radiator caps, cooling system pressure

"Guv Bob" > wrote in message
m...
"MLD" > wrote in message ...
>
> > wrote in message
> ...
> > On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
> > > wrote:
> >
> >>On Apr 21, 6:11 pm, Tony Hwang > wrote:
> >>> Ashton Crusher wrote:
> >>> > I was thinking of putting a higher pressure cap on one of my cars to
> >>> > increase the factor of safety against boiling. Looking thru the web
> >>> > for info on the likelihood of changing from 7 psi to 13 psi causing
> >>> > leaks I found little on that issue but did find a couple references
> >>> > to
> >>> > the pressures created by the water pump. One site boasts of a 19
> >>> > PSI,
> >>> > $25 cap to get you thru your "hard driving".
> >>> >http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
> >>> > Thought I'd see if anyone else has heard of this. The claim was that
> >>> > the water pump could create over 30 PSI of pressure. Since that is
> >>> > double the normal operating pressure of most modern cars I find it
> >>> > hard to believe. If the system was at full 15 psi of pressure while
> >>> > the car is idling and then your floored it and ran it up to near
> >>> > redline and created another 30psi of additional pump pressure, or
> >>> > even 10 psi of additioingnal pressure downstream at the radiator
> >>> > cap,
> >>> > you
> >>> > would immediately cause the system to have to vent to the overflow
> >>> > to
> >>> > relieve this higher pressure. I've never seen a car vent due to me
> >>> > revving the engine up while I'm working on it. Thoughts?????
> >>>
> >>> Hi.
> >>> There is a over flow bottle for coolant/anti-freeze. Ever
> >>> cleaned/flushed your rad. and maintain proper level of
> >>> coolant/anti-freeze in your rad.? If the car is old, messing with cap
> >>> can spring
> >>> a leak.- Hide quoted text -
> >>>
> >>> - Show quoted text -
> >>
> >>AMEN!
> > A water pump cannot produce system pressure because it just moves
> > water from one side of the pump to the other. Expansion due to heat is
> > what builds pressure..
>
> I guess you need to know how a centrifugal pump works. Pressure rise
> across the pump is function of the square of its speed. Double the pump
> speed and the delta P across the pump increases 4X. Expansion due to
> heat
> will increase system pressure if it is in a closed system. If a fluid can
> expand without being constrained---no significant change in pressure.
> MLD

Well, I give each of you half credit. LOL! At a certain RPM, the pump head
(outlet-inlet pressure) and flow rate are both are fairly indept of the
coolant temperature as long as the coolant stays a liquid (normal condition)
when going through the pump. The engine heat raises the coolant temperature
and the pressure (remember this from skool... PV=nRT), but (and this is a
big butt) as long as the pump turns at the same RPM, the head should stay
about the same.

FWIW, here's a decent drawing of a water pump cross-section
http://assets.hemmings.com/story_image/83720-500-0.jpg

A couple of comments--PV=nRT is an equation used in gas flow calculations
not when the fluid is a liquid. Don't understand where you are coming from.
Just for the record, at constant speed the pressure rise across a
centrifugal pump does not remain constant. Typically, there is a droop
(loss of delta P) as the pump flow demand increases. Relatively
insignificant at first but if the flow demand gets large enough, then the
Pump Delta P can drop significantly. Flow demand is dictated by the
characteristics of the the system in question--that is, how the delta P vs
Flow of the system (line losses etc.) matches up with the delta P vs flow of
the pump. Where the two intersect will be the operating point of the
System. The idea is to match them so that the intersection takes place
where the droop in pump deta P is relatively insensitive to flow demand.
MLD

