Introduction For the purpose of studying combined radiation and free convection heat transfer, this experiment measured the surface temperature of two aluminum flat plates during heat-up. Both plates' lower surfaces were well insulated. For comparison, one plate was considered to be ideal blackbody, which is a perfect absorber and emits; the other one was polished, yielding different radiant properties. According to the procedure, both plates were heated under the lamp from room temperature; plates' temperature was measured with a thermocouple and recorded with LabView Program. To analyze the results, appropriate assumptions were made and correct conservations of energy were chosen.
Results and Discussion Based on the data collected in the experiment, Temperature vs Time were plotted for both plates, as shown in figure 1 and figure 3. Our plates were exposed under the lamp for a longer time than claimed in the procedure to reach a relatively steady state, because the lamp we were using was weaker than normal ones. Figure 1, Temperature vs Time for Blackbody Plate
Energy terms in the energy balance equation were also calculated and plotted as shown in figure 3 and figure 4. Equations that used to do all the calculations can be found in Appendix A and Appendix B. All the calculations were done using Microsoft Excel.

Figure 2, Energy terms vs Time for Blackbody Plate Irradiation, Gtot was calculated to be 1456.95 W/m2. Since the initial temperature of plate surface was measured to be 23.5C, and we assumed G stay constant, so G for Polished plate is the same as G for Blackbody plate. With the Gtot being 1456, α was calculated to be 0.22. All the calculations can be found in Appendix I. Thus, as we can see in the plots, αG is a straight line.

Figure 3, Temperature vs Time for Polished Plate

Figure 4, Energy terms vs Time for Polished Plate