Hot Aisle Containment Research Articles

Effects and optimization of airflow on the thermal environment in a data center

In this research, the escalating energy consumption challenges in data centers are addressed by optimizing airflow organization designs. Through the use of computational fluid dynamics (CFD) simulations, three different airflow strategies were evaluated and improved: underfloor precision air conditioning, inter-column air conditioning, and backplane air conditioning. These cooling systems, which are usually considered in isolation, were compared in a comprehensive manner to get a full picture of their efficiency and effectiveness. The findings reveal that the implementation of cold aisle containment (CAC) or hot aisle containment (HAC) significantly improves air supply efficiency (ASE) and reduces the supply heat index (SHI), leading to a more uniform temperature distribution and enhanced cooling performance. Specifically, the ASE increased from 65.69% to 85.57% and 90.25% for underfloor precision air conditioning and from 71.29% to 92.16% and 92.17% for inter-column air conditioning, with corresponding reductions in SHI. The backplane cooling system offered consistent ambient temperatures throughout the room, eliminating thermal hotspots without the need for aisle containment. This study offers a comparative analysis of different airflow organization schemes, highlighting the benefits of aisle containment in precision and inter-column air conditioning and the suitability of backplane air conditioning for high-density cooling without the need for traditional aisle separation. The results are crucial for informing energy-efficient cooling strategies in data center design and operation.

GREEN DATA CENTERS: SUSTAINABLE PRACTICES FOR ENERGY-EFFICIENT IT INFRASTRUCTURE

The digital age has led to a surge in connectivity, innovation, and information exchange, but it has also led to escalating energy consumption by data centers. Green data centers have emerged as a transformative solution, embodying a commitment to sustainability through eco-friendly practices and cutting-edge technologies. Key principles of green data centers include energy-efficient hardware, renewable energy integration, advanced cooling systems, and resource optimization strategies. Energy-efficient hardware involves replacing outdated servers, storage systems, and network equipment with energy-efficient alternatives, such as virtualization technologies. This reduces power consumption and sets the stage for a more sustainable and technologically advanced data center infrastructure. Renewable energy integration reduces dependence on traditional power grids and fossil fuels, ensuring an eco-friendlier energy supply. Advanced cooling systems, such as liquid immersion, hot aisle containment, and free air cooling, optimize efficiency while maintaining ideal server temperatures. Resource optimization ensures that every unit of energy is utilized judiciously, contributing to the overarching goal of sustainability. The transition to green data centers presents challenges such as upfront investment costs, integration of renewable energy with fluctuating power grids, and technical complexities associated with advanced cooling systems. However, there are substantial opportunities, including reduced operational costs, improved brand image, and compliance with environmental regulations. Emerging trends in green data centers include artificial intelligence and edge computing, which enable optimization of cooling systems, prediction of peak workloads, and dynamic resource management. By prioritizing energy efficiency, embracing innovative technologies, and staying attuned to emerging trends, data centers can play a pivotal role in forging a more sustainable digital future.
 Keywords: Green Data Centers, Sustainability, Energy Efficiency, It Infrastructure, Edge Computing, Artificial Intelligence.

Multi-criteria assessments of increasing supply air temperature in tropical data center

With rapid development of information technology, the number and scale of data centers (DCs) increase rapidly. Therefore, cooling energy saving becomes crucial. This study proposes multi-criteria assessments of increasing supply air temperature (SAT) in the air-cooled DCs to analyze the interactions of internal and external factors in cooling systems comprehensively. Impacts of refrigerant charge (RC), evaporation pressure (EP) control limits, and hot aisle containment (HAC) with improvements in SAT are compared and analyzed according to the thermodynamic, economic, and thermoeconomic aspects. Overall, as SAT increases from 20 °C to 32 °C, the power usage effectiveness decreases by 16.8%–19.3%. Increase in RC leads to energy consumption and cost increasing at high SAT ranges, whereas high RC shows obvious advantages at the low SAT from the thermoeconomic aspects. Additionally, releasing EP control limits has significant advantages in reducing energy usage, and cumulative present worth of data center testbed can decrease by 5.2% and 6.0% at low and high RC operations, respectively. Return on investment and payback period analysis are also performed in the testbed with the HAC reform, and the payback period is about 1–3 years with the SAT setting range at 20–32 °C.

