The document discusses a new multiple chiller system installed at a telecommunications data center in Belgrade, Serbia in 2008. The system uses three water chillers equipped with oil-free variable speed turbo compressors, which provide higher energy efficiency than previous systems, especially at partial loads. Testing showed the new system achieved over 35% energy savings compared to the old system and allowed precise temperature regulation and low sound levels. The multiple chiller design provides redundancy and allows reducing energy use further by operating all three chillers at lower speeds to meet cooling demands.
Feedwater Heater Control: Bring Your Efficiency to a New Level -- Kevin Hambrice, Global Factory Sales and Marketing Manager-Level, K-TEK, A Member of the ABB Group
Various parameters affecting the performance of a regeneratorIJESFT
Main objective of this review paper is to show how various parameters affect the performance of regenerator. Performance of regenerator is very important parameter to design it. Various parameters which affect the performance of regenerator have been discussed.
Research Inventy : International Journal of Engineering and Scienceinventy
esearch Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
This paper describes an experimental study of using the waste heat from a Panasonic Under-
Ceiling split room air - conditioner had a rated capacity of 3.51 kW (12,000 Btu/h). An under – ceiling
split type air conditioning for heating domestic water in private homes. Energy recovery improved the
performance, and the recovered energy could replace electricity completely for heating domestic water
use. An extra charge of refrigerant in the air-conditioner could prevent its compressor from over heating
during energy recovery. The experimental conducted on varies capacity of the range from 22.5 litres to
120 litres storage tank. Results show the water temperature increased lies in the range of 50 OC to 65
OC. It was found that, when the initial water temperature in the 22.5 litres storage tank 27 OC, the water
temperature reached 65 OC in 105 minutes. For 120 litres water, temperature increased from 27 OC to 62
OC,5 in 240 minutes.
Feedwater Heater Control: Bring Your Efficiency to a New Level -- Kevin Hambrice, Global Factory Sales and Marketing Manager-Level, K-TEK, A Member of the ABB Group
Various parameters affecting the performance of a regeneratorIJESFT
Main objective of this review paper is to show how various parameters affect the performance of regenerator. Performance of regenerator is very important parameter to design it. Various parameters which affect the performance of regenerator have been discussed.
Research Inventy : International Journal of Engineering and Scienceinventy
esearch Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
This paper describes an experimental study of using the waste heat from a Panasonic Under-
Ceiling split room air - conditioner had a rated capacity of 3.51 kW (12,000 Btu/h). An under – ceiling
split type air conditioning for heating domestic water in private homes. Energy recovery improved the
performance, and the recovered energy could replace electricity completely for heating domestic water
use. An extra charge of refrigerant in the air-conditioner could prevent its compressor from over heating
during energy recovery. The experimental conducted on varies capacity of the range from 22.5 litres to
120 litres storage tank. Results show the water temperature increased lies in the range of 50 OC to 65
OC. It was found that, when the initial water temperature in the 22.5 litres storage tank 27 OC, the water
temperature reached 65 OC in 105 minutes. For 120 litres water, temperature increased from 27 OC to 62
OC,5 in 240 minutes.
Water Efficiency in Thermal power PlantAtanu Maity
Ministry of Environment, Forest and Climate Change (MoEF)
in its recent notification dated December 07, 2015 on
Environment (Protection) Amendment Rules, 2015 have
notified the following:
I. All plants with Once Through Cooling (OTC) shall install Cooling Tower (CT) and achieve specific water consumption upto maximum of 3.5m3/MWh within a period of two years from the date of publication of this notification.
II. All existing CT-based plants shall have to reduce specific water consumption upto maximum of 3.5m3/MWh within a period of two years from the date of publication of this notification.
III. New plants to be installed after 1st January, 2017 shall have to meet specific water consumption upto maximum of 2.5 m3/MWh and achieve zero waste water discharged.
In light of the above a presentation on water consumption in cooling towers / Air Cooled Condensers and other comparisons.
It is related to piping system in Air-condition(AC) or Room heaters. In this slide, you come to know how heated or cooled water transfer from generater to terminal units(heat exchangers).
A REVIEW PAPER ON ANALYSIS OF AUTOMOBILE RADIATORijsrd.com
An Automotive engine cooling system takes out of excess heat produced during engine operation. An automobile cooling system regulates engine surface temperature for engine optimum efficiency. Recent advancement and development in engine for power forced engine cooling system to develop new strategies to improve its performance efficiency. Also to reduce fuel consumption along with controlling engine emission to mitigate environmental pollution norms. This paper throws light on parameters which influence radiator performance along with reviews some of the conventional and modern approaches to enhance radiator performance. This review paper Focus on the various research papers regarding experimental, CFD and Numerical analysis to improving automobile radiator efficiency.
