Effects of gas-liquid flow and dehumidification performance of a liquid desiccant dehumidifier: A numerical approach for vertical smooth & rough, and inclined rough plates

Abstract

This study investigates the dehumidification performance and the gas-liquid flow of a falling film liquid desiccant dehumidifier with different plate configurations: vertical smooth, vertical rough, and inclined rough. Utilizing ANSYS Workbench 2020 R1, the Re-Normalization Group (RNG) k-ε turbulence model has been utilized to simulate the gas-liquid flow, and the volume of fluid model is employed to track the interface patterns between the gas and liquid phases. This model takes into account the effects of the two-dimensional turbulent flow which is performed for various plate configurations under situations of unstable gas-liquid flow. The 30% LiCl solution is used as an absorbent and hence, the performance has been evaluated using a constant mass transfer rate of 50 mol/s. Furthermore, the LiCl solution’s mass concentration is taken into account as 30%, 33%, 36%, 40%, and 44%, respectively, for the justification of the influence of various concentrations of LiCl solution. The study analyzes the fields of mass fractions and the mechanisms that lead to the enhancement of dehumidification. The research examines the influence of inlet desiccant concentration and air velocity on mass transfer properties, revealing that an inclined ribbed plate significantly enhances dehumidification up to 10.8% compared to the smooth plate particularly at 1.5 m/s inlet air velocity by generating liquid film waves and increasing contact time between the liquid desiccant and moist of air. Lower inlet air velocities and higher inlet desiccant concentrations resulted in a decreased outlet mass percentage of water vapor. The optimal LiCl concentrations for water vapor absorption are 30-40%, with efficiency stable above 36%, though benefits may plateau beyond a certain level. The study concludes that the inclined rough plate enhances mass transfer performance at various inlet air velocities and desiccant concentrations by increasing the contact time between the liquid desiccant and moist air, increasing the rate of water vapor absorption. These findings provide valuable insights for researchers and engineers aiming to optimize liquid desiccant dehumidification systems for various applications, especially in the hybrid liquid desiccant-vapor compression systems.

Keywords

• Dehumidifier Performance
• Heat and Mass Transfer
• Liquid Desiccant
• Moist Air
• Vertical and Inclined Plates

References

1. [1] Luo Y, Yang H, Lu L. Liquid desiccant dehumidifier: Development of a new performance predication model based on CFD. Int J Heat Mass Transf 2014;69:408–416. [CrossRef]
2. [2] Lu H, Lu L. CFD simulation of liquid desiccant dehumidifier performance with smooth and rough plates. Int J Refrig 2021;124:1–12. [CrossRef]
3. [3] Wen T, Lu L, Dong C. Enhancing the dehumidification performance of LiCl solution with surfactant PVP-K30. Energy Build 2018;171:183–195. [CrossRef]
4. [4] Liu XH, Jiang Y. Handling zone dividing method in packed bed liquid desiccant dehumidification/regeneration process. Energy Conver Manage 2009;50:3024–3034. [CrossRef]
5. [5] Zhang LZ. Energy performance of independent air dehumidification systems with energy recovery measures. Energy 2006;31:1228–1242. [CrossRef]
6. [6] Zhang F, Zhang Z, Geng J. Study on shrinkage characteristics of heated falling liquid films. AIChE J 2005;51:2899–2907. [CrossRef]
7. [7] Zhang L, Hihara E, Matsuoka F, Dang C. Experimental analysis of mass transfer in adiabatic structured packing dehumidifier/regenerator with liquid desiccant. Int J Heat Mass Transf 2010;53:2856–2863. [CrossRef]
8. [8] Das RS, Jain S. Experimental investigations on a solar assisted liquid desiccant cooling system with indirect contact dehumidifier. Sol Energy 2017;153:289–300. [CrossRef]

