in a temperature control system using a controlled mix of high temperature pressurized gas and a cooled vapor / liquid flow of the same medium to cool a thermal load to a target temperature in a high energy environment , particular advantages are obtained in precision and efficiency by passing at least a substantial percentage of the cooled vapor / liquid flow through the thermal load directly , and thereafter mixing the output with a portion of the pressurized gas flow . this “ post load mixing ” approach increases the thermal transfer coefficient , improves control and facilities target temperature change . ad added mixing between the cooled expanded flow and a lesser flow of pressurized gas also is used prior to the input to the thermal load . a further feature , termed a remote “ line box ”, enables transport of the separate flows of the two phase medium through a substantial spacing from pressurizing and condensing units without undesired liquefaction in the transport lines .