HOMOGENEOUS NUCLEATION AND THE HEAT-PIPE BOILING LIMITATIOND. Mishkinis and J. M. Ochterbeck UDC 536.24 Criteria for phase change in classical heat pipes and loop heat pipes with microporous capillary structures of wicks have been formulated and developed. The criteria are based on homogeneous nucleation and cluster theory to evaluate the superheat required for phase change to occur in microchannels. The results can be employed in analyzing the limiting operational criteria and heat-transfer capacity of heat pipes based on the boiling limit. Clemson University, Clemson, SC 29631; email: Donatas@CLEMSON.EDU. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 76, No. 4, pp. 61-64, July-August, 2003. Original article submitted December 24, 2002.