Study on the heat and mass transfer characteristics of wet air and solution on the surface of corrugated packings at lower ambient pressure

This article undertakes both theoretical and experimental investigation on the heat and mass transfer properties of wet air and solution (configured sodium hydroxide solution with the concentration of 2%) on the surface of corrugated packings under reduced ambient pressure conditions. Theoretical analysis reveals that a decreased atmospheric pressure environment is conducive to amplifying mass transfer potential difference. However, it concurrently mitigates the maximum possible mass of water vapor per unit volume of air. Subsequently, experiments were carried out under the following conditions: vacuum degree-0 ~ 40 kPa, inlet air velocity-0.8 ~ 1.6 m/s, inlet air temperature-12.0 ~ 22.0 °C, and inlet air relative humidity-50.0 ~ 95.0%. The experimental outcomes indicate that heat transfer coefficient is predominantly influenced by inlet air velocity and vacuum degree. An enhancement of inlet air velocity or a reduction of vacuum degree leads to a corresponding increase of heat transfer coefficient. Under consistent conditions for other parameters, as vacuum degree ascends, moisture absorption rate and efficiency exhibit a steady growth, albeit with a diminishing rate of increment. Under constant inlet air velocity and relative humidity conditions, mass transfer coefficient initially experiences an upsurge as vacuum degree rises, but eventually undergoes a decline. At a fixed inlet air temperature, mass transfer coefficient behaves differently depending on air temperature. It demonstrates a gradual decrease under cooler air temperatures as vacuum degree rises, whereas under warmer air temperatures, it initially increases and then decreases. The analysis reveals that elevating vacuum degree indeed augments mass transfer capability between wet air and solution. However, there exists an upper limit to this enhancement, dictated by the maximum amount of water vapor that wet air can bear upon reaching saturation.