TITLE:
A Steady-State Evaluation of Simple Organic Rankine Cycle (SORC) with Low-Temperature Grade Waste Heat Source
AUTHORS:
Ali H. Tarrad
KEYWORDS:
Organic Rankine Cycle, Low Temperature, Waste Heat Source, Thermal Analysis
JOURNAL NAME:
Journal of Power and Energy Engineering,
Vol.8 No.7,
July
30,
2020
ABSTRACT: The
low-grade heat source recovery is usually constrained by the physical
characteristics of the hot fluid medium. The present work focuses on the
importance of energy recovery from
low-temperature waste energy sources and its conversion to useful electrical
power. The thermal performance analysis is based
on the utilization of R-123, R-134a, R-290, R-245fa, R-1234ze-E, and R-1233zd-E fluids in a simple organic Rankine cycle (SORC). A waste
energy source from an industrial sector is suggested to be available at a
temperature greater than 110 °C. A hypothetical organic Rankine cycle of 10 kW
nominal heat recovery was implemented to evaluate the cycle performance. It
operates at evaporation and condensation
temperatures of 90 °C and 45 °C, respectively. The selected vapor
superheat degree at the expander entrance was 5 °C - 15 °C, and the liquid was
subcooled by 5 °C at the discharge port of condenser. The estimated first law
cycle thermal efficiency fell in the range of 6.4% - 7.7%. The results showed
that the thermal efficiencies of R-134a, R-123, R-245fa, R-1233zd-E, and
R-1234ze-E were higher than that of R-290 by 10% - 14%, 11% - 12%, 9% - 12%, 4%
- 7% and 1% - 3%, respectively. R-1233zd-E, R-1234ze-E, and R-290 showed close thermal efficiency
values, and it fell in the range of 6.7% - 7% for the (SORC) at a superheat
degree of 15 °C. At the same superheat degree, the corresponding range of
thermal efficiency for R-134a, R-123 and R-245fa fell within 7.5% - 7.7%.
R-134a possessed the highest net power output of the (SORC); it reached a value
of 0.91 kW as predicted at 15 °C superheat degree. Increasing the expander
volumetric efficiency value by 10% improved the cycle thermal efficiency by 10%
- 12%.