9. [9] Zhang L, Liu X, Jiang J, Jiang Y. Exergy calculation and analysis of a dehumidification system using liquid desiccant. Energy Build 2014;69:318–328. [CrossRef]
10. [10] Chen Y, Yin Y, Zhang X. Performance analysis of a hybrid air-conditioning system dehumidified by liquid desiccant with low temperature and low concentration. Energy Build 2014;77:91–102. [CrossRef]
11. [11] Stevens DI, Braun JE, Klein SA. An effectiveness model of liquid-desiccant system heat/mass exchangers. Sol Energy 1989;42:449–455. [CrossRef]
12. [12] Liu GB, Yu KT, Yuan XG, Liu CJ, Guo QC. Simulations of chemical absorption in pilot-scale and industrial-scale packed columns by computational mass transfer. Chem Engineer Sci 2006;61:6511–6529. [CrossRef]
13. [13] Park MS, Howell JR, Vliet GC, Peterson J. Numerical and experimental results for coupled heat and mass transfer between a desiccant film and air in cross-flow. Int J Heat Mass Transf 1994;37:395–402. [CrossRef]
14. [14] Ren CQ. Corrections to the simple effectiveness-NTU method for counterflow cooling towers and packed bed liquid desiccant-air contact systems. Int J Heat Mass Transf 2008;51:237–245. [CrossRef]
15. [15] Luo Y, Shao S, Qin F, Tian C, Yang H. Investigation on feasibility of ionic liquids used in solar liquid desiccant air conditioning system. Sol Energy 2012;86:2718–2724. [CrossRef]
16. [16] Liu XH, Zhang Y, Qu KY, Jiang Y. Experimental study on mass transfer performances of cross flow dehumidifier using liquid desiccant. Energy Conver Manage 2006;47:2682–2692. [CrossRef]
17. [17] Tao W, Yimo L, Lin L. A novel 3D simulation model for investigating liquid desiccant dehumidification performance based on CFD technology. Appl Energy 2019;240:486–498. [CrossRef]
18. [18] Jayanti S, Hewitt GF. Hydrodynamics and heat transfer in wavy annular gas-liquid flow: A computational fluid dynamics study. Int J Heat Mass Transf 1997;40:2445–2460. [CrossRef]
19. [19] Del Carlo L, Olujić Z, Paglianti A. Comprehensive mass transfer model for distillation columns equipped with structured packings. Ind Engineer Chem Res 2006;45:7967–7976. [CrossRef]
20. [20] Banerjee R, Bai X, Pugh D, Isaac KM, Klein D, Edson J, et al. CFD simulations of critical components in fuel filling systems. SAE Tech Pap 2002-01-0573, 2002. p. 724. [CrossRef]
21. [21] Haroun Y, Raynal L, Legendre D. Mass transfer and liquid hold-up determination in structured packing by CFD. Chem Engineer Sci 2012;75:342–348. [CrossRef]
22. [22] Turgut OE, Çoban MT. Experimental and numerical investigation on the performance of an internally cooled dehumidifier. Heat Mass Transf 2016;52:2707–2722. [CrossRef]
23. [23] Wen T, Luo Y, He W, Gang W, Sheng L. Development of a novel quasi-3D model to investigate the performance of a falling film dehumidifier with CFD technology. Int J Heat Mass Transf 2019;132:431–442. [CrossRef]
24. [24] Xu YY, Paschke S, Repke JU, Yuan JQ, Wozny G. Computational approach to characterize the mass transfer between the counter-current gas-liquid flow. Chem Engineer Technol 2009;32:1227–1235. [CrossRef]
25. [25] Wen T, Lu L. Numerical and experimental study on internally cooled liquid desiccant dehumidification concerning film shrinkage shape and vapor condensation. Int J Therm Sci 2019;136:316–327. [CrossRef]
26. [26] Luo Y, Shao S, Xu H, Tian C, Yang H. Experimental and theoretical research of a fin-tube type internally-cooled liquid desiccant dehumidifier. Appl Energy 2014;133:127–134. [CrossRef]
27. [27] Qi R, Lu L. Energy consumption and optimization of internally cooled/heated liquid desiccant air-conditioning system: A case study in Hong Kong. Energy 2014;73:801–808. [CrossRef]
