Questions tagged [chemical-engineering]

Use this tag for questions within the problem domain of chemical engineering.

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84 votes
9 answers
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Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Glass is fragile and impractical to transport, install and repair. Even worse, glass kills and hurts people when it breaks. Falling to the streets like guillotines during earthquakes and bomb raids. ...
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  • 1,023
14 votes
1 answer
657 views

What are some cost-effective metal substances that can wet glass?

A highly desirable property of metals like gallium and indium is that they are able to wet glass. Normally, as metals, they wouldn't be able to form an airtight seal when in contact with glass. But ...
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  • 571
13 votes
1 answer
868 views

What causes rechargeable batteries to age? What can be done to extend life of these batteries?

These days most of modern electronics use rechargeable batteries as a power source. Also, these days most modern rechargeable batteries are Lithium Ion or Lithium Polymer based. Like any other devices,...
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12 votes
3 answers
479 views

Exploiting fluid dynamics for the optimal design for gas mixing in a furnace

Background This is the standard design for a thermal furnace used in the Clauss process, which converts H2S to SO2. The main problem with the furnace is that gas mixing is rather poor and results in ...
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  • 331
10 votes
1 answer
1k views

What liquid crystals are used most frequently in displays?

Is there a specific chemical that is used frequently in the production of liquid crystal displays? During my internet research so far, it seems as if the specific chemical composition of the liquid ...
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  • 345
10 votes
1 answer
689 views

Steam sterilization of whey in a bioreactor

I'm trying to design a bioreactor to produce citric acid with whey and Aspergillus Niger. The first step in the process would be to put whey into the reactor with some dextrose (approx. 10%). Then, ...
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10 votes
1 answer
156 views

How do I choose operating parameters for input air to a methane reformer?

I'm interested in controlled oxidation of nickel in a methane reformer with diameter ~3 m and height ~1.5 m. In this reactor, CH4 is converted into H2 and CO, and CO into H2 and CO2 but for this ...
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  • 101
10 votes
2 answers
813 views

External diffusion: calculation of surface concentration

I am struggling a bit with an external diffusion problem. I am trying to calculate the concentration at the surface (as well as surface reaction rate) and would like some help or guidance. Here is ...
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  • 200
9 votes
5 answers
488 views

Why is "regular" gasoline standard instead of something more knock-resistant?

The standard light petroleum distillate for vehicle engines, "regular gasoline," is (or is equivalent to) some mix of heptane (C7) and octane (C8). Higher proportions of C8 are more knock-resistant, ...
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  • 1,785
8 votes
2 answers
17k views

What does "a" mean at the end of a refrigerant's designation (R-134a)?

I was studying the designation of names to refrigerants. The following is the basic formula: R - (m - 1) ( n + 1) ( o ) where: m = number of carbon atoms in the refrigerant n = number of hydrogen ...
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  • 575
8 votes
2 answers
5k views

Why can we neglect the inertial (but not viscous) term in Navier-Stokes at low flow and high viscosity?

Why can we neglect the inertial (but not viscous) term in Navier-Stokes at low flow and high viscosity? Complete Navier-Stokes: $\rho \frac{D\vec{v}}{Dt}=\rho g - \nabla P+ \mu \nabla ^2 \vec{v}$ ...
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  • 81
8 votes
1 answer
1k views

Estimating Darcy Friction Factors for Critical Flow

The Darcy-Weisbach equation is used to calculate the frictional pressure losses in pipes transporting incompressible fluids. This equation uses a dimensionless Darcy friction factor, also known as the ...
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8 votes
1 answer
535 views

Degassing silicone solution with negative pressure

I am planning to use polydimethylsiloxane (PDMS) to create a phantom for mimicking tissue for imaging. For this, I plan on using SYLGARD® 184, which is a viscous liquid. When adding other components ...
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  • 181
7 votes
2 answers
1k views

What are the advantages of chemical oxygen generation over compressed tank storage?

Chemical oxygen generation (COG) is used in commercial airliners to supply emergency oxygen to passengers and crew if the plane is depressurized. Weight for weight it produces far more oxygen than ...
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6 votes
2 answers
995 views

Can the Sabatier reaction power a vehicle?

The Sabatier reaction converts CO2 to methane. Can a vehicle that burns methane recover it (at least some part) from the exhaust gases via the Sabatier reaction? I am interested to know how this would ...
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  • 313
6 votes
3 answers
935 views

P&ID Symbol identification, unknown meaning

I'm aware that answers may vary and it really does depend on the company/country where the PID was drawn but I have checked back for the last 30 years and found no drawing legend that describes what ...
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6 votes
2 answers
1k views

Cleaning anodised aluminium

We have some metal parts in our machines, which are anodised aluminium. Those machines are due to be shipped to the customer in the near future, but I have noticed some pitting or slight rust ...
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  • 1,806
6 votes
1 answer
160 views

Removing water and nitrogen from reactor effluent

I wish to remove water and nitrogen from my reactor effluent in order to decrease downstream equipment sizes and subsequently capital costs. Stream composition: ${H_2S}$.................5.6% ${SO_2}...
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  • 331
5 votes
4 answers
1k views

Why do rechargeable Lithium Ion & Lithium Polymer batteries explode or catch fire?

