Abstract:

The humidification-dehumidification seawater desalination technology shows significant potential as a method for freshwater production. Nevertheless, challenges such as heat and mass imbalances between the humidification and dehumidification processes caused by uneven spraying result in a low freshwater production rate per volume. In this regard, this paper proposes a compact two-stage humidification-dehumidification (HDH) desalination system. The device contains two humidifiers and a dehumidifier, wherein the dehumidifier is stacked between the vertically placed humidifiers. Its freshwater yield performance was evaluated through an electric heating steady-state experiment, varying the feed seawater mass flow rate, feed seawater temperature, and preheating conditions. The results show that the water production of the device increases with the increase of feed seawater flow rate and temperature. Specifically, an increase in feed seawater mass flow rate from 0.45 t/h to 0.96 t/h resulted in a corresponding increase in freshwater yield from 18.7 kg/h to 27.1 kg/h. At a feed seawater temperature of 85℃, the device achieves a freshwater yield of 33.7 kg/h with a gained output ratio (GOR) of 0.9. In addition,preheating the device can potentially enhance the freshwater yield by up to 6.8%. The maximum per unit volume freshwater yield of the device is 33.7 kg/(m³·h), which is obviously higher than traditional two-stage HDH device.

Key words: humidification-dehumidification, desalination, heat transfer, mass transfer, freshwater yield per volume

摘要：

空气加湿除湿海水淡化是极具应用前景的淡水生产技术。然而，由于加湿、除湿腔内存在喷淋不均匀现象，且喷淋不均对加湿过程的影响更大，致使加湿除湿过程的热质传递系数不匹配，进而致使其单位体积产水量偏低。为此，提出一种两级叠置式加湿除湿海水淡化装置，其两个加湿腔共用一个除湿腔，从而缩小了装置体积，提高了单位体积产水量。研究了供料海水流量、温度及预热对其性能的影响。结果表明，装置产水量随供料海水流量、温度的升高而增加。供料海水流量由0.45 t/h增至0.96 t/h，产水量从18.7 kg/h增加到27.1 kg/h；供料海水温度为85℃，产水量达33.7 kg/h，对应热利用系数为0.9；预热装置，可将其产水量提高6.8%。此外，其单位体积产水量可达33.7 kg/（m³∙h），远高于传统两级空气加湿除湿海水淡化装置。

关键词: 加湿除湿, 海水淡化, 传热, 传质, 单位体积产水量