Babak Fakhim

Thermal Performance of an Air-Cooled Data Center With Raised-Floor and Non-Raised-Floor Configurations

In this paper, the thermal performances of an air-cooled data center with raised-floor and non-raised-floor configurations are compared with respect to the room and ceiling return strategies. The thermal performance of the data center is evaluated in terms of supply heat index, rack cooling index, total irreversible loss, and the number of racks with at least one server exceeding the maximum recommended and allowable inlet air temperature according to American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) thermal guidelines. The numerical simulations are conducted providing an insight into the flow and temperature distributions, and thus giving a better understanding of the cooling issues. It is found that using a ceiling return strategy for the return of hot exhaust air to the computer room air conditioning units gives a better thermal performance of the data center, for both raised- and non-raised-floor strategy, as compared to the room return. The findings are then extended to a geometrically complex operational data center to improve its cooling effectiveness. The paper also highlights the drawback of using supply heat index alone as a performance metric.

A comparative study of raised-floor and hard-floor configurations in an air-cooled data centre

The thermal performance of an air-cooled data centre with raised-floor and hard-floor configurations are compared with respect to the room and ceiling return strategies. The supply heat index, rack cooling index and number of racks that exceed the maximum recommended and allowable rack inlet air temperature according to ASHRAEs thermal guidelines, are used to evaluate the thermal performance. Numerical simulations are conducted to obtain thermal and velocity fields. Results show that using a ceiling return strategy for the return of hot exhaust air to the CRACs gives a better thermal performance of the data centre, for both raised and hard-floor strategy as against the room return. The paper also addresses an important limitation of the supply heat index performance metric.

Analysis of exergy destruction in data centres

IT equipment and systems, housed in data centres, consume a considerable amount of electricity. Most of the electrical energy consumed by the data centre IT equipment is released in the form of heat. From a second law of thermodynamics analysis point of view, the mixing of hot and cold air streams in the room caused by hot air recirculation is an irreversible process, leading to wasted work potential in data centres. In the work presented here, a numerical analysis of flow and temperature distribution of a raised-floor data centre is conducted in order to evaluate the thermal performance of the data centre. Subsequently, from flow patterns and temperature profiles, a detailed exergy analysis of the data centre is performed to get a better understanding of the room airspace irreversibilities. The amount of the exergy as well as the exergy destroyed in the airspace is evaluated in order to cast a light on the nature of the irreversibilities. Finally, new performance metrics based on the second law of thermodynamics are proposed and used to assess the performance of a data centre. A comparison between the performance metrics based on the first and second law of thermodynamics as well as the limitations of the newly derived performance metrics are discussed.

Thermal Performance of Data Centers-Rack Level Analysis

This paper analyzes the thermal performance of a data center on a rack level, by utilizing racks stocked with 1U servers. Eleven different rack models covering a wide range of server arrangements with void spaces are presented and modeled in a raised-floor configuration. The objective is to investigate the thermal performance of semipopulated racks with different server arrangements. The inlet and outlet temperature profiles of the models are presented and the overall effect of each model on the thermal performance of a specific rack is discussed. Findings point toward the detailed modeling of semipopulated racks to investigate the main locations of the temperature spikes adjacent to the rack inlet and outlets as well as the recirculation zones.

Addressing Thermal Challenges in Design of Data Centres

Aggregation of small networking hardware has led to an ever increasing power density in data centres. The energy consumption of IT systems is continuing to rise substantially owing to the demands of electronic information and storage requirements. Energy consumption of data centres can be severely and unnecessarily high due to inadequate localised cooling and densely packed rack layouts. However, as heat dissipation in data centres rises by orders of magnitude, inefficiencies such as air recirculation causing hot spots, leading to flow short-circuiting will have a significant impact on the thermal manageability and energy efficiency of the cooling infrastructure. Therefore, the thermal management of high-powered electronic components is a significant challenge for cooling of data centres. In this project, an operational data centre has been studied. Field measurements of temperature have been performed. Numerical analysis of flow and temperature fields is conducted in order to evaluate the thermal behaviour of the data centre. A number of undesirable hot spots have been identified. To rectify the problem, a few practical design solutions to improve the cooling effectiveness have been proposed and examined to ensure a reduced air-conditioning power requirement. Therefore, a better understanding of the cooling issues and the respective proposed solutions can lead to an improved design for future data centres.© 2010 ASME

