Modeling the discontinuous individual channel injection into fin-and-tube evaporators for residential air-conditioning

In this paper a working principle based upon the novel expansion and distributor device EcoFlowTM is analyzed.
The device enables compensation of flow maldistribution by control of individual channel superheat.
The working principle is discontinuous liquid injection (pulsating flow) into each individual channels during a
specified cycle time. Moreover, the influence of the injection cycle time is investigated together with an optional
secondary flow into the other channels with regards to cooling capacity, overall UA-value and COP.
The results showed spurious fluctuations in pressure when simulating the pulsating flow, thus the dynamic
behavior in the mixture two-phase flow model is insufficient to model the discontinuous liquid injection
principle. Despite, the fluctuations and imperfections of the model we found that the cycle time should be
kept as low as possible and that the optional secondary flow increases performance. Moreover, the paper reports
on the applicability of Modelica developed models to analyze and optimize the working principle and
design of expansion devices such that Modelica may be used in future development of novel discontinuous
expansion devices.