Review on Comparative Study between Helical Coil and Straight Tube Heat Excha...IOSR Journals
The purpose of this study is to determine the relative advantage of using a helically coiled heat
exchanger against a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is
higher as compared to Straight tube due to their shape. Helical coils offer advantageous over straight tubes due
to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a
consequence of the curvature of the coil, which induces centrifugal forces to act on the moving fluid, resulting in
the development of secondary flow. The curvature of the coil governs the centrifugal force while the pitch (or
helix angle) influences the torsion to which the fluid is subjected to. The centrifugal force results in the
development of secondary flow. Due to the curvature effect, the fluid streams in the outer side of the pipe moves
faster than the fluid streams in the inner side of the pipe. The difference in velocity sets-in secondary flows,
whose pattern changes with the Dean number of the flow.
In current work the fluid to fluid heat exchange is taken into consideration, Most of the investigations on heat transfer coefficients are for constant wall temperature or constant heat flux. The effectiveness, overall
heat transfer coefficient, effect of coldwater flow rate on effectiveness of heat exchanger when hot water mass
flow rate is kept constant and effect of hot water flow rate on effectiveness when cold water flow rate kept
constant studied and compared for parallel flow, counter flow arrangement of Helical coil and Straight tube
heat exchangers. The inner heat transfer coefficient calculated from Wilson plot method. Then Nusselt no and
correlation obtained on the basis of inner heat transfer coefficient. All readings were taken at steady state
condition of heat exchanger.
The result shows that the heat transfer coefficient is affected by the geometry of the heat exchanger.
Helical coil heat exchanger are superior in all aspect studied here.
Water Efficiency in Thermal power PlantAtanu Maity
Ministry of Environment, Forest and Climate Change (MoEF)
in its recent notification dated December 07, 2015 on
Environment (Protection) Amendment Rules, 2015 have
notified the following:
I. All plants with Once Through Cooling (OTC) shall install Cooling Tower (CT) and achieve specific water consumption upto maximum of 3.5m3/MWh within a period of two years from the date of publication of this notification.
II. All existing CT-based plants shall have to reduce specific water consumption upto maximum of 3.5m3/MWh within a period of two years from the date of publication of this notification.
III. New plants to be installed after 1st January, 2017 shall have to meet specific water consumption upto maximum of 2.5 m3/MWh and achieve zero waste water discharged.
In light of the above a presentation on water consumption in cooling towers / Air Cooled Condensers and other comparisons.
It is related to piping system in Air-condition(AC) or Room heaters. In this slide, you come to know how heated or cooled water transfer from generater to terminal units(heat exchangers).
A REVIEW PAPER ON ANALYSIS OF AUTOMOBILE RADIATORijsrd.com
An Automotive engine cooling system takes out of excess heat produced during engine operation. An automobile cooling system regulates engine surface temperature for engine optimum efficiency. Recent advancement and development in engine for power forced engine cooling system to develop new strategies to improve its performance efficiency. Also to reduce fuel consumption along with controlling engine emission to mitigate environmental pollution norms. This paper throws light on parameters which influence radiator performance along with reviews some of the conventional and modern approaches to enhance radiator performance. This review paper Focus on the various research papers regarding experimental, CFD and Numerical analysis to improving automobile radiator efficiency.
Review on Comparative Study between Helical Coil and Straight Tube Heat Excha...IOSR Journals
The purpose of this study is to determine the relative advantage of using a helically coiled heat
exchanger against a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is
higher as compared to Straight tube due to their shape. Helical coils offer advantageous over straight tubes due
to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a
consequence of the curvature of the coil, which induces centrifugal forces to act on the moving fluid, resulting in
the development of secondary flow. The curvature of the coil governs the centrifugal force while the pitch (or
helix angle) influences the torsion to which the fluid is subjected to. The centrifugal force results in the
development of secondary flow. Due to the curvature effect, the fluid streams in the outer side of the pipe moves
faster than the fluid streams in the inner side of the pipe. The difference in velocity sets-in secondary flows,
whose pattern changes with the Dean number of the flow.
In current work the fluid to fluid heat exchange is taken into consideration, Most of the investigations on heat transfer coefficients are for constant wall temperature or constant heat flux. The effectiveness, overall
heat transfer coefficient, effect of coldwater flow rate on effectiveness of heat exchanger when hot water mass
flow rate is kept constant and effect of hot water flow rate on effectiveness when cold water flow rate kept
constant studied and compared for parallel flow, counter flow arrangement of Helical coil and Straight tube
heat exchangers. The inner heat transfer coefficient calculated from Wilson plot method. Then Nusselt no and
correlation obtained on the basis of inner heat transfer coefficient. All readings were taken at steady state
condition of heat exchanger.
The result shows that the heat transfer coefficient is affected by the geometry of the heat exchanger.
Helical coil heat exchanger are superior in all aspect studied here.
Automan POS is an Open Source based Retail Management Solution for Independent Retailers. Automan ERP & POS are having data synchronization to import/ export customers and products details.