Generation of sclerosant foams by mechanical methods increases the foam temperature

Objective To investigate the effect of agitation on foam temperature. Methods Sodium tetradecyl sulphate and polidocanol were used. Prior to foam generation, the sclerosant and all constituent equipment were cooled to 4–25℃ and compared with cooling the sclerosant only. Foam was generated using a modified Tessari method. During foam agitation, the temperature change was measured using a thermocouple for 120 s. Results Pre-cooling all the constituent equipment resulted in a cooler foam in comparison with only cooling the sclerosant. A starting temperature of 4℃ produced average foam temperatures of 12.5 and 13.2℃ for sodium tetradecyl sulphate and polidocanol, respectively. It was also found that only cooling the liquid sclerosant provided minimal cooling to the final foam temperature, with the temperature 20 and 20.5℃ for sodium tetradecyl sulphate and polidocanol, respectively. Conclusion The foam generation process has a noticeable impact on final foam temperature and needs to be taken into consideration when creating foam.

Exergy Analysis of Data Centres-Effect of the Rack Location and Airflow Direction on the Thermal Performance

In this paper, a numerical analysis of flow and temperature distribution of a small raised-floor data centre is conducted in order to evaluate the thermal performance of the data centre. The flow patterns and temperature profiles established leads to a detailed exergy analysis of the data centre, which results in better understanding of irreversibilities in room airspace. The impact of the rack location in the data centre room and the airflow direction through perforated tiles on the thermal performance of the data centre is investigated using first-law and second-law of thermodynamics.

Fluid-structure interaction analysis on the effects of bifurcation angle asymmetry in a left main coronary artery model

This study was to investigate the effect of the bifurcation angle asymmetry on recirculation flow, pressure drop and wall shear stress (WSS) in an atherosclerotic model of a left coronary artery with left anterior descending (LAD) and left circumflex (LCX) branches. The linear regression analysis results showed that there is a positive correlation between WSS and bifurcation angle asymmetry. However, small increase in the WSS magnitude due to the increase in bifurcation angle asymmetry revealed the angle asymmetry does not seem to have a profound effect on the WSS. The results also showed that the bifurcation angle asymmetry play a prominent role in determining the pressure drop and recirculation area, while having relatively unnoticeable effects on the wall shear stress (WSS).

Effect of Stenosis Eccentricity in a Model of Bifurcated Coronary Artery

This study was to implement fluid structure interaction (FSI) method in order toinvestigate the effect of stenosis eccentricity on the recirculation flow, pressure drop and wall shearstress (WSS) in an atherosclerotic model of a left coronary artery with left anterior descending(LAD) and left circumflex (LCX) branches. The linear regression analysis results showed a positivecorrelation between WSS and stenosis eccentricity. The results also showed that the stenosiseccentricity plays a prominent role in determining the pressure drop and recirculation area, whilehaving relatively unnoticeable effects on WSS.

Thermal Management of Data Centres – Effect of CRAC Location and Flow Rate on the Performance of Data Centres

IT Equipment and Systems, Housed in Data Centres, Consume a Considerable Amount Ofenergy. most of the Electrical Energy Consumed by the Data Centre IT Equipment is Released in Theform of Heat. Cooling Issues will have a Significant Impact on the Thermal Manageability and Energyefficiency of the Cooling Infrastructure. in this Paper, a Numerical Analysis of Flow and Temperaturedistribution of a Raised-Floor Data Centre is Conducted in Order to Evaluate the Thermal Performance Ofthe Data Centre. the Effect of the Computer Room Air Conditioning (CRAC) Location and Flow Rate Onthe Data Centre Performance in Investigated Using Thermodynamic-Based Performance Metrics.