A phase change material composite structure for radiation shielding and a preparation method and application thereof

Abstract

The application relates to a phase change material composite structure for radiation shielding and a preparation method and application thereof, and belongs to the technical field of spacecrafts. According to natural radiation environment, ionizing radiation conditions of a reactor to an aircraft platform and single-machine anti-radiation capability, and in combination with the heat transfer capacity, mechanical properties, processing difficulty and radiation shielding efficiency of metal materials, a suitable metal material is selected, and a corresponding shell thickness is designed according to the attenuation law of gamma rays in a substance; according to the working temperature and heat consumption of an extravehicular single machine, and external heat flow conditions, a paraffin material with suitable phase change latent heat and phase change temperature is selected, high-temperature phase change materials can be used for inhibiting the temperature rise of short-term high-heat-consumption working equipment, and low-temperature phase change materials can be used for storing heat at high temperature and releasing the stored heat at low temperature for equipment heat preservation. The required paraffin thickness is designed according to the neutron radiation conditions of a reactor to an aircraft platform, single-machine anti-radiation capability and the attenuation law of neutron flux in paraffin.

Description

Technical Field

[0001] This invention relates to a phase change material composite structure for radiation shielding, its preparation method, and its application, belonging to the field of spacecraft technology. Background Technology

[0002] With the development of the space industry, missions such as deep space exploration have placed higher demands on energy supply. The application of space reactors is an inevitable choice. However, space reactors produce high fluxes of neutrons and gamma rays. These neutral particles have strong penetrating power and, compared to charged particles such as electrons and protons in the space environment, will cause more severe radiation effects on individual components of the spacecraft. Among them, extravehicular components such as star sensors and surveillance cameras are highly sensitive to neutrons and gamma rays. Due to the lack of shielding conditions outside the spacecraft, these components will be subjected to more particle radiation; on the other hand, these components have high operating temperature requirements, but thermal control measures are difficult to implement.

[0003] Currently, the application of space reactors is in its early stages, and there is no mature external single-unit local radiation shielding solution. Its thermal control is mainly achieved through active thermal control, passive thermal control, and hybrid control methods that combine passive and active thermal control, such as attaching additional heat sinks and covering with thermal control materials.

[0004] Currently, the application of space reactors is in its early stages, and there is no mature local radiation shielding solution for external single-unit systems, making it impossible to effectively reduce radiation damage from reactor neutrons and gamma rays to these systems. Furthermore, existing local shielding methods lack passive thermal control capabilities for external single-unit systems. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a phase change material composite structure for radiation shielding, its preparation method, and its application.

[0006] The technical solution of this invention is:

[0007] A phase change material composite structure for radiation shielding, the composite structure comprising a shell, a paraffin-based phase change material located inside the shell, and a heat-conducting plate located on one side of the shell;

[0008] The shell is made of a metallic material, such as aluminum, copper, tungsten, lead, tantalum, chromium, stainless steel, or magnesium-aluminum alloy.

[0009] The shell wall thickness is determined by the following formula:

[0010] N = N0e -μd

[0011] Where N0 is the number of gamma photons before passing through the shell, N is the number of gamma photons after passing through the shell, d is the shell wall thickness, and μ is the linear attenuation coefficient of gamma photons in the shell;

[0012] The thickness of the inner cavity of the shell is determined by the following formula:

[0013]

[0014] Where D is the thickness of the shell cavity. The neutron fluence rate at the exit position of the shell. It is the neutron fluence rate at the incident position in the shell, and L is the relaxation length of the neutron in the shell (i.e. the length at which the neutron fluence rate decays to 1 / e).

[0015] The cross-section of the shell must cover the projection of the equipment in the direction of particle incidence in the reactor;

[0016] The shell side is designed with injection holes for paraffin-based phase change materials;

[0017] The paraffin-based phase change material is n-undecane, n-tridecane, n-pentadecanane, n-octadecane, n-nonadecanane, n-timodecane, n-timodecane, n-timodecane, n-pentadecanane, n-timodecane, n-hexadecane, n-octadecane, n-nonadecanane, or n-triadecane;

[0018] The heat-conducting plate is made of metallic materials (such as aluminum, aluminum alloy, copper, etc.) or non-metallic materials (aluminum-based silicon carbide, high thermal conductivity graphite, diamond, high thermal conductivity carbon fiber, aluminum-based diamond, etc.).