Automan POS includes several modules:
Point of Sale
Inventory Control
Customer Management
Employee Management
Reports
Store Configuration
Suppliers
Gift Cards
Data synchronization between Automan ERP & POS
Payment
Multiple Themes
Support Multilingual
Peer-to-peer does not just refer to the technical infrastructure that we are building, but to the social relationships that it enables, and which are poised to fundamentally change the logic of our economics and civilization.
Innovation is leaving the exclusive world of the enterprise and democracy is leaving the exclusive world of political representation, in order to be more firmly located within the bottom-up processes of civil society. What will those changes bring as challenges and opportunities?
The presentation on the politics of Web 2.0. will focus on the political implications of value creation by users, and how the potential conflict between private monetazation and common production can play out in the future.
Gestión de Reclamaciones. Los clientes hablan, pero ¿alguien les escucha?
Un cliente satisfecho siempre vuelve. CDC Respond permite demostrar a los clientes que son lo primero, atendemos sus necesidades y los escuchamos.
We proposed to reduce the energy consumption on the air conditioning system in AFGRE facilities (Al Futtaim Real Estate)
We selected the engineering room's office as the AES test site located in the site management offices of Dubai Festival City.
The test was conducted for two days and 8 hours each day.
The AC ran without AES as a normal situation during the first days. However, the AES was connected to AC in the following days to control and optimize the operations.
Also, we have collected some data like the room temperature (electronic thermometer), the temperature targeted (AC), and the room temperature shown on the remote control to keep the same environmental situation during the test.
An air conditioner acclimatizes every room in the site office.
We demonstrated the AES's performance, achieving an energy saving of 20%.
ENERGY SAVINGS IN DOMESTIC REFRIGERATOR USING TWO THERMOELECTRIC MODULES& WAT...ijiert bestjournal
The study deals with hybrid refrigerator that combi nes thermoelectric (TER) and vapor compression refrigeration (VCR) and also entail exp erimental details of combined VCR & TER system. Objective is to configure hybrid refrig erator by introducing two Peltier modules (TER) in domestic refrigerator and to analyze compr essor cycles of conventional refrigerator with TER to increase energy efficiency of vapor com pression cycle. For this comparison of standalone VCR and Hybrid VCR+TER system is carried out. A Peltier module of size 4cm � 4cm � .4cm is introduced in the refrigerator cabinet & t he effect on energy efficiency in terms of trip time of compressor is recorded. The e ffect of Air cooled & Water cooled condenser with TER in different structures is also investigated. It is observed that by introducing thermoelectric effect,energy consumpti on of VCR is reduced by almost 10.92% annually,which accounts for 80 units per year. Thu s ultimately improving COP of the hybrid system with better control on temperature over the total run time.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Performance Enhancement of an Air Conditioner with Condensate Mist Cooled Con...IJMTST Journal
This paper presents a simple and efficient methodology to design a household (and can also be used for
commercial air conditioning purposes) air conditioner, predicts the performance of air conditioning unit and
how the thermal performance can be improved, when the water mist system is coupled with the air cooled
conditioner as a pre-cool for condenser inlet air to increase the cooling capacity, and decrease the compressor
power consumption. Inputs for formulation include inlet air DBT and humidity ratio, air velocity, water
temperature and flow rate, and geometrical properties of evaporative medium. Generally air conditioning
units are used for small and medium scale residential buildings and the large units are used for the
commercial purposes. Therefore, more energy efficiency and lower cost are needed along with reliable control
for the air conditioning units. The influence of condenser and evaporator inlet air temperatures on the cooling
capacity and power consumption has been investigated and presented. It has been found that due to the
coupling of water mist with air cooled condenser, the cooling capacity of the air-cooled,air conditioner can be
increased up to 17.5%, and the compressor power consumption can be reduced up to 15.5%. Thus, it is
concluded that the application of water mist condenser, inlet air pre-cooling could increase the COP by up to
37%, especially when the ambient relative humidity is low[10].
Enhancement of Specific Power Output of a Gas Turbine Using Filtered Chilled AirIOSR Journals
Conventionally the specific power output of the gas turbine can be increased using reheating and
intercooling. The thermal efficiency can be improved by adding a regenerating at lower pressure ratios. In the
present work the emphasis is given to enhance the specific power output by other means like reduction in the air
temperature at the inlet duct. The power output of the gas turbine has been estimated by allowing air at reduced
temperatures, step wise. The experiment is conducted till STP conditions are attained. The chiller coils are used
for inlet air cooling. The variation of power output with respect to temperature is also studied.
EXPERIMENTAL INVESTIGATION OF WASTE HEAT RECOVERY SYSTEM FOR DOMESTIC REFRIGE...IAEME Publication
The objective of this project was to determine the energy savings associated with improved utilization of waste heat from a domestic refrigerator. Domestic refrigerators maybe operate
continuously to maintain proper food storage condition. The continual operation of this equipment accounts more electrical energy consumption. Furthermore, a significant amount of waste heat is rejected by the condensers of refrigerator.
