Content uploaded by Sang-Ho Suh
Author content
All content in this area was uploaded by Sang-Ho Suh on Dec 23, 2019
Content may be subject to copyright.
A Study on the Formation of Fouling in a Heat Exchanging System for River Water
Abstract
When the water flowing inside of the heat transfer equipments such as heat exchangers, condensers, and boilers is heated, calcium, magnesium sulfate, and other minerals in the water are deposited and built up for scales on the heat transfer surfaces. When those scales accumulate on the heat transfer surfaces, their performance of the heat transfer become progressively reduced due to the increase of the heat transfer resistance. The mechanism of this reduced heat transfer is called fouling. This study investigated the formation of the fouling in a heat exchanger with river and tap water flowed inside of it as a coolant. In order to visualize the formation of the fouling and to measure the fouling coefficients, a lab-scale heat exchanging system was used. Based on the experimental results, it was found that the formation of fouling for river water was quite different with the formation for tap water. ??? ??뼀 ?????G?
... In this study, tap water and artificial water were chosen. Compared with the waters in Europe and America, the domestic water has less hardness [9]. Since the low hardness of water results in slow fouling, this study used hard water with high concentration to reduce the required experimental time. ...
This study investigated the efficiency of the physical water treatment method in preventing and controlling fouling accumulation
on heat transfer surfaces in a laboratory heat exchange system with tap and artificial water. To investigate the fouling characteristics,
an experimental test facility with a plate type heat exchange system was newly built, where cooling and hot water moved in
opposite directions forming a counter-flow heat exchanger. The obtained fouling resistances were used to analyze the effects
of the physical water treatment on fouling mitigation. Furthermore, the surface tension and pH values of water were also measured.
This study compared the fouling characteristics of cooling water in the heat exchange system with and without the mitigation
methods for various inlet velocities. In the presence of the electrode devices with a velocity of 0.5m/s, the fouling resistance
was reduced by 79% compared to that in the absence of electrode devices.
We researched characteristics of heat recovery rate and fouling according to structures and materials in heat exchangers like water preheater and air preheater. Economizer and air preheater have used in thermal electric power plant. we made small incinerator and heat exchangers to carry out simulated experiment. We observed fouling formation and change of heat recovery rate, combusting powdered coal for 24 hr. In economizer, fin tube type had the largest amount of fouling formation, followed by tube line type > pipe type > auto washing type according to structures. As heat recovery rate, fin tube showed highest recovery rate, followed by auto washing type > pipe type > tube line type. In air preheater, fin tube type had the largest amount of fouling formation, followed by fin plate type > pipe type > pipe type coated by teflon > pipe type coated by ceramic according to structures. And then, heat recovery rate showed the same oder.
The objectives of this study are to measure the ball recovery rate of cleaning apparatus for plate heat exchanger. Ceramic ball is used for plate heat exchanger cleaning. The main components of cleaning apparatus are comprised of ball collector, ball trap, ejector, pump and plate heat exchanger. The ball recovery rate are obtained with change in recovery time and velocity of water. The results show that the ball recovery rate is slightly increased with increase in the recovery time and the velocity of water over 0.4 m/s in the straight flow. In the case of reverse flow, the ball recovery rate more increased than straight flow. The maximum ball recovery rate of the straight flow and reverse flow reach 83.97% and 86.61%, respectively, when the velocity and cleaning time are 0.5 m/s and 15min.
The heat transfer performance of heat exchanger plate decreases as time goes by. The main reason for this phenomenon is the fouling of the heat exchanger plates. To remove the fouling, we have usually cleaned the plate of heat exchanger using chemicals or polishing brush or cloth with hand after stopping the equipment and disassembling the heat exchanger. However, to clean the plate using these methods, the heat exchanger equipment needs to be stopped and disjointed. In addition, it must be re-jointed after cleaning. Especially, the concern of environmental pollution happens in case of using chemicals. Therefore, we need to develop an automatic fouling removal equipment which can continuously keep high heat transfer efficiency and solve the problem of environmental pollution. So, in this paper, we developed and tested the equipment which can clean the fouling on heat exchanger plates automatically per constant period and interval using air bubbles. The total heat transfer coefficient decreased with a slower tendency when using air bubbles compared to the existing methods. There was 10% higher heat transfer effect air bubbles every 10 minutes for 2 hours to remove the fouling ingredients on the heat transfer surface area concerned to the case without air bubbles after 192 hours.
The objective of this study was to investigate the effecs of fouling mitigation for ceramic ball in cooling water system experimentally. The devices filled with ceramic balls were connected to the bypass line of the heat exchanging system. Cooling water in the heat exchanging system was artificial water. To visualize the formation of fouling on the heat transfer surface a number of images were obtained using a CCD camera with real-time microscopy. Fouling resistances and overall heat transfer coefficients were measured in order to analyze fouling mitigation effects. We found that the ceramic ball devices for artificial water reduced the formation of fouling compared to the no-mitigation devices.
The paper describes the mechanisms in the development of biofouling layers (initial surface conditioning, microbial transport and attachment, mass transfer of nutrients to the biofilm surface and through the microbial layer, cell metabolism, and detachment of cells and of larger parts of the biofilm) and summarizes the effects of several factors on the buildup and stability of biofilms (nutrient availability, fluid velocity and turbulence, temperature, surface condition, and nonliving particles). Mass transfer within biofilms is treated in more detail. A biofouling model applied to the development of biofilms in heat exchangers is presented. Finally, references are made to biofouling control methods (biocide and the proper design and operation of heat exchangers) and to future research needs in this area.
The objective of the present study was to investigate the behavior of CaCO3 crystal formation at the very beginning stage of fouling. This article describes an experimental method which employs a light microscope system to visualize crystal growth behavior during the fouling process inside a transparent rectangular channel. Crystal visualization data are presented to examine the crystal growth behavior of calcium carbonate crystallizing from hard-water fouling. The present study provides crystal growth data as a function of time, which includes crystal creation, crystal growth, the number of crystals, and removal process. Both the rate and location of crystal growth were found to be dictated by small seed crystals formed in the early stage of fouling. The removal rate was found to be almost negligible compared to the deposition rate.
This paper presents a new winding method in electronic descaling (ED) technology. Conventional ED technology Produces an oscillating electric field via Faraday`s law to provide the necessary molecular agitation to dissolve mineral ions. However, the proposed method produces an additional agitation force for mineral ions, called Lorentz`s force. Experiments were performed using various Renolds numbers. A series of tests was conducted to measure the pressure drop across the test section and the overall heat transfer coefficient as a function of time. In order to accelerate the rate of fouling, artificial hard water, 1000ppm CaCO_3, was used throughout the tests. The results show that the new winding method accelerates the collision of the mineral ions, thereby improving the system efficiency. The present study can develope more effective fouling-removing equipment with change of estabishment method of coil.
Method and Apparatus for Treatment of Flowing Liquids to Control Deposition of Solid Matter Thereform
- D L Moody
- D L Moody
European Community R&D Strategy in the Field of Heat Exchanger Fouling. Project,' Fouling Mechanisms, Theoretical and Practical Aspects
- P A Pilavachi
- J D Isdalem
Prevention of Particulate Scale with a New Winding Method in the Electronic Descaling Technology
- Koo Sang-Mo
- Kim Chang-Soo
- Kim Gun-Woo
- Sohn Chang-Hyun