On 5/1/2014 9:39 AM, MLD wrote:
>
> "Guv Bob" > wrote in message
> m...
> "MLD" > wrote in message ...
>>
>> > wrote in message
>> ...
>> > On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
>> > > wrote:
>> >
>> >>On Apr 21, 6:11 pm, Tony Hwang > wrote:
>> >>> Ashton Crusher wrote:
>> >>> > I was thinking of putting a higher pressure cap on one of my
>> cars to
>> >>> > increase the factor of safety against boiling. Looking thru the web
>> >>> > for info on the likelihood of changing from 7 psi to 13 psi causing
>> >>> > leaks I found little on that issue but did find a couple
>> references >>> > to
>> >>> > the pressures created by the water pump. One site boasts of a 19
>> >>> > PSI,
>> >>> > $25 cap to get you thru your "hard driving".
>> >>>
>> >http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>> >>> > Thought I'd see if anyone else has heard of this. The claim was
>> that
>> >>> > the water pump could create over 30 PSI of pressure. Since that is
>> >>> > double the normal operating pressure of most modern cars I find it
>> >>> > hard to believe. If the system was at full 15 psi of pressure while
>> >>> > the car is idling and then your floored it and ran it up to near
>> >>> > redline and created another 30psi of additional pump pressure, or
>> >>> > even 10 psi of additioingnal pressure downstream at the radiator
>> >>> > cap,
>> >>> > you
>> >>> > would immediately cause the system to have to vent to the
>> overflow >>> > to
>> >>> > relieve this higher pressure. I've never seen a car vent due to me
>> >>> > revving the engine up while I'm working on it. Thoughts?????
>> >>>
>> >>> Hi.
>> >>> There is a over flow bottle for coolant/anti-freeze. Ever
>> >>> cleaned/flushed your rad. and maintain proper level of
>> >>> coolant/anti-freeze in your rad.? If the car is old, messing with cap
>> >>> can spring
>> >>> a leak.- Hide quoted text -
>> >>>
>> >>> - Show quoted text -
>> >>
>> >>AMEN!
>> > A water pump cannot produce system pressure because it just moves
>> > water from one side of the pump to the other. Expansion due to heat is
>> > what builds pressure..
>>
>> I guess you need to know how a centrifugal pump works. Pressure rise
>> across the pump is function of the square of its speed. Double the pump
>> speed and the delta P across the pump increases 4X. Expansion due to
>> heat
>> will increase system pressure if it is in a closed system. If a fluid
>> can
>> expand without being constrained---no significant change in pressure.
>> MLD
>
> Well, I give each of you half credit. LOL! At a certain RPM, the pump
> head (outlet-inlet pressure) and flow rate are both are fairly indept of
> the coolant temperature as long as the coolant stays a liquid (normal
> condition) when going through the pump. The engine heat raises the
> coolant temperature and the pressure (remember this from skool...
> PV=nRT), but (and this is a big butt) as long as the pump turns at the
> same RPM, the head should stay about the same.
>
> FWIW, here's a decent drawing of a water pump cross-section
> http://assets.hemmings.com/story_image/83720-500-0.jpg
>
> A couple of comments--PV=nRT is an equation used in gas flow
> calculations not when the fluid is a liquid. Don't understand where you
> are coming from. Just for the record, at constant speed the pressure
> rise across a centrifugal pump does not remain constant. Typically,
> there is a droop (loss of delta P) as the pump flow demand increases.
> Relatively insignificant at first but if the flow demand gets large
> enough, then the Pump Delta P can drop significantly. Flow demand is
> dictated by the characteristics of the the system in question--that is,
> how the delta P vs Flow of the system (line losses etc.) matches up with
> the delta P vs flow of the pump. Where the two intersect will be the
> operating point of the System. The idea is to match them so that the
> intersection takes place where the droop in pump deta P is relatively
> insensitive to flow demand.
> MLD
>
Riddle me this.
In a CLOSED system FILLED with INCOMPRESSIBLE liquid, the pressure is
whatever
the pressure is.
The pump can't put more pressure on the output side than is on the input
side because it's a CLOSED system FILLED with INCOMPRESSIBLE liquid.

Do pump principles applied to OPEN systems really apply?

