Design of an Optimized Graphite Electrode Cooling System by using Numerical Simulations
Abstract
The article deals with the design of optimization of graphite electrode cooling in a plasma reactor. By means of experimentally obtained data during the operation of the plasma reactor, it analyzes the current state of electrode cooling. Based on the measured temperatures at the inlet and outlet of the reactor and on the basis of the calculated flow rate of the cooling medium, it proposes a suitable solution for the optimization of the cooling system in the plasma reactor providing the necessary cooling power by analytical calculations with the use of software support. The proposed solution works on the principle of a water-air type heat exchanger. The verification of this proposal is carried out by numerical simulations using the Ansys CFX software.
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Introduction
Sufficient cooling is necessary to ensure the long service life of the electrode in the plasma reactor and its proper functioning. The high temperatures reached during operation can cause a high rate of electrode erosion. Heat transfer at the cathode occurs by radiation, convection, conduction and the influence of electron interaction. The cathode is also heated during operation by the electric current that passes through it. As the cathode is one of the elements with the highest temperature in the plasma torch, practically everything that is in contact with it serves as a thermal cooler.
The original cooling system works on the principle of an open cooling circuit. Thus, fresh water is supplied to the cooler using a water service line from the building in which the reactor is located. After heating, the water is then drained into the sewer pipe. Such a cooling system is highly inefficient and results in extremely high consumption of water. For this reason, it is necessary to change the system to a cooling system with a closed water circuit.
Conclusion
The resulting design of the air-water exchanger provides a cooling capacity approximately 20% higher than the required 1 kW. Due to the relatively robust construction of this solution, it would therefore be possible to shorten the total length of the exchanger tubes, which would allow more compact dimensions of the device to be achieved. Minimizing the dimensions could also be achieved by using a heat exchanger equipped with different ribbed surfaces.