The Data and Models project at the Concord Consortium is developing innovative probeware running on powerful wireless handheld computer systems that support student explorations into various forms of heat energy transfer.

In order to best support deeper personal ownership of the methods of experimentation, analysis and visualization, we gave every student in the study access to a wireless color handheld computer system: the Compaq H3600 series iPAQ Pocket PC. We selected the iPaq over several other options because it combined a fast 206 MHz processor, 32 MB of memory, a color screen, an excellent battery system, and 802.11b wireless Ethernet capability. In January 2001 an iPAQ Pocket PC outfitted with a PCMCIA jacket and wireless Ethernet card costs about $750; however, within two years we expect to see similar systems marketed for educational use selling for under $300. While an iPaq is small enough to easily fit in a hand, it has enough processing power, memory, and display capacity to easily function as a personal computer for a student. Systems like the iPAQ can easily function as a simple web browsing system, email center, advanced graphing calculator, student information manager, probeware system and by attaching a keyboard they can even be used for extended writing. Adding wireless networking not only allows portable access to web and email services, it also supports extended collaborative access to probeware systems such as the Concord Consortium's new Data and Models Thermal Conductivity System.

Starting from research on student misconceptions regarding heat and temperature (see article, page 6), we have first created a system we call "blockmodel" to explore thermal conductivity and temperature gradients in different materials. The heart of our system for exploring thermal conductivity is a set of small aluminum, stainless steel and nylon blocks with an embedded network of temperature sensors.

The blocks can be arranged in arbitrary two-dimensional patterns and heat can be pumped either into or out of any point of the thermal network of blocks using a Peltier-based thermal actuator we designed. The temperature of sensors embedded in the blocks is transmitted over a wireless Ethernet and displayed simultaneously on multiple iPaq handheld computers.

Because the blocks can be rearranged easily, many simple configurations involving topology and material can be investigated quickly. For example, students are often puzzled when asked "does heat flow around a corner as easily as it does in a straight line?" It is very simple to set up a test with the blockmodel system. Later issues of both thermal conductivity and specific heat come into play when comparing temperature gradients using different block materials. In addition to measurement, visualization, and analysis of real physical systems, the software enables students to use simulations to construct and evaluate simple thermodynamic systems.

Going beyond our work on conductivity, we are working on an ultra-fast response temperature probe. While most computer-based temperature probes take over five minutes to settle to near equilibrium in still air, our new probe responds in seconds with a temperature resolution of better than 0.05oC. This ultra-fast response allows a tremendous range of interesting investigations.

We believe it is important for students to understand how the mass of a finger and the nerve cells near the surface of their skin respond when touching objects at different temperatures. A finger is the first temperature probe that everyone uses. A classic misconception is that metal objects are colder than plastic objects. The ultra-fast probe can in seconds measure the actual surface temperature of the metal and plastic objects and determine that they are the same. However, the experiments become much more interesting when the temperature of the surface of the skin is measured both before and after touching metal and plastic objects. If this is done with different fingers students discover that the surface of the finger that touched metal cooled more than the finger that touched plastic. We hope that by using their previous learning about temperature gradients and heat flow through materials of different conductivities and specific heats, along with a simulation of finger thermodynamics, students will break through the misconception and achieve a deeper understanding of their body as a sensor.

We also plan to use the ultra-fast probe for investigations of radiant heat flow. We experimented with the initial prototype by turning on an incandescent desk lamp and directing it horizontally at the sensor placed about 18" away. While the hand holding the sensor could feel the heat of the lamp the shiny surface of the sensor reflected most of the radiant energy coming from the lamp and did not heat up. However, when placing the sensor one millimeter above the back cover of a book and illuminating both with the lamp, the temperature of the air next to the surface of the book immediately rose. Moving the book away caused the sensor to immediately drop to the local air temperature. This experiment became even more interesting when we turned the lamp off, aimed it at the book and sensor and watched the air at the surface of the book immediately rise in temperature again because of the infrared radiation coming from the hot bulb and lamp housing. In effect we created a primitive thermopile.

An ultra-fast response probe can also be used for measuring the small and often ephemeral temperature differences associated with convective flow. The probe is sensitive enough to measure the temperature fluctuations of convective bubbles of warmed air three inches above the surface of a hand.

Developing student intuition to provide a context for interpreting results like this will be greatly enhanced by model-based visualization of convective flow.

Stephen Bannasch is the CC director of technology
stephen@concord.org

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Last Updated: April 21, 2001
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