Design of Experiment to Evaluate Thermal Resistance of a PTAC Unit

As a part of the “Design of Experiment” component of Thermal/Fluids Laboratory (MECH405) at Manhattan College, a setup for measuring the R-value of an Evergreen Products Model KHS-09 PTAC unit was designed by a student group. The setup consisted of the PTAC unit installed in a well insulated wall. A thermally controlled hot chamber (which simulated a hot outdoor environment) was built around the exterior side of the wall and PTAC assembly. The interior side was exposed to the lab air temperature (typically at 70°F). Thermocouples were installed on various surfaces of the setup and temperature history data were collected in order to calculate the R-value of the PTAC under different imposed temperature gradients and convection heat transfer environments. ANOVA analysis of the data showed that the R-value of the PTAC was influenced by the convective environment (free versus forced convection), and while outdoor temperature did not directly influence the R-value, an interaction existed between temperature and convection.