A centrifugal spin on a 500-year-old air compressor design
1–10 of 64 posts
Re: A centrifugal spin on a 500-year-old air compressor design
#2Interesting. A few questions that come to mind:
1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger applications, refrigeration-based dehumidifiers are needed. If the use of water in the compression stage leaves the dew point significantly higher than what you get from reciprocating or Roots-type compressors, that added complexity could be a deterrent to adoption.
2. What's the energy efficiency of the process? Does the claimed "20% lower cost of ownership" account for the difference in efficiency (whatever it is)?
3. What sort of pressures can be achieved with a tabletop or shop-sized compressor? Presumably, this is related to the speed at which the drum is spun, but what are the practical limits?
I mean, I use a decent amount of very dry air at 300 bar (yeah...), and I'd love to replace the noisy beast of multi-stage compressor with something quieter and more efficient.
Re: A centrifugal spin on a 500-year-old air compressor design
#3Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
I'm certainly no expert, but as they pointed out this is basically a trompe, which...
>Compressed air from a trompe is at the temperature of the water, and its partial pressure of water vapor is that of the dewpoint of the water's temperature. If the water is cool, the compressed air can be made very dry by passing it through pipes that are warmer than the water. Often, ordinary outside air can warm the pipes enough to produce dry, cool compressed air.
[https://en.wikipedia.org/wiki/Trompe]
So use a better heat exchanger to cool the water, and then heat up the air until it's dry enough, I guess?
Re: A centrifugal spin on a 500-year-old air compressor design
#4Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
If there was liquid with vapor benign in your use case, you could substitute that. Also, since you're doing compression, you would have less water vapor than with something like a water aspirator (vacuum ejector, or Venturi effect vacuum pump.)
Re: A centrifugal spin on a 500-year-old air compressor design
#5Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
I didn't realize that air compression hardware has to deal with water removal but apparently it does. One article I found is suggesting that air at 7 bar can hold about 1/3 as much water. What confused me is that the a wing stall (low pressure above a wing) causes cloud formation, due to vapor condensing out of the air.
But 7 bar is ~7 times as much air per cubic centimeter, so that's 14% as much space containing 33% as much water. The partial pressure doesn't drop at a 1:1 ratio.
As a former owner of many water management devices from pet fountains to humidifiers to dehumidifiers, I'm more concerned about the fact that air is full of particulates, and you're going to wash the particulates through a fluid that stays in the pump permanently, so how quickly is the funk going to make that compressor unpleasant to be around?
Re: A centrifugal spin on a 500-year-old air compressor design
#6Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
If the water is saturated with a salt, it could actually dehumidify the air, https://www.youtube.com/watch?v=R_g4nT4a28U
Re: A centrifugal spin on a 500-year-old air compressor design
#7Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
I'm certainly no expert, but as they pointed out this is basically a trompe, which... >Compressed air from a trompe is at the temperature of the water, and its partial pressure of water vapor is that of the dewpoint of the water's temperature. If the water is cool, the compressed air can be made very dry by passing it through pipes that are warmer than the water. Often, ordinary outside air can warm the pipes enough…
A heat pump could be used to cool the water to below-ambient and inject that heat directly into the outgoing compressed air. I wonder if a system like that would be more efficient than installing a separate refrigeration-based system downstream?
Re: A centrifugal spin on a 500-year-old air compressor design
#8Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
That and if ever accidentally you get water in your lines and you run piston based tools on them you'll end up with hydraulic lock and/or bits of your tools all over the place.
Re: A centrifugal spin on a 500-year-old air compressor design
#9Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
I was wondering the same thing, re: dry (or not) air. I’ve spent a good bit of $ on a drying system for my setup.
Also: I’ve seen water vapor in the compressor ruin an otherwise nice paint job.
Re: A centrifugal spin on a 500-year-old air compressor design
#10Interesting. A few questions that come to mind: 1. What is the dew point of the compressed air? Many applications using compressed air require very dry air so as to avoid corrosion issues (e.g., air tools) as well as problems related to heating of water vapor (e.g., tires). For small applications, the dew point is reduced using simple traps, silica gel beads, or molecular sieves, but for even-drier air or larger appl…
I didn't realize that air compression hardware has to deal with water removal but apparently it does. One article I found is suggesting that air at 7 bar can hold about 1/3 as much water. What confused me is that the a wing stall (low pressure above a wing) causes cloud formation, due to vapor condensing out of the air. But 7 bar is ~7 times as much air per cubic centimeter, so that's 14% as much space containing 33%…
Looks like there is a filter on the air intake, probably partially for that latter reason (larger particulates could be a problem mechanically also).