Peltier coefficient

The other primary thermoelectric phenomenon is the Peltier effect, which is the generation or absorption of heat at the junction of two different conductors when a current flows in the circuit. Whether the heat is evolved or absorbed is determined by the direction of the current flow. The amount of heat involved is determined by the magnitude of the current, I, and the Peltier coefficients, 7T, of the materials ... 

Peltier coefficient for charge-transfer reaction h, V density of phase k, glcm ... 

The thermoelectric effect is due to the gradient in electrochemical potential caused by a temperature gradient in a conducting material. The Seebeck coefficient a is the constant of proportionality between the voltage and the temperature gradient which causes it when there is no current flow, and is defined as (A F/A7) as AT- 0 where A Fis the thermo-emf caused by the temperature gradient AT it is related to the entropy transported per charge carrier (a = — S /e). The Peltier coefficient n is the proportionality constant between the heat flux transported by electrons and the current density a and n are related as a = Tr/T. 

THERMOCOUPLE. In 1821, Seebeck discovered that an electric current flows in a continuous circuit of two metals if the two junctions are at different temperatures, as shown in Fig. 1. A and B are two metals, T and T are the temperatures of the junctions. I is the thermoelectric current. A is thermoelectncally positive to B if 7i is the colder junction. In 1834, Peltier found that current flowing across a junction of dissimilar metals causes heat to be absorbed or liberated. The direction of heat flow reverses if current flow is reversed. Rate of heat flow is proportional to current but depends upon bodi temperature and the materials at die junction. Heat transfer rate is given by PI, where P is the Peltier coefficient in watts per ampere, or die Peltier emf in volts. Many studies of the characteristics of thermocouples have led to the formulation of three fundamental laws ... 

The Peltier effect, on which thermopiles are based, is the heat released or taken up when a current flows through an isothermal junction. In a thermopile, the current flows in the opposite direction through the two junctions and, thus, transfers heat from one junction to the other. The Peltier coefficient, II, is defined as the heat absorbed per unit charge flow ... 

The Peltier coefficient is obtained by dropping the temperature gradient terms ... 

Peltier coefficient -> molar electrochemical Peltier heat Peltier effect Peltier heat... 

Peltier coefficient, II, is the ratio of the rate at which heat flows across a material to the electrical current flow and is, therefore, a nonsymmetrical second-rank tensor that relates a scalar with another second-rank tensor ... 

The Peltier coefficient II can be found from Kelvin s relation to be... 

The effectiveness of devices using thermoelectric effects depends on the magnitude of the relative Peltier coefficient, II, or its equivalent, the relative Seebeck coefficient, S. However, these are not the only material parameters of importance. As an example, consider the operation of a heat pump. The amount of heat produced or absorbed is... 

Peltier coefficient See coefficient, Peltier, penetrant An agent that is used to increase the speed and ease with which a bath or liquid permeates a material being processed by effectively reducing the interfacial tension between the soHd and liquid. See barrier plastic permeability. 

Electrical conduction and heat transport are closely linked, the connection being described by three thermoelectric coefficients, the Seebeck coefficient (or thermopower), the Peltier coefficient and the Thomson coefficient, all of which have relevance to thermoelectric power generation and refrigeration. In perovskites, the most reported values are for the Seebeck coefficient. The magnitude and sign (+ or -) of the Seebeck coefficient are related to the concentration and type of mobile charge carriers present. For band-like perovskites, the magnitude of the Seebeck coefficient is proportional to the density of states, either in the conduction band, for electron transport, or the valence band for hole transport. 

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