Cooling Tower Performance Evaluation: Merkel, Poppe, and e-NTU Methods of Analysis

2005 ◽  
Vol 127 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Johannes C. Kloppers ◽  
Detlev G. Kro¨ger
Keyword(s):  
Performance Evaluation ◽  
Analytical Approach ◽  
Cooling Tower ◽  
Performance Characteristics ◽  
Cooling Towers ◽  
Ambient Conditions ◽  
Natural Draft ◽  
Ambient Humidity ◽  
Fill Material ◽  
Methods Of Analysis

The heat rejected and water evaporated in mechanical and natural draft cooling towers are critically evaluated by employing the Merkel, Poppe, and e–number-of-transfer-units e-NTU methods of analysis, respectively, at different operating and ambient conditions. The importance of using a particular method of analysis when evaluating the performance characteristics of a certain fill material and subsequently employing the same analytical approach to predict cooling tower performance is stressed. The effect of ambient humidity and temperature on the performance of cooling towers employing the Merkel, e-NTU, and Poppe methods of analysis are evaluated.

PERFORMANCE EVALUATION OF COUNTER-FLOW WET COOLING TOWERS USING EXERGETIC ANALYSIS

2008 ◽  
Vol 32 (3-4) ◽  
pp. 499-512 ◽  
Author(s):  
A. Ataei ◽  
M. H. Panjeshahi ◽  
M. Gharaie
Keyword(s):  
Experimental Data ◽  
Performance Evaluation ◽  
Performance Improvement ◽  
Thermal Efficiency ◽  
Cooling Tower ◽  
Cooling Towers ◽  
Ambient Conditions ◽  
Counter Flow ◽  
Packing Materials ◽  
Exergetic Analysis

In this paper, performance evaluation of wet cooling tower is done. To achieve this aim, first, thermal behavior of counter-flow wet cooling tower is studied through a simulation model. The influence of the environmental conditions on the thermal efficiency of the cooling tower is investigated. The cooling tower performance is simulated in terms of varying air and water temperatures, and of the ambient conditions. This model allows the use of a variety of packing materials. Second, the exergetic analysis is applied to study the cooling tower potential of performance improvement. The model is validated against the experimental data.

Computational Fluid Dynamics Analysis of Cooling Tower Inlets

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
H. C. R. Reuter ◽  
D. G. Kröger
Keyword(s):  
Cooling Tower ◽  
Flow Patterns ◽  
Full Scale ◽  
Loss Coefficient ◽  
Cooling Towers ◽  
Cfd Model ◽  
Shell Wall ◽  
Natural Draft ◽  
Flow Losses ◽  
Loss Coefficients

Cooling tower inlet losses are the flow losses or viscous dissipation of mechanical energy affected directly by the cooling tower inlet design, which according to the counterflow natural draft wet-cooling tower performance analysis example given in Kröger (Kröger, 2004, Air-Cooled Heat Exchangers and Cooling Towers: Thermal-Flow Performance Evaluation, Pennwell Corp., Tulsa, OK), can be more than 20% of the total cooling tower flow losses. Flow separation at the lower edge of the shell results in a vena contracta with a distorted inlet velocity distribution that causes a reduction in effective fill or heat exchanger flow area. In this paper, a two-dimensional (axi-symmetric) computational fluid dynamic (CFD) model is developed using the commercial CFD code ANSYS FLUENT, to simulate the flow patterns, loss coefficients and effective flow diameter of circular natural draft cooling tower inlets under windless conditions. The CFD results are compared with axial velocity profile data, tower inlet loss coefficients and effective diameters determined experimentally by Terblanche (Terblanche, 1993, “Inlaatverliese by Koeltorings,” M. Sc. Eng. thesis, Stellenbosch University, Stellenbosch, South Africa) on a cylindrical scale sector model as well as applicable empirical relations found in Kröger, determined using the same experimental apparatus as Terblanche. The validated CFD model is used to investigate the effects of Reynolds number, shell-wall thickness, shell wall inclination angle, fill loss coefficient, fill type, inlet diameter to inlet height ratio and inlet geometry on the flow patterns, inlet loss coefficient and effective diameter of full-scale cooling towers. Ultimately, simple correlations are proposed for determining the cooling tower inlet loss coefficient and inlet effective flow diameter ratio of full-scale cooling towers excluding the effect of rain zones and the structural supports around the cooling tower entrance.

