Contamination in Heat Exchangers: Types, Energy Effects and Prevention Methods

Abstract

Exchangers are thoroughly used equipment for heat transfer. These equipment play a climacteric role in variegated business administration and buildings by providing heat exchange between two fluids. However, over time, exchangers can be subject to variegated problems such as contamination and sediment build-up. This can diminish heat transfer efficiency, leading to energy waste and equipment malfunctions. Calcification is a problem that comes off when water becomes saturated with hard minerals and exceeds the solubility of these minerals. These minerals precipitate as a consequence of water evaporation or chemical reactions and form a solid layer called limestone. Limescale can bring variegated problems in homes, business administration, and water transportation systems. Lime accumulates on heat transfer superficies, reducing the superficies area of ​​these superficies. This reduces the superficies area available for heat transfer and inhibits heat transfer. The thermal conductivity of lime is lower than water. Scale, which is the formation of a scale layer on heat transfer superficies, reduces the thermal conductivity of these superficies and prevents heat transfer. This study focuses on the types of contamination in heat exchangers, the effect of contamination on heat transfer and other factors, and methods of clogging.

Introduction

Heat transfer systems play a critical role in multicolored business management and daily life. These administrations are complicated structures that meet our warming and cooling needs and play an impressive part in vitality generation. All things considered, the effectiveness and surrender of these frameworks can be undermined by an inconvenience called scaling. Scale brings several negatory efficacies to warm exchange frameworks [11Pan M, Bulatov I, Smith R. Improving heat recovery in retrofitting heat exchanger networks with heat transfer intensification, pressure drop constraint, and fouling mitigation. Appl Energy. 2016; 161:611-626.,22Guha A. Transport and deposition of particles in turbulent and laminar flow. Annu Rev Fluid Mech. 2008; 40: 311-341.]

Reduce in warm exchange effectiveness

Calcification gathers on warm exchange superficies, narrowing the zone of these superficies and discouraging warm exchange. This administers a critical reduction in warm exchange effectiveness and diminishes the abdicate of the framework. Warm exchangers may confront diminished warm exchange effectiveness over time due to variegated components such as scaling, erosion, biofilm nascency, insufficient upkeep, and the need for a separator. This may lead to the abdication of warming and cooling frameworks, administering vitality squander, and expanded costs [33Zhao B, Wu J. Modeling particle deposition from fully developed turbulent flow in ventilation duct. Atmos Environ. 2006; 40:457-466.-55Bayat M, Aminian J, Bazmi M, Shahhosseini S, Sharifi K. CFD modeling of fouling in crude oil pre-heaters. Energy Convers Manage. 2012; 64:344-350.].

Vitality squander

Diminishing warm exchange effectiveness brings the warming and cooling frameworks to expend more vitality. This results in expanded vitality costs and hurt to the environment.

Hindrance of liquid stream

Scale can gather in channels and channels, hindering the liquid stream. This circumstance makes it troublesome to transport the liquid required for the warm exchange, causing the warm exchange to decrease.

Hardware glitches

Overheating and weight buildup can come off in calcified warm exchange frameworks. This may lead to gear breakdowns and harm. Increment in Upkeep Costs: Calcified warm exchange frameworks require more visit cleaning and upkeep. This may result in an increment in working costs.