On Thu, 01 May 2014 12:59:51 -0700, mike > wrote:

>On 5/1/2014 9:39 AM, MLD wrote:
>>
>> "Guv Bob" > wrote in message
>> m...
>> "MLD" > wrote in message ...
>>>
>>> > wrote in message
>>> ...
>>> > On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
>>> > > wrote:
>>> >
>>> >>On Apr 21, 6:11 pm, Tony Hwang > wrote:
>>> >>> Ashton Crusher wrote:
>>> >>> > I was thinking of putting a higher pressure cap on one of my
>>> cars to
>>> >>> > increase the factor of safety against boiling. Looking thru the web
>>> >>> > for info on the likelihood of changing from 7 psi to 13 psi causing
>>> >>> > leaks I found little on that issue but did find a couple
>>> references >>> > to
>>> >>> > the pressures created by the water pump. One site boasts of a 19
>>> >>> > PSI,
>>> >>> > $25 cap to get you thru your "hard driving".
>>> >>>
>>> >http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>>> >>> > Thought I'd see if anyone else has heard of this. The claim was
>>> that
>>> >>> > the water pump could create over 30 PSI of pressure. Since that is
>>> >>> > double the normal operating pressure of most modern cars I find it
>>> >>> > hard to believe. If the system was at full 15 psi of pressure while
>>> >>> > the car is idling and then your floored it and ran it up to near
>>> >>> > redline and created another 30psi of additional pump pressure, or
>>> >>> > even 10 psi of additioingnal pressure downstream at the radiator
>>> >>> > cap,
>>> >>> > you
>>> >>> > would immediately cause the system to have to vent to the
>>> overflow >>> > to
>>> >>> > relieve this higher pressure. I've never seen a car vent due to me
>>> >>> > revving the engine up while I'm working on it. Thoughts?????
>>> >>>
>>> >>> Hi.
>>> >>> There is a over flow bottle for coolant/anti-freeze. Ever
>>> >>> cleaned/flushed your rad. and maintain proper level of
>>> >>> coolant/anti-freeze in your rad.? If the car is old, messing with cap
>>> >>> can spring
>>> >>> a leak.- Hide quoted text -
>>> >>>
>>> >>> - Show quoted text -
>>> >>
>>> >>AMEN!
>>> > A water pump cannot produce system pressure because it just moves
>>> > water from one side of the pump to the other. Expansion due to heat is
>>> > what builds pressure..
>>>
>>> I guess you need to know how a centrifugal pump works. Pressure rise
>>> across the pump is function of the square of its speed. Double the pump
>>> speed and the delta P across the pump increases 4X. Expansion due to
>>> heat
>>> will increase system pressure if it is in a closed system. If a fluid
>>> can
>>> expand without being constrained---no significant change in pressure.
>>> MLD
>>
>> Well, I give each of you half credit. LOL! At a certain RPM, the pump
>> head (outlet-inlet pressure) and flow rate are both are fairly indept of
>> the coolant temperature as long as the coolant stays a liquid (normal
>> condition) when going through the pump. The engine heat raises the
>> coolant temperature and the pressure (remember this from skool...
>> PV=nRT), but (and this is a big butt) as long as the pump turns at the
>> same RPM, the head should stay about the same.
>>
>> FWIW, here's a decent drawing of a water pump cross-section
>> http://assets.hemmings.com/story_image/83720-500-0.jpg
>>
>> A couple of comments--PV=nRT is an equation used in gas flow
>> calculations not when the fluid is a liquid. Don't understand where you
>> are coming from. Just for the record, at constant speed the pressure
>> rise across a centrifugal pump does not remain constant. Typically,
>> there is a droop (loss of delta P) as the pump flow demand increases.
>> Relatively insignificant at first but if the flow demand gets large
>> enough, then the Pump Delta P can drop significantly. Flow demand is
>> dictated by the characteristics of the the system in question--that is,
>> how the delta P vs Flow of the system (line losses etc.) matches up with
>> the delta P vs flow of the pump. Where the two intersect will be the
>> operating point of the System. The idea is to match them so that the
>> intersection takes place where the droop in pump deta P is relatively
>> insensitive to flow demand.
>> MLD
>>
>Riddle me this.
>In a CLOSED system FILLED with INCOMPRESSIBLE liquid, the pressure is
>whatever
>the pressure is.
>The pump can't put more pressure on the output side than is on the input
>side because it's a CLOSED system FILLED with INCOMPRESSIBLE liquid.
>
>Do pump principles applied to OPEN systems really apply?