Estimating Cooling Towers for Power Plant Applications

2006 ◽  
Author(s):  
Hector L. Cruz
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cooling Tower ◽  
Arithmetic Function ◽  
Water Flow Rate ◽  
Mechanical Equipment ◽  
Cooling Towers ◽  
Ambient Conditions ◽  
The Cost ◽  
Basin Area

It has always been difficult to estimate size and cost of well designed counterflow induced-draught cooling towers due to the interrelationship of approach temperature and cooling range associated with each design. Attempts to estimate the cost of a tower by assessing currency per cell, per square foot, per gallon, or currency per other single metric, have never been sufficiently accurate due to the asymptotic nature of the approach temperature versus the tower size arithmetic function. To determine accurate qualitative metrics for cooling tower estimating purposes requires assessing two-variable second-order equations in water-flow-rate/approach-temperature, temperature-range/approach-temperature, wet-bulb-temperature/approach-temperature, and approach-temperature/cost. The design and therefore cost responds to the following variables; 1) Recirculating Water Flow Rate, 2) Inlet Wet Bulb Temperature (WBT), 3) Approach Temperature, and 4) Cooling Tower Range or Heat Duty. With the proper evaluation of these parameters they can be utilized to determine metrics to estimate the following parameters: 1) Number of Cells, 2) Basin Area, 3) Pump Power, 4) Fan Power, and 5) Costs (at today’s prices only). In addition, a percentage breakdown can be calculated for; 1) Structure, 2) Hardware, 3) Mechanical Equipment, 4) Labor, and 5) Miscellaneous items. Although developed for the power industry, the operative model, design, and qualified costing techniques are also valid for large petroleum and chemical process projects, provided the heat duty dissipated, ambient conditions, water quality and flow rate can be accurately predicted. A set of equations are developed which can be used to estimate the significant costs of a proposed cooling tower. Example calculations and data are presented in Annex A.

Study of Heat Rejection in Triple Natural Draft Dry Cooling Towers under Crosswind Using Radiator-Type Windbreakers

2014 ◽  
Vol 598 ◽  
pp. 265-270 ◽  
Author(s):  
Amir Hozhabr ◽  
Ramin Radi ◽  
Hossein Chenari ◽  
Arash Chogani ◽  
Masoud Esmaeelipour
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cooling Tower ◽  
Independent Solution ◽  
Numerical Results ◽  
Cooling Towers ◽  
Cooling Efficiency ◽  
Natural Draft ◽  
Computational Fluid Dynamics Cfd ◽  
Dry Cooling

In this paper, the effect of crosswind on triple natural draft dry cooling towers is studied and analyzed. Concerning this area, many researches have concentrated on one cooling tower. This research focuses on the mutual effects of the adjacent towers' performance, and also makes a comparison between the efficiency of the three cooling towers in windy and no-wind conditions, using Computational Fluid Dynamics (CFD). In modeling the crosswind condition, at first solid windbreakers, and then radiator-type windbreakers are used for each cooling tower. Finally, the water outlet temperatures of the radiators' cooling towers are analyzed, and the total heat rejections at different conditions are compared. Numerical results show that radiator-type windbreakers can substantially improve cooling efficiency more than usual solid-types. It should be mentioned that a complete grid study is done to achieve a grid-independent solution.

A New Two-Dimensional CFD Model to Predict the Performance of Natural Draught Wet-Cooling Towers Packed With Trickle or Splash Fills

2010 ◽  
Author(s):  
Hanno C. R. Reuter ◽  
Detlev G. Kro¨ger
Keyword(s):  
Cooling Tower ◽  
Air Flow ◽  
Linear Interpolation ◽  
Atmospheric Temperature ◽  
Performance Characteristics ◽  
Cooling Towers ◽  
Cfd Model ◽  
Flow Angle ◽  
Cfd Models ◽  
Air Inlet

