International Scientific Journal


The heat losses that occur from the surface of the rotary kilns during calcination process are a major source of waste heat in cement production industry. In order to recover this heat, a multi-shell heat exchanger that forms an annular duct over the high temperature zone of the kiln is used. The phase-change material (PCM) paraffin wax with a melting point of 68°C is filled in between the gap of the two concentric annular steel shells which are thermally insulated from the outside. In order to draw a comparison and to establish that phase change material improves the waste heat recovery, the heat exchanger model made up of mild steel, which extracts waste heat from a kiln, is experimentally investigated with and without the tertiary shell that contains the phase-change material. The outer surface of the heat exchanger is insulated by glass wool, and to facilitate the passage of air between the shells for heat transfer, a variable speed centrifugal fan (for variable flow rate) is installed. The results show that the waste heat recovery rate is increased by 3% to 8% (depending on different air flow rate) with the use of phase-change material. This implies that phase-change materials such as paraffin wax can be used in heat exchangers to obtain an improved waste heat recovery rate.
PAPER REVISED: 2017-12-11
PAPER ACCEPTED: 2017-12-19
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