Abstract:

Based on different experimental conditions， the ground experimental studies on the frosting and defrosting of the microtubule precooler have been carried out. The specific experimental conditions are as follows： the temperature and humidity value of the mainstream are 50 ℃ and 1.8 g/kg， respectively， and the flow velocity of the mainstream is 10， 20， and 30 m/s， respectively. For the defrosting experiments at different main flow velocities， the mass ratio of the anhydrous methanol-to-water spraying into the main flow is 1.0. The results of the frosting and defrosting ground experiments show that the main flow velocity has significant effects on the frosting and defrosting characteristics of the microtubule precooler. In addition to increasing the main flow velocity， it can significantly reduce the condensation and accumulation of the frost layer on the outside wall surface of the microtubule bundle of the precooler. In the defrosting experiments， due to the spraying of anhydrous methanol with a mass ratio of 1.0 into the main flow， the wall surface temperature of the microtubule bundle of the precooler can be significantly increased， and the defrosting effect can also be clearly improved. As a result， the pressure loss coefficient of the freestream deceases distinctly and the heat transfer rate of the precooler appreciably increases. In addition， with the increase of the main flow velocity， the pressure loss coefficient of the freestream increases sharply， while the covering area of the frost layer on the outside wall surface of the microtubule bank of the precooler clearly decreases， which indicates that increasing the main flow velocity is beneficial to the suppression of the condensation and accumulation of frost layers on the outside wall surface of the precooler microtubule bank.

Key words: microtubule precooler, defrosting performance, pressure loss coefficient, wall surface temperature, heat transfer rate