A New Experiment for Investigating Evaporation and Condensation of Cryogenic Propellants.

Passive and active technologies have been used to control propellant boil-off, but the current state of understanding of cryogenic evaporation and condensation in microgravity is insufficient for designing large cryogenic depots critical to the long-term space exploration missions. One of the key factors limiting the ability to design such systems is the uncertainty in the accommodation coefficients (evaporation and condensation), which are inputs for kinetic modeling of phase change. A novel, combined experimental and computational approach is being used to determine the accommodation coefficients for liquid hydrogen and liquid methane. The experimental effort utilizes the Neutron Imaging Facility located at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland to image evaporation and condensation of hydrogenated propellants inside of metallic containers. The computational effort includes numerical solution of a model for phase change in the contact line and thin film regions as well as an CFD effort for determining the appropriate thermal boundary conditions for the numerical solution of the evaporating and condensing liquid. Using all three methods, there is the possibility of extracting the accommodation coefficients from the experimental observations. The experiments are the first known observation of a liquid hydrogen menisci condensing and evaporating inside aluminum and stainless steel cylinders. The experimental technique, complimentary computational thermal model and meniscus shape determination are reported. The computational thermal model has been shown to accurately track the transient thermal response of the test cells. The meniscus shape determination suggests the presence of a finite contact angle, albeit very small, between liquid hydrogen and aluminum oxide.

Diversity of avifauna of Jamwa Ramgarh wetland of Rajasthan in India.

The present paper deals with the rich avifauna available at Jamwa Ramgarh Lake of Rajasthan in India. More than 100 species of birds belonging to 38 families were recorded at lake during the year 2002, maximum species were sighted during the winter season. Due to scanty rainfall in 2002, this lake was also affected and had only one-fourth of water of its total capacity, which affected the numbers of migratory waterfowl also. In the wetland most water birds were found to be migratory and few being resident. Some rare, endangered, uncommon, vulnerable, threatened and near threatened species of birds those already listed in Red Data Book were sighted.