117 votes

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 (Why haven't they been replaced by plastics?)

There are two main reasons why glass is still preferred over say PMMA. The first is durability. As long as it isn't broken, the glass in a window can easily last for hundreds of years in good ...
Chris Johns's user avatar
  • 15.2k
47 votes

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 (Why haven't they been replaced by plastics?)

Here is a plastic (most likely PMMA) window, in a boat, after only 37 years. In addition to the obvious scratches, the outer surface has developed a cloudiness : possibly from degradation due to ...
user_1818839's user avatar
  • 1,630
31 votes

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 (Why haven't they been replaced by plastics?)

What are the requirements for window glass? Resistance to moisture Resistance to UV radiation Resistance to cleaning agents Very high transmission in the visible spectrum (There are many more, from ...
JHK's user avatar
  • 1,618
15 votes

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 (Why haven't they been replaced by plastics?)

I actually did make windows out of plexiglas for an outbuilding. I could work them to the shape I wanted and they were lightweight. However, I discovered that they indeed scratch easily: just trying ...
JDługosz's user avatar
  • 257
13 votes
Accepted

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

R134a..Here "a" is used to denote that it is an isomer. R134 and R134a have same chemical formula and atomic weight but different chemical structures. R134 has NBP of about -19 C whereas ...
morristtu's user avatar
  • 538
10 votes

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 (Why haven't they been replaced by plastics?)

After some research, we are using glass windows as it was used traditionally. Actually plastic windows exists. Though it may take time for most of us to adapt to it. While the reasons to consider ...
Fennekin's user avatar
  • 585
7 votes

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 (Why haven't they been replaced by plastics?)

Another issue is that the coefficient of thermal expansion of many plastics is higher than that of window glass. Frames for plastic windows would have to be able to accommodate more expansion / ...
r1677301k's user avatar
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
Accepted

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

$\frac{1}{22.4}\frac{\mathrm{mol}}{\mathrm{L}}$ is only valid for standard conditions. Use the ideal gas law to calculate the concentration for your conditions. $s \equiv$ standard conditions $2 \...
idkfa's user avatar
  • 1,734
5 votes

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

The Richardson number $\mathrm{Ri} = \frac{\mathrm{Gr}}{\mathrm{Re}^2} = \frac{\text{buoyancy term}}{\text{flow gradient term}}$ (1) can be used to determine if forced or natural convenction dominate ...
idkfa's user avatar
  • 1,734
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

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

Hardness aside, weathering effects (from e.g. rainfall, snow, hail, temperature and moisture variations etcetera) and UV degradation are of course important to consider for windows. In general, glass ...
rsunds's user avatar
  • 41
4 votes

Heat Exchanger Design - finding necessary variables

I found the average of the inlet and outlet pressure and temperature in the hydrocarbon stream and then used those values in the ideal gas equation to find the densities of each hydrocarbon Why would ...
Algo's user avatar
  • 2,160
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
  • 9,667
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
  • 4,696
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
  • 5,496
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
  • 6,134
3 votes
Accepted

Mass Transfer from an Oxygen Bubble

Your approach is wrong because the left hand side represents the derivative of the composition of two time dependent functions. You completely ignored that fact and started cancelling terms. I try to ...
idkfa's user avatar
  • 1,734

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