In this paper we address the high level of validation of commercially available numerical predictive tools, namely CFD models, for data center applications. Experimental data at a real world facility is compared with computational results. Specifically, a recently developed temperature measurement tool is used to capture three dimensional temperature profiles of the facility with very fine spatial granularity. These detailed contours based on actual measurements reveal hot air recirculation patterns in the room as well as variable utilization levels of the room air-conditioning units. We compare these experimental temperature distributions measured using a novel 3D mapping tool with CFD thermal modeling results. An algorithm for generating CFD models for real world systems is proposed and demonstrated. It is found that due to the extensive inaccuracies in rapidly gathered input data as well as inherent limitations of the model, there can be significant discrepancies between predicted and actual temperatures. In addition to steady state measurements, transient data was also collected and are presented. Knowledge of the transient temperature profiles at different parts of the room allows an estimation of the temporal behavior of the data center. Transient temperature fluctuations are presented which capture the real variations in the system boundary conditions, for example the temperature of the chilled water to the air conditioning units, or the power dissipation of the servers over time.
Practical concentrator photovoltaic systems operating at high solar concentration levels up to 2000 suns experience large thermal and electrical loads in addition to large power density transients under routine operation. These systems require efficient cooling systems to manage the associated incident power densities up to 200 W/cm 2 . Photovoltaic cells and thermal interface materials experience considerable stress under these load conditions. Reliability data is sparse for operation above 500 suns. We present high power test results for a commercial triple junction cell cooled through a high performance metal thermal interface using active liquid cooling methods for power densities up to 200 W/cm 2 .
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