Steady State and Transient Experimentally Validated Analysis of Hybrid Data Centers

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Tianyi Gao ◽  
Bahgat Sammakia ◽  
Emad Samadiani ◽  
Roger Schmidt
Keyword(s):  
Steady State ◽  
Heat Exchanger ◽  
Thermal Management ◽  
Information Technologies ◽  
Data Centers ◽  
Cooling System ◽  
Hybrid Approach ◽  
Air Cooling ◽  
Air Conditioner ◽  
Density Data

Data centers consume a considerable amount of energy which is estimated to be about 2% of the total electrical energy consumed in the U.S. in the year 2010, and this number continues to increase every year. Thermal management is becoming increasingly important in the effort to improve the energy efficiency and reliability of data centers. The goal is to keep the information technologies (IT) equipment temperature within the allowable range in high power density data centers while reducing the energy used for cooling. In this regard, liquid and hybrid air/water cooling systems are alternatives to traditional air cooling. In particular, these options offer advantages for localized cooling higher power racks which may not be manageable using the room level air cooling system without requiring significantly more energy. In this paper, a hybrid cooling system in data centers is investigated. In addition to traditional raised floor, cold aisle-hot aisle configuration, a liquid–air heat exchanger attached to the back of racks is considered. First of all, the paper presents a review of literature of the study of this heat exchanger strategy in the thermal management of a data center. The discussion focus on rear door heat exchanger (RDHx) performance, both the steady state and transient impact are analyzed. The studies show that under some circumstances, this hybrid approach could be a viable alternative to meet the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommended inlet air temperatures, while at the same time reducing the overall energy consumption in high density data centers. The hybrid design approach can also significantly improve the dynamic performance during rack power increases or computer room air conditioner (CRAC) unit failure. And then, additional parametric steady state and dynamic analyses, are presented in detail for the different scenarios.

New Thermal Management Systems for Data Centers

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Mayumi Ouchi ◽  
Yoshiyuki Abe ◽  
Masato Fukagaya ◽  
Takashi Kitagawa ◽  
Haruhiko Ohta ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Single Phase ◽  
Data Centers ◽  
Cooling System ◽  
Heat Pipes ◽  
Air Cooling ◽  
Liquid Cooling ◽  
Two Phase ◽  
Cooling Jacket ◽  
Cooling Methods

Energy consumption in data centers has seen a drastic increase in recent years. In data centers, server racks are cooled down in an indirect way by air-conditioning systems installed to cool the entire server room. This air cooling method is inefficient as information technology (IT) equipment is insufficiently cooled down, whereas the room is overcooled. The development of countermeasures for heat generated by IT equipment is one of the urgent tasks to be accomplished. We, therefore, proposed new liquid cooling systems in which IT equipment is cooled down directly and exhaust heat is not radiated into the server room. Three cooling methods have been developed simultaneously. Two of them involve direct cooling; a cooling jacket is directly attached to the heat source (or CPU in this case) and a single-phase heat exchanger or a two-phase heat exchanger is used as the cooling jacket. The other method involves indirect cooling; heat generated by CPU is transported to the outside of the chassis through flat heat pipes and the condensation sections of the heat pipes are cooled down by coolant with liquid manifold. Verification tests have been conducted by using commercial server racks to which these cooling methods are applied while investigating five R&D components that constitute our liquid cooling systems: the single-phase heat exchanger, the two-phase heat exchanger, high performance flat heat pipes, nanofluid technology, and the plug-in connector. As a result, a 44–53% reduction in energy consumption of cooling facilities with the single-phase cooling system and a 42–50% reduction with the flat heat pipe cooling system were realized compared with conventional air cooling system.

scholarly journals Comprehensive Experimental and Computational Analysis of a Fully Contained Hybrid Server Cabinet

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Kourosh Nemati ◽  
Husam A. Alissa ◽  
Bruce T. Murray ◽  
Bahgat G. Sammakia ◽  
Russell Tipton ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Data Centers ◽  
Heat Dissipation ◽  
Cooling System ◽  
Thermal Characterization ◽  
Temperature Limit ◽  
Research Area ◽  
Air Cooling ◽  
Steady State Mode ◽  
Compact Models

