An innovative system for feeding once-through evaporators in flooded conditions

In this paper an innovative feeding system for once-through flooded evaporators is presented and experimentally analysed. The mentioned system consists of an electronically operated expansion valve and a small liquid separator placed at the evaporator exit, equipped with a level indicator. The basic idea is to get the control signal for the expansion device from the liquid level in the separator. An additional internal heat exchanger must follow the evaporator to prevent any liquid from flowing back to the compressor. The proposed solution retains the benefits of flooded evaporation, without the need for liquid recirculation, thus keeping the simplicity and flexibility of the systems equipped with thermostatic valves. It is suitable both for single evaporator and multi-evaporators lay-out. To verify the potentialities of the proposed solution, a simple algorithm has been developed to control the valve. The first experimental results have shown the ability of the system to keep stable operations of the evaporator under flooded conditions. The comparison with a dry-expansion circuit has shown large potential of energy saving