h a l f b a k e r ycarpe demi
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Not a terrible idea, just not a great one either. |
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// replace the water/glycol mix with pool water? // |
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Because that water/glycol mix also contains anticorrosion additives, that's why. |
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Include a coolant/potable water heat exchanger (an off the shelf item for marine use) and it's workable. |
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[+] but, before you have to go out and buy an entire new rear end, recall that water weighs 1tonne/m³. |
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// water weighs 1tonne/m³ // |
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Are you sure about that ? |
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Indeed it was, until the Grand Fleet was dispersed in 1918. |
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//Are you sure about that ?// I think it weighs 1megagram; how much do you think it weighs ? |
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I am sure that there have been Cadillacs with swimming pool on top on TV adverts for years. Surely at least one exists. The adaption of the Radiator heater is brilliant. |
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I've been in a steam-bath in a closet with a radiator!! Not exactly the same thing, but kind of red-neckish. I moved to a rural town many years ago and in the gym-pool area, there was a closet with 2 benchs and a radiator turned up high to make a steam bath! |
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I don't know any of the pertinent figures right off the top of
my head, but it seems like
a standard automotive radiator would take a very long
time to heat that much water. |
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Assume a 130 Hp (100kW) IC powerplant. |
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So, you have 50 kW power available for heating (waste heat). |
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Specific heat of water is 4.2 J/g/K. |
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One tonne of water requires 1000000 x 4.2 Joules to raise its temperature by 1 degree K. |
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Therefore, the temperature of your tonne of water will rise by 1K every 84 seconds. |
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Starting from 10C ambient, a 40 degree temperature rise will take 56 of your Earth minutes. |
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So that's a 130-hp automotive ICE, most likely a V6,
disengaged (in neutral), running in the lower top third of
its power band, so let's say 3,000 rpm +/- 500, for 56 min,
to heat roughly 250 gal from 10C/56F to the typical hot
tub temp of 40C/104F. How much gas will that consume,
gal/ltr per hour? |
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More pertinently, how much _more_ gas will that consume
than a 4hp generator running an electric water heater and
a 100 gal/min (approx. 1.5hp) pump? |
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We need to factor in the body heat of three hot girls sitting the truck bed/pool (link) |
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Not for this part of the math we don't; they won't get in
until it's hot, remember? |
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Most automotive engines only produce their rated output a small fraction of the time, and much of the energy that is wasted in the 50% loss is lost to the exhaust. In this example I can only propose that the exhaust also be passed through a heat exchanger to maximize the total output. |
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Agreed - the numbers in the example were
simply illustrative, not rigorous. |
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Absorbing heat from the exhaust gases makes
a lot of sense as a lot of useful hot water is
condensed, which can be used to top up the
pool. |
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Since this is supposed to be a redneck contraption, why not
just run the exaust pipes right through the tub? Put the cat
and muffler in there, too. Careful where you put your feet! |
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That would pretty much render the cat useless. |
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Of course, most cats are. |
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Also, a 100kW engine is rated for output, ie after the efficiency is calculated. |
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So, an engine with 100kW of chemical energy going into it will output ~30% as available power, ie be rated as a 30kW engine. |
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Soo, your 100kW rated engine is more like a 200kW heater with 100kW flywheel power. Consider a 50/50 split from exhaust heat to radiator heat and you have 100kW avaialble for heating. As has been suggested, put in an exhaust heat exchanger and you double your avilable heating power. |
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Lastly, at <<100% rated power, your engine will most likely be even more innefficient - at 15kW flywheel output, the nominally 100kW engine might be as low as 20% efficient - meaning there's still 60kW in available heating between radiator and exhaust. |
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Any generator setup will be less efficient (chemical -> electrical heating) than this, unless it uses a novel, highly efficient generator. Electrical heating is close to unity for converting electrical energy to heat energy, but only the flywheel power is available to the alternator, which is itself well shy of 100% efficient. |
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<sorry, edited for clarity just after posting> |
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I meant cat as in catalytic converter. They get wicked hot,
what with all the converting going on. |
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Although, now that I think about it it occurs that you
probably knew what I meant and were being clever. |
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Never mind, it was worth a try. |
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<fishes in prototype pool for lifeless mass of
bedraggled fur> |
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Catalytic converters need to be hot to work
efficiently. Cooling them with a water jacket
will render them ineffective. |
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Yeah, their conversion curve looks pretty much like a hockey stick. Below a certain temp they don't do a darn thing. If you could heat up your catalytic converter instantly while your engine was still warming up, you'd take a monster bite out of global emissions. |
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// If you could heat up your catalytic converter instantly ... you'd take a monster bite out of global emissions // |
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Why bother ? You're all going to die anyway when that inbound asteroid arrives ... |
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Oh, ye of little faith... You've seen my rhinoceros, plan,
haven't you? Shirley, it cannot fail. |
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//We need to factor in the body heat of three hot
girls sitting the truck bed/pool// |
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That doesn't count in your cost calculations if all
three girls in the pool are your daughters, right? |
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