Figure 1.
Greenhouse cross-section diagram.
Figure 1.
Greenhouse cross-section diagram.
Figure 2.
Locations of temperature sensors in the greenhouse: (a) side view; (b) overhead view.
Figure 2.
Locations of temperature sensors in the greenhouse: (a) side view; (b) overhead view.
Figure 3.
Internet-of-things transmission platform. (a) Platform of weather station. (b) Interior Sensor Platform.
Figure 3.
Internet-of-things transmission platform. (a) Platform of weather station. (b) Interior Sensor Platform.
Figure 4.
Greenhouse model. (a) Three-dimensional model. (b) Structured grids.
Figure 4.
Greenhouse model. (a) Three-dimensional model. (b) Structured grids.
Figure 5.
Grid independence verification. (a) Temperature verification. (b) Wind speed verification.
Figure 5.
Grid independence verification. (a) Temperature verification. (b) Wind speed verification.
Figure 6.
Validation of calculated and measured values. (a) Temperature validation. (b) Velocity validation.
Figure 6.
Validation of calculated and measured values. (a) Temperature validation. (b) Velocity validation.
Figure 7.
Solar greenhouse study cross-section: (a) x = 4000 mm (crop area); (b) x = 600 mm (non-crop area).
Figure 7.
Solar greenhouse study cross-section: (a) x = 4000 mm (crop area); (b) x = 600 mm (non-crop area).
Figure 8.
Wind pressure ventilation characteristics in the high-altitude area of: (a) x = 4000 mm, Re; (b) x = 600 mm, Re; (c) x = 4000 mm, wind pressure; (d) x = 600 mm, wind pressure.
Figure 8.
Wind pressure ventilation characteristics in the high-altitude area of: (a) x = 4000 mm, Re; (b) x = 600 mm, Re; (c) x = 4000 mm, wind pressure; (d) x = 600 mm, wind pressure.
Figure 9.
Wind pressure ventilation characteristics in the plain area of: (a) x = 4000 mm, Re; (b) x = 600 mm, Re; (c) x = 4000 mm, wind pressure; (d) x = 600 mm, wind pressure.
Figure 9.
Wind pressure ventilation characteristics in the plain area of: (a) x = 4000 mm, Re; (b) x = 600 mm, Re; (c) x = 4000 mm, wind pressure; (d) x = 600 mm, wind pressure.
Figure 10.
Variation in wind pressure characteristic parameters in high−altitude and plain areas of: (a) x = 4000 mm, Re; (b) x = 600 mm, Re; (c) x = 4000 mm, wind pressure; (d) x = 600 mm, wind pressure.
Figure 10.
Variation in wind pressure characteristic parameters in high−altitude and plain areas of: (a) x = 4000 mm, Re; (b) x = 600 mm, Re; (c) x = 4000 mm, wind pressure; (d) x = 600 mm, wind pressure.
Figure 11.
Thermal pressure ventilation characteristics in the high−altitude area of: (a) x = 4000 mm, density; (b) x = 600 mm, density; (c) x = 4000 mm, heat pressure; (d) x = 600 mm, heat pressure.
Figure 11.
Thermal pressure ventilation characteristics in the high−altitude area of: (a) x = 4000 mm, density; (b) x = 600 mm, density; (c) x = 4000 mm, heat pressure; (d) x = 600 mm, heat pressure.
Figure 12.
Thermal pressure ventilation characteristics in the plain area of: (a) x = 4000 mm, density; (b) x = 600 mm, density; (c) x = 4000 mm, heat pressure; (d) x = 600 mm, heat pressure.
Figure 12.
Thermal pressure ventilation characteristics in the plain area of: (a) x = 4000 mm, density; (b) x = 600 mm, density; (c) x = 4000 mm, heat pressure; (d) x = 600 mm, heat pressure.
Figure 13.
Variation in thermal pressure characteristic parameters in high−altitude and plain areas of: (a) x = 4000 mm, density; (b) x = 600 mm, density; (c) x = 4000 mm, heat pressure; (d) x = 600 mm, heat pressure.
Figure 13.
Variation in thermal pressure characteristic parameters in high−altitude and plain areas of: (a) x = 4000 mm, density; (b) x = 600 mm, density; (c) x = 4000 mm, heat pressure; (d) x = 600 mm, heat pressure.
Figure 14.