Similar to Data centar cooling using multiple chiller system with r134a (20)
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
De-mystifying Zero to One: Design Informed Techniques for Greenfield Innovati...
Data centar cooling using multiple chiller system with r134a
1. Roundtable on climate & ozone-friendly technologies in refrigeration & air-conditioning
========================================================================
ANNUAL MEETING OF THE REGIONAL OZONE NETWORK
FOR EUROPE & CENTRAL ASIA
BELGRADE, SERBIA, 10-13 MAY 2011
Highly Efficient Data Centar Cooling Using Multiple Chiller System
with Oil-Free Variable-Speed Turbo Compressors
Dipl.-Ing. Slobodan Pejković
Filter Frigo d.o.o.
Serbia – 11050 Belgrade
E-mail=filfrigo@EUnet.rs
ABSTRACT
Oil-free twin-turbo centrifugal compressor uses electromagnetic bearings and turbine variable-speed for
significant increase of energy efficiency at partial load compared to conventional oil-lubricated centrifugal
or screw compressors.
Each of the three water chillers installed in Telecommunication Data Centar 'Belgrade' in April 2008 has
two turbo compressors and total cooling capacity of 1.97 MW. Such design solution with oil-free
compressors was applied for the first time in Serbia as well as in the territory of ex-Yugoslavia. It has
been estimated that in the 2008 cooling season this solution achieved more than 35% energy savings
comparing to the previous solution with conventional centrifugal compressors.
This paper presents the results of preliminary measurement of the working characteristics of chillers and
EER-energy efficiency ratio for real working conditions.
Keywords
Turbocor compressor; oil-free centrifugal compressor; energy efficiency
INTRODUCTION
In the Telecommunication Data Centar 'Belgrade' (Figure 1), back in 1973, water chillers ware installed
(Figure 2) with the conventional oil lubricated turbo compressor. The water chillers used R 12 as
refrigerant.
The engineers from Telecommunication Data Centar 'Belgrade' requested to retrofit the worn-out water
chillers with new, state-of-the-art chillers with an environmentally friendly refrigerant. Due to disturbances
that the old water chillers made in the electric network, especially when starting up the compressors
(starting current of over 500 A) it has been decided to install water chillers with oil-free turbo compressors
with starting current less than 5 A, and R134a as a refrigerant. The advantages of these water chillers
over the conventional ones are:
High energy efficiency, especially during reduced part-load, by use of the oil-free compressors
with the variable-speed turbine and flooded evaporator,
More efficient heat exchange in the evaporator and condenser (with no oil film causing additional
heat resistances),
10. May 2011. Belgrade Page 1
2. Roundtable on climate & ozone-friendly technologies in refrigeration & air-conditioning
========================================================================
Higher evaporation temperatures, and therefore higher cooling capacity at the same
temperatures of the water in the evaporator,
Silent work and reduced vibrations,
Low starting current (2 to 5 A ),
Light compressor weight (up to 140 kg),
Precise temperature regulation thanks to software controlling the compressor.
Figure 1: Telecommunication Data Centar 'Belgrade'
Figure 2: The old water chillers
10. May 2011. Belgrade Page 2
3. Roundtable on climate & ozone-friendly technologies in refrigeration & air-conditioning
========================================================================
BASIC CHARACTERISTICS OF MODERN WATER CHILLERS WITH OIL-FREE
TURBO COMPRESSORS
Basic characteristics that set aside this family of water chillers with water cooled condenser (Figure 3)
from the other water chillers with conventional centrifugal or screw compressors are:
Figure 3: New water chillers with Turbocor compressors
High energy efficiency
In air-conditioning systems, the water chillers operate a smaller part of their time in the maximum load
regime. Therefore, it is very important to know the seasonal energy efficiency ratio, which has been
defined as following:
ESEER - (European Seasonal Energy Efficiency Ratio) is used to define the average annual cooling
efficiency of a water chiller system, and represents a ratio of total cooling energy exchanged in the
evaporator during the year – seasonal use of water chiller, expressed in Wh, in relation to total
absorbed energy used in the same period, expressed in Wh. ESEER is an average value of EERcooling
(Cooling Efficiency Level) during the year, at different external air temperatures, and therefore in
different operating regimes of the device.
This index presents energy efficiency of water chillers in more realistic terms, when compared to the
EER, because time period during the annual operating season, in which the chiller works under full load,
is shorter. Therefore, manufacturers try to develop the devices that would be more efficient during
reduced load conditions. Chillers, with the same cooling efficiency level EER, do not need to have the
same ESEER. A chiller with higher ESEER is more energy efficient.
