Methodology for the Evaluation of Natural Ventilation in ... - Cham

had a dedicated supply and return fan with a variable-speed drive incorporated into the controlscheme for each. A computer software package allowed for a more refined control over theHVAC system. The computer interface, shown in Figure 36, allowed the operator to controlvarious system set points, including supply airflow rates, temperature, and relative humidity. Thecontrol system also allowed recording for all data points in the control system at a time intervalspecified by the operator. The supply air temperature and the supply fan airflow were adjustedduring experiments to have the test chamber positively pressurized so that warmer air from thespace surrounding the test chamber was not drawn into the test chamber itself. The set pointsused for the experiments are presented in Table 22.Table 22. Test Chamber HVAC System Set PointsVariableSet PointSupply Flowrate165 l/s (350 CFM)Supply Fan Variable Frequency Drive 97.5%Return Fan Variable Frequency Drive 95.5%Supply Air Temperature6°C (±2°C)Figure 36. Test Chamber HVAC Computer Interface Control PanelA separate computer controlled and recorded data from a Campbell Scientific CR10X dataacquisition system. The CR10X was outfitted with two sets of ports having a total of 50monitoring locations available. These locations were equipped with Type K thermocouple wiresthat had been painted with silver paint to reduce any error in measurement due to radiation. AnRS-232 cable connected these locations to the desktop computer. The computer softwarepackage, TComm®, was used to monitor and record data from the CR10X data acquisitionsystem. The CR10X was used for long-term data recording at minute intervals, as long as thedata logger was turned on and connected to the computer. The setup file for the CR10X dataacquisition system is provided in Appendix A. A second, more portable, data acquisition systemmonitored additional temperature locations throughout the model. The Keithley® 2700 had a103