The Blender Experiment

Apparatus

The apparatus consists of a kitchen blender, thermocouple probes mounted on a support frame, a data acquisition system, and a computer to record the data captured by the data acquisition system.

The thermocouple support frame is constructed from acrylic, pine board and four chop sticks. The frame provides a rigid support for four thermocouples that are equally spaced by 2.5 cm in a horizontal row approximately 1.5 cm above the tip of the blades in the blender.

The data acquisition system is a NI USB-9211A device from National Instruments that can read up to four thermocouples. The DAQ device is controlled by a LabVIEW program running on the computer. The program collects the temperature readings, plots the temperature values in a strip chart, and stores the data for later analysis.

In-class Demonstration

The in-class demonstration takes 15 minutes, including the time to introduce the project, fill out the worksheets, and run the experiment.

We begin with a brief introduction to the EET project and then describe of the experimental apparatus. Students are asked to complete a one page worksheet that solicits their prediction of what will happen when the blender motor is turned on. Specifically we ask them to predict whether the temperature of the thermocouples will increase, decrease, or stay the same. Other questions on the worksheet ask the students to provide some justification for their prediction, and to identify the source of their knowledge on how the blender will perform.

Lab Exercise

The laboratory exercise takes about one and a half hours. The purpose of the lab exercise is to give students a guided-inquiry learning experience that complements the conventional lecture for the class. At this point in our research, the lab exercise is voluntary and does not count toward the student's grade in the course.

You can download the lab manual. It is especially helpful if you review the first four pages (sections 1 through 3) before coming to the lab.

Learning Objectives

As a result of completing this exercise, students will be able to...

1. Recognize and describe the roles of heat, work, and energy storage in the operation of a food blender.
2. Identify and qualitatively describe the relationship between terms in the first law of thermodynamics as manifest in the operation of the blender.
3. Use qualitative reasoning to predict and verify the response of measurable system parameters (temperature, power input) that result from changing blender speed, quantity of liquid in the blender, and the initial temperature of liquid in the blender.