The rapid growth in the number of data centers combined with the high-density heat dissipation of computer and telecommunications equipment has made energy efficient thermal management of data centers a key research area. Localized hybrid air–water cooling is one approach to more effectively control the cooling when there is wide variation in the amount of dissipation in neighboring racks while the traditional air cooling approach requires overprovisioning. In a closed, hybrid air–water cooled server cabinet, the generated heat is removed by a self-contained system that does not interact with the room level air cooling system. Here, a hybrid-cooled enclosed cabinet and all its internal components were characterized experimentally in steady-state mode (e.g., experimentally determined heat-exchanger effectiveness and IT characterization). Also, a comprehensive numerical model of the cabinet was developed and validated using the experimental data. The computational model employs full numerical modeling of the cabinet geometry and compact models to represent the servers and the air/water heat exchanger. The compact models were developed based on experimental flow and thermal characterization of the internal components. The cabinet level model has been used to simulate a number of operating scenarios relevant to data center applications such as the effect of air leakage within the cabinet. The effect of the air side and the water side failure of the cooling system on the IT performance were investigated experimentally. A comparison was made of the amount of time required to exceed the operating temperature limit for the two scenarios.

Perimeter Cooling Unit and Localized Row-Based Cooling Unit Transient Air Flow Effects Modeling and Characterization in Data Centers

2015 ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Bahgat G. Sammakia ◽  
Russell Tipton ◽  
Mark Seymour
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Data Centers ◽  
Cooling System ◽  
Air Flow ◽  
Cooling Systems ◽  
Dynamic Thermal Management ◽  
Hybrid Cooling ◽  
Cooling Unit ◽  
Cooling Air

Cooling power constitutes a large portion of the total electrical power consumption in data centers. Approximately 25%∼40% of the electricity used within a production data center is consumed by the cooling system. Improving the cooling energy efficiency has attracted a great deal of research attention. Many strategies have been proposed for cutting the data center energy costs. One of the effective strategies for increasing the cooling efficiency is using dynamic thermal management. Another effective strategy is placing cooling devices (heat exchangers) closer to the source of heat. This is the basic design principle of many hybrid cooling systems and liquid cooling systems for data centers. Dynamic thermal management of data centers is a huge challenge, due to the fact that data centers are operated under complex dynamic conditions, even during normal operating conditions. In addition, hybrid cooling systems for data centers introduce additional localized cooling devices, such as in row cooling units and overhead coolers, which significantly increase the complexity of dynamic thermal management. Therefore, it is of paramount importance to characterize the dynamic responses of data centers under variations from different cooling units, such as cooling air flow rate variations. In this study, a detailed computational analysis of an in row cooler based hybrid cooled data center is conducted using a commercially available computational fluid dynamics (CFD) code. A representative CFD model for a raised floor data center with cold aisle-hot aisle arrangement fashion is developed. The hybrid cooling system is designed using perimeter CRAH units and localized in row cooling units. The CRAH unit supplies centralized cooling air to the under floor plenum, and the cooling air enters the cold aisle through perforated tiles. The in row cooling unit is located on the raised floor between the server racks. It supplies the cooling air directly to the cold aisle, and intakes hot air from the back of the racks (hot aisle). Therefore, two different cooling air sources are supplied to the cold aisle, but the ways they are delivered to the cold aisle are different. Several modeling cases are designed to study the transient effects of variations in the flow rates of the two cooling air sources. The server power and the cooling air flow variation combination scenarios are also modeled and studied. The detailed impacts of each modeling case on the rack inlet air temperature and cold aisle air flow distribution are studied. The results presented in this work provide an understanding of the effects of air flow variations on the thermal performance of data centers. The results and corresponding analysis is used for improving the running efficiency of this type of raised floor hybrid data centers using CRAH and IRC units.

scholarly journals Improving the performance of the air-cooling unit in the cooling system of a radar

2021 ◽  
Vol 2057 (1) ◽  
pp. 012004
Author(s):  
Yu A Borisov ◽  
V V Volkov-Muzilev ◽  
D A Kalashnikov ◽  
H S Khalife
Keyword(s):  
Heat Exchanger ◽  
Gas Flow ◽  
Cooling System ◽  
Experimental Studies ◽  
Air Cooling ◽  
Axial Fan ◽  
Gas Dynamic ◽  
Cooling Unit ◽  
Calculation Results ◽  
Axial Fans

