A miniature-scale refrigeration system for electronics cooling
Thermal management of electronics is a critical issue that is increasingly gaining importance in line with the advances in packaging technology. Alternate chip cooling techniques are being investigated in the literature with vapor compression refrigeration being one of the methods to replace conventional air cooling. ^ This study presents a new advanced and experimentally validated numerical model to predict the performance of a Miniature-Scale Refrigeration System (MSRS) for electronics cooling. The system model consists of four main components: an integrated microchannel cold plate evaporator-heat spreader, a compressor, a microchannel condenser, and an expansion device. The simulation model was developed based on thermodynamic and heat transfer control volume approaches and a segment-by-segment analysis was employed to estimate the condenser and evaporator heat transfer rates and pressure drops. The mass flow rate and power consumption of the compressor were predicted by using the ARI standard (1999) and Klein method (2000) while an isenthalpic process was assumed for the expansion device. A charge calculation was also included in the model to calculate the refrigerant distribution and the total charge in the system. ^ The simulation model was verified using experimental data that were collected with a bread board system assembled in the Ray W. Herrick Laboratories at Purdue University. The experimentally values of cooling capacity and COP were predicted to within ±20% (standard deviation of 12.0%) and ±30% (standard deviation of 15.2%), respectively, by the model. These deviations between predictions and measurements arise mainly from the mass flow rate predictions using the compressor map. ^ The simulation model is considered a valid predictive tool since the model can be used to predict the system performance within acceptable accuracy. It can be used to evaluate the system performance resulting from variations of the component designs and of the operating conditions of the system. A parametric study is presented and design guidelines and recommendations are proposed. An optimum heat spreader thermal conductivity of 2000 W/m-K for a heat spreader thickness of 3 to 4 mm is suggested. A cold plate evaporator microchannel length of 30 mm is recommended to achieve low overall system thermal resistance. ^
Eckhard A. Groll, Purdue University, Suresh V. Garimella, Purdue University.