Suchergebnisse

Reprinted from Journal of Atmospheric Sciences, Vol. 23, No. 6, pp. 678-681, November 1966. ; Research supported by the Air Force Cambridge Research Laboratories, Office of Aerospace Research, United States Air Force, L.G. Hanscom Field, Bedford, Massachusetts. ; Meteorology Laboratory Project 7655. ; "February 1967." ; Includes bibliographical references. ; Mode of access: Internet.

Non-linear temperature profiles caused by temperature-dependent thermal conductivity l(T) of wall materials are discussed. Instead of conventional thermal resistance, modified effective resistance has been introduced.

The design of a thermal regenerator is initially carried out by considering the fundamental influencing variables. For novel solid-state cooling systems using active caloric regenerators, the non-linearity of the coupled phenomena of material properties, heat transfer, and hydraulic flow can complicate the interpre- tation of experimental and simulated results. Based on the boundary conditions of a sinusoidal magnetic field and fluid flow, we elucidate the operation of active regenerators by deriving easy-to-manage analyt- ical expressions for the temperature transients of the caloric materials and heat transfer fluid. An internal temperature measurement system with an estimated uncertainty of ±0.3 K for packed bed regenerators has been developed for validation. The derived expressions have acceptable accuracy relative to the exper- imental and numerical results for temperature profiles in both magnitude and sensitivity, where average and maximum errors are ∼10% and ∼15%, respectively. Useful figures of merit are post-calculated using the derived temperature profiles. We found that the average temperature profiles are linear for passive regenerators and nonlinear for active regenerators, and their transients are nonlinear functions of the configuration and operating parameters. ; This work was in part financed by the RES4Build project, which received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 814865. The authors wish to acknowledge Dr. Kaspar K. Nielsen for the valuable discussions of the experimental setup.

When light water reactor (LWR) is subject to a cold shutdown, it needs to be cooled with pure water or seawater to prevent the core melting. To precisely evaluate the cooling characteristics in the fuel assembly, a measurement method capable of installing to the fuel assembly structure and determining the temperature distribution with high temporal resolution, high spatial resolution, and in multidimension is required. Furthermore, it is more practical if applicable to a pressure range up to the rated pressure 16 MPa of a pressurized water reactor (PWR). In this study, we applied the principle of the wire-mesh sensor technology used in the void fraction measurement to the temperature measurement and developed a simulated fuel assembly (bundle) test loop with installing the temperature profile sensors. To investigate the measurement performance in the bundle test section, it was confirmed that a predetermined temperature calibration line with respect to time-average impedance was calculated and became a function of temperature. To evaluate the followability of measurement in a transient temperature change process, we fabricated a 16 × 16 wire-mesh sensor device and measured the hot-water jet-mixing process into the cold-water pool in real time and calculated the temperature profile from the temperature calibration line obtained in advance from each measurement point. In addition, the sensors applied to three-dimensional temperature distribution measurement of a complex flow field in the bundle structure. The axial and cross-sectional profiles of temperature were quantified in the forced flow field with nonboiling when the 5×5 bundle was heated by energization.

Abstract
Paleo-temperature reconstruction from precise depth (>2.0 km) well temperature logs can offer information on whether the bed of an ice sheet was frozen. Inversion or upward extrapolation of the >2-km-deep geothermal profile is the only method by which temperature evolution at the base of long-disappeared ice sheets such as the Laurentide and Fennoscandian in the northern part of the Northern Hemisphere in North America and Europe can be inferred. It is obvious from the results from well temperature profiles that there were spatial variations in temperature at the base of the ice sheets during glaciations. This comes as no surprise, since modern-day measurements of temperature profiles through the ice of existing glaciers show a similarly large variability. Present bedrock temperatures measured beneath the central part of the Yukon Rusty glacier are near 0°C to -2°C while Greenland ice sheet base temperatures are -8 and -13°C. In case of very low paleo-temperatures derived from the interpretation of temperature profiles in the areas presently outside the current extent of glacial ice it can be shown that low temperature conditions under glacial ice could facilitate the existence of moderate (some 100-200 m) to thick (0.5 km-1 km) permafrost conditions. It is speculated here that, in many cases, paleo-glacial cold base ice could have existed right on top of paleo-permafrost in sediments just below. Such ice-bonded permafrost may have been frozen to glacial ice above, forming pillars which fixed glacial ice to permafrost below, thus limiting ice movement in such places and resulting in the -extended persistence of permafrost.

In order to simulate the CANDU-6 moderator circulation phenomena during steady state operating and accident conditions, a scaled-down moderator test facility has been constructed at Korea Atomic Energy Institute (KAERI). In the present work an experiment using a 1/40 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a flow field is visualized with a particle image velocimetry (PIV) technique under an isothermal state, and the temperature field is measured using a laser induced fluorescence (LIF) technique. A preliminary CFD analysis is also performed to find out the flow, thermal, and heating boundary conditions with which the various flow patterns expected in the prototype CANDU-6 moderator tank can be reproduced in the experiment.

Greater Hyderabad a twin city in earlier days, has grown into a tricity of Cyberabad - Hyderabad – Secunderabad. This concentrated development with impetus on industrialization has led to unprecedented urbanization and sprawl, resulting in heavy population growth and ultimately raising serious challenges such as traffic congestion, enhanced Green House Gas (GHG) emissions causing climatic changes apart from over-use of basic amenities and infrastructure. This study shows that urban areas have grown from a mere 172 sq km of MCH (Municipal Corporation of Hyderabad) in the 1970's to a whopping 1905 sq km at present, currently known as the Greater Hyderabad Metropolitan Corporation. The phenomenon of Urban Heat Island (UHI) can be observed in several localities. The pattern of growth of Greater Hyderabad and its repercussions on the local climate are studied with the help of geospatial technologies. An increase of ~20C to 2.50C is observed over the last 2 decades. The Vegetation and water bodies also show a sharp decline.

The knowledge of dynamic thermal properties of building elements is necessary to investigate temperature and heat flux changes in natural daily and annual cycles. The basic dynamic parameter is thermal diffusivity. A method for determining its value for real objects has been proposed. This method is based on measuring the temperature in the element's volume and on assuming that the obtained results meet the Fourier equation. Validation by a numerical experiment was made. The wall of the building with known thermal parameters was assumed and the temperature distribution was calculated over time in the process of non-stationary heat exchange. From the results, the diffusivity value was calculated and compared with the data entered into the model. Validations were performed for several accuracy of the temperature value and for two forms of function which approximated the temperature values obtained from calculation. A preliminary analysis of errors has been carried out.
Keywords: measurements of thermal diffusivity, temperature distribution in a building element, approximation, heat transfer