Cooling Tower Fan Research Articles

Energy analysis of chilled water system configurations using simulation-based optimization

The paper presents an incremental development of the methodology for chilled water system design optimization. Initially, the system configuration parameters are varied with fixed design conditions to confirm the established best practice design criteria, followed by a comprehensive system design optimization. The implemented simulation-based optimization approach couples the Dymola/Modelica dynamic modeling and simulation program with GenOpt generic optimization program to find optimal system configuration. A dynamic system model is developed to vary and simulate different chilled water system configurations. Optimization of the chilled water system is achieved at both design and configuration level using five design variables. Two discrete variables are related to system configuration: number of chillers and number of cooling towers and three continuous variables are related to system design: building load demand, temperature difference across condenser, and cooling tower fan speed. The strategy of varying system design and configuration variables together for overall system optimization proved to be the most energy efficient. For a fixed building load demand, power consumption of the considered system can be reduced 17–43% by selecting an optimal system configuration.

Research on the Energy Consumption Reference Value of Commercial Office Buildings in Xi’an

Energy consumption reference values support the reference data for development of building energy efficiency potential. A uniform split model of energy consumption was established for calculating the item electricity consumption. Item electricity consumption are consisted by the electricity use of air conditioning system (chillers, chilled water pumps, cooling water pumps, cooling tower fans and end-use equipments), lighting system, indoor equipments and service equipments respectively. The data from site investigation was used to calculate the item electric energy use intensities (EUIs) in commercial office building. And these EUIs were used to identify the item energy reference value by two statistical analysis methods. The results show that the quadratic average EUIs which stand for the high level of energy consumption are lower than the mean plus standard deviation (SD) EUIs. Finally, the individual building (EUIs) can be compared with these reference values to evaluate building energy performance. And the item energy reference value is investigated in support of the retrofit of commercial office building.

Synthesis of cooling water systems with multiple cooling towers

This paper presents a systematic approach for the synthesis of re-circulating cooling water systems consisting of a cooler network and a cooling tower network (i.e. a general arrangement of multiple interconnected cooling towers with different supply temperatures). An overall superstructure is developed, which contains all the different alternatives for the cooler and cooling tower networks, as well as all their potential interconnections for fixed data of hot process streams. The synthesis problem is formulated as a mixed integer nonlinear programming problem. The continuous variables include the flow rates and temperatures of the circulating cooling water in the superstructure while the integer variables describe the existence of the coolers and the cooling towers. The objective function is to minimize the total annual cost, which includes the investment costs of cooler units and cooling towers, as well as the operating costs due to make-up water and power consumption of the circulating-water pumps and cooling tower fans. The solution of the proposed MINLP formulation provides simultaneously both the optimal configuration and operating conditions of the cooler and cooling tower network to comply with given process cooling demand at minimum total annual cost. One of the most important design variables is the number of cooling water sources (i.e. cooling water streams at different temperatures originated from the outlets of cooling towers) for removing heat from several hot process streams at different temperature ranges. Results show that cooling systems consisting of multiple cooling towers with different supply temperature yield significant better results than traditional systems with a cooler network in parallel arrangement that is supplied with cooling water from a single cooling tower.

Chillers energy consumption, energy savings and emission analysis in an institutional buildings

Chillers consume more than 40% of the total energy used in the commercial and industrial buildings for space conditioning. In this paper, energy consumption by chillers and chilled water pumps, condenser pumps and fan motors has been estimated using data collected by a walkthrough energy audit for the 16 faculties of the University of Malaya. It has been estimated that chillers and motors and pumps used in chillers consume 10,737 MWh (i.e. 51% of total energy consumption) of electric energy for different percentage of loadings. As chillers are major energy users, variable speed drives are applied in chillers to reduce their energy consumption. It has been estimated that about 8368 MWh annual energy can be saved by using efficient chillers at different loadings. It has also been found that about 23,532 MWh annual energy can be saved for chilled water supply pumps, condenser pumps and cooling tower fan motors by matching required speeds using variable speed drives for 60% of speed reduction. About 1,274,692 kg of CO 2 emission could be avoided for using energy efficient chillers at 50% load. It has been also found that about 2,426,769 kg CO 2 emission can be reduced by using variable speed drives for 60% speed reductions. Payback periods found to be only few months for using variable speed drives in chilled water pumps, condensers and fan motors.

