Annual Energy Outlook 2008 With Projections to 2030

A review of the performance of different ventilation and airflow distribution systems in buildings

A Review on efficient thermal management of air- and liquid-cooled data centers: From chip to the cooling system

http://plaza.ufl.edu/siddgoya/Homepage/Publications_files/12_Applied_Energy_Control.pdf

Occupancy-based zone-climate control for energy-efficient buildings: Complexity vs. performance

The continuous growth in size, complexity and energy density of data centres due to the increasing demand for storage, networking and computation has become a worldwide energetic problem. The emergent awareness of the negative impact that the uncontrolled energy consumption has on natural environment, the predicted limitation of fossil fuels production in the upcoming decades and the growing associated costs have strongly influenced the energy systems engineering work in the last decades. Therefore, the implementation of well known and advanced energy efficiency measures to reduce data centres energy demand play an important role not only to a supportable growth but also to reduce its operational costs. The carbon footprint is greatly influenced by the energy sources used. Therefore, there have been recent efforts to exploit and reuse or combine green energy sources in data centres to lower brown energy consumption and CO2 emissions. This paper presents a comprehensible overview of the current data centre infrastructure and summarizes a number of currently available energy efficiency strategies and renewable energy integration into data centres and its characterization using numerical models. Moreover it would be necessary to develop dynamic models and metrics for properly understand and quantify the energy consumption and the benefits of applying the incoming energy efficiency strategies and renewable energy sources in the data centres. Thus, the researches or investors will be able to compare with reliability the different data centre designs and choose the best option depending on the renewable energy sources and capital available.

Energy efficiency and renewable energy integration in data centres. Strategies and modelling review

Experimental investigation of reduced-mixing personal ventilation jets

Current CFD simulation studies of large data centers cannot model the detailed geometries of the perforated tiles due to grid size limitation. These studies often assume that the tile flow can be modeled as constant velocity based on a fully open tile. In this case, mass flux is enforced at the expense of under-predicting momentum flux; the error in momentum flux can be as high as a factor of four for a 25% open perforated tile. Since jet entrainment is a strong function of its initial momentum flux, this error can be significant with respect to predicting the mixing of the surrounding room air into the tile flow. Combined experimental and computational studies were carried out to quantify the importance of the detailed tile geometry, and it was found that proper prediction of the mixing process must account for the tile opening patterns. Suggestions of how to model the floor perforated tiles in data center CFD simulations are then presented.

Experimental and computational study of perforated floor tile in data centers

An improved CFD model is presented to predict the thermal field in a small data center test cell. CFD analysis reported in an earlier paper [19] tended to exaggerate hot and cold spots in a small data center test cell as a result of the inability of the CFD model to predict the correct level of mixing of the cold air emanating from the perforated floor tiles and the warmer room air. The same can be said about the mixing of the hot air stream exiting the rack and the surrounding room air. The overall RMS error in the earlier study was 4°C between numerical results and test data. Another indication of low mixing in the CFD results is illustrated in the comparison of the temperature profile along a vertical line in front of the rack between CFD results and test data. While the temperature of the cold flow from the under floor plenum entering the data center was measured to be 12.8°C, temperature measurement at the same location via a temperature mapping tool showed that it is 15°C at 6" above the floor and rising quickly to 17°C at a height of 4 ft. The present investigations yield several improvements to the CFD model, including modeling of the perforated tile flow and rack exhaust flow to conserve both mass and momentum, inclusion of the effects of buoyancy, and an improved thermal boundary condition for the floor. With these improvements, the overall RMS error was reduced to 2°C between numerical results and the same test data reported in [19].

Improved CFD modeling of a small data center test cell

Computational analysis of reduced-mixing personal ventilation jets

Most data center design analyses focus on design point operation, which, in reality, is rarely realized due to the reliability needs and the constantly changing operating states of data centers. The objective of this work is to develop and experimentally validate a model that will allow data center operators and designers the ability to evaluate the energy impact of various data center loop configurations and operating strategies. The modeling methodology couples a thermodynamic model of the cooling equipment and a hydraulic pipe network for hydraulic characterization. Inherent in this model is the ability to capture off-design operating conditions of the data center cooling infrastructure caused by changes in ambient conditions and fluctuations in required IT load. The thermo-hydraulic model is validated based on an existing IT data center and chiller plant located in Poughkeepsie, New York. The model is used to study the data center under several climatic and operating conditions—namely, winter and summ...

H. Ezzat Khalifa

Papers

Experimental investigation of reduced-mixing personal ventilation jets

Experimental and computational study of perforated floor tile in data centers

Improved CFD modeling of a small data center test cell

Computational analysis of reduced-mixing personal ventilation jets

Development and experimental validation of a thermo-hydraulic model for data centers