# Heat Transfer Experiments

Thermal energy transfer involves the transfer of internal energy, which is the total amount of kinetic energy and potential energy of all the particles in the system. There are three main methods of thermal energy transfer. These are convection, conduction, and radiation

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Table of contents

## Heat transfer experiments

These are experiments used to investigate the behaviour of thermal energy transfer, depending on the method of energy transfer we are discussing.

Conduction is the transfer of thermal energy that is transmitted by collisions between atoms and molecules.

Convection is the transfer of thermal energy due to the movement of heated fluid.

There are two types of convection, namely, natural convection and forced convection. Natural convection occurs by the motion of fluid due to density differences in a fluid, which is caused by temperature differences. Forced convection occurs by a motion of fluid due to a pump or fan.

Radiation is the transfer of thermal energy in the form of electromagnetic radiation, which is emitted by a heated surface in all directions.

## Conduction heat transfer experiment

The aim of this experiment is to investigate the rate of conduction in different metals. More specifically, four different types of metal will be used to investigate which metal has the highest and lowest rate of conduction. Let us look at some examples below.

Some examples of conduction heat transfer are:

• When hot tea is poured into a cup, collisions between the high-temperature molecules and the atoms comprising the cup will cause energy to transfer from the hot coffee to the cup.
• When an ice cube is positioned on a warmer surface, the collision between the molecules and atoms of the surface and the ice will cause thermal energy to transfer from the warmer surface to the ice, causing the latter to melt.

The most efficient method of heat transfer is conduction. This method of heat transfer occurs when there is a temperature gradient across a body.

### Equipment for a conduction heat transfer experiment

• Stand.
• Burner.
• Ball-type bearing.
• Aluminium.
• Copper.
• Conduction ring.
• Iron.
• Brass.
• Wax.
• Stopwatch.

Conduction experiment schematic.

### Methodology for a conduction heat transfer experiment

1. Firstly we attach ball bearings onto a stand and position a Bunsen-type burner underneath the ball bearings.

2. Then we position four different types of metal strips of equal width and length on the ball bearings, two horizontally and two vertically such that they meet at the centre, as seen in figure 1. These four metals are iron, brass, copper, and aluminium.

3. Using wax, we attach the metal strips to the ball bearings so that they won't move.

4. The strips should be heated using the burner at the central point where the strips touch.

5. The heat should be conducted from the point of touch of the strips to the ball bearing.

6. When the heat is transferred along the length of the ball bearing, the wax melts and the ball bearing drops.

7. We use a time watch to record the time required for the wax to melt on each metal strip and construct a table with the recorded data.

8. The experiment is then repeated to calculate an average of each time.

As we know, thermal conductivity is the ability of a material to conduct heat. A material with high thermal conductivity will be heated faster than materials with low thermal conductivity. Using the time taken for each strip to fall is used to find which material is the best thermal conductor or had the highest thermal conductivity.

The results are shown below in the table. The metals are ranked based on the time it took for the wax to melt on each strip. The metal with the highest metal conductivity is copper and the metal with the lowest thermal conductivity is iron.

 Metals ranked from highest to lowest thermal conductivity 1. Copper 2. Aluminium 3. Brass 4. Iron

#### Sources of random errors in conduction heat transfer experiments

• Each metal strip should be the same size, i.e., width and length.
• The amount of wax used should be the same on each strip.
• Identical ball bearings should be used.

#### Source of systematic errors in conduction heat transfer experiments

• Not allowing the rods to cool to room temperature before heating, so that they are all heating from the same temperature.

Factors affecting heat transfer by conduction:

• Temperature difference.
• Cross-sectional area.
• The thickness of the material.
• Thermal properties of the material.

## Convection heat transfer experiment

The aim of this experiment is to investigate the rate of convection of potassium permanganate crystals in two different temperatures of water.

Some examples of convection heat transfer are:

• Natural convection:
• Sea breeze: The sun heats up the area around land and sea. The sea is warmed up much slower than the land. This heats the air in the atmosphere above it. High-temperature air is less dense, and is therefore expanded, creating a low-pressure area over the land near the coast while there is high pressure over the sea. The air pressure difference causes the air to flow from sea to land. The sudden airflow is what is known as a sea breeze.
• Land breeze: This is the reverse situation. When the sun sets, the land and sea start cooling down. The land loses heat relatively faster compared to water due to the differences in heat capacity. Thus the temperature of the sea is relatively higher, which creates low air pressure above the sea while the pressure above land is high. The pressure difference between the air above land and sea results in airflow from land to the sea, also known as a land breeze.
• Forced convection:
• Refrigerator: Gas is circulated by a fan through copper lines inside a refrigerator. This gas absorbs the heat in the refrigerator, and is circulated back outside of the refrigerator.

### Equipment for convection heat transfer experiments

• Bunsen-type burner.
• Tripod.
• Beaker.
• Water.
• Potassium permanganate crystals.
• Heatproof mat.

Convection experiment schematic.

