Modeling Large-Size Boilers As a Set of Heat Exchangers: Tips and Tricks

2001 ◽  
Author(s):  
Cristóbal Cortés ◽  
Luis I. Díez ◽  
Antonio Campo
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Practical Calculation ◽  
Approximate Methods ◽  
Monitoring Method ◽  
Large Size ◽  
Thermoelectric Plant ◽  
The One

Abstract Practical calculation of the heat-recovery sections of large-size boilers is still based on approximate methods. On the one hand, CFD-based models cannot directly handle the geometric intricacy of tube bundles, and thus rely on volume-averaged source terms that demand empirical input. On the other hand, the standard, lumped heat exchanger calculation, which can be a far simpler and more robust alternative, fails in several important aspects, mainly related to the effects of thermal radiation and the coupling between several sections. In this paper, we consider the diverse sections of a coal-fired utility boiler as a case study to show how to deal with these shortcomings. Under the objective of developing a simple monitoring method, we extend the traditional heat exchanger model to take into account most of the peculiarities of boiler superheaters, reheaters and economizers. Techniques range from the re-examination of analytical solutions to the auxiliary use of CFD calculations. The models are assembled to simulate the thermal performance of the boiler as a whole unit. Results are validated against actual measurements taken at a thermoelectric plant.

scholarly journals Heat pipe heat exchanger and its potential to energy recovery in the tropics

2015 ◽  
Vol 19 (5) ◽  
pp. 1685-1697 ◽  
Author(s):  
Yat Yau ◽  
Mohammad Ahmadzadehtalatapeh
Keyword(s):  
Heat Exchanger ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Energy Recovery ◽  
Heat Recovery ◽  
Face Velocity ◽  
The One ◽  
The Tropics ◽  
Pipe Heat

The heat recovery by the heat pipe heat exchangers was studied in the tropics. Heat pipe heat exchangers with two, four, six, and eight numbers of rows were examined for this purpose. The coil face velocity was set at 2 m/s and the temperature of return air was kept at 24?C in this study. The performance of the heat pipe heat exchangers was recorded during the one week of operation (168 hours) to examine the performance data. Then, the collected data from the one week of operation were used to estimate the amount of energy recovered by the heat pipe heat exchangers annually. The effect of the inside design temperature and the coil face velocity on the energy recovery for a typical heat pipe heat exchanger was also investigated. In addition, heat pipe heat exchangers were simulated based on the effectiveness-NTU method, and their theoretical values for the thermal performance were compared with the experimental results.

The Effect of Geometrical Features on Air-Side Heat Transfer and Friction Characteristics, and Optimization of a Large-Size Plain Fin-and-Tube Heat Exchanger by 3-D Numerical Simulation

2009 ◽  
Author(s):  
M. Izadi ◽  
D. K. Aidun ◽  
P. Marzocca ◽  
H. Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Simple Algorithm ◽  
Operating Conditions ◽  
Friction Characteristics ◽  
Tube Heat Exchanger ◽  
Large Size ◽  
Geometrical Features

The effect of geometrical features on the air-side heat transfer and friction characteristics of an industrial plain fin-and-tube heat exchanger is investigated by 3-D numerical modeling and simulations. The heat exchanger has been designed and employed as an intercooler in a gas power plant and is a large-size compact heat exchanger. Most of the available design correlations developed so far for plain fin–and–tube heat exchangers have been prepared for small-size exchangers and none of them fits completely to the current heat exchanger regarding the geometrical limitations of correlations. It is shown that neglecting these limitations and applying improper correlations may generate considerable amount of error in the design of such a large-size heat exchanger. The geometry required for numerical modeling is produced by Gambit® software and the boundary conditions are defined regarding the real operating conditions. Then, three-dimensional simulations based on the SIMPLE algorithm in laminar flow regime are performed by FLUENT™ code. The effect of fin pitch, tube pitch, and tube diameter on the thermo-hydraulic behavior of the heat exchanger is studied. Some variations in the design of the heat exchanger are suggested for optimization purposes. It is finally concluded that the current numerical model is a powerful tool to design and optimize of large-size plain fin-and-tube heat exchangers with acceptable accuracy.

