Investigation on a full-scale heat pipe heat exchanger in the ceramics industry for waste heat recovery

The ceramics industry is the second largest energy consuming sector in Europe. The main energy used in the ceramics industry is heat generated through burners using natural gas. The main area can be identified in three stages, the drying stage and the firing stage, and the cooling stage. The firing stage represents about 75% of the total energy cost. The roller hearth kiln technology is considered to be the most cost-effective solution for ceramic tile manufacturing. The kiln is separated into two sections, the firing stage and the cooling stage. The cooling stage generates large amounts of waste heat as the exhaust of the kiln is composed of a challenging flue gas for heat recovery. The recovery of this heat in an efficient way with no cross contamination has been achieved with a heat pipe heat exchanger (HPHE) system, which was designed, manufactured and installed on a roller hearth kiln and is presented in this paper. The heat pipe heat exchanger located next to the cooling section exhaust stack managed to recover up to 100 kW at steady state without cross contamination or excess fouling. The return on investment of the system has been evaluated at 16 months with a saving of £30,000 per year. This paper will present a deep row by row theoretical analysis of the heat pipe heat exchanger. The Computational Fluids Dynamics will also be presented to investigate the fluid dynamics within the evaporator and condenser section. Both investigations have then been validated by the experimental investigation carried out on a full-scale industrial system. The design approach used in this paper will highlight the benefits of this type of technology and provide a guideline for the design of novel heat pipe heat exchangers.