Research on the Monitoring Technique of Non-Contact Running Status of Cooling Tower Fan Blades

This paper presents a new monitoring method of non-contact blade status—blade tip timing monitoring method based on the principle of discontinuous phase principle, and a new monitoring system of non-contact running status of cooling tower fan blades is developed on the basis of the technology of single-chip microcomputer(SCM) and the blade tip timing monitoring method.The monitoring system is controlled by the SCM and has real-time monitoring to the blade. The pulse signal which is collected by the sensor is processed by the SCM.Through using the timing and interrupt function of SCM, the pulse signal is analysed and processed, when the blade breaks down and deforms, the system will shut down the fan and output a forecast alarm, so the blade accident will be prevented. It is proved that the monitoring method can greatly improve the reliability of the fan running status and the fault diagnosis and effectively prevent the default of the blades, so the monitoring system has a wide application value.

Research of Fault Warning System of the Cooling Tower Fan Blade

A new monitoring method is described on the basis of the technology of the cooling tower fan monitoring and failure diagnosis, the warning system uses microprogrammed control unit real-time monitoring the blade. A magnet was fixed on the tip of every blade and these magnets were uniformly distributed in the same plane. A Hall proximity switch was fixed on the air duct which was at the same plane with the magenet, and the Hall proximity switch was used as a signal acquisition sensor, and the pulse signal of the Hall proximity swith was collected through microprogrammed control unit. Using the timing and interrupt function of microprogrammed control unit, the pulse signal was analysed and processed, when the blade breaks down and deforms, the preprogramme shut down the fan and outputted a forecast alarm, so the blade accident would be prevented. It is proved that running state of the system is good by production and practice and the monitoring method can greatly improve the reliability of the fault monitoring and warning. The monitoring system has a wide application.

Economic benefits of optimal control for water-cooled chiller systems serving hotels in a subtropical climate

A water-cooled chiller system in an air-conditioned hotel can take up about one-quarter of the total electricity consumption and considerable amounts of water in the heat rejection process. This paper evaluates operating cost savings of a chiller system integrated with optimal control of cooling towers and condenser water pumps. A sophisticated chiller system model was used to ascertain how different control methods influence the annual electricity and water consumption of chillers operating for the cooling load profile of a reference hotel. It is estimated that applying load-based speed control to the cooling tower fans and condenser water pumps could reduce the annual system electricity use by 8.6% and operating cost by 9.9% relative to the equivalent system using constant speed fans and pumps with a fixed set point of 29.4 °C for cooling water temperature control. The ways to implement this advanced control for system optimization are discussed.

Comprehensive Environmental Assessment for Cooling Towers with Various Controls

Cooling towers are generally used in water-cooled chiller systems, which provide cooling energy for commercial buildings. This article assesses how the various control systems of cooling towers influence plume emissions and the electricity and water consumption of a chilled water system. Integrated with real control of cooling tower fans, chiller and cooling tower models were developed to analyze how the energy performance of a chiller and the water loss rate varied under different operating conditions. The status of air flows through the cooling tower was investigated to judge plume formation under various cooling tower controls. A simulation analysis on a chilled water system serving an office building showed that optimizing the fan speed control of cooling towers enables the annual electricity and water consumption costs to save 4.6% while also reducing the plume generation. The optimum control means adjusting the temperature of cooling water leaving the cooling tower in response to the chiller load and wet bulb outdoor temperature. The results of this article provide important insights into how to enhance the environmental performance of cooling towers for use in water-cooled chiller systems.

Effects of alternative control strategies of water-evaporative cooling systems on energy efficiency and plume control: A case study

This paper reports the evaluations of energy efficiency, plume potential as well as plume control of a huge chiller plant using water-evaporative cooling towers for heat rejection for a super high-rising commercial office building in a subtropical region of Hong Kong. The evaluations were carried out in a dynamic Transient Simulation Program (TRNSYS)-based simulation platform using alternative control strategies including set-point control logics of the supply cooling water temperature and cooling tower fan modulation control methods as well as different number control means of cooling towers. The results show that different control strategies have significant effects on the energy efficiency of the chiller plant. The quantification of the energy efficiency demonstrates significant energy-saving potential by using advanced technologies for implementing optimal control strategies in this cooling system. The results also reveal that the plume may occur frequently in spring and summer seasons and occasionally in other months due to the odd subtropical weather conditions. Control strategies also have significant effects on the frequency of the plume occurrence. The effective energy efficiency control and effective plume control using wet–dry (i.e., hybrid) cooling towers are also discussed.

