A Study on the Design of an Air-to-Air Plate Heat Exchanger for 300℃ High Temperature Heat Pumps

A high-temperature plate heat exchanger was developed for use in a high-temperature heat pump system operating at 300 °C, utilizing air as the working fluid. Most existing heat transfer correlations for plate heat exchangers are based on water-to-water experimental data, which can lead to performance prediction errors. This underscores the necessity for correlations specifically tailored for air-to-air heat exchangers. To address this, a prototype heat exchanger was constructed based on conventional water-to-water correlations, and performance tests were conducted by varying the inlet pressure between 131 and 517 kPa and the inlet mass flow rate from 0.187 to 0.436 kg/s. As the airflow rate increased, the heat transfer rate rose from 45.7 kW to 103.7 kW, while the heat exchanger effectiveness decreased from 89.1% to 85.4%. From these experimental results, a heat transfer correlation suitable for air-to-air plate heat exchangers was developed. This new correlation significantly reduced the error in heat exchanger effectiveness from 8.0% to 0.45% compared to the conventional water-to-water correlation. When designing high-temperature and low-temperature heat exchangers with 90% effectiveness using this new correlation, the 300 °C high-temperature heat pump system is predicted to achieve a coefficient of performance (COP) of 1.63.