Impacts on Building Return Water Temperature in District Cooling Systems

Solar Energy ◽  
2006 ◽  
Author(s):  
Gang Wang ◽  
Bin Zheng ◽  
Mingsheng Liu
Keyword(s):  
Water Supply ◽  
Water Temperature ◽  
Control Method ◽  
Cost Effective ◽  
Cooling Systems ◽  
Return Water ◽  
Chilled Water ◽  
Coil Performance ◽  
Cooling Coil ◽  
The Impact

A high temperature differential between supply and return water is most cost effective in district cooling systems. The chilled water supply temperature relies on central plant operation while the chilled water return temperature mainly depends on cooling coil performance of air handling units (AHU) at consumers. Many factors affect the AHU cooling coil performance at the consumers, such as cooling coil size, chilled water supply temperature, AHU supply air temperature, space cooling load, outside airflow and conditions, cooling coil fouling condition and cooling coil control valves types. The AHU chilled water return temperature may deviate from its design valve under off-design conditions. The common method to maintain the required consumer chilled water return temperature is to install a bypass bridge between the chilled water supply and return at consumer connections. This paper studies the impact of these factors on the AHU chilled return water temperature and finally develops the improved chilled water return temperature control method.

Energy Use and Performance of a New Variable Primary-Flow Chilled Water System

Solar Energy ◽  
2005 ◽  
Author(s):  
Li Song ◽  
Ik-Seong Joo ◽  
Mingsheng Liu
Keyword(s):  
Pump Power ◽  
Water Supply ◽  
Water Flow ◽  
Water System ◽  
Variable Flow ◽  
Chilled Water ◽  
Flow Through ◽  
Compressor Power ◽  
Cooling Coil

The traditional chilled water loop has been designed as a primary/secondary (P/S) system for several years. The primary loop maintains constant chilled water flow through the evaporator, and the secondary loop is designed as a variable flow system in response to variations in building cooling load. The primary/secondary design separates the chiller operation from the building load requirements. This design principle has been working adequately for old chillers that require constant chilled water flow to achieve stable chiller performance. However, these chillers operate inefficiently and consume unnecessary pump power. In recent years, the chiller industry has begun the use of variable water flow through evaporators. Significant energy savings can be achieved by using the variable flow principle. This paper compares the P/S system with variable chilled water system and also proposes an innovative solution: chilled water supply temperature reset to maintain the minimum chilled water flow and eliminate by-pass water flow. The energy consumption models including pump power and chiller compressor power improvement are presented to simulate the energy performance of two systems. ASHRAE detailed cooling coil models are also adopted to simulate the cooling coil discharge air humidity in order to verify the impacts of the chilled water supply temperature reset. Finally, a case study building demonstrates experimental results. Up to 10% pump and compressor power saving is demonstrated by simulations and the case study.

A Model-Based Feed-Forward Controller Scheme for Accurate Chilled Water Temperature Control of Inlet Guide Vane Centrifugal Chillers

2002 ◽  
Author(s):  
Yongzhong Jia ◽  
T. Agami Reddy
Keyword(s):  
Water Temperature ◽  
Temperature Sensor ◽  
Control Method ◽  
Discrete Control ◽  
Model Parameters ◽  
Simple Method ◽  
Feed Forward ◽  
Control Scheme ◽  
Centrifugal Chillers ◽  
Chilled Water

Capacity control in most commercial centrifugal chillers is achieved by inlet guide vanes, which are activated by the leaving chilled water temperature sensor. Due to mechanical reasons, vane control is done discretely, and not continuously. The control module compares the value provided by the temperature sensor to pre-set control band values, and if those bands are exceeded, it sends a signal to the vane control motor to adjust the vane position by one step that could be upwards or downwards. The advantage of this type of discrete control method is its simplicity. Normally, the accuracy in the outlet chilled water temperature is of the order of 0.5°C, which is acceptable for normal cooling plants such as used in office buildings. However, there are applications such as in pharmaceutical processes, mechanics labs, or instances in chemical processes where more accurate control is required (sometimes as low as 0.05°C). This paper proposes a simple method to achieve such tight control without any hardware modifications. The basis of this method is a transient physical inverse model of the refrigerant boiling process in the evaporator, in conjunction with a feed-forward control scheme. The model parameters need to be identified from monitored data since they are chiller-specific. This paper describes the model, and applies it to one-minute monitored data from an actual chiller plant of 1580 kW (450 Tons). It is demonstrated that for this specific chiller such a control scheme has the potential to improve control accuracy by about 28% as compared to the traditional control method.

