Experiments on Room Temperature Nernst-Ettingshausen Refrigerators

Cooling experiments with a (transverse) Nernst-Ettingshausen (NE) refrigerator using properly oriented and shaped single crystals of pure bismuth are described. By cooling the hot junction T_h of the specially designed refrigerator with flowing water, temperatures as low as 191 K were achieved at the cold surface while maintaining the warm surface at 279 K. Measurements were carried out for various values of the electrical current up to 85 amp and various values of the magnetic field up to 90 kgauss. The experimental results were found to be essentially in accord with the theory concerning the operating characteristics of shaped devices. Since the temperature difference occurred across a 5mm distance, an average temperature gradient of 170 K/cm was calculated.