Great Question. My original question remains unanswered .... Does the
water pump ADD another 10 to 30 psi internal pressure (as the sources
I originally was looking at claimed) and if it does, how come that
extra pressure, on top of the already existing 12 psi heat pressure,
not cause the cap to blow off from the excess pressure now totaling
from 20 to 40 psi? All I can think is that the pump only adds perhaps
2 to 5 psi and that by the time it "gets" to the cap area, flow
resistance has dissipated it down to 1 or 2 psi and it has ceased to
be a problem. Or maybe the pump only "adds" negative pressure, i.e.
suction at the inlet, or some combo of all that.

"mike" > wrote in message
...
> On 5/1/2014 9:39 AM, MLD wrote:
>>
>> "Guv Bob" > wrote in message
>> m...
>> "MLD" > wrote in message
>> ...
>>>
>>> > wrote in message
>>> ...
>>> > On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
>>> > > wrote:
>>> >
>>> >>On Apr 21, 6:11 pm, Tony Hwang > wrote:
>>> >>> Ashton Crusher wrote:
>>> >>> > I was thinking of putting a higher pressure cap on one of my
>>> cars to
>>> >>> > increase the factor of safety against boiling. Looking thru the
>>> >>> > web
>>> >>> > for info on the likelihood of changing from 7 psi to 13 psi
>>> >>> > causing
>>> >>> > leaks I found little on that issue but did find a couple
>>> references >>> > to
>>> >>> > the pressures created by the water pump. One site boasts of a 19
>>> >>> > PSI,
>>> >>> > $25 cap to get you thru your "hard driving".
>>> >>>
>>> >http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>>> >>> > Thought I'd see if anyone else has heard of this. The claim was
>>> that
>>> >>> > the water pump could create over 30 PSI of pressure. Since that is
>>> >>> > double the normal operating pressure of most modern cars I find it
>>> >>> > hard to believe. If the system was at full 15 psi of pressure
>>> >>> > while
>>> >>> > the car is idling and then your floored it and ran it up to near
>>> >>> > redline and created another 30psi of additional pump pressure, or
>>> >>> > even 10 psi of additioingnal pressure downstream at the radiator
>>> >>> > cap,
>>> >>> > you
>>> >>> > would immediately cause the system to have to vent to the
>>> overflow >>> > to
>>> >>> > relieve this higher pressure. I've never seen a car vent due to me
>>> >>> > revving the engine up while I'm working on it. Thoughts?????
>>> >>>
>>> >>> Hi.
>>> >>> There is a over flow bottle for coolant/anti-freeze. Ever
>>> >>> cleaned/flushed your rad. and maintain proper level of
>>> >>> coolant/anti-freeze in your rad.? If the car is old, messing with
>>> >>> cap
>>> >>> can spring
>>> >>> a leak.- Hide quoted text -
>>> >>>
>>> >>> - Show quoted text -
>>> >>
>>> >>AMEN!
>>> > A water pump cannot produce system pressure because it just moves
>>> > water from one side of the pump to the other. Expansion due to heat is
>>> > what builds pressure..
>>>
>>> I guess you need to know how a centrifugal pump works. Pressure rise
>>> across the pump is function of the square of its speed. Double the pump
>>> speed and the delta P across the pump increases 4X. Expansion due to
>>> heat
>>> will increase system pressure if it is in a closed system. If a fluid
>>> can
>>> expand without being constrained---no significant change in pressure.
>>> MLD
>>
>> Well, I give each of you half credit. LOL! At a certain RPM, the pump
>> head (outlet-inlet pressure) and flow rate are both are fairly indept of
>> the coolant temperature as long as the coolant stays a liquid (normal
>> condition) when going through the pump. The engine heat raises the
>> coolant temperature and the pressure (remember this from skool...
>> PV=nRT), but (and this is a big butt) as long as the pump turns at the
>> same RPM, the head should stay about the same.
>>
>> FWIW, here's a decent drawing of a water pump cross-section
>> http://assets.hemmings.com/story_image/83720-500-0.jpg
>>
>> A couple of comments--PV=nRT is an equation used in gas flow
>> calculations not when the fluid is a liquid. Don't understand where you
>> are coming from. Just for the record, at constant speed the pressure
>> rise across a centrifugal pump does not remain constant. Typically,
>> there is a droop (loss of delta P) as the pump flow demand increases.
>> Relatively insignificant at first but if the flow demand gets large
>> enough, then the Pump Delta P can drop significantly. Flow demand is
>> dictated by the characteristics of the the system in question--that is,
>> how the delta P vs Flow of the system (line losses etc.) matches up with
>> the delta P vs flow of the pump. Where the two intersect will be the
>> operating point of the System. The idea is to match them so that the
>> intersection takes place where the droop in pump deta P is relatively
>> insensitive to flow demand.
>> MLD
>>
> Riddle me this.
> In a CLOSED system FILLED with INCOMPRESSIBLE liquid, the pressure is
> whatever
> the pressure is.
> The pump can't put more pressure on the output side than is on the input
> side because it's a CLOSED system FILLED with INCOMPRESSIBLE liquid.
>
> Do pump principles applied to OPEN systems really apply?