In the study of Jradi, et al. the prediction of fouling resistance in a cross-flow heat transfer was carried out using linear PLS and non-linear ANN methods. The predictive power of the developed PLS model was calculated as a correlation coefficient value of 0.992 and a predictive ability of 87%. Garson’s equation was applied to determine the sensitivity of input parameters on fouling resistance. The results showed that acid inlet and outlet temperatures were the highest relative important parameters on fouling resistance, with significance levels of 56% and 15.4%, respectively [66Jradi R, Marvillet C, Jeday MR. Estimation and sensitivity analysis of fouling resistance in phosphoric acid/steam heat exchanger using artificial neural networks and regression methods. Sci Rep. 2023 Oct 19; 13(1):17889. doi: 10.1038/s41598-023-44516-6. PMID: 37857645; PMCID: PMC10587106.]. In the study of Kazi, fouling causes gigantic financial misfortune due to its effect on taking a toll on warm trading operations, working fetched, moderation measures, and execution. The display thinks about centered on fouling wonders, fouling models, the environment of fouling, the thought of warm exchanger fouling in the plan, and relief of fouling [77Kazi NS. Fouling and Fouling Mitigation on Heat Exchanger Surfaces. In: InTech; 2012. doi: 10.5772/32990.]. In the study of Sundar, et al. in this study, a generalizable and versatile factual show was created to precisely anticipate fouling resistance utilizing parameters commonly measured in mechanical warm exchanges. Indeed with changing levels of estimation commotion within the inputs, expectations on different neural network gatherings show up to realize way better precision and vigor to clamor. The proposed profound learning fouling forecast system is found to memorize to take after the material science of warm exchange and warm exchanger stream, which is affirmed utilizing locally interpretable demonstrate rationalist portrayals around haphazardly chosen working focuses [88Sundar S, Rajagopal MC, Zhao H, Kuntumalla G, Meng Y, Chang HC, Shao C, Ferreira P, Miljkovic N, Sinha S, Salapaka S. Fouling modeling and prediction approach for heat exchangers using deep learning. Int J Heat Mass Transfer. 2020; 159:120112.].

Types of contamination and their mechanisms in heat exchangers

Calcification: Water-borne lime accumulates on heat exchanger plates or pipes, narrowing the heat transfer superficies area and obstructing fluid flow [99Kostoglou M, Andritsos N, Karabelas AJ. Flow of supersaturated solutions in pipes. Modelling bulk precipitation and scale formation. Chem Eng Commun. 1995; 133:107-133.-1111Sheikholeslami R. Nucleation and Kinetics of Mixed Salts in Scaling. AIChE J. 2003; 49(January):194-202.]. Rusting: Rusting in metal exchangers reduces heat transfer ability and can govern structural damage. Biofilm Nascency: Microorganisms can form biofilms on heat exchanger superficies, reducing heat transfer efficiency and contributing to corrosion.

Other contamination: Other sediments such as sand, mud, and oil can also accumulate in the exchangers and obstruct heat transfer.

Variegated methods can be used to obstruct the negatory effects of scaling on heat transfer systems [1212Sheikholeslami R. Calcium Sulfate Fouling - Precipitation or Particulate; A Proposed Composite Model. Heat Transfer Eng. 2000; 21(2):24-33.]:

Water softening: Water softening systems obstruct calcification by reducing the hardness of water. These systems work on the principle of ion exchange and purify water from hardness-bringing minerals such as calcium and magnesium.

Filtration: Water filters obstruct scaling by removing lime and other pollutants from water. Different types of filtration can remove different sizes of lime particles and contaminants. 

Natural methods: Natural acids such as vinegar and lemon can be used to dissolve limescale. These methods can be used for mild arthritis problems and need to be repeated regularly.

Application of magnetic field: Devices that apply magnetic fields can obstruct the nascency of lime crystals. These devices work with a mechanism that directs water molecules by a magnetic field, making it difficult for lime crystals to form.

Electronic anti-limescale: Electronic anti-limescale obstructs limescale nascency through ion exchange. These devices apply electric current to the flow of water, bringing scale-forming minerals to be ionized and carried away from the water.
Regular cleaning and maintenance of heat transfer system: Regular cleaning and maintenance of heat transfer systems is considerable to obstruct scaling. This process should be done periodically by experts and different cleaning methods may be used depending on the type of system and operating conditions.

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Abstract Introduction Discussion Conclusion References Article Info

Discussion

Factors that decrease energy efficiency in heat exchangers

Calcification, which comes off as a consequence of water becoming saturated with hard minerals and exceeding the solubility of these minerals, accumulates on the plates or pipes of heat exchangers, narrowing the heat transfer superficies area and obstructing fluid flow. This leads to a significant diminish in heat transfer efficiency. Corrosion in metal heat exchangers reduces heat transfer ability and can lead to structural damage. Rusting comes off when the metal oxidizes as a consequence of contact with oxygen and water. 

Biofilm nascency: Microorganisms can form biofilms on the superficies of heat exchangers, reducing heat transfer efficiency and contributing to corrosion. Biofilm nascency can be brought by factors such as water being rich in nutrients and oxygen and inadequate disinfection. 

