Name: heat transfer calculations with conduction, convection
Uploaded: 2023-09-18T17:11:17.000Z
Duration: 1 min 20 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Physical Science

Energy

PS.PSc.7.1

conduction-convection-and-radiation-problem-solving

Conduction, Convection and Radiation: Problem Solving

קיר בעובי 13 ס"מ עם שטחשל 100 מ"ר ומוליכות תרמית של 1.5 וואט/מ"ק מפריד בין החדר לאטמוספירה החיצונית, שנמצאת ב-3 מעלות צלזיוס.
המשטח החיצוני של הקיר הוא 10 מעלות צלזיוס, והפליטות שלו היא 0.8. אם מקדם העברת החום הקונבקטיבי הוא 15 W/m2K , מצא את קצב איבוד החום הכולל לסביבה. כמו כן, לחשב את הטמפרטורה של המשטח הפנימי של הקיר.
כאן, כל שלושת מנגנוני העברת החום מעורבים. חום מועבר מהמשטח הפנימי לחיצוני של הקיר באמצעות הולכה, בעוד שאיבוד חום לסביבה מתרחש עקב הסעה וקרינה.
קצב איבוד החום באמצעות הסעה תלוי בשיפוע הטמפרטורה, שטח הפנים ומקדם העברת החום.
לכן, אובדן חום כולל לסביבה עקב הסעה וקרינה ניתן לחשב כמו 13.27 x 103 W.
באמצעות שימור אנרגיה והחלפת המונחים במשוואת החום, ניתן לחשב את הטמפרטורה של המשטח הפנימי של הקיר.

<ol>
	<li>OpenStax. (2019). פיזיקה אוניברסיטאית כרך 2. [גרסת אינטרנט]. מקור: <a href="https://openstax.org/books/university-physics-volume-2/pages/1-6-mechanisms-of-heat-transfer">https://openstax.org/books/university-physics-volume-2/pages/1-6-mechanisms-of-heat-transfer</a></li>
</ol>

הולכה, הסעה וקרינה: פתרון בעיות

<div style="direction:rtl">ישנן שלוש שיטות שבהן ניתן להתרחש העברת חום: הולכה, הסעה וקרינה. לכל שיטה יש מאפיינים ייחודיים ומעניינים, אבל לשלושתם שני דברים משותפים: הם מעבירים חום רק בגלל הפרש טמפרטורה; וככל שהפרש הטמפרטורה גדול יותר, כך העברת החום מהירה יותר. כדי לפתור בעיה הקשורה להעברת חום, ראשית יש לבחון את המצב לקביעת סוג העברת החום. זה יכול להיות הולכה, הסעה, קרינה או שלושתם. השלב השני הוא לזהות ולרשום את הכמויות הלא ידועות בבעיה. ניתן להכין רשימה של מה שניתן או מה ניתן להסיק מהבעיה כאמור, כלומר, הכמויות הידועות, ולאחר מכן לפתור את המשוואה המתאימה לכמות שתיקבע. עבור העברת חום דרך הולכה, יש להשתמש במשוואה הבאה. <img alt="Equation1" src="/files/ftp_upload/14166/14166_Equation_1.svg" style="text-align: center; height: 46px;"> עבור הסעה, קצב איבוד החום תלוי בשיפוע הטמפרטורה, שטח הפנים ומקדם העברת החום. <img alt="Equation2" src="/files/ftp_upload/14166/14166_Equation_2.svg" style="text-align: center; height: 18px;"> המשוואה הבאה נותנת את קצב העברת החום נטו עבור קרינה. <img alt="Equation3" src="/files/ftp_upload/14166/14166_Equation_3.svg" style="text-align: center; height: 25px;"> החלפת הכמויות הידועות יחד עם היחידות שלהן במשוואה המתאימה ופתורה מספרית נותן את הפתרון הנכון.</div>

ישנן שלוש שיטות שבהן העברת חום יכולה להתרחש: הולכה, הסעה וקרינה. לכל שיטה יש ייחודי ומעניין...

Education

JoVE Core

Physics

פיזיקה

Unit 1

יחידה 1

Temperature and Heat

טמפרטורה וחום

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

heat transfer calculations with conduction, convection

Heat transfer calculations with conduction and convection use the temperature difference to find the rate of heat flow. Radiation can also be part of the process. The main idea is that heat moves only because one area is hotter than another, and a larger temperature difference leads to faster transfer.

