Analysis of Blockages, Scaling, and Other Issues in Plate Heat Exchangers—EJS Scraper-Type Self-Cleaning Filters Installed Before Heat Exchangers
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This post was last edited by goldliyang on 2020-7-16 09:50. Heat exchangers, such as plate heat exchangers, are compact heating and cooling devices that are widely used in various industries, delivering good economic benefits. A plate heat exchanger is mainly composed of plates, gaskets, fixed end caps, movable end caps (covers), clamping bolts, bracket guides, supports, etc. It offers advantages such as compact size, high heat transfer efficiency, and ease of disassembly, cleaning, and maintenance. However, the various problems that arise in the use of plate heat exchangers also have a serious impact on production. The reasons for this are multifaceted, being related to aspects such as design, operation, maintenance, and upkeep. The blockage of heat exchangers is mainly due to the small flow channel gaps in plate heat exchangers (2.5–6 mm); particles with a diameter of more than 1.5–3 mm can easily block these channels, causing a sharp increase in pressure drop within the equipment. This leads to a significant reduction in the heat exchange capacity of the equipment, and in severe cases, it can result in interruptions in the continuous operation of the plant. Due to the high amount of impurities in the circulating water, frequent blockages occur, resulting in repeated shutdowns of the equipment and having a certain impact on the company’s economic performance. Therefore, a coarse filter or backwashing device can be installed at the inlet of the medium as needed, to effectively prevent clogging in the plate heat exchanger. Scaling in plate heat exchangers is also a major problem. Scaling can reduce the heat transfer coefficient of heat transfer equipment, and in severe cases, it can even block the channels between the plates. The plates of plate heat exchangers are designed with numerous support points, intended to disrupt the flow of the fluid (creating turbulence to increase the heat transfer coefficient) and to provide structural support. These areas are prone to the accumulation of solid debris and fibers; as a side effect, this leads to localized stagnation of the fluid, resulting in the formation of scale deposits. Calcium and magnesium ions present in the fluid can precipitate at appropriate temperatures and easily attach to these deposits, growing to form honeycomb-like scales. Although blockage and scaling have different causes, their effects on plate heat exchangers are the same. The following countermeasures can be adopted to mitigate structural problems: (1) Plate heat exchangers should not be used in dirty or scaling-prone environments (unless effective additional measures such as pre-filters are implemented). (2) When unsoftened cooling water is used as the cooling medium, the operating temperature should be controlled at around 50°C or lower in order to avoid the sensitive temperature at which calcium and magnesium ions precipitate from the medium.
The removal of hardness from water to prevent scaling on heat exchangers is a topic that has been around in the industry for over a century. After 1953, when the brothers Ludwig Taprogge and Josef Taprogge from Germany developed an automatic online cleaning device for rubber balls, this concept had an impact around the world for nearly half a century. Almost all of them improve on a common basis to create devices with similar designs and mechanisms, which can be found everywhere. With the advancement of concepts such as electronics, microelectronics, etc., every notion of miniaturization has transformed the concept of industrial equipment. The refinement of heat exchange processes has reached the nanoscale level. Improvements in traditional macroscopic heat exchange methods such as scraping, cleaning, and filtering, etc., not only fail to enhance overall energy efficiency; on the contrary, they are counterproductive, with unintended losses in microscopic efficiency that go unnoticed. The theme of this post, „Clogging, scaling, and issues in plate heat exchangers – an analysis,“ is good; adding unnecessary details only ruined things. Even if you use mechanical scraping or brushing,... it will still severely pollute the quality of the cooling water; with such severely polluted cooling water, how can heat transfer efficiency be improved?
\"Analysis of Blockage, Scaling, and Related Issues in Plate Heat Exchangers\" provides a comprehensive exploration of these problems. The caveat stated in the article is that (1) plate heat exchangers should not be used in dirty or scaling-prone environments (unless effective additional measures such as pre-filtering are implemented). (2) When unsoftened cooling water is used as the cooling medium, the operating temperature should be controlled at around 50°C or lower in order to avoid the sensitive temperature at which calcium and magnesium ions in the medium precipitate. Such a device cannot stand up to scrutiny – can it still have commercial value? Is it even meaningful?