Experimental Investigation of Heat Recovery from Flue Gases Using Heat Pipe Heat Exchangers

Waste heat recovery from industrial flue gases presents a significant opportunity to improve overall thermal system efficiency and reduce carbon emissions. This study presents a comprehensive experimental investigation into the thermal performance of a copper-water Heat Pipe Heat Exchanger (HPHE) designed for medium-to-low temperature waste heat recovery. The HPHE contains a ۶ × ۶ staggered array of gravity-assisted wickless heat pipes (thermosyphons). The effects of key operating parameters — including flue gas inlet temperature (۱۲۰oC to ۲۲۰oC), inlet mass flow rate (۰.۰۵ to ۰.۲۵ kg/s), evaporator-to-condenser thermal capacity ratios, and liquid filling ratios (FR: ۱۵% to ۶۰%) — on the overall heat transfer rate, temperature effectiveness, and pressure drop were systematically characterized. The experimental results reveal that the optimum filling ratio for maximum heat transfer is approximately ۳۵% of the evaporator volume, balancing the dry-out and liquid entrainment limits. At this optimum FR, the HPHE demonstrated a maximum heat recovery rate of ۱۸.۴ kW and a thermal effectiveness of ۶۸.۵%. However, increasing the flue gas mass flow rate leads to an elevated pressure drop on the gas side, highlighting a crucial trade-off between heat transfer enhancement and fan power requirements. The experimental data and calculated Nusselt number correlations provide robust baseline parameters for scale-up designs of industrial flue gas recovery networks

کلیدواژه ها:

Waste Heat Recovery ، Heat Pipe Heat Exchanger ، Thermosyphon ، Thermal Effectiveness ، Flue Gas ، Filling Ratio