| 7 | Heating glycol in well insulated container |
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| Main | Glycol is heated electrically in an almost perfectly insulated container. The temperature of the liquid is monitored, and the power of the electric heater is measured. More…
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| Description | DESCRIPTION OF EXPERIMENT |
| Experiment | Glycol is heated electrically in an almost perfectly insulated container. The temperature of the liquid is monitored, and the power of the electric heater is measured. The power of the electric heater is kept constant and the liquid is stiired very gently to ensure homogeneous conditions. The lid of the container is insulated with a thick layer of cotton. The tank is made of a material that stores very little entropy.
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| Dimensions | Mass of glycol: 1398 g Power of electric heater: 302 W Ambient temperature: 23°C |
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| Assignment | A POSSIBLE PATH THROUGH THE INVESTIGATION… |
| Basics | Investigate the experiment, make sure you understand the setup of the system and the initial conditions. Plot the data to get a feeling for the process. Create a word model for the system and its processes.
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Particulars | Create Ts (temperature – specific entropy) and sT diagrams for the experiment from the experimental results. Use the Ts diagram and graphically determine the warming factor, the specific entropy capacitance and the specific heat c = T·k for temperatures 20°C, 40°C… up to 120°C. Show that the specific heat increases (nearly) linearly with temperature (c = aT + b). Create a dynamical model based on the entropy representation. Repeat this using the energy representation which uses the function c = aT + b to simulate the heating of glycol in a perfectly insulated container. |
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| Model | MODEL EQUATIONS AND MORE… |
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| Questions | SOME SIMPLE QUESTIONS… |
| 1 | What is the specific temperature coefficient of energy (specific heat) of a body? What is the relation between the (specific) entropy capacitance and the (specific) temperature coefficient of energy of a body? |
2 | Are specific heats of bodies constant in general? Is the specific heat of water constant? Is it constant for glycol? |
3 | What function of temperature is the entropy capacitance of a body whose specific heat is constant?
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4 | If a material has a constant entropy capacitance, what function of temperature is its specific heat (i.e. the temperature coefficient of energy)?
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5 | What is the meaning of the area between the function and the temperature axis in an entropy capacitance – temperature diagram (Kapa–T diagram)?
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6 | What is the meaning of the area between the function and the temperature axis in a temperature coefficient of energy versus temperature diagram (C–T diagram)? |
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