Inadequate maintenance: If heat exchangers are not cleaned and maintained regularly, problems such as calcification, rust, and biofilm nascency will come off and efficiency will diminish. Lack of Insulation, insufficient insulation in heat exchangers governs heat losses and reduces efficiency. Lack of insulation comes off when the heat exchanger comes into contact with the external environment and the heat spreads to the air [1313Taberok J, Ritter RB, Palen JW. Heat Transfer; Fouling: The Major Unresolved Problem in Heat Transfer. Chem Eng Prog. 1972; 68(2):59-67.].

Methods of increasing energy efficiency in heat exchangers and their importance

Calcification can be obstructed by using methods such as water-softening systems, filtration systems, and devices that apply magnetic fields. Using anti-corrosion coatings, performing regular maintenance, and controlling the chemical properties of water help obstruct rust. Biofilm nascency can be obstructed by obstructing biofilm nascency, disinfection processes, use of biocides, and regular maintenance. Regular Maintenance; It is considerable to regularly clean and inspect heat exchangers and make necessary repairs. Adequate Insulation; Heat losses can be minimized by applying appropriate insulation material to the outer superficies of the heat exchanger. Choosing the Correct Heat Exchanger; Heat exchangers made of materials suitable for appropriate working conditions and fluids should be selected.

Additionally, reducing contamination in heat exchangers and increasing energy efficiency can also be achieved by increasing the fluid velocity [1414Kho T, Muller-Steinhagen H. An experimental and numerical investigation of heat transfer fouling and fluid flow in flat plate heat exchangers. Trans IChemE, Part A. 1999; 77:124-130.Bott TR. -1818Muller-Steinhagen H, Zhao Q, Helali-Zadeh A, Ren XG. The effect surface properties of CaSO4 scale formation during convective heat transfer and subcooled flow boiling. Can J Chem Eng. 2000 Feb; 78:12-20.]. According to the study by Mukherjee [1919Mukherjee, R., Conquer heat exchanger fouling. Hydrocarbon Processing. 1996; 121-127.], the “ideal velocity ranges” are 1.5 to 2.1 m/s and 1.0 to 1.5 m/s for the liquid inside and outside the tubes, respectively.

The efficiency of heat exchangers is critical to the yield and energy consumption of heating and cooling systems. Heat exchangers with reduced efficiency consume more energy, leading to an increase in energy costs. In addition, a diminish in efficiency may diminish the yield of the system and cause the desired heat transfer to not be achieved.

Biofilm nascency: The hidden danger in heat exchangers

Warm exchangers can considerably influence warm exchange effectiveness and surrender due to an issue called biofilm nascency. Biofilm nascency comes off when microorganisms colonize the superficies of warm exchangers and shape a sticky layer. This limits the warm exchange superficies zone, preventing warm exchange and contributing to erosion.

Mechanism of biofilm nascency

Biofilm nascency comes offs microorganisms passing through a course of action of stages:

1. Hold: Microorganisms take the essential step by taking after the superficies of the warm exchanger. This grasp can come off through variegated components such as electrostatic powers, van der Waals powers, and hydrophobic cleverly.
2. Colonization: Taking after microorganisms begin to copy and copy, forming colonies on the superficies.
3. Extracellular system (ECM) nascency: Microorganisms release a sticky substance called ECM. This substance holds colonies together and shapes the skeleton of the biofilm.
4. Advancement: The biofilm is created over time and turns into a complicated structure. Assorted sorts of microorganisms take an interest by forming different layers interior of the biofilm.

Effects of biofilm nascency on heat exchangers

Biofilm nascency brings a few antagonistic impacts on warm exchangers:

Decrease in warm exchange proficiency: Biofilm nascency hinders warm exchange by narrowing the warm exchange superficies region. This significantly diminishes the productivity of the warm exchanger and increases vitality utilization. 

Erosion: Biofilm can bring erosion on the metal superficies of the warm exchanger. Microorganisms living within the biofilm create metabolic items that quicken the oxidation of metal.

Weight increment: Biofilm nascency can bring weight increment in channels and channels by discouraging liquid stream. This may be the result of harm to channels and gear. Increment in Upkeep Costs: Biofilm nascency requires more visit cleaning and upkeep of warm exchangers. This administers an increment in working costs.

