Variable Water Flow Pumping for Central Chilled Water Systems

2002 ◽  
Vol 124 (3) ◽  
pp. 300-304 ◽  
Author(s):  
M. Liu
Keyword(s):  
Pump Power ◽  
Flow System ◽  
Water System ◽  
Water Systems ◽  
Analytical Models ◽  
Partial Load ◽  
Chilled Water ◽  
And Control ◽  
Variable Water ◽  
Load Conditions

A new variable water (VW) flow system for chilled water system application is presented. Design, operational, and control issues are discussed. Analytical models of pump power and evaporative temperature are developed. The VW systems consume considerably less pump and compressor energy than the primary secondary (PS) systems under partial load conditions for most existing chillers. The VW system consumes less compressor energy since it results in higher refrigerant temperature in the evaporator. The VW systems also have the decoupling capability of the primary and secondary pumping systems.

Development of the Chilled Water System Analysis Tool for Assessing Energy Conservation Opportunities

2013 ◽  
Author(s):  
Ghanshyam Gaudani ◽  
Alex Quintal ◽  
Dragoljub Kosanovic
Keyword(s):  
Energy Consumption ◽  
Cost Reduction ◽  
Air Conditioning ◽  
System Analysis ◽  
Water System ◽  
Water Systems ◽  
Analysis Tool ◽  
Chilled Water ◽  
System Energy ◽  
Chilled Water System

Chilled water systems constitute a major portion of energy consumption in air conditioning systems of the large buildings and process cooling of the manufacturing plants. These systems do not operate optimally in most of the cases because of the operating parameters set and/or the components used. The Chilled water system analysis tool software (CWSAT) is developed as a primary screening tool for energy evaluation. This tool quantifies the energy usage of the various chilled water systems and typical measures that can be applied to these systems to conserve energy. The tool requires minimum number of inputs to analyze the component-wise energy consumption and incurred overall cost. Both air-cooled and water-cooled systems can be analyzed with this tool; however, this paper focuses on water-cooled systems. The tool uses weather data of the chilled water system location and loading schedules to calculate the chilled water system energy consumption. The Air-Conditioning and Refrigeration Institute (ARI) standard 550/590 typical loading schedule is also incorporated for the chiller(s) loading. The tool is capable of comparing economics by analyzing the energy consumption and relevant cost of the existing system and the new system with cost reduction opportunities considered like: (1) increase chilled water temperature set point, (2) lowering the condenser cooing water supply temperature set point, (3) replace chiller(s), (4) Apply variable speed control to chilled and/or condenser water pumps, (5) upgrade cooling tower fan speed control, (6) Use free cooling when possible for water-cooled systems. The savings can be calculated separately for each cost reduction opportunity or can be combined. The economics comparison can be a primary decision criterion for further detailed engineering and cost analysis related with system changes. The comparison between actual system energy consumption and CWSAT results are also shown.

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.

Chiller Condenser Service Water Cooling Valve Maintenance

2008 ◽  
Author(s):  
Ken Boughton ◽  
Paul N. Hansen
Keyword(s):  
Flow Control ◽  
Water Flow ◽  
Water System ◽  
Cooling Water ◽  
Control Valves ◽  
Service Water ◽  
Low Load ◽  
Chilled Water ◽  
Chilled Water System ◽  
Load Conditions

This paper presents issues associated with Chilled water system operations at a Nuclear facility that experiences problems with the cooling water flow control valves during the cold season under low load conditions. The system is used to provide safety related functions of cooling rooms such as the control rooms due to radioactive and toxic gas hazards. The valves experience excessive cycling under low load conditions during the cold seasons leading to maintenance and availability problems with the system. This problem is driven by the current system design and the need to utilize a chilled water system during times when natural ambient temperature conditions are low. The Chilled water system uses refrigeration units to cool the chilled water and service water to provide the heat sink for the refrigeration condensing units. The focus of the discussion is the cooling water (service water) flow control valves, which are the major source of the maintenance problem. The paper presents the integrated behavior of the Chilled water system to properly characterize the issue and the solutions. The paper will present the system details and performance parameters necessary to evaluate the problem. The behavior of the valves will be evaluated based on the system operations. This paper evaluates the technical merits of several options to provide stable control of the flow control valves, prevent high-pressure chiller unit trips and solve flow control valve actuator excessive wear.

scholarly journals Variable flow and optimization of chiller loading effect on energy saving for screw vapor compression-single effect absorption hybrid chiller plant in hospital mechanical room ‒ case study: Tehran heart hospital

2021 ◽  
Vol 22 ◽  
pp. 9
Author(s):  
Ronald Boghosian ◽  
Mostafa Mafi ◽  
Mohammad Hassan Panjeshahi ◽  
Abtin Ataei
Keyword(s):  
Energy Consumption ◽  
Energy Saving ◽  
Water Flow ◽  
Flow System ◽  
Vapor Compression ◽  
Absorption Chillers ◽  
Partial Load ◽  
Energy Consuming ◽  
Single Effect ◽  
Variable Water

Chiller plants are the most energy consuming system during summer season in residential, commercial and hospital buildings. The highly variable cooling demand of the buildings connected to a hybrid chiller plant included absorption and vapor compression chillers to achieve higher energy efficiencies is one of the important issues. Cooling load sharing strategies and apply the variable water flow system in chiller plant have a significant impact on energy consumption and consequently with more productivity and environmentally protected. This paper examines the behavior and pattern of energy consumption in a hybrid chiller plant that includes a combination of two air-cooled screw vapor compression and three single effect absorption chillers. In order to properly understand the pattern of energy consumption, an existing mechanical room in a hospital in Tehran has been studied for five months, and its energy consumption has been compared with the optimized model. The results indicate that the sequence of the chiller function and the way in which they are placed in the circuit during a partial load, is in highest importance in view point of energy saving also by Applying of variable water flow system for optimized chiller loading the more energy saving is achieved for hybrid absorption and vapor compression chiller plant.

scholarly journals A Modelling and Control Approach for a Type of Mixed Logical Dynamical System Using in Chilled Water System of Refrigeration System

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Yan Zhang ◽  
Xiaoli Chu ◽  
Yang Liu ◽  
Yongqiang Liu
Keyword(s):  
Energy Saving ◽  
Hybrid System ◽  
Air Conditioning ◽  
Water System ◽  
Cooling Capacity ◽  
Chilled Water ◽  
Central Air Conditioning ◽  
Chilled Water System ◽  
And Control ◽  
Mixed Logical Dynamical

The chilled water system of central air conditioning is a typical hybrid system. The dynamic adjustment of cooling capacity based on hybrid system can achieve accurate temperature control and real-time energy saving. Mixed logical dynamical (MLD) systems have advantage for solving constrained optimization problems of this type of case by numerical methods. This paper proposes a novel modified type of MLD system, which enhances the model applicability and improves the switching flexibility and control effect for the framework. In order to meet the needs of cooling capacity and energy saving, the optimal control problem is transformed as MIQP problem by defined performance index. As a numeral example of application, the model and control method is used in pumps group control for variable water volume in chilled water system of central air conditioning. At last, the dynamic and energy-saving effects of the system are simulated, which shows the ideal control results.

EXERGOECONOMIC ANALYSIS OF A CHILLED WATER SYSTEM IN A SHOPPING MALL

2020 ◽  
Author(s):  
Renata Portela de Abreu ◽  
Victor Hugo Lobo Correia ◽  
Adriano Marques ◽  
monica carvalho
Keyword(s):  
Water System ◽  
Shopping Mall ◽  
Chilled Water ◽  
Chilled Water System ◽  
Exergoeconomic Analysis
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