28. [28] Qi R, Lu L, Yang H, Qin F. Investigation on wetted area and film thickness for falling film liquid desiccant regeneration system. Appl Energy 2013;112:93–101. [CrossRef]
29. [29] Qi R, Lu L, Jiang Y. Investigation on the liquid contact angle and its influence for liquid desiccant dehumidification system. Int J Heat Mass Transf 2015;88:210–217. [CrossRef]
30. [30] Bouzenada S, McNevin C, Harrison S, Kaabi AN. An experimental study on the dehumidification performance of a low-flow falling-film liquid desiccant air-conditioner. Proc Comp Sci 2015;52:796–803. [CrossRef]
31. [31] Dong C, Lu L, Wen T. Experimental study on dehumidification performance enhancement by TiO2 superhydrophilic coating for liquid desiccant plate dehumidifiers. Build Environ 2017;124:219–231. [CrossRef]
32. [32] Lu H, Lu L, Luo Y, Qi R. Investigation on the dynamic characteristics of the counter-current flow for liquid desiccant dehumidification. Energy 2016;101:229–238. [CrossRef]
33. [33] Das A, Das RS, Das K. Performance analysis of aqueous LiCl and CaCl2 based falling film dehumidifier with surface modification. Appl Therm Engineer 2022;200:117704. [CrossRef]
34. [34] Das A, Das RS, Das K. Performance enhancement of a liquid desiccant absorber with triangular corrugated structured packing. J Build Engineer 2022;45:103677. [CrossRef]
35. [35] Lyu Y, Yin Y, Wang J. Effect of air parameters on LiCl-H2O film flow behavior in liquid desiccant systems. Buildings 2024;14:1474. [CrossRef]
36. [36] Das A, Das RS, Das K. Numerical analysis of liquid desiccant dehumidification system with novel trapezoidal baffled surface. Int J Refrig 2023;145:457–466. [CrossRef]
37. [37] Du B, Zhang G, Xie J, Liu H, Liu J. Experimental analysis of an innovative internally cooled dehumidifier. J Build Engineer 2023;80:108057. [CrossRef]
38. [38] Du B, Zhang G, Xie J, Liu H, Liu J. Study on the influence characteristics of thermal effect of internally cooled dehumidifier. Appl Therm Engineer 2024;236:121850. [CrossRef]
39. [39] Gao Y, Lu L. Parametric analysis and multi-objective optimization of a membrane distillation liquid desiccant regenerator with heat/moisture recovery and potable water production. Energy 2024;297:131319. [CrossRef]
40. [40] Khan R, Neyer D, Kurzina I, Kumar R. Heat and mass transfer characteristics of vertical falling film cylindrical plastic surfaces under partial wetting conditions for liquid desiccant regeneration. Appl Therm Engineer 2024;242:122462. [CrossRef]
41. [41] Peng D, Li Y, Cheng N. Study on the performance of tube evaporative cooling dehumidifier based on CFD. Appl Therm Engineer 2024;241:122419. [CrossRef]
42. [42] Rokhman F, et al. Performance enhancement of falling film dehumidifier by variation number and width ratio rectangular cylinder based on CFD simulation. Int J Heat Mass Transf 2024;221:125002. [CrossRef]
43. [43] Zhao CY, Zhang P, Guan Q, Qi D, Zhang Y, Jiang JM. Numerical study of falling film dehumidification performance on corrugated plates. Int J Heat Mass Transf 2024;219:124843. [CrossRef]
44. [44] Zhou D, Zhang Y, Zhang Y, Wu Y, Zhang G. Numerical study on the interface characteristics of gas-liquid falling film flow considering the interface forces. Phys Fluids 2024;36:0203373. [CrossRef]
45. [45] Mondal D, Alam A, Islam MA. Experimental observation of a small capacity vapor absorption cooling system 2014;5:456–467.
46. [46] Mondal D, Ikram MO, Rabbi MF, Moral MNA. Experimental investigation and comparison of bend tube parallel & counter flow and cross flow water to air heat exchanger. Int J Sci Engineer Res 2014;5:686–695.
47. [47] Mondal D, Islam MA. Experimental investigation on an intermittent ammonia absorption refrigeration. Mech Engineer Res J 2018;11:59–65.