To solve a heat transfer problem, first identify the type of transfer involved. It may be conduction, convection, radiation, or a combination of all three. Next, write down the unknown quantities and sort the given information from the problem statement.

After the known values are listed, choose the correct equation for the type of heat transfer. Use the conduction equation for heat flow through materials. For convection, the rate of heat loss depends on the temperature gradient, the surface area, and the heat transfer coefficient. For radiation, use the equation for net heat transfer rate.

Finally, substitute the known quantities and their units into the selected equation. Solve the equation numerically to find the answer. This method helps students work through heat transfer problems in a clear, step-by-step way.

Heat Transfer Calculations with Conduction, Convection

heat-transfer-calculations-with-conduction-convection

temperature and thermal equilibrium

Heat, Temperature, and Everyday Energy

Heat and temperature are key ideas in thermodynamics and in everyday life. People often connect temperature with hot and cold, but science gives it a more precise meaning. Temperature is the quantity measured with a thermometer. It is also linked to the average translational kinetic energy of particles. Heat is different from temperature. Heat is energy that moves from one place or material to another because there is a difference in temperature. That difference in temperature keeps heat...

zeroth law of thermodynamics

Thermal Equilibrium and the Zeroth Law

The zeroth law of thermodynamics explains thermal equilibrium between objects. If object A is in equilibrium with object B, and object B is in equilibrium with object C, then object A is also in equilibrium with object C. This transitive relationship is the key idea behind the law. A simple example uses metal blocks and a metal plate at room temperature. A cold metal block and a hot metal block are both placed on the plate. Over time, the cold block and the plate reach thermal equilibrium, and...

thermometers and temperature scales

How Thermometers Measure Heat

Thermometers measure temperature by using physical properties that change in a predictable way. One common example is volume. For most substances, volume increases as temperature rises. That idea is used in alcohol thermometers and in the original mercury thermometers. Other thermometer designs use different temperature-sensitive properties. Some measure electrical resistance, color, or the emission of infrared radiation. The alcohol thermometer is a common example. It contains red-dyed...

gas thermometers and the kelvin scale

Kelvin Temperature and Gas Thermometer Standards

Kelvin temperature is the absolute scale used in science, and it starts at absolute zero. That zero point matches the lowest possible temperature, where molecular motion reaches zero or the minimum allowed by quantum mechanics. Scientists use this scale because some physical quantities, such as the volume of an ideal gas, depend directly on absolute temperature. The Kelvin scale is part of the SI system of units, so its definition is more precise than simply using water’s freezing and boiling...

thermal expansion

Thermal Expansion in Air, Water, and Solids

Thermal expansion is the change in size or volume of a material as its temperature changes. A common example is the alcohol inside a thermometer. As the temperature rises, the alcohol expands and shows the change. Heated air also expands. It becomes less dense than the cooler air around it, so the surrounding air pushes it upward. This is why steam and smoke rise and why hot air balloons float. The same effect happens in liquids and gases, and it helps move heat upward in homes, oceans, and...

thermal stress

How Temperature Changes Create Stress

Thermal stress is the stress that builds up when an object changes temperature but cannot expand or contract freely. If the object would expand without restraint, the stress is compressive. If it would contract, the stress is tensile. This stress from heating or cooling can become large enough to cause damage. Engineers often reduce it by designing parts so they can move as temperature changes. Highway blocks, for example, are separated by gaps so thermal stress does not build up. When gaps...

thermal expansion and thermal stress: problem solving

thermal-expansion-and-thermal-stress-problem-solving

Golden Gate Bridge Thermal Expansion

Thermal expansion and thermal stress are shown through the Golden Gate Bridge. The bridge faces temperatures from -15 °C to 40 °C. At its coldest, the main span is 1275 m long. Assuming the bridge is made entirely of steel, the example asks for the change in its length across this temperature range. To solve the problem, the known values must be identified first. The initial length is 1275 m. The coefficient of linear expansion for steel is 12 x 10 -6 /°C, and the change in temperature is 55...

