الفهرس 
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Abstract
.Methods used to detel”tmine thermal conductivity with axial or radial heat flow are one dimensional conduction problems_ In radial heat flow methods, the longitudinal heat loss is eglected, while in axial heat flow methods, the radial heat loss is neglected.To guarantee one dimensional condition, guard heaters are used, but it is very difficult to maintai~ zero tempe-
rature differenoe between the main and the guard heaters.The assumption of one dimensional heat flow. may result in an approximate value of thermal onductivity when using these methods.To avoid the difficulties which arise in connection with the use of one dimensional methods for determination of thermal conduotivity, specially for thermal insulating materials. An apparatus has been designed and construeted taking into account the heat transmitted in the two direc¬tions through cylindrical samples of insulating materials at different mean temperatures. In the proposed apparatus, the heater which generates heat uniformly along it’s axis, is covered with the tested.