Abstract

Hot air generators are essential for food drying processes, operating in either indirect or direct modes. In this study, a high-power radiant porous burner in a novel dual hot air generator (HAG-D) was designed and experimentally investigated. Temperatures and emissions of the combustion process are reported for 9, 13, and 18 kW, and 20% and 40% of excess air. Indirect and direct modes were tested across airflow rates of 300-1100 m3/h to assess thermal efficiency. For indirect mode operation, 88% thermal efficiency is the highest value for 9 kW, 20% excess air, with an airflow of 890 m3/h observing air temperature difference (outlet minus inlet) of approximately 30 degrees C. Furthermore, CO and NOx emissions were found in the range of 0-30 ppm and 20-45 ppm, respectively. For direct mode operation, results showed that for 18 kW with 20% and 40% excess air, the maximum thermal efficiency was 82% with an airflow of 670-1040 m3/h and air temperature difference in the range of 50-80 degrees C. Results confirm that the radiant heat transfer mechanism allows for higher efficiencies and less pollution in a wide range of powers in the HAG-D unit. The direct mode is recommended for food drying processes due to low exposure to flue gases, and the indirect mode is for other industrial applications due to its high efficiency. Future studies are suggested to assess renewable fuels, such as liquefied petroleum gas or natural gas and hydrogen mixtures, toward energy transition.Practical applicationsThe potential applications or practical benefits of the develop of this novel dual hot air generator is in the food industry, particularly in drying process of fruits and vegetables. Also, air conditioning, and space heating (household use) processes stand out among their several applications to generate hot air, such as paint, and wood.