heat flow and specific heat

Heat Units and Specific Heat

Heat is energy transferred because of a temperature difference, and it can change an object’s temperature. Since heat is energy, its SI unit is the joule (J). Heat transfer is the movement of energy from one place or material to another, and it plays a role in home heating, cooking, and many industrial processes. Two common units for heat are the calorie and the kilocalorie. A calorie (cal) is the energy needed to change the temperature of 1 g of water by 1 °C, specifically between 14.5 °C and...

phase changes

Heat and Phase Change Energy

Heat and phase change energy explain why substances melt, freeze, boil, and condense. A solid turns into a liquid during melting, also called fusion. The reverse process is freezing. A liquid turns into a gas during evaporation. The reverse process is condensation. Each substance changes phase at specific temperatures. The melting point is the temperature where a substance melts or freezes. The boiling point is the temperature where a substance boils or condenses. These temperatures depend on...

calorimetry

Heat Exchange in an Insulated System

Calorimetry studies heat exchange in an insulated system. A calorimeter is a container that prevents heat transfer in or out. Scientists use calorimetry to measure heat and specific heat capacity. A calorimetry problem is any situation where the objects are thermally isolated from their surroundings. The key idea comes from conservation of energy. During heat transfer, the heat gained by the colder object must equal the heat lost by the hotter object. A simple example is water poured into a...

mechanisms of heat transfer i

Three Ways Heat Moves Between Objects

Heat transfer happens when there is a temperature difference. It can move fast, like through a cooking pan, or slowly, like through the walls of a picnic ice box. Heat transfer appears in many everyday situations, so it is hard to find a place where it does not occur. There are only three ways heat is transferred: conduction, convection, and radiation. A fireplace shows all three at once. Radiation carries most of the heat into the room. Conduction also moves heat into the room, but much more...

mechanisms of heat transfer ii

Convection and Radiation in Heat Transfer

Convection and radiation are two major ways heat moves. In convection, thermal energy is carried by the large-scale flow of matter. Warm air and water rise because they are less dense, so ocean currents and large-scale atmospheric circulation move heat from the tropics toward the poles and move cold air from the poles toward the tropics. Earth’s rotation changes these moving air currents. It interacts with the flow and helps produce the eastward movement of air in the temperate zones.

conduction, convection and radiation: problem solving

Heat transfer calculations with conduction and convection use the temperature difference to find the rate of heat flow. Radiation can also be part of the process. The main idea is that heat moves only because one area is hotter than another, and a larger temperature difference leads to faster transfer. To solve a heat transfer problem, first identify the type of transfer involved. It may be conduction, convection, radiation, or a combination of all three. Next, write down the unknown...

radiation: applications

Earth’s Energy Balance and Greenhouse Effect

Earth’s energy balance and the greenhouse effect help explain its average temperature. Earth is in radiative contact with both the Sun and dark space. It receives almost all of its energy from solar radiation, and it reflects some of that energy back into outer space. Dark space is very cold, about 3 K, so Earth also radiates energy into it. Heat can move quickly from soil and grasses, and frost can form on clear summer evenings, even in warm latitudes. In a first approximation, Earth’s...

absorption of radiation

Radiation Heat Transfer and Thermographs

Radiation heat transfer depends on temperature, surface area, and emissivity. The Stefan-Boltzmann law describes the rate of heat transfer by emitted radiation. In this law, σ is the Stefan-Boltzmann constant, A is the object’s surface area, and T is its temperature in kelvins. The fourth-power dependence on absolute temperature makes radiation highly sensitive to small temperature changes. Even a slight rise in temperature can change the emitted heat a lot. That sensitivity is why radiation...

key terms and concepts

Learn how to solve heat transfer problems by identifying conduction, convection, or radiation, choosing the right equation, and calculating the unknowns.

Heat Transfer Calculations with Conduction, Convection | JoVE K12

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Louisiana Student Standards for Science

High School

Chemistry

HS-PS3-3

HS-PS3-4

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Energy And Waves

transfer-and-transformation-of-energy-including-work

Transfer and transformation of energy (including work)

Thermal energy

Tennessee Academic Standards

PHYS.PS3.1

PHYS.PS3.2

Virginia  Standards of Learning

HIgh School

PS.5

PS.5.b

Texas Essential Knowledge and Skills

Earth Systems Science

112.49.c.8.

112.49.c.8.A.