An application of thermal exermal analysis to the development of mine cooling systems

2002 ◽  
Vol 216 (8) ◽  
pp. 845-857 ◽  
Author(s):  
C T Twort ◽  
I S Lowndes ◽  
S J Pickering
Keyword(s):  
Water Distribution ◽  
Cooling System ◽  
Ventilation System ◽  
Cost Effective ◽  
Mine Ventilation ◽  
Distribution Networks ◽  
Ventilation Network ◽  
Generic Model ◽  
Cooling Systems ◽  
Chilled Water

The extraction of minerals and coal at greater depth, employing higher-powered machinery to improve production levels, imposes an increased burden on the ability of a ventilation system to maintain an acceptable mine climate. Hence, mechanical mine cooling systems are often adopted, which can be expensive both in terms of their associated capital and operating costs. Consequently, in order to optimize the costs it is essential to provide the mine operator with a method with which to determine the most cost effective and efficient mine cooling system. The following paper overviews the development of a novel approach to the energy analysis of mine cooling systems using the concepts of thermal exergy analysis. Generic model mine ventilation networks are constructed and the subsurface environments of these mine networks predicted. Models of various cooling system methods are developed and applied to control the underground climate within these mine networks to within pre-set climatic limits. The exergy transfers that are produced by the application of the different cooling methods are compared using performance indices. Models to represent chilled water distribution networks, used to supply the air coolers within the various cooling systems, are designed and balanced. The results of the exergy analyses applied to the operation of the various chilled water pipe networks are discussed and used to assess the exergetic performance of the application of each cooling system to the mine ventilation network.

scholarly journals A Study on the Energy Reduction Measures of Data Centers through Chilled Water Temperature Control and Water-Side Economizer

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3575
Author(s):  
Yu-Jin Kim ◽  
Ju-Wan Ha ◽  
Kyung-Soon Park ◽  
Young-Hak Song
Keyword(s):  
Energy Consumption ◽  
Water Temperature ◽  
Data Center ◽  
Cooling System ◽  
Water Control ◽  
Cooling Systems ◽  
Efficient Operation ◽  
Water Side ◽  
Chilled Water ◽  
Active Research

The degree of integration of IT devices and consumption of cooling energy are consistently increasing owing to developments in the data center industry. Hence, to ensure the smooth operation and fault prevention of IT devices, the energy consumption of cooling systems has increased, leading to active research on improvements in cooling system performance for reducing energy consumption. This study examines the reduction in cooling energy consumption using a simulation by applying chilled water control and a water-side economizer (WSE) system to enhance the cooling system efficiency. The simulation results showed that the energy consumption was reduced by 1.8% when the chilled water temperature was set to 11 °C in a conventional system and by up to 19.6% when WSE was also applied. Furthermore, when the changes in chilled water temperature were applied for efficient operation of WSE, the energy consumption was reduced by up to 30.1% compared to that in conventional energy systems.

The impact of climate changes on the aquatic system chemistry in the Kyiv Reservoir and the Desna river (Ukraine)

2020 ◽  
Author(s):  
Valeriy Osypov ◽  
Volodymyr Osadchyi ◽  
Natalia Osadcha ◽  
Olha Ukhan ◽  
Nina Mostova
Keyword(s):  
Drinking Water ◽  
Water Supply ◽  
Water Chemistry ◽  
Water Temperature ◽  
Air Temperature ◽  
Ice Cover ◽  
Drinking Water Supply ◽  
Summer Period ◽  
The Impact ◽  
System Chemistry

