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主页 旧刊 有关人员 未来大会 American Society of Thermal and Fluids Engineering

ISSN 在线: 2379-1748

ISBN 打印: 978-1-56700-517-2 (Flash drive)

5-6th Thermal and Fluids Engineering Conference (TFEC)
May, 26–28, 2021 , Virtual

ENHANCING STUDENTS LEARNING IN THEMAL-FLUID SCIENCES COURSES THROUGH DAILY LIFE EXAMPLES

Get access pages 1345-1348
DOI: 10.1615/TFEC2021.edu.032230

摘要

Many Engineering Technology students at Penn State Erie, The Behrend College tend to struggle with some of the basic concepts in courses of thermal-fluid sciences, which are Thermodynamics, Heat Transfer, Fluid Power and Energy Conservation Systems. This challenge occurs globally according to many researchers [1-4]. Courses in thermal-fluid sciences are difficult to understand and students tend to develop significant misconception about these courses [5]. One reason for this issue is the characteristics of the thermal-fluid sciences. Velocity is a concept that is easy to understand because in their daily life people see lots of moving objects and experience the feeling of movement personally. In thermal-fluid sciences, there are lots of concepts that are unobservable, such as pressure, heat transfer, enthalpy etc. Students learn when they connect new information to existing understanding. However, usually students lack personally experience of these concepts, which makes learning of these concepts very challenging. Daily life examples are easier for students to understand comparing to industry applications because students are not familiar with industry applications. Daily life examples are emphasized in teaching thermal-fluid sciences courses to enhance students learning.
Pressure of fluid is the most important concept in fluid power course for mechanical engineering technology students. One important concept is the pressure at the bottom of a liquid column, which is equal to the specific weight of the liquid multiplied by the height of the liquid column. This equation is very simple, however students can make mistakes when they solve the manometer problems. Part of the reason is that they do not understand that the deeper they go underwater the higher the pressure becomes, which is obvious to divers. However, not lots of students have diving experience. A movie clip of a submarine going deeper is shown in class. The crackling noise and bolts flying out of the wall, which are caused by the high pressure at deep water, make this concept very easy for students to understand.
Another important concept which is very difficult for students to understand is that the pressure of the fluid when the fluid is moving is different than the pressure of fluid at rest. Previously an exercise has been proposed with apparatus to be made [6]. Then the author realized the coffee urn is very similar to the proposed apparatus. Pressure of Water in a Coffee Urn lab is designed to illustrate the Bernoulli equation which is the most used and most abused equation in fluid mechanics. The lab includes Pre-Exercise Worksheet and Post-Exercise Worksheet and is shown in the appendix. Students first complete the Pre-Exercise Worksheet to make predictions about outcomes based on their past experiences, pre-conceived notions and possible previous coursework. Students then download picture of coffee urn with nozzle at the off position and video of water flowing out of the nozzle. Then students complete Post-Exercise Worksheet.
Volumetric flow rate is widely used in Fluid Power. In a channel, the average fluid velocity multiplied by the cross-section area is equal to the volumetric flow rate. Blowing candles at a birthday party can be used to demonstrate this relation. When blowing candles, people need to keep the mouth opening minimum to achieve very high air velocity. The problem is listed below.
Vital capacity is the volume of air breathed out after the deepest inhalation. For average male the vital capacity is 4.6 liters. Assume the exhalation time is 5 s. Calculate the average volumetric flow rate. Assume the opening of the mouth is half circle with a diameter of 7 mm. Calculate the average velocity of the air leaving the mouth.
To illustrates the temperature and pressure dependence during phase change processes, the author designed a problem which involves cooking a potato in boiling water on a high mountain. The saturation temperature decreases with the pressure. The problem is listed below. Pressure cooker is another good daily life example for this principle.
A climber to Mount Denali, previously called Mount McKinley, set up a fire to boil some water in a Dutch oven. Several potatoes are added in the boiling water and cooked for half hour. The atmosphere pressure at that high altitude is 50 kPa. Can the potato be cooked? What is the boiling water temperature at that pressure?
Rate of heat transfer is a difficult concept for students to understand. Students are asked about what to wear when they stay outside during cold wintertime. Common answers include coats, jackets, hats and gloves. Thanks to the snowy weather here they all know that not dressed properly can cause injuries from frostbite and even hypothermia. Then the instructor explains the reason of this phenomena which involves rate of heat transfer, winter clothes reduce the rate of heat loss. Obviously, there are lots of industry examples of rate of heat transfer such as steel blocks in the quenching tank and electric heater in the water heater. Students are more familiar with daily life examples than industry applications which makes daily life examples more effective for introduction of a new concept.
All the daily life examples motivate the students since they realize that the principles they are studying are applied in daily life. Building the connections between dry abstract sciences with familiar daily life also make the students more confident to learn the subject.
Video presentation
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