Shape Memory Alloy Heat Engine

Using SMA Materials to demonstrate the Second Law of Thermodynamics.

 

Part A.

 

Introduction

 

Brief introduction on SMA materials.

Part B.

 

Supplies

 

Trained SMA wire

Meter Stick

Temporary Support Member

Clamp

Power Supply

Voltmeter

Stop Watch (or Timer)

Heat Gun

 

Fig. 1

 

Fig. 2

 

                                                                   

 

Setup

 

Connect the SMA Wire to the temporary support member. Connect the power supply to the wire by attaching the positive and negative output wires to the opposite ends of the wire. Attach the voltmeter to the wire by attaching the negative lead near the negative output lead from the power supply. Attach the positive voltmeter lead near the positive lead from the power supply as shown in Fig.1.  Load the wire with the 453 g (1 lb) weight. At this time the wire should deform from the load. Set the power supply such that the voltage is the manipulated variable.

 

 

Part C.

 

Preliminary Experiment

 

1. Measure the initial height in cm of the bottom of the weight.

 

Initial Height (cm): ______________

 

 

2. Use the heat gun to heat the wire until the wire no longer visibly contracts.

 

 

3. Measure the finial height in cm of the bottom of the weight.

 

Final Height (cm): ______________

 

4. Compare the components of this experiment to the following diagram.

 

 

What part of the experiment acts as the Hot reservoir?

 

What work does the system do?

 

What part of the experiment acts as the Cold reservoir?

 

 

 

Part D.

 

Experiment Procedure

*Read through entire step before beginning each step.

 

In this part of the experiment you will be figuring out the efficiency of the system. To do this you must be able to accurately represent the Win and the Wout. In order to accurately represent the work going into the system (Win ) you will heat the wire using resistance heating. This is done by passing an electronic current through the wire. By reading the voltage and current from a multimeter (or the power source) you will be able to calculate the power going into the system. The power can then be integrated to find the Win . The work done by the system (Wout = WSMA ) can be calculated by determining the displacement of the weight.

 

1. Measure the initial height in cm of the bottom of the weight.

 

Initial Height (t = 0 sec): ______________

 

 

2. Turn on the power supply and adjust the voltage until the voltmeter reads 0.8 V. Notice that the wire has begun to change its shape to return to its trained spring shape. After 10 seconds record the height of the weight. After 10 more seconds measure the height of the weight again. Continue this process until the wire no longer visibly changes its shape. Record the measurements below.

 

 

Time (seconds)

Height (cm)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3. Measure the current of the circuit by reading the power supply.

 

Current (Amps):           ______________

 

4. Turn off the power supply. What happens to the wire as it cools?

 

 

 

5. Once the wire has cooled to approximately room temperature it should be elongated due to the weight of the load still attached to it. Measure the final height of the weight.

 

Height (cm):                  ______________

 

 

Part E.

 

Equations

 

 

Calculations

 (for Part D.)

 

 

  1. Calculate the work going into the wire from the power supply for steps 2 & 3 f the experiment.

 

 

 

 

 

 

  1. Calculate the work done by the SMA wire from step 2 of the experiment.

 

 

 

 

 

 

 

 

  1. Calculate the efficiency of the system from steps 2 & 3 of the experiment.