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,...
- 191
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 ...
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 ...
- 729
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 (...
- 15.3k
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 ...
- 4,071
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. ...
- 15.3k
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 ...
- 2,991
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 ...
- 201
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 ...
- 15.3k
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 ...
- 9,752
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 ...
- 605
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 ...
- 542
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 ...
- 5,105
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 ...
- 15.3k
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 ...
- 5,629
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 ...
- 6,182
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 ...
- 15.3k
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 ...
- 6,115
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.
- 325
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 ...
- 605
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 ...
- 121
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 ...
- 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 ...
- 11.5k
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 ...
- 335
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 ...
- 8,285
3
votes
Can CO2 produce energy to drive a bot
Potentially yes. There are a lot of homemade toys which use a reaction between vinegar and bicarbonate of soda to make simple CO2 jet engines.
However if you want to use this sort of reaction to ...
- 15.3k
3
votes
Will natural gas or propane generators also run on methane?
natural gas is methane, so no problems there. an internal combustion engine that is equipped to operate on gasoline can be converted easily to run on gaseous fuels and the conversion kits usually ...
- 15.3k
3
votes
Will natural gas or propane generators also run on methane?
The average low heating value (LHV) of biogas is around 5.5 kWh/m³ for a methane % around 40-70%, and Propane has around 24.2 kWh/m³ of LHV, and the Natural gas (NG) has around 10 kWh/m³.
Gas
LHV
...
- 31
3
votes
Accepted
Modelling gas desorption from a still solution (e.g. a beer)
In perfectly stagnate gas systems, transport of a component through a gas collapses to diffusion of the component through the gas. In this case, $k_L a \propto (D / \delta)^n$ where $D$ is diffusion ...
- 2,991
3
votes
Systems In "Thermodynamic Equilibrium"
Certainly, an isolated system at equilibrium will remain so when isolated. This example is a bit of a tautology though. But the implications are important, because we next have to consider non-...
- 2,991
Only top scored, non community-wiki answers of a minimum length are eligible