A method of controlling a temperature control system comprising a two-phase refrigerant and a vapor cycle refrigeration system including a compressor and a condenser each having an input and output for circulating refrigerant at a controllable temperature to and from a load having input and output terminals and a known thermal capacity, the temperature control system including a subsidiary flow circuit for enhancing the performance of the system, comprising: a subsidiary heat exchanger coupled between the flow from the output of the condenser to the load input and the flow from the load output to the input of the compressor, said subsidiary heat exchanger having a first flow path including an input receiving flow from the condenser, a thermal expansion valve upstream of the subsidiary heat exchanger and a pressure valve downstream of the subsidiary heat exchanger and an output therefrom coupled to the load input, the subsidiary heat exchanger also including a second flow path in parallel thermal exchange relation along the length of the first flow path, and an output from the subsidiary heat exchanger coupled to the compressor input; the method comprising: opening a thermo expansion valve upon rise of the inlet temperature disposed in the second flow path between the subsidiary heat exchanger and the input to the compressor, sensing flow through the thermo expansion valve using a fluid sensing device at the exit to the thermo expansion valve, collecting fluid that is backed up at the thermo expansion valve during a ramp-up phase of the cycle, in which the compressor is directly connected to the load bypassing the condenser, thermal expansion valve, subsidiary heat exchanger and pressure valve, using a capacitor downstream of the load and upstream of the thermo expansion valve; condensing refrigerant within the load until the thermo expansion valve simultaneously allows refrigerant collecting at the load to flow through the thermo expansion valve and regulates a temperature of the refrigerant in its two phase state ahead of the thermo expansion valve, and allowing flow through the thermos expansion valve only after a pressure and temperature upstream of the thermo expansion valve reaches a final temperature and pressure. a subsidiary heat exchanger coupled between the flow from the output of the condenser to the load input and the flow from the load output to the input of the compressor, said subsidiary heat exchanger having a first flow path including an input receiving flow from the condenser, a thermal expansion valve upstream of the subsidiary heat exchanger and a pressure valve downstream of the subsidiary heat exchanger and an output therefrom coupled to the load input, the subsidiary heat exchanger also including a second flow path in parallel thermal exchange relation along the length of the first flow path, and an output from the subsidiary heat exchanger coupled to the compressor input; the method comprising: opening a thermo expansion valve upon rise of the inlet temperature disposed in the second flow path between the subsidiary heat exchanger and the input to the compressor, sensing flow through the thermo expansion valve using a fluid sensing device at the exit to the thermo expansion valve, collecting fluid that is backed up at the thermo expansion valve during a ramp-up phase of the cycle, in which the compressor is directly connected to the load bypassing the condenser, thermal expansion valve, subsidiary heat exchanger and pressure valve, using a capacitor downstream of the load and upstream of the thermo expansion valve; condensing refrigerant within the load until the thermo expansion valve simultaneously allows refrigerant collecting at the load to flow through the thermo expansion valve and regulates a temperature of the refrigerant in its two phase state ahead of the thermo expansion valve, and allowing flow through the thermos expansion valve only after a pressure and temperature upstream of the thermo expansion valve reaches a final temperature and pressure. opening a thermo expansion valve upon rise of the inlet temperature disposed in the second flow path between the subsidiary heat exchanger and the input to the compressor, sensing flow through the thermo expansion valve using a fluid sensing device at the exit to the thermo expansion valve, collecting fluid that is backed up at the thermo expansion valve during a ramp-up phase of the cycle, in which the compressor is directly connected to the load bypassing the condenser, thermal expansion valve, subsidiary heat exchanger and pressure valve, using a capacitor downstream of the load and upstream of the thermo expansion valve; condensing refrigerant within the load until the thermo expansion valve simultaneously allows refrigerant collecting at the load to flow through the thermo expansion valve and regulates a temperature of the refrigerant in its two phase state ahead of the thermo expansion valve, and allowing flow through the thermos expansion valve only after a pressure and temperature upstream of the thermo expansion valve reaches a final temperature and pressure.