48. [48] Mondal D, Hori Y, Kariya K, Miyara A, Jahangir Alam M. Measurement of viscosity of a binary mixture of R1123 + R32 refrigerant by tandem capillary tube method. Int J Thermophys 2020;41:1–20. [CrossRef]
49. [49] Mondal D, Kariya K, Tuhin AR, Amakusa N, Miyara A. Viscosity measurement for trans-1,1,1,4,4,4-hexafluoro-2-butene(R1336mzz(E)) in liquid and vapor phases. Int J Refrig 2022;133:267–275. [CrossRef]
50. [50] Mondal D, Kariya K, Tuhin AR, Miyoshi K, Miyara A. Thermal conductivity measurement and correlation at saturation condition of HFO refrigerant trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)). Int J Refrig 2021;129:109–117. [CrossRef]
51. [51] Mondal D, Tuhin AR, Kariya K, Miyara A. Measurement of kinematic viscosity and thermal conductivity of 3,3,4,4,5,5-HFCPE in liquid and vapor phases. Int J Refrig 2022;140:150–165. [CrossRef]
52. [52] Islam L, Mondal D, Islam A, Das P. Effects of heat transfer characteristics of R32 and R1234yf with Al2O3 nanoparticle through U-bend tube evaporator. J Engineer 2024;24:9991809. [CrossRef]
53. [53] Das P, Mondal D, Islam A, Afroj M. Thermodynamic performance evaluation of a solar powered Organic Rankine cycle (ORC) and dual cascading vapor compression cycle ( DCVCC ): Power generation and cooling effect. Energy Conver Manage 2024;23:100662. [CrossRef]
54. [54] Kumar K, Singh A, Chaurasiya PK, Kishore Pathak K, Pandey V. Progressive development in hybrid liquid desiccant-vapour compression cooling system: A review. Sustain Energy Technol Assess 2023;55:102960. [CrossRef]
55. [55] Zhao CY, Liang LW, Qi D, Ji WT, Tao WQ. The effect of gas streams on the hydrodynamics, heat and mass transfer in falling film evaporation, absorption, cooling and dehumidification: A comprehensive review. Build Environ 2022;219:109183. [CrossRef]
56. [56] Fahad FG, et al. Advancements in liquid desiccant technologies: A comprehensive review of materials, systems, and applications. Sustainability 2023;15:14021. [CrossRef]
57. [57] Koronaki IP, Christodoulaki RI, Papaefthimiou VD, Rogdakis ED. Thermodynamic analysis of a counter flow adiabatic dehumidifier with different liquid desiccant materials. Appl Therm Engineer 2013;50:361–373. [CrossRef]
58. [58] Park JY, Dong HW, Cho HJ, Jeong JW. Energy benefit of a cascade liquid desiccant dehumidification in a desiccant and evaporative cooling-assisted building air-conditioning system. Appl Therm Engineer 2019;147:291–301. [CrossRef]
59. [59] Mohammad AT, Bin Mat S, Sulaiman MY, Sopian K, Al-Abidi AA. Survey of liquid desiccant dehumidification system based on integrated vapor compression technology for building applications. Energy Build 2013;62:1–14. [CrossRef]
60. [60] Rafique MM, Gandhidasan P, Bahaidarah HMS. Liquid desiccant materials and dehumidifiers – A review. Renew Sustain Energy Rev 2016;56:179–195. [CrossRef]
61. [61] Jani DB, Rathod DP, Kureshi F. A review on recent development in liquid desiccant dehumidification assisted cooling systems. Int J Adv Res Sci Comm Technol 2022;2:683–690. [CrossRef]
62. [62] Misha S, Mat S, Ruslan MH, Sopian K. Review of solid/liquid desiccant in the drying applications and its regeneration methods. Renew Sustain Energy Rev 2012;16:4686–4707. [CrossRef]
63. [63] Banerjee R, Isaac KM. Evaluation of turbulence closure scheme for stratified two phase flow. ASME 2003 International Mechanical Engineering Congress and Exposition, Washington DC, November 15–21, 2003. pp. 689–705. [CrossRef]
64. [64] Lemmon EW, Bell H, Huber IL, McLinden MO. NIST Standard Reference Database 23: Reference Fluid Thermodynamic Properties-REFPROP (DLL Version 10.0a); 2018.