Heat Pipe Design Heat Transport Limits  Viscous Limit  --viscous forces Chart B shows the five heat transport  The amount of power that a heat pipe prevent vapor flow from the limits as a function of operating  can transport is an important heat pipe  evaporator to,the condenser.  temperature for a copper/water heat design consideration.Depending on the  Sonic Limit -- vapor flow reaches pipe with a sintered wick structure. application,heat pipes can be designed evaporator. The sonic velocity when  In most cases,the capillary limit is to carry a few watts or several kilowatts. exiting the evaporator.                         the limiting factor in a heat pipe Heat pipes transfer much higher powers  Capillary Pumping Limit --sum of   design.The capilliary limit is a strong  for a given temperature gradient than the  the liquid,vapor and gravitational function of the wick structure and best metallic conductors. pressure drops exceed the capillary the operating orientation. pumping capability of the wick Five primary heat  transport limits,  structure. which are a function of operating  Entrainment or Flooding Limit   temperature, determine the maximum --high velocity vapor flow prevents the heat  transport capability for a heat pipe. condensate from returning to the evaporator.  The five transport limits are: Boiling Limit --boiling in the heat pipe evaporator wick structure.