## 4 Results and Discussion
### EAHX's Capacity to Meet the Room Design Cooling Load Demand  
In Section 4.1, it was concluded that, for the studied EAHX, the ability for standalone cooling (warranting room setpoint temperature) is lost as outdoor temperatures rise above 32 \({}^{\circ}\)C. Indeed, Table 1 states a room design cooling load demand of 50 W/m\({}^{2}\) when  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{1}{c}{**Measured**} & \multicolumn{1}{c}{**Analytical (Case 1)**} & \multicolumn{1}{c}{**Analytical (Case 2)**} \\  & & **8000 m\({}^{3}\)/h; \(x/L^{*}=0.75\)** & **16,000 m\({}^{3}\)/h; \(x/L^{*}=0.575\)** \\ \hline \multirow{3}{*}{\(\dot{Q}_{\text{rm}}\)} & Point(s) in Figure 11 & \(\underline{\text{n}}\)4) & \(\underline{\text{n}}\)5) & \(\underline{\text{n}}\)6) \\  & [kW] & 7\(\sim\)11 & 11 & 13.75 \\  & [W/m\({}^{2}\)] & 15.5\(\sim\)24.4 & 24.4 & 30.5 \\ \hline \multirow{3}{*}{\(\dot{Q}_{\text{oa}}\)} & Point(s) in Figure 11 & \(\underline{\text{n}}\)6) & \(\underline{\text{n}}\)6) & \\  & [kW] & 13.75 & 13.75 & — \\  & [W/m\({}^{2}\)] & 30.5 & 30.5 & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of load removal measurements with results determined from analytical expressions when the design outdoor air temperature is considered, \(T_{a0}=37\)\({}^{\circ}\)C. Values of specific load removal are obtained using the room floor area \(A_{\text{rm}}=450\) m\({}^{2}\).  
outdoor air temperature is 37 \({}^{\circ}\)C, whereas Table 2 shows that for Case 1 (as defined in Section 2.4), with 8000 m\({}^{3}\)/h flowrate, the EAHX's maximum measured room load removal is 24.4 W/m\({}^{2}\), half the design value.  
Since the design ventilation rate stated in Table 1 is 16,000 m\({}^{3}\)/h, to study the increase in the EAHX's airflow rate, Figure 11 includes the line, \(\tilde{Q}_{\rm rm,\tilde{V}=16,000\rm m^{3}/h}^{\rm analy.}\), consisting of orange vertical marks, depicting room air load removal results when analytical expressions are used with two (1 m diameter) 70 m long pipes and 16,000 (=2 \(\times\) 8000) m\({}^{3}\)/h ventilation rate.  
Table 2 highlights the \(\tilde{Q}_{\rm rm,\tilde{V}=16,000\rm m^{3}/h}^{\rm analy.}\) result in Figure 11, considering the design outdoor air temperature \(T_{\rm a0}=37\)\({}^{\circ}\)C, which corresponds to Case 2 (also defined in Section 2.4). For this case, the estimate of room air load extraction is 13.75 kW (point \(\widehat{\rm n6}\)), or 30.5 W/m\({}^{2}\).  
This result represents more than 60% of the design room cooling load demand, 50 W/m\({}^{2}\); still, it is concluded that despite the increased ventilation rate, the built EAHX is incapable, on its own, of canceling the room design heat gains. Only in the case where building thermal mass and nighttime ventilation allows a temperature difference \(T_{\rm as}-T_{\rm aL}\approx-1.6\) K, equivalent to room load removal \(\tilde{Q}_{\rm rm}^{\rm bldg}\approx 8.75\) kW, is the design cooling demand specification met. If the building cooling capacity \(\tilde{Q}_{\rm rm}^{\rm bldg}\) is lower than 8.75 kW (19.5 W/m\({}^{2}\)), the room air temperature rises above the 32 \({}^{\circ}\)C upper free-floating setpoint.  
Hence, it is concluded that, for the large-diameter EAHX described in this paper and for the hottest summer days, with outdoor temperatures exceeding 32 \({}^{\circ}\)C, full standalone cooling capability requires that the cooling in the EAHX is supplemented with cooling obtained from the use of the building's structural elements thermal mass in combination with forced nighttime ventilation, as described in Table 1 and as previously mentioned in the scientific literature [14; 23; 39].