# Study the Effect of Operating Temperature on Performance in Dry Scroll Vacuum Pump
## 4 Conclusions  
The transient numerical model of the multi-stage dry scroll vacuum pump is established by the CFD method and dynamic mesh technology. Under the suction pressure of 1000 Pa, the simulation calculation is carried out at different operating temperatures of fixed scrolls (25 \({}^{\circ}\)C, 45 \({}^{\circ}\)C, and 65 \({}^{\circ}\)C). The pumping speed and gas compression power are analyzed. The energy efficiency ratio of the dry scroll vacuum pump is evaluated. This research provides a transient simulation method using dynamic mesh technology for the study of dry scroll vacuum pumps. The following conclusions can be drawn.  
Based on the spring smoothing method, the numerical simulation model of the multi-stage dry scroll vacuum pump is established, and the unsteady compressible flow calculation is realized. Compared with the experimental pumping speed, the pumping speed error calculated by CFD simulation is \(-\)5.7%, which verifies the accuracy of the numerical model.  
Figure 11: EER changing with the operating temperature.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Suction** & **Operating** & **Pumping** & **Input** & **Energy Efficiency Ratio** \\
**Pressure/kPa** & **Temperature/K** & **Speed/L/min** & **Power/W** & **/L/(min-W)** \\ \hline
1 & 298.15 & 189.84 & 30.99 & 6.1263 \\
1 & 318.15 & 186.59 & 30.49 & 6.1189 \\
1 & 338.15 & 179.15 & 29.75 & 6.0212 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Energy efficiency ratio.  
Under different operating temperatures, the pumping speed and the gas compression power change significantly. With the rising pump cooling capacity, the pumping speed increases. When the reduction of the operating temperature is from 338.15 K to 298.15 K, the pumping speed is increased by approximately 5.97%. The gas compression power of the dry scroll pump is related to pumping speed. With the rising pump cooling capacity, the gas compression power increases. The gas compression power is increased by approximately 4.32% when the operating temperature is reduced from 338.15 K to 298.15 K. With the same geometric design parameters, by improving the cooling capacity of the pump body, the pumping speed can be increased, and gas compression power can be reduced.  
The energy efficiency ratio of the dry scroll pump is proposed. The energy efficiency ratio of the scroll pump is related to the operating temperature of the pump. With decreasing the temperature of the pump body, the energy efficiency ratio increased. The energy efficiency ratio is increased by approximately 1.745% when the operating temperature is reduced from 338.15 K to 298.15 K.  
This research can provide a theoretical basis for the design and application of the cooling system of the dry scroll vacuum pump, and these results are of great significance to the structural design and optimization of the dry scroll vacuum pump.  
Conceptualization, Y.-L.Z. and X.-J.Y.; methodology, Y.-L.Z. and X.-J.Y.; software, Y.-L.Z.; validation, Y.-L.Z. and X.-J.Y.; formal analysis, Y.-L.Z. and X.-J.Y.; investigation, Y.-L.Z. and J.-N.D.; resources, X.-J.Y. and D.-C.B.; data curation, Y.-L.Z. and X.-J.Y.; writing--original draft preparation, Y.-L.Z.; writing--review and editing, X.-J.Y. and J.-N.D.; visualization, Y.-L.Z. and J.-N.D.; supervision, X.-J.Y.; project administration, X.-J.Y. and D.-C.B.; funding acquisition, X.-J.Y. and D.-C.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Key Scientific Instrument and Equipment Development Project of China (2013 YQ24042101).  
Not applicable.  
The authors declare no conflict of interest.