ESEER is a weighed formula enabling to take into account the variation of EER with the load rate and the
variation of air or water inlet condenser temperature.
10. May 2011. Belgrade Page 3
4. Roundtable on climate & ozone-friendly technologies in refrigeration & air-conditioning
========================================================================
ESEER = 0.03 • A + 0.33 • B + 0.41 • C + 0.23 • D
Where:
A = EER at 100% of load C = EER at 50% of load
B = EER at 75% of load D = EER at 25% of load
In water chillers with water cooled condenser, the ratios are determined for different loads at different
entering water temperatures. For the minimum load (25%), water temperature of 18ºC is adopted, and for
the maximum load (100%), the temperature of 30ºC.
From the quoted above, one can conclude that during the ESEER calculations, the assumption is that the
water chiller works only 3% of time under full load, and 41% of time with 50% load.
From Figure 4, one can see that the water chiller with oil-free Turbocor compressor is more efficient than
the water chillers with screw compressor, especially at loads less than 75%.
Figure 4: Energy efficiency ratio of water chiller at different loads
Sound level of water chillers
Environmental protection is becoming increasingly important in the air-conditioning systems, and
therefore also for water chillers. Sound level of oil-free centrifugal Turbocor compressors, as well as
vibrations which spread from the compressor to the foundations and the bearing construction of the
facility, are much less than the sound level and vibrations originating during the work of water chillers
using screw compressors of the same cooling capacity.
Continuous regulation of the compressor’s cooling capacity
In modern water chillers, water temperature is controlled at the outlet from the evaporator by changing
the speed of the impeller (turbine) and the opening degree of the inlet guide vane - IGV at centrifugal
compressor’s inlet side (Figure 5).
10. May 2011. Belgrade Page 4
5. Roundtable on climate & ozone-friendly technologies in refrigeration & air-conditioning
========================================================================
Impeller
IGV
Figure 5: Cross-section of Turbocor compressor Figure 6: Electromagnetic compressor bearing
In this way the work of the water chiller shall be precisely adapted to the air-conditioning system
dynamics.
Figure 7: Schematic diagram of basic compressor elements
Compressor of small size and small weight is equipped with two impellers driven by electric-motor with
continuous frequency regulation. High-speed variable-frequency operation maintains outstanding part-
load efficiency, compactness and extraordinary soft-start capacity. Compressor’s rotor shaft and
impellers levitate during rotation and float on a magnetic cushion (Figure 6). The rotor shaft position
(Figure 7) is monitored and self-corrected by 10 sensors. Each shaft shift exceeding 0.5μ shall be read
and position correction shall be made accordingly. This technology, which has been transferred from the
space research program, has many advantages:
There is no oil for compressor lubrication, which enables more efficient exchange of heat in
the evaporator and condenser (there is no oil film creating additional heat resistances).
Extended compressor life due to lack of existence of wear surfaces; no metal-to-metal contact
of rotating components.
There are no vibrations in any of the work phases of the water chiller, including start.
The compressor drive motor is a synchronous permanent-magnet brushless DC motor, with
the power of 105 kW, with the size of a conventional fan induction engine, and power of 0.75
kW. It is cooled directly with refrigerant (R134a), works at high speed (20000 to 48000 RPM),
and there is no need for “Soft start system”, and the motor is completely protected.
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Small dimensions and weight (just 140 kg). The screw compressors with the same cooling
capacity are up to 5 times heavier and up to two times bigger in size.
Low starting currents up to 5A, during compressor’s start, instead of 500-600A for screw
compressors of the same cooling capacity.
Shell-and-tube flooded evaporator
The evaporator of the water chiller is the shell-and-tube in its appearance, and is of a flooded by its
function. It has been made of steel shell and a bundle of copper tubes, mechanically expanded in the
steel pipe-plates. The shell is thermally insulated. Thanks to the special drop liquid separator system
there is no possibility for the compressor to suck in liquid refrigerant, and overheating of the refrigerant
at the inlet of the compressor is less than 3K. The level of the liquid refrigerant is controlled and
maintained with the help of special electronic level sensors and by a modular expansion valve. The
water circulates through the bundle of copper tubes, and the refrigerant (R134a) is around the tubes
(Figure 8).
Turbo
Compressor
Evaporator
Condenser
Figure 8: Principal operating scheme for water chiller
This is possible to execute, because there is no oil in the refrigerant, as in conventional oil-lubricated
compressors; oil runs away from the compressor and appears in the refrigerant side of the heat
exchangers (evaporator and condenser). In this way, the refrigerant boiling has been enabled throughout
the total external surface of the copper tube bundle. For this reason, the heat transfer ratio has been
significantly increased, and small temperature difference has been secured between the outlet water
temperature from the evaporator and the evaporating temperature (less than 2K). This results in
increased cooling capacity, with slight increase of absorbed power, leading to an increased energy
efficiency of the water chiller.