Predicting the Fire Source Location by Using the Pipe Hole Network in Aspirating Smoke Detection System

The aspirating smoke detector (ASD) is one of the most critical pieces of equipment for detecting smoke in a protected area when a fire occurs. It has more advantages than a conventional smoke detector because it can be used in extreme conditions, such as cold storage facilities or hot aisle containment areas. ASD uses a fan to draw air from the protected area into the pipe network system via pipe holes. The sucked air is transported into the sensing chamber to detect smoke. If the obscuration in the sensing chamber is greater than the setpoint, the ASD will sound an alarm so that people realize there is a fire. For this reason, investigating the effect of the pipe hole network on obscuration in the ASD is critical. In this study, a Pipe Hole Network Program was developed to consider the pipe flow parameter. A numerical study based on the program and an experimental study was performed. The results showed that the numerical results had the same trend as the experimental study. The further the location of the fire source was, the lower the obscuration was. In addition, the correlation between the obscuration parameter and the fire source distance was also derived. It could be used to predict the fire source location in the aspirating smoke detection system.

Vortex-enhanced thermal environment for air-cooled data center: An experimental and numerical study

Poor airflow management attributed to hot air recirculation and cold air by-pass adds massive thermal inefficiencies to air-cooled data center’s cooling system. The containment system usually was adopted to mitigate such drawbacks by isolating the space using a physical partition wall, such as hot aisle containment. Although the recirculation and by-pass can be effectively suppressed, the consequent high backpressure built up in the containment reducing the server air flowrate and possibly increasing the server temperature beyond the acceptable limit. This study presents a new enclosure mechanism for air-cooled data center using a vortex flow as an alternative to the conventional hot aisle containment to reduce the hot recirculation and, at the same time to retain the server air flowrate. The experiments conducted in a half-scale test cell (2-times smaller than a typical data center hall in length scale) examined vortex containment's effectiveness. The experiment results revealed that the average Supply Heat Index (SHI) in vortex hot aisle containment could be reduced to 0.11. Although vortex hot aisle containment did not enclose all hot recirculation compared to the full containment deployed in the benchmark layout, the relieved backpressure (the high pressure in the hot aisle) retains the rack flowrate by 42% (2.1 m/s in the vortex hot aisle containment with a diameter 1.2 m (VFL1200) layout compared to 1.2 m/s in full containment) and results in a 4.3% lower normalized server temperature (1.03 in VFL1200 layout compared to 1.076 in full containment CL). In the end, the validated CFD model provides more insights on vortex containment characteristics, such as the vortex strength and pressure distribution.

Experimental investigation on ducted hot aisle containment system for racks cooling of data center

A new type of ducted hot aisle containment system for racks cooling of data center has been proposed and put into practice gradually. However, the related academic research has not been carried out, especially for the improvement of cooling performance and influencing factors for the cooling system. In this paper, one experiment platform with 8 racks in 2 rows with multiple-heat-sources was established and tested under various working scenarios. In terms of improving the cooling performance, airtight treatment on the basis of ducted hot aisle containment system is better than itself and is also better than only collar, which is better than no collar. Besdides, doors closing is better than that doors opening, "V" diffuser is better than "T" diffuser, and “T” diffuser is better than no diffuser. Properly increasing installation ratio of blanking panels and air volume have also favorable impact. The experimental data and results in this paper will be of great significance to the design and application of ducted hot aisle containment system for racks cooling.

Numerical and experimental study of air containment systems in legacy data centers focusing on thermal performance and air leakage

With the increasing awareness of data center cooling and its impact on energy costs, hot-aisle containment (HAC) and cold-aisle containment (CAC) are considered vital techniques for IT environment control. Common data center cooling problems, which include air bypass and recirculation, are crucial to airtightness. The air leakage in an air containment is typically 10% or less. However, in practice, containment systems cannot guarantee complete airtightness, and do not function in the intended manner. In this study, both numerical and experimental studies were conducted to investigate the thermal performance of two systems. We found that there are operational differences that are significant factors influencing the amount of air leakage within the air containment systems. With an air leakage rate of 15%, the numerical simulation results show that selecting HAC, over CAC, can improve the thermal performance by 24.9%, corresponding to a 5.2% reduction in the return temperature index. The field measurements also show that HAC is more effective in cooling IT equipment. The supply air temperature of HAC can be raised by 2.0 °C; however, the IT operation environment will be similar to that of CAC. With an operational condition of high air leakage rate, HAC exhibits better thermal performance than CAC.

