https://orcid.org/0000-0002-3024-196X
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ABSTRACT
The continuously growing energy demands for space air conditioning and depletion of conventional energy resources at a fast rate have propagated the need for producing a new and wide range of renewable and sustainable energy technologies. Liquid desiccant dehumidification technologies are the most optimistic approach due to their lower regeneration temperature required, a higher coefficient of performance, and the ability to be used during night hours. The factors responsible for the limited application of these systems are desiccant leakage, corrosion to the fabricating material, and carryover of desiccant droplets with the process air. To overcome these issues, a new multi-channel flat plate liquid desiccant air conditioning system has been developed and experimentally investigated. The performance of the system has been analyzed for the dehumidification and regeneration process. Calcium chloride has been used as a desiccant material with 40% and 35% by wt. concentration. Three sets of velocities of process air have been utilized, i.e., 0.9, 0.7, 0.5 m/s to investigate the system performance. Performance parameters, such as dehumidification rate, regeneration rate, dehumidification, and regeneration effectiveness, have been investigated in the present study. The liquid desiccant dehumidification system investigated in the present study includes a flat plate energy exchanger for heat and mass transfer between ambient moist air and liquid desiccant solution. This system conveys a large interfacial surface area between liquid desiccant solution and process air. Experimental results indicate that, in the dehumidification process, the ambient moist air has been dehumidified and cooled by 5.90 g kg−1 and 1.4°C, respectively, and dehumidification effectiveness of 0.239 has been achieved for the air velocity of 5 m/s at 40% concentration of the desiccant solution. Regeneration rate and effectiveness have been observed to be 0.014 g s−1 and 0.323, respectively, for the air velocity of 5 m/s at 35% concentration. The work presented in this study demonstrates the feasibility of the novel multi-layer flat plat liquid desiccant concept and provide growth and development to the liquid desiccant technologies for space air conditioning. Certain issues regarding the mass imbalance in the dehumidification and regeneration processes have been identified to be considered as future scope.
Nomenclature
| ω | = | Humidity ratio (g/kg) |
| Δω | = | Change in humidity ratio (g/kg) |
| m | = | Mass flow rate (kg/s) |
| T | = | Temperature (oC) |
| ΔT | = | Change in temperature (oC) |
| p | = | Partial pressure (kpa) |
| h | = | Specific enthalpy (kJ/kg) |
| φ | = | Mole fraction of solute particle |
| ᵡ | = | Concentration of desiccant solution (%) |
| ℇ | = | Effectiveness |
| Å | = | Rate of moisture absorption (g/kg) |
| Ɍ | = | regeneration rate (g/kg) |
| Subscripts | = | |
| a | = | Air |
| in | = | Inlet port |
| out | = | Outlet port |
| eqm | = | Equilibrium |
| d | = | Dehumidifier |
| r | = | Regenerator |
| s | = | Solution |
| Abbreviations | = | |
| VCS | = | Vapor Compression Systems |
| COP | = | Coefficient of Performance |
| HVAC | = | Heating Ventilation and Air Conditioning |
| ASHRAE | = | American Society of Heating Refrigeration and Air Conditioning Engineers |
| CaCl2 | = | Calcium Chloride |
| LiCl | = | Lithium Chloride |
| LiBr | = | Lithium Bromide |
| TEG | = | Triethylene Glycol |
| HCOOK | = | Potassium Formate |
| LDD | = | Liquid Desiccant Dehumidification |
| LDAC | = | Liquid Desiccant Air Conditioning |
| LiDS | = | Liquid Desiccant Solution |
| WBT | = | Wet Bulb Temperature |
| M.A.R | = | Moisture Absorption rate in the dehumidifier |
| M.R.R | = | Moisture Removal Rate in the regenerator |
Acknowledgments
The authors gratefully acknowledge the financial support provided by SERB-DST, Govt. of India (Grant no. EEQ/2017/000227) and infrastructural facilities provided by NIT-Kurukshetra for the present work.
Disclosure statement
No potential conflict of interest was reported by the authors.