Abstract The article discusses the issues of reducing the size of the cooling unit of the antenna of a radar station by improving the gas-dynamic processes occurring in the air-cooling unit. The results of the experimental studies of the gas flow in a plate-fin heat exchanger, being blown by one axial fan are presented. The feasibility of changing the number of axial fans for organizing a more uniform flow around the heat-exchange surfaces has been determined by calculation and theoretical methods. The calculation results are confirmed by experimental studies of the air flow in the segment of the heat exchanger, which is provided by a smaller fan.

scholarly journals Outdoor Air-Cooling System for a Computer Room and Its Corresponding Energy-Saving Effect

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5719
Author(s):  
JiHyun Hwang ◽  
Taewon Lee
Keyword(s):  
Power Consumption ◽  
Energy Saving ◽  
Data Centers ◽  
Cooling System ◽  
Stable Operation ◽  
Air Cooling ◽  
Outdoor Air ◽  
Air Conditioners ◽  
Air Cooling System ◽  
Saving Effect

The recent expansion of the internet network and rapid advancements in information and communication technology are expected to lead to a significant increase in power consumption and the number of data centers. However, these data centers consume a considerable amount of electric power all year round, regardless of working days or holidays; thus, energy saving at these facilities has become essential. A disproportionate level of power consumption is concentrated in computer rooms because air conditioners in these rooms are required to operate throughout the year to maintain a constant indoor environment for stable operation of computer equipment with high-heat release densities. Considerable energy-saving potential is expected in such computer rooms, which consume high levels of energy, if an outdoor air-cooling system and air conditioners are installed. These systems can reduce the indoor space temperature by introducing a relatively low outdoor air temperature. Therefore, we studied the energy-saving effect of introducing an outdoor air-cooling system in a computer room with a disorganized arrangement of servers and an inadequate air conditioning system in a research complex in Korea. The findings of this study confirmed that annual energy savings of up to approximately 40% can be achieved.

Steady State and Transient Comparison of Perimeter and Row-Based Cooling Employing Controlled Cooling Curves

2015 ◽  
Author(s):  
Husam A. Alissa ◽  
Kourosh Nemati ◽  
Bahgat Sammakia ◽  
Alfonso Ortega ◽  
David King ◽  
...  
Keyword(s):  
Steady State ◽  
Heat Exchanger ◽  
Data Center ◽  
Cooling System ◽  
Air Flow ◽  
Thermal Inertia ◽  
Small Data ◽  
Cfd Model ◽  
Controlled Cooling ◽  
Failure Scenario

The perpetual increase of data processing has led to an ever increasing need for power and in turn to greater cooling challenges. High density (HD) IT loads have necessitated more aggressive and direct approaches of cooling as opposed to the legacy approach by the utilization of row-based cooling. In-row cooler systems are placed between the racks aligned with row orientation; they offer cool air to the IT equipment more directly and effectively. Following a horizontal airflow pattern and typically occupying 50% of a rack’s width; in-row cooling can be the main source of cooling in the data center or can work jointly with perimeter cooling. Another important development is the use of containment systems since they reduce mixing of hot and cold air in the facility. Both in-row technology and containment can be combined to form a very effective cooling solution for HD data centers. This current study numerically investigates the behavior of in-row coolers in cold aisle containment (CAC) vs. perimeter cooling scheme. Also, we address the steady state performance for both systems, this includes manufacturer’s specifications such as heat exchanger performance and cooling coil capacity. A brief failure scenario is then run, and duration of ride through time in the case of row-based cooling system failure is compared to raised floor perimeter cooling with containment. Non-raised floor cooling schemes will reduce the air volumetric storage of the whole facility (in this small data center cell it is about a 20% reduction). Also, the varying thermal inertia between the typical in-row and perimeter cooling units is of decisive importance. The CFD model is validated using a new data center laboratory at Binghamton University with perimeter cooling. This data center consists of one main Liebert cooling unit, 46 perforated tiles with 22% open area, 40 racks distributed on three main cold aisles C and D. A computational slice is taken of the data center to generalize results. Cold aisle C consists of 16 rack and 18 perforated tiles with containment installed. In-row coolers are then added to the CFD model. Fixed IT load is maintained throughout the simulation and steady state comparisons are built between the legacy and row-based cooling schemes. An empirically obtained flow curve method is used to capture the flow-pressure correlation for flow devices. Performance scenarios were parametrically analyzed for the following cases: (a) Perimeter cooling in CAC, (b) In-row cooling in CAC. Results showed that in-row coolers increased the efficiency of supply air flow utilization since the floor leakage was eliminated, and higher pressure build up in CAC were observed. This reduced the rack recirculation when compared to the perimeter cooled case. However, the heat exchanger size demonstrated the limitation of the in-row to maintain controlled set point at increased air flow conditions. For the pump failure scenario, experimental data provided by Emerson labs were used to capture the thermal inertia effect of the cooling coils for in-row and perimeter unit, perimeter cooled system proved to have longer ride through time.

