## 2 Problem Formulation
### Description of Measurement Technique and Equipment  
The experimental program comprised two sets of measurements. In each experiment simultaneous measurements of air velocity and air temperature at four points were performed. An 8-channel thermo anemometer composed of a multichannel power supply module SENSOR HT-430 and four thermo anemometer transducers SENSOR HT-428, each equipped with a SENSOR HT-412 (omnidirectional probe sensitive to both air velocity and air temperature) were used. The HT-412 probes meet all requirements of ISO 7726:1998 [38] standard for class C (comfort)-category desirable, i.e., accuracy \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Case** & **Study** & \(\theta\) & **Cooling Mode** & **Time-Sample, \(s\)** \\ \hline \#1 & _Experimental_ & \(25^{\circ}\) & _Nonisothermal_ & 3600 \\ \#2 & _Experimental_ & \(25^{\circ}\) & _Isothermal_ & 360 \\  & _CFD_ & \(25^{\circ}\) & _Isothermal_ & 7500 \\  & _Experimental_ & \(45^{\circ}\) & _Isothermal_ & 300, 2100 \\  & _CFD_ & \(45^{\circ}\) & _Isothermal_ & 7500 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The list of cases considered. Figure 1: (a) Geometry model for Unsteady RANS (URANS), (b,c) room interior photos with four fan coils numbered, (d) photo near a fan coil. better than \(\pm\) (0.02 m/s + 7% of readings) and response time (90%) better than 0.2 s. The thermo anemometers were calibrated for two measurement ranges for better accuracy of the polynomial fit. The first range was between 0.03 m/s and 2.65 m/s, which corresponds to room airflow velocities. The second range was between 2 m/s and 5 m/s, which corresponds to the velocities of fan coil jets. The mean absolute error (MAE) and the normalized mean bias error (NMBE) were calculated for each sensor and both measurement ranges. The maximum sensor MAE was 0.01 m/s for measurement range 1, and 0.03 m/s for measurement range 2. It roughly corresponds to 1% normalized mean absolute error for both ranges. There was a small positive bias for the sensors in range 1 with normalized mean bias error between 0.02% and 0.05%. For range 2, the bias was practically zero with NMBE in the range \(\pm\) 0.002%. The 8 voltage signals (4 proportional to air velocity and 4 proportional to air temperature) generated by the HT-412 probes were simultaneously read and stored on the hard drive of a PC by a data acquisition system manufactured by DATAQ Instruments. This system was composed of a DI-2108-P high-speed DAQ board controlled by the WinDaq recording and playback software. The first measurement set was devoted to the characterization of airflow near the fan coil exhausts. These measurements aimed to evaluate the level of uniformity in the supply flow rates and to get data for inlet boundary conditions to be set in the CFD simulations. All fan coils were set to isothermal recirculation mode with the louver inclination of \(\theta\) = 45\({}^{\circ}\) (case #3 in Table 1, with longer time sample). For each fan coil, the measurements of air velocity and air temperature at the middle points of four supply sections were performed simultaneously. The sensors were placed below the middle point of each opening at the distance of 0.017 m from the surface (Figure 1d). The total measuring period for each fan coil was 35 min (2100 s) long, with the sampling rate of 5 Hz. The results of this measurement set are discussed in Section 3.1. In addition to the local measurements, at the same fan coil operation conditions the measurements of the volume flow rate \(Q\), at each supply section of each fan coil were performed by an ALNOR Balometer. Table 2 summarizes the \(Q\) values. The second set of measurements was devoted to the characterization of the airflow in the room occupied zone.