关键词: 低温加热, 负压蒸汽, 精准控温, 数值模拟, 液气射流泵

Abstract: Aiming at the current problems of low heating efficiency, difficult to maintain accurate temperature, low automation and high equipment cost in agriculture, chemical and food processing industries for low temperature heating process below 100 ℃, a negative pressure steam heating system based on liquidair jet is designed and developed by integrating jet pump evacuation technology, PLC control technology and temperature control and pressure regulation technology. The system consists of intelligent control system, liquidair jet vacuum circulation system, temperature reduction and pressure regulation system and circulating water regulation system, which provides negative pressure environment of steam through liquidair jet pump evacuation, combined with temperature and pressure reduction device and PLC intelligent control system to control the negative pressure steam and realize the precise automatic heating of materials by negative pressure steam. The working principle of the negativepressure steam heating system is elaborated, the design structure and relevant parameters of the key component jet pump are determined, and the relevant verification of the fluid numerical simulation is carried out, and the simulation results are within 10% error from the actual one, which shows that the jet pump design is reasonable and reliable. The heating performance of the system is tested, and the results show that the negative pressure steam heating system based on liquidair jet can precisely control the steam temperature for heating, while the heating temperature curve is gentle, with the vacuum level fluctuating up and down by 0.003 MPa in the rapid heating stage and 0.002 MPa in the equilibrium stage, and the heating temperature fluctuation is also within ±1 ℃, which can better adapt to the heating temperature of different materials. The heating efficiency is about 2 times better than that of water bath heating. This study can solve the problems of uneven heating, poor control accuracy, slow heating process and low production capacity of traditional water bath heating, and provide new ideas and references for heating methods, systems and devices for deep processing of agricultural and chemical products.

Key words: low temperature heating, negative pressure steam, accurate temperature control, numerical simulation, liquidair jet pump