Thermal performance of reciprocating two-phase thermosyphon with nozzle

Flow images and thermal performances of the two-phase reciprocating thermosyphons (RT) with an internal nozzle at 50% volumetric filling ratio (FR) were measured. Two sets of flow snapshots and thermal performance data detected from two similar RTs with and without nozzle were compared. Above the critical reciprocating frequencies (fcr), the circulation routes of working fluid in the RTs with and without nozzle were reversed to cause disparities in thermal performances. At the reciprocating frequencies (f) of 1.75, 1.83, 1.92 and 2 Hz with four different heating and cooling duties for each fixed f, the time-mean local and regionally averaged Nusselt numbers (Nu) along the evaporator/condenser centerlines of the RTs with and without nozzle were dominated by reciprocation number (Reci) but subject to the coupled effects attributed from the heating and cooling duties indexed by boiling number (Bo) and dimensionless condenser thermal resistance (Rth,con). Local Nu were raised by increasing Reci, Bo and/or Rth,con for both RTs with and without nozzle. Due to the inversed liquid film circulation and jet impingement, the overall thermal resistances (Rth) of present RT with nozzle were reduced by 40.06-59.96% from those of RT without nozzle. To add engineering applications, evaporator Nu correlations were devised for present RT with nozzle.