B-61 杭基礎を利用した自然エネルギーによる土壌蓄熱空調システムの性能分析 : (その3)冷却塔ファンのインバータ化に伴う運転の最適化

B-61 杭基礎を利用した自然エネルギーによる土壌蓄熱空調システムの性能分析 : (その3)冷却塔ファンのインバータ化に伴う運転の最適化

A General Control Algorithm for Cooling Towers in Cooling Plants with Electric and/or Gas-Driven Chillers

A hybrid chiller plant employs a combination of chillers that are “powered” by electricity and natural gas. This paper presents an algorithm for determining cooling tower fan settings in hybrid plants in response to loadings on individual chillers. Parameters of the algorithm are evaluated using design information for the chillers and cooling tower fans. In addition to reducing operating costs, use of the open-loop control strategy simplifies the control and improves the stability of the tower control compared with the use of a constant condenser water supply or approach to wet-bulb. Simulated plant cooling costs associated with the algorithm were compared with costs for optimized settings and were within 1% of the minimum costs. The control method is general, in the sense that it also applies to cooling plants that have all electric or all natural gas chillers.

Power Saving of Large-Scaled Helium Compressor for Fusion Device

For the purpose of reducing the power consumption of a cryogenic system for an experimental nuclear fusion system, investigation of the relationship between the ambient temperature and the mass flow rate of the compressor was carried out. When the suction gas temperature is lowered, gas density increases. The mass flow rate of the compressor can therefore be increased without any change in power consumption. It has been confirmed that some 5.6% of compressor power consumption can be saved by making the cooling water temperature equal to the ambient temperature during the winter season with the continuous running of the cooling tower fan motor. Further, a new gas compression cycle using an additional auxiliary gas cooling system was developed to lower the compressor suction gas temperature. Compared to a conventional system, some 11% of power consumption can be saved using this new gas compression cycle when the helium gas suction temperature of the compressor is 235K.

Cooling Tower Fan Control for Energy Efficiency

ABSTRACT This article evaluates the economics of alternative cooling tower capacity control methods. Annual fan electrical energy requirements are calculated for towers with single-speed, two-speed, and variable-speed fans. Fan energy requirements are determined counter-flow and cross-flow towers designed for low initial cost and for energy efficiency. Effectiveness-NTU equations are solved to predict cooling tower performance with the fan running at various speeds. Natural convection, which determines the cooling capacity when the fan is off, is accounted for using a mean enthalpy difference. Ambient conditions are simulated using typical meteorological year data for five locations. The results show that potential savings are not strongly dependent on the approach temperature, but are dependent on the range in colder climates. The potential for saving is greatest for cooling towers designed for low initial cost, and is generally higher in locations where the wet bulb temperature remains relatively consta...

Cooling Tower Fan Control for Energy Efficiency

ABSTRACT This article evaluates the economics of alternative cooling tower capacity control methods. Annual fan electrical energy requirements are calculated for towers with single-speed, two-speed, and variable-speed fans. Fan energy requirements are determined counter-flow and cross-flow towers designed for low initial cost and for energy efficiency. Effectiveness-NTU equations are solved to predict cooling tower performance with the fan running at various speeds. Natural convection, which determines the cooling capacity when the fan is off, is accounted for using a mean enthalpy difference. Ambient conditions are simulated using typical meteorological year data for five locations. The results show that potential savings are not strongly dependent on the approach temperature, but are dependent on the range in colder climates. The potential for saving is greatest for cooling towers designed for low initial cost, and is generally higher in locations where the wet bulb temperature remains relatively consta...

Optimal control development for chilled water plants using a quadratic representation

Optimal supervisory control strategy for the set points of controlled variables in the cooling plants has been studied by computer simulation. A quadratic linear regression equation for predicting the total cooling system power in terms of the controlled and uncontrolled variables was developed using simulated data collected under different values of controlled and uncontrolled variables. The optimal set temperatures such as supply air temperature, chilled water temperature, and condenser water temperature, are determined such that energy consumption is minimized as uncontrolled variables, load, ambient wet bulb temperature, and sensible heat ratio are changed. The chilled water loop pump and cooling tower fan speeds are controlled by the PID controller such that the supply air and condenser water set temperatures reach the set points designated by the optimal supervisory controller. The influences of the controlled variables on the total system and component power consumption were determined. The predicted power obtained from the quadratic regression equation was found to be a good fit to the simulated one. Because the Hermitian matrix of the system quadratic cost function was positive, the optimal control variables for the minimum power consumption were able to be obtained. There are relatively high effects of the load and sensible heat ratio on the optimal supply air and chilled water set temperatures, while the effect of ambient wet bulb temperature is less. In contrast to that result, the ambient wet bulb temperature has a much larger effect on the optimal condenser water set temperature, while the load has less, and the sensible heat ratio has no influence on it. The trade-off among the components of power consumption results in that the total system power use in both simulated and predicted systems are minimized at lower supply, higher chilled water, and lower condenser water set temperature conditions.

