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. Summary Table of Contents. 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.
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The Data Item document you have requested is available only to subscribers or purchasers. ESDU Heat pipes - performance of two-phase closed thermosyphons. Summary 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. Advice and expressions are also given for the limits of vapour pressure, sonic velocity in the vapour, dry-out, boiling limit, and the counter-current flow limit.
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Heat Pipes - Performance of Two-phase Closed Thermosyphons. 81038
The heat pipe is a sealed system containing a liquid, which when vaporized transfers heat under isothermal conditions. The temperature of the vapor corresponds to the vapor pressure, and any temperature variation throughout the system is related directly to vapor pressure drop. The choice of liquid charge is related to the required operating temperature range of the heat pipe. In the case of the elementary pipe design, liquid returns from the condenser via a wick structure. The wick is designed to provide a capillary pumping action, as described below. The heat pipe is a development of the thermosyphon , in which there is no wick structure and liquid is returned to the evaporator by gravity.