## 4 Conclusions  
In this paper, an OAR system is proposed to be coupled with the air compression section in a cryogenic air separation unit. Due to its small temperature difference between the heat source and heat sink, the OAR system can reduce the compressed air to a relatively  
Figure 11: Influences of feed air temperature and humidity ratio on _ESR_ and _COP_. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Equipment** & **Design Parameters** & **Investment Cost (USD)** \\ \hline \hline  & OAR system & 711,501 \\ SAHEX1 & A = 295.4 m\({}^{2}\) & 73,522 \\ SAHEX2 & A = 285.3 m\({}^{2}\) & 71,871 \\ SAHEX3 & A = 253.7 m\({}^{2}\) & 66,594 \\ CWAHEX1 & A = 198.1 m\({}^{2}\) & 56,813 \\ CWAHEX2 & A = 293.1 m\({}^{2}\) & 73,148 \\ CWAHEX3 & A = 191 m\({}^{2}\) & 55,510 \\ Absorber & A = 502.2 m\({}^{2}\) & 104,477 \\ Evaporator & A = 401.5 m\({}^{2}\) & 79,991 \\ Open generator & A = 424.3 m\({}^{2}\) & 84,642 \\ ACT1 & Diameter = 3.5 m, Height = 3 m & 19,533 \\ Pump & Volume rate = 263.8 m\({}^{3}\)/h & 16,538 \\ Fan & Volume rate = 38.2 m\({}^{3}\)/s & 8862 \\ \hline \hline \multicolumn{3}{c}{Annual operation, maintenance, and management cost} & 71,222 \\ \hline \hline  & Conventional cooling system & 308,988 \\ \hline \hline  & Intercooler1 & A = 328.69 m\({}^{2}\) & 72,978 \\ Intercooler2 & A = 345.17 m\({}^{2}\) & 75,557 \\ Intercooler3 & A = 383.09 m\({}^{2}\) & 81,361 \\ WCT & Diameter = 2.6 m, Height = 1.8 m & 10,850 \\ ACT1 & Diameter = 3.7 m, Height = 3 m & 19,640 \\ ACT2 & Diameter = 4 m, Height = 3.2 m & 23,300 \\ Pumps & Volume rate = 2844 m\({}^{3}\)/h & 25,300 \\ \hline \hline \multicolumn{3}{c}{Annually project revenue (USD)} & 640,986 \\ \hline \hline  & 5,423,691 (based on Capital cost of OAR) \\ \hline \hline  & 5,423,691 (based on Capital cost of OAR) \\ \hline \hline  & 5,709,802 (based on Net Capital cost of cooling system) \\ \hline \hline  & 1.32 year (based on Capital cost of OAR) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Results of economic analysis. low temperature by the close matching between its generation heat and cooling capacity. The close matching also makes it possible to realize the low evaporation temperature with a more simply structured OAR without external heat sinks. The coupling of the OAR system with the air compression section has been studied in this paper and proved to be technologically viable and profitable. The energy distribution principle and energy conversion principle between the multi-stage waste compression heat and cooling capacity of the OAR under different working conditions are discussed. The profitability is also analyzed. The main conclusions are summarized below:  
1. The distribution of cooling demand of compressed air, which corresponds to the cooling capacity of the SAHEXs and CWAHEXs of the OAR system, is crucial for the system balance and energy saving performance. Effects of operating parameters, including evaporation temperature, solution-to-air flow ratio, and the approach temperature of the SAHEXs, have been analyzed to illuminate the energy distribution and conversion principle. Ranges of approach temperatures of heat exchangers are optimized under different suction temperatures. The lower limit of approach temperature corresponds to the maximum ESR. 2. Feed air temperature and humidity ratio have a great impact on the system performance and energy saving potential. ESR ranges from 0.52-8.05%, corresponding to the temperature range of 5-30 \({}^{\circ}\)C and humidity range of 0.002-0.010 kg/kg. The annual mean energy saving ratio of the ACS-OAR reaches 4.41% based on the air condition in Beijing. A much higher ESR can be expected by installing a dehydrator before the compressors, as the present ESR is calculated based on a high suction temperature to avoid condensation water in the compressors. 3.