<p>The Kyiv Reservoir and the Desna river are the main sources of drinking water supply for Kyiv, the capital of Ukraine. The impact of surface air temperature on the change of the aquatic system chemistry mentioned above water objects was studied based on long-term regular observations (1995–2018).</p><p>The findings are based on the analysis of daily air and water temperature, water pH, oxygen and carbon dioxide concentrations, water color index, dissolved organic substances (COD<sub>Mn</sub>), Fe, Mn, and phytoplankton abundance (without identifying their species composition).</p><p><strong>The winter period. </strong>Despite different hydraulic conditions in the Kyiv Reservoir and in the Desna river, the lack of ice cover due to an increase in winter air temperatures (December-February) led to significant improvement of the water oxygen regime in recent years. This fact, as well as the subsequent chain of changes in the water chemistry, contributed to the cheaper drinking water supply.</p><p>The ratio of the oxygen content change to the duration of the ice cover, determined by air temperature, was obtained. This allowed us to reconstruct years with observed hypoxia phenomena since 1850. Changes in the water chemistry, triggered by oxygen deficit, were described.</p><p><strong>The summer period. </strong>The increase in summer air temperature led to a decrease in oxygen concentrations. It had the effect of slowing down the process of N-NH<sub>4</sub><sup>+</sup> nitrification. Because of the high content of natural organic matters in these water bodies, dangerous hypoxia phenomena were reported in summertime. Such conditions contributed to the restoration of manganese to a mobile Mn<sup>2+</sup>.</p><p>All these features created additional difficulties at water treatment plants for supplying drinking water to residents of Kyiv.</p><p>In shallow waters, occupying almost half of the Kyiv Reservoir, an increase in water temperature during the summer period led to the intensification of the hydrobiological processes and “water blooming.” This is compounded by the high income of nitrogen and phosphorus from the point and diffuse sources.</p><p>The observed decrease in the Dnieper water flow does not allow the active use of releases from the Kyiv Reservoir. The only way to minimize negative consequences in the future is to prevent pollution and eliminate shallow water zones.</p><p>This is complicated by the fact that a significant amount of nitrogen compounds enters the Kyiv Reservoir with the water of its main tributary, Pripyat, which basin is highly marshy.</p><p>Dredging in the shallow areas will require further research because of the bedding of radionuclides of Chernobyl in the bottom sediments.</p>

A Model-Based Feed-Forward Controller Scheme for Accurate Chilled Water Temperature Control of Inlet Guide Vane Centrifugal Chillers

2005 ◽  
Vol 127 (1) ◽  
pp. 47-52 ◽  
Author(s):  
Yongzhong Jia ◽  
T. Agami Reddy
Keyword(s):  
Water Temperature ◽  
Temperature Sensor ◽  
Control Method ◽  
Discrete Control ◽  
Model Parameters ◽  
Simple Method ◽  
Feed Forward ◽  
Control Scheme ◽  
Centrifugal Chillers ◽  
Chilled Water

Capacity control in most commercial centrifugal chillers is achieved by inlet guide vanes which are activated by the leaving chilled water temperature sensor. Due to mechanical reasons, vane control is done discretely, and not continuously. The control module compares the value provided by the temperature sensor to pre-set control band values, and if those bands are exceeded, it sends a signal to the vane control motor to adjust the vane position by one step which could be upwards or downwards. The advantage of this type of discrete control method is its simplicity. Normally, the accuracy in the outlet chilled water temperature is of the order of 0.5°C, which is acceptable for normal cooling plants such as used in office buildings. However, there are applications such as in pharmaceutical processes, mechanics labs, or instances in chemical processes where more accurate control is required (sometimes as low as 0.05°C). This paper proposes a simple method to achieve such tight control without any hardware modifications. The basis of this method is a transient physical inverse model of the refrigerant boiling process in the evaporator, in conjunction with a feed-forward control scheme. The model parameters need to be identified from monitored data since they are chiller-specific. This paper describes the model, and applies it to one-minute monitored data from an actual chiller plant of 1580 kW (450 Tons). It is demonstrated that for this specific chiller such a control scheme has the potential to improve control accuracy by about 28% as compared to the traditional control method.

