Calcium sulphate scale formation during subcooled flow boiling

Najibi, Seyed Hesam; Müller‐Steinhagen, Hans; Jamialahmadi, M.

doi:10.1016/s0009-2509(96)00505-2

Cited by 88 publications

(27 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The simplified scheme of the test heater, with the thermocouples' location in it, is demonstrated in Figure 2. This type of heater has been extensively used for fouling research by the other investigators (Najibi et al, 1997;Helalizadeh et al, 2000). The temperature drop between the thermocouple location and the heat transfer surface can be calculated from:…”

Section: Literature Reviewmentioning

confidence: 99%

Experimental study of micro-particle fouling under forced convective heat transfer

Peyghambarzadeh

Vatani

Jamialahmadi

2012

Braz. J. Chem. Eng.

Self Cite

View full text Add to dashboard Cite

-Particulate fouling studies of a hydrocarbon based suspension containing 2 µm alumina particles were performed in an annular heat exchanger having a hydraulic diameter of 14.7 mm. During fouling experiments, the classical asymptotical behavior was observed. It is shown that particle concentration, fluid velocity, and wall temperature have strong influences on the fouling curve and the asymptotic fouling resistance. Furthermore, a mathematical model is developed to formulate the asymptotic fouling resistance in terms of the mass transfer coefficient, thermophoresis velocity, and fluid shear rate. The results demonstrate that the prediction of the new model is in good agreement with the experimental observations.

show abstract

Section: Literature Reviewmentioning

confidence: 99%

Experimental study of micro-particle fouling under forced convective heat transfer

Peyghambarzadeh

Vatani

Jamialahmadi

2012

Braz. J. Chem. Eng.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The 'S' shape can be obtained if the nucleation period is considered in the development of fouling. The period of nucleation may vary from seconds to hours depending on the temperature, concentration and the velocity [7]. However, Figure 7 presented by Hamed and Al-Otaibi [29] shows the fouling behaviour in MSF brine heater and the shape of the curve does not look like 'S' shape.…”

Section: Fouling Resistancementioning

confidence: 98%

“…Though Helalizadeh et al [40] reported a decrease in the mass deposit rate with increase in the velocity during convection heat transfer and sub-cooled flow boiling experiment, Najibi et al [7], Helalizadeh et al [11] and Peyghambarzadeh et al [54] reported that the fouling resistance increases with increase of the flow velocity. They explained that the diffusion mechanism has some control on the fouling resistance at certain velocities and then when the velocity increased further, the fouling became completely reaction control and the deposit rate is flow velocity independent.…”

Section: Effect Of Flow Velocitymentioning

confidence: 99%

“…Helalizadeh et al [11] and Fahiminia et al [34] reported that at low velocity, the fouling is controlled by diffusion rate while at high velocity, the controller mechanism changes to be reaction rate. Moreover, Najibi et al [7]assumed that the fouling process is controlled by diffusion mechanism when the velocity bellow 0.9 m/s. Also, Andritsos et al [35] reported large indication of diffusion controlled process when they tested two velocities below 0.9 m/s on the activation energy.…”

Section: Deposit Ratementioning

confidence: 99%

“…Non-alkaline scale such as calcium sulphate (CaSO 4 ), on the other hand, is also considered to be the most common scales found in MSF process [5]. Nevertheless, Anhydrite sulphate scale (CaSO 4 ) would be expected to form at temperature above 40 o C due to its low solubility ( Figure 1) [6], most of the calcium sulphate scale in thermal units is hemihydrate [7,8]. However, there is large agreement among the MSF fouling researchers that CaSO 4 , in any forms, precipitates in MSF plants at temperature above 120 o C [5].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dynamic modelling of Heat Exchanger fouling in multistage flash (MSF) desalination

Alsadaie

Mujtaba

2017

Desalination

View full text Add to dashboard Cite

Fouling on heat transfer surfaces due to scale formation is the most concerned item in thermal desalination industry. Here, a dynamic fouling model is developed and incorporated into the MSF dynamic process model to predict fouling at high temperature and high velocity. The proposed dynamic model considers the attachment and removal mechanisms in the fouling phenomena with more relaxation of the assumptions such as the density of the fouling layer and salinity of the recycle brine. While calcium sulphate might precipitate at very high temperature, only the crystallization of calcium carbonate and magnesium hydroxide are considered in this work. Though the model is applied in a 24 stages brine recycle MSF plant, only the heat recovery section (21 stages) is considered under this study. The effect of flow velocity and surface temperature are investigated. By including both diffusion and reaction mechanism in the fouling model, the results of the fouling prediction model are in good agreement with most recent studies in the literature. The deposition of magnesium hydroxide increases with the increase in surface temperature and flow velocity while calcium carbonate deposition increases with the increase in the surface temperature and decreases with the increase in the flow velocity.

show abstract

Enhancing flow boiling and antifouling with nanometer titanium dioxide coating surfaces

Liu

Wang

2007

AIChE Journal

View full text Add to dashboard Cite

This article aims to develop a new heat-transfer surface on which both heat-transfer enhancement and fouling prevention can be observed. One of the potential methods is to coat a thin layer on the heat-transfer surface with nanometer material. The selection of coated nanometer material, the preparation, and characterization of nanometer coatings on heat-transfer surface, including the measurement and calculation of the coated thickness, contact angle and surface free energy, the experiments on heat transfer of flow boiling and antifouling are all investigated in this article. The results declare that heattransfer film coefficients of flow boiling on TiO 2 coating surfaces with film thickness of 1.41 Â 10 À7 and 1.587 Â 10 À6 m are higher than those on uncoated surface of heated tube. The fouling resistance on the surface modified with nanometer material is lower than that on the untreated heat-transfer surface and remains constant during a long operating time. Under present experimental conditions, the coated heat-transfer surface with thin film thickness of 1.41 Â 10 À7 m is the best one in enhancing heat transfer of flow boiling and preventing fouling, since its surface free energy is the lowest one.

show abstract

Calcium sulphate scale formation during subcooled flow boiling

Cited by 88 publications

References 22 publications

Experimental study of micro-particle fouling under forced convective heat transfer

Experimental study of micro-particle fouling under forced convective heat transfer

Dynamic modelling of Heat Exchanger fouling in multistage flash (MSF) desalination

Enhancing flow boiling and antifouling with nanometer titanium dioxide coating surfaces

Contact Info

Product

Resources

About