Hot answers tagged

43

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 of modern PCs. It will not magically make your PC 6 °C - instead the PC will de-cool all your groceries. Condensation. Computers and electronics do not like ...


21

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 collateral damage if it breaks. For example in a large turbofan jet engine, a mechanical failure caused by a crack near the hub of the fan usually only releases ...


18

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., at least) are air conditioned. Server rooms almost universally have dedicated HVAC systems and they will indeed be designed to keep the room at a more-or-less ...


12

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 as well as maintaining temperature limits. You can't risk having condensation forming on electrical wiring or circuit boards as it will disrupt operation. ...


11

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 incandescent light bulb inside the fridge. ... Over the next 55 minutes, I saw the temperature in the fridge slowly creep up, while the fridge's compressor ran ...


7

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 motor driving the fans, the shroud around the rim contains the stator. With the amount of research I'm willing to do right now, I found no definitive statement ...


6

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 that reduces the pressure differential, it will speed up and increase the flow, to compensate. The blue curve is a fan that doesn't expect any significant ...


5

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, and efficiency if your company does not do it on a daily basis. If you are not able to purchase a fan, another option is to copy someone else's simple straight ...


5

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. A hole in the center of the platform. Then duct the air conditioner to the bottom of the platform. Forced air rose through the computer. For your needs - can ...


4

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 actually not a problem, just put the air intake through a room with filters (just like most mid- to high end PC cases have nowadays). For watercooled server centers, ...


3

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 degrees C, the system is unable to heat fast enough the wooden box. (probably the insulation is not sufficient). So beyond that point, the error accumulated and ...


2

Well, a couple of points come to mind: the motor behind has a similar shape or "blocking area" so will not change the efficiency very much the angular acceleration given by the blades to the fluid moving through will be so small compared to the blade section farther out from the centre the blades have to be fixed and that hub provides a secure ...


2

A typical 2 way solenoid valve would not restrict airflow towards one direction. So in your case is perfectly valid, since you will be removing the pressure from the inlet. What you would normally do if you wanted to prevent backflow is to place a check valve. Below is a cutout of typical two way valve operation states.


2

First work out your power requirements. $$ P = \frac {m \times \Delta T \times SHC} t $$ where $ \frac m t $ is the mass of air per unit time, $ \Delta T $ is the temperature rise and $ SHC $ is the specific heat capacity of air. Choose a heating wire. Nichrome seems to be readily available. Then choose a system voltage (e.g. 12 V) and calculate the ...


2

Heat transfer capacity The main problem is that a refrigerator is not potent enough for a server or a PC. A refrigerator is a type of heat pump that takes heat energy from a cool environment and transfers it to a hotter environment. On both sides, it uses convection with the natural flow of air (as opposed to forced convection). If you look at the history of ...


2

To address the problem from a more abstract, physical point of view: The problem with servers is that they produce heat. This heat has to be deduced somehow. If it isn’t, the server will heat up more and more until it breaks. Apart from temperature-dependent performance differences of the server, it doesn’t matter much at which temperature the server resides,...


2

Having a fixed airflow will not be very appropriate for the things stored in the fridge. First of all, you can't be certain what the external temperature will be. It would be preferable to use a thermostat to turn on and off the fan. Even better would be to regulate the speed of the fan again with a thermostat and some sort of PI control. The reason is that ...


2

you should look into district heating solutions. For your application the lengths are quite small so you probably can get away with using an air duct and a fan to push the air through. However, a better way is (probably optimal) to actually use a air/liquid heat pump which extracts the heat (cools down the air in one building), and heats up water which is ...


1

The bigger pump affects the smaller pump by changing the system when it is on. In this case, the bigger pump will cause the pressure at the inlet to the smaller pump to drop. The pressure drop will be proportional to the inlet pipe run. This pressure drop would reduce flow through the small pump. One could imagine a scenario where a large pump causes ...


1

There are a lot of ways. To cut cost, reduce your expensive sensors to a bare minimum - probably just measuring what goes into the reactor. Controlling by mass tends to be expensive compared to by volume or pressure. Ideal gas law is your friend here. Pressure times volume is proportional to number of particles times temperature. It's pretty inexpensive ...


1

You can buy an incense stick, which burns slowly and produces perfumed smoke. you then position the incense stick at different points in the sauna and make a video of the resulting smoke trails.


1

This NASA article discusses some of the common wind tunnel flow visualization methods. A fog machine generally uses a heated mixture of polypropylene glycol and water. You can test different mixture concentrations in an electric kettle, and use a plastic tube to plumb the fog stream to the locations you are interested in visualizing the flow. Tufts or pieces ...


1

First of all, do NOT USE EXCEL. Sooner or later it will lead to undetected errors and great sadness. Next, whether you use "Excel formulas" or proper code in tools like MATLAB or python, you need to start with the equations and formulas and boundary conditions you want to work with. Only after you have this can you start to make software do the ...


1

A typical residential refrigerator has a coefficient of performance in the neighborhood of 3, and a 150W compressor. This means it can reject heat at a rate of 150W*3=450W. This is of course just a ballpark number: some refrigerators are bigger or smaller, and the coefficient of performance will depend on things like the temperature differential between the ...


1

Let's assume you 50 W is the correct figure. Then you need to solve $50 W = C_{air}*(T_{out}-T_{in})*\dot{m}$ with thermal capacity at constant pressure C and mass flow rate $\dot{m}$ (thisgives you your volumetric flowrate.). The tricky part is $T_{out}$ - this will be between the temeprature of the stuff in your fridge (around 5°C) and the incoming air (-5°...


1

I believe what you are describing is a not-uncommon item in process industry and is often simply referred to as a rotary joint or rotary union. These rotary joints can be configured many different ways, but they are often utilized for rotating pieces of equipment such as Rotary Steam Tube Driers (RSTDs) that rotate while needing to be supplied with steam and ...


1

Creating an output from 2 inputs won't have more precision; it will have 2 sources of error. If you are trying to control relative humidity, then using that as your control variable only makes sense.


1

You are right in that the you the relative humidity will be quicker and easier to control. The question is whether that matter for your problem. Absolute humidity is the measure of water vapor (moisture) in the air, regardless of temperature. It is expressed as grams of moisture per cubic meter of air ($g/m^3$). Relative humidity is the ratio of water vapor ...


1

There is another factor here that is not being discussed. Primarily in turbo fan gas turbine engines the central hub is also a mount for the 'spinner' or 'cone'. This allows the incoming fan drawn air to be inducted in such a way as to created a convergent air flow increasing air velocity in to the fan. This process more than makes up for any induction ...


1

I mounted 20 solar panels to the roof of my Airstream, which has a curved roof. I did this using two L brackets, attached together, then one attached to the panel, through the pre-drilled hole. The other bracket is attached to the top of the trailer using VHB tape. I topped off the attachment to the trailer with eternabond tape. This works great, no drilling,...


Only top voted, non community-wiki answers of a minimum length are eligible