Fig. 1
NIFTE fluid pump schematic, adapted from Reference [25]. Configuration. A NIFTE consists of four major elements: the displacer cylinder ā that contains the hot ā and cold ā heat-exchangers; the adiabatic vapor region ā; the power cylinder ā that is connected to the load ā; and the feedback connection tube ā . The white area denotes the vapor phase, while the grey area denotes the liquid phase of the working fluid. Operational cycle. Low-grade heat from an external source is supplied to the system via the hot heat-exchanger (HHX) ā to vaporize the working fluid. The pressure in the adiabatic vapor region ā thus increases, causing the liquid level ā in the power cylinder ā to fall below the equilibrium level. The liquid level ā in the displacer cylinder ā drops as a result of the hydrostatic pressure via the feedback connection ā . The vapor comes into contact with the cold heat-exchanger (CHX) ā, where heat is removed from the system, causing the vapor to condense and the liquid height to rise back above the equilibrium position. Sustained oscillations in the load ā are thereby created by the cyclic condensation and evaporation of the working fluid in the cylinders