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High-performance multi-stage internally-cooled liquid desiccant dehumidifier for high gas-liquid flow ratios

  • Fang, S
  • Xu, Z
  • Zhang, H
  • Rong, Y
  • Zhou, X
  • Zhi, X
  • Wang, K
  • Markides, CN
  • Qiu, L
Publication Date
Oct 10, 2021
Spiral - Imperial College Digital Repository


Liquid desiccant dehumidification provides a pathway to high-flow air pretreatment of air compressors for en-ergy savings. However, high air-to-solution flow ratios (i.e., over 4.0) may result in an unacceptable decrease in dehumidification effectiveness, and few studies have managed to overcome this challenge. This study aims to experimentally demonstrate that the multi-stage internally-cooled liquid desiccant dehumidifier (MILDD) is capable of improving the effectiveness at extremely high air-to-solution flow ratios over 10.0. A laboratory bench of the MILDD is designed and tested in various operational conditions. Based on the finite difference model, the experimental results of dehumidification effectiveness are analyzed in terms of the heat and mass transfer process such as irreversible loss and driving forces. The specific cooling capacity associated with the energy efficiency is further studied by considering different desiccant regeneration efficiency. In addition, the experimental latent effectiveness from present and previous work is compared and correlated. Results show that the measured latent effectiveness of the MILDD exceeds 0.42 and goes even up to 1.02 at high air-to-solution flow ratios, i.e., 8.6–20.1, while existing liquid desiccant dehumidifiers maintain a comparable effectiveness only at much lower flow ratios, i.e., below 4.0. The proposed model and correlation also have been validated with a considerable accuracy for predicting the performance of internally-cooled dehumidifiers. This work has experimentally demonstrated the ability of the multi-stage internally-cooled liquid desiccant dehumidifier to overcome the low effectiveness at high gas–liquid flow ratios, which advances the potential application of liquid desiccant dehu-midification in the air compression process.

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