Problem statement: Currently, the heat pipe air-preheater has become importance equipment for energy recovery from industrial waste heat because of its low investment cost and high thermal conductivity. Approach: This purpose of the study was to design, construct and test the waste heat recovery by heat pipe air-preheater from the furnace in a hot brass forging process. The mathematical model was developed to predict heat transfer rate and applied to compute the heat pipe air-preheater in a hot brass forging process. The heat pipe air-preheater was designed, constructed and tested under medium temperature operating conditions with inlet hot gas ranging between 370-420°C using water as the working fluid with 50% filling by volume of evaporator length. Results: The experiment findings indicated that when the hot gas temperature increased, the heat transfer rate also increased. If the internal diameter increased, the heat transfer rate increased and when the tube arrangement changed from inline to staggered arrangement, the heat transfer rate increased. Conclusion/Recommendations: The heat pipe air-preheater can reduced the quantity of using gas in the furnace and achieve energy thrift effectively.

This research studied the heat transfer of the thermosyphon air-preheater. An empirical model was developed to predict heat transfer and applied to compute the thermosyphon air-preheater in a hot brass forging process. The thermosyphon air-preheater was designed, constructed and tested under medium temperature operating conditions with inlet hot gases, ranging between 390-440 °C in terms of using water as the working fluid with a 50 % fill by volume of the evaporator section. The experimental setup was comprised of a circular fin with 0.013 and 0.020 m internal diameter bare stainless steel tubes, with 0.015 m long evaporator and condenser sections. The thermosyphon air-preheater model had 6 rows, each composed of 4 columns. Experimental results found that the hot gas temperature was increased from 390 to 440 °C, the heat transfer rate increased. If the internal diameter changed from 0.013 to 0.020 m, the heat transfer rate slightly increased. The predicted results agreed well with the experimental data. This thermosyphon air-preheater has been designed, manufactured and tested for heat recovery in industry using medium temperatures ranging between 300-500 °C to recover flue gas energy from the furnace in a hot brass forging process.