Coupling ventilation characteristics in the high−altitude area of: (a) x = 4000 mm, velocity; (b) x = 600 mm, velocity; (c) x = 4000 mm, temperature; (d) x = 600 mm, temperature.
Figure 14.
Coupling ventilation characteristics in the high−altitude area of: (a) x = 4000 mm, velocity; (b) x = 600 mm, velocity; (c) x = 4000 mm, temperature; (d) x = 600 mm, temperature.
Figure 15.
Coupled ventilation characteristics in the plain area of: (a) x = 4000 mm, velocity; (b) x = 600 mm, velocity; (c) x = 4000 mm, temperature; (d) x = 600 mm, temperature.
Figure 15.
Coupled ventilation characteristics in the plain area of: (a) x = 4000 mm, velocity; (b) x = 600 mm, velocity; (c) x = 4000 mm, temperature; (d) x = 600 mm, temperature.
Figure 16.
Variation in coupled ventilation parameters in high−altitude and plain areas of: (a) x = 4000 mm, velocity; (b) x = 600 mm, velocity; (c) x = 4000 mm, temperature; (d) x = 600 mm, temperature.
Figure 16.
Variation in coupled ventilation parameters in high−altitude and plain areas of: (a) x = 4000 mm, velocity; (b) x = 600 mm, velocity; (c) x = 4000 mm, temperature; (d) x = 600 mm, temperature.
Figure 17.
Sample values of greenhouse ventilation rate.
Figure 17.
Sample values of greenhouse ventilation rate.
Figure 18.
Ventilation rate correlation factor analysis. (a) Correlation coefficient calculation. (b) Significance analysis.
Figure 18.
Ventilation rate correlation factor analysis. (a) Correlation coefficient calculation. (b) Significance analysis.
Figure 19.
Fitted ventilation rate in the high-altitude area with the plain area ventilation rate.
Figure 19.
Fitted ventilation rate in the high-altitude area with the plain area ventilation rate.
Figure 20.
Comparison of calculated and fitted results before the correction of the ventilation rate in the plain area.
Figure 20.
Comparison of calculated and fitted results before the correction of the ventilation rate in the plain area.
Figure 21.
Comparison of the fitted and sample values in the high-altitude area.
Figure 21.
Comparison of the fitted and sample values in the high-altitude area.
Figure 22.
Comparison of predicted and sample values of the greenhouse ventilation rate in the high-altitude area.
Figure 22.
Comparison of predicted and sample values of the greenhouse ventilation rate in the high-altitude area.
Table 1.
Sensor Specifications.
Table 1.
Sensor Specifications.
Instrument | Measurement Data | Measurement Range | Precision |
---|
PT100 | Temperature | −40 °C~80 °C | ±0.2 °C |
Humidity sensor | Humidity | 0 RH~99% RH | ±3% RH (5% RH~95% RH, 25 °C) |
Thermal bulb wind speed sensor | Velocity | 0~5 m/s | ±(0.03 m/s + 2% reading) |
Light sensor | Total indoor radiation | 0~2000 W/m2 | ±10 W/m2 |
PT100 | Temperature | −40 °C~80 °C | ±0.2 °C |
Table 2.
Basic parameters and boundary condition settings.
Table 2.
Basic parameters and boundary condition settings.
Parameters | Boundary Conditions | Parameters | Boundary Conditions |
---|
Air Density (kg/m3) | 0.761 | Pressure (Kpa) | 66.1 |
Air thermal conductivity (W·m−1·K−1) | 0.027 | Wall temperature (°C) | 23.8 |
Viscosity (m2/s) | 2.63 × 10−5 | Inlet velocity (m/s) | 0.27 |
Specific heat of air (J·kg−1·K−1) | 1005.93 | Inlet temperature (°C) | 30.5 |
Wall density (kg/m3) | 1600 | Outlet temperature (°C) | 28.5 |
Specific heat of the wall (J·kg−1·K−1) | 1051 | Crop temperature (°C) | 27.3 |
Thermal conductivity of walls (W·m−1·K−1) | 0.76 | Covering film temperature (°C) | 47.0 |
Soil density (kg/m3) | 1700 | Soil temperature (°C) | 27.5 |
Soil specific heat (J·kg−1·K−1) | 1010 | Crop canopy pressure drop coefficient (°C) [10,34] | 0.395 |
Soil thermal conductivity (W·m−1·K−1) | 0.8 | Internal dropout factor (C1) [10,34] | 0.2 |
Covering film density (kg/m3) | 950 | Crop porosity | 0.7 |
Covering film specific heat (J·kg−1·K−1) | 1600 | leaf area index (LAI) | 2.6 |
Thermal conductivity of covering film (W·m−1·K−1) | 0.29 | Latent heat of evaporation (J·kg−1) | 2.43 |
Crop density (kg/m3) | 560 | Saturated water vapor pressure difference (Pa) | 650 |
Crop specific heat (J·kg−1·K−1) | 2100 | d (mm) | 6.0 |
Crop thermal conductivity (W·m−1·K−1) | 0.19 | ra (s·m−1) | 225.4 |
Indoor radiation (W/m2) | 743 | rs (s·m−1) | 200 |
Air temperature (°C) | 29.55 | Internal heat source (W/m3) | 19.96 |
Table 3.
