How the Peltier Effect Powers Cooling and Heating Technologies
The entire experiment is based on the purpose of the heat generator that also derives from the Peltier effect application.
Here, we find a different concept of the Peltier effect. The experiment called ‘Peltier effect’ was discovered by a French scientist in 1834. The concept was named after him.
This experiment is all about absorption or radiation of heat effect when there will be the passage of electrical current. We call the electrical junction a Peltier junction.
The concept of LJ effort is the fact where heat is given out when an electrical current is passed across the junction of two materials. Detailed information on the Peltier effect in thermocouple has been provided here.
Peltier Effect and Thomson Effect
The Peltier effect and Thomson effect possess some similarities. Thomson effect is something which states that the generation of reversible heat is possible when the passage of electrical current is sent via a conducting material under a certain temperature gradient.
The thermoelectric cooling devices are dependent on the Peltier effect. Each effect generated from the Peltier experiment is meant to convert the electrical energy into a temperature gradient.
However, we will study it later. Let’s clarify all your doubts on Peltier effect efficiency. The efficiency of the Peltier modules is found to be around 5% only. Also, it is concluded that there is an additional loss of 3% during the process.
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In the above figure, the electric current is travelling through a circuit comprising two different Peltier materials. One Peltier device called a couple consists of one n-type and one p-type semiconductor pellet.
The charge carries the negative electron and positive holes. This behaviour also promotes the transport of heat. Thermoelectric coolers (TECs) are used as Peltier effect devices. These devices are suitable for Peltier effect as they act as the beast heat exchanger between two electrical junctions.
The TECs Have Certain Benefits for Which it is Used in the Peltier Effect. Those Points Are:
Long lifetime
Low maintenance
Controllable
Tolerate extreme environments
Highly Performance-based
No emission of any chlorofluorocarbons or refrigerants
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The Experiment of Peltier Effect Gives Two Annotations Such As
Heat is evolved at one junction
Heat is absorbed in the other junction
This is why the Peltier effect is considered as the converse of the Seebeck effect. So, the electric current is passed through a fuse consisting of its two dissimilar junctions. Heat is at one and absorbed at another junction. This is the basic output of the entire Peltier effect.
The Seebeck effect behaves like the opposite of the Peltier effect as they do not keep their function in one path but in two different ways.
You can visualize from the figure that the current is able to pass within the two dissimilar natures, such as one is the absorption of heat, and another is releasing heat.
Peltier Thermocouple
In a Cu-Fe thermocouple, the current flows from Cu to Fe, at junction number 1. In this case, the heat is absorbed. So, the thermocouple gets cooled.
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However, in junction 2 you notice that the current flows from Fe to Cu and heat is liberated. That is why it gets heated.
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The reverse of the current occurs during this experiment. This initiates a healing effect at junction 1 and initiates the cooling effect at junction 2. This is why the Peltier effect is considered a reversible process. The reversible process is dependent on the direction of the current.
The Peltier effect is a fact that depends on the passage of electric current and the absorption or rejection of heat current. Here, heat energy is absorbed or sent out from a homogeneous conductor. The Peltier effect is something that enables us to detect the different flows of electricity.
The accompanying heat current is a type of electric current that can be explained by the different velocities of the flow of the electrons. All of these electrons are an active carrier of electric current. The electric flow of the current has certain velocities. Each electron’s velocity depends on the conduction electrons’ energies.
Peltier Coefficient
Peltier coefficient can be denoted as the total amount of heat evolved or absorbed at one end of the junction of a thermocouple during the passage of one ampere of current flows through it within one second (one coulomb).
Pie ‘π’ is the symbol that is used for the Peltier coefficient. The unit of measurement is volt. Assume that H is the total heat absorbed or sent out at one point, then the formula for Peltier effect is:
H = π I t
Here, t = total time
I = current flow through the conductor
π = Peltier coefficient
Peltier electromotive force or Peltier emf is found at that junction where the Peltier coefficient is found. The co-efficient relies on certain facts such as the pair of metals in contact and the junction’s temperature.
FAQs on Understanding the Peltier Effect in Physics
1. What is the Peltier effect in Physics?
The Peltier effect is a thermoelectric phenomenon where heat is either absorbed or released at the junction of two different electrical conductors when an electric current is passed through them. One junction becomes cool (absorbs heat) while the other becomes hot (releases heat). This effect essentially converts electrical energy into a temperature gradient.
2. What is the main difference between the Peltier effect and the Seebeck effect?
The main difference lies in their cause and effect. The Peltier effect is the converse of the Seebeck effect. In the Peltier effect, an electric current causes a temperature difference between two junctions. In the Seebeck effect, a temperature difference maintained across two junctions generates an electromotive force (voltage) and drives an electric current.
3. How does a Peltier device (thermoelectric cooler) work?
A Peltier device, or thermoelectric cooler (TEC), typically consists of two semiconductor pellets, one n-type and one p-type, connected by a metallic plate. When a DC current flows through the circuit, charge carriers (electrons in n-type, holes in p-type) move from a low energy level to a high energy level at one junction, absorbing thermal energy and making that side cold. At the other junction, they move to a lower energy level, releasing thermal energy and making that side hot.
4. What are some real-world examples and applications of the Peltier effect?
The Peltier effect is used in applications requiring precise temperature control or cooling in a compact space. Common examples include:
- Portable coolers: Small refrigerators for cars or camping that don't require compressors.
- CPU Coolers: For cooling computer processors and other electronic components.
- Scientific Instruments: Used in devices like PCR machines for rapid heating and cooling cycles (thermal cyclers) and in infrared detectors.
- Dehumidifiers: To cool a surface and condense water vapour from the air.
5. Why is the Peltier effect considered a reversible process?
The Peltier effect is considered reversible because its thermal behaviour depends directly on the direction of the electric current. If you reverse the direction of the current flowing through the thermocouple, the hot junction will become cold and the cold junction will become hot. This is unlike Joule heating, which is an irreversible process as it produces heat regardless of the current's direction.
6. What is the Peltier coefficient (π) and its formula?
The Peltier coefficient (π) is defined as the amount of heat energy absorbed or released at a junction per unit charge that passes through it. It depends on the pair of materials and the temperature of the junction. The formula for the heat (H) transferred is given by:
H = π * I * t
Where:
- H is the heat absorbed or evolved.
- π is the Peltier coefficient (in Volts).
- I is the current (in Amperes).
- t is the time (in seconds).
7. Can a Peltier device be used to cool an entire room?
No, a Peltier device is generally not practical for cooling an entire room. While it effectively moves heat from one side to another, it has relatively low efficiency (around 5-10%) compared to conventional compressor-based air conditioners. The heat generated on the hot side of the device, plus the waste heat from its own inefficiency, must be dissipated. This makes it suitable for small, enclosed spaces or spot cooling but inefficient for large-scale applications like room air conditioning.
8. How does the Peltier effect fundamentally differ from the Joule heating effect?
The fundamental difference is in their nature and cause. The Peltier effect occurs only at the junction of two different materials, is reversible, and depends linearly on the current (I). In contrast, Joule heating occurs uniformly throughout any conductor carrying a current, is irreversible (always produces heat), and is proportional to the square of the current (I²). Joule heating is a consequence of resistance, while the Peltier effect is a thermoelectric property of the material interface.