Arizona Science Standards

Earth and Space Science

HS+E.E1

HS+E.E1U1.1

HS+Phy.P4

HS+Phy.P4U2.7

HS.P4

HS.P4U1.8

Alabama Course of Study Science

9-12.PS.1.1.b

Earth's Systems

9-12.ESS.2.7

Next Generation Science Standards

Florida Department of Education

SC.912.P.10

SC.912.P.10.4

Chemistry and Physics

IPC.6

IPC.6.D

new-york-state-science-learning-standards

New York State Science Learning Standards

Earth and Space Sciences

Earth’s Systems

HS. ESS2-3.

Energy Basics

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

Chemical changes and their accompanying ...

Mechanisms of Heat Transfer I

Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature ...

Mechanisms of Heat Transfer II

In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the ...

There are three methods by which heat transfer can take place: conduction, convection, and radiation. Each method has unique and interesting ...

Use models to explain thermal energy and its transfer.

The universe is composed of matter in different forms, and all forms of matter contain energy.&#160; The different forms of energy on Earth originate from ...

Types of Potential Energy

Potential energy is also known as energy at rest or stored energy. Common types of potential energy include the gravitational potential energy stored in ...

Types of Kinetic Energy

The amount of kinetic energy of an object depends on its mass and speed. Consider two balls of different masses rolling down an inclined plane at the same ...

Conservation of Mechanical Energy

The mechanical energy E of a system is the sum of its potential energy U and the kinetic energy K of the objects within it. What happens to this ...

/files/media/science-education/science-education-thumbs/14702.jpg

Conservative Forces

According to the law of conservation of energy, any transition between kinetic and potential energy conserves the total energy of the system. Hence, the ...

Non-conservative Forces

Non-conservative forces are dissipative forces such as friction or air resistance. These forces take energy away from a system as it progresses. Unlike ...

Conservation of Energy

The terms &#39;conserved quantity&#39;&#160;and &#39;conservation law&#39;&#160;have specific scientific meanings in physics, which differ from the ...

Conservation of Energy: Application

When solving problems using the energy conservation law, the object (system) to be studied should first be identified. Often, in applications of energy ...

Use mathematics and computational thinking to explain the Law of Conservation of Energy in a mechanical system in terms of kinetic and potential energy.

PS.PSc.7.2

Work

Work is done when energy is transferred from one object to another. In other words, work is when a force acts on something that undergoes a displacement ...

Positive, Negative, and Zero Work

Work is done on an object when energy is transferred to the object. In other words, work is done when a force acts on a body that undergoes a displacement ...

Work-energy Theorem

According to Newton&#x2019;s second law of motion, the sum of all the forces acting on a particle (net force) determines the rate of change in the ...

Work and Energy for Variable Forces

When an object is acted upon by a variable force, the amount of work done and the change in energy of the object can be more complex to calculate compared ...

/files/media/science-education/science-education-thumbs/14699.jpg

work-energy-theorem-for-motion-along-a-curve

Work-Energy Theorem for Motion Along a Curve

The work-energy theorem can be generalized to the motion of a particle along any curved path. The simple argument here is that the curved path can be ...

/files/media/science-education/science-education-thumbs/14700.jpg

Work Done Over an Inclined Plane

The center-of-mass framework helps to easily describe the work done on rigid bodies. Since the internal forces in a rigid body do no work, they can be ...

/files/media/science-education/science-education-thumbs/14701.jpg

Work Done by Many Forces

The total work done on an object acted upon by multiple forces can be computed using two methods that give the same result. In one method, the work done ...

/files/media/science-education/science-education-thumbs/14735.jpg

Work Done by Gravity

Gravitation is one of the four fundamental forces in nature. The force between objects on Earth and Earth itself is called gravity.
Like other forces, ...

/files/media/science-education/science-education-thumbs/14750.jpg

Use mathematics and computational thinking to explain work in terms of the relationship among the applied force to an object, the resulting displacement of the object, and the energy transferred to an object.

PS.PSc.7.3

Power

The concept of work involves force and displacement; meanwhile, the work-energy theorem relates the net work done on a body to the difference in its ...

Power Expended by a Constant Force

The relationship between work done and the time taken to do it can be explained using the concept of power. For example, several sprinters in a race may ...

Construct an explanation to infer the relationship between work and power, both quantitatively and qualitatively.

PS.PSc.7.4

Analyze energy transfers and transformations within a mechanical system.

Heat Transfer Calculations with Conduction, Convection

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