Portable pilot plant for evaluating marine biofouling growth and control in heat exchangers-condensers

2003 ◽  
Vol 47 (5) ◽  
pp. 99-104 ◽  
Author(s):  
J.F. Casanueva ◽  
J. Sánchez ◽  
J.L. García-Morales ◽  
T. Casanueva-Robles ◽  
J.A. López ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Pilot Plant ◽  
Economic Cost ◽  
Automatic Monitoring ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Indirect Measure ◽  
Transfer Equations ◽  
And Control

Biofouling frequently involves a serious impediment to achieving optimum operating conditions in heat exchangers-condensers. The economic cost and energy losses associated with this phenomenon are significant and the environmental impact of biocides must satisfy stringent regulations. A portable pilot plant has been designed in order to carry out in-situ experimental study as biofilm is formed under thermal and hydrodynamically controlled conditions. The pilot plant has an automatic monitoring, control and data acquisition system, which automatically processes data from indirect measure of fouling in terms of increased fluid frictional and heat transfer resistances. A particular method is used and proposed for direct measuring and biofilm characterization. Once we know the actual film thickness, we can calculate the effective thermal conductivity of the layer by using the appropriate heat transfer equations.

The Air-Side Thermal-Hydraulic Performance of Flat-Tube Heat Exchangers With Louvered, Wavy, and Plain Fins Under Dry and Wet Conditions

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Young-Gil Park ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Flat Tube ◽  
Parametric Effects ◽  
Dry And Wet Conditions ◽  
Wet Surface ◽  
Friction Performance

The air-side thermal-hydraulic performance of flat-tube aluminum heat exchangers is studied experimentally for conditions typical to air-conditioning applications, for heat exchangers constructed with serpentine louvered, wavy, and plain fins. Using a closed-loop calorimetric wind tunnel, heat transfer and pressure drop are measured at air face velocities from 0.5 m/s to 2.8 m/s for dry- and wet-surface conditions. Parametric effects related to geometry and operating conditions on heat transfer and friction performance of the heat exchangers are explored. Significant differences in the effect of geometrical parameters are found for dry and wet conditions. For the louver-fin geometry, using a combined database from the present and the previous studies, empirical curve-fits for the Colburn j- and f-factors are developed in terms of a wet-surface multiplier. The wet-surface multiplier correlations fit the present database with rms relative residuals of 21.1% and 24.4% for j and f multipliers, respectively. Alternatively, stand-alone Colburn j and f correlations give rms relative residuals of 22.7% and 29.1%, respectively.

Single-Phase Heat Transfer and Pressure Drop of Water Cooled Inside Horizontal Smooth Tubes in the Transitional Flow Regime

2010 ◽  
Author(s):  
Josua P. Meyer ◽  
Leon Liebenberg ◽  
Jonathan A. Olivier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transition Region ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Smooth Tubes

Heat exchangers are usually designed in such a way that they do not operate in the transition region. This is usually due to a lack of information in this region. However, due to design constraints, energy efficiency requirements or change of operating conditions, heat exchangers are often forced to operate in this region. It is also well known that entrance disturbances influence where transition occurs. The purpose of this paper is to present experimental heat transfer and pressure drop data in the transition region for fully developed and developing flows inside smooth tubes using water as the working fluid. The use of different inlet disturbances were used to investigate its effect on transition. A tube-in-tube heat exchanger was used to perform the experiments, which ranged in Reynolds numbers from 1 000 to 20 000, with Prandtl numbers being between 4 and 6 while Grashof numbers were in the order of 105. Results showed that the type of inlet disturbance could delay transition to a Reynolds number as high as 7 000, while other inlets expedited it, confirming results of others. For heat transfer, though, it was found that transition was independent of the inlet disturbance and all commenced at the same Reynolds number, 2 000–3 000, which was attributed to secondary flow effects.

scholarly journals Corrosion and corrosion prevention in heat exchangers

2019 ◽  
Vol 37 (2) ◽  
pp. 131-155 ◽  
Author(s):  
Willem Faes ◽  
Steven Lecompte ◽  
Zaaquib Yunus Ahmed ◽  
Johan Van Bael ◽  
Robbe Salenbien ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Prevention And Control ◽  
Metallic Materials ◽  
Corrosion Prevention ◽  
Design Considerations ◽  
Repair Costs ◽  
Anodic Protection ◽  
Different Types ◽  
And Control

