Airflow simulation and optimization based on CO2 concentration in plant factory

doi:10.11949/0438-1157.20241354

Abstract

Abstract:

The accurate analysis of the distribution of airflow tissue in plant factories is an important basis for the study of plant healthy growth, but there is a lack of research on the distribution of $C O 2$ concentration in plant factories. Computational fluid dynamics (CFD) method was used to establish a mathematical model of porous media and net photosynthesis, and the concentration of $C O 2$ and energy consumption of air supply fans under different air supply speeds were explored. Based on the NSGA-Ⅱ genetic algorithm, multi-objective optimization was carried out with the velocity of the air supply outlet as the decision variable, the airflow velocity of the plant area, the concentration of $C O 2$ and the energy consumption of the fan as the objective functions, and the Pareto optimal solution was obtained. When the air supply speed was 3.26 m/s, the average velocity of the plant area is 0.37 m/s and $C O 2$ concentration of the plant area is 277 $μ m o l / m o l$ , and the energy consumption of the fan is 23.26 W.

Key words: plant factory, porous media, carbon dioxide, mathematical models for photosynthesis, genetic algorithm

摘要：

植物工厂内气流组织的精准化分析是探究植物健康生长的重要基石，然而，目前针对植物工厂内部 $C O 2$ 浓度分布的研究仍较为匮乏。采用计算流体力学（CFD）方法构建了植物多孔介质模型及净光合作用数学模型，旨在探讨不同送风速度下植物区域内气流速度 $C O 2$ 、浓度分布以及送风风机能耗的情况。基于NSGA-Ⅱ遗传算法，以送风口速度为决策变量，植物区域的气流速度、 $C O 2$ 浓度以及风机能耗作为目标函数，进行了多目标优化。优化结果得出了帕累托最优解：当送风速度为3.26 m/s时，植物区域的平均气流速度为0.37 m/s $, C O 2$ 浓度为277 $μ m o l / m o l$ ，同时风机的能耗为23.26 W。

关键词: 植物工厂, 多孔介质, 二氧化碳, 光合作用模型, 遗传算法

CLC Number:

TK 05

Jichao GUO, Xiaoxiao XU, Yunlong SUN. Airflow simulation and optimization based on $C O 2$ concentration in plant factory[J]. CIESC Journal, 2025, 76(S1): 237-245.

郭纪超, 徐肖肖, 孙云龙. 基于植物工厂中的CO₂浓度气流模拟及优化研究[J]. 化工学报, 2025, 76(S1): 237-245.

Figures/Tables 14

Fig.1 Geometry model of plant factory

Fig.2 Structured mesh of plant factory

Table 1 Boundary conditions

边界条件	参数
进风口	入口速度 1.70 m/s，温度 22.5℃, CO₂摩尔分数 0.033%
出风口	出口压力 101325 Pa，温度 22.5℃, CO₂摩尔分数 0.033%
LED灯板	恒温壁面 32℃
植物区域	多孔介质区域， $C O 2$ 组分源项通过UDF实现
栽培板	绝热壁面
壁面	绝热壁面

Table 1 Boundary conditions

边界条件	参数
进风口	入口速度 1.70 m/s，温度 22.5℃, CO₂摩尔分数 0.033%
出风口	出口压力 101325 Pa，温度 22.5℃, CO₂摩尔分数 0.033%
LED灯板	恒温壁面 32℃
植物区域	多孔介质区域， $C O 2$ 组分源项通过UDF实现
栽培板	绝热壁面
壁面	绝热壁面

Table 2 Governing equations

方程

源项

质量方程：

∂ ρ ∂ t + d i v ρ v = 0

动量方程： $∂ (ρ u) ∂ t + d i ρ v u = d i v μ g r a d u - ∂ p ∂ x + S u$

$∂ (ρ u) ∂ t + d i v ρ v v = d i v μ g r a d v - ∂ p ∂ y + S v$

$∂ (ρ u) ∂ t + d i v ρ v w = d i v μ g r a d w - ∂ p ∂ z + S w$

$S u = - ρ C D L A D v u$

$S v = - ρ C D L A D v v$

$S w = - ρ C D L A D v w$

能量方程： $∂ (ρ T) ∂ t + d i v ρ v T = d i v λ C p g r a d T + S T C p$

组分输运方程： $∂ ρ C ∂ t + d i v ρ v C = d i v D C g r a d C + S c$

$S T = 0$

$S c = 0.78 × α I τ ρ C α I + τ ρ C L A D$

Table 2 Governing equations

方程

源项

质量方程：

∂ ρ ∂ t + d i v ρ v = 0

动量方程： $∂ (ρ u) ∂ t + d i ρ v u = d i v μ g r a d u - ∂ p ∂ x + S u$

$∂ (ρ u) ∂ t + d i v ρ v v = d i v μ g r a d v - ∂ p ∂ y + S v$

$∂ (ρ u) ∂ t + d i v ρ v w = d i v μ g r a d w - ∂ p ∂ z + S w$

$S u = - ρ C D L A D v u$

$S v = - ρ C D L A D v v$

$S w = - ρ C D L A D v w$

能量方程： $∂ (ρ T) ∂ t + d i v ρ v T = d i v λ C p g r a d T + S T C p$

组分输运方程： $∂ ρ C ∂ t + d i v ρ v C = d i v D C g r a d C + S c$

$S T = 0$

$S c = 0.78 × α I τ ρ C α I + τ ρ C L A D$

Fig.3 Mesh independence validation

Fig.4 Experiment and simulationn comparison of velocity in cross-section Z=1.15m

Fig.5 Experiment and simulation comparison of CO2 concentration in cross-section X=1.20 m

Fig.6 CO2 concentration distribution contours (cross-section X=1.20, 2.40 m)

Fig.7 Contours of CO2 concentrations at different times (cross-section X=1.20 m)

Fig.8 Schematic diagram of CO2 concentration over time in different planes

Fig.9 Velocity distribution contours of plane X=1.0 m at different velocities

Fig.10 CO2 Concentration distribution contours of plane X=1.0 m at different velocities

Table 3 Pressure drop and energy consumption at different supply speeds

送风速度/(m/s)	进出口压降/Pa	送风口面积/m²	能耗/W
1.7	2.73	0.64	3.83
2.5	5.69	0.64	11.74
3.4	9.60	0.64	26.95
4.2	14.88	0.64	51.59
5.1	20.93	0.64	88.12

Fig.11 Multi-objective optimization solves the optimal air supply speed

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