Don't understand either of your comments. Could you expand your
explanations so they make some sense?
Do you know what happens if you dead end a centrifugal pump (Zero flow)
while its running?? The discharge pressure might not change but you better
be prepared to see the fluid temperature skyrocket.
You seem to to make a big point out of INCOMPRESSIBLE fluid. Got some news
for you, Ready---fluids, aka liquids, are not INCOMPRESSIBLE!!! Have you
ever heard of "Bulk Modulus", entrained air or compressible flow as they
apply to liquids?
Do you know what would happen to the pressure in a closed system if the
fluid temperature (say water) was increased but the fluid was not able to
expand due to the closed (or fixed) system volume?
Hint: Delta P=(BM) x (Delta V)/V
Clue: Pressure can increase up to the thousands! Want to try and conduct
your own experiment? Close the water inlet shut off valve in your house.
Keep all faucets closed and of course, lock the hot water tank relief valve
so that it doesn't open. Now just crank up the temperature of your water
heater. This ought to seek out your system's weak link.
MLD

On 5/1/2014 4:36 PM, Ashton Crusher wrote:
> On Thu, 01 May 2014 12:59:51 -0700, mike > wrote:
>
>> On 5/1/2014 9:39 AM, MLD wrote:
>>>
>>> "Guv Bob" > wrote in message
>>> m...
>>> "MLD" > wrote in message ...
>>>>
>>>> > wrote in message
>>>> ...
>>>>> On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
>>>>> > wrote:
>>>>>
>>>>>> On Apr 21, 6:11 pm, Tony Hwang > wrote:
>>>>>>> Ashton Crusher wrote:
>>>>>>>> I was thinking of putting a higher pressure cap on one of my
>>>> cars to
>>>>>>>> increase the factor of safety against boiling. Looking thru the web
>>>>>>>> for info on the likelihood of changing from 7 psi to 13 psi causing
>>>>>>>> leaks I found little on that issue but did find a couple
>>>> references >>> > to
>>>>>>>> the pressures created by the water pump. One site boasts of a 19
>>>>>>>> PSI,
>>>>>>>> $25 cap to get you thru your "hard driving".
>>>>>>>
>>>>> http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>>>>>>>> Thought I'd see if anyone else has heard of this. The claim was
>>>> that
>>>>>>>> the water pump could create over 30 PSI of pressure. Since that is
>>>>>>>> double the normal operating pressure of most modern cars I find it
>>>>>>>> hard to believe. If the system was at full 15 psi of pressure while
>>>>>>>> the car is idling and then your floored it and ran it up to near
>>>>>>>> redline and created another 30psi of additional pump pressure, or
>>>>>>>> even 10 psi of additioingnal pressure downstream at the radiator
>>>>>>>> cap,
>>>>>>>> you
>>>>>>>> would immediately cause the system to have to vent to the
>>>> overflow >>> > to
>>>>>>>> relieve this higher pressure. I've never seen a car vent due to me
>>>>>>>> revving the engine up while I'm working on it. Thoughts?????
>>>>>>>
>>>>>>> Hi.
>>>>>>> There is a over flow bottle for coolant/anti-freeze. Ever
>>>>>>> cleaned/flushed your rad. and maintain proper level of
>>>>>>> coolant/anti-freeze in your rad.? If the car is old, messing with cap
>>>>>>> can spring
>>>>>>> a leak.- Hide quoted text -
>>>>>>>
>>>>>>> - Show quoted text -
>>>>>>
>>>>>> AMEN!
>>>>> A water pump cannot produce system pressure because it just moves
