tailieunhanh - Heat Transfer Handbook part 38

Heat Transfer Handbook part 38. 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. | JOINT CONDUCTANCE ENHANCEMENT METHODS 361 Figure Gap conductance model and data for conforming rough Ni 200 surfaces. From Song 1988. 200 surfaces. The plastic deformation model was used to calculate Y. The points for M correspond to the high-gas-pressure tests near 1 atm and the points for M 2 correspond to the low-gas-pressure tests. JOINT CONDUCTANCE ENHANCEMENT METHODS In many electronics packages the thermal joint conductance across a particular joint must be improved for the thermal design to meet its performance objectives. If the joint cannot be made permanent because of servicing or other considerations. the joint 362 THERMAL SPREADING AND CONTACT RESISTANCES Figure Dimensionless gap conductance model and data for conforming rough Ni 200 surfaces. From Song 1988. conductance must be enhanced that is it must be improved above the bare joint situation utilizing one of several known techniques such as appiicaiion of thermal interface materials TIMs for example thermal grease grease filled with particles also called paste oils and phase-change materials PCMs . Enhancement of the joint conductance has also been achieved by the insertion of soft metallic foils into the joint or by the use of a i eaitV ty soft metallic coaling nn one or bthh surfaces .More recently soft nonmetallic materials such as polymers and rubber have been used. One may consult review articles by Fletcher 1972 1990 Madhusudana and Fletcher 1986 Madhusudana 1996 Marotta and Fletcher 1996 Prasher 2001 Savija et al. 2002a b and other pertinent references may be found in these reviews. This section is limited to a few examples where models and data are available. JOINT CONDUCTANCE ENHANCEMENT METHODS 363 Metallic Coatings and Foils An effective method for enhancement of joint conductance consists of vapor deposition of a very thin soft matallic layer on surface of the substrate. Tire layer thickness is often less than 100 m it is in perfect thermat and mechanicat

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