An investigation of the heat transfer in an electrically heated tubular wire strand furnace

Massey, JN

Abstract

This thesis investigates the heat transfer involved in the heating of wire in an Electrically-Heated Tubular Strand Annealing Furnace. The fundamental concepts of the furnace are explained, followed by the rationale behind the basic design of the furnace.
This is followed by an experimental investigation of a furnace which is actually used in production at a local wire factory. The overall efficiency of this furnace in heating wire is found to be 69%, as compared with the manufacturer's estimate of 78%. As a consequence of this work, a prototype furnace rig has been designed and set up in the Thermodynamics laboratory, where tests have been carried out on the heating of 2,3 and 4 mm diameter, Austenitic stainless steel, over a temperature range of 20-1000°C. The results from these experiments are then presented, and the prototype furnace is found to be able to anneal Stainless Steel wire at a maximum rate of 5.4 Kg per hour, with an overall efficiency of 60%
The results of the experiments have been analyzed and are subsequently discussed, and the wire temperature profiles corrected for thermocouple installation error. A model is developed to predict the heating of wire due to radiant heat transfer in the prototype furnace. This model is used to predict the temperature profiles of 2,3 and 4 mm diameter, Austenitic Stainless Steel wire being heated in the furnace, with the three heater zones at a set temperature of 1000°C. The results from these simulations suggest that over all the tests presented, the heat transferred to the wire by radiation provides approximately 65% of the energy which is required to heat the wire at the experimentally determined rate.
A second prediction model is then developed which considers the heat transfer to the wire from the process tube by convection, in addition to radiation. The wire temperature profiles predicted using this model are determined to be within approximately 5% of the experimental results. A more complex model is discussed and has been developed, leading to the final model of a multi-tube furnace, and this is used to predict the wire temperature profiles for the multitube furnace on which the experimental work was carried out. These are found to be within approximately 10% of the experimental results. This model is then developed into a design tool, for use by the manufacturers to predict the performance of a given furnace design.

Citation

Massey, J. An investigation of the heat transfer in an electrically heated tubular wire strand furnace. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Sep 7, 2021
• Publicly Available Date: Sep 7, 2021
• Publisher URL: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261856
• Related Public URLs: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261856
• Additional Information: Funders : Meltech Furnaces Ltd.;The Science and Engineering Research Council
• Award Date: Apr 1, 1993