scholarly journals Dynamic Modeling of Mechanical Draft Counter-Flow Wet Cooling Tower With Modelica

2010 ◽  
Author(s):  
Xiao Li ◽  
Yaoyu Li ◽  
John E. Seem
Keyword(s):  
Dynamic Modeling ◽  
Cooling Tower ◽  
Transient Behavior ◽  
Counter Flow ◽  
Inlet Conditions ◽  
The One ◽  
Control Volumes ◽  
Air Conditioning Systems ◽  
Volume Method ◽  
Energy Balances

Cooling towers are important equipments for the heating, ventilation and air conditioning systems in commercial buildings, rejecting the process heat generation to the atmosphere. Dynamic modeling of cooling tower is beneficial for control design and fault detection and diagnostics of the chilled-water systems. This paper proposes a simple and yet effective dynamic model for a typical mechanical draft counter-flow cooling tower. The finite volume method is applied to the one-dimensional heat and mass transfer analysis. With control volumes defined separately for the water and air sides, the dynamic equations are constructed with the mass and energy balances. The steady-state performance of the proposed model is evaluated with the experimental data from literature. The transient behavior is simulated under the changes of tower inlet conditions, with the performance to be evaluated in the future with field test data.

scholarly journals Experimental Study and Performance Analysis of Ceramic Packing Cooling Tower Using Taguchi Method

2014 ◽  
Vol 08 (1) ◽  
Keyword(s):  
Experimental Study ◽  
Taguchi Method ◽  
Orthogonal Array ◽  
Cooling Tower ◽  
Signal To Noise Ratio ◽  
Packing Material ◽  
Counter Flow ◽  
Ceramic Packing ◽  
Forced Draft ◽  
Inlet Conditions

Deterioration of the packing material is a major problem in cooling tower. In this experimental study, ceramic tile is used as packing material. The experimental study was conducted in a forced draft cooling tower. Cooling tower operating parameters were optimized using Taguchi approach. The application of Taguchi method is assessing maximum cooling tower effectiveness for the Forced draft counter flow cooling tower using ceramic packing. An experimental study has been carried out for Taguchi’s L9 orthogonal array. According to the Orthogonal array, the trail was performed under different inlet conditions of flow rate of water, air and Inlet water temperature. Signal-to-noise ratio (S/N) and regression were carried out in order to determine the effects of process parameters on cooling tower effectiveness. Finally, confirmation tests verified this reliability of Taguchi method for optimization of forced draft counter flow cooling tower performance with sufficient accuracy. Confirmation experiment was d o n e using optimum combination showed that cooling tower effectiveness was found by experiment is closer to the predicated value.

scholarly journals Optimization of cooling tower performance analysis using Taguchi method

2013 ◽  
Vol 17 (2) ◽  
pp. 457-470 ◽  
Author(s):  
Ramakrishnan Ramkumar ◽  
Arumugam Ragupathy
Keyword(s):  
Performance Analysis ◽  
Taguchi Method ◽  
Cooling Tower ◽  
Signal To Noise Ratio ◽  
Sufficient Accuracy ◽  
Wire Mesh ◽  
Signal To Noise ◽  
Counter Flow ◽  
Temperature Signal ◽  
Inlet Conditions

This study discuss the application of Taguchi method in assessing maximum cooling tower effectiveness for the counter flow cooling tower using expanded wire mesh packing. The experiments were planned based on Taguchi?s L27 orthogonal array .The trail was performed under different inlet conditions of flow rate of water, air and water temperature. Signal-to-noise ratio (S/N) analysis, analysis of variance (ANOVA) and regression were carried out in order to determine the effects of process parameters on cooling tower effectiveness and to identity optimal factor settings. Finally confirmation tests verified this reliability of Taguchi method for optimization of counter flow cooling tower performance with sufficient accuracy.

The Dynamic Modeling of PEMFC System for Automotive Application

2008 ◽  
Author(s):  
Sanggyu Kang ◽  
Kyoungdoug Min
Keyword(s):  
Energy Balance ◽  
Thermal Management ◽  
Dynamic Modeling ◽  
Management System ◽  
Mass Conservation ◽  
Cell System ◽  
Operating Conditions ◽  
Automotive Application ◽  
Thermal Management System ◽  
Control Volumes

Water and thermal management are crucial factors in determining the performance of PEMFC for automotive application. In order to investigate the effect of cell humidity and temperature on the performance of PEMFC, a dynamic model of a PEMFC system for automotive application has been developed by using Matlab/Simulink®. The model is composed of a PEM unit cell, membrane humidifier, and thermal management system (TMS). At first, fuel and air are well hydrated by the shell and tube humidifier, then humidified fuel and air flow into the PEMFC for electrochemical reaction. PEMFC temperature was maintained at a constant level by the thermal management system. The active area of PEM model is 240 cm2. The cell was discretized into several control volumes in the through-plane to resolve energy balance and species diffusion. The membrane humidifier model is also discretized into three control volumes in the through-plane to resolve the mass conservation and energy balance. Fuel and air are hydrated by the diffusion of the water through the membrane. The thermal management system consists of radiator, fan and pump. De-ionized water cools down the temperature of PEMFC. In order to validate the model, the model was compared with a corresponding experiment. Comparison shows that simulation results are in good agreement with experiments. And the dynamic response of PEMFC with regard to the change of current was also investigated. The model is useful to elucidate the relationships between operating conditions such as air relative humidity, temperature, etc. It is expected that this dynamic modeling of PEMFC system can contribute to the design optimization of PEM fuel cell system for vehicle application.