Methods to obstruct biofilm nascency

Variegated strategies can be utilized to deter biofilm nascency:

Sanitization: Standard sanitization makes a difference deter biofilm nascency. Variegated sanitization strategies can be utilized, such as chemical disinfectants, ozone, bright light, and warm. 

Utilize of biocides: Biocides are chemical substances that murder microorganisms or discourage their development. Standard utilization of biocides can offer assistance to deter biofilm nascency.

Fabric determination: It is impressive to select warm exchangers made of materials that are safer for biofilm nascency. Materials such as stainless steel and copper are more safe for biofilm nascency. 

Superficies medicines: The superficies of warm exchangers can be subjected to extraordinary medications that make biofilm nascency troublesome. These medicines may incorporate changing superficies unpleasantness or applying chemicals that hinder biofilm nascency.

Control of liquid conditions: Controlling the temperature and supplement substance of the water makes a difference in deterring biofilm nascency. Tall temperatures and the nearness of substances within the water that can be nourishment sources for microorganisms quicken biofilm nascency. Bringing down the temperature of the water circulating in warm exchangers and customary recharging or decontamination of the water contributes to hindering biofilm nascency.

Normal strategies: Utilizing metals with normal antibacterial properties, such as silver and copper, in warm exchangers or including certain sums of silver particles in water may have a decreasing impact on biofilm nascency. Be that as it may, the application of these strategies ought to be assessed by specialists and their natural impacts ought to be taken under consideration.

Selection of biofilm control methods

A single method may not be sufficient to obstruct biofilm nascency. It is more effective to adopt an integrated approach by using different methods together. The most appropriate biofilm control methods should be selected by considering factors such as the operating conditions of the heat exchanger, water properties, and cost.

Latest developments in preventing contamination in heat transfer systems

Fouling in warm exchange frameworks may be an issue that can essentially diminish warm exchange proficiency and lead to vitality squander. Subsequently, modern advances and strategies are continually being created to anticipate fouling and optimize the execution of warm exchange frameworks.
A few of the most recent improvements include:

1. Nanotechnology coatings: Nanotechnology coatings connected to warm exchange surfaces can altogether increment fouling resistance by avoiding the grip and amassing of contaminants. These coatings can have hydrophobic or hydrophilic properties and give security against diverse sorts of defilement.
2. Self-cleaning surfaces: Self-cleaning surfaces based on standards such as photocatalysis or microfluidics can consequently break down and evacuate contaminants by daylight or fluid stream. Such surfaces diminish the need for consistent support and decrease costs in the long run.
3. Bio-inspired pollution prevention: Bio-inspired pollution prevention methods inspired by pollution-resistant surfaces found in nature are being developed. These methods involve mimicking superhydrophobic surfaces such as lotus flower petals or micro-topographic structures such as seashell patterns.

Conclusion

A wide variety of heat exchangers are used on the market and are available at significant energy levels. The yield values obtained have a very significant impact on cumulative costs. Heat exchangers are critical equipment widely used in various business administrations and buildings. These equipment play an important role by providing heat transfer in heating and cooling systems, the chemical industry, food production, and many other areas. Additionally, heat exchangers can be subject to various problems over time, such as fouling and scale build-up. This can reduce heat transfer efficiency, resulting in energy waste and equipment malfunctions. Therefore, it is inevitable that costs will rise.

This study focused about centers on the sorts of defilement in warm exchangers, the impacts of this defilement on warm exchange and other variables, and strategies to anticipate these negative impacts. Scale, rust, biofilm arrangement, and other sorts of contamination can essentially decrease the effectiveness of warm exchangers. Different strategies can be utilized to anticipate these issues that decrease productivity. Strategies such as water softening, filtration, cleansing, biocide utilization, redress fabric choice, and standard upkeep can offer assistance to expand the proficiency and life of warm exchangers. The arrangement of biofilm postures is a noteworthy issue in warm exchangers. Killing this circumstance spares vitality by expanding the warm exchange proficiency to a tall level and can offer assistance in amplifying the life of the hardware by minimizing erosion. Biofilm arrangement can be minimized by utilizing strategies such as occasional support, sanitization, utilization of biocide, choice of fitting materials, and control of liquid conditions. It is of extraordinary significance to control biofilm arrangement in arrange to assist amplify the proficiency and working life of warm exchangers.