Numerical and Experimental analysis of the air distribution system in a data center building to improve the thermal performance

The purpose of the management of air distribution systems is to solve the problems in the cooling of data centers through minimizing the hot air recirculation and cold air bypass. In this paper, experimental and numerical analyses are conducted for the AUT data center. The data center performance indices have been compared between experimental and numerical solutions. According to temperature contours at a height of 1 m from the raised floor, recirculation of hot air to the cold aisle enclosure has occurred. For enhancement, the thermal management of the data center, cold aisle enclosure with decreasing supply airflow temperature to 18 , and hot aisle enclosure with return hot air from plenum ceiling to CRAC units were investigated. With the decrease in the total airflow supplied by CRAC units in the cold aisle enclosure and hot aisle enclosure models, the problem of Super-micro servers that experience about 50% more airflow than defined airflow for them in the base model, has been solved. The load on the cooling systems decreased from 13.2 kW up to 7.8 kW in hot aisle containment, the result is a hot aisle is a more suitable and appropriate configuration for the data center

A Comparative CFD Study of Two Air Distribution Systems with Hot Aisle Containment in High-Density Data Centers

Removing heat from high-density information technology (IT) equipment is essential for data centers. Maintaining the proper operating environment for IT equipment can be expensive. Rising energy cost and energy consumption has prompted data centers to consider hot aisle and cold aisle containment strategies, which can improve the energy efficiency and maintain the recommended level of inlet air temperature to IT equipment. It can also resolve hot spots in traditional uncontained data centers to some degree. This study analyzes the IT environment of the hot aisle containment (HAC) system, which has been considered an essential solution for high-density data centers. The thermal performance was analyzed for an IT server room with HAC in a reference data center. Computational fluid dynamics analysis was conducted to compare the operating performances of the cooling air distribution systems applied to the raised and hard floors and to examine the difference in the IT environment between the server rooms. Regarding operating conditions, the thermal performances in a state wherein the cooling system operated normally and another wherein one unit had failed were compared. The thermal performance of each alternative was evaluated by comparing the temperature distribution, airflow distribution, inlet air temperatures of the server racks, and recirculation ratio from the outlet to the inlet. In conclusion, the HAC system with a raised floor has higher cooling efficiency than that with a hard floor. The HAC with a raised floor over a hard floor can improve the air distribution efficiency by 28%. This corresponds to 40% reduction in the recirculation ratio for more than 20% of the normal cooling conditions. The main contribution of this paper is that it realistically implements the effectiveness of the existing theoretical comparison of the HAC system by developing an accurate numerical model of a data center with a high-density fifth-generation (5G) environment and applying the operating conditions.

CFD 기반 고밀도 데이터센터의 공기분배시스템 효율평가에 관한 비교연구

CFD 기반 고밀도 데이터센터의 공기분배시스템 효율평가에 관한 비교연구

Simulation-Based Assessment of Performance Indicator for Data Center Cooling Optimization

Abstract Data center power consumption has grown substantially in the past 20 years. According to the United States Data Center Energy Usage Report, the data center consumption in 2014 was estimated at 70 billion kWh, which accounted for 1.8% of the total U.S. electricity. The present effort investigates the effects of various data center parameters on a new set of metrics called the performance indicator to help assess and optimize the cooling performance of data centers. The three metrics in the performance indicator include power usage effectiveness ratio (PUEr), thermal conformance, and thermal resilience. The data center parameters investigated include computer room air handler (CRAH) setpoints, room configuration layouts, and containment strategies. The results show that the CRAH setpoint significantly influences the PUEr with higher setpoint values resulting in lower PUEr values. Room configuration layout changes and containment strategies showed substantial effects on thermal conformance and thermal resilience. The thermal conformance was increased approximately 10% with room configuration changes without changing the PUEr. Full hot aisle containment also improved the thermal conformance by 7.4%.

A Simulation-Based Approach to Data Center Thermal Efficiency Optimization

Abstract The energy consumption for cooling electronic equipment in data centers using central systems is significant and will continue to rise. The motivation of the present research study is based on the need to determine optimization strategies to improve and optimize the thermal efficiency of data centers using a simulation-based approach. Here, simulation is used to model and optimize a proposed research data center for use as an environment to test equipment and investigate best practices and strategies such as containment and hybrid cooling. The optimization technique used in this study finds the optimal operating conditions and containment strategies of the data center while meeting specific thermal conformance criteria. More specifically, optimum supply airflow rate and temperature setpoint of cooling units are sought under different containment configurations, including both hot aisle and cold aisle containment strategies in both full and partial setups. The results of the computational fluid dynamics (CFD) simulations indicated a lower probability of hot spots with full hot aisle containment strategy in a data center operating at lower supply airflow rate and higher supply temperature setpoint. The optimization approach helped to determine a more efficient cooling system without the risk of under-provisioning. The study considered steady-state conditions with static heat load and fixed equipment layout. However, the generalized optimization process developed in the present study should add to the repertoire of tools presently used for the optimization of new air-cooled data centers.