AbstractIn many industries and processes, heat exchangers are of vital importance as they are used to transfer heat from one fluid to another. These fluids can be corrosive to heat exchangers, which are usually made of metallic materials. This paper illustrates that corrosion is an important problem in the operation of heat exchangers in many environments, for which no straightforward answer exists. Corrosion failures of heat exchangers are common, and corrosion often involves high maintenance or repair costs. In this review, an overview is given of what is known on corrosion in heat exchangers. The different types of corrosion encountered in heat exchangers and the susceptible places in the devices are discussed first. This is combined with an overview of failure analyses for each type of corrosion. Next, the effect of heat transfer on corrosion and the influence of corrosion on the thermohydraulic performances are discussed. Finally, the prevention and control of corrosion is tackled. Prevention goes from general design considerations and operation guidelines to the use of cathodic and anodic protection.

scholarly journals Multi-Scale CFD Modeling of Plate Heat Exchangers Including Offset-Strip Fins and Dimple-Type Turbulators for Automotive Applications

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2965 ◽  
Author(s):  
Augusto Della Torre ◽  
Gianluca Montenegro ◽  
Angelo Onorati ◽  
Sumit Khadilkar ◽  
Roberto Icarelli
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Heat Exchangers ◽  
Internal Combustion Engines ◽  
Cfd Simulation ◽  
Full Scale ◽  
Operating Conditions ◽  
Plate Heat ◽  
Multi Scale ◽  
Macro Scale

Plate heat exchangers including offset-strip fins or dimple-type turbulators have a wide application in the automotive field as oil coolers for internal combustion engines and transmissions. Their optimization is a complex task since it requires targeting different objectives: High compactness, low pressure drop and high heat-transfer efficiency. In this context, the availability of accurate Computational Fluid Dynamics (CFD) simulation models plays an important role during the design phase. In this work, the development of a computational framework for the CFD simulation of compact oil-to-liquid heat exchangers, including offset-strip fins and dimples, is presented. The paper addresses the modeling problem at different scales, ranging from the characteristic size of the turbulator geometry (typically µm–mm) to the full scale of the overall device (typically cm–dm). The simulation framework is based on multi-scale concept, which applies: (a) Detailed simulations for the characterization of the micro-scale properties of the turbulator, (b) an upscaling approach to derive suitable macro-scale models for the turbulators and (c) full-scale simulations of the entire cooler, including the porous models derived for the smaller scales. The model is validated comparing with experimental data under different operating conditions. Then, it is adopted to investigate the details of the fluid dynamics and heat-transfer process, providing guidelines for the optimization of the device.

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.

Numerical Investigation of Heat Transfer Characteristics of Different Nanoparticles Using Modified Eulerian-Eulerian Model

2020 ◽  
Author(s):  
Muzafar Hussain ◽  
Shahbaz Tahir
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchangers ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Phase Model ◽  
Heat Transfer Characteristics ◽  
Eulerian Model ◽  
Transfer Characteristics

Abstract Nanofluids are widely adopted nowadays to enhance the heat transfer characteristics in the solar applications because of their excellent thermophysical properties. In this paper, a modified Eulerian-Eulerian model recently developed based on experiments was validated numerically to account for the deviations from the experimental data. The modified Eulerian-Eulerian model is compared with the single-phase model, Eulerian-Eulerian models for TiO2-water at different operating conditions and deviation from the experimental data for each of the model was documented. However, the modified Eulerian-Eulerian model gave much closer results when compared to the experimental data. For the further extension of work, the modified Eulerian-Eulerian model was applied to different nanofluids in order to investigate their heat transfer characteristics. Three different nanoparticles were investigated namely Cu, MgO, and Ag and their heat transfer characteristics is calculated based on the modified Eulerian-Eulerian model as well as the single-phase model for the comparison. For lower values of Reynolds numbers, the average heat transfer coefficient was almost identical for both models with small percentage of error but for higher Reynolds numbers, the deviation got larger. Therefore, single-phase model is not appropriate for higher Reynolds numbers and modified Eulerian-Eulerian model should be used to accurately predict the heat transfer characteristics of the nanofluids at higher Reynolds numbers. From the analysis it is found that the Ag-water nanofluid have the highest heat transfer characteristics among others and can be employed in the solar heat exchangers to enhance the heat transfer characteristics and to further improve the efficiency.

