Design and simulation of thermal control system for micro nautical satellite
Thermal simulation and optimization of a 3G mobile base station
Thermal analysis of outdoor communication power supply
Thermal analysis of ZTE EDFA module
Case 1 a certain type of micro nautical satellite thermal control system design
Micro nautical satellite: a satellite with a mass of less than 10kg and with practical use functions. The Tiangong-2, which will be launched on September 15-20, will carry a companion satellite that is a micro nautical satellite.
The satellite is mainly composed of load compartment, module box, solar cell sail plate, etc. The load compartment contains micro-inertial combination, battery pack, storage box, camera and other components, which has the function of imaging and information transmission to the ground. The satellite operates in a high-vacuum space environment, and heat transfer is mainly carried out through conduction and radiation.
The purpose of satellite thermal control design is to provide the ambient temperature required for the normal operation of satellite payload and satellite platform instruments and equipment of each sub-system through reasonable thermal design methods and thermal control means, and at the same time to ensure that all the equipment on the surface of the satellite works in the required temperature range.
Follow the principles: the use of mature thermal control technology and implementation process, follow the thermal control norms and standards, and strive to be simple, reliable; the whole star thermal design in line with the passive thermal control mode is the main, in the passive thermal control mode can not meet the requirements, and then consider the active thermal control means of electric heating compensation, and strive to achieve the best thermal coupling mechanism; star general equipment together with the design of the temperature range of the margin of ± 10 ℃.
Thermal control measures :
Taking into account the structure of the satellite, the temperature requirements and the space environment in which it is located, the following thermal control measures are taken.
Except for the propulsion system, the outer surface of other payloads is blackened and the surface blackness ε≥0.8;
ε≥0.5 on the inner surfaces of the module and payload body;
The circuit boards in the module box are filled with heat-conducting material or heat-conducting grease between the circuit boards and their mounting surfaces;
The external surfaces of magnetometers, GPS antennas, etc. located outside the star are painted with organic gray paint or organic black paint a/ε=0.85/0.8;
The software IDEAS TMG establishes the overall finite element model of the satellite and the finite element module of the payload module as follows
The space background is 4K cold black space, and the parameters of orbit and attitude are input (sun-synchronous circular orbit, altitude is taken as 550km, inclination is taken as 95°, local time of descending node is taken as 11:00, etc.), and the three-axis stabilized attitude is taken with the +Z-axis pointing to the center of the earth, and the +X-axis pointing to the direction of flight.
The temperature of each part of the satellite in the steady state is shown in the following table
The following figures show the temperature distribution of the whole satellite, the payload module, the solar cell sail panel, the top plate, and the magnetometer and GPS antenna, respectively Temperature distribution cloud
The simulation results show that the thermal design scheme adopted meets the requirements put forward by the satellite overall, with the temperature of general instruments and equipment in the cabin ranging from 10℃ to +45℃, and the temperature of instruments and equipment outside the cabin ranging from -80℃ to +80℃.
Case 2 Thermal Simulation and Optimization of a 3G Mobile Base Station
1、Actual model
The mobile base station uses a standard 19-inch cabinet with a total of 20 PCB insertion board positions.
a、 Option 1 (top extraction program)
The schematic structure of this program is shown in the right figure. The total height of the cabinet is 10U. Among them, the height of the board insertion area is 7U, the height of the bottom air inlet is 1U, and the height of the top air outlet is 2U. two centrifugal fans from EBM are used, which are placed on the top of the cabinet.
b、 Option two (bottom blowing program)
The schematic structure of this program is shown in the right figure. The total height of the cabinet is 10 U. The height of the bottom air inlet is 2 U, and the height of the top air outlet is 1 U. Six axial fans from EBM are used and placed at the bottom of the cabinet.
c、 Option three (axial fan top air extraction program)
The schematic structure of this program is shown in the right figure. The height of the top air outlet is 2U, and the height of the bottom air inlet is 1U. Other dimensions are the same as Scheme II, which adopts six axial fans from EBM and places them on the top of the cabinet.
Simulation results
a、 Results of numerical analysis for Scenario 1
I
b、Results of numerical analysis for Scenario 2
c、Results of numerical analysis for Scenario 3
Conclusion of simulation
Option 2 has the best cooling effect
Although program three uses the same number and type of axial fans as program two, but because they are placed on the top of the chassis, so that the air outlet and fan axis is perpendicular to each other, thus increasing the wind resistance of the system, and axial fans are characterized by large air volume, wind pressure is small, so the cooling effect of the program three is much lower than that of program two.
