Top hose / bottom hose
Richard Quinn - 24/8/09 at 02:21 PM
Most, if not all, cars that I have come across take hot water to the rad via the "top hose" and cooled water back to the water pump via the
"bottom hose". Why is it this way round and why not the other? Maybe it is in some cars but I haven't seen any as yet.
tomgregory2000 - 24/8/09 at 02:24 PM
heat rises
Project7 - 24/8/09 at 02:26 PM
Because physics says that the cooler water will be at the bottom.
omega0684 - 24/8/09 at 02:37 PM
and you would have to pump the water upwards against gravity, using up more of the engines created engine = less horses at the wheels!
MikeRJ - 24/8/09 at 02:56 PM
quote:
Originally posted by omega0684
and you would have to pump the water upwards against gravity, using up more of the engines created engine = less horses at the wheels!
In a closed system pressure at the pump inlet will only be a little lower than at it's outlet, so gravity won't have much effect. Just like
a central heating pump, it would never be able to pump water up one or two floors unless it had the pressure of the returning water at it's
inlet.
The reason is that water will naturally circulate upwards through the engine and downwards through the radiator due to the thermosyphon effect; hot
water has a lower density than cold water so will rise to the top of a system if allowed to do so. Similarly the water being cooled in the radiator
falls to the bottom as it's density increases. This gives you a natural flow of water which the pump assists.
It could be connected the other way around, but the pump would be fighting the thermosyphon action
BenB - 24/8/09 at 03:10 PM
Some early engines didn't have pumps at all and just relied on thermosiphon..... (as expertly described above!!).
Mark Allanson - 24/8/09 at 03:24 PM
The main reason is that if the coolant level falls a little, the top hose would only suck air.
britishtrident - 24/8/09 at 06:04 PM
A very very few recent engines have tried to do it the other way round for emission control and fuel efficiency reasons --- here be dragons.