TAILIEUCHUNG - Heat Transfer Handbook part 120

Heat Transfer Handbook part 120. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | INTRODUCTION 1187 The axially grooved wick shown in Fig. possesses highly conductive metal paths for the minimization of radial temperature drop. Axially grooved heat pipes are most commonly found in space applications. The annular and crescent wicks shown respectively in Fig. and e have small resistance to liquid flow but are vulnerable to liquids of low thermal conductivity. The artery wick shown in Kg. was developed to reduce the thickness of the ti heat flow path through the structure and to provide a low-resistance path for the liquid flow from the condenser to the evaporator. However these wicks often lead to operating problems if they are not self-priming because the arteries must fill automatically at startup or after a dryout. All the composite wicks shown in Fig. have a separate structure for development of flee caplllary f rcj surc and Equid f oy. Notice fliat m sime ot hhe . in Fig. a separation ofthe heat flow path from the liquid flow path can be provided. For example the screen-covered groove wick shown in Fig. has a fine mesh screen for high capillary pressure axial grooves to reduce flow resistance and a metal structure to reduce the radial temperature drop. The slab wick displayed in Fig. is inserted into an internally threaded container. High capillary pressure is derived from a layer of fine mesh screen at the surface and liquid flow is assured by the coarse screen inside the slab. The threaded grooves tend to provide uniform circumferential distribution of liquid and enhance radial heat transfer. Classification by Type of Control In addition to classification by the temperature range of the workmg Amd h t jip s may be classified by the type of conttol employed. C onurol is often hehessery benuee a heat pipe without control will self-adjust its operating temperature in accordance with the heat source at the evaporator end and the heat sink at the condenser end. For example it may be .

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