Thermohydrodynamic Behavior of a Slider Pocket Bearing

2005 ◽  
Vol 128 (2) ◽  
pp. 312-318 ◽  
Author(s):  
Mihai B. Dobrica ◽  
Michel Fillon
Keyword(s):  
Pressure Distribution ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Convective Boundary ◽  
Inertia Effects ◽  
Good Convergence ◽  
Bearing Design ◽  
The One ◽  
Volume Method ◽  
Generalized Reynolds Equation

Pocket-pads or steps are often used in journal bearing design, allowing improvement of the latter’s dynamic behavior. Similar “discontinuous” geometries are used in designing thrust bearing pads. A literature review shows that, to date, only isoviscous and adiabatic studies of such geometries have been performed. The present paper addresses this gap, proposing a complete thermohydrodynamic (THD) steady model, adapted to three-dimensional (3D) discontinuous geometries. The model is applied to the well-known geometry of a slider pocket bearing, operating with an incompressible viscous lubricant. A model based on the generalized Reynolds equation, with concentrated inertia effects, is used to determine the 2D pressure distribution. On this basis, a 3D field of velocities is constructed which, in turn, allows the resolution of the 3D energy equation. Using a variable-size grid improves the accuracy in the discontinuity region, allowing an evaluation of the magnitude of error induced by Reynolds assumptions. The equations are solved using the finite volume method. This ensures good convergence even when a significant reverse flow is present. Heat evacuation through the pad is taken into account by solving the Laplace equation with convective boundary conditions that are realistic. The runner’s temperature, assumed constant, is determined by imposing a zero value for the global heat flux balance. The constructed model gives the pressure distribution and velocity fields in the fluid, as well as the temperature distribution across the fluid and solid pad. Results show important transversal temperature gradients in the fluid, especially in the areas of minimal film thickness. This further justifies the use of a complete THD model such as the one employed.

Numerical prediction of the performance of gas-lubricated spiral groove thrust bearings

1997 ◽  
Vol 211 (2) ◽  
pp. 117-128 ◽  
Author(s):  
Y Yue ◽  
T. A. Stolarski
Keyword(s):  
Control Volume ◽  
Numerical Procedure ◽  
Operating Conditions ◽  
Hydrodynamic Bearings ◽  
Thrust Bearings ◽  
Flow Balance ◽  
Control Volumes ◽  
Volume Method ◽  
Spiral Angle ◽  
Spiral Grooves

The objective of this paper is to develop an accurate numerical procedure for the analysis of nominally flat contacts with spiral grooves lubricated by gases. The numerical procedure, which is based on the control-volume method, enables the solutions of the non-linear Reynolds equation to be obtained without limitation in geometry and operating conditions. Satisfactory flow balance was achieved on the control volumes as well as on the whole boundary and the method was proved to be very accurate. Convergence of the method was quick for any compressibility number. Three types of contact with spiral grooves were analysed. They were hydrodynamic bearings without interior chambers, hydrodynamic bearings with interior chambers and hybrid bearings. The effects of spiral angle, groove geometry (length, depth and width) and compressibility on performances were investigated for all possible designs.

Comparison of Supercritical CO2 Power Cycles to Steam Rankine Cycles in Coal-Fired Applications

2017 ◽  
Author(s):  
Jason D. Miller ◽  
David J. Buckmaster ◽  
Katherine Hart ◽  
Timothy J. Held ◽  
David Thimsen ◽  
...  
Keyword(s):  
Power Plants ◽  
Cooling Tower ◽  
Test Case ◽  
Test Cases ◽  
Power Cycles ◽  
Air Preheater ◽  
Power Cycle ◽  
Inlet Conditions ◽  
Cycle Efficiency ◽  
Steam Plant

