Helium Heat Rectifiers and a Simple Magnetic Refrigerator
A heat valve having an inherently unidirectional conductivity would simplify both single and cyclic magnetic cooling because of its automatic action. As previously reported, such a rectifier can be made by confining a liquid mixture of heliums 3 and 4 in a vertical stainless steel tube fastened to a copper block at the upper end but leading into a hole in a copper block at the lower end. It conducts heat downward but not upward; ratios in the neighborhood of 1000 have been obtained. Figure 1 shows one of the best designs to date for temperatures above 1°K.2 The chamber at the top, for overcoming Kapitza resistance, may not be necessary except below 1°K. A capillary may be used to change mixtures for investigative purposes. Sealed units have been made. Reproducibility has been satisfactory but the ability of various factors to change the conductivity enormously in both directions indicates that careful analysis is needed.
KeywordsSilica Aerogel Copper Block Automatic Action Unbalanced Voltage Uniform Tube
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