CFD Validation.
Observation Point | Temperature (°C) | Velocity (m/s) |
---|
Measurement Value | Calculated Value | Measurement Value | Calculated Value |
---|
1 | 27.6 | 29.34 | 0.17 | 0.151 |
2 | 27.3 | 28.91 | 0.21 | 0.199 |
6 | 28.3 | 29.76 | 0.21 | 0.186 |
7 | 35 | 34.12 | 0.29 | 0.307 |
11 | 28.5 | 29.79 | 0.74 | 0.637 |
ARE | - | 4.880% | - | 9.525% |
MAE | - | 1.396 | - | 0.035 |
RMSE | - | 1.428 | - | 0.049 |
R2 | - | 0.9982 | - | 0.9869 |
Table 4.
Main calculation boundaries.
Table 4.
Main calculation boundaries.
Inlet Velocity (m/s) | Reference Temperature (°C) | Reference Pressure (Pa) | Inlet Temperature (°C) | Outlet Temperature (°C) |
---|
1.95 | 17.30 | 66,780 | 19.0 | 18.1 |
0.27 | 29.55 | 66,100 | 30.5 | 28.5 |
1.3 | 23 | 66,340 | 24 | 23.8 |
Table 5.
Boundary conditions for ventilation calculation.
Table 5.
Boundary conditions for ventilation calculation.
Period | Reference Temperature (°C) | Velocity (m/s) | Inlet Temperature (°C) | Outlet Temperature (°C) |
---|
9:00 | 14.18 | 1.21 | 15.6 | 15.7 |
10:00 | 17.30 | 1.95 | 19.0 | 18.1 |
11:00 | 23.30 | 0.42 | 24.6 | 21.7 |
12:00 | 23.48 | 1.91 | 24.8 | 22.2 |
13:00 | 27.75 | 0.15 | 28.8 | 25.8 |
14:00 | 29.55 | 0.27 | 30.5 | 28.5 |
15:00 | 30.60 | 0.14 | 28.8 | 28.2 |
16:00 | 27.85 | 1.11 | 29.4 | 26.8 |
17:00 | 24.45 | 1.32 | 26.3 | 24.6 |
18:00 | 23 | 1.3 | 24 | 23.8 |
Table 6.
Values calculated for ventilation−rate−related factors.
Table 6.
Values calculated for ventilation−rate−related factors.
Period | Ventilation Rate (m3/s) | Inlet Velocity (m/s) | ΔT (°C) | Δρ (kg/m3) | Total Radiation (W/m2) | Heat Source (W/m3) |
---|
9:00 | 41.51 | 1.21 | 1.20 | 0.003 | 40 | 116.20 |
10:00 | 66.76 | 1.95 | 0.93 | 0.004 | 301 | 113.14 |
11:00 | 14.95 | 0.42 | 5.53 | 0.015 | 523 | 8.24 |
12:00 | 65.24 | 1.91 | 2.88 | 0.005 | 213 | 25.27 |
13:00 | 7.09 | 0.15 | 7.35 | 0.011 | 394 | 11.94 |
14:00 | 9.25 | 0.27 | 7.43 | 0.008 | 743 | 19.96 |
15:00 | 4.80 | 0.14 | 9.85 | 0.022 | 639 | 12.88 |
16:00 | 37.76 | 1.11 | 6.80 | 0.000 | 412 | 53.52 |
17:00 | 44.94 | 1.32 | 5.15 | 0.002 | 366 | 75.11 |
18:00 | 44.27 | 1.30 | 3.90 | 0.003 | 296 | 60.70 |