Iranian Research Organization for Science and Technology Journal of Particle Science and Technology 2423-4087 12 1 2026 06 01 Extending the allowable exposure time of rotating X-ray anodes via an embedded lithium pulsating heat pipe: A 3D multiphase analysis 1 20 1691 10.22104/jpst.2026.8247.1291 EN Mohsen Amini Department of Mechanical Engineering, University of Sistan and Baluchestan, Zahedan, Iran Faramarz Sarhaddi Department of Mechanical Engineering, University of Sistan and Baluchestan, Zahedan, Iran 0000-0002-5216-9823 Hassan Azarkish Department of Mechanical Engineering, University of Sistan and Baluchestan, Zahedan, Iran Journal Article 2026 05 13 Thermal management of high-power X-ray rotating anodes is strictly constrained by the intense, localized heat fluxes generated during brief exposure times. This study proposes the integration of a lithium-based rotating pulsating heat pipe (RPHP) into the anode and investigates its transient thermal-hydraulic performance using a volume of fluid (VOF) multiphase model, which is heavily influenced by both extreme centrifugal forces and the intense heat flux applied during the exposure time. The results reveal a fundamental thermodynamic trade-off governing the optimal rotational speed: while higher rotational speeds enhance internal fluid circulation as well as latent and sensible heat transport, they simultaneously generate massive hydrostatic pressures that cause a significant transient delay in the phase-change (boiling) process. Consequently, the maximum allowable exposure time exhibits a non-monotonic dependence on the rotational speed. A case study based on the RAD-14 X-ray tube was investigated with a heat input of 20 kW on a minimum focal spot size (0.3 mm). A critical temperature limit of 2200 K was defined to evaluate and compare the allowable exposure times across different configurations. Compared to a conventional solid anode (which is limited to an exposure time of 0.436 s), the RPHP integration at 8500 rpm achieves optimal thermal performance, extending the allowable exposure time to 0.706 s (a 62 % increment). However, further increasing the speed to 10000 rpm exacerbates the pressure-induced boiling retardation, leading to an exposure time of 0.619 s (a 42 % increment relative to the solid base, but a 12 % reduction compared to the 8500 rpm peak). https://jpst.irost.ir/article_1691_8303a79b1e19a194f1875981be5bdb6f.pdf