The Potential Danger of Fire in Gas Turbine Heat Exchangers

1969 ◽  
Author(s):  
C. F. McDonald
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Engine Operation ◽  
Exhaust Heat ◽  
The Subject ◽  
Gas Turbine Cycle

Increased emphasis is being placed on the regenerative gas turbine cycle, and the utilization of waste heat recovery systems, for improved thermal efficiency. For such systems there are modes of engine operation, where it is possible for a metal fire to occur in the exhaust heat exchanger. This paper is intended as an introduction to the subject, more from an engineering, than metallurgical standpoint, and includes a description of a series of simple tests to acquire an understanding of the problem for a particular application. Some engine operational procedures, and design features, aimed at minimizing the costly and dangerous occurrence of gas turbine heat exchanger fires, are briefly mentioned.

Modelling the Transient Behaviour of Heat Recovery Steam Generators

1995 ◽  
Vol 209 (4) ◽  
pp. 265-273 ◽  
Author(s):  
P J Dechamps
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Computation Time ◽  
Assisted Circulation ◽  
Steam Generators ◽  
Two Phase ◽  
Linear Heat ◽  
Numerical Predictions ◽  
Equivalent Linear

This paper describes a method used to compute the transient performances of assisted circulation heat recovery steam generators. These heat recovery steam generators are composed of several heat exchangers, each of which is a bundle of tubes. The method presented here treats each heat exchanger in a similar way, replacing the bundle of tubes with an ‘equivalent’ linear heat exchanger. This equivalent linear heat exchanger is then discretized in as many slices as required by the accuracy. The mass and enthalpy equations on each of these control volumes are solved by a fully explicit numerical method, adapted for the special conditions encountered in this kind of problem, allowing a considerable reduction of the computation time compared to other methods. Some emphasis is put on the modifications required to solve the equations for the evaporators because they are two-phase heat exchangers. A model for the steam drums is also presented together with simple models for the main control loops used in such systems. An example is presented in which an existing dual pressure level heat recovery steam generator is started from a cold state. The numerical predictions are in good agreement with measurements.

scholarly journals The influence of airflow on the effectiveness of rotary heat exchangers operating under high-speed rotor conditions

2019 ◽  
Vol 116 ◽  
pp. 00032
Author(s):  
Paulina Kanaś ◽  
Andrzej Jedlikowski ◽  
Sergey Anisimov ◽  
Borys Vager
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
High Speed ◽  
Airflow Rate ◽  
Sharp Drop ◽  
Transfer Processes ◽  
Mass Transfer Processes

The paper presents an analysis of heat and mass transfer processes occurring inside the rotary heat exchanger operating under high-speed rotor conditions for different values of the airflow rate. For this purpose the original mathematical α-model was used. Conducted computer simulations allowed to determine the influence of Number of Transfer Units (NTU) of airflow on the temperature effectiveness as well as on the distribution of different active heat and mass transfer zones: “dry”, “wet” and “frost”. It was found that the increase of the values of NTU strictly affects the increase of the effectiveness of heat recovery. Another issue emerging from this study is the fact that in the certain range of low values of NTU there is no “dry” area created. It was established that at low values of NTU (NTU≈1) “frost” area extremum and sharp drop in the “frost” area accumulation are observed.

scholarly journals CFD analysis of a dual heat recovery system

2019 ◽  
Vol 85 ◽  
pp. 02007
Author(s):  
Robert Ştefan Vizitiu ◽  
Gavril Sosoi ◽  
Andrei Burlacu ◽  
Florin Emilian Ţurcanu
Keyword(s):  
Heat Exchanger ◽  
Thermal Energy ◽  
Heat Recovery ◽  
Hot Water ◽  
Heat Transfer Analysis ◽  
Cfd Analysis ◽  
Pipe System ◽  
Recovery System ◽  
Heat Recovery System

This paper presents a CFD Heat Transfer Analysis of an originally designed system for heat recovery in the building sector. The heat exchanger has a dual role, which means it will produce simultaneously hot water and warm air. The key to the efficiency of the heat exchanger is the heat pipe system which recovers thermal energy from residual hot water and transfers it to the secondary agents. The paper includes a case study structured by different mesh distributions and flow regimes. The purpose of the heat exchanger is to reduce the costs of producing thermal energy and to increase the overall energy efficiency of buildings.