Regulatory and sustainability initiatives lead to improved polyaminopolyamide epichlorohydrin (PAE) wet-strength resins and paper products

TAPPI Journal ◽  
2018 ◽  
Vol 17 (09) ◽  
pp. 519-532 ◽  
Author(s):  
Mark Crisp ◽  
Richard Riehle
Keyword(s):  
Health And Safety ◽  
Cost Effective ◽  
Worker Safety ◽  
Regulatory Requirements ◽  
Wet Strength ◽  
The Past ◽  
Consumer Safety ◽  
Federal Institute ◽  
Sustainability Initiatives ◽  
The Impact

Polyaminopolyamide-epichlorohydrin (PAE) resins are the predominant commercial products used to manufacture wet-strengthened paper products for grades requiring wet-strength permanence. Since their development in the late 1950s, the first generation (G1) resins have proven to be one of the most cost-effective technologies available to provide wet strength to paper. Throughout the past three decades, regulatory directives and sustainability initiatives from various organizations have driven the development of cleaner and safer PAE resins and paper products. Early efforts in this area focused on improving worker safety and reducing the impact of PAE resins on the environment. These efforts led to the development of resins containing significantly reduced levels of 1,3-dichloro-2-propanol (1,3-DCP) and 3-monochloropropane-1,2-diol (3-MCPD), potentially carcinogenic byproducts formed during the manufacturing process of PAE resins. As the levels of these byproducts decreased, the environmental, health, and safety (EH&S) profile of PAE resins and paper products improved. Recent initiatives from major retailers are focusing on product ingredient transparency and quality, thus encouraging the development of safer product formulations while maintaining performance. PAE resin research over the past 20 years has been directed toward regulatory requirements to improve consumer safety and minimize exposure to potentially carcinogenic materials found in various paper products. One of the best known regulatory requirements is the recommendations of the German Federal Institute for Risk Assessment (BfR), which defines the levels of 1,3-DCP and 3-MCPD that can be extracted by water from various food contact grades of paper. These criteria led to the development of third generation (G3) products that contain very low levels of 1,3-DCP (typically <10 parts per million in the as-received/delivered resin). This paper outlines the PAE resin chemical contributors to adsorbable organic halogens and 3-MCPD in paper and provides recommendations for the use of each PAE resin product generation (G1, G1.5, G2, G2.5, and G3).

Exploring the Benefits of Early Contractor Involvement (ECI) and the Mechanism for Automated 5D BIM Quantification Process in Offsite Modular Construction

2016 ◽  
Author(s):  
Tochukwu Moses ◽  
David Heesom ◽  
David Oloke ◽  
Martin Crouch
Keyword(s):  
Effective Means ◽  
Cost Effective ◽  
Modular Construction ◽  
Automated Quantification ◽  
Building Information ◽  
Project Risks ◽  
Value Add ◽  
The Uk ◽  
The Impact ◽  
Level 2

The UK Construction Industry through its Government Construction Strategy has recently been mandated to implement Level 2 Building Information Modelling (BIM) on public sector projects. This move, along with other initiatives is key to driving a requirement for 25% cost reduction (establishing the most cost-effective means) on. Other key deliverables within the strategy include reduction in overall project time, early contractor involvement, improved sustainability and enhanced product quality. Collaboration and integrated project delivery is central to the level 2 implementation strategy yet the key protocols or standards relative to cost within BIM processes is not well defined. As offsite construction becomes more prolific within the UK construction sector, this construction approach coupled with BIM, particularly 5D automated quantification process, and early contractor involvement provides significant opportunities for the sector to meet government targets. Early contractor involvement is supported by both the industry and the successive Governments as a credible means to avoid and manage project risks, encourage innovation and value add, making cost and project time predictable, and improving outcomes. The contractor is seen as an expert in construction and could be counter intuitive to exclude such valuable expertise from the pre-construction phase especially with the BIM intent of äóÖbuild it twiceäó», once virtually and once physically. In particular when offsite construction is used, the contractoräó»s construction expertise should be leveraged for the virtual build in BIM-designed projects to ensure a fully streamlined process. Building in a layer of automated costing through 5D BIM will bring about a more robust method of quantification and can help to deliver the 25% reduction in overall cost of a project. Using a literature review and a case study, this paper will look into the benefits of Early Contractor Involvement (ECI) and the impact of 5D BIM on the offsite construction process.

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