取樣冷卻裝置選型指南（中英文）
各種工廠和設(shè)施都使用取樣冷卻器來冷卻來自工藝流的樣品。
作為蒸汽和水采樣系統(tǒng)的一部分，冷卻樣品對(duì)于保持樣品的安全性和代表性至關(guān)重要。
例如，如果發(fā)電廠中的樣品過熱而無法處理，操作員可能會(huì)將流量限制到不可接受的低水平，這意味著樣品不再具有代表性或可接受性。
另一個(gè)例子來自碳?xì)浠衔锛庸せ蜻^程分析。冷卻過程以處理樣品是必要的。如果用戶采集某種碳?xì)浠衔锏臉颖荆瑹o論是液體還是氣體，最安全的方式是在低于 140F 的溫度下處理樣品。這可以保護(hù)操作員在處理需要安全地帶到實(shí)驗(yàn)室進(jìn)行分析的熱樣品時(shí)的安全。
為了獲得準(zhǔn)確的數(shù)據(jù)，電力研究所 (EPRI)、ASTM 和 ASME 建議將水樣冷卻至 77°F (25°C)，以確保一致、準(zhǔn)確的測(cè)試結(jié)果。
Plants and facilities of all kinds use sample coolers to cool a sample from a process stream.
Cooling samples as part of your steam and water sampling system is essential to maintaining safety and the representativeness of the sample.
For example, if a sample in a power plant is too hot to handle, the operator might throttle the flow to unacceptably low levels, which means the sample is no longer representative or acceptable.
Another example comes from Hydrocarbon processing or Process Analytics. Cooling the process to handle the sample is necessary. If you take a grab sample of a certain hydrocarbon whether it be of a liquid or a gas, the safest way is to handle the sample at below 140F. This protects the operator when handling hot samples that need to be physically taken to the lab safely for analysis.
In order to achieve accurate data, the Electric Power Research Institute (EPRI), ASTM and ASME recommend cooling water samples to 77°F (25°C) to ensure consistent, accurate test results.
取樣冷卻器的工作原理
HOW SAMPLE COOLERS WORK
取樣冷卻器只是一個(gè)小型殼管式熱交換器，其工作原理如下：
要冷卻的樣品流過冷卻器的管側(cè)
冷卻液（通常是水）流過殼側(cè)以降低樣品的溫度。
冷卻后的樣品被送往實(shí)驗(yàn)室進(jìn)行分析或通過管道輸送到在線過程儀表，以連續(xù)監(jiān)測(cè)某些特性，例如電導(dǎo)率、pH 值或化學(xué)成分
A sample cooler is simply a small shell and coil heat exchanger that works like this:
The sample to be cooled flows through the tube side of the cooler
The cooling fluid, usually water, flows through the shell side to cool the temperature of the sample.
The cooled sample is taken to a laboratory for analysis or piped to on-line process instrumentation for continuous monitoring of certain properties such as conductivity, pH or chemical constituent
滿足需求的3 種冷卻器
3 TYPES OF COOLERS TO FIT YOUR NEEDS
有多種冷卻器設(shè)計(jì)用于液體、氣體或蒸汽工藝中的大多數(shù)應(yīng)用。
1. 螺旋盤管 – 緊湊、高效的取樣冷卻器，包括一根螺旋盤繞并安裝在殼體中的連續(xù)管。
2. 螺旋管 – 這些冷卻器具有螺旋盤管和歧管組件，安裝在緊湊的殼體中，可優(yōu)化傳熱效率和空間。盤管和殼體流道的螺旋形狀產(chǎn)生離心力，從而以真正的逆流布置增強(qiáng)兩側(cè)的傳熱。它們經(jīng)過優(yōu)化設(shè)計(jì)，可用于腐蝕性流體和氣體。
3. 管中管 – 這些螺旋纏繞的全逆流熱交換器非常適合各種需要加熱或冷卻低流速高壓和/或高溫流體的應(yīng)用。
There are several types of coolers designed for most applications in liquid, gas or steam processes.
1. Helical Coil – The most compact and highly efficient kind of sample coolers, these include a single continuous tube that’s helically coiled and fitted in a shell.
2. Spiral Tube – These coolers have a spirally coiled tube and manifold assembly fitted into a compact shell that optimizes heat transfer efficiency and space. The spiral shape of the coil and shell flow paths creates centrifugal force that enhances heat transfer on both sides in a true counterflow arrangement. They’re optimally designed for use with corrosive fluids and gases.
3. Tube-In-Tube – These helically wound, full counter-flow heat exchangers are well-suited for a variety of applications where low flow rates of high-pressure and/or high-temperature fluids need heating or cooling.
選擇取樣冷卻器時(shí)需要考慮的事項(xiàng)
CONSIDERATIONS NEEDED WHEN CHOOSING A SAMPLE COOLER
足夠的流量
真正具有代表性的樣品需要足夠的樣品流量。因此，取樣冷卻器的尺寸將由樣品所需的流速和蒸汽入口壓力決定。例如，EPRI 建議水樣的流速為每秒 6 英尺（1.8 米）。對(duì)于蒸汽樣品，由于蒸汽流向樣品面板時(shí)速度很快，因此流速較低。通常，每分鐘 500-1,000 cc 之間的流速就足夠了。
兩級(jí)冷卻
如果要將樣品送入在線分析儀，粗略冷卻可能不夠。一些分析儀，特別是電導(dǎo)率和 pH 值分析儀，對(duì)溫度非常敏感。為了達(dá)到推薦的 77°F (25°C) 溫度，樣品的兩級(jí)冷卻首先使用工廠冷卻水粗略冷卻熱樣品，然后使用機(jī)械制冷。
安裝
取樣冷卻器可以垂直或水平安裝，但最好將其垂直安裝在高溫管線上。冷卻器通常還安裝在冷卻水管道中隔離閥，以方便維修。
維護(hù)和維修
大多數(shù)冷卻器只需要偶爾對(duì)殼體側(cè)進(jìn)行除垢，這可以在拆除殼體后以化學(xué)或機(jī)械方式完成。
在為設(shè)施選擇合適的取樣冷卻器時(shí)，重要的是要考慮每條取樣管線的要求，以確保足夠的流速并優(yōu)化冷卻水的使用。
Adequate flow
A truly representative sample requires adequate sample flow. Because of this, the sample cooler size will be determined by your samples’ required flow rate and the steam inlet pressure. For example, EPRI recommends a flow rate of 6 feet (1.8 m) per second on water samples. For steam samples, flow rates are lower due to the high velocity of the steam as it flows to the sample panel. Generally, flow rates of between 500-1,000cc per minute are adequate.
Two-stage cooling
If the sample is to be fed to an in-line analyzer, rough cooling might not be sufficient. Some analyzers, particularly conductivity and pH, are very sensitive to temperature. To reach the recommended temperature of 77°F (25°C), two-stage cooling of the sample first rough cools the hot sample using plant cooling water, then uses mechanical refrigeration.
Installation
Sample coolers can be mounted either vertically or horizontally, but it’s best to mount them vertically on high-temperature lines. Coolers are also typically installed with isolation valves in the cooling water piping to facilitate service.
Maintenance and service
Most coolers need only occasional descaling of the shell side, which can be done chemically or mechanically after removing the shell.
When selecting the right sample cooler for your facility, it’s important to consider the requirements for each sample line to ensure adequate flow rates and optimize cooling water usage.
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