An Experimental and Analytical Study of a Unique Wet/Dry Surface for Cooling Towers

1978 ◽  
Vol 100 (3) ◽  
pp. 520-526 ◽  
Author(s):  
J. M. Bentley ◽  
T. K. Snyder ◽  
L. R. Glicksman ◽  
W. M. Rohsenow
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Analytical Study ◽  
Cooling Tower ◽  
Cross Flow ◽  
Hot Water ◽  
Cooling Towers ◽  
Experimental Apparatus ◽  
Power Plant Cooling ◽  
Cooling Air

An advanced wet/dry heat transfer surface has been developed for power plant cooling towers eliminating the need for conventional dry surface. Hot water to be cooled is channeled down grooves in the surface; the balance of the surface is dry and acts like a fin. The cooling air passes over the surface in cross-flow. Since the grooves occupy only a small fraction of the surface area, a majority of the heat transfer is by sensible heat transfer. In the experimental apparatus the wet surface area was five percent of the total area and the heat transfer by evaporation varied between 20 and 40 percent of the total heat transfer. An analytical model indicated that the yearly water consumption of a cooling tower with the new wet/dry surface would be less than half that of a conventional wet cooling tower and fog plumes would be eliminated.

scholarly journals Theoretical and experimental study of a cross-flow induced-draft cooling tower

2009 ◽  
Vol 13 (4) ◽  
pp. 91-98
Author(s):  
Elazm Abo ◽  
Farouk Elsafty
Keyword(s):  
Experimental Study ◽  
Cooling Tower ◽  
Characteristic Curve ◽  
Cross Flow ◽  
Hot Water ◽  
Proper Solution ◽  
Cooling Towers ◽  
Water Cooling ◽  
Transfer Coefficients ◽  
Experimental Rig

The main objective of this study is to find a proper solution for the cross-flow water cooling tower problem, also to find an empirical correlation's controlling heat and mass transfer coefficients as functions of inlet parameters to the tower. This is achieved by constructing an experimental rig and a computer program. The computer simulation solves the problem numerically. The apparatus used in this study comprises a cross-flow cooling tower. From the results obtained, the 'characteristic curve' of cross-flow cooling towers was constructed. This curve is very helpful for designers in order to find the actual value of the number of transfer units, if the values of inlet water temperature or inlet air wet bulb temperature are changed. Also an empirical correlation was conducted to obtain the required number of transfer units of the tower in hot water operation. Another correlation was found to obtain the effectiveness in the wet bulb operation.

Assessment of Cooling Tower Discharge Recirculation and Dispersion Using CFD Techniques

2015 ◽  
Author(s):  
S. Pal ◽  
L. J. Peltier ◽  
A. Rizhakov ◽  
M. P. Kinzel ◽  
M. H. Elbert ◽  
...  
Keyword(s):  
Experimental Data ◽  
Cooling Tower ◽  
Cross Flow ◽  
Bluff Bodies ◽  
Cooling Towers ◽  
Design Strategies ◽  
Worst Case ◽  
Buoyant Jets ◽  
Design Values ◽  
High Reynolds

The performance of cooling towers, whether operating by themselves, or in close vicinity of other cooling towers can be adversely affected by the re-ingestion of the cooling tower discharge into the tower intakes. The recirculation of the discharge from a wet cooling tower raises the wet bulb temperature of the air entering a wet cooling tower. Current design strategies, often account for this discharge re-ingestion issue, through a conservative adjustment to the far field ambient wet bulb temperature to calculate the actual intake wet bulb temperature. Critical applications, such as those related to nuclear safety applications where there is concern about cooling tower performance, may require more accurate and comprehensive assessment of the recirculation and dispersion of cooling tower discharge. Gaussian plume models alone are of limited use when dealing with discharges in the vicinity of large structures. This paper discusses the use of a computational fluid dynamics approach to evaluate worst case discharge recirculation effects in cooling towers. The bounding design values of tower intake wet bulb temperature increase due to recirculation (ingestion of tower’s own discharge), and interference (ingestion of another interfering tower’s discharge), are calculated considering the various conditions of cooling tower operation, ambient temperature, humidity and wind conditions. The RANS CFD model used in the study is evaluated against published experimental data for flow over bluff bodies at high Reynolds numbers, and experimental data on buoyant jets in cross flow.

