A review on boiling heat transfer enhancement with nanofluids

There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement

Analytical expressions for stopping-power ratios relevant for accurate dosimetry in particle therapy

In particle therapy, knowledge of the stopping-power ratios (STPRs) of the ion beam for air and water is necessary for accurate ionization chamber dosimetry. Earlier work has investigated the STPRs for pristine carbon ion beams, but here we expand the calculations to a range of ions (1 <= z <= 18) as well as spread out Bragg peaks (SOBPs) and provide a theoretical in-depth study with a special focus on the parameter regime relevant for particle therapy. The Monte Carlo transport code SHIELD-HIT is used to calculate complete particle-fluence spectra which are required for determining STPRs according to the recommendations of the International Atomic Energy Agency (IAEA). We confirm that the STPR depends primarily on the current energy of the ions rather than on their charge z or absolute position in the medium. However, STPRs for different sets of stopping-power data for water and air recommended by the International Commission on Radiation Units & Measurements (ICRU) are compared, including also the recently revised data for water, yielding deviations up to 2% in the plateau region. In comparison, the influence of the secondary particle spectra on the STPR is about two orders of magnitude smaller in the whole region up till the practical range. The gained insights enable us to propose an analytic approximation for the STPR for both pristine and SOBPs as a function of penetration depth, which parametrically depend only on the initial energy and the residual range of the ion, respectively.Comment: 21 pages, 5 figures, fixed bug with figures in v

Peaks of Identity in Colorado’s San Juan Mountains

The glaciated ranges of southwestern Colorado constituting the San Juan Mountains are culturally significant to residents and visitors. As certain mountains are imbued with meaning, they become "peaks of identity," tangible and towering symbolic landscapes representing a distinctive set of community and cultural ideals. This paper explores the symbols and themes of San Juan peaks of identity, with a focus on the mountain amenity town of Lake City and nearby Uncompahgre Peak. Uncompahgre's icon dominates mountain representations in Lake City and instantly identifies the community; its symbolism embodies aesthetics of form and elevation and the sanctity of hallowed ground. Mountain symbolism in the San Juans is mainly projected through land use and the display of icons and names on signs and government seals. Although the San Juans are sacred to the Utes and Navajos and represent a rich mining heritage, they also symbolize idealized natural scenery, landmarks of home, recreation opportunities, and spiritual renewal. Many San Juan communities identify with mountains in a generic sense, but this article focuses on the traits, variability, and depth of meaning of the mountains that are landscape signatures of community identity