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7 votes

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

Strictly speaking, very few metals are "stable" in terms of the laws of thermodynamics. True chemical stability is when the atoms are in their lowest energy state. For most metallic elements,...
Brian Ensign's user avatar
6 votes

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

For a combustible mixture to ignite, it must be within its flammability limits. This forum provides an anecdotal explanation for gasoline's inflammability in an automobile tank: ...when the tank is ...
Bruce Kirkpatrick's user avatar
6 votes

P&ID Symbol identification, unknown meaning

This is an instrument symbol, they are read in the following way, ISA Symbology The symbology of the instrument it is placed in a circle of 7/16 “or 12 mm (see below), was in the top there is ...
DrMrstheMonarch's user avatar
5 votes

foam earplugs: what’s the composition of the (non washable) substance that slow down their expansion?

That sticky oily substance found in the ear plug foam is the plasticizer leaching out. The plasticizer is unlikely to be added on after the foam is made, I think it would be mixed in with the source ...
Netduke's user avatar
  • 1,109
5 votes

Why do we still scuba dive with bottled air?

Bottled air is used for SCUBA because it is simple, reliable and relatively inexpensive and an open circuit system with a demand valve is pretty safe to use. There are closed circuit systems (...
Chris Johns's user avatar
  • 15.2k
5 votes
Accepted

Nylon brittleness as function of moisture content

Nylons are a class of polymers formed from di-acid and di-amine monomers. The amine groups bond with the acid groups to form amide groups, end to end. The resulting amide groups have a positive charge ...
do-the-thing-please's user avatar
5 votes

Why lead was chosen as the metal for lead-acid batteries?

each electrochemical reaction involving a lead atom in a lead-acid cell releases two electrons into the external circuit, which means it has a relatively good extractable power-to battery mass ratio. ...
niels nielsen's user avatar
5 votes

How can I vaporize metals?

The easiest way to vaporize a metal is to create a filament of the metal. Heat the filament in the vacuum to its sublimation (vaporization) temperature. Alternatively, when the metal cannot be shaped ...
Jeffrey J Weimer's user avatar
4 votes

How to hermetically seal a circuit in a visual & bluetooth transparent solid cube ~2-3"?

The process of encasing electronics in a material is called potting. Various resin materials can be used, such as polyester resin or epoxy. Discussion of the types of resin can be found in this ...
Colin D Bennett's user avatar
4 votes
Accepted

Diesel or Gasoline? Which one is more dangerous to our health?

1) In an engineering context efficiency has a very specific meaning ie it is the ratio between the energy you put into a system and the useful work that you get out. In itself this doesn't tell you ...
Chris Johns's user avatar
  • 15.2k
4 votes

Why do we still scuba dive with bottled air?

A scuba diver needs more air per minute than only 7 to 8 liters, because he is not at rest. A diver swimming with moderate speed needs about 20 to 25 liters per minute. But this is the consumption at ...
Uwe's user avatar
  • 201
4 votes

Meaning of kWh/tcoal

On average, the power plant produces 100 MW of electricity, or 100 000 kW of electricity. Per tonne of coal burned, the plant produces 5100 kWh. Thus, the average amount of coal the plant burns per ...
Fred's user avatar
  • 9,687
4 votes

specific energy consumption vs plant load

This is a great question, though I feel it should be refined a bit and have the main question stated more explicitly. That being said, I will attempt to answer it with the assumption that the question ...
ChemE mang's user avatar
4 votes

Advantages of hydrogen gas turbine over fuel cell

I've read in one of Smil's books that fuel cells are somehow limited (in what sense I'm not sure anymore but I believe it was power output) by their "active area". I'm having difficulties learning ...
baltakatei's user avatar
4 votes

Why are there no propane refrigerator air-conditioning units that run on solar heat?

It is a lot more efficient to convert the solar to electricity and run a decent heat pump for AC and normal refrigeration. Absorption refrigeration is expensive, bulky, not terribly versatile, and has ...
Phil Sweet's user avatar
  • 4,765
4 votes

Why are there no propane refrigerator air-conditioning units that run on solar heat?

