Contents of Journal of Thermoelectricity, No.4, 1996

G.N.Logvinov. Thermoelectricity in Submicron Semiconductors

The characteristic peculiarity of submicron samples, submicron layers in particular, is the surface energetic dissipation dominance in comparison with volume one. This means that electron and phonon heat flows can be varied by thermal boundary conditions change, the function of the volume energetic electron-phonon interaction in generation of electron and phonon temperature gradients is unimportant. This fact is rather urgent in thermoelectricity because it makes possible to predict theoretically the increase of thermoelectric figure of merit parameter. This report describes principal basis for temperature distribution forming and arising therewith thermo-emf and thermoelectric currents in semiconductors with limited dimensions, submicron, in particular.

L.N.Vikhor. Optimal Function as a New Step of the Thermoelectricity Development

Recently received results of optimal FGM simulation for thermoelectric coolers and generators are described. A possibility of thermoelectric cooling and generating efficiency improvement at the expense of optimal FGM use is demonstrated.

Todd M. Ritzer, Michael J. Nagy, and Richard J. Buist. Evaluation of Thermal Junction Quality in Thermoelectric Assemblies Using Transient Analysis Technology

This paper describes the application of the Transient Analysis Test method to evaluate the integrity of thermal junctions in a thermoelectric (TE) assembly. The quality of thermal junctions (Q_jctn) in assemblies was measured by creating a thermal gradient in the TE modules comprising an assembly and analyzing the decay of the residual Seebeck voltage. A study was made of various junction conditions that exist between the TE module and its heatsinks which are common to most assembly techniques. Poor thermal contacts were deliberately introduced such as insufficient thermal grease, inadequate compression and improper surface finishes in test assemblies in order to simulate typical assembly defects. A direct correlation between good and inadequate thermal junctions was established and illustrated through graphic test data evaluation.

Richard J. Buist and Paul G. Lau. Theoretical Analysis of Thermoelectric Cooling Performance Enhancement via Thermal and Electrical Pulsing

This paper is an introduction and theoretical investigation of the fast-transient cooling characteristics of a TE module under applied high-current electrical pulses. A temperature- dependent, finite element model was developed to accurately model the fast-transient performance. Analysis of experimental data is presented to verify the accuracy and validity of the model and the conclusions derived therefrom. It has been shown that cold plate temperatures are achievable from a typical TE module beyond that obtainable by conventional, steady-state means. The cooling enhancement is by virtue of the fad that Peltier cooling is a surface effect and extremely concentrated at the cold junction, whereas. Joule heating is a volume effect and is distributed throughout the volume of the TE pellet. As such, most of the Joule heat takes a longer time to reach the cold plate than the Peltier cooling effect. This phenomenon is theoretically demonstrated by applying a high-current pulse after the minimum steady-state cold plate temperature has been established. Calculations have shown that cold plate temperatures can be reduced by 16 K below that via steady- state means. These transient enhancements are admittedly short-lived and have limited effectiveness. However, the results presented herein suggest that farther exploitation of the fundamental differences between Peltier and Joule heat are possible. A concept is re-introduced which consists of thermally and electrically separating the cold electrode from the TE pellet. This pulse cooling concept was originally conceived over 30 years ago by Reich[1] at the Berg-Warner Research Center.

Michael J. Nay and Richard J. Buist. Transient Analyse of Thermal Junctions within a Thermoelectric Cooling Assembly

The performance of a thermoelectric (TE) heat exchanger assembly Is greatly affected by the quality of the thermal junctions connecting the modules and the mounting surfaces of the heat/cold sinks. The quality of this junction, in turn, is off cried by many different variables. These include heat sink surface quality, quantity of thermal grease, contaminates in the thermal grease, assembly screw torque, tapped hole quality, surface finish of the modules and the variance in module heights. Until now, junction quality could only be verified by disassembly of the heat exchanger or inferred from a fall cooling performance test of the assembly. This paper details a new, transient test method which accurately and dependably characterizes the module-heat-sink thermal junctions. A small current is applied to the TE modules in a thermoelectric assembly. This induces a small temperature difference across the module and between the ceramics of the module and its neighboring heat/cold sink. Power is then removed and the module's ceramics return to the temperature of its neighboring heat sink. The rate of temperature decay is directs proportional to the junction quality. Thus, the residual Seebeck decay waveform directly correlates to thermal junction quality, providing the means for rapidly and accurately characterizing assembly quality.

A.A.Pustovalov. Modern State and Perspectives of Space Using Radionuclide Thermoelectric Generators (RTG)

History, contemporary state and prospects of radioisotope thermoelectric generator for space application are analized: historical information, problems of RTG nuclear safety, state of space RTGs development in the USA, state of space RTG development in Russia, RTG prospects in the XXI-century space programs.

N.G.Kokodii. New Thermal Meters of Energetic Characteristics of Laser Radiation

Principles for new thermoelectric devices construction for energy of pulse, power and intensity distribution measurement in a laser radiation beam have been described. Peculiarities of the devices construction enable essentially decrease their time constant, mass and dimensions. Information processing by microcomputer offers additional information on radiation parameters. Thermal (thermoelectric) devices are broadly used for measurement of energetic characteristics of laser radiation. Principles of their construction have been designed long ago, it is well known their advantages and disadvantages. But carrying on investigations in thermoelectricity and possibilities of new electronic equipment make it possible to improve the parameters of available devices greatly and to develop new measuring devices. The present work considers these cases: investigations of thermal processes in the absorbing load offer gradient calorimeters with best parameters than available ones, use of microcomputer for data processing permits to acquire the information on intensity distribution in a radiation beam.