h a l f b a k e r y
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The standard drip coffee maker is a remarkable machine.
Perhaps the most remarkable thing is the lack of
remarkable things within. As machines, they seem durable
at a level not attained by much else, especially consumer
products that handle water. We have 4 dead examples in a
at work. They're not actually dead,
someone just dropped the glass carafe. The local diner has
an example from the late '60s that as far as I can tell has
been in continuous 24Hr operation since it was bought.
The key lies in simplicity. The business end is a heated
tube in the base. Cold water is fed to this from a tank and
when the temperature rises above boiling point the
steamy-water mix expands and is forced up to the coffee
basket. This water is replaced by more from the tank,
usually via the only moving part: a one-way valve.
Central heating systems, the type with water pipes and
radiators, are a lot like coffee machines. They have a gas
boiler on the ground floor/basement that heats water, this
is then electrically pumped to the radiators. Sadly the
durability isn't in the same league as coffee makers. Their
reliability is also lower, since they rely on a gas supply AND
an electrical supply to function. Should electricity be
unavailable or the pump malfunctioning, you might freeze
to death despite a plentiful supply of fuel. This would be
To prevent such embarrassment, I recommend a coffee-
maker inspired pumping mechanism. The gas boiler heats
water which is ejected up to the top of the radiator in the
highest room. Here it fills the radiator until it overflows
down the return pipe to the radiators on lower floors and
ultimately the main tank. Flow can be regulated by manual
and thermostatic valves as normal. To simplify the system
further, the one-way valve should be eliminated. To do
this, the holding tank and/or heating coil should be
designed as a fluid inerter <link>. When the boiling water
rapidly expands, the supply-side inerter will dramatically
bias the pumping in the desired direction, a Tesla valve
could also be added for the cool factor, depending on how
cool you find inerters or Tesla valves.
To dramatically increase the effectiveness of the system,
water can be replaced with mercury. Radiators operating
at ~350C can be smaller and mercury has excellent
inertance and antimicrobial characteristics.
[bs0u0155, Mar 04 2019]
Capacitor fluid equivalent
Mentioned in my anno. From [wbeaty] [notexactly, Mar 08 2019]
||Hmm. I'm not convinced that I'd enjoy the gurgling noises.
||A mercury-loop system would be interesting, but I don't think
you'd be able to use soldered joints, and I'm not sure how well
push-fit would stand up to 350°C, so you'd be lumbered with
||//lumbered with compression fittings//
||Small leaks aren't a major issue. Mercury will find its own
way back down to the basement. In fact, there's no real
need for the return piping at all. Just try and make sure any
aluminum belongings are kept out of the larger streams.
||And... cue [8th] suggesting NaK.
||I think I would be interested to visit a house with radiators at -350°C
||I think a lot of physicists would too.
||I'm not sure I'm understanding how the inerter concept
applies here, though. It appears to me to be just an inductor
for liquids. Are you just putting it behind the boiler, as a
low-pass filter to direct the expansion forward?
||//Are you just putting it behind the boiler, as a low-pass
filter to direct the expansion forward?//
||Exactly that. It's performing the function of the valve
without any of that nasty wearing out business.
||//It appears to me to be just an inductor for liquids//
||I'm not sure, I'm slightly out of my depth when it comes to
liquids. I arrived at the inerter via its use in F1 suspension
systems. The original wasn't fluid, it was mechanical.
Suspension travel was used to spin up a flywheel. It was
particularly good at smoothing oscillations as it resists
||I followed the concept to a guy named Malcolm Smith at
Cambridge. His explanation draws parallels between
dampers and resistors, which I get. However, he equates
springs with inductors and inerters with capacitors. I'm
not comfortable with those, possibly because I don't
understand. To me, a spring will not smooth oscillations
while an inductor does, and an inductor will not store
force like a spring. The inerter specifically resists
CHANGE in input, storing that energy in another form.
||It's fascinating, I thought all the mechanical stuff was
done, we've been messing with wheels and cogs and
levers etc for centuries, electronics for a few minutes by
comparison. Is there an electronic equivalent of the self-
closing valve in a ram pump?
||Diode or perhaps a transformer.
||// However, he equates springs with inductors and inerters with
capacitors. I'm not comfortable with those //
||Me neither. When I use a hydraulic analogy to explain electricity (which is
not that often) I typically think of a paddle wheel/vane pump thing
connected to a flywheel as the equivalent for an inductor. And a capacitor
becomes a rubber membrane with water connected on both sides [link]*, which is a kind of spring.
||*That is just to be equivalent to an electrical capacitor; in real hydraulics you can also have a
membrane or spring-loaded piston that's open to the environment on the other side, which is, I guess,
equivalent to a capacitor with the other side grounded.
||// Is there an electronic equivalent of the self- closing valve in a ram
||I often describe hydraulic rams as boost converters for water, though the
operation is not exactly equivalent.