Numerical simulation and verification of heat and mass transfer characteristics in honeycomb hydrogel adsorption bed

doi:10.11949/0438-1157.20211107

Abstract

Abstract:

The adsorption characteristics of PAM-LiCl hydrogel composite adsorbent is studied. Based on the D-A equation, a three-dimensional mathematical model of the honeycomb gel adsorption bed is established. The adsorption/desorption dynamic phase of the adsorption bed under dry/wet conditions air simulated by COMSOL software. Combined with the experiment, the verification of the mathematical model is completed, and finally the optimization of the adsorption bed structure is realized. The results show that the honeycomb structure dramatically improves the adsorption/desorption performance of the adsorption bed. The water uptake rate is positively correlated with the porosity of the honeycomb mass transfer channel. The total water absorption first increases and then decreases. When the porosity is 20%, the total water absorption is the largest. The water uptake of the adsorption bed decreases with the increase of the thickness of the adsorption bed. When the air velocity is lower than 3.6 m/s, increasing the air velocity can significantly enhance the adsorption performance of the adsorption bed. The honeycomb adsorbent bed has good desorption performance and realizes complete desorption in hot air at 60℃.

Key words: adsorption, hydrogel, heat transfer, mass transfer, numerical simulation

摘要：

对PAM-LiCl水凝胶复合吸附剂进行了吸附特性实验研究，基于D-A方程拟合其特性曲线，建立了该凝胶蜂窝吸附床的三维数学模型，用COMSOL软件完成了吸附床干燥/湿润工况下的动态吸/脱附过程模拟，结合实验完成该数学模型的验证，最终实现吸附床结构的优化。研究表明，蜂窝结构大幅提升了吸附床的吸/脱附性能。吸附速率与蜂窝传质通道的孔隙度呈正相关；总吸水量先增大后减小，当孔隙度为20%时，总吸水量最大。吸附床的吸附量随吸附床厚度的增大而降低。当空气流速低于3.6 m/s时，提高空气流速能显著增强吸附床的吸附性能。蜂窝吸附床解吸性能良好，在60℃ & RH10%的热空气中可实现完全解吸。

关键词: 吸附, 水凝胶, 传热, 传质, 数值模拟

CLC Number:

TQ 424

Guodong ZHONG, Chaohe DENG, Yang WANG, Jiayun WANG, Ruzhu WANG. Numerical simulation and verification of heat and mass transfer characteristics in honeycomb hydrogel adsorption bed[J]. CIESC Journal, 2022, 73(3): 1083-1092.

钟国栋, 邓超和, 王洋, 王佳韵, 王如竹. 蜂窝状水凝胶吸附床传热传质特性数值模拟及验证[J]. 化工学报, 2022, 73(3): 1083-1092.

Figures/Tables 14

Fig.1 Physical model of honeycomb hydrogel adsorption bed

Table 1 Thermophysical properties of adsorbent and air

材料	热导率/(W/(m·K))	密度/ (kg/m³)	比定压热容/ (kJ/(kg·K))	吸附热/(kJ/kg)	水分扩散系数/(m²/s)
PAM-LiCl	0.4	1424.6	1600	2400	1.75×10^-10
空气	0.0263	1.293	1.005	—	2.82×10^-5

Fig.2 Adsorption experiment devic

Fig.3 Sorption characteristic curves for PAM-LiCl

Table 2 Parameters of fitting equations for PAM-LiCl

Section	ΔF/(kJ/kg)	Correlation curves	R²
Ⅰ	35.4-300.5	$w e q =$ 11.3686exp(-0.5519 $?$ F^0.3180)	0.9976
Ⅱ	300.5-307.2	$w e q =$ 12.05668-0.03888 $?$ F	0.98503
Ⅲ	307.2-600	$w e q =$ exp(22.65357-0.8074 $?$ F）	0.95296

Table 2 Parameters of fitting equations for PAM-LiCl

Section	ΔF/(kJ/kg)	Correlation curves	R²
Ⅰ	35.4-300.5	$w e q =$ 11.3686exp(-0.5519 $?$ F^0.3180)	0.9976
Ⅱ	300.5-307.2	$w e q =$ 12.05668-0.03888 $?$ F	0.98503
Ⅲ	307.2-600	$w e q =$ exp(22.65357-0.8074 $?$ F）	0.95296

Fig.4 Isothermal sorption kinetics of PAM-LiCl-CNT under different temperature

Fig.5 Model validation

Fig.6 Adsorbed water distribution of the hydrogel adsorption bed under 25℃ &RH75% adsorption condition

Fig.7 Adsorbed water distribution of different sections

Fig.8 Temperature responses of adsorbent bed and air

Table 3 Porosity corresponding to different pore sizes

孔径/mm	孔体积/mm³	吸附剂体积/mm³	孔隙度/%
0	0	12500	0
3.57	1250	11250	10
5	2454	10046	20
6.18	3750	8750	30
7.14	5000	7500	40

Fig.9 Effect of adsorption bed geometry on performance

Fig.10 Effect of air flow rate on performance of adsorption bed

Fig.11 Effect of air temperature on desorption performance of adsorption bed

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