Heat transfer and pressure drop characteristics of arrays of rectangular modules encountered in electronic equipment

This paper provides a review of thermoelectric cooling and its application to the cooling of electronic equipment. A background discussion of thermoelectric cooling is provided briefly citing early history, current developments, and the defining thermoelectric heat pumping equations. Several examples are provided of early IBM applications of thermoelectric cooling. An analysis to assess thermoelectric cooling enhancement in terms of increases in allowable power dissipation or chip temperature reduction is described along with results.

Application of thermoelectric cooling to electronic equipment: a review and analysis

The trend towards increasing heat flux at the chip and module level in computers is continuing. This trend coupled with the desire to increase performance by reducing chip operating temperatures presents a further challenge to thermal engineers. We will provide an assessment of the potential for module cooling enhancement with thermoelectric coolers. A brief background discussion of thermoelectric cooling is provided citing some of the early history of thermoelectrics as well as more recent developments from the literature. An example analyzing cooling enhancement of a multichip module package with a thermoelectric cooler is discussed. The analysis utilizes closed form equations incorporating both thermoelectric cooler parameters and package level thermal resistances to relate allowable module power to chip temperature. Comparisons are made of allowable module power with and without thermoelectric coolers based upon either air or water module level cooling

An Assessment of Module Cooling Enhancement With Thermoelectric Coolers

Natural convection heat transfer in annular fin-arrays mounted on a horizontal cylinder was experimentally investigated. An experimental set-up was constructed to investigate heat transfer characteristics of 18 sets of annular fin-arrays mounted on a horizontal cylinder of 24.9-mm diameter in atmospheric conditions. Keeping the fin thickness fixed at 1 mm, fin diameter is varied from 35 mm to 125 mm and fin spacing is varied from 3.6 mm to 31.7 mm. The base-to-ambient temperature difference was also varied with a calibrated wattmeter ranging from 25 W to 150 W. The results have shown that the convection heat transfer rate from the fin arrays depends on fin diameter, fin spacing and base-to-ambient temperature difference. In addition, for every fin diameter, for a given base-to-ambient temperature difference, there exists an optimum value for the fin spacing for which the heat transfer rate from the fin array is maximised. Experimental results show that, for practical engineering applications, the optimum fin spacing may be taken approximately as 8 mm. A scale analysis is also performed in order to estimate order-of-magnitude of optimum fin spacing at a given fin diameter and base-to-ambient temperature difference. The correlation obtained from scale analysis is the result of limited number of experiments. This correlation may be generalised by applying the order-of-magnitude analysis developed in this work for wider range of experiments.

An experimental investigation on performance of annular fins on a horizontal cylinder in free convection heat transfer

The stability of a viscous liquid film flowing under gravity down an inclined wall with periodic corrugations is investigated. A long-wave model equation valid at near-critical Reynolds numbers is used to study the film dynamics, and calculations are performed for either sinusoidal or rectangular wall corrugations assuming either a fixed flow rate in the film or a fixed volume of fluid within each wall period. Under the two different flow assumptions, steady solution branches are delineated including subharmonic branches, for which the period of the free surface is an integer multiple of the wall period, and the existence of quasi-periodic branches is demonstrated. Floquet-Bloch theory is used to determine the linear stability of steady, periodic solutions and the nature of any instability is analysed using the method of exponentially weighted spaces. Under certain conditions, and depending on the wall period, the flow may be convectively unstable for small wall amplitudes but undergo transition to absolute instability as the wall amplitude increases, a novel theoretical finding for this class of flows; in other cases, the flow may be convectively unstable for small wall amplitudes but stable for larger wall amplitudes. Solutions with the same spatial period as the wall become unstable at a critical Reynolds number, which is strongly dependent on the period size. For sufficiently small wall periods, the corrugations have a destabilizing effect by lowering the critical Reynolds number above which instability occurs. For slightly larger wall periods, small-amplitude corrugations are destabilizing but sufficiently large-amplitude corrugations are stabilizing. For even larger wall periods, the opposite behaviour is found. For sufficiently large wall periods, the corrugations are destabilizing irrespective of their amplitude. The predictions of the linear theory are corroborated by time-dependent simulations of the model equation, and the presence of absolute instability under certain conditions is confirmed. Boundary element simulations on an inverted substrate reveal that wall corrugations can have a stabilizing effect at zero Reynolds number.

Abhay A. Wative

Papers

Cooling Electronic Equipment

Cooling Electric Equipment