2,3), the distance between the two arc-shaped wings 4 closest to the heat transfer fluid flow channel 2 is the smallest. The arc radius R of the three arc-shaped wings 4 i (i=1,2,3) is an arithmetic progression, and the arc radius of the arc-shaped fin 4 closest to the heat transfer fluid flow channel 2 is the smallest. The thickness of the straight fin 3 and the arc-shaped fin 4 is W r, the length of the straight fin 3 is L. The phase change heat storage material 5 is filled between the shell tube 1 and the heat transfer fluid flow channel 2, which is a crystalline hydrated salt or paraffin or fatty acid phase change material. The end of the arc fin phase change heat storage device is also provided to the end plate, which is sealed and connected to the shell tube 1 and the heat transfer fluid flow channel 2 respectively through the end plate to prevent leakage of the heat transfer fluid.

[0027] Example 2, please combine Figure 4 As shown, the difference between the arc-shaped fin phase-change heat storage structure of this embodiment and that of embodiment 1 is that in each fin group, the arrangement spacing of each arc-shaped sub-fin 4 is equal, and the rest of the structure and size are the same as those of embodiment 1.

[0028] For comparison, please combine Figure 5 As shown, the difference between the fin phase change heat storage structure of this comparative example and that of Example 1 is that each fin group includes a radial straight fin 6 and three tangential straight fins 7, and the tangential straight fins 7 are arranged at equal intervals on the radial straight fins 6, and the length of the tangential straight fins 7 decreases from the tangential straight fins 7 far away from the heat transfer fluid flow channel 2 to the tangential straight fins 7 close to the heat transfer fluid flow channel 2. The volume of the filling space of the phase change heat storage material 5 between the shell tube 1 and the heat transfer fluid flow channel 2 is the same as that of Example 1.

[0029] The performance of the phase change heat storage devices of the embodiments and comparative examples was evaluated.

[0030] The size parameters of the phase change heat storage device of the embodiment and the comparative example are shown in the following table

[0031] <![CDATA[W r / mm]]> d / mm L / mm <![CDATA[R1 / mm]]> <![CDATA[R2 / mm]]> <![CDATA[R3 / mm]]> θ / ° Comparative Example 1 0 18 - - - - Example 1 1 1 18 16 22 28 45 Example 2 1 0 18 16 22 28 45

[0032] Specific evaluation indicators include:

[0033] The liquid phase ratio β of phase change thermal storage material can be expressed as:

[0034]

[0035] Where, T s is the PCM solidus temperature; T l is the liquidus temperature of PCM; β∈(0,1) represents the mushy region.

[0036] The liquid fraction f of the phase change thermal storage material is the ratio of the melted PCM to the total volume of PCM, which can be expressed as:

[0037]

[0038] In the formula, v PCM is the total volume of the phase change thermal storage material, and β is the liquid phase ratio of the phase change thermal storage material at different stages.

[0039] Phase change heat storage capacity Q PCM It can be expressed as:

[0040] Q PCM =m PCM ·[c p (TT ref )+β·ΔH]

[0041] In the formula, m PCM and c p are the mass and specific heat of the phase change thermal storage material, respectively; T and T ref are the instantaneous average temperature and initial reference temperature of the phase change thermal storage material in the system, respectively; β is the liquid fraction of PCM, and ΔH is the latent heat of melting.

[0042] The heat storage efficiency of the phase change heat storage device can be expressed as:

[0043]

[0044] Where, T end is the average temperature of the phase change thermal storage material when the PCM is completely melted, t end It is the time for the phase change thermal storage material to completely melt.

[0045] like Figure 6 As shown, the arc-shaped fin phase change heat storage device proposed in the present invention can effectively improve the thermal efficiency of the system. Figure 7 As shown, compared with the traditional straight-fin phase-change heat accumulator (comparative example), the uniformly distributed arc-shaped fin phase-change heat accumulator (Example 2) can shorten the energy storage time of the system by 15.46%, and the energy storage efficiency is improved by 18.87%; the arc-shaped fin phase-change heat accumulator with equidistant spacing distribution (Example 1) further shortens the energy storage time by 2.50% and improves the energy storage efficiency of the phase-change heat accumulator by 2.55% based on Example 1.

Claims

1. An arc-shaped fin phase-change heat accumulator, comprising a shell tube and a heat transfer fluid flow channel, wherein the heat transfer fluid flow channel is located at the center of the shell tube, and the outer side wall of the heat transfer fluid flow channel is provided with a plurality of fin groups, characterized in that: The fin group includes straight fins and a plurality of arc-shaped fins, the straight fins are arranged along the radial direction of the heat-conducting fluid flow channel, the arc-shaped fins are fixedly connected to the straight fins, the bending direction of the arc-shaped fins is away from the heat-conducting fluid flow channel, the arc radius of the arc-shaped fins decreases from the arc-shaped fins away from the heat-conducting fluid flow channel to the arc-shaped fins close to the heat-conducting fluid flow channel, and phase change heat storage material is filled between the shell tube and the heat-conducting fluid flow channel.

2. The arc-shaped fin phase change heat storage device according to claim 1, characterized in that: The spacing between the arc-shaped fins in the fin group is an arithmetic progression, and the spacing between the two arc-shaped fins closest to the heat transfer fluid flow channel is the smallest.

3. The arc-shaped fin phase change heat storage device according to claim 1 or 2, characterized in that: The arc radius of the arc-shaped fins in the fin group is an arithmetic progression, and the arc radius of the arc-shaped fin closest to the heat transfer fluid flow channel is the smallest.

4. The arc-shaped fin phase-change heat storage device according to claim 1, characterized in that: The fin groups are equally distributed in the circumferential direction of the heat transfer fluid flow channel.

5. The arc-shaped fin phase-change heat storage device according to claim 4, characterized in that: The fin groups are provided with no less than three groups.

6. The arc-shaped fin phase-change heat storage device according to claim 1, characterized in that: Each arc-shaped fin in the fin group is symmetrically arranged with the straight fin as a symmetry plane.

7. The arc-shaped fin phase-change heat storage device according to claim 1, characterized in that: The arc angles of the arc-shaped fins in the fin group are the same, and are all 40° to 50°.

8. The arc-shaped fin phase-change heat storage device according to claim 1, characterized in that: The phase change heat storage material is a crystalline hydrated salt or paraffin or fatty acid phase change material.

9. The arc-shaped fin phase-change heat storage device according to claim 1, characterized in that: An end plate is provided at the end of the arc-shaped fin phase-change heat accumulator, and the end plate is sealed and connected to the shell tube and the heat-conducting fluid flow channel respectively.

10. The arc-shaped fin phase-change heat storage device according to claim 1, characterized in that: The outer shell tube is coated with heat insulation material.

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