[0019] A method for preparing a phase change material composite structure for radiation shielding, the method comprising the following steps:

[0020] The first step is to prepare the shell, paraffin-based phase change material, and heat-conducting plate;

[0021] The second step involves injecting paraffin-based phase change material into injection holes designed on the side of the shell, and then placing the prepared heat-conducting plate on one side of the shell.

[0022] An application of a phase change material composite structure for radiation shielding involves fixing the resulting composite structure to the neutral particle incident direction of the equipment using screws or other means, according to the reactor direction (i.e., the neutral particle incident direction). Thermally conductive fillers (such as thermal grease, thermal adhesive, or thermal pads) are filled between the heat-conducting plate and the equipment shell to increase thermal conductivity.

[0023] Beneficial effects

[0024] (1) Based on the natural radiation environment, the ionizing radiation conditions from the reactor to the aircraft platform and the radiation resistance capability of the single unit, this invention selects suitable metal materials, such as aluminum, copper, tungsten, lead, tantalum, chromium, stainless steel, magnesium-aluminum alloy, etc., according to the attenuation law of gamma rays in matter and follows the design of the corresponding shell thickness.

[0025] (2) Based on the working temperature and heat consumption of the single unit outside the cabin and the external heat flow conditions, the present invention selects paraffin materials with suitable latent heat of phase change and phase change temperature. High temperature phase change materials can be used to suppress the temperature rise of equipment with high heat consumption in a short period of time; low temperature phase change materials can be used to store heat at high temperature and release the stored heat at low temperature for the insulation of the equipment.

[0026] (3) The present invention designs the required paraffin thickness based on the neutron radiation conditions from the reactor to the aircraft platform, the radiation resistance capability of a single unit, and the decay law of the neutron flux rate in paraffin.

[0027] (4) The structure designed by this method can shield against both the natural radiation environment and the neutrons and gamma generated by the reactor. Neutron shielding and slowing down are mainly achieved by the paraffin filling the shell; shielding against the natural radiation environment and gamma is mainly achieved by the metal material of the shell.

[0028] (5) The structure designed by this method can not only provide radiation shielding, but also play a role in thermal control of the equipment through the phase change properties of paraffin. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0030] Figure 2 This is a schematic diagram of a phase change material composite structure. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Based on the natural radiation environment, the ionizing radiation conditions from the reactor to the spacecraft platform, and the radiation resistance capability of the individual unit, and considering the heat transfer capacity, mechanical properties, processing difficulty, and radiation shielding effectiveness of the metal materials, a suitable metal material is selected. Based on the operating temperature, heat consumption, and external heat flow conditions of the external unit, a paraffin material with suitable latent heat of phase change and phase change temperature is selected. Based on the neutron radiation conditions from the reactor to the spacecraft platform and the radiation resistance capability of the individual unit, the required paraffin thickness is designed. A sealed shell is fabricated from the selected metal material, with an inner thickness equal to the required paraffin thickness, and the shell's cross-section must cover the projection of the equipment in the particle incident direction. Paraffin injection holes are designed on the side of the shell. The selected type of paraffin is filled into the shell through these injection holes. According to the reactor direction (i.e., the neutral particle incident direction), this structure is installed and fixed to the neutral particle incident direction side of the equipment using screws or other methods.

[0033] A phase change material composite structure for radiation shielding, the composite structure comprising a shell, a paraffin-based phase change material located inside the shell, and a heat-conducting plate located on one side of the shell;

[0034] The shell is made of a metallic material, such as aluminum, copper, tungsten, lead, tantalum, chromium, stainless steel, or magnesium-aluminum alloy.

