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A holistic system-level analysis of the energy and mass transfer in a data center cooling system is used to determine the exergy destruction by each component in the system. The analysis, performed using our in-house analysis code, allows for identification of system inefficiencies and comparison of the energy efficiency of different data center cooling strategies. In this paper, we describe a systematic...
Hybrid air/liquid cooling systems used in data centers enable localized, on-demand cooling, or “smart cooling” using various approaches such as rear door heat exchangers, overhead cooling systems and in row cooling systems. These systems offer the potential to achieve higher energy efficiency by providing local cooling only when it is needed, thereby reducing the overprovisioning that is endemic to...
This paper discusses data center scale performance characterization of hybrid liquid-air cooling solutions for a full 42U rack of servers. Using data collected in a production data center at Lawrence Berkeley Laboratories, we interpret the results with a simple three parameter model which allows characterization of the major factors affecting heat recovery efficiency of the system. The model is shown...
This paper evaluates the impact of pressure drop in server racks on the cooling of the IT equipment. The measured impedance curves for servers internal resistance, rack doors, and Cable Management Arms (CMA) are used to estimate the reduction in the cooling airflow rate. In this study, 1 RU and 2 RU servers, and a 9 RU server simulator are used as representative IT equipment. A Computational Fluid...
Concerted efforts are being made by data center professionals to ensure that data centers are made more sustainable by reducing energy consumption. The combination of increasing IT workloads and packaging densities place stringent requirements on data center cooling systems. Various traditional airflow management technologies have been implemented that propose significant energy savings as well as...
Heat exchangers are important facilities used in data center cooling systems. The effectiveness of the heat exchangers strongly influences the thermal performance of the cooling systems. Rear door heat exchangers, in-row, overhead coolers and fully contained cabinets are some examples of executing liquid and hybrid cooling systems used in data centers. A liquid to liquid heat exchanger is an important...
The transient behavior of IT equipment can be represented by a lumped thermal capacitance for use in data center level transient thermal simulations. Previous work has proposed a mathematical methodology to extract the necessary lumped capacitance parameters, the server's time constant and heat transfer effectiveness, via air temperature measurements. This work describes and experimentally tests that...
In this work dynamic numerical models for server, rack, and Computer Room Air Handler (CRAH) are developed and used in a room level Computational Fluid Dynamics (CFD) model. The effect of server, rack, and Computer Room Air Handler (CRAH) heat capacity is investigated in cases of server power fluctuations and CRAH failure situations.
Air-cooled Data Centers absorb heat in central room air conditioners or air handlers and most commonly reject the heat through cooling towers to ambient air. The energy efficiency of the overall cooling system is determined by the energy efficiency of its components, its thermodynamic design and layout, and the protocol for its control, operation and its operational set points. The current work is...
Our theoretical studies showed that absorption refrigeration (AR) system and organic Rankine cycle (ORC) are the most promising technology candidates in utilizing the waste heat dissipated by data centers. Since both candidates work with heat of temperatures not less than ∼65°C, this study is limited to water-cooled and hybrid two-phase cooled data centers. However, there exist challenges in the integration...
A model for a basic hot aisle/cold aisle data center configuration was built and analyzed using the commercial computational fluid dynamics (CFD) software FloTHERM. The CFD study was motivated by experimental data that sho wed air recirculatio n from the hot aisle to the cold aisle through the gap between the floor and the bottom of the server cabinet. This flow can be attributed to lower values of...
Data centers are very costly structures, both in terms of capital and operational expenditures. The high innovation rate in the IT business conflicts with the long-term character of data centers. In order to ensure lifetime usability, flexibility is a major concern for any data center design. Recent developments of data center air-cooling, in particular containment solutions for hot/cold air separation,...
As a common practice in the data center industry, chassis fans are used to direct air flow independent from neighboring servers. In general, smaller fans are less efficient compared to geometrically similar larger fans. In this study, a novel approach is proposed whereby chassis enclosed fans are replaced with a smaller number of larger fans installed behind a stacked array of servers which share...
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