In the design of a modern natural draught wet-cooling tower, structural and performance characteristics must be considered. Air flow distortions and resistances must be minimised to achieve optimal cooling which requires that the cooling towers must be modelled two-dimensionally and ultimately three-dimensionally to be optimized. It is found that CFD models in literature are limited to counterflow cooling towers packed with film fills which are porous in one direction only and generally have a high pressure drop, as well as purely crossflow cooling towers packed with splash fill, which simplifies the analysis considerably. Many counterflow cooling towers are however packed with trickle and splash fills which have anisotropic flow resistances, which means the fills are porous in all flow directions and thus air flow can be oblique through the fill, particularly near the cooling tower air inlet. This provides a challenge since available fill test facilities and subsequently fill performance characteristics are limited to purely counter- and crossflow configuration. This paper presents a CFD model to predict the performance of natural draught wet-cooling tower with any type of fill configuration, which can be used to investigate the effects of different atmospheric temperature distributions, air inlet and outlet geometries, air inlet heights, variations in radial water loading and fill depth, fill configurations, rain zone drop size distributions, and spray zone performance characteristics on cooling tower performance for optimization purposes. Furthermore the effects of damage or removal of fill in annular sections and boiler flue gas discharge in the centre of the tower can be investigated. The fill performance characteristics for oblique air flow are determined by linear interpolation between counter- and crossflow fill characteristics in terms of the air flow angle. The CFD results are validated by means of corresponding one-dimensional computational model data.

scholarly journals Coupling model and solving approach for performance evaluation of natural draft counter-flow wet cooling towers

2016 ◽  
Vol 20 (1) ◽  
pp. 291-301 ◽  
Author(s):  
Wei Wang ◽  
Deliang Zeng ◽  
Yong Hu ◽  
Jizhen Liu ◽  
Yuguang Niu
Keyword(s):  
Performance Evaluation ◽  
Water Temperature ◽  
Water Flow ◽  
Cooling Water ◽  
Coupling Model ◽  
Outlet Temperature ◽  
Cooling Towers ◽  
Air Velocity ◽  
Natural Draft ◽  
Plant Practice

When searching for the optimum condenser cooling water flow in a thermal power plant with natural draft cooling towers, it is essential to evaluate the outlet water temperature of cooling towers when the cooling water flow and inlet water temperature change. However, the air outlet temperature and tower draft or inlet air velocity are strongly coupled for natural draft cooling towers. Traditional methods, such as trial and error method, graphic method and iterative methods are not simple and efficient enough to be used for plant practice. In this paper, we combine Merkel equation with draft equation, and develop the coupled description for performance evaluation of natural draft cooling towers. This model contains two inputs: the cooling water flow, the inlet cooling water temperature and two outputs: the outlet water temperature, the inlet air velocity, equivalent to tower draft. In this model, we furthermore put forward a soft-sensing algorithm to calculate the total drag coefficient instead of empirical correlations. Finally, we design an iterative approach to solve this coupling model, and illustrate three cases to prove that the coupling model and solving approach proposed in our paper are effective for cooling tower performance evaluation.

scholarly journals Influence of ambient conditions and water flow on the performance of pre-cooled natural draft dry cooling towers

2014 ◽  
Vol 66 (1-2) ◽  
pp. 621-631 ◽  
Author(s):  
Suoying He ◽  
Zhiqiang Guan ◽  
Hal Gurgenci ◽  
Ingo Jahn ◽  
Yuanshen Lu ◽  
...  
Keyword(s):  
Water Flow ◽  
Cooling Towers ◽  
Ambient Conditions ◽  
Natural Draft ◽  
Dry Cooling

Construction Simulation and Construction Speed Analysis of Natural Draft Cooling Towers

2013 ◽  
Vol 353-356 ◽  
pp. 3559-3565
Author(s):  
Ming Zhang ◽  
Heng Le Wang
Keyword(s):  
Nuclear Power ◽  
Cooling Tower ◽  
Guangdong Province ◽  
Load Reduction ◽  
Simulation Methods ◽  
Cooling Towers ◽  
Construction Simulation ◽  
Stress Distributions ◽  
Power Station ◽  
Natural Draft

Using the finite element code ABAQUS and taking account of the wind load reduction, this paper presents a set of construction simulation methods of concrete cooling towers. A natural draft cooling tower at Taishan nuclear power station in Guangdong province, China, under three speeds of construction is simulated. Displacement and stress distributions of the cooling tower in the different construction stages are obtained. Some interested parts of the cooling tower are analyzed in detail and the variations of displacements and stresses of these parts with the construction are concluded. A comparative study of the influence of construction speed on displacements and stresses is performed as well. The analyses and proposals of this paper may be used as reference to the cooling tower design and construction.

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