Half a croissant, on a plate, with a sign in front of it saying '50c'
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Radiator Jacuzzi

Redneck Luxury
  (+5, -1)
(+5, -1)
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A rich redneck might want a hot tub in the bed of his pickup. There's already a source of heat and plumbing to move it around, so why not run coolant lines to the bed and back and replace the water/glycol mix with pool water? (Something would have to be done with the thermostat.)
kevinthenerd, Jun 14 2012

I guess this is the type of thing you mean... http://www.flickr.c...ro_photo/444470632/
[PainOCommonSense, Jun 15 2012]

Additional temperature modifiers http://www.sporttru..._beds/photo_29.html
[normzone, Jun 15 2012]

[link]






       Not a terrible idea, just not a great one either.
blissmiss, Jun 14 2012
  

       // replace the water/glycol mix with pool water? //   

       Because that water/glycol mix also contains anticorrosion additives, that's why.   

       Include a coolant/potable water heat exchanger (an off the shelf item for marine use) and it's workable.
8th of 7, Jun 14 2012
  

       [+] but, before you have to go out and buy an entire new rear end, recall that water weighs 1tonne/m³.
FlyingToaster, Jun 14 2012
  

       // water weighs 1tonne/m³ //   

       Are you sure about that ?
8th of 7, Jun 14 2012
  

       Indeed it was, until the Grand Fleet was dispersed in 1918.
8th of 7, Jun 14 2012
  

       //Are you sure about that ?// I think it weighs 1megagram; how much do you think it weighs ?
FlyingToaster, Jun 15 2012
  

       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.
PainOCommonSense, Jun 15 2012
  

       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!
xandram, Jun 15 2012
  

       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.
Alterother, Jun 15 2012
  

       Do the math ...   

       Assume a 130 Hp (100kW) IC powerplant.   

       Assume 50% efficiency.   

       So, you have 50 kW power available for heating (waste heat).   

       50kW = 50000 J s-1   

       Specific heat of water is 4.2 J/g/K.   

       One tonne of water requires 1000000 x 4.2 Joules to raise its temperature by 1 degree K.   

       Therefore, the temperature of your tonne of water will rise by 1K every 84 seconds.   

       Starting from 10C ambient, a 40 degree temperature rise will take 56 of your Earth minutes.
8th of 7, Jun 15 2012
  

       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?
Alterother, Jun 15 2012
  

       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?
Alterother, Jun 15 2012
  

       We need to factor in the body heat of three hot girls sitting the truck bed/pool (link)
normzone, Jun 15 2012
  

       Not for this part of the math we don't; they won't get in until it's hot, remember?
Alterother, Jun 15 2012
  

       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.
WcW, Jun 16 2012
  

       Agreed - the numbers in the example were simply illustrative, not rigorous.   

       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.
8th of 7, Jun 16 2012
  

       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!
Alterother, Jun 16 2012
  

       That would pretty much render the cat useless.   

       Of course, most cats are.
RayfordSteele, Jun 17 2012
  

       Also, a 100kW engine is rated for output, ie after the efficiency is calculated.   

       So, an engine with 100kW of chemical energy going into it will output ~30% as available power, ie be rated as a 30kW engine.   

       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.   

       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.   

       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.   

       <sorry, edited for clarity just after posting>
Custardguts, Jun 18 2012
  

       I meant cat as in catalytic converter. They get wicked hot, what with all the converting going on.   

       Although, now that I think about it it occurs that you probably knew what I meant and were being clever.   

       Carry on.
Alterother, Jun 18 2012
  

       Oh.   

       Never mind, it was worth a try.   

       <fishes in prototype pool for lifeless mass of bedraggled fur>   

       Catalytic converters need to be hot to work efficiently. Cooling them with a water jacket will render them ineffective.
8th of 7, Jun 18 2012
  

       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.
RayfordSteele, Jun 18 2012
  

       Eeeen-teresting...
Alterother, Jun 18 2012
  

       // If you could heat up your catalytic converter instantly ... you'd take a monster bite out of global emissions //   

       Why bother ? You're all going to die anyway when that inbound asteroid arrives ...
8th of 7, Jun 18 2012
  

       Oh, ye of little faith... You've seen my rhinoceros, plan, haven't you? Shirley, it cannot fail.
Alterother, Jun 18 2012
  

       //We need to factor in the body heat of three hot girls sitting the truck bed/pool//   

       That doesn't count in your cost calculations if all three girls in the pool are your daughters, right?
UnaBubba, Jun 18 2012
  
      
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