## 4 Results and Discussion
### Performance Prediction of Case CCKEF System under Various Conditions
#### 4.2.2 Different Simultaneity Coefficient of Stoves  
There are generally 4-6 stoves in CCK, but not all of them are burning at the same time during cooking. By taking the case kitchen with four cauldron stoves and one stockpot as an example, the percentage of simultaneity coefficient of stoves (\(\varphi\)) is shown in Table 6. In this part, the air velocity, temperature and pollutant distribution of the kitchen cooking area at breathing height (in Figure 5, Line a) and the system purification efficiency were studied under four simultaneity coefficient values (\(\varphi\) = 0.2, 0.6, 0.8, 1). The results are shown in Figure 12.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Number of** \\ **Stoves** \\ **Burning** \\ \end{tabular} } & \multicolumn{5}{c}{**Usage State of Stoves**} & \multirow{2}{*}{\begin{tabular}{c} **Simultaneity** \\ **Factor (\(\varphi\))** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Percentage** \\ **(\%)** \\ \end{tabular} } \\ \cline{2-2} \cline{6-7}  & **S1** & **S2** & **S3** & **S4** & **S5** & **Factor (\(\varphi\))** & **(\%)** \\ \hline \hline \multirow{2}{*}{
\begin{tabular}{c} One \\ Three \\ Four \\ Five \\ \end{tabular} } & Frying & Off & Off & Off & Off & 0.2 & 16.9 \\  & Frying & Frying & Frying & Off & Off & 0.6 & 46.1 \\  & Frying & Frying & Frying & FStewing & Off & 0.8 & 33.8 \\  & Frying & Frying & Frying & FStewing & Stewing & 1 & 3.2 \\ \hline \end{tabular} Note: cooking process during lunch and dinner in canten-type kitchens is similar, so only the use state of stoves during brunch cooking was surveyed in this paper.  
\end{table}
Table 6: The use state of stoves in the case kitchen during brunch cooking.  
Figure 12: The indoor air environment of cooking area and system purification efficiency under different simultaneity coefficient of stoves (Q\({}_{\text{ex}}\) = 11,726 m\({}^{3}\)/h). (**a**) Air temperature; (**b**) Air velocity; (**c**) C6H6 concentration; (**d**) Purification efficiency.  
Figure 12a-c shows that the change in simultaneity coefficient of stoves affected the air velocity, temperature and pollutant concentration distribution of the cooking area. When the simultaneity coefficient was 0.2, the temperature of the cooking area near the stove was high at 24-28 \({}^{\circ}\)C, while the temperature of other areas was about 24 \({}^{\circ}\)C. When the simultaneity usage factor ranged from 0.6 to 1, the temperature of the cooking area with personnel standing was high at 24-30 \({}^{\circ}\)C, while that of other areas was about 24 \({}^{\circ}\)C. This was because the presence of personnel decreased the air velocity (0.2-0.3 m/s) near the burning stoves, and the generated cooking heat could not be eliminated effectively. Due to its wall-hugging characteristics, the heat plume flowed leftward and upward. The larger the simultaneity coefficient was, the more serious the pollutant spillage. As shown in Figure 12d, the purification efficiency of the electrostatic purifier decreased as the simultaneity coefficient of stoves increased. The purification efficiency also met the requirement of the minimum limit (85%) when all stoves were burning.