Lab 6: Thermoelectric Cooler, Otto Heat Engine, and Carnot Engine Cycle

Today we started the day with a thermoelectric cooler. First Professor Mason, put one side of the metal in cold water, and the other side in hot water. As a result, the cooler spins counter-clockwise. Then by reverting the hot and cold water, the cooler spins clockwise.

Here is the thermoelectric cooler spinning counter-clockwise.

 Then we attached a power supply to it, allowing the cooler to rotate, and also proving the thermoelectric effect, in which one side of the metal will be hot while the other becomes cold.

 This is our prediction of the experiment above.

 We found the molar heat capacity at constant volume by using the first law of thermodynamics at constant volume, where the change in internal energy of the gas is the same as the energy transferred to it. E = Q. And we relate that equation to Q = CVnT. We found that CV is (3/2)R.

 With CV we were able to find CP, the molar heat capacity at constant pressure by using the formula
CP = CV + 1. We found that CP is (5/2)R.

 Using the ideal gas law, PV = nRT, and replacing R for CP - CV. We were able to find an equation relating the number of moles and the temperature.

 These are further calculations to show the relationship between the ratio of pressure as a function of the ration in volume. This calculations only apply to Adiabatic expansions.

 More calculations regarding the initial temperature and volume as function of the final temperature and volume.

 We derived the work done in Adiabatic expansions as function of pressure, volume and gamma.

 This is a working example to find the work by using the derived formula above.

This is a working example about the Carnot Engine cycle. The system undergoes Isothermal expansion from a to b and from c to d, and it goes Adiabatic expansion from b to c and from d to a. Using the given values. we found all change of energy first. For adiabatic process, we let the heat energy be 0. And then solve for work using the first law of thermodynamics. For isothermal process, we found the work from, W = nRTln(V2/V1).  Then solved for Q using the first law.

 This machine is also known as the Viertakt Ottomotor, and it operates at four stroke engine cycle. Intake stroke, compression stroke, power stroke, and exhaust stroke. First, the machine intakes fuel, then compressed, then ignited as the piston moves down, then the piston goes up pushing heat out to get a mixture of exhaust and unburnt gas. The main purpose of this engine is to burn as much of the gas as you can in order to avoid pushing out unburnt gas.

 This video shows the cycle by which the Ottomotor operates. 

It is possible to increase the power output of the engine, by increasing the revolutions per second, increasing the volume, and increasing the pressure.