# Design and Numerical Study of Induction-Heating Graphitization Furnace Based on Graphene Coils
## 1 Introduction
The heater of an IHGF has a temperature of more than 2000 \({}^{\circ}\)C in the later stages of heating, which greatly increases the heat dissipation. In order to improve the insulation of the furnace, it is necessary to increase the thickness of the insulation layer, sacrificing some of the electrical efficiency. This paper proposes a new idea to improve the energy efficiency by manufacturing coils using conductor materials with excellent high-temperature performances. The coil is placed inside the insulation layer next to the heater to achieve higher electrical efficiency; the coil does not need internal cooling water during operation but uses the heat generated by the coil losses for insulation, thereby improving the thermal efficiency. This idea combines the electrical and thermal efficiencies, resulting in the very high energy efficiency of the induction furnace, and it is also of great significance for energy saving in other high-temperature-heating fields, such as ceramics sintering [18; 19; 20]. The triple-phase point of carbon is 3727 \({}^{\circ}\)C [21], and graphitized carbon materials generally exhibit good high-temperature performances and excellent conductivities. Single-layer graphitic graphene, for instance, has a conductivity as high as 1 \(\times\) 10\({}^{8}\) S/m. In recent years, numerous studies have attempted to transfer the microscopic properties of graphene to the macroscopic scale. This class of materials includes graphene-based conductor materials (GCMs), such as graphene films [22; 23] and fibers [24; 25]. [PERSON] et al. [26] utilized a nitrogen-doping method to produce highly ordered crystalline graphene films with a conductivity of up to 2.0 \(\times\) 10\({}^{6}\) S/m and a thickness of 10 \(\upmu\)m. [PERSON] et al. [27] created an ultra-thick graphene film with a conductivity of 6.91 \(\times\) 10\({}^{5}\) S/m and a thickness of 200 \(\upmu\)m through the self-fusion property of graphene oxide sheets. Graphene fibers also exhibit excellent mechanical and electrical properties, and the conductivity of graphene fibers after high-temperature annealing can be up to 0.8-2.2 \(\times\) 10\({}^{6}\) S/m [28; 29; 30]. High-performance graphene fibers can be used as high-strength cables [25; 31; 32], flexible supercapacitors [33; 34], or other electronic devices. The conductivity of macroscopic graphenematerials is continuously making breakthroughs and showing potential applications in electrical engineering. The previous discussion highlighted the ability of graphene-based conductor materials to overcome the limitations imposed by copper. This paper describes a novel induction-heating system for IHGFs that utilizes macroscopic graphene materials as coils with impermeable internal cooling water that are placed inside an insulating layer to improve the energy efficiency. In this paper, the energy efficiencies, temperature fields, and electromagnetic fields of the new furnace and original furnace are investigated by numerical simulations. The energy efficiency potential of the new furnace is comparatively analyzed, and the impact of the coil parameters is discussed.