چكيده به لاتين
Abstract:
As the satellite is outside the Earth's atmosphere, experiencing sunrise and successive eclipses as it orbits the Earth; it is subject to extreme temperature gradients. Thermal Protection and control of the satellite subsystems in these conditions is very important. One of the new methods of thermal control that has been discussed in many industries today is the use of phase change materials for this purpose. Thermal energy storage is accomplished by phase change materials (PCMs). In these materials, energy storage is caused by phase change. The PCMs have the property of changing their state at a given temperature range, this means that they maintain their temperature for the duration of the state of change during the state change process. This property can be used for thermal control in many systems. Choosing the appropriate PCMs and improving its thermal properties for use in the satellite's thermal control subsystem is a challenge that will be dealt in this project. An important category of PCMs are paraffins. Paraffins have a good thermal capacity, their volume is not too large due to phase change, and the phenomenon of supercooling rarely occurs in them, they are not toxic, they have high reliability during repeated cycles, and Of course, they are availabe and reasonable cost. All of these factors make them suitable for space applications; however, paraffins are generally of low thermal conductivity. There are several solutions to solve the problem of thermal conductivity deficiency of paraffins. One of these ways is the addition of nano-superconducting materials such as graphene and carbon nanotubes (CNT) to paraffins; in this study, has investigated the paraffin-hybrid grapheme_CNT. The paraffin used in this research is n-octadecane (C18H38), a high-chain alkane with a melting point of about 28 to 30 degrees Celsius, commonly used for thermal management of batteries and electronic devices. The results showed that the addition of hybrid grapheme_CNT partially increases the thermal conductivity of paraffin, although it mostly reduced its thermal capacity slightly and appeared to slightly increase the melting point (phase change temperature), and generally reduced the mobility and movement of atoms. Graphene and CNT, due to their high thermal conductivity and by regulating the paraffin molecules and keeping them crystalline, increase the thermal conductivity of the paraffin-hybrid grapheme_CNT composite. Paraffin-hybrid grapheme_CNT composite show more thermal conductivity in graphene and CNT longitudinal direction than in the Perpendicular to the directions of the nano additive.
Keywords: Satellite, Thermal Control System, Phase Change materials, Melting Point, Paraffin, n-Octadecane, Supercooling, Thermal Energy Storage, Molecular Dynamics, Nano Additive, Graphene, Carbon Nanotube(CNT), Thermal Conductivity, Thermal Capacity.