Option 1 uses two centrifugal fans, their total air volume is much smaller than six axial fans; and due to the unevenness of the fan distribution, so that the placement of the plug-board location on the temperature distribution of the plug-board has a greater impact on the total heat dissipation effect is also worse than the program two.
Pay attention to the placement of the board
Under different cooling solutions, the PCB board temperature distribution in each board position is different. When there is extra board space, you should pay attention to prioritize the lower temperature board placement PCB.
Case 3 Thermal Analysis of Outdoor Communication Power Supply
Requirement Analysis:
An AC/DC conversion module. Product Overall dimensions of 320 mm in length, 70 mm in width and 255 mm in height.
Totally enclosed structure, the required water proof and dust proof grade is strengthened IP55, that is, the waterproof test conditions of the product is the water temperature is 10 ℃ and the product in the ambient temperature of 60 ℃ under the conditions of operation to the thermal equilibrium of the waterproof test.
The main application environment of the product is outdoor transmitter rack, the heat dissipation method is natural convection, and at the same time there is solar radiation, the product is a fully enclosed structure, the heat generated by the components is mainly through conduction to the metal casing, and then through the natural convection to dissipate the heat.
The main circuit board is mounted on the heat sink as shown on the below. The main circuit board is mounted on the heat sink cover, the circuit board and the heat sink cover are filled with thermally conductive potting glue as a thermal medium for heat dissipation, the heat generating power devices are fixed to the edges of the heat sink cover with compression strips, and a thermally conductive insulating material is used as a thermal conductive medium between the components and the heat sink cover.
The mounting on the heat sink housing of the EMI board is shown in the figure to the below, and the mounting method is similar to that of the main circuit board.
The overall structure of the power supply module, with the heat sink cover housing hermetically mounted and watertight sealed with a rubber strip in the center.
The thermal model created after simplification by Flotherm software is as follows.
For the heat dissipation simulation of the power supply module, the simulation model makes the following assumptions without affecting the solution results:
Heat transfer inside the power module is dominated by conduction, and convection and radiation occupy a very small proportion, so the internal heat transfer only considers conduction heat dissipation and ignores convection and radiation.
The heat transfer between the power module and the external environment is dominated by natural convection, and there is also radiation heat dissipation, so it is necessary to consider natural convection and radiation heat dissipation.
Solar radiation is used as the external heat source.
The internal heat generating element acts as a constant heat source and the amount of heat generated does not change with temperature.
The thermal conductivity of the components within the heat sink system is isotropic and does not vary or change with temperature.
The air within the solution domain is an ideal gas and the effects of mass and force are neglected.
The boundaries and main parameters of the power module are as follows:
Environmental parameters Ambient temperature is 55°C, altitude is assumed to be sea level, air properties are defined as 55 ℃ fluid, natural convection heat dissipation, fluid velocity is less than 1.0m / s, outdoor installation equipment with solar radiation.
Power Module Dimensions Product external dimensions are 320 mm long, 70 mm wide, and 255 mm high.
Solution domain definition gravity negative direction 510 mm, gravity direction 255 mm, horizontal x direction 320 mm, horizontal y direction 70 mm.
Power consumption Parameters of the main components of the power consumption by component position distribution of power consumption, set the component's has radiant heat dissipation characteristics, components of the power consumption of the following table, the position distribution is shown in the figure on the right.
Material Parameters The case material is aluminum alloy, the PCB board is FR-4, and the thermal conductivity materials are Gap-Pad VO Soft, LORD 309 potting thermal conductive adhesive, and Sil-Pad 900S. The thermal conductivity of the materials is shown in the table below.
Meshed simulation model
Convergence curve (math.)
Temperature profile
Simulation results
Power Module Temperature Field Distribution
Temperature field distribution of heat generating devices inside the power module
Case 4 ZTE EDFA Module
ZTE Module thermal design specifications and requirements
1. ZTE EDFA module box volume: 120 * 100 * 17mm
2. System wind speed 2.5m/s, the wind direction is perpendicular to the direction of the connector; the top of the air extraction, the bottom of no
Air supply.
EDFA pump number: 2; power consumption: 6W8W
4. Ambient temperature: maximum temperature of 65 degrees
5. EDFA module on both sides with side panels
ZTE Module Module Dimension Schematic
1.EDFA module heat dissipation fins height of 4mm, wind speed of 2.5m / s, the module has a side plate on both sides
2.EDFA module thickness is 17mm, no cooling fins, wind speed is 2.5m/s, both sides have side panels.
3.The height of the heat dissipation fins of the EDFA module is 4mm, the wind speed is 2.5m/s, and there are no side panels on both sides of the module.
thermal simulation data
