An Inductive Approach To Teaching Heat And Mass Transfer

This paper presents a method to teach heat and mass transfer courses that will appeal to the inductive learner. A deductive learner prefers to proceed from general to specific, while an inductive learner prefers to proceed from specific to general. Studies have shown that induction promotes deeper learning and results in longer retention of the information to students. Induction, in many cases, is also the method in which the original material was discovered! This style of teaching is relatively rare in engineering courses and is almost non-existent in textbooks. Instructors can teach inductively by presenting familiar phenomena, practical issues, or experimental observations before presenting a general principle. Surprisingly, most textbooks still use an exclusively deductive approach, proceeding from first principles and governing equations to specific applications. Since there are relatively few textbooks that are written using an inductive approach; this makes implementation of the inductive method a challenge. Another challenge is that students typically will not have a wide range of experience or intuition needed to begin the inductive process. A simple laboratory experiment or demonstration will provide the foundation (observations or data) from which the inductive process is initiated. We have integrated inductive learning into our coverage of heat transfer and mass transfer. In heat transfer, for example, simple heat exchanger design is the first topic addressed in the course. Discussion of the significance of the overall heat transfer coefficient provides a meaningful framework for introduction of topics such as conduction and convection, which are introduced later in the course. In mass transfer, presented in the context of a transport phenomena course, students start with the design of a gas absorption tower. They are shown both laboratory equipment and pictures of industrial towers used to remove an impurity from a gas stream. If possible, they perform experiments on a laboratory gas absorption tower and observe the gas and liquid flowing Page 593.1 over the packing material and measure inlet and outlet gas concentrations. Next, they use a simple model of the tower with a constant overall transfer unit height. The students then proceed to learn about the overall mass transfer coefficients, individual phase coefficients, and the film theory of mass transfer. This portion of the material ends with an experiment in diffusion, Fick’s law of diffusion and the measurement and prediction of a diffusion coefficient. We believe that presenting course material in this order establishes the industrial importance of the equipment and gives a reason for why the student needs to learn the material. The student starts with simple concepts that are easily grasped; a liquid stream is heated from a second stream and a sulfur dioxide in a gas stream is removed by using a liquid stream. The learning then examines how the process works by looking inside the equipment and seeing why heat and mass are transported. The learning culminates with the presentation of fundamental continuum concepts of convection, conduction and diffusion. Inductive Learning and Teaching Styles Deductive teaching begins with rules or principles and then proceeds to deduce consequences or resulting phenomena. This is the natural teaching style in higher education, particularly in mathematics and engineering courses. Using a deductive teaching style, a professor can cover a large quantity of material in a short amount of time simply by lecturing and presenting derivations. Most topics in engineering courses are approached deductively; most courses are arranged in a deductive structure, and most curricula are organized to utilize a deductive order of courses. Induction is the more natural learning style in which the learners explore observations and then infer the governing principles from them. Children learn by observation, not by deriving outcomes by beginning with first principles. Once familiar with an outcome or phenomenon, a child’s natural curiosity will lead him or her to ask for an explanation. The Scientific method also begins with induction when a scientist formulates generalizations that explain experimental observations. Those generalizations can then be extended and applied to other situations to deduce outcomes or describe phenomena. The concepts of inductive learning and deductive learning are illustrated in Figure 1. Figure 1. Deductive learning is begins with principles, and inductive learning begins with observations (Adapted from Felder et al. ). Observations, Data General Principle or Theorem IN D U C T IO N IN D U C T IO N D E D U C T IO N