In outline, it is imperative to anticipate defilement components and perform intermittent upkeep to preserve the proficiency of warm exchangers. In this way, vitality reserve funds can be accomplished, hardware glitches can be dispensed with and the productivity of warm exchange frameworks can be optimized.

References

1. Pan M, Bulatov I, Smith R. Improving heat recovery in retrofitting heat exchanger networks with heat transfer intensification, pressure drop constraint, and fouling mitigation. Appl Energy. 2016; 161:611-626.

2. Guha A. Transport and deposition of particles in turbulent and laminar flow. Annu Rev Fluid Mech. 2008; 40: 311-341.

3. Zhao B, Wu J. Modeling particle deposition from fully developed turbulent flow in ventilation duct. Atmos Environ. 2006; 40:457-466.

4. Cui XZ, Liu QS, Zhang CY. Physical factors affecting the transport and deposition of particles in saturated porous media. Water Sci Tech-W Sup. 2017; 17(6):1616-1625.

5. Bayat M, Aminian J, Bazmi M, Shahhosseini S, Sharifi K. CFD modeling of fouling in crude oil pre-heaters. Energy Convers Manage. 2012; 64:344-350.

6. Jradi R, Marvillet C, Jeday MR. Estimation and sensitivity analysis of fouling resistance in phosphoric acid/steam heat exchanger using artificial neural networks and regression methods. Sci Rep. 2023 Oct 19; 13(1):17889. doi: 10.1038/s41598-023-44516-6. PMID: 37857645; PMCID: PMC10587106.

7. Kazi NS. Fouling and Fouling Mitigation on Heat Exchanger Surfaces. In: InTech; 2012. doi: 10.5772/32990.

8. Sundar S, Rajagopal MC, Zhao H, Kuntumalla G, Meng Y, Chang HC, Shao C, Ferreira P, Miljkovic N, Sinha S, Salapaka S. Fouling modeling and prediction approach for heat exchangers using deep learning. Int J Heat Mass Transfer. 2020; 159:120112.

9. Kostoglou M, Andritsos N, Karabelas AJ. Flow of supersaturated solutions in pipes. Modelling bulk precipitation and scale formation. Chem Eng Commun. 1995; 133:107-133.

10. Amjad Z. Calcium Sulfate Dihydrate (Gypsum) Scale Formation on Heat Exchanger Surface: The Influence of Scale Inhibitors. J Colloid Interface Sci. 1988; 132(2).

11. Sheikholeslami R. Nucleation and Kinetics of Mixed Salts in Scaling. AIChE J. 2003; 49(January):194-202.

12. Sheikholeslami R. Calcium Sulfate Fouling - Precipitation or Particulate; A Proposed Composite Model. Heat Transfer Eng. 2000; 21(2):24-33.

13. Taberok J, Ritter RB, Palen JW. Heat Transfer; Fouling: The Major Unresolved Problem in Heat Transfer. Chem Eng Prog. 1972; 68(2):59-67.

14. Kho T, Muller-Steinhagen H. An experimental and numerical investigation of heat transfer fouling and fluid flow in flat plate heat exchangers. Trans IChemE, Part A. 1999; 77:124-130.Bott TR. 

15. Fouling of Heat Exchangers. ELSEVIER science BV. 1995.

16. Bailey K. Optimise Heat Exchanger Operations By Minimising Fouling. Hydrocarbon Process. 1999 Jul; 113-127.

17. Epstein N. Fouling in Heat Exchangers. In Proceedings of the 2nd International Conference Heat Transfer. 1978.

18. Muller-Steinhagen H, Zhao Q, Helali-Zadeh A, Ren XG. The effect surface properties of CaSO4 scale formation during convective heat transfer and subcooled flow boiling. Can J Chem Eng. 2000 Feb; 78:12-20.

19. Mukherjee, R., Conquer heat exchanger fouling. Hydrocarbon Processing. 1996; 121-127.

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ME. Contamination in Heat Exchangers: Types, Energy Effects and Prevention Methods. IgMin Res. Jul 03, 2024; 2(7): 503-507. IgMin ID: igmin209; DOI:10.61927/igmin209; Available at: igmin.link/p209

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17 Jun, 2024

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02 Jul, 2024

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03 Jul, 2024

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