Numerical and Analytical Modelling of Induction Heating in Silica Gel/Methanol Adsorption Cold Production System 

3. Institut für elektrische Energie- und Steuerungstechnik, Technische Universität Ilmenau 98684 Ilmenau, Germany 

Abstract: Using the thermal heating such as industry waste heat or solar energy has some severe drawbacks in the development of adsorption cooling technology. A major disadvantage is the adsorption reactor requires a long time of about one hour to desorb the required amount of the adsorbate. Moreover the setup has a complex design, composed of tubes of hot water and so many fins. In order to overcome the problems found with conventional methods (thermal heating), a new design of the adsorption reactor with a new heat source has been studied and simulated in this work. Our work deals with a mathematical modeling and numerical simulation of an induction heating system for an adsorption reactor filled by Silica Gel (SG) as adsorption material and methanol (CH3OH) as adsorbate. The purpose of this study is the use of electromagnetic induction technology as a new heat source of the adsorption cold production system. Here, inductive heating shall be used to desorb the adsorbate CH3OH loaded within the SG-particles, i.e., supplying the desorption process with process energy, that the desorption process is the main process of the adsorption cooling systems. Within this context the work will focus on analyzing the induction heating system (calculation of the inductor and work-load) for the new application (desorption process). The important step was to explore the possibility of heating SG-granular using this technology. Because of the dielectric properties of SG, incorporation of the materials (Graphite balls), having a good electrical conductivity, into the adsorption medium, is used in order to improve the heat transfer process and to save the input energy. The solution of the induction heating problem by numerical modelling and simulation processes was implemented by the software ANSYS ELECTRONICS ®17.2. This option is based on a special 2D and 3D FEM algorithm for calculation of the coupled electromagnetic and thermal fields. Additionally, ANSYS FLUENT was used to study the temperature distribution at every point throughout the adsorption reactor during the desorption process. In this Study, to desorb 1 kgmeth as adsorbate, we have numerically simulated the desorption process by using 7.9 kg of silica gel and 2 kg of methanol in the adsorption reactor. As a main result to obtain the needed desorption temperature of 100°C through the reactor, we find, the required electric power, which is induced inside the reactor to desorb 1 kg methanol from the SG-particles, is estimated to be 3kW yielding an electrical efficiency of 41%, which is produced by applying coil current of 690 A passing the induction coil at 25 kHz. Incorporation of Graphite balls into the adsorption reactor allows achieving homogeneity of the temperature distribution throughout the reactor and allows obtaining the exact needed temperature distribution in the material if required.