https://orcid.org/0009-0009-1572-8735
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ABSTRACT
Liquid desiccant dehumidification has garnered significant attention due to its numerous benefits. This study focuses on enhancing the efficiency of liquid desiccant dehumidification through the use of modified solutions, particularly by incorporating polyvinyl pyrrolidone (PVP) as an additive. PVP is a nonvolatile, odorless, and nontoxic surfactant that was selected to enhance the dehumidification performance of the liquid desiccant system. Computational fluid dynamics was employed to investigate the dehumidification performance of falling film liquid desiccant systems. The study aims to assess the impact of PVP, solution parameters, and moist air conditions (humidity concentration, temperature, and flow rate) on dehumidification effectiveness. The specific objectives of the numerical simulation include analyzing performance metrics such as dehumidification rate and effectiveness to evaluate the enhancement in the falling film liquid desiccant cooling system. The selection of lithium chloride (LiCl) as the base solution and PVP as an additive at 0.4 wt% is highlighted as a key aspect of the study. The findings indicate that PVP significantly improves dehumidification effectiveness by reducing the contact angle of liquid solution on the surface plate and increasing the surface wetting ratio, thereby enhancing moisture transfer capacity. Optimal dehumidification performance is achieved with the combination of LiCl and PVP at the specified concentration. The study reveals that increasing solution or air inlet temperature reduces the dehumidification rate, while raising solution or air inlet concentration, velocity, or air humidity strengthens the dehumidification process. Additionally, the efficacy of dehumidification increases with solution velocity but decreases with solution intake concentration or air velocity. Overall, the results demonstrate an average relative increase of 21.6% in dehumidification rate and 17.4% in dehumidification effectiveness, underscoring the effectiveness of PVP in enhancing vapor absorption capability and overall system efficiency in Liquid Desiccant Cooling systems (LDCs). This enhancement is attributed to the reduction in surface tension of the liquid desiccant, as evidenced by the decrease in contact angle from 58.6° to 28.9°.
Nomenclature
| F | = | Momentum source term (N m−3) |
| Gk | = | Generation of turbulence kinetic energy due to mean velocity gradients (kg m−1 s−3) |
| g | = | Gravity acceleration (m s−2) |
| H | = | Humidity (g kg−1) |
| Wg,b | = | Humidity ratio of bulk air (kg kg−1) |
| hm | = | Local mass transfer coefficient (kg m−2 s−1) |
| Gb | = | Generation of turbulence kinetic energy due to buoyancy (kg m−1 s−3) |
| Hlg | = | Latent heat of evaporation (J kg−1) |
| J | = | Mass flux (kg m−3 s−1) |
| t | = | Time (s) |
| k | = | Thermal conductivity (W m−1 K−1) |
| l | = | Liquid flow distance (m) |
| D | = | Diffusion coefficient (m2 s−1) |
| P | = | Pressure (Pa) |
| Pl,b | = | Partial vapor pressure of the bulk desiccant solution (Pa) |
| Pa | = | Atmospheric pressure(Pa) |
| K | = | Local overall mass transfer coefficient (kg m−2s−1) |
| Wg,e | = | Equilibrium air humidity ratio to the desiccant solution (kg kg−1) |
| Q | = | Liquid flow rate of the unit width (m3 m−1s−1) |
| E | = | Energy (J kg−1) |
| SE | = | Energy source term (W m−3) |
| Slg | = | Mass transfer source at the phase interface (kg m−3) |
| tc | = | Contact times (s) |
| T | = | Temperature (K) |
| usurf | = | Surface velocity of the liquid film |
| Greek characters | = | |
| μ | = | Dynamic viscosity (kg m − 1 s − 1) |
| ρ | = | Density (kg m − 3) |
| ψ | = | Concentration difference ratio |
| α | = | Volume fraction of phases |
| Subscripts | = | |
| a | = | Air eff effective |
| l | = | Liquid phase s solution |
| g | = | Gas phase |
Acknowledgements
The authors, Shrikant Kol and Dr. Manoj Arya, express their gratitude to the Director and Maulana Azad National Institute of Technology Bhopal, India for their support and assistance in the completion of this work.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Funding
Notes on contributors
Shrikant Kol
Shrikant Kol is a research scholar in the Department of Mechanical Engineering at Maulana Azad National Institute of Technology (MANIT) in Madhya Pradesh, India. He holds a master’s degree in Heat and Power Engineering and is currently working towards his Ph.D. at MANIT Bhopal. His doctoral research involves the optimization of liquid desiccant systems and the application of computational fluid dynamics (CFD) for improved performance analysis, utilizing advanced tools like ANSYS and Python.
Manoj Arya
Dr. Manoj Arya is an Associate Professor in the Department of Mechanical Engineering at Maulana Azad National Institute of Technology (MANIT) in Madhya Pradesh, India. He holds a Doctor of Engineering degree in Thermal Engineering from the same institution.
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