Educational Heat Transfer Flame

thingiverse

The set of models designed are two flames with an open core with a hole at their top. They are to be printed with filament that changes color with temperature and assembled with a watertight plexiglass covering. A stopper to plug the hole is also included in the design. By filling the models with hot water, the plastic changes color. If the suggested filament is used to print the models, the plastic wall of the model should turn yellow above 45*C. This should happen where the wall is directly in contact with the hot water in the core, and since the heat transfers across the surface, it will be yellow a couple millimeters beyond the core. Just beyond the yellow ring, the filament will turn to an orangey-brown color in the 45*C - 30*C temperature range. At room temperature, the filament is dark green almost black color. The outer thickness of the model will be this color assuming the temperature of the room is below 30*C. The fun flame shape is intended to be eye catching while the color changing capabilities of the plastic serve to grab the attention of a young child and engage them in learning heat transfer. The different thicknesses of the model wall serve to demonstrate how heat transfer can be impacted by wall thickness. Additionally, the design includes a ruler cut-out into the thickness of the wall. This allows the user to measure the distance the heat is transferred. Together, the models are intended to be used as educational tools. They visually demonstrate concepts of heat transfer. On a primary level, the models aid in teaching the rudimentary concept of heat transfer from hot to cold objects, satisfying Kentucky Academic Standard 4-PS3-1. These models can also be used to teach higher level concepts of heat energy and its transfer across a solid surface. The concepts from the governing equation of heat conduction can be demonstrated through use of the models. Heat transfer by conduction is calculated by the following equation. q/A=k ∙(T1-T2) / (X2-X1) Where: q = Rate of heat transfer (W) A = Area (m2) k = Thermal conductivity (W/mK or kgm/Ks3) X2-X1 = Thickness the temperature difference is measured across (m) T1 = Initial temperature at point 1 (K) T2 = Temperature across the thickness at point 2 (K) The model serves to visually demonstrate how the parameters in Equation 1 are intertwined. By studying a single model, students can witness the effect that the initial temperature of the water inside the model has on heat transfer. Specifically, students will see that filling the model with higher temperature water leads to greater thicknesses over which color change occurs. Since the color of the model changes in response to temperature, this visually demonstrates that the greater the initial water temperature, the greater the distance over which thermal heat can be transferred. Further heat conduction concepts are revealed by comparing the thickness over which color changes when both the 30% infill and 100% infill models are filled with water at the same temperature. Experimenting in such a way will reveal how thermal conductivity impacts heat transfer. The difference in infill serves to represent two materials with different thermal conductivities. They give students insight into the purpose of insulation. The 100% infill acts as the insulated model, preventing heat loss by the additional layers of plastic. As seen in Equation 1, if the thermal conductivity is decreased but the rate of heat transfer, surface area and thickness remain the same, the temperature change across an incremental thickness will increase. This is visually taught by pairing the model to a lesson on heat transfer, satisfying the middle school level Kentucky Academic Standard 07-PS3-3. For high level learners, the equation itself can be applied to the model to calculate the models’ heat transfer parameters. As mentioned above, the ruler cut into the side of the model serves to measure the thickness of the model. Using the ruler paired with the known color to temperature correlation, an average q/Ak can be calculated. This term can then be used to back calculate the thickness at which a certain temperature exhists. If additional study is desired, it may be beneficial to note the surface area of the flame walls is 3708.42 mm2 and the thermal conductivity of PLA is known to be 0.12 W/m*K.