Increasing the efficiency of coal-fired power plants is vital to reducing electricity costs and emissions. Power cycles employing supercritical carbon dioxide (sCO2) as the working fluid have the potential to increase power cycle efficiency by 3–5% points over state-of-the-art oxy-combustion steam-Rankine cycles operating under comparable conditions. To date, the majority of studies have focused on the integration and optimization of sCO2 power cycles in waste heat, solar, or nuclear applications. The goal of this study is to demonstrate the potential of sCO2 power cycles, and quantify the power cycle efficiency gains that can be achieved versus the state-of-the-art steam-Rankine cycles employed in oxy-fired coal power plants. Turbine inlet conditions were varied among the sCO2 test cases and compared with existing Department of Energy (DOE)/National Energy Technology6 Laboratory (NETL) steam base cases. Two separate sCO2 test cases were considered and the associated flow sheets developed. The turbine inlet conditions for this study were chosen to match conditions in a coal-fired ultra-supercritical steam plant (Tinlet = 593°C, Pinlet = 24.1 MPa) and an advanced ultra-supercritical steam plant (Tinlet = 730°C, Pinlet = 27.6 MPa). A plant size of 550 MWe, was selected to match available information on existing DOE/NETL bases cases. The effects of cycle architecture, combustion-air preheater temperature, and cooling source type were considered subject to comparable heat source and reference conditions taken from the steam Rankine reference cases. Combinations and variants of sCO2 power cycles — including cascade and recompression and variants with multiple reheat and compression steps — were considered with varying heat-rejection subsystems — air-cooled, direct cooling tower, and indirect-loop cooling tower. Where appropriate, combustion air preheater inlet temperature was also varied. Through use of a multivariate nonlinear optimization design process that considers both performance and economic impacts, curves of minimum cost versus efficiency were generated for each sCO2 test case and combination of architecture and operational choices. These curves indicate both peak theoretical efficiency and suggest practical limits based on incremental cost versus performance. For a given test case, results for individual architectural and operational options give insight to cost and performance improvements from step-changes in system complexity and design, allowing down selection of candidate architectures. Optimized designs for each test case were then selected based on practical efficiency limits within the remaining candidate architectures and compared to the relevant baseline steam plant. sCO2 cycle flowsheets are presented for each optimized design.

scholarly journals Analisa Kebutuhan Make Up Water Cooling Tower RSG-GAS pada Daya 30 MW Setelah Revitalisasi

2020 ◽  
Vol 17 (1) ◽  
pp. 38
Author(s):  
Pranto Busono ◽  
Santosa Pujiarta
Keyword(s):  
Cooling Tower ◽  
Water Cooling ◽  
Counter Flow ◽  
Evaporation Loss

Akibat kondisi dan usia dari cooling tower RSG-GAS maka telah dilakukan revitalisasi pada cooling tower tersebut. Cooling tower yang baru mempunyai tipe sama dengan tipe sebelumnya, yaitu tipe Mechanical induced draft, counter flow, Inline, Closed end. Akibat penggantian/revitalisasi cooling tower RSG-GAS maka perlu dilakukan kajian yang berkaitan dengan besarnya kehilangan air. Kehilangan air pada cooling tower terdiri atas: evaporation loss (We), Drift loss (Wd) dan blowdown (Wb). Besarnya kehilangan air berdasarkan desain 93,8074 m3/h, hasil perhitungan 53,1286 m3/h dan hasil pengamatan adalah sebesarnya 39,4548 m3/h. Kehilangan air pada cooling tower perlu dilakukan perhitungan karena berkaitan dengan kemampuan pompa PA-04 dalam mengkompensasi kehilangan air tersebut. Dengan kemampuan pompa PA-04 yang mempunyai kapasitas 100 m3/h, maka dapat dipastikan bahwa pompa PA-04 masih mampu untuk mengkompensasi kehilangan air di cooling tower.   Kata kunci : make up water, revitalisasi cooling tower, kehilangan air

Simulation Comparison of PEMFC Micro-Cogeneration Units With Conventional and Innovative Fuel Processing

2010 ◽  
Author(s):  
Leonardo Roses ◽  
Davide Bonalumi ◽  
Stefano Campanari ◽  
Paolo Iora ◽  
Giampaolo Manzolini
Keyword(s):  
Polymer Electrolyte Membrane ◽  
Performance Comparison ◽  
Fuel Processing ◽  
Electrolyte Membrane ◽  
Simulated Performance ◽  
Commercial Code ◽  
The One ◽  
Definition Of ◽  
Performance Results ◽  
Energy Balances

This paper deals with the performance comparison over simulated micro-cogeneration units based on polymer electrolyte membrane fuel cells (PEMFC or PEM), when the fuel is processed by means of two contrasting techniques. On the one hand with the use of conventional natural gas steam reforming (SR), and on the other, the adoption of an innovative palladium based membrane-reformer. After the definition of the plant layout, which reflects the results of previous studies and includes all the components of a 4 kW PEM for combined heat and power production, the comparison among the plant performances is carried out with two approaches: (i) using a in-house developed code (GS), able to calculate mass and energy balances, as well as a number of specific component parameters, already applied to a large variety of plant simulations, and (ii) using a commercial code (Aspen Plus®). The comparison allows to validate the simulated performance results as well as to evidence the advantages of the two approaches and to assess the effects of different simulation assumptions.

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