>>>>> water from one side of the pump to the other. Expansion due to heat is
>>>>> what builds pressure..
>>>>
>>>> I guess you need to know how a centrifugal pump works. Pressure rise
>>>> across the pump is function of the square of its speed. Double the pump
>>>> speed and the delta P across the pump increases 4X. Expansion due to
>>>> heat
>>>> will increase system pressure if it is in a closed system. If a fluid
>>>> can
>>>> expand without being constrained---no significant change in pressure.
>>>> MLD
>>>
>>> Well, I give each of you half credit. LOL! At a certain RPM, the pump
>>> head (outlet-inlet pressure) and flow rate are both are fairly indept of
>>> the coolant temperature as long as the coolant stays a liquid (normal
>>> condition) when going through the pump. The engine heat raises the
>>> coolant temperature and the pressure (remember this from skool...
>>> PV=nRT), but (and this is a big butt) as long as the pump turns at the
>>> same RPM, the head should stay about the same.
>>>
>>> FWIW, here's a decent drawing of a water pump cross-section
>>> http://assets.hemmings.com/story_image/83720-500-0.jpg
>>>
>>> A couple of comments--PV=nRT is an equation used in gas flow
>>> calculations not when the fluid is a liquid. Don't understand where you
>>> are coming from. Just for the record, at constant speed the pressure
>>> rise across a centrifugal pump does not remain constant. Typically,
>>> there is a droop (loss of delta P) as the pump flow demand increases.
>>> Relatively insignificant at first but if the flow demand gets large
>>> enough, then the Pump Delta P can drop significantly. Flow demand is
>>> dictated by the characteristics of the the system in question--that is,
>>> how the delta P vs Flow of the system (line losses etc.) matches up with
>>> the delta P vs flow of the pump. Where the two intersect will be the
>>> operating point of the System. The idea is to match them so that the
>>> intersection takes place where the droop in pump deta P is relatively
>>> insensitive to flow demand.
>>> MLD
>>>
>> Riddle me this.
>> In a CLOSED system FILLED with INCOMPRESSIBLE liquid, the pressure is
>> whatever
>> the pressure is.
>> The pump can't put more pressure on the output side than is on the input
>> side because it's a CLOSED system FILLED with INCOMPRESSIBLE liquid.
>>
>> Do pump principles applied to OPEN systems really apply?
>
>
> Great Question. My original question remains unanswered .... Does the
> water pump ADD another 10 to 30 psi internal pressure (as the sources
> I originally was looking at claimed) and if it does, how come that
> extra pressure, on top of the already existing 12 psi heat pressure,
> not cause the cap to blow off from the excess pressure now totaling
> from 20 to 40 psi? All I can think is that the pump only adds perhaps
> 2 to 5 psi and that by the time it "gets" to the cap area, flow
> resistance has dissipated it down to 1 or 2 psi and it has ceased to
> be a problem. Or maybe the pump only "adds" negative pressure, i.e.
> suction at the inlet, or some combo of all that.
>
It's my contention that the pump can add no pressure unless it has
somewhere to get the water to pump.
If it's coming from the closed system, there ain't none available
unless you vaporize some on the source side.