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Interactive remote control
By the installed software through local area network, or Internet, one can monitor the work of the water
chiller from any computer anywhere in the world (Figure 9).
Figure 9: Connecting compressor to a computer
THE MAIN PARTS OF OIL-FREE TWIN-TURBO CENTRIFUGAL COMPRESSOR
Figure 10: Turbocor compressor’s main parts
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FACTORY MEASUREMENT OF WATER CHILLER’S WORKING PARAMETERS
Expert team consisting of mechanical and electric engineers from Filter Frigo has attended factory
tests of the water chiller. The tests have been performed on April 3rd, 2008 in the test cabin no. 3
(Figure 11).
Table 1 shows calculated cooling capacity and absorbed powers at different loads of the water chiller
and different water temperatures for condenser cooling.
The results of the measurements for one of three water chiller have been presented in Table 2.
Figure 11: Test cabin no. 3
Water Chiller TECS-HF 2AS
Load % 100 66 50 33
Cooling capacity kW 657.4 433.88 328.7 216.94
Total absorbed power kW 128.4 57.5 34.2 20.7
EER Wh/Wh 5.11 7.55 9.61 10.47
Water entering the evaporator °C 14 12.3 11.5 10.6
Water exiting the evaporator °C 9 9 9 9
Water flow through the 3
m /h 113.2
evaporator
Water entering the condenser °C 29.5 26 22 18
Water exiting the condenser °C 34 28.8 24.1 19.4
Water flow through the
m3/h 149.7
condenser
Table 1: Calculated operating parameters of the water chiller
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Table 2: Original factory testing report of the water chiller TECS-HF 2AS
FACILITY REQUIREMENT FOR COOLING
For cooling of equipment and air-conditioning in the building of Telecommunication Data Centar
'Belgrade', a total cooling capacity is needed of 1.2 MW. For those requirements, three water chillers,
with water cooled condensers were selected, each with cooling capacity of 658 kW, in the following work
regimes:
Water temperature at the evaporator inlet 14ºC
Water temperature at the evaporator outlet 9ºC
Water temperature at the condenser inlet 29ºC
Water temperature at the condenser outlet 34ºC
The installed capacity is much higher (1.97 MW) than needed, due to the reason of redundancy
safeguards. Processor (Manager 3000, shown in Figure 12), controls the work of all three water chillers.
The simultaneous work of all three water chillers was enabled at reduced load, when the electric power
consumption has been significantly decreased.
Regulation of the cooling capacity of the water chillers (from 10% to 100%) is executed in two ways:
By changing the speed of the turbine, according to factory data from 20000 to 48000 min¯¹.
Measured from 22500 to 34000 min¯¹.
By changing the opening degree of the inlet guide vane - IGV at the inlet side of the compressor.
It was found that combined regulation has a good performance.
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Figure 12: Processor for controlling the work of three water chillers
When two water chillers operate at high external temperatures, in order to satisfy the cooling requirement
(Figure 13), their total cooling capacity is 2 x 612.6 = 1225.2 kW, while the absorbed power is 2 x 139.8
= 279.6 kW. The cooling capacity is less than nominal, and the absorbed power is higher, due to higher
temperature of water for cooling of the condenser. The condensing temperature is tk = 40ºC (Table 4,
page 16, the first column).
When all three water chillers operate at decreased speed in order to satisfy the same cooling
requirement, their total cooling capacity is 3 x 407.5 = 1222.5 kW, while the absorbed power is 3 x 64.0 =
192.0 kW, that is 31% less. The condensing temperature is tk = 32ºC (Table 3, page 15).
The use of Multiple Chiller System allows unusual redundancy safeguards.
100% 100%
33.3% 31%
80% 50% 50% 80%
23%
60% 33.3%
60%
40% 23%
40%
50% 50% 20% 33.3%
23%
20%
0%
0% Cooling capacity Absorbed power
Cooling capacity Absorbed power
Water Chiller I Water Chiller II
Water Chiller I Water Chiller II Water Chiller III Energy savings
Figure 13: Comparative presentation of energy consumption, if two or three water chillers
are operational for the same cooling capacity
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These values have encouraged us to determine the annual seasonal energy consumption by calculation
for the data center cooling, using multiple chiller system.
Three cases have been discussed in order to be able to determine an optimum operating method for the
system. Cooling of equipment in the winter is working in the free cooling mode.
The first case is the analysis of the work of an old Westinghouse water chiller, with cooling capacity of 1.2
MW, with conventional oil-lubricated centrifugal compressor. According to the method recommended by
KGH (Serbian Society for HVAC&R), we have assumed that the water chiller operates only 240 days a
year, 14 hours per day. The calculated seasonal electric power consumption is 571200 kWh during the
year. For securing the facility requirement for the cooling, only one water chiller was used, and the other
served as a reserve.
