Manufacturing and Energy

Calculate Diffusion Coefficients in Liquids

technologist — Sat, 09 May 2009 00:02:42 -0700

The order of magnitude of diffusion coefficients in liquids is 10^-9 m2/s with the bulk of data in the range between 0.5 x 10^-9 m2/s and 5 x 10^-9 m2/s. Note that these data also hold for gases dissolved in liquids.

Equation of Chen and Othmer for gases is used for

� Its Simplicity
� Sufficiently Accurate
� Availability of Input Data

Correlation for liquids is that of Wilke and Chang (AIChE J. 1 (1955), 264):

Heat Capacity with Dissolved Solids

technologist — Fri, 08 May 2009 02:53:18 -0700

You are working on some design problem where a concentrated salt solution is under consideration and you are looking for its heat capacity. In such situation, will you use it to be equal to water Or it will be significantly different.

Yes, the answer is that it will be significantly different than water depending on its concentration. The deviation goes higher & higher if concentration increases.

The discussed equations are very useful for heat transfer calculations for slurry systems as well as solid handling systems.

So how to calculate it? Find out the easy way to calculate it.

Equal Percentage Valves - Opening Vs Flow

technologist — Thu, 23 Apr 2009 01:39:04 -0700

In case of equal percentage valves, the flow varies according to the following definition.

'Any % change in the opening from its current existing value changes the flow by same percentage of its current value at current opening.'

Means if current opening is say 10% & u change it to 15% than the change in opening from its current value (of 10%) is 50%, so the flow will also increase by 50% of its existing value at 10% opening. This means if flow was say 20% of the total range (Or capacity of the valve) at 10% opening it will become 30% (50% higher compared to 20%) of the total range.

So how to calculate it????

Types of Valves - Ball Valve

technologist — Mon, 29 Dec 2008 21:16:12 -0700

In the last article I discussed brief & important things about Globe Valve. Today I will discuss some basics of Ball Valve.

The Ball valves as name suggests is having a ball type spherical body. They are stop valves that use a ball to stop or start the flow of fluid. The ball performs the same function as the disk in the globe valve.

Types of Valves - Globe

technologist — Tue, 23 Dec 2008 20:58:57 -0700

In the last article I discussed brief & important things about Gate Valve. Today I will discuss some basics of Globe Valve.

The Globe valves as name suggests is having a globe type spherical body which is divided in two parts by a baffle. Flow direction is steeply changed in this type of valve so the controlling of flow is better by the movement of restriction element.

Positive Displacement Vs Centrifugal Pumps - How to Select

technologist — Sun, 23 Mar 2008 21:10:16 -0700

When to use a centrifugal or a Positive Displacement pump (PD) is not always a clear choice. To make a good choice between these pump types it is important to understand that the two types of pumps behave very differently. By looking at the performance chart below you can see just how different they are. The centrifugal has varying flow depending on pressure or head, whereas the PD pump has more or less constant flow regardless of pressure

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Can hot water freeze faster than cold water?

technologist — Fri, 22 Feb 2008 04:37:47 -0700

Hot water can in fact freeze faster than cold water for a wide range of experimental conditions. This phenomenon is extremely counter- intuitive, and surprising even to most scientists, but it is in fact real. It has been seen and studied in numerous experiments. While this phenomenon has been known for centuries, and was described by Aristotle, Bacon, and Descartes, it was not introduced to the modern scientific community until 1969, by a Tanzanian high school student named Mpemba.

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Cooling Tower: Performance calculation - I

technologist — Thu, 24 Jan 2008 21:48:03 -0700

I am invariably finding many hits on cooling tower capacity & performance calculation and related queries. Therefore, I have decided to include the detailed calculation procedure in order to enable many students & process engineers who are interested in improving cooling towers performance by following these simple steps. If you have any query, kindly post them in the comments section. I�ll try my level best to answer those queries as soon as possible. First you should collect all the data as given below. Be sure that the data collected for these temperatures is most accurate because of lower absolute level of generally ~40�C average temperatures, an error of 0.5�C due to manual data collection & judgment will cause more than 1.2% error in the result at one calculation. Repeating such errors may result in cumulative errors of more than 10% in totality giving you totally absurd results. So the basic point is that collect the data on regular basis, keep a watch to have a feel of real values & then proceed

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