This was my senior team project in engineering school, in 1974. Here were our findings: The power needed to run a small absorption refrigerator can be supplied by a solar collector of about 32 square ...
niels nielsen's user avatar
4 votes
Accepted

Why Sintered Tantalum Powder Forms a Sponge-Like Structure?

Anything sintered has a sponge like structure with pores. That's what sintering is. For example, oil-impregnated bronze for use as self-lubricating bushings. You're compressing the metal powder so ...
DKNguyen's user avatar
  • 5,641
4 votes

How the choice of etchant can affect the severity of hydrogen embrittlement during pickling and passivation?

The primary cause of hydrogen cracking is a susceptible matrix . Typically a carbon or low alloy steel that is hard ( > HRC 25) untempered is the primary problem. The martensitic chrome steels were ...
blacksmith37's user avatar
  • 6,154
3 votes
Accepted

Centrifugal pumps working

To address the first point without further clarification from your side: I think you mean unstable pump curves with that. Otherwise I wouldn't know how you could achieve a higher operating head than ...
idkfa's user avatar
  • 1,734
3 votes

What is the plastic blister chemical compound that stores plastic toys?

To answer a question like this I would look up blister packaging and see what materials are commonly used: Blister packaging article Note the article I have linked above suggests some possibilities: ...
Andy's user avatar
  • 285
3 votes

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

Here is a good resource that has very detailed information about Li-Ion hazards: Lithium-Ion Batteries Hazard and Use Assessment (Lithium-Ion Batteries Hazard and Use Assessment. Celina Mikolajczak, ...
jpa's user avatar
  • 1,953
3 votes

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

Well first and foremost, refiners are a business so they must make the decisions that make them the most money. Considering this, lets think about cracking and isomerization via catalysis. The refiner ...
ChemE mang's user avatar
3 votes
Accepted

silicone injection molding - making a flexible ring

If you are using RTV silicone of the type used for prosthetics and animatronics then you can get a variety of grades with different mechanical properties, commonly rated by Shore Hardness. You can ...
Chris Johns's user avatar
  • 15.2k
3 votes

Boiling Point, Pressure and Distillation

In ambient pressure, ethane boiling point is -89 °C; ethylene boiling point is -103.7 °C. Water, to act as efficient coolant needs to be liquid, so above 0 °C. You're not going to condense ethane ...
SF.'s user avatar
  • 6,105
3 votes
Accepted

Calculation of Activity Coefficient Model parameters

There was an error in the question, the model in the question is the van Laar activity model, the coefficient for $\ln \gamma_2$ on the numerator should be B, in this case, it is easily solvable.
MathsIsHard's user avatar
3 votes

Valve first,then heat exchanger OR heat exchanger first then valve

I think the key information is that the liquid is saturated. This means any reduction in pressure will lead to partial vaporization and two phase flow. For heat tranfer best overall heat transfer ...
Ohio ChemE's user avatar
3 votes

is it possible to achieve 1000C temperature in a cabin?

If the heating element is constantly at 100°C, there is no way it can cause the room can get warmer than 100°C. Otherwise, perpetual motion machines would be possible. If you meant the heating ...
Bob's user avatar
  • 64
3 votes

How can i obtain heat from conductive paint using dc current

If you end up with something that conducts current, it will heat up with applied current. One way or another, you have what is called a resistor. A resistor dissipates power proportional to the ...
Olin Lathrop's user avatar
  • 11.4k
3 votes
Accepted

Failure of N.R.T.L method to model Phenol / Methylcyclohexane / Toluene system in AspenPlus. Why?

At moderate temperatures and pressure NRTL should be a good option provided that the binary interaction parameters are correct. You need to check: Whether the binary interaction parameters for your ...
Toulousain's user avatar
3 votes
Accepted

Why lead was chosen as the metal for lead-acid batteries?

Lead acid batteries has been around a long time and is easy to manufacture. They are rechargeable, recyclable, and reasonably safe. AGM or Absorbent Glass Mat lead acid has the added benefit of being ...
ericnutsch's user avatar
  • 8,181

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