Document Abstract: ESDU explains the various mechanisms producing high winds, such as depressions, thunderstorms, tropical storms and tornadoes, and describes their characteristics and geographical occurrence. Detailed procedures are given for analysing annual and storm maxima records and for analysis by direction. The Lieblein method of fitting the maxima with a Fisher-Tippett Type 1 distribution is detailed and an alternative method of predicting extreme values from the parent probability distribution function of Weibull form is provided and allows good estimates of extreme speeds to be obtained from relatively short records. Methods of analysing and synthesising data when more than one storm mechanism contributes to the extremes are included. Methods are recommended for extrapolating extreme values for depressions, thunderstorms or tropical storms to heights and terrain roughnesses different from those at the measurement site. To assist in the analysis of historical wind speed records, types of anemometers used and their possible inaccuracies are discussed.
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This module, which runs in Excel 97 or later, can be used to estimate the variation of wind speed and turbulence properties with height in the atmospheric boundary layer.
The module brings together the relevant methods for estimating the effects of terrain roughness changes, gust averaging time and topography hills, valleys, etc. The spreadsheet presentation facilitates repeat runs with changes to the input.
The facility is also available to reduce or correct measured wind properties such as those from a local met. The program will calculate wind properties as a function of height over the site including hourly-mean wind speed and maximum gust speed, together with properties of the longitudinal u and lateral v and w components of turbulence intensities, integral length scales and spectral densities.
The program takes into account the following local conditions. Ground roughness at the site and variations in ground roughness upwind of the site including lateral variations in a terrain patch and the variation of sea-surface roughness with wind speed.
Topographic effects on wind speed due to the location of the site in a hilly region, including ridges, embankments, escarpments or cliffs, or in a valley; topographic effects on turbulence properties for flow over hills with no flow separation. A major feature of the program is its ability to deal with sites in complex terrain where the site is located within a range of hills. The general effect of topography is based on the two-dimensional computational method of Deaves but extended to include three-dimensional effects.
The program incorporates a means of dealing with steep topography where flow separations occur and also a simplified model for estimating the distortion of spectra and turbulence variances over a hill. Indexed under:.
Table of Contents Methods and data are presented for use by the process plant engineer, design engineer or consultant dealing with the evaluation or prediction of the performance of heat transfer equipment and the costing of heat exchangers. The Sections give step-by-step calculation methods and indicate the limits of applicability and the limits of accuracy of empirical correlations. Many of the methods are presented in a form readily adaptable to computer implementation. The following topics are covered in this Series: Single-phase forced and free convection in straight, annular and coiled tubing, together with the pressure loss and heat transfer resulting from tube inserts and roughened surfaces. Forced convection over cylinders and tube banks and free convection and radiation from simple shapes. Heat pipe design and performance prediction and the selection of appropriate temperature measuring devices and the requirements for refractory lining materials are also treated. Heat exchanger selection and costing, performance and design.
Dar The thermosyphon consisted of a 0. These results compare well with the predicted values found using a calculation procedure presented by Engineering Services Data Unit, Item No. Degree Grantor University of Canterbury. A point is reached when temperature difference exceeds the degree of superheat sustainable in relation to nucleate boiling conditions. The boiling limit occurs when a esxu vapor film is formed between the liquid and the evaporator wall. It gives equations for calculating the effective thermal conductivity, minimum capillary radius and permeability of a wide range of wicks for use in capillary-driven heat pipes including single-layer and multiple-layer wire mesh, unconsolidated packed particles and sintered felted metal fibres. Heat and Mass Transfer16, At low temperature range operation of the working fluid, especially at start-up of the heat pipe, the minimum pressure at the condenser end of the pipe can be very small.
Using this characteristic dimension they have produced a table showing the degree of superheat for a range of candidate heat pipe working fluids, including ammonia, water eddu liquid metals for high temperature operation. The reactor vessel would be fed with water through porous dispenser tubes. The use of a simple wick in the evaporator was found to hinder heat transfer. The viscous and sonic limits are the same as for wicked heat pipes and the equation for the boiling limit and countercurrent flow limits are summarized below. It gives equations for calculating the effective thermal conductivity, minimum capillary radius and permeability of a wide range of wicks for use in capillary-driven heat esd including single-layer and multiple-layer wire mesh, unconsolidated packed particles and sintered felted metal fibres. The Data Item document you have requested is available only to subscribers or purchasers. Nucleation sites, at which bubbles first form, are provided by scratches or rough surfaces and esduu the release of absorbed gas.
ESDU Heat Transfer Series
Document Abstract: The physical processes involved in a thermosyphon, whereby high rates of heat transfer can be obtained between surfaces that have only a small temperature difference between them, are described. Heat is transferred by means of evaporation and condensation, and gravity is used to return the liquid film to the evaporator as compared with capillary-driven designs which use a wick as described in ESDU ESDU relates to thermosyphons having i circular tubes of uniform cross section, ii a single component working fluid and no non-condensable gas, iii either no wick or a simple wick or insert in the evaporator wall and iv angles of inclination to the horizontal of 5 degrees to 90 degrees. The maximum overall rate of heat transfer depends on the overall temperature difference and the sum of the thermal resistances of the various solid, liquid and vaporous media and interfaces involved. Methods are given for calculating each thermal resistance.