Novel Evaporator Geometries Based on Entrance-Length Flow-Paths for Geothermal Binary Power Plants

2016 ◽  
Author(s):  
Adrian S. Sabau ◽  
Ali H. Nejad ◽  
James W. Klett ◽  
Adrian Bejan ◽  
Kivanc Ekici
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Cost Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Length Scale ◽  
Entrance Length ◽  
Scale Levels

In this paper, a novel geometry is proposed for evaporators that are used in Organic Rankine Cycles. The proposed geometry consists of employing successive plenums at several length-scale levels, creating a multi-scale heat exchanger. The channels at the lowest length-scale levels were considered to have their length given by the thermal entrance-length. Numerical simulations based on turbulent flow correlations for supercritical R134a and water were used to obtain performance indicators for new heat exchangers and baseline heat exchangers. The relationship between the size of the channels at one level, k, with respect to the size of the channels at the next level, k + 1, is based on generalization of the “Murray’s law.” In order to account for the variation of the temperature and heat transfer coefficient in the entrance region, a heat transfer model was developed. The variation of the brine and refrigerant temperatures along each pipe was considered. Using the data on pumping power and weight of metal structures, including that of all the plenums and piping, the total present cost was evaluated using a cost model for shell-and-tube heat exchangers. In addition to the total present cost, the data on overall thermal resistance is also used in identifying optimal heat exchanger configurations. The main design variables include: tube arrangement, number of channels fed from plenum, and number of rows in the tube bank seen by the outside fluid. In order to assess the potential improvement of the new evaporator designs, baseline evaporators were designed. The baseline evaporator designs include long tubes of the same diameter as those of the lowest length-scale levels, placed between one inlet and one outlet. The baseline evaporator designs were created from the new evaporator designs by simply removing most of the internal plenums employing tubes much longer than their entrance length, as they would currently be used. Consistent with geothermal applications, the performance of new heat exchanger designs was compared to that of baseline heat exchanger designs at the same flow rates. For some operating conditions it was found that the new heat exchangers outperform their corresponding baseline heat exchangers.

FRTCOILS: A General Purpose Simulation Software for Design and Prediction of Thermal and Hydraulic Performance of Finned-Tube Compact Heat Exchangers

2007 ◽  
Author(s):  
Maung Naing Naing Tun ◽  
Nilufer Egrican
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Water Solution ◽  
Finned Tube ◽  
Simulation Software ◽  
Operating Conditions ◽  
Object Oriented Programming ◽  
Compact Heat Exchangers ◽  
Cooling Coils

This paper presents computer software developed for rating and optimum selection of finned circular tubes compact heat exchangers with various coil geometries. The software is developed to use as a computing tool for commercial and R&D purposes in FRITERM A.S, an original equipment manufacturer (OEM) of finned tube heat exchangers. Finned-tube heat exchangers are highly utilized in refrigeration and process industries and heat transfer and pressure drop calculations are very important to manufactures and design engineers. For this purpose, a simulation and design software to predict the performance of finned-tube heat exchangers is presented. In finned-tube coils fin side fluid is air and tube side fluid can be water, oil, glycol water solution mixture and refrigerants. The analysis and rating of coils at dry and wet operating conditions are presented. Design and the most suitable selections of coils at the given parameters and design constraints from many different coil geometries are also performed in the software. User-friendly object-oriented programming C# is applied in developing the software. The software is developed in modular basic. Six modules are developed: Heating Coils, Cooling Coils, Condenser Coils, Steam Coils, Heat Recovery Coils and Evaporator (DX) Coils. REFPROP is also integrated in the software and all fluids’ thermal and transport properties are obtained from REFPROP. Heat transfer and pressure drop correlations available from literature are evaluated with recommendations. Simulated results are verified against experimental results.

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