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43 votes

Why not put servers in a refrigerator?

A refrigerator is basically a heat pump designed to achieve a temperature close to 0 °C. There are a couple of problems here: Most refrigerators are way too weak to effectively tackle the heat output ...
Thomas's user avatar
  • 431
21 votes
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Benefit of removing the center "engine hub" inside a fan

For a large and/or high speed fan, there are several mechanical disadvantages, for example The outer ring is highly stressed and therefore heavy. It may also need a heavy containment system to avoid ...
alephzero's user avatar
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19 votes
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Why not put servers in a refrigerator?

We do. It's just an up-sized (i.e. more powerful) version of a refrigerator known as an air conditioning unit. Essentially all server rooms and most spaces where PCs are located (speaking for the U.S.,...
reirab's user avatar
  • 306
12 votes

Why not put servers in a refrigerator?

refrigerator boxes tend to generate condensate There are specifications for acceptable relative humidity (RH) for servers. Air conditioning in server rooms will maintain RH within the allowed limits ...
Graham Nye's user avatar
12 votes

Why not put servers in a refrigerator?

Here's a webpage from a random guy who put a light bulb in his refrigerator to see what would happen, and took careful data to monitor it. Results: The next experiment was to put a 60-watt ...
Michael Seifert's user avatar
7 votes

Benefit of removing the center "engine hub" inside a fan

Fans like the one on the right exist. These where first invented as rim-driven thrusters (rim driven is your search term, not centerless) for marine applications. The rim is the rotor of the electric ...
mart's user avatar
  • 4,791
6 votes
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How do gas flow regulators avoid choking?

The short answer is that they don't. Choking is not a bad thing. For a gas flow regulator, it's actually a good thing, because under choking conditions, the mass-flow rate is no longer dependent on ...
Han-Kwang Nienhuys's user avatar
6 votes
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Fan performance curve

The yellow curve corresponds to a fan that will provide mostly a set pressure differential, say, keeping fumes from escaping a tank through elsewhere than dedicated vents. If there is a circumstance ...
SF.'s user avatar
  • 6,115
5 votes

How does one create a draft in a room (with a single window)?

The fundamental problem is that hot air must leave the room and cold air must enter it, both at the same time through the same single opening. The conflicting forces will mostly cancel each other out,...
Ray Butterworth's user avatar
5 votes
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How much does an evaporative cooler cool down a room

The capacity of an evaporative cooler depends on the relative humidity. The lowest theoretical temperature that the cooler can reach is the wet bulb temperature. The wikipedia article has some ...
pandita's user avatar
  • 377
5 votes
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How do I choose a blower design for an induced draft brick kiln?

Normally fans are not custom built by a company that does not build fans. The concept of a centrifugal fan is not particularly complicated, but it is difficult to achieve target flow rate, pressure, ...
ericnutsch's user avatar
  • 8,201
5 votes

Why not put servers in a refrigerator?

They've been doing that with computers for 30+ years. Back when computers were the size of refrigerators. They use to get a regular air conditioner. Build a platform for the computer to stand on. ...
Keith's user avatar
  • 51
4 votes
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Shouldn't enthalpies be equal in isentropic process?

Constant entropy doesn't mean constant temperature, the gas flow through nozzle is subject to change in pressure and velocity (continuity equation) due to the variation in cross section, and being ...
Algo's user avatar
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4 votes
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What's the difference between aircon modes Auto, Sun, Snowflake?

The sun is heating mode. When the room temperature reaches the set temperature, the air conditioner stops operating until the temperature falls below the set temperature and the starts operating again....
Fred's user avatar
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4 votes
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Passing by a semi truck on a highway

A truck speeding down a highway creates an envelope stream of high pressure air surrounding it. This is basically a wake, composed of layers of high pressure shockwaves, created when the front of the ...
kamran's user avatar
  • 22.6k
4 votes

What is the equivalent of a capacitor in pneumatics?

