To explore the hunting behavior of the thermostatic-expansion-valve (TEV)

dynamic characteristics of the TEV (TEX2 externally balanced type) control-loop ranged from stability to vibration were studied under the selected 7 sets of water mal-distribution experimentally. Results showed that as F2 dropped from 36.9% to 27.0%

the TEV control-loop was stable and the overall evaporator capacity decreased by only 3.4%. As F2 dropped from 27.0% to 9.1%

evaporator overall outlet temperature changed from stability to vibration. Its vibration amplitude increased gradually with the phase transformation from vapor to mist

indicating that hunting behavior of TEV control-loop occurred

and the overall evaporator capacity decreased by 14.1%. The superheated refrigerant gas from Circuit 1 outlet only provided sensible heat and couldn't evaporate the liquid refrigerant out of Circuit 2 into superheated steam. Consequently

refrigerant in the evaporator overall outlet was of a smaller superheat than the necessary minimal stable signal (MSS) of the TEV

even at two-phase state

and would inevitably give rise to the hunting of the TEV -controlled system according to the MSS theory. These experimental results might provide references for the design of the heat exchanger of multi-circuit refrigerating system.