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The instructions for the simplest, cheapest and possibly
most unsafe DIY Induction Shower Heater are as
1. Screw a portable induction stove sideways to a wall,
well away from where water can splash upon it.
2. Take an induction-rated pressure cooker. In place of
valve, bore a hole. To this hole affix the water
3. Bore another hole on the pressure cooker's wall, and
this hole affix the water outlet hose to which the
4. Mount the pressure cooker onto the induction stove
the outlet pointing downward. Anchor the pot to the
with some degree of creativity. A frame perhaps. But
definitely not adhesive.
5. Voila. After use, DO NOT FORGET to switch it off.
(?) Heat Wayv
microwave domestic water heater
grr... bad... snakeoil... [Frankx, Sep 29 2021]
With hot water, under-floor heating, & radiators. [neutrinos_shadow, Sep 29 2021]
heat wayv microwave boilers
Fixed link for article on "grr... bad... snakeoil..." heater [a1, Oct 26 2022]
|//In place of the regulator valve, bore a hole.//
|The regulator valve would normally be in the top of the
pressure cooker, where the steam comes out when
necessary - right? And yet, you're turning this into in inlet
port, while your outlet port is further down the pot -
|Since you have two holes in the pot, you're no longer
regulating its pressure. It's now just a pot - unless ... the
heat is, by implication, coming from the portable
induction stove, but are you adding further heat with a
heating element built into the pressure cooker?
|So, now you're powering two heating elements, one inside
the pot, the other one outside. But a pressure cooker
with its own heating element, unlike a normal stove-top
pot, is designed to have insulating walls, not conducting
walls, isn't it? So, the induction stove is acting mostly as
a shelf-cum-space-heater, and contributing little to the
heating of the water. So, are you living in a very cold
climate, where your shower cubicle needs its own space
|Hey I have a cheaper one. 1. fix a parrafin blowtorch to spout of galvanised watering can using duct tape. 2. Light blowtorch and fill can with water. 3. Hold contraption above head and pour.
|Anyone want to step up another rung?
|This reminds me of microwave water heating - it's possible
to heat water for your home more efficiently than any other
method by focussing microwaves on water flowing through a
plastic pipe. Because the pipe diameter and flow rate are
known, the microwave emitter can be optimised. Microwave
home heating systems are now in development, I think.
|I don't get it. If you convert, say, 1kJ electrical energy into
thermal energy in water, you get 1kJ heat in your water. A
normal resistance heater will achieve 100% efficiency - why
use induction or microwaves?
|I suppose you can dynamically adjust the power (heat input
to your water) more finely with a microwave heater - but
that works out the same as using a thermostat shower
mixer (in terms of total energy).
|I kind of like the dangerous DIY version in the original idea.
|//Microwave home heating systems are now in
|What? I invented that when I was about 12, my brother
thought it was a good idea and I was presented to a
family friend - a physicist working in reactor design - to
explain. He gave a little chuckle and said "a complicated
way of solving a perfectly solved problem! There's plenty
of careers in that. If you water-cool the transformers,
you'll actually get within 10% of a normal heater".
|//A normal resistance heater will achieve 100% efficiency
- why use induction or microwave// Hence the chuckle.
At least my idea used the pipes to guide the microwaves
around a house.
|//heating element doesn't have to be in immersed in the
water. A common failure mode of home water heaters is
scale or corrosion building up on the heating elements.//
|The problem isn't because of the heating element being
IN the water, necessarily. The scale derives from the
peculiar way in which carbonates etc. become LESS
soluble in water as temperature rises. You could heat the
water in any way you like and scale will still form.
|There are other problems with corrosion caused by
dissimilar metals and so on which is why water heaters
usually have a sacrificial anode (which no one ever
|//I suppose you can dynamically adjust the power (heat
input to your water) more finely with a microwave
|Microwave or induction, presumably. The microwave we
all use to heat our lunch is an example of a relatively
high-power commercial product, a water heater would
likely be a scale up of that. If it's anything to go by, it has
dreadful fine control. 50% power is just on for 5s, off for
5s. The only induction stove I used was similar, but maybe
in 0.5s pulses.
|I have a heater that is astonishingly precise, it's used to
heat the 100x objective on one of my microscopes, that's
just a little flexible Kapton-insulated resistive heating
element. The key to precision, accuracy & most
importantly, stability, is careful control which we get
from multiple thermistors and a PID controller which
varies Voltage and pulse frequency.
|Getting fine control of heating is so easy with large tanks
of water, water has such thermal capacity & conductivity
that you barely have to try to keep it stable. My 50W
aquarium heater is set at 24C, it's on for hours at a time
before the controller decides the temperature is raised
enough based on the sensor at the other end of the tank.
|Good find [a1] with the heatwayv microwave boiler.
|Some really dubious text about the technology in the FAQ
section of their website:
|Of conventional immersion heaters:
|"there is dissipated volumetric loss that directly affects
thermal efficiency which has to be taken into consideration
when evaluating overall performance. This thermal loss
equates to 1% per radial centimetre from the element
during its heating phase and once temperature is attained
03% loss per radial centimetre during its stand-by reheating
phase. Accordingly, an immersion coil situated in a tank
with a diameter of 450mm (R225mm) would be just over
75% efficient during the high-energy consuming heating
|Of their microwave heater:
|"it fully maximises current resistance in signal generation
and amplification by utilising convected waste heat to
elevate the initial water temperature. Secondly, 100% of
the generated microwave signal is transferred into the
liquid via confined cavities and highly dielectric materials
to reach nominal thermal temperature. Finally, optimal
usage temperature is attained and maintained by latent
heat transfer into the liquid through the use of proprietary
exothermic diffusing insulation."
|A steaming pile of horseshit is what that is.
|There will be an engineer on staff, and they were likely...
motivated.. to come up with that. Poor chap probably
hasn't slept since.
|"Heat pumps are expensive to purchase, are cumbersome
to retrofit requiring the replacement of incumbent
heating systems such as radiators, less responsive in on-
|A huge fridge compressor is no more expensive than a
huge microwave that they're proposing. At least a heat
pump can run on a normal domestic power supply. A
whole-house hot water + heating sized microwave water
heater would definitely require some serious thought on
the electrical supply side. I don't see why a heat pump
couldn't run with radiators and I don't see why it would be
|[bs0u0155]; heat pumps with radiators are definitely a Thing.
|//You could heat the water in any way you like and scale will still form. //
|More easily and cheaply fixed with a microwave heater. Just swap out a short length of pipe.