This study has proposed a simple method to show the convective heat transfer. The object in this study is an air conditioner (AC) as a simple case of convection. In addition, AC is also easy to find in the class because most classrooms in Indonesia installed AC. Usually, a visualization needs special software (i.e. MatLab or others) and good programming skills. Therefore, in some cases, a lecturer would have difficulty enhancing the students' understanding of the topic because it needs a simulation or visualization to explain it. Therefore, we present an alternative way to help the lecturer prepare materials for the learning process. The visualization was processed using Microsoft excel. So, it would be easy to operate and implement in the classroom. The result shows that the visualization convective heat transfer and the temperature change in the room seem to correspond to each other. The process AC does heat transfer is centred in a particular area as the coldest position. The lowest temperature is 20.90 °C with the decay constant 0.040, appropriate to the exponential decay in Newton's law. Moreover, the decay constant (k) could not be used to predict the distance from the AC in temperature change.