4.1 Fundamentals of the Peltier effect

The Peltier effect is a thermoelectric phenomenon that creates heat transfer between two materials when electric current flows through them. This effect forms the basis for thermoelectric cooling devices, which can create temperature differences by absorbing and rejecting heat at opposite junctions.

Understanding the Peltier effect is crucial for grasping how thermoelectric coolers work. It involves concepts like heat flux, charge carrier flow, and temperature gradients. These principles are key to developing efficient cooling systems for various applications.

Peltier Effect Fundamentals

Thermoelectric Phenomenon and Cooling Mechanism

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• Peltier effect describes heat transfer between two dissimilar conductors or semiconductors when electric current flows through their junction
• Thermoelectric cooling utilizes the Peltier effect to create a heat flux between two different types of materials
• Charge carrier flow (electrons or holes) across the junction carries heat energy
• Heat absorption occurs at one junction, creating a cold side
• Heat rejection takes place at the opposite junction, forming a hot side

Principles of Heat Transfer in Peltier Devices

• Junction temperature difference develops between the cold and hot sides
• Peltier coefficient quantifies the amount of heat transferred per unit of current
• Reversibility allows the device to function as a cooler or heater by reversing current direction
• Temperature gradient forms across the device due to heat absorption and rejection
• Thermal conductivity of materials influences the efficiency of heat transfer

Peltier Effect Characteristics

Temperature Dynamics and Material Properties

• Junction temperature depends on the current magnitude and material properties
• Peltier coefficient varies with temperature and material composition
• Seebeck coefficient relates to the Peltier coefficient through the Thomson relation
• Material selection impacts device performance (bismuth telluride, silicon-germanium)
• Doping levels in semiconductors affect charge carrier concentration and Peltier effect strength

Operational Factors and Device Efficiency

• Current density influences cooling capacity and temperature difference
• Joule heating occurs within the device, competing with the Peltier cooling effect
• Thermal resistance between junctions affects overall temperature difference
• Figure of merit (ZT) quantifies thermoelectric material efficiency
• Coefficient of Performance (COP) measures the cooling efficiency of Peltier devices