Experimental Investigations on the Performance of a Cross Flow Air Heated Humidifier

2015 ◽  
Author(s):  
K. A. Khalid ◽  
A. S. Yassen ◽  
S. A. Salaudeen ◽  
M. A. Antar
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Surface Area ◽  
Cross Flow ◽  
Packing Material ◽  
Hot Water ◽  
Experimental Investigations ◽  
Heated Humidifier ◽  
Air Stream ◽  
Unit Effectiveness

A horizontal cross flow air heated humidifier is designed for three modes of heating. It is tested to investigate its performance in terms of its ability to effectively humidify air. The system investigated in this study has both the humidifier and the heater(s) integrated in one unit. Special low pressure-drop nozzles are used to spray water such that they provide a fine mist, thus they break a liquid to tiny droplets to increase the surface area for better heat and mass transfer between the hot air and sprayed water. Several attempts to improve system performance are made. For example, the effect of adding packing material to further increase heat and mass transfer surface area is attempted. Another attempt is by having an inter-stage heating such that a heating coil (basically a heat exchanger where hot water is circulated in a closed loop) is placed after a first-stage sprayer to heat the air again such that its ability to absorb more moisture increases as it is passed through a second-stage sprayer. A mist eliminator is placed at the exit of the humidifier to make sure water droplets are not allowed to leave the humidifier with the exit humid air stream. Performance parameters used in the analysis include the temperature and humidity of the exit air stream in addition to the humidifier effectiveness that is considered one of the crucial parameters in designing a HDH desalination system. A comparison between different modification to the humidifier are made to select the mode that results in the closest exit air stream to saturation condition and the highest humidifier effectiveness. Adding the packing material showed insignificant improvement to the humidifier performance. On the other hand, the inter-stage heating is believed to be effective in increasing the unit effectiveness.

scholarly journals A CASE STUDY ON MAINTENANCE OF OVERHEAT - SPOT WELDING MACHINE

2018 ◽  
Author(s):  
Dessy Agustina Sari
Keyword(s):  
Heat Transfer ◽  
Spot Welding ◽  
Cooling Tower ◽  
Cooling Water ◽  
Heat Transfer Process ◽  
Hot Water ◽  
Time Production ◽  
Standard Temperature ◽  
Standard Operation

Indicator overheat on robot transformer of spot welding was gun thermos alarm. Thermostat which adheringin the machine could be shut down the robot if this component detected the excessive warm below the standard operation. Impurities (scale, and deposit) existence caused heat transfer process disturbed, exchanged thermal between cold and hot water. This research methods were replacement part filler of the cooling tower and flushing the pipeline by chemical. The result showed a step progressing which cooling water reached the standard temperature, 30oC. Performance spot welding was being better so time production worked normally.

scholarly journals Design of Cross Flow Heat Exchanger Using Performance Charts

2018 ◽  
Vol 3 (2) ◽  
pp. 1
Author(s):  
Mohammed Al Arfaj ◽  
Nasser Al Mulhim ◽  
Abdullah Al Mulhim ◽  
Ahmed Al Naim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Surface Area ◽  
Material Flow ◽  
Cross Flow ◽  
Thermal Characteristics ◽  
Preliminary Design ◽  
Dimensionless Parameters ◽  
Flow Heat ◽  
The Right

The manuscript reviews the various steps involved in the design of a cross flow heat exchanger. Performance charts describing the thermal performance of the heat exchanger in terms of dimensionless parameters are used to develop the preliminary design of the heat exchanger. The preliminary design involves choosing the required number of heat exchanger passes, the required number of transfer units (NTU) and the capacity rate ratio for a given heat transfer application. These dimensionless parameters account for material, flow and thermal characteristics of the heat exchanger. In addition, NTU accounts for heat exchanger size, flow configuration and the type of heat exchanger. Since the preliminary design accounts for all the major characteristics of the heat exchanger, this approach is beneficial in optimizing the heat exchanger during the design phase. Performance charts indicate that indefinitely increasing the surface area (or NTU) does not increase the rate of heat transfer. There exists a threshold limit beyond which increasing the surface area adds no benefit to the heat exchanger. Instead, it just adds weight, material and cost of the heat exchanger. It must be noted that an undersized heat exchanger for a given application may not deliver the required heat transfer and while an oversized heat exchanger will increase the capital cost. Hence, it is very important to choose the right parameters during design of a heat exchanger. From the preliminary design, the detailed design for the heat exchanger can be readily extrapolated. The benefits of using performance charts in the design of a cross flow heat exchanger are described in the manuscript.