Parametric Study of Heat Insulation in Case of Plate Heat Exchangers

2015 ◽  
Vol 775 ◽  
pp. 50-53
Author(s):  
Milan Kubín ◽  
Jiří Hirš
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Insulation ◽  
Plate Heat Exchanger ◽  
Heat Losses ◽  
Heat Energy ◽  
Plate Heat ◽  
Surrounding Environment ◽  
Parametric Case

Contribution is aimed on lost heat of plate heat exchangers to surrounding environment. Heat losses to vicinity are insignificant relative to transferred heat flow in the plate heat exchangers. This small part of the lost heat is demonstrated in parametric case study of plate heat exchanger, where is the lost part of heat energy lower than 0.50 % in ordinary cases.

Refrigeration Heat Exchanger Systems for Server Rack Cooling in Data Centers

2009 ◽  
Author(s):  
Takeshi Tsukamoto ◽  
Jyunji Takayoshi ◽  
Roger R. Schmidt ◽  
Madhusudan K. Iyengar
Keyword(s):  
Heat Exchanger ◽  
Data Center ◽  
Heat Exchangers ◽  
Energy Savings ◽  
Vapor Compression ◽  
Data Center Cooling ◽  
Thermal Data ◽  
Coolant Loop ◽  
Vapor Compression System

In 2005, IBM released a water cooled heat exchanger product that significantly enhanced data center cooling capability while also demonstrating substantial energy savings. In 2008, IBM released an enhanced water less solution to cool the electronic racks via a R410A refrigerant based vapor compression system, which is the focus of this paper. The paper provides a detailed description of device and coolant loop construction, the experimental thermal data collected, as well as a discussion of its’ cooling energy efficiency relative to both typical air cooled facilities and water cooled heat exchangers, respectively. A data center level case study was performed with experimental measurements collected and discussed herein. Significant energy savings were realized even when the heat exchanger devices were implemented on a small part of the data center. Based on the test data and the experimental data center study, the CRAC units based loops have a COP of 1.95, while the refrigerant refrigerant heat exchanger loop has a COP of 5.0.

scholarly journals Temporary Uses of Urban Brownfields for Creative Activities in a Post-Socialist City. Case Study: Timișoara (Romania)

2020 ◽  
Vol 12 (19) ◽  
pp. 8095
Author(s):  
Alexandra-Camelia Marian-Potra ◽  
Ramona Ișfănescu-Ivan ◽  
Sorin Pavel ◽  
Cătălina Ancuța
Keyword(s):  
Financial Instability ◽  
Industrialized Countries ◽  
Event Space ◽  
The Public ◽  
Large Size ◽  
The One ◽  
Community Space ◽  
Urban Brownfields

The linking (in terms of functional use) of brownfield sites with creative spaces is a frequently encountered phenomenon in western European, post-communist, and industrialized countries in general and is viewed as a way of revitalizing, repurposing, or simply making temporary use of them. It may also be seen in the municipality of Timișoara in Romania, where 12 creative spaces, each involving one or more kinds of functionalities (coworking space, maker space, community space, event space, incubator), are operating on such sites. A content analysis of interviews with those in charge of these 12 creative spaces brought to light, on the one hand, the opportunities represented by the existence of derelict industrial spaces, as represented by their large size, low rents, and innate flexibility, but on the other the reality of a number of long-term constraints on the use of these spaces, given the financial instability of cultural operators, the limited numbers of the public who are interested in creative activities of this kind, and, most seriously, the development pressure exerted by some real-estate developers on derelict industrial spaces.

scholarly journals Effective Overall Heat Transfer Coefficient Solver in a Triple Concentric-Tube Heat Exchanger

2019 ◽  
Vol 70 (6) ◽  
pp. 2040-2043
Author(s):  
Sinziana Radulescu ◽  
Loredana Irena Negoita ◽  
Ion Onutu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Total Thermal Resistance ◽  
Tube Heat Exchanger ◽  
Overall Heat Transfer Coefficient

A relation for calculation of the effective overall heat transfer coefficient in a triple concentric-tube heat exchanger is proposed. The relation of the effective overall heat transfer coefficient is obtained based on total thermal resistance and it is applied within a case study for thermal analysis of two triple concentric-tube heat exchangers with different geometries, hot fluids and operating conditions. Through case study it is found that the values of effective overall heat transfer coefficient can be obtained with acceptable errors, up to 3 % for both heat exchangers.

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