### Methodology for convection heat transfer experiments

1. The beaker is filled with 250ml cold water and placed on the tripod. A heatproof mat, as seen in the schematic in figure 2, sits under the base.
2. The crystals are dropped very carefully and slowly in the centre of the beaker so that the crystals are not dissolved.
3. The beaker is then heated using the burner.
4. Observations are then recorded as shown below.
5. The experiment is repeated using hot water instead of cold. Any observations are recorded.
6. Heat the beaker using the Bunsen burner and record observations
7. Repeat the experiment using the same amount of water but instead of cold water, hot water should be used and observations recorded.

#### Observations in convection heat transfer experiments

• Heat is initially transferred from the burner flame to the walls of the beaker by conduction.

• Then the water closer to the flame is heated and then expanded. Hence the water becomes less dense and rises to the top of the glass. Meanwhile, the crystals are slowly dissolved and are also moved upwards with the expanding water.

• The water at the top of the glass is cooled after a while and becomes denser, causing it to fall to the bottom again.

When liquid is heated it expands, which is known as thermal expansion.

#### Analysis of results in convection heat transfer experiments

• This whole process of the recorded observations is continued. This is what we call heat transfer by convection, as heat is transferred through the liquid.

• The crystals follow this path called convection current, where the crystals are rising to the top and then fall to the bottom.

When the process is repeated with cold water, it is observed that the convection current is faster in hot water. Therefore a conclusion can be drawn from the above observations that the higher the temperature of the liquid, the higher the kinetic energy of the molecules. Hence, in the hot water experiment, the molecules of the crystals are dissolved and move faster than in the cold water experiment.

#### Sources of random errors in convection heat transfer experiments

• The amount of water in the beaker should be exactly the same.

• The burner should have the same flame in both experiments.

• The crystals should have the same size.

#### Factors affecting convection

• The temperature gradient between the two materials of interest.
• The cross-sectional area of the materials involved.
• The properties of the materials.

## Radiation heat transfer experiment

The aim of the experiment is to investigate whether the amount of infrared radiation absorbed by a surface depends on the physical characteristics of that surface.

Thermal energy transfer from the sun to the earth in the form of ultraviolet light is an example of heat transfer via radiation.

### Equipment in radiation heat transfer experiments

• Hot water.
• four different coloured beakers.
• Thermometer.

Radiation experiment. Georgia Panagi- StudySmarter Originals

### Methodology in radiation heat transfer experiments

1. Position the four different coloured flasks on a surface, and leave them at room temperature so that they reach the same temperature.
2. Fill the flasks with hot water.
3. Create a table with five columns, one with time and one column for each coloured flask. Record the starting temperature.
4. Measure the temperatures at regular intervals, say, every 30 seconds.

#### Analysis of results in radiation heat transfer experiments

• The results from the table are plotted in a temperature vs time graph including all of the different temperatures for each flask. Use different colours for each flask. The expected results of the graph should be similar to figure 4, which is an indicated temperature-time graph.

Indicated temperature vs time graph. Georgia Panagi- StudySmarter Originals

• Any difference in heat loss in the beakers must be due to the infrared thermal radiation as beakers are identical in shape.
• The rate of heat loss or cooling can be compared for each beaker can be concluded from the graph.
• It can also be concluded from the graph that the intensity of the emitted thermal radiation must depend on colour as well as the temperature of the body (which was the same in this experiment) and the surface area (which was also the same during this experiment).

#### Sources of random errors in radiation heat transfer experiments

• Take repeated readings for each coloured flask.

• Read the values on the thermometer at eye level, to avoid parallax error.

• Same amounts of hot water.

• Same starting temperature of the water.

• Same time interval.

#### Sources for systematic errors in radiation heat transfer experiments

• Make sure the starting temperature of the water is the same for each material.
• Use a data logger connected to a digital thermometer to get more accurate readings.

### Safety considerations for heat transfer experiments

• Safety goggles should be worn when using a Bunsen burner.
• Keep water away from all electrical equipment.
• Make sure not to touch the hot water directly.

## Heat Transfer Experiments - Key takeaways

• There are three main methods for energy transfer: conduction, convection, and radiation.

• Conduction is the transfer of thermal energy that is transmitted by collisions between atoms and molecules due to temperature differences.

• Convection is the transfer of thermal energy due to the movement of heated fluid. There are two types of convection, namely, natural convection and forced convection.

• Radiation is the transfer of thermal energy, in the form of electromagnetic radiation, which is emitted by a heated surface in all directions.

#### Flashcards in Heat Transfer Experiments 15

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##### Frequently Asked Questions about Heat Transfer Experiments

What are different types of heat transfer?

The different types of heat transfer are convection, radiation, and conduction.

What is a good example of heat transfer?

Cooking on the stove. There is energy transfer in the form of heat between the thermal energy of the stove and pan.

What are four examples of convection?

Four examples of convection are land breeze, sea breeze, refrigerator, and electronic cooling.

Which mode of heat transfer is most efficient?

Conduction is the most efficient method of heat transfer.

What happens to a solid when it is heated?

The particles gain energy and break away from one another.

## Test your knowledge with multiple choice flashcards

When does convection occur?

What is the systematic errors in the conduction experiment?

Which of the following is a random error of the convection experiment?

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