3/12 week 3 day 2 Different Heat Engines and Cycles again.

The purpose of this lab was to analyze the different types of heat engines including the carnot engine cycle and determine how to maximize the efficiency of the engine based on how the engines work. We will use the pV diagram in order to consider its four main elements in a high efficiency heat engine cycle. 

at the beginning of the class, we did an experiment that shows in these two picture. we prepare two cups of water, one is hot water, the other is ice water. then we put the equipment into the two cups, we find it rotating. 

Then we reverse the hot and ice water, we find that the rotation is also reversed. 

then we attach a power supply to the leads, we find that one side gets hot and the other side gets cold.

in this photo, we first use the equation:△E=C_v*n*△T and △E=3/2*n*R*△T, and combine them we find that C_v=(3/2)*R. then we know that △E=Q-W= Q-P△V and Q=n*C_p*△T and P*△V=n*R*△T and find C_p=(5/2)R.

in the second and third photos, we calculate the questions in the first photo.  in the last photo, we use the equations that we find in the second and third photos to find the relationship of △P and P.

in the second photo, we integral both side of the equation and find the equation about P_final, P_initial, V_final and V_initial and the equation:T_f*V_f^(y)=T_i*T_i^(y). In the third photo, we prove the equation:T_f*V_f^(y-1)=T_i*T_i^(y-1).

in these photos, we begin to figure out the work in an adiabatic expansion. and we prove the equation in the second photo. Then in the third photo, we use the equation we find in the second photo to find that the work done is 1246J.

We start to talk about the Carnot Engine Cycle. There are four expansion in the photo. They are Isothermal expansion A-B, Adiabatic Expansion B-C, Isothermal Compression C-D and Adiabatic Compression D-A. we use the equation W=nRTln(V_f/V_i) to find the work and the equation △E=(3/2)nRT to find the internal energy and the equation △E=Q-W to find heat energy Q.  Then we use the data we calculated to find the W_net =950 and Q_H is 2739 and Q_C is -1822 and find e(efficiency)=W/Q_H=0.35

in this photo, if we want to increase the efficiency of car engine, we should cool the radiator and use hot engine.

in these photos, the professor introduces us the Otto Cycle.

in this photo, we have three ways to increase the power of engine:1. increase the revolution, it is also called rpm. 2. increase the volume that the engine has the larger space to work. 3. increase the maximum pressure that makes the engine works harder. 

Conclusion:

Today in class, we didi thermoelectric cooler and Otto cycle experiments. For thermoelectric cooler lab, we should reverse the hot and cold water, then the fan will also reverse. Tf we want to increase the engine power, we need increase revolutions, volume and maximum pressure for the Otto cycle,  Also, for the Carnot cycle engine problem, we know the each different expansions and compressionsinternal energy and heat energy.