On 5/1/2014 4:46 PM, MLD wrote:
>
> "mike" > wrote in message
> ...
>> On 5/1/2014 9:39 AM, MLD wrote:
>>>
>>> "Guv Bob" > wrote in message
>>> m...
>>> "MLD" > wrote in message
>>> ...
>>>>
>>>> > wrote in message
>>>> ...
>>>> > On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
>>>> > > wrote:
>>>> >
>>>> >>On Apr 21, 6:11 pm, Tony Hwang > wrote:
>>>> >>> Ashton Crusher wrote:
>>>> >>> > I was thinking of putting a higher pressure cap on one of my
>>>> cars to
>>>> >>> > increase the factor of safety against boiling. Looking thru
>>>> the >>> > web
>>>> >>> > for info on the likelihood of changing from 7 psi to 13 psi
>>>> >>> > causing
>>>> >>> > leaks I found little on that issue but did find a couple
>>>> references >>> > to
>>>> >>> > the pressures created by the water pump. One site boasts of a 19
>>>> >>> > PSI,
>>>> >>> > $25 cap to get you thru your "hard driving".
>>>> >>>
>>>> >http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>>>>
>>>> >>> > Thought I'd see if anyone else has heard of this. The claim was
>>>> that
>>>> >>> > the water pump could create over 30 PSI of pressure. Since
>>>> that is
>>>> >>> > double the normal operating pressure of most modern cars I
>>>> find it
>>>> >>> > hard to believe. If the system was at full 15 psi of pressure
>>>> >>> > while
>>>> >>> > the car is idling and then your floored it and ran it up to near
>>>> >>> > redline and created another 30psi of additional pump pressure, or
>>>> >>> > even 10 psi of additioingnal pressure downstream at the radiator
>>>> >>> > cap,
>>>> >>> > you
>>>> >>> > would immediately cause the system to have to vent to the
>>>> overflow >>> > to
>>>> >>> > relieve this higher pressure. I've never seen a car vent due
>>>> to me
>>>> >>> > revving the engine up while I'm working on it. Thoughts?????
>>>> >>>
>>>> >>> Hi.
>>>> >>> There is a over flow bottle for coolant/anti-freeze. Ever
>>>> >>> cleaned/flushed your rad. and maintain proper level of
>>>> >>> coolant/anti-freeze in your rad.? If the car is old, messing
>>>> with >>> cap
>>>> >>> can spring
>>>> >>> a leak.- Hide quoted text -
>>>> >>>
>>>> >>> - Show quoted text -
>>>> >>
>>>> >>AMEN!
>>>> > A water pump cannot produce system pressure because it just moves
>>>> > water from one side of the pump to the other. Expansion due to
>>>> heat is
>>>> > what builds pressure..
>>>>
>>>> I guess you need to know how a centrifugal pump works. Pressure rise
>>>> across the pump is function of the square of its speed. Double the
>>>> pump
>>>> speed and the delta P across the pump increases 4X. Expansion due to
>>>> heat
>>>> will increase system pressure if it is in a closed system. If a fluid
>>>> can
>>>> expand without being constrained---no significant change in pressure.
>>>> MLD
>>>
>>> Well, I give each of you half credit. LOL! At a certain RPM, the pump
>>> head (outlet-inlet pressure) and flow rate are both are fairly indept of
>>> the coolant temperature as long as the coolant stays a liquid (normal
>>> condition) when going through the pump. The engine heat raises the
>>> coolant temperature and the pressure (remember this from skool...
>>> PV=nRT), but (and this is a big butt) as long as the pump turns at the
>>> same RPM, the head should stay about the same.
>>>
>>> FWIW, here's a decent drawing of a water pump cross-section
>>> http://assets.hemmings.com/story_image/83720-500-0.jpg
>>>
>>> A couple of comments--PV=nRT is an equation used in gas flow
>>> calculations not when the fluid is a liquid. Don't understand where you
>>> are coming from. Just for the record, at constant speed the pressure
>>> rise across a centrifugal pump does not remain constant. Typically,
>>> there is a droop (loss of delta P) as the pump flow demand increases.
>>> Relatively insignificant at first but if the flow demand gets large
>>> enough, then the Pump Delta P can drop significantly. Flow demand is
>>> dictated by the characteristics of the the system in question--that is,
>>> how the delta P vs Flow of the system (line losses etc.) matches up with
>>> the delta P vs flow of the pump. Where the two intersect will be the
>>> operating point of the System. The idea is to match them so that the
>>> intersection takes place where the droop in pump deta P is relatively
>>> insensitive to flow demand.
>>> MLD
>>>
>> Riddle me this.
>> In a CLOSED system FILLED with INCOMPRESSIBLE liquid, the pressure is
>> whatever
>> the pressure is.
>> The pump can't put more pressure on the output side than is on the input
>> side because it's a CLOSED system FILLED with INCOMPRESSIBLE liquid.
>>
>> Do pump principles applied to OPEN systems really apply?
>
> Don't understand either of your comments. Could you expand your
> explanations so they make some sense?
> Do you know what happens if you dead end a centrifugal pump (Zero flow)
> while its running?? The discharge pressure might not change but you
> better be prepared to see the fluid temperature skyrocket.
> You seem to to make a big point out of INCOMPRESSIBLE fluid. Got some
> news for you, Ready---fluids, aka liquids, are not INCOMPRESSIBLE!!!
> Have you ever heard of "Bulk Modulus", entrained air or compressible
> flow as they apply to liquids?
> Do you know what would happen to the pressure in a closed system if the
> fluid temperature (say water) was increased but the fluid was not able
> to expand due to the closed (or fixed) system volume?
> Hint: Delta P=(BM) x (Delta V)/V
> Clue: Pressure can increase up to the thousands! Want to try and
> conduct your own experiment? Close the water inlet shut off valve in
> your house. Keep all faucets closed and of course, lock the hot water
> tank relief valve so that it doesn't open. Now just crank up the
> temperature of your water heater. This ought to seek out your system's
> weak link.
> MLD
>
>
Can't argue with your theory. Problem is that it doesn't apply here
in any significant amount.
If the pressure exceeds the cap pressure, it vents.
The pump didn't add the pressure. In your scenario, the pump added
heat.
So, get back to the topic. In a closed car cooling system under normal
operation
can the pressure on the output side of the pump significantly exceed
the pressure on the input side?

