No I don't think so. That wouldn't really work. I'll say again, the water does not need to be hotter. If the engine is 80 and the water out of the tap is 60 then there is loss of course. But if the engine has cooled to 40 passing it round twice won't make it any more than 40. Well that would still be hot enough, but when the engine is 20 - it's colder than tap water from the mains. And what I am saying is that if you fancied a shower in the evening long after pulling over, the engine is cold. You can't create heat energy from nothing.
The piping involved would be significant. too. I'd have to circulate the water without drawing any off. That doesn't work. Not without having a storage tank. Nope too complicated. In answer to Tim, I do not have any trouble at all getting heat to the exchanger. It's scorching. The electric pump is circulating water from the engine through the unit. Cold is then drawn over the element and comes out of the tap. If I stop the tap momentarily then open it again, after a few seconds the water that has paused in the HE comes out and it's nearly boiling. So the exchange process works a treat. But what I am saying is that the engine cools so quickly that its no longer hot. Passing that round a dozen times won't make any difference. A cold engine is a cold engine. The engine is a massive thermal lump and radiates heat in all directions. Look at how long it takes to heat up in the first place. The idea is to have a hot and cold feed. You set the output temp by adding cold water to the hot. But as the temp is perfect for everything at its hottest, there will never be the need to add cold. So that's why I don't have it set up as Tim probably suggests.
It's not a case as he suggests that the engine is hot but it's not sending hot water to the exchanger, that's what the pump is for but once the engine cools and the thermostat shuts there is limited circulation. Leave the engine running and you can have hot water all day. But that's not what I wanted. If there wasn't a thermostat in there it might make a difference. What I don't know is, when the stat is shut, how much circulation of water is there around the block? Does it sit there like a jacket gradually warming up with the water pump just spinning, or does it move. If the water doesn't circulate until the stat opens then it's never going to work for that long. once you switch the engine off. And that may be the issue. My rad is very effective. I had it custom cored. When the engine is off and the electric pump is running, it pushes water around the engine including the radiator. So how long is the engine going to stay hot with an aux cooling system running. See the point? I bet if I could bypass the rad it wouldn't cool nearly so fast.
The piping involved would be significant. too. I'd have to circulate the water without drawing any off. That doesn't work. Not without having a storage tank. Nope too complicated. In answer to Tim, I do not have any trouble at all getting heat to the exchanger. It's scorching. The electric pump is circulating water from the engine through the unit. Cold is then drawn over the element and comes out of the tap. If I stop the tap momentarily then open it again, after a few seconds the water that has paused in the HE comes out and it's nearly boiling. So the exchange process works a treat. But what I am saying is that the engine cools so quickly that its no longer hot. Passing that round a dozen times won't make any difference. A cold engine is a cold engine. The engine is a massive thermal lump and radiates heat in all directions. Look at how long it takes to heat up in the first place. The idea is to have a hot and cold feed. You set the output temp by adding cold water to the hot. But as the temp is perfect for everything at its hottest, there will never be the need to add cold. So that's why I don't have it set up as Tim probably suggests.
It's not a case as he suggests that the engine is hot but it's not sending hot water to the exchanger, that's what the pump is for but once the engine cools and the thermostat shuts there is limited circulation. Leave the engine running and you can have hot water all day. But that's not what I wanted. If there wasn't a thermostat in there it might make a difference. What I don't know is, when the stat is shut, how much circulation of water is there around the block? Does it sit there like a jacket gradually warming up with the water pump just spinning, or does it move. If the water doesn't circulate until the stat opens then it's never going to work for that long. once you switch the engine off. And that may be the issue. My rad is very effective. I had it custom cored. When the engine is off and the electric pump is running, it pushes water around the engine including the radiator. So how long is the engine going to stay hot with an aux cooling system running. See the point? I bet if I could bypass the rad it wouldn't cool nearly so fast.