Impact of Server Thermal Design on the Cooling Efficiency: Chassis Design

There are various designs for segregating hot and cold air in data centers such as cold aisle containment (CAC), hot aisle containment (HAC), and chimney exhaust rack. These containment systems have different characteristics and impose various conditions on the information technology equipment (ITE). One common issue in HAC systems is a pressure build-up inside the HAC (known as backpressure). Backpressure also can be present in CAC systems in case of airflow imbalances. Hot air recirculation, limited cooling airflow rate in servers, and reversed flow through ITE with weaker fan systems (e.g., network switches) are some known consequences of backpressure. Currently, there is a lack of experimental data on the interdependency between overall performance of ITE and its internal design when backpressure is imposed on ITE. In this paper, three commercial 2-rack unit (RU) servers with different internal designs from various generations and performance levels are tested and analyzed under various environmental conditions. Smoke tests and thermal imaging are implemented to study the airflow patterns inside the tested equipment. In addition, the impact of hot air leakage into the servers through chassis perforations on the fan speed and the power consumption of the servers are studied. Furthermore, the cause of the discrepancy between measured inlet temperatures by the intelligent platform management interface (IPMI) and external sensors is investigated. It is found that arrangement of fans, segregation of space upstream and downstream of fans, leakage paths, the location of baseboard management controller (BMC) sensors, and the presence of backpressure can have a significant impact on ITE power and cooling efficiency.

Rack level transient CFD modeling of data center

PurposeThe paper aims to capture the rack-level thermal dynamics in data center. It proposes the rack-level response experiments as well as transient Computational Fluid Dynamics (CFD) analysis to characterize the local thermal environment of the system.Design/methodology/approachA single sever simulator rack and its two neighboring racks with its cold and hot aisle containment have been modeled with known cold air supply temperature and flow rate for transient CFD analysis. The heat load was kept constant initially and varied case-to-case basis, which includes capturing the rack-level response with respect to changes in input. However, the response experiments on simulator rack were performed for 14 h by variation of server heat loads as step and ramp input.FindingsThe paper provides the detailed transient CFD analysis of data center racks. The local cold air flow rates and temperature at the vicinity of the racks showed significant effect due to changes in input. It was concluded that the rack-level dynamics impacts the thermal environment of data center and hence cannot be ignored.Research limitations/implicationsThe high computing devices and faster internet demands have led to major thermal management concerns for data center operators. To tackle this issue, capturing the system thermal dynamics is imperative. However, the system-level CFD analysis is computationally expensive. Therefore, this paper deals with the rack-level transient CFD study using commercial tool STAR CCM+.Practical implicationsThis paper includes the modeling of the servers as a porous media as well as the multigrid method to enhance the computational speed. The successful implementation of this approach validated through experiments. This would help to establish a base for research in any type of data center.Originality/valueThis paper provides the porous media approach to model servers and multigrid method to enhance the computational speed. At the same time, the thought of characterizing the local dynamics at the vicinity of data center racks is unique.

Thermal Performance Evaluation of a New Close-Coupled Cooling Solution including Cooling Failure Analysis

The objective of this work is to introduce and evaluate a new end-of-aisle cooling design which consists of three cooling configurations. The key objectives of close-coupled cooling are to enable controlled cooling of information technology (IT) equipment, flexible and modular design, and the containment of hot air exhaust from the cold air. The thermal performance of the proposed solution is evaluated using computational fluid dynamics modeling. A computational model of a small size data center room has been developed. The room is modeled to be a hot aisle containment setup, i.e., the hot air exhaust exiting for each row is contained and directed within a specific volume. The cold aisle is separated from the hot aisle by means of banks of heat exchangers (HXs) placed on either side of the containment aisle. Based on the placement of rack fans, the design is divided into three sub-designs—Case 1: passive HXs with rack fan walls; Case 2: active HXs (coupled with fans) with rack fan walls; Case 3: active HXs (coupled with fans) with no rack fans. The cooling performance is calculated based on the thermal and flow parameters obtained for all three configurations. The computational data obtained has shown that the Case 1 is used only for lower system resistance IT. However, Cases 2 and 3 can handle denser IT systems. Case 3 is the design that can consume lower fan energy and handle denser IT systems. The article also discusses the cooling behavior of each type of design under cooling failure conditions with Case 2 showing better cooling redundancy compared with other two cases.

