A Computer-Based Simulation for Teaching Heat Transfer across a Woody Stem

Abstract

To assist student understanding of heat transfer through woody stems, we developed an instructional package that included an Excel-based, one-dimensional simulation model and a companion instructional worksheet. Guiding undergraduate botany students to applying principles of thermodynamics to plants in nature is fraught with two main obstacles: (1) students have a limited knowledge of heat transfer fundamentals, and (2) the highly complex and cognitively demanding analysis of the plant thermal environment. To provide the necessary background, reduce the complexity, and allow students to process information in a step-wise fashion, the computer simulation permits students to vary heat transfer properties for the bark and xylem, along with lateral stem dimensions, to visualize the resulting diurnal transient radial temperature distribution throughout the stem. Additionally, the maximum cambial temperature excursion could be visualized, along with the phase difference between the cambial temperature and the outer bark temperature at any time. A paper-based instructional worksheet guides students through a series of questions and leads them through the learning process. They acquire basic concepts of heat transfer and apply their observations to ecophysiological conditions such as heat stress on saplings, the insulative value of bark, and the impact of fire on the cambium. Anecdotal evidence indicated that the computer simulation proved to be a valuable tool for students because it reinforced woody stem structure and placed it into context of a tree's physiological response to temperature.