There are many Lithium Ion and Lithium Polymer rechargeable battery related accidents. Are some of these accidents are battery design related? Are some of them misuse of rechargeable batteries. What ...
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5 votes
1 answer
119 views

What is a 'swept path' in a valve system?

I have been doing some research on valve systems for sample analyzers. In many of the valve systems' product documentation they refer to a flow path as 'fully swept'. From the context I can conclude ...
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5 votes
1 answer
838 views

How important is an ABET-accredited Engineering Degree in the EU (like Germany) or other countries that is not in North America?

I have an option to either attend Middle East Technical University - North Cyprus Campus (non-ABET accredited) or Mapua University (ABET accredited) in the Philippines to study Chemical Engineering as ...
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5 votes
1 answer
485 views

Von Karman mixing length $l=k \frac{du/dy}{d^2u/dy^2}$

In a fully developed turbulent flow of an in-compressible fluid inside a pipe of radius $R$, velocity at the center is $U_m$. If we define $U^*=\sqrt{\tau_0/\rho}$, where $\tau_0$ is the wall shear ...
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  • 159
5 votes
1 answer
581 views

Baffle vs Bottom Temperature Measurement/Control

In an industrial jacketed reactor, we have two temperature probes: one on a baffle the extends down about to the 50% fill line one built into reactor, very close to the bottom valve. When is it ...
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  • 233
5 votes
1 answer
297 views

Thermodynamics of gas exchange between gas cylinders

A synthesis gas mixture ($\text{H}_2:\text{CO}$ with molar proportion 2:1) is needed for methanol synthesis. The final mixture must be available in a gas cylinder of 50 L, say cylinder $M$, which ...
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  • 51
5 votes
2 answers
3k views

Normalization and Non-Dimensionalization of a mass balance equation

I would like to ask what is the difference (if any) between normalization and non-dimensionalization. I will try to explain what I have done until now with an equation that I would like to work with ...
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  • 101
5 votes
2 answers
837 views

Dynamic mass balance in plug flow reactor

So I would like to ask you about a problem I encountered. The case study goes like this: I want to study species distribution inside a packed bed reactor, at first at steady state but eventually what ...
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  • 101
5 votes
1 answer
2k views

How does Alloy 20 compare with Ti 6-4, C-276 and 316 stainless for corrosive service?

While I've designed tons of plastics for corrosive service, the fasteners to hold the plastics together are inevitably metallic. There have been a lot of ways to protect them from rusting (due to ...
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  • 5,323
5 votes
0 answers
62 views

Why do some pipelines have regular 90 degree deviations? [duplicate]

On this satellite image, there are pipelines extending from a terminal at sea to an LNG (Liquid Natural Gas) storage facility. Why do the pipelines, at regular intervals, deviated from a straight ...
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  • 151
5 votes
0 answers
571 views

Fluid dynamics of non interacting tanks in series

I have a system like this: and I have to estimate the height of the lower tank. First of all, I'm considering that I have a non-viscous, incompressible fluid in steady flow. Base apertures The ...
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  • 229
5 votes
1 answer
167 views

Working Out Shaft Torque in a Stirred Tank with a Cylindrical Cavern Formation (using a non Newtonian fluid)

Here is some background to the problem (in a stirred tank): "With yield stress non-Newtonian (viscoplastic) fluids, it is possible to generate an agitated volume around the impeller, defined as a ...
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4 votes
2 answers
497 views

What relationship is there between mass of water vapour produced in combustion and the energy lost through producing this water?

I am performing a number of simple heat transfer experiments with the application of a magnetic field around the fuel line to evaluate the effects. To attempt to quantify some of the heat losses in ...
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4 votes
2 answers
153 views

Nylon brittleness as function of moisture content

Can someone explain the how/why Nylons brittleness is to some degree a function of it's moisture content. I don't understand HOW the water content changes the elongation at break of the material. ...
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  • 632
4 votes
1 answer
485 views

How does conductivity $\sigma$ of salt-water depend on salinity?

In what way does the electrical conductivity $\sigma$ (or conversely, resistivity $\rho = 1/\sigma$) depend on the salinity $S$ of the saline- (or sea-) water? I know they must be in some way ...
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4 votes
1 answer
537 views

Which component of vehicle tailpipe emissions has the greatest social cost?

