One question frequently raised during the design and selection stage is: the flue gas temperature is only 180°C, but the heat pipe wall temperature is already close to the critical temperature of the working fluid—can a conventional heat pipe heat exchanger still be selected for such an operating condition? To answer this question, we must first return to the fundamental constraint of heat pipe operating temperature.
The operating temperature of a heat pipe must be below the critical temperature of the charged working fluid and above its freezing point; otherwise, the heat transfer capability will drop significantly or the heat pipe may fail to start. During selection of the HGR-48 heat pipe heat exchanger, the pipe wall temperature is calculated based on the actual temperature ranges on the flue gas side and air side, and the working fluid type and charge amount are determined accordingly. If process adjustments cause changes in the medium or temperature, the original selection records must be rechecked to confirm whether the temperature and corrosion resistance grades of the pipe material and the fin spacing are still applicable; old parameters must not be reused based on experience alone.
For the flue gas side with high dust content or prone to fouling, excessively small fin spacing will accelerate ash deposition, causing the heat transfer capability to decline noticeably after several months of operation. The HGR-48 can adopt a larger spacing arrangement on the flue gas side and correspondingly shorten the ash cleaning cycle to maintain long-term heat transfer performance. Designers should determine the spacing comprehensively based on dust concentration, fouling tendency, and ash cleaning method, and should not merely pursue a compact structure.
Different media have considerably different requirements for pipe shell materials. For acid-base tanks and nitrate tanks, the combination of pipe material and working fluid must be determined based on medium concentration, temperature, and compatibility test data, so as to avoid the generation of non-condensable gases during operation that would deteriorate heat transfer. Compatibility data should be obtained during selection, and small-sample verification should be arranged when necessary.
The HGR-48 heat pipe heat exchanger is applicable to a flue gas temperature range of approximately 120°C to 350°C. The design pressure is marked separately for the flue gas side and the air side. Single-pipe heat transfer is mainly by gravity return, and the installation inclination angle must be controlled according to the sample requirements. The equipment can be used for flue gas waste heat recovery in industrial furnaces and kilns, hot air preheating in drying systems, and heat exchange in process tanks such as acid-base tanks and nitrate tanks. Specific parameters are subject to the ordering technical agreement and accompanying documents.