Combination of Impingement and Trip Strips for Combustor Liner Backside Cooling

Volume 3 ◽  
2004 ◽  
Author(s):  
Ryan Hebert ◽  
Srinath V. Ekkad ◽  
Vivek Khanna
Keyword(s):  
Heat Transfer ◽  
Cross Flow ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Combination Technique ◽  
Impingement Jet ◽  
Impingement Heat Transfer ◽  
Flow Effects ◽  
Heat Transfer Degradation ◽  
Cooling Air

Effective cooling of modern low NOx combustor liners is achieved through combinations of impingement and other heat transfer enhancement methods. In the present study, a combination of impingement and trip strips is studied to determine the optimum location of trip strips with respect to impingement jet arrays. Heat transfer with pure impingement has degradation downstream due to increased cross-flow effects. To counter the cross-flow induced heat transfer degradation, a combination technique wherein impingement is combined with ribs placed in between impingement rows or downstream of the impingement array is studied. Three configurations with increased rib placements and reduced impingement holes are studied and compared with pure impingement cases for the same jet Reynolds number. Three jet Reynolds numbers are studied for Rej = 10000, 20000, and 30000. Detailed heat transfer distributions are obtained using the transient liquid crystal technique. Results show that the presence of ribs increases jet impingement heat transfer on the surface with lower mass flows. The effectiveness of the combination ribs and impingement can provide higher heat transfer with reduced cooling air requirements.

scholarly journals Nonlinear Finite Element Analysis-Based Flow Distribution and Heat Transfer Model

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1664 ◽  
Author(s):  
Tomáš Létal ◽  
Vojtěch Turek ◽  
Dominika Babička Fialová ◽  
Zdeněk Jegla
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Fluid Flow ◽  
Heat Recovery ◽  
Tube Bundle ◽  
Cross Flow ◽  
Hot Water ◽  
Flow Tube ◽  
Element Analysis

A new strategy for fast, approximate analyses of fluid flow and heat transfer is presented. It is based on Finite Element Analysis (FEA) and is intended for large yet structurally fairly simple heat transfer equipment commonly used in process and power industries (e.g., cross-flow tube bundle heat exchangers), which can be described using sets of interconnected 1-D meshes. The underlying steady-state model couples an FEA-based (linear) predictor step with a nonlinear corrector step, which results in the ability to handle both laminar and turbulent flows. There are no limitations in terms of the allowed temperature range other than those potentially stemming from the usage of fluid physical property computer libraries. Since the fluid flow submodel has already been discussed in the referenced conference paper, the present article focuses on the prediction of the tube side and the shell side temperature fields. A simple cross-flow tube bundle heat exchanger from the literature and a heat recovery hot water boiler in an existing combined heat and power plant, for which stream data are available from its operator, are evaluated to assess the performance of the model. To gain further insight, the results obtained using the model for the heat recovery hot water boiler are also compared to the values yielded by an industry-standard heat transfer equipment design software package. Although the presented strategy is still a “work in progress” and requires thorough validation, the results obtained thus far suggest it may be a promising research direction.

Modeling of a Rotary Dry Cooling Tower

1981 ◽  
Vol 103 (4) ◽  
pp. 715-719 ◽  
Author(s):  
J. A. Valenzuela ◽  
L. R. Glicksman
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Cooling Tower ◽  
Thick Layer ◽  
Hot Water ◽  
Rotating Disks ◽  
Air Stream ◽  
Additional Resistance ◽  
Dry Cooling Tower ◽  
Dry Cooling

A novel design of a rotary heat exchanger to be used as a dry cooling tower is described. The heat exchanger consists of a matrix of thin steel disks which rotate between a hot water bath and a forced draft air stream. On top of the water floats a 2 cm thick layer of oil which coats the rotating disks and thus eliminates evaporation. An analytical model of the heat exchanger was developed and validated with experimental measurements taken on a 1.5 m dia test section. The model was then used to determine the net effect of the oil on the heat transfer performance. Although the oil film that coats the disks presents an additional resistance to the transfer of heat, it also contributes to the heat capacity of the disks. It was found that the reduction in the overall heat transfer rate due to the presence of the oil is small, of the order of 5 to 10 percent.

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