Hamza Salih Erden

Istanbul Technical University · Informatics Institute

High density data centers consume mega watts of electricity for both computing and cooling. Because of the fast paced growth of data center energy demand, effective energy conservation measures must be implemented. The use of on-site combined power generation and cooling systems for data centers that are located on campuses is discussed and compare...

Transient thermal events in air-cooled data centers may lead to undesirable operating conditions such as the formation of hot spots and associated degradation of equipment reliability. These transients may be caused by cooling equipment failures, server load changes, or other time-dependent scenarios in data center operations. This paper introduces...

Computer room air handling (CRAH) bypass (BP) method is an application that reduces the total fan power in air-cooled data centers by lowering CRAH fan speed. BP fans supply the complementary fraction of server airflow from warmer room air through lower-resistance floor openings into the plenum. Hence, chillers need to operate at lower temperatures...

The share of equipment and power use in smaller data centers (DCs) is comparable with that of more massive counterparts. However, they grabbed less attention in the literature despite being less energy-efficient. This study highlights the challenges of setting up a computational fluid dynamics (CFD) model of a 180-m2 small-size high-performance com...

Mechanical cooling is responsible for a significant fraction of the energy consumption of data centers (DCs). Free cooling systems take advantage of ambient conditions to reduce the need for compressor-based cooling. This study utilizes thermodynamic models of major free cooling systems such as the direct air-side economizer (ASE), indirect air-sid...

The emerging adhocracy of sustainability in every field of life, do also claims its Institutions necessitate to adapt their curriculums to the possible changes so that the engineers of the future are ready to address interdisciplinary and evolving challenges European engineering model, EELISA project has a dedicated work package to explore and prop...

The computer room air handling (CRAH) bypass (BP) method is a method to reduce the fan energy consumption in data centers. To provide a fraction of the server airflow, CRAH BP fans typically operate across an order of magnitude lower pressure drop across floor tiles compared to that across CRAH units. However, at a higher fraction of BP airflow, CR...

Today, selling electricity to the grid has lost its former profitability with reduced feed-in tariff (FiT) rates. This makes it crucial for prosumers to increase self-consumption and size their photovoltaic (PV) and battery energy storage system (BESS) units accordingly. Self-consumption can be increased through demand-side management (DSM) and an...

The recent spike in the demand for high-performance computing (HPC) server systems has created many challenges in data centers (DCs) including thermal management, system reliability sustenance and server failure minimalization. Lately, deep neural networks applied to infrared thermography (IRT) images have been successfully used for fault diagnosis...

Önceki optimizasyon çalışmaları sistem odası kliması (computer room air handling, CRAH) baypas (BP) yönteminin veri merkezlerindeki enerji tasarruf potansiyelini oda seviyesinde akış ağı modelleme ve soğutma altyapısı seviyesinde termodinamik modellemeyi harmanlayan indirgenmiş model yaklaşımı kullanmışlardır. Akış ağı modellerini barındıran termod...

As cloud computing applications have witnessed an exponential growth in recent years, the maintenance of server uptime has never been more important. A fault in a server due to overload, attack, or a misconfiguration of a cooling system can be of imponderable economic and financial loss to the echelons of global institutions. The advent of thermal...

Smart thermostats and home energy management systems (HEMSs) are generally studied separately. However, their joint use can provide a greater benefit. Therefore, this study primarily aims to combine a smart thermostat with a HEMS. The mixed-integer linear programming (MILP)-based HEMS performs day-ahead load scheduling for cost-minimization and pro...

This study highlights experimental challenges of setting up a computational fluid dynamics (CFD) model of a 180-m2 small-size high-performance computing (HPC) data center (DC) in a university campus and the validation procedure leading to a reasonably accurate CFD model for the investigation of the thermal environment. Experimental results based on...

Aisle containment systems reduce temperature nonuniformities in traditional air-cooled data centers and pave the way for higher cooling air temperature and more efficient operation of the cooling system and wider application of economizers. However, enclosing the aisle does not guarantee the lowest possible cooling infrastructure power. Enclosed ai...

Aisle containment separates hot and cold aisles in air-cooled data centers to prevent hot air recirculation into cold aisle and decrease temperature nonuniformity among the servers. Uniform server inlet temperatures allow the cooling system to operate more efficiently at a higher evaporator temperature. Lower cooling power consumption can be achiev...

Two time-dependent mathematical and numerical models with different levels of complexity and fidelity were developed to investigate the melting of a phase change material (PCM) configured as a number of aluminum-encased, PCM-filled slabs with embedded micro-channel aluminum tubes, and with parallel air-flow passages interposed between the slabs. Me...

Aisle containments in data centers help provide uniform server inlet air temperatures. This allows the cooling system to run at a higher evaporator temperature and more efficiently. On the other hand, CRAH units run at higher speeds to ascertain that racks receive sufficient air flow. Since CRAH fan power already constitutes an important component...

Temperature non-uniformities in traditional data centers can be eliminated or at least reduced by utilizing containment systems. As all servers receive the same inlet air temperature in a contained configuration, the cooling system can be operated more efficiently at a higher temperature, which also increases the potential for free cooling through...

Lumped capacitance models have been introduced to study transient thermal response of data centers. Chilled water interruption of a Computer Room Air Handling (CRAH) unit is one of several failure scenarios of data center cooling infrastructures. In such a scenario, predicting the transient thermal response of the CRAH unit depends requires the det...

Accurate prediction of data center temperatures and airflow following a transient event, such as the loss of cooling or variation in server load, requires that all sources of thermal mass in the data center be modeled with sufficient accuracy. One of the most important and simultaneously difficult-tomodel types of thermal mass in the data center is...

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 measuremen...

Current trends in data center cooling infrastructure design drive toward raising the coolant temperature to as high a level as equipment reliability allows in order to reduce the energy consumed by the cooling infrastructure and, consequently, improve (i.e., decrease) the power utilization effectiveness (PUE). However, as currently applied, PUE wou...

Computer servers can be represented by lumped thermal capacitances for the purpose of simulating server and data center transient thermal response to changes in operating conditions or equipment failures. Two parameters are needed to characterize the transient behavior of a lumped-capacitance server: its thermal capacitance and its thermal conducta...

This work investigates the transient response of the thermal environment in air cooled data centers through experiments, analytical and computational tools. The key thermal characteristics of the various data center components were extracted from a set of experiments. This includes the development of practical experimental procedures for the therma...

The Syracuse/IBM Green Data Center utilizes micro turbines in combination with exhaust fired heat exchangers and absorption chillers to produce electrical power, cooling and heating for the data center and surrounding infrastructure. The overall efficiency of cogeneration systems depend greatly on the utilization of turbine exhaust heat. This makes...

Transient CFD analysis of data centers requires appropriate representations of the transient thermal characteristics of servers. Thermal conductance and thermal capacitance are two determining characteristics for the response of servers under unsteady conditions. Previous studies proposed tests that require detailed temperature and thermal capacita...

Servers have time constants on the order of several minutes, which is significantly longer than many other time constants observed in data centers. When server thermal masses are not negligible, transient scenarios cannot be modeled appropriately with the steady state boundary conditions. By using the time constant and thermal masses of the servers...

Conducting experiments on real high-density computer servers can be an expensive and risky task due to the risks associated with unintended inlet temperatures that exceed the server’s red-line temperature limit. Presented herein is the development of the simulated chassis that mimic real computer servers. Briefly, twelve high-power simulated chassi...