Determination of Heat Capacity Ratio, isothermal expansion, thermodynamics, adiabatic process, open systems, closed systems, isolated systems
Objective for experiment 1:
To determine the heat capacity ratio of air by following a modernised version of the experiment attributed to Shoemaker. The experiment is to determine the heat capacity ratio of air, by emulating an adiabatic expansion of air.
Objective for experiment 2:
The objective is to calculate the volume ratio of two vessels for air. This calculated by using an isothermal expansion.
[...] The difference between and adiabatic and an isothermal is that an adiabatic doesn't necessarily mean the temperature of the system is constant but there is no heat exchange occurring. In Thermodynamics, there are three different types of systems; open systems, closed systems and isolated systems. An open system is one that will exchange both energy and matter with the surroundings, however with a closed system it will not exchange matter only energy. Alternatively, an isolated system will not exchange energy and matter with the surroundings. If a thermo-bottle had perfect insulation is would be considered a fully isolated system as there is no exchange in matter or heat. [...]
[...] Method for experiment 1 To determine the Heat Capacity Ratio of air we used a barometer the apparatus shown in figure Expansion Processes of a Perfect Gas Apparatus, Armfield Limited'. Using the barometer the first step was to measure the atmospheric pressure. The next step was to close the ball valves V1 and V3 then open V4. V1 allows air to exit the vessel to the surroundings once it has been pressurised where as V3 allows air to enter a vessel once a vacuum has been formed in the vessel. [...]
[...] Alternatively, to further improve the accuracy, the pressure Pi could have been obtained by reading off the data logger instead, giving the pressure at instantaneously. Unless an automatic method of opening and closing the valve the experiment could have only given results that are more reliable by repeating the experiment. Method for experiment 2 Before carrying out the experiment both vessels needed to be at atmospheric pressure and this was achieved by opening valves V1 and V3 whilst keeping the other valves closed; the atmospheric pressure was measured using a barometer. [...]
[...] Small factors, for example the minute change in temperatures of each vessel contribute to less accurate results as both temperatures needed to be the same. Furthermore, valve V5 may not have been adjusted correctly; this may have caused the airflow to be slightly too fast causing a change in the temperatures of both vessels effecting the results. Other external environmental factors also may have affected the pressure and temperature of the system. Finally, to improve the experiment for more accurate results a data logger can be used to help prevent human error and repeating the experiment would have helped attain more reproducible results. [...]
[...] A process is considered adiabatic if there is no or very little heat transfer. By opening V1 rapidly, it caused air to escape in a short period causing a high rate of expansion. Due to the rate of expansion, occurring so quickly the heat transfer would not have occurred in time. Furthermore, we recorded the instantaneous value of the pressure Pi after opening and closing valve V1 quickly. By taking Pi immediately after, the value had not been affected by heat transfer meaning that the initial expansion could be considered adiabatic. [...]
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