The second discussed case is a parallel work of two new water chillers with Turbocor compressors.
During that, the third water chiller serves as a reserve. For the same number of hours of work, as in the
previous case, the seasonal energy consumption is 364800 kWh, which is 36% less than in the first case.
The third case is the parallel operation of all three new water chillers. For the same number of hours,
seasonal energy consumption was 212600 kWh, which is 63% less than in the first case.
According to the world price lists for electricity utilization, the financial effects, that is, annual savings in
this operating regime of the water chillers would be $37650. The current project indicates a simple
payback for the third water chiller of approximately 2.5 years.
MEASUREMENT OF CHILLER WORKING PARAMETERS IN THE FACILITY
The measurements have been performed in August and on October 14th, 2008.
Measuring equipment
For basic measurement of temperatures and pressures, the measuring equipment which has been
installed in the factory in water chillers, has been used.
For control measurements of temperatures and pressures, the measuring equipment, product of
ROBINAIR, has been used.
For indirect measurements of the speed of turbine, opening degree of inlet guide vane - IGV and for
determining the requested load of the water chiller, a computer has been used (Figure14) with the
software package from »Danfoss Turbocor Monitoring Tool Version 2.1.0.80«.
For electrical network characteristics measurement, instrument CHAUVIN ARNOUX C.A 8334 has been
used (Figure 15).
For basic measurement of the water flow rate orifice meter have been used in conection with
OVENTROP flow-meter OV-DMC 2 (Figure 16).
For control measurement of water flow rate, the ultrasonic flow-meter UFM 610P has been used, product
of KROHNE (Figure 16).
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Figure 14: Measuring equipment Figure 15: Instrument
CHAUVIN ARNOUX C.A 8334
Figure 16: Instrument OVENTROP OV-DMC 2 and ultrasonic flow-meter KROHNE UFM 610P
By detailed measurement and analysis of current characteristics of the water chiller, the influence of the
variable speed electric motor has been observed to so-called “defilement“ of power grid.
From the voltage diagram (Figure 17), it can be observed that there is small voltage distortion because
voltage oscillograms are not ideal sinusoids.
From the current intensity diagram, one can observe that the currents in phases are symmetrical.
Simultaneously, this diagram shows that there is serious current distortion, because the current
oscillograms are not ideal sinusoids, but have in each semi-period two symmetrical peaks, resulting from
higher odd harmonics (Figure 17).
In other words, good characteristics, like soft start (maxigraph compensation) and speed regulation,
which is the compressor cooling capacity regulation, have for their consequence, the current and voltage
distortion. This results in an appearance of interferences in the form of higher harmonics of voltage and
current. In installations where such level of higher harmonics might cause problems, we use filters, based
on inductive chokes mounted in the compressor’s power line.
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Figure 17: Results of the electrical parameters measuring (power, cosφ, voltage, current intensity)
The measurements show that by decreasing the speed of the turbine, power factor - cosφ also
decreases, and it increases the percentage of reactive power in apparent power. Considering the costs of
the reactive power, reactive power should be compensated. On the other hand, low starting current (up to
5A) does not cause problems with »peaks« and it does not switch on maxigraph, which in conventional
water chillers with starting currents from 500A to 600A significantly influences the price of the consumed
electricity.
The software package »Danfoss Turbocor Monitoring Tool Version 2.1.0.80« offers possibilities for
monitoring different parameters in the work of Turbocor compressor. From the program the operator can
open up different windows, some of which were presented in the Figures 18, 19 and 20.
Figure 18
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Figure 19
Figure 20
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Table 3 shows the results of measuring the working parameters of water chiller no.2 at high external
temperatures (measured in August 2008). The water chillers no.1 and no.3 were in simultaneous
operation.
Water Chiller: TECS-HF 2S Compressors: Date:
Φo=658 kW ; Pw=130 kW ; tw=14/9°C TT300 (R134a) 12/08/2008.
Outside Air Temperature 37.9ºC
Parameters
Discharge Pressure [kPag] 702
Condensing Temperature [°C] 32
Discharge Temperature [°C] 38.5
3
Water Flow (Condenser) [m /h] 126.3
Water Temp. (Cond. Inlet) [°C] 25.7
Water Temp. Difference-Cond. [K] 3.1
Heating Capacity [kW] 455.3
Suction Pressure [kPag] 290
Suction Temperature [°C] 7.6
3
Water Flow (Evaporator) [m /h] 129.8
Water Temp. (Evap. Outlet) [°C] 9.0
Water Temp. Difference-Evap. [K] 2.7
Cooling Capacity [kW] 407.5
-1
Shaft Speed [min ] 27371
Compressor load [%] 34
IGV (Inlet Guide Vane) open [%] 110
Power Input [kW] 64.0
Cosφ - 0.893
EER - 6.4
Table 3: Results of measuring the working parameters of water chiller no.2
The compressors worked with completely opened inlet guide vane - IGV, and with reduced impeller’s
-1
speed of 27371 min . Because the condenser’s load was below 70%, this enabled the compressor to
operate at condensing temperature of 32ºC and the efficiency level - EER should be significantly
increased (6.4).
