Thermodynamic analysis of induction gas heaters

The energy demand among the worldwide is increasing every day parallel to the developing technology. Within this scope, preserving energy and energy efficiency has become a key point for a sustainable society. Reducing the energy costs by reducing the usage of electricity has a large share among the state's economics. Electricity savings can be achieved by avoiding unnecessary use and leakage, as well as by developing devices that can perform the same work with lower energy. The air conditioning sector renews itself within the scope of the environmental policies which are put into practice by the state's due to the factors that threatening the lives of human beings and living things, especially global warming. Therefore, it is important to develop the air conditioning systems in accordance with environmental policies. In this context, technology development stages are in progress in order to ensure that heating systems based on fossil fuels for space conditioning are replaced by systems that operate with electrical energy and on the other hand to ensure the effective heating of systems working with electrical energy. By means of this aspect, induction heating systems are an emerging technology as an alternative to other technologies. In the case of induction heating technology, an electrically conductive material placed in a coil that heats the fluid without combustion, thereby improving the quality of the earth environment by significantly eliminating carbon-based and other greenhouse gas emissions caused by air heating. In accordance with the findings and suggestions obtained from the prototypes previously developed, the performance of the K5 type induction gas heater is realized by simplification of these prototypes in the circular air channel has been examined under the transient and steady state regimes in terms of the disciplines of electricity, thermodynamics and fluid mechanics. By using induction air heaters instead of conventional resistance heaters, it is planned to prevent the dangers caused by electricity leakages, environmental pollution, corrosion, and the growth of bacteria and/or viruses in the heater, and to obtain a heating system with long service life. In the experiments, air was used as a working fluid and numerical simulations were carried out with Comsol Multiphysics®, which uses the finite element method to determine the thermal and flow characteristics that was in the air duct. The method and results obtained in the simulation were confirmed by experimental results and other validation methods given in the literature. On the other hand, the applicability of Nusselt correlations from the literature to the heater was discussed. Temperature values achieved on shell and coil, temperature values of the air in different points of the heater, heat transfer coefficient inside the shell (I. Region) and outside of the coil (II. Region), pressure loss in the duct, electrical coupling efficiency and thermal efficiency was determined as performance parameters of the heater. In order to analyse the performance parameters of the system under different conditions, parametric studies were performed using a validated simulation model. Within this scope, the change of the Reynolds number of the air at the inlet of the considered analysis zone, the different coil powers with the change of the Reynolds number, the change in the ratio of the inner diameter of the channel to the inner diameter of the shell, the change in the ratio of the shell length to the inner diameter of the shell, the effect of different gases and the flow rectifier placed in the shell and heater ends was investigated. In addition, in order to determine the electromagnetic performance of the system, simulations related to equivalent circuit analysis were performed by Multisim v.14. As a result of the experimental study, the thermal and electrical efficiency of the heater was calculated as 100% and 94.46%, respectively. It was determined that the exit temperature of the air from the duct is 30.5°C when the average temperature of the shell and coil is 159.6°C and 58.2°C.