[0035] The shell wall thickness is determined by the following formula:

[0036] N = N0e -μd

[0037] Where N0 is the number of photons before passing through the shell, N is the number of photons after passing through the shell, d is the shell wall thickness, and μ is the linear attenuation coefficient of photons in the shell;

[0038] The thickness of the inner cavity of the shell is determined by the following formula:

[0039]

[0040] Where D is the thickness of the shell cavity. The neutron fluence rate at the exit position of the shell. It is the neutron fluence rate at the incident position of the shell, and L is the relaxation length of the neutron in the shell (i.e. the length at which the neutron fluence rate decays to 1 / e).

[0041] The cross-section of the housing needs to cover the projection of the device in the direction of particle incidence;

[0042] The shell side is designed with injection holes for paraffin-based phase change materials;

[0043] The paraffin-based phase change material is n-undecane, n-tridecane, n-pentadecanane, n-octadecane, n-nonadecanane, n-timodecane, n-timodecane, n-timodecane, n-pentadecanane, n-timodecane, n-hexadecane, n-octadecane, n-nonadecanane, or n-triadecane;

[0044] The heat-conducting plate is made of metallic materials (such as aluminum, aluminum alloy, copper, etc.) or non-metallic materials (aluminum-based silicon carbide, high thermal conductivity graphite, diamond, high thermal conductivity carbon fiber, aluminum-based diamond, etc.).

[0045] Example

[0046] like Figure 1 As shown, a method for preparing a phase change material composite structure for radiation shielding includes the following steps:

[0047] The first step is to prepare the shell, paraffin-based phase change material, and heat-conducting plate;

[0048] The second step involves injecting paraffin-based phase change material into injection holes designed on the side of the shell, and then placing the prepared heat-conducting plate on one side of the shell.

[0049] An application of a phase change material composite structure for radiation shielding involves fixing the obtained structure to the neutral particle incident direction of the equipment using screws or other means, according to the reactor direction (i.e., the neutral particle incident direction). Thermally conductive fillers (such as thermal grease, thermal adhesive, or thermal pads) are filled between the heat-conducting plate and the equipment shell to increase thermal conductivity.

[0050] like Figure 2 As shown, in this embodiment, the shell wall thickness d = 1 cm, the shell material is aluminum alloy, the shell cavity thickness D = 4 cm, and the paraffin-based phase change material is n-pentadecane. Simulation calculations were performed on the equipment with the added composite structure. The results show that in a typical 800 km Earth orbit, this composite structure can reduce the total natural radiation dose in the shielding direction by more than 95%; 1.33 MeV-γ by about 28%; and the energy spectrum shift damage dose of a typical fast neutron reactor by more than 35%. Simultaneously, paraffin can provide a latent heat of phase change of approximately 0.74 kJ / cm². 2 .

Claims

1. A phase change material composite structure for radiation shielding, characterized in that: The composite structure includes a shell, a paraffin-based phase change material located inside the shell, and a heat-conducting plate located on one side of the shell; The shell is made of aluminum alloy, with a shell wall thickness d = 1 cm and an inner cavity thickness D = 4 cm. The paraffin phase change material is n-pentadecane. The cross-section of the shell must cover the projection of the equipment in the direction of particle incidence in the reactor; The shell side is designed with injection holes for paraffin-based phase change materials; The heat-conducting plate is made of aluminum, aluminum alloy, copper, aluminum-based silicon carbide, high thermal conductivity graphite, diamond, high thermal conductivity carbon fiber, or aluminum-based diamond. The method for preparing a phase change material composite structure for radiation shielding includes the following steps: The first step is to prepare the shell, paraffin-based phase change material, and heat-conducting plate; The second step is to inject paraffin-based phase change material into the injection holes designed on the side of the shell, and place the prepared heat-conducting plate on one side of the shell. Based on the reactor direction, i.e. the neutral particle incident direction, the obtained composite structure is fixed on the side of the equipment with the neutral particle incident direction, and thermally conductive filler is filled between the heat-conducting plate and the equipment shell.

2. The phase change material composite structure for radiation shielding according to claim 1, characterized in that: The composite structure is fixed to the side of the device in the direction of neutral particle incidence by screws. The thermally conductive filler between the heat-conducting plate and the equipment housing is thermally conductive grease, thermally conductive adhesive, or thermally conductive pad.

Images