## 3 Results
### Influence of Different Aperture Ratios on the Temperature in the Cabinet  
Figure 4 shows the temperature distribution of each layer in the cabinet for shelves of different aperture ratios (average temperature in a single cycle). It can be seen from the graph that with increasing open porosity, the cabinet temperature first presented a drop, followed by a rising trend; the highest temperature fell from 10.2 \({}^{\circ}\)C to 5.6 \({}^{\circ}\)C and then increased to 10.9 \({}^{\circ}\)C.  
In order to represent the overall temperature conditions in the cabinet, the overall uniformity and average temperature were used to evaluate them, and the results are shown in Figure 5. The overall uniformity and average temperature first decreased and then increased with the increasing aperture ratio. At the different aperture ratios, the respective overall uniformity values were 6.7 \({}^{\circ}\)C, 5.4 \({}^{\circ}\)C, 4.6 \({}^{\circ}\)C, 3.8 \({}^{\circ}\)C, and 6.8 \({}^{\circ}\)C, and the minimum corresponding aperture ratio was 25%. The average temperature in the cabinet changed with the aperture ratio to 7.2 \({}^{\circ}\)C, 5.6 \({}^{\circ}\)C, 4.1 \({}^{\circ}\)C, 5.0 \({}^{\circ}\)C, and 7.4 \({}^{\circ}\)C; these values are consistent with the overall uniformity. It can be seen from the graph that for a frame aperture ratio of 50%, when the average temperature inside the cabinet was a barely suitable preservation temperature (0-4 \({}^{\circ}\)C) for animal, poultry, and aquatic products, the corresponding temperature difference was 3.8 \({}^{\circ}\)C only. The quality difference in each layer of product due to temperature inside the cabinet would thus decrease. The non-uniformity coefficient is often used as an important indicator to evaluate spatial differences [24,25]. The temperature non-uniformity coefficients in the refrigerated display cabinet are shown in Table 1. When the shelf aperture ratio was 0%, the temperature non-uniformity coefficient was 3.7, and the quality difference of each product area inside the cabinet was smaller. However, as the porosity increased from 12.5% to 90%, the unevenness  
Figure 4: The influence of different aperture ratios on the temperature of each shelf inside the cabinet. Figure 5: The influence of different aperture ratios on the average temperature inside the cabinet. coefficient fluctuated little, indicating that the increased porosity had little influence on the uniformity of the temperature distribution. From Table 1, it can be seen that, except for the small non-uniformity coefficient at a 0% aperture ratio, the difference in the non-opening coefficient of other aperture ratios was not large, which indicates that the difference between shelf openings was significant. The electricity consumption of refrigerated display cabinets accounts for about 50% of the total electricity consumption of supermarkets [26]. Therefore, the energy savings and environmental protection aspects of refrigerated display cabinets are particularly important. Figure 6 presents a comparison of the cooling times and heating times with different aperture ratios in a single period. The corresponding cooling times were 505 s, 427 s, 336 s, 329 s, and 373 s. The corresponding heating times were 162 s, 160 s, 200 s, 204 s, and 185 s. The longest heating time was 204 s, and the corresponding aperture ratio was 50%. The cooling time and heating time reflect the ability to maintain the temperature in the display cabinet, and they can represent the energy conservation and environmental protection status of the refrigerated display cabinet to a certain extent. Therefore, in this paper, we evaluate the cabinet's environmental performance through the temperature maintenance coefficient, obtained as the ratio of the cooling time and heating time; the results are shown in Table 1. It can be seen from Table 1 that the maximum temperature maintenance coefficient was 0.62, corresponding to a porosity of 50%, but there was little difference in the temperature maintenance coefficient for a porosity of 25%.