九州大学　エネルギーウィーク2022 r nerqy Week 2022 Combined desiccant dehumidification and dew point evaporative cooling A potential greener and cheaper alternative to compressor-based air conditioners Lao, Marco², Frantisek Miksik b, Kyaw Thu ª,b, Takahiko Miyazaki ª,b *Thermal Energy Conversion Systems Laberatory, Department of Energy and Environmental Engineering. Interdisciplinary Graduate School of Engineering Sciences, Kyushu Universi koen, Kasuga, Fukuoka, 816-8580, Japan b International Institute for Carbon-Neutral Energy Research, Kyushu University, 744, Motooka, Nishi Ward, Fukuoka, 819-0385, Japan
Background
O O Air conditioners consume large amounts of electricity Heat-driven desiccant dehumidifier can reduce latent heat load while dew point evaporative cooling can reduce sensible heat load Independent desiccant dehumidification and dew point evaporative cooling.
Objective
The primary objective of this study is to investigate the feasibility of CoDECS in O conditioning hot and humid air to human thermal comfort levels via numerical simulations
O Numerical simulations were performed following the governing equations for heat and mass transfer in the proposed system
Wet air (wa) mass & energy balance
d Pv,wa Pvsat,wa ￣ Pv,wa Pv,waCpwa Combined water film & plate (wf) energy balance PwfCwf Pvsat,wa
Dry air (da) mass & energy balance

Uh,da Desiccant sorbent (sb) mass & energy balance d Pv,sb dt O PsbCpsb The instantaneous and equilibrium water uptake of RD Silica gel desiccant is expressed by the Linear Driving Force model and the DA model as follows O The following fixed CoDECS design parameters were used
O The following nominal and experimental variables were used during the simulation

Deeper dehumidification requires higher
50 60 40 Temperature [°C] Desiccant dehumidification increases the desiccant temperature consequently decreasing its moisture adsorption capacity Psychrometric plot of independent desiccant dehumidification and dew point evaporative cooling.
Results & Conclusion
Diversion of dehumidified air from dry to wet channel induces evaporative cooling thereby facilitating the decrease in dry channel temperature Humidity decreases along CoDECS length due to integration of desiccant Decrease in desiccant temperature promotes continuous dehumidification Due to reduced humidity, dew point evaporative cooling facilitates further decrease in temperature CoDECS can produce dry and cold air for a long time period. Temporal product air temperature and humidity profile. Effect of varying regeneration temperature, channel length, air velocity, and product air extraction ratio to product air minimum temperature & humidity in CoDECS.
Major References:
El-Sharkawy II (2011) On the linear driving force approximation for adsorption cooling applications. Int J Refrig 34:667–673. Lin J, Thu K, Bui TD, et al (2016a) Study on dew point evaporative cooling system with counter-flow configuration. Energy Convers Manag 109:153–165. Lin J, Thu K, Bui TD, et al (2016b) Unsteady-state analysis of a counter- fl ow dew point evaporative cooling system. 113:172–185. Mohammed RH, Mesalhy O, Elsayed ML, Su M (2017) Revisiting the adsorption equilibrium equations of silica gel / water for adsorption cooling applications Revisiting the adsorption equilibrium equations of silica-gel / water for adsorption cooling applications. Int J Refrig 86:40–47. Narayanan R, Saman WY, White SD, Goldsworthy M (2011) Comparative study of different desiccant wheel designs. Appl Therm Eng 31:1613–1620. Temperature and humidity distribution along the dry and wet channels of CoDECS at nominal operating condition and t = 500s. Psychrometric plot of dry air in CoDECS at nominal  operating condition and at different time periods. Various strategies may be employed in CoDECS to produce air with reduced temperature and humidity such as: 0 increase in regeneration temperature; □ increase in system length; △ decrease in air velocity; or ♦ reduction of extraction ratio. Combined desiccant dehumidification and dew point evaporative cooling system (CoDECS). Combination of desiccant dehumidification in dew point evaporative cooler (DPEC) ▷ Evaporative cooling will limit temperature increase in the desiccant ▷ Lower desiccant temperature will increase moisture adsorption capacity Proposed system