Universal Cooling of Data Centres: A CFD Analysis

At present, cooling of data centres efficiently is proving a challenging feat for many companies. With constantly increasing server size and IT demand, combined with the ever increasing energy consciousness of the world, many cooling systems are no longer up to the task of effectively cooling these Data Centres while maintaining an energy efficient environment. A review of journal papers, white papers, and information from companies who manufacture data centre cooling solutions was undertaken. The literature reviewed shows that any solution to this increasing problem needs to be flexible. Investigation was carried out on two different types of cooling system which showed the most promise within the literature review. An air-cooled type (hot aisle containment air cooling) and a liquid-cooled type (single-phase liquid immersion cooling) were the two types of data centre cooling systems selected. 2D simulation of each of these systems, using ANSYS© Fluent 17.2 Academic, was carried out to demonstrate the flexibility of each system when rack density is increased from 15kW to 30kW. Conclusions were drawn that air was not a flexible cooling method if changes were to be made to the IT equipment, with a maximum outlet temperature of 324K (51°C) for the 15kW system rising to 342K (69°C) when changed to a 30kW system. It was also found that liquid immersion cooling was flexible and maintained an average outlet temperature of 298K (25°C) even when the IT equipment was uprated to 30kW.

Effect of raised floor height on different arrangement of under-floor air distribution performance in data center

In the more and more expanding and complicated data center, requirements on air conditioning system and the air distribution arrangement are getting higher and higher. One of the resolutions is improving the airflow uniformity and cooling the local over-hot area by raising the floor in the data center. With a typical mode of four rows of cabinets in the data center as a sample. This paper uses Computational fluid dynamic (CFD) to investigate the influence of the six raised floor heights (0.2m, 0.4m, 0.6m, 0.8m, 1m and 1.2m) on the airflow distribution of three types of under-floor air distribution (the open aisle, the cold aisle containment and the hot aisle containment). Optimization is done on performance indexes, including supply/return heat index (SHI/RHI), return cooling index (RCI) and return temperature index (RTI), with which the condition of subcooling / overheating of all cabinets and the characteristics of the airflow organization in the data center are reflected and the thermal environment in the data center is revealed. Normally, the cooling effect and the uniformity of the airflow can be improved by raising the floor height. However, this won’t work well when the floor height reaches a certain level. Therefore, based on the comparative analysis on the 18 different cases in this investigation, the recommended range of raised floor height in data centers of different construction can be obtained and verified in the experimental tests. The experimental results turn out to be in accordance with the simulation results, which proves the range recommended in this investigation is valuable.

Experimental Characterization of Various Cold Aisle Containment Configurations for Data Centers

The data center industry has experienced significant growth over the last decade, mainly due to the increased use of the internet for our day to day activities such as e-commerce, social media, video streaming, and healthcare. This growth in demand results in higher energy costs, as data centers can be energy intensive facilities. A significant portion of the energy used in data centers is for cooling purposes. Hence, it is one of the important areas of optimization to be addressed to create more efficient data centers. Among the many ways to increase data center efficiencies, air flow management is a key solution to many existing data centers. Fundamentally, there are three main schemes: hot-aisle containment, cold-aisle containment, and exhaust chimney containment. This paper's focus is to experimentally characterize the following cold aisle configurations: open aisle, partially contained aisle, and fully contained aisles. Experimental data presented to evaluate the effectiveness of the different configurations are rack inlet contour plots, tile and rack flow rates, pressure measurements, and server central processing unit (CPU) temperatures.

Analyzing the Cooling Efficiency of the Thermal Environment in Data Centers

Given the explosive growth of data, scalability and fault tolerance have become a fundamental challenge for data center network structures. Temperature in data centers significantly affects the failure ratio of high-speed network devices. Various types of air distribution schemes influence the temperature of network equipment differently, and the cooling cost in data centers dominates the overall energy cost. On the basis of the energy efficiency of cooling systems, this study analyzes and compares the thermal load distribution in the enclosure of standard and non-standard data centers by considering the effects of the external environment. Analysis results demonstrate that the external environment significantly affects the thermal load of non-standard data centers. By leveraging on the air temperature outside data centers and on the inlet/outlet of IT equipment, the air temperature and return air temperature of air conditioning are calculated when performing hot and cold aisle containment. The calculations indicate that sealing an appropriate aisle (hot or cold aisle) can significantly reduce the energy consumption of cooling systems in terms of the external air temperature outside data centers. Furthermore, if the air temperature outside data centers is higher than the temperature at the inlet of IT equipment, sealing the cold aisle outperforms sealing the hot aisle. By contrast, the aisle to be sealed depends on the energy efficiency ratio of the air conditioning.