KINETIC MODEL FOR HEAT TRANSFER IN HELIUM II,
CONNECTICUT UNIV STORRS
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A model is proposed for the heat transfer in helium II when the net mass transfer is zero and the temperatures are constant. It is assumed that heat is transferred by two processes 1 by the force coupling between atoms which is the ordinary heat conduction process in solids and 2 by transfer of atoms along with their associated energies. The heat transferred by process 1 is a small fraction of the total except at very low temperatures and is not dealt with here. It is assumed that the transfer of atoms is accomplished in some fashion which maintains at least a relatively constant microscopic density. The number of thermally excited normal atoms leaving an area is assumed to be proportional to thermomechanical pressure. As far as the heat transfer is concerned, only those normal atoms leaving the area which are accompanied by returning thermally unexcited super atoms are important. Assumptions are made concerning the probabilities for a moving normal atom to be accompanied by a return super atom in wide and in narrow channels. The heat current is calculated as a function of thermomechanical pressure and temperature and is found to agree with experimental results. A brief discussion is given of the relationship of this model to some existing theories of helium II.