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Hey guys, I have been working on making a desalination project using a heatpump to boil water... and I remembered how some on this forum were using electric heaters to warm thier blocks for improved MPG...

Heat pumps are 5, 8, sometimes more efficient at creating heat than straight electric heat.

But, where would one put the condenser? best place would be to somehow circulate the coolant acrost the heat pump then back into the car but since the thermostat won't open until ~180deg, that's difficult.
It could be coiled around the bottum of the motor... but that increases the chances of a leak in the heat pump's system.

Any thoughts?
 

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A heat pump can provide additional heating only by transferring energy from one place to another. Hence, a heatpump would be more efficient than an electric heater only if a source of ample heat were available.

Although a heat pump CAN extract energy from a source cooler than the location being heated, it's output is limited in this scenario. The heat pumping capacity of a heat pump is lesser the greater the difference in temperatures. With a difference of about 30 degrees Celcius, a typical household heat pump transfers aboyut twice as much energy as it uses itself. (Including the heat that it produces from resistance)

However, various "real-life" limitations limit the heat transferring ability to about 165% efficiency. (as compared to a straight heater.) In an engine heating environment, however, the temperature difference is quite large - in the winter it could be 100 degrees Celcius or more. For these reasons I don't think that a heat pump would give good results in this application, especially considering the added cost and complexity that you would add to the system.
 

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oem block heater

Guys, Honda sells a $50 block heater that takes the place of the coolant drain plug, draws 400 watts( i think) and in a few hours has the engine warm. Leave the temp control at 60 degrees to force the coolant valve closed before you shut down for the night,and you my friends will have an engine that could out last you. Use sysn.oil too.
 

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All Canadian Insights have a block heater from the factory. Regardless, The block heater is probrably not designed to get up to the temperature it would if powered while the engine was running.
 

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What? :shock: Better look for mine!
 

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The block heater is fine if your goal is to get easier starting in cold weather. If your goal is to get higher MPG, it's not worth it. You might use 1 kWh heating up the engine with the block heater. That's the energy in about 1/40th gallon of gas, but the power plant is not 100% efficent--so you've used the equivalent of about .075 gallons of gas. Compare that to what you save. Suppose it means you get 40 mpg for the first five miles without the heater, and 70 mpg with it. That's 0.05 gallons saved. So, but that estimate, you are burning more fossil fuel than you save.

Hence the inerest in a heat pump. A good option for cold climates is a "ground source" heat pump that pumps heat out of the ground (obtained through buried pipes). In space heating application they can get COP of 3 to 5, much better than the 1.65 someone quoted.

It's still questionable whether that's worth it, vs. heating the engine with the free waste heat it generates, but with the ground source, at least you've got a shot at making it worthwhile.

Charlie
 

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I use the block heater for max engine life. The engine is noticably quieter on cold mornings. Cold starts are hard on an engine.
 

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The small displacement, and aluminum block, make the enging run cooler in winter, as the cold air cools the block, faster than the waste heat can heat it, thus the improved MPG with the hot air mod.Ever try to idle the car on a real cold day to warm it up? It don't work.
Why not insulate the block, with some spray on foam? The radiator would stop the temp from getting too hot.
Will have to wait a few more months to get into the winter experiments.
I can wait! :wink:
 

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The cost of using a block heater ?? The joy of driving away in the morning with immediate heat and a quiet happy engine-- priceless.

Yeah, insulating the block / head to keep heat in is a great idea.
May not be so great to look at but who cares. quieter too.
Foam wrap on the heater hose too.

Big trucks and piston airplanes do it for engine life, but having heat right away can't be beat. Try it you'll like it.
 
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