Emissions Emissions from vehicles have an associated social cost for everyone. We hear a lot about CO2, but CO2 is not the only thing that comes out of a tailpipe. From Wikipedia, emissions ...
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  • 10.7k
4 votes
1 answer
425 views

How to determine if mass transfer convection is natural or forced?

I know that forced convection requires some external bulk flow, but is there an equation to determine which form of Convection is dominant? I looked around and found the Richardson number $\mathrm{Ri}=...
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4 votes
4 answers
2k views

Discrepancy of calculated critical compressibility factor in Peng Robinson EoS

The Peng Robinson Equation of State gives a better approximation of the critical compressibility factor $Z_c$, where experimental data ranges between $0.24$ and $0.28$ (Source). Since the calculated ...
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4 votes
1 answer
512 views

How to separate isotopes of Plutonium?

In case of Uranium, things are lot easier, because $UF_6$ is gaseous from around 60 $\,^{\circ}\mathrm{C}$. I know, that in most cases, plutonium isotope separation is not needed, because there is no ...
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  • 2,344
4 votes
1 answer
121 views

Modelling gas desorption from a still solution (e.g. a beer)

The common way to model or estimate gas (e.g. CO2) desorption rate from a liquid solution is by using an equation similar to this one $J_{CO_2} = -k_L a(H·C^G_{CO_2} - C^L_{CO_2})$ where $J_{CO_2}$ ...
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4 votes
1 answer
337 views

Calculation of Activity Coefficient Model parameters

Here is the question, I am stuck on part B: Basically, this is my thought process so far, as $x_a \rightarrow 0$, the Henry's law line becomes tangential to the actual partial pressure curve. Henry'...
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4 votes
1 answer
50 views

silicone injection molding - making a flexible ring

I am working with silicone injection molding as a hobby and I am wanting to make a ring. I have tried with 100% silicone and the results are a clear ring that is not quite the consistency I want. I ...
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4 votes
2 answers
4k views

How does one calculate degrees of freedom in a reactor with parallel reactions?

Some time ago, I was going through some exercises and I came across a odd question, for which my atomic species degrees of freedom did not match my degrees of freedom using molecular species. I showed ...
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4 votes
2 answers
195 views

Understanding redundant pharmaceutical packaging

I ran across an interesting combination of packaging for some medicine the other day. The medicine in question was a prescription migraine medication. The exterior, cardboard package that it came in ...
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4 votes
2 answers
105 views

Eulerian description of fluid flow

In Eulerian description of fluid flow, we observe how the properties of the fluid are changing at a point. Since a point has zero dimension hence a zero area, how can we make sense of the 'finite ...
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  • 41
4 votes
2 answers
547 views

Can I control latent/sensible heat changes in a counter-flow, induced draft cooling tower using climate?

Some extensive background information to start I'm attempting to reduce water consumption at 25+ production facilities, and I've identified that the largest consumption of water (60+%) comes from ...
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4 votes
3 answers
1k views

Calculating the minimum reflux ratio for separation of Acetone and Chloroform

Acetone must be recovered from a waste process stream, which also contains chloroform , so that it can be reused in the chemical process. The chemical process requires however that before the ...
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  • 41
4 votes
1 answer
148 views

Convolution with RTD laminar flow

I have laminar flow in a tube. Consider the tube to be 0.2 m long and with an average velocity of 0.05 m/s. The analytical expression for my transfer function is: $E(t)= \frac{\tau^2}{2*t^3}$ for $t$>=...
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  • 93
3 votes
2 answers
266 views

Why do we still scuba dive with bottled air? [closed]

Breaking down water into H2 and O2 through electrolysis takes 241.8 Kj/mol. According to howstuffworks.com, the average person uses 550L of pure oxygen per day, which equates to about 24.6 moles of ...
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  • 255
3 votes
3 answers
216 views

Is there a maximum life for things made out of stainless steel or cast iron?

Do steel objects have a maximum lifespan? I read that "316 stainless steel is estimated to last for 1200 years in a “rule“ environment before heavy pitting. In the marine environment this is ...
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3 votes
1 answer
2k views

Can current passing through a wire potentially ignite gasoline? If not, why?

I am doing some restauration on my old Vespa and since the fuel indicator doesn't work, I took the fuel gauge system out of the tank and tried to understand how it works to repair it. Apparently, 3 ...
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  • 141
3 votes
1 answer
794 views

How do temperature and pressure influence the rate of evaporation of water in a closed vessel?

I am trying to solve a fairly simple question but I'm kind of stuck on the technicalities: Imagine that water is evaporating into initially dry air in the closed vessel shown schematically in Fig....
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