Effect of Drift Eliminator Design on Cooling Tower Performance

In the use of wet cooling towers, drift refers to small droplets of circulating water that are carried out of the cooling tower by the saturated exhaust air. Inertial impaction separators, known as drift eliminators, are used to strip the water droplets from the exhaust air. To achieve peak cooling tower operating efficiency, it is desirable that losses in fan system performance due to the drift eliminators be minimized. Therefore, an experimental program was developed and executed to evaluate the effect of drift eliminator design on cooling tower fan system performance. Flow visualization studies were used to gain insight into the flow patterns within the cooling tower plenum as influenced by drift eliminator design. A fully instrumented fan test cell was used to investigate the effects upon fan system performance resulting from two different styles of drift eliminators. The effect of drift eliminator discharge angle upon fan system total efficiency was investigated and the optimal discharge angle determined.

Model scale testing of outdoor noise propagation from a power plant

A proposed cogenerating power plant of 70-MW capacity is to be located in an urban setting and will be subject to stringent environmental noise emission criteria. A four-cell forced draft cooling tower is included in the plant design. Computer modeling of cooling tower noise propagation to affected neighboring residences involved significant uncertainties due to the complex shapes of power plant building elements and existing surrounding buildings. Without a finished facility in which to perform full-scale field tests, the next best thing is a scale model test. This paper will discuss the specifics of the 1/20th scale test setup, materials, selection, instrumentation, test execution, some problems and some lessons learned. The results of the test will be given in terms of the differences in octave band sound-pressure levels between an unobstructed free-field value and the modeled in situ value, at several receptor positions. The test enabled the specification of more precise sound attenuating elements for the cooling tower fans and inlets in order to comply with the governing regulations.

Engineering and design features of the Otake geothermal power plant

Otake geothermal power plant, the first steam-water mixture type geothermal power plant in Japan, was accomplished in August, 1967, and is now operating successfully with 12,000 kW output. In comparison with the other geothermal power plants in the world, most of which use superheated steam at about 3–13 kg/cm 2 G, the features of Otake geothermal power plant are that it utilizes low-pressure saturated steam of 1.5 kg/cm 2 G separated from a mixture of hot water and steam. The design of this plant is based on the study and development of the following items: 1. (1) The study of the characteristics of the geothermal well. 2. (2) The study of the chemical properties of steam and hot water. 3. (3) The study of ideal material to be used for geothermal steam and water. 4. (4) The development of efficient water separators. 5. (5) The development of orifice water-level control method. 6. (6) The study of transmission of mixture of water and steam. 7. (7) The development of jet condensers. The features of this power plant are as follows: Rated output 10,000 kW Maximum output 13,000 kW Steam condition 1.5 kg/cm 2 saturated Condenser vaccum 687 mmHg Geothermal well 5 × 8 in.dia. Steam turbine Single cylinder impulse condensing Condenser Barometric spray type Cooling method Forced draft cooling tower Gas extractor Reciprocating type vacuum pump The steam condition was selected to get the maximum available energy from the geothermal well, and also to avoid power down in case of scale deposits. The condenser vacuum was selected considering all the factors, such as turbine output, turbine last blade length, size of both the condenser and cooling tower, and required number and power for cooling water pump, hot water pump, cooling tower fan and vacuum pump. In the case of geothermal power plants steam quantity is apt to increase in the future. Therefore, in order to be sure of stretched power operation in the future, turbines are designed to have a maximum output of 13,000 kW. The main problems of the geothermal plant which uses a mixture of hot water and steam are scale deposit and corrosion. This paper describes the design concept of the equipment which can withstand and work effectively against problems inherent to steam-water mixture type geothermal power plants. Overall inspection after 8670 hours of continuous operation showed no damaged to all the equipment.

Probleme der schwingungsisolierten aufstellung von maschinen

Vibration isolation of machines by elastic mounting The paper explains basically the theory of elastic mounting of machinery and gives some practical aspects and recommendations for the vibration isolation of air conditioning equipment. Vibration transmission attenuation for a condensing pump, chilled water pump, chilling set and cooling tower fan, are mentioned.