Table 4 shows the results of measuring the working parameters of water chiller no.2 at different loads.
During the measurement opening degree of inlet guide vane – IGV was changing from 110 to 8.8%, as
well as the compressor impeller’s speed from 33978 to 22520 min-1. The efficiency level - EER changed
from 4.4 at maximum load to 9.1 at reduced capacity of 34% of the maximum load. By further decrease
of load, the efficiency level - EER would also increase.
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Water Chiller: TECS-HF 2S Compressors: Date: Outside Temp.
Φo=658 kW ; Pw=130 kW ; tw=14/9°C TT300 (R134a) 14/10/2008. 21°C
Parameters / Time 12:48 13:08 13:16 14:15 14:34 15:32 15:37
Discharge Pressure [kPag] 887 793 769 702 618 613 595
Condensing Temperature [°C] 40 36 35 32 28 27 26
Discharge Temperature [°C] 50.5 47.4 41.2 36.2 33.8 32.8 32.0
3
Water Flow (Condenser) [m /h] 126.1 125.8 125.6 125.6 125.9 125.8 126.3
Water Temp. (Cond. Inlet) [°C] 26.6 25.2 25.4 24.3 24.0 23.5 23.1
Water Temp. Difference-Cond. [K] 5.0 4.7 3.7 2.6 1.8 1.5 1.4
Heating Capacity [kW] 733.1 687.5 540.4 379.7 263.5 219.4 205.6
Suction Pressure [kPag] 3.0 2.67 2.8 2.89 2.92 2.95 2.98
Suction Temperature [°C] 9.2 5.9 7.0 7.6 8.2 9.1 9.2
3
Water Flow (Evaporator) [m /h] 128.5 129.8 129.5 129.8 129.1 128.8 129.4
Water Temp. (Evap. Outlet) [°C] 11.3 8.7 8.7 8.9 8.8 8.8 8.9
Water Temp. Difference-Evap. [K] 4.1 3.9 3.2 2.2 1.6 1.4 1.3
Cooling Capacity [kW] 612.6 588.6 481.9 332.0 240.2 210.0 195.6
-1
Shaft Speed [min ] 33802 33978 29182 25434 23784 22907 22520
Compressor load [%] 90 74.8 42.8 26.8 10 10 11.7
IGV (Inlet Guide Vane) open [%] 110 110 110 110 23.6 8.8 8.8
Power Input [kW] 139.8 130.8 78.5 46.5 30.8 23.2 21.6
Reactive power [kVAR] 60.6 56.9 36.6 26.6 21.3 19.2 18.2
Cosφ - 0.917 0.916 0.906 0.867 0.822 0.771 0.762
EER - 4.4 4.5 6.1 7.1 7.8 9.0 9.1
Table 4: Results of measuring the working parameters of water chiller no.2
Pumps for circulation of cold (evaporator) and cooling (condenser) water
Each of the water chillers has its own pair of pumps. Pump for circulating water through the evaporator
shall start its operation before the start of the first compressor in the water chiller, and the pump for
circulation of the water through the condenser, shall start when the condensing pressure reaches the set
value. These pumps are important consumers of electricity and haven’t been calculated in when
determining the efficiency level - EER.
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CONCLUSION:
Oil-free twin-turbo centrifugal compressor uses electromagnetic bearings and a variable-
speed turbine for significant increase of energy efficiency at partial load compared to the
previous solution with conventional centrifugal compressor.
Water chillers with water cooled condenser offer high energy efficiency level - EER at the
highest external temperatures, because the water chillers operate with condensing
temperature up to 40ºC.
Part load energy efficiency is outstanding, with energy savings greater than 35% compared
to the conventional oil-lubricated centrifugal or screw compressors.
Totally oil-free operation has improved the heat transfer efficiency.
Extended equipment life was provided with minimal scheduled maintenance.
The current project indicates a simple payback for the third water chiller of approximately 2.5
years.
The Multiple Chiller System allows unusual redundancy safeguards with energy savings
greater than 35%.
Reduced energy consumption provides a way to reduce utility generated greenhouse gas
emissions.
Literature:
1. Određivanje, klasifikovanje i označavanje energetske efikasnosti agregata za hlađenje vode i
toplotnih pumpi,
Slobodan Pejković - Vladimir Živanović, Filter Frigo d.o.o., Belgrade
2. Danfoss Turbocor, USCO 7.2008
3. Water cooled liquid chiller SerieTECS-HF / TECS-HFD,
Cod: B100AS_120_220B_CV_06_06_IT_GB,
CLIMAVENETA
4. www.turbocor.com
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