CFD Analysis of Thermal Shadowing and Optimization of Heatsinks in 3rd Generation Open Compute Server for Single-Phase Immersion Cooling

2019 ◽  
Author(s):  
Jimil M. Shah ◽  
Ravya Dandamudi ◽  
Chinmay Bhatt ◽  
Pranavi Rachamreddy ◽  
Pratik Bansode ◽  
...  
Keyword(s):  
Thermal Management ◽  
Power Density ◽  
Heat Sink ◽  
Single Phase ◽  
Data Centers ◽  
Air Cooling ◽  
Third Generation ◽  
Dielectric Fluids ◽  
Immersion Cooling ◽  
The Impact

Abstract In today’s networking world, utilization of servers and data centers has been increasing significantly. Increasing demand of processing and storage of data causes a corresponding increase in power density of servers. The data center energy efficiency largely depends on thermal management of servers. Currently, air cooling is the most widely used thermal management technology in data centers. However, air cooling has started to reach its limits due to high-powered processors. To overcome these limitations of air cooling in data centers, liquid immersion cooling methods using different dielectric fluids can be a viable option. Thermal shadowing is an effect in which temperature of a cooling medium increases by carrying heat from one source and results in decreasing its heat carrying capacity due to reduction in the temperature difference between the maximum junction temperature of successive heat sink and incoming fluid. Thermal Shadowing is a challenge for both air and low velocity oil flow cooling. In this study, the impact of thermal shadowing in a third-generation open compute server using different dielectric fluids is compared. The heat sink is a critical part for cooling effectiveness at server level. This work also provides an efficient range of heat sinks with computational modelling of third generation open compute server. Optimization of heat sink can allow to cool high-power density servers effectively for single-phase immersion cooling applications. A parametric study is conducted, and significant savings in the volume of a heat sink have been reported.

scholarly journals Design of an Optimized Thermal Management System for Li-Ion Batteries under Different Discharging Conditions

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5695 ◽  
Author(s):  
Ankur Bhattacharjee ◽  
Rakesh K. Mohanty ◽  
Aritra Ghosh
Keyword(s):  
Thermal Management ◽  
Cooling System ◽  
Peak Temperature ◽  
Air Cooling ◽  
Li Ion Batteries ◽  
Li Ion Battery ◽  
Liquid Cooling ◽  
Thermal Management System ◽  
Li Ion ◽  
Liquid Cooling System

The design of an optimized thermal management system for Li-ion batteries has challenges because of their stringent operating temperature limit and thermal runaway, which may lead to an explosion. In this paper, an optimized cooling system is proposed for kW scale Li-ion battery stack. A comparative study of the existing cooling systems; air cooling and liquid cooling respectively, has been carried out on three cell stack 70Ah LiFePO4 battery at a high discharging rate of 2C. It has been found that the liquid cooling is more efficient than air cooling as the peak temperature of the battery stack gets reduced by 30.62% using air cooling whereas using the liquid cooling method it gets reduced by 38.40%. The performance of the liquid cooling system can further be improved if the contact area between the coolant and battery stack is increased. Therefore, in this work, an immersion-based liquid cooling system has been designed to ensure the maximum heat dissipation. The battery stack having a peak temperature of 49.76 °C at 2C discharging rate is reduced by 44.87% to 27.43 °C after using the immersion-based cooling technique. The proposed thermal management scheme is generalized and thus can be very useful for scalable Li-ion battery storage applications also.

Sign in / Sign up

Export Citation Format

Share Document