## 3 Case Study
### The Building (Being Cooled by the EAHX)  
Relevant for EAHX design are the building design specifications summarized in Table 1. Free-floating room temperatures are assumed, and on hot summer days, adaptive setpoint temperatures are considered as defined in standard EN 15251:2007 [28].  
Table 1 emphasizes the extent to which the design of the building and of the large-diameter EAHX are related (similar to the design of naturally ventilated office buildings). Use of building thermal mass and forced nighttime ventilation to extend EAHX cooling capacity has been mentioned and used previously [14; 23; 39] and is also considered in the present case study. Moreover, complementing this \"supply side\" increase in room load extraction, careful building design allowed a reduction in sensible cooling demand in the room to approximately 50 W/m\({}^{2}\). Special care was placed, also, in the selection and location of room air supply diffusers and air extractor grilles, preventing local draft discomfort.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Bldg Parameter** & **Design Value** & **Comment** \\ \hline
1. Floor area \({}^{\dagger}\), \(A_{\text{rm}}\) & 450 m\({}^{2}\) (EAHX cooled) & 1a. Total floor area 750 m\({}^{2}\). \\ \hline
2. Room height, \(\overline{h}_{\text{rm}}\) & 3 m & 2a. Average value. \\ \hline
3. Outdoor air temperature & \
\begin{tabular}{l} 37 \({}^{\circ}\)C (equal to EAHX inlet temperature, \\ \(T_{\text{a0}}\)) \\ \end{tabular} &
\begin{tabular}{l} 3a. ASHRAE’s 0.4\% annual dry bulb \\ design value for Beja, Portugal [40]. \\ \end{tabular} \\ \hline
4. Room setpoint temperature \({}^{\dagger}\), \(T_{\text{ar}}\) & \
\begin{tabular}{l} 32 \({}^{\circ}\)C (upper limit according to data in \\ Figure 7) \\ \end{tabular} &
\begin{tabular}{l} 4a. Ventilation and cooling with EAHX is \\ handled as equivalent to natural \\ ventilation, allowing free-floating indoor \\ air temperatures. \\ \end{tabular} \\ \hline
5. Room (air) cooling load demand \({}^{\dagger}\), \(Q^{\prime\prime}_{\text{rm}}\) &
\begin{tabular}{l} 5a. Rooms are used for light office work; \\ have low occupancy density; design \\ makes use of structural elements’ thermal \\ and gains through the building envelope \\ \end{tabular} \\ \hline
6. Room ach \({}^{\dagger}\), \(n_{\text{rm}}\) & \
\begin{tabular}{l} \(\sim\)11 h\({}^{-1}\) (100\% fresh air system as in \\ \"Case 2\"); \\ \(\bar{V}=A\cdot\overline{h}\cdot n_{\text{rm}}\approx\) 16,000 m\({}^{3}/\)h \\ \(\approx\)4.5 m\({}^{3}/\)s \\ \end{tabular} &
\begin{tabular}{l} 6a. Local draught discomfort is prevented \\ with careful selection and placement of \\ air supply diffusers and air extractor \\ grilles; \\ \(\bar{b}\). During summer, larger (controlled) \\ airflow velocities in the room working \\ area offset larger air temperatures [28]. \\ \end{tabular} \\ \hline
7. Supply air temperature \({}^{\dagger}\), \(T_{\text{as}}\) & \
\begin{tabular}{l} \(\sim\)4 K below the design upper \\ free-floating setpoint temperature (28 \({}^{\circ}\)C \\ when \(T_{\text{ar}}=32\)\({}^{\circ}\)C) \\ \end{tabular} &
\begin{tabular}{l} 7a. Use of building’ structural elements \\ (foundations) thermal mass in \\ combination with forced nighttime \\ ventilation allows a design temperature \\ gradient \(T_{\text{as}}-T_{\text{aL}}\) between the air \\ supplied to the room and the air as it \\ exits the EAHX between \(-1\) and \(-2\) K. \\ \end{tabular} \\ \hline \end{tabular}
\end{table}
Table 1: Building design specifications relevant to the EAHX design.