High heat flux dissipation using small diameter channels

Morris Brian Bowers, Purdue University

Abstract

Increased heat dissipation rates from electronic chips creates the need for high heat flux cooling schemes with a special emphasis on practical considerations such as pressure drop and flow rate. Devices such as fusion reactor components and rocket nozzles have heat dissipation rates of 10,000 W cm$\sp{-2}$ These heat fluxes are orders of magnitude greater than electronic devices, thus requiring ultra-high heat flux cooling schemes. In this thesis, a cooling technology is proposed where high heat fluxes are achieved by flow boiling in miniature heat sinks. High heat dissipation is achieved by forcing a boiling liquid through small channels that run through the heat sink. For boiling conditions, the limiting heat flux is the critical heat flux, CHF; however, flow boiling in small diameter channels offered an enhancement in CHF over most boiling configurations. Pertaining to electronic cooling applications, flow boiling of R-113 at low mass velocity in mini-channel (D = 2.54 mm) and micro-channel (D = 510 $\mu$m) heat sinks is presented as a practical cooling technology. Also, complimenting the experimental study, predictive tools for optimizing heat sink design based upon channel diameter, channel spacing, CHF pressure drop, and flow rate are developed and presented as a complete package for incorporating miniature heat sink technology into electronic cooling scheme design. For ultra-high heat flux applications, miniature heat sink technology is also proposed; however, flow boiling of water at high mass velocity is the choice of coolant. In order to adapt miniature heat sink technology for ultra-high heat flux applications, an experimental investigation of CHF for water in small diameter tubes was performed and predictive CHF correlations developed for two distinct parametric regions defined as high and low pressure regions. A complete design methodology for incorporating two-phase miniature heat sink technology into cooling scheme design is presented. ^

Degree

Ph.D.

Advisors

Major Professor: Issam Mudawar, Purdue University.

Subject Area

Engineering, Mechanical

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