Absorption and Conversion of Sensible Heat and Solar Radiation into Mechanical Work Using a Self-Pumping Capillary Thermal Engine with Passive Cooling Potential
Year: 2026
Type: preprint
Abstract: This paper proposes a self-pumping capillary thermal engine that absorbs solar radiation and sensible heat with a spectrally selective absorber and converts part of it into mechanical work through the evaporation and condensation of a low-boiling organic fluid, while a capillary wick returns the liquid to the evaporator without a mechanical pump. The performance is analysed for the climate of Khartoum using hourly NASA POWER data for 2025 and fluid properties from CoolProp. For an evaporator at 75 °C and a condenser at 45 °C the Carnot limit is about 8.6%, and the estimated mechanical power is 1.5-2.8 W per 0.1 m2 at solar noon. The annual mean daily output is 7.9-14.5 Wh per 0.1 m2 (79-145 Wh m-2 per day), with a stable output throughout the year. A comparison of R1233zd(E), n-pentane and ethanol shows similar power but very different maximum wick pore radii (0.05, 0.11 and 0.52 µm), which emerges as the governing design constraint. A second operating mode with an evaporator near 50-55 °C is described for cooling photovoltaic panels and machines, and the thermodynamic limits of heat rejection and routes toward higher efficiency are discussed. The results are numerical and no experiments are reported.
Authors: Alshaikh, Alshaikh, Mohamed Nasir Ali
Institution: University of Khartoum
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225465124