It is reasonable to use a two-phase heat transfer loop (TPL) in a thermal control
system (TCS) of spacecraft with large heat dissipation. One of the key
elements of TPL is a heat-controlled accumulator (HCA). The
HCA represents a volume which is filled with vapor and liquid of a single
working fluid without bellows. The pressure in a HCA is controlled by the
heater.
The heat and mass transfer processes in the HCA can proceed with a significant
nonequilibrium. This has implications on the regulation of TPL. This article
presents a mathematical model of nonequilibrium heat and mass transfer processes
in an HCA for microgravity conditions. The model uses the equations of mass and
energy conservation separately for the vapor and liquid phases. Interfacial heat
and mass transfer is also taken into account. It proposes to use the convective
component k for the level of nonequilibrium evaluation.
The experiments were carried out in microgravity conditions for the estimation of
the k value. The heating of the HCA was investigated in the
flight experiments. The working fluid was ammonia. It was determined that in the
mathematical model, the k low margin is k =
15…30 for the microgravity conditions.
An analysis of the HCA regulation was performed for two values of the
k coefficient. It defined that nonequilibrium has a
significant impact on the regulation process. It is shown that to ensure a given
mode of TPL operation with the HCA equilibrium process (k >
100), a greater HCA heater power is required than in a nonequilibrium process
(k = 30).