The equivalent of a capacitor in terms of pneumatics would be a chamber such as a metal sphere the size of a tennis ball. It would be necessary to have an external vacuum pump to evacuate the air ...
fred_dot_u's user avatar
  • 7,287
4 votes

What are these outdoors "mystery boxes" for in the USA?

Almost anything can be in those pedestals, but the more common inhabitant would be cable television related. The smaller ones are for subscriber taps, while the larger ones contain amplifiers or ...
fred_dot_u's user avatar
  • 7,287
4 votes

Why not put servers in a refrigerator?

The price-to-effect ratio for heat pumps is just not there for any large scale applications. Especially since air or watercooling is far less complex, and therefore a lot, lot cheaper. Dust is ...
Hobbamok's user avatar
  • 140
3 votes
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How do I convert cubic metres/feet per minute to a pounds per hour flow rate?

There are several pieces of additional information you need to go from units of volume/time to units of force/time. For gasses, temperature and pressure matter. Air is mostly nitrogen and oxygen. ...
Olin Lathrop's user avatar
  • 11.4k
3 votes

What is the purpose of a vacuum cleaner's bypass valve?

It’s purpose is to allow sufficient air to cool the motor when the filter / dirt bag is blocked - otherwise it will overheat and could catch fire.
Solar Mike's user avatar
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3 votes
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Whistle Design - Optimizing sound initiation pressure and volume

The most serious and comprehensive information about whistles is provided by the folks who work on pipe organs: expensive instruments which endure critique by serious listeners, and which require ...
elliot svensson's user avatar
3 votes

How to cool down a warehouse?

keep it under 30 degrees Celcius but everyday the temperature will goes above that No amount of ventilation when it's hot out is going to fix that. In fact, more ventilation will make that worse. ...
Olin Lathrop's user avatar
  • 11.4k
3 votes
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Cooling with fans in narrow space

No, this will not work well (as I read your plans). You should configure your fans (of any size) to draw air from inside the chassis and expel it outside the chassis. This will require vents on the ...
David Prentiss's user avatar
3 votes

Ventilation setup high sleeper night cooling

I would recommend a modification Phil's answer: airflow is almost always better when the fan is exhausting to the outside - fans don't "like" back pressure and work most efficiently when dumping to an ...
Carl Witthoft's user avatar
3 votes
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Doesn't this fan spin the wrong way?

I believe the main reason for the different blade shapes is ducted vs non-ducted fan design and tip vorticity. PC fans are essentially ducted fans with a fan-blade shape that produces tip vortices. ...
BillDOe's user avatar
  • 335
3 votes
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Will the airflow inside a vacuum hose keep a sphere centered inside of it?

No - the sphere would likely stick to one wall, or bounce between them. A sphere is not a very aerodynamic shape, having both a relatively blunt front, and sudden cut off at the back. This causes a ...
Jonathan R Swift's user avatar
3 votes

Would a plane lift from ground if in a free treadmill?

Yes. Aircrafts, other than a few which could lift vertically, create lift by moving forward in the air and bending the stream of air flow around their wings. Airplanes create the traction forward by ...
kamran's user avatar
  • 22.6k
3 votes
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What is the equivalent of a capacitor in pneumatics?

The device is called a "receiver" in pneumatics - this is basically the tank you see on any garage compressor, or much larger and more elaborate setups in industrial settings. Its function can be ...
Joel Keene's user avatar
3 votes
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Why does accuracy of temperature PID controller drop over time and how to eliminate it?

IMHO the problem you observe is mainly related to limitations of your system. Notice, that up until 55 degrees C the heating element can follow the gradient of temperature wrt to time. Just after 55 ...
NMech's user avatar
  • 24.4k
3 votes

How to determine time taken for tyre to deflate using CFD analysis?

I don't think CFD is the right tool. You can use an orifice equation, say from ASME, to calculate flow rate from inner and outer pressure. This takes the form of: $$\dot{m}=\frac{EC_D}{\sqrt{1-\beta^4}...
RC_23's user avatar
  • 791

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