Beside the exhaust duct of a fusible metal melting furnace, or at the steam tail end of a drying oven, heat is often continuously lost in the form of medium-to-low temperature. Heat pipe heat exchangers, plate heat exchangers, and shell-and-tube heat exchangers can all undertake recovery tasks, but their applicable boundaries differ significantly. The plate structure is compact and has a high heat transfer coefficient, but it has strict requirements for medium cleanliness; fluids with particles or scaling tendencies easily clog the channels. The shell-and-tube type has a wide pressure and temperature resistance range, but its heat transfer area per unit volume is limited, and it tends to be bulky under low temperature difference conditions. The heat pipe heat exchanger transfers heat through the phase change of the working fluid, with the hot and cold sides completely isolated; the failure of a single heat pipe does not affect overall operation, and it shows good adaptability in waste heat recovery from dust-laden flue gas or corrosive gases.
The first is medium corrosiveness, which determines the selection of pipe material and weld seam material. Sulfur-containing flue gas or acidic vapor environments should use corrosion-resistant alloys or undergo surface treatment. The second is the operating temperature and its fluctuation range, which affects the verification of the heat pipe working fluid and pipe wall temperature; the heat pipe operating temperature should be lower than the critical temperature of its working fluid and higher than the freezing point, to avoid a decline in heat transfer performance. The third is the allowable pressure drop and installation space, which relate to fin spacing and structural arrangement. When space is limited, a smaller fin spacing can be used, but the risk of ash deposition must be evaluated simultaneously. In addition, for equipment such as fusible metal melting furnaces, air heating furnaces, drying ovens, and hot-pressing molds, this heat exchanger can recover waste heat or provide a stable heat source. During design, the matching relationship between the heat pipe start-stop temperature and load fluctuations must be calculated.
The RQC-38 heat pipe heat exchanger can use working fluid combinations such as carbon steel-water, steel-naphthalene, or aluminum-ammonia, selected according to the temperature range. The equipment supports vertical or horizontal installation, and a counterflow arrangement of hot and cold fluids helps improve temperature difference utilization. In the cooling circuit of a hot-pressing mold, the heat pipe heat exchanger can transfer mold waste heat to preheated air, reducing external heat source consumption; in the moisture exhaust duct of a drying oven, it can preheat fresh air. During operation, the isothermal performance of the heat pipes must be checked regularly. If abnormal wall temperature distribution is found, working fluid leakage or solidification blockage should be investigated. Compared with similar solutions, this structure has relatively controllable maintenance workload in dust-laden, corrosive, and small-to-medium temperature difference scenarios, but the initial investment is close to that of plate solutions, so a trade-off must be made based on specific working conditions.
