In this paper we compare a recently proposed two-phase thermofluidic
oscillator device termed ‘Up-THERM’ to a basic
(sub-critical, non-regenerative) equivalent organic Rankine cycle
(ORC) engine. In the Up-THERM heat converter, a constant
temperature difference imposed by an external heat source and
sink leads to periodic evaporation and condensation of the working
fluid, which gives rise to sustained oscillations of pressure
and volumetric displacement. These oscillations are converted
in a load arrangement into a unidirectional flow, which passes
through a hydraulic motor that extracts useful work from the device.
A pre-specified Up-THERM design is being considered in a
selected application with two n-alkanes, n-hexane and n-heptane,
as potential working fluids. One aim of this work is to evaluate
the potential of this proposed design. The thermodynamic comparison
shows that the ORC engine outperforms the Up-THERM
heat converter in terms of power output and thermal efficiency,
as expected. An economic comparison, however, reveals that the
capital costs of the Up-THERM are lower than those of the ORC
engine. Nevertheless, the specific costs (per unit power) favour
the ORC engine due to its higher power output. Some aspects of
the proposed Up-THERM design are identified for improvement.
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.