I think we can exclude any vaporization of the liquid leading to excess
pressure. If it did, it would vent and, eventually, there'd be no more
liquid to pump.

But thank you for the clue and the hint and the nitpicking.

On Thu, 01 May 2014 17:05:57 -0700, mike > wrote:

>On 5/1/2014 4:36 PM, Ashton Crusher wrote:
>> On Thu, 01 May 2014 12:59:51 -0700, mike > wrote:
>>
>>> On 5/1/2014 9:39 AM, MLD wrote:
>>>>
>>>> "Guv Bob" > wrote in message
>>>> m...
>>>> "MLD" > wrote in message ...
>>>>>
>>>>> > wrote in message
>>>>> ...
>>>>>> On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
>>>>>> > wrote:
>>>>>>
>>>>>>> On Apr 21, 6:11 pm, Tony Hwang > wrote:
>>>>>>>> Ashton Crusher wrote:
>>>>>>>>> I was thinking of putting a higher pressure cap on one of my
>>>>> cars to
>>>>>>>>> increase the factor of safety against boiling. Looking thru the web
>>>>>>>>> for info on the likelihood of changing from 7 psi to 13 psi causing
>>>>>>>>> leaks I found little on that issue but did find a couple
>>>>> references >>> > to
>>>>>>>>> the pressures created by the water pump. One site boasts of a 19
>>>>>>>>> PSI,
>>>>>>>>> $25 cap to get you thru your "hard driving".
>>>>>>>>
>>>>>> http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>>>>>>>>> Thought I'd see if anyone else has heard of this. The claim was
>>>>> that
>>>>>>>>> the water pump could create over 30 PSI of pressure. Since that is
>>>>>>>>> double the normal operating pressure of most modern cars I find it
>>>>>>>>> hard to believe. If the system was at full 15 psi of pressure while
>>>>>>>>> the car is idling and then your floored it and ran it up to near
>>>>>>>>> redline and created another 30psi of additional pump pressure, or
>>>>>>>>> even 10 psi of additioingnal pressure downstream at the radiator
>>>>>>>>> cap,
>>>>>>>>> you
>>>>>>>>> would immediately cause the system to have to vent to the
>>>>> overflow >>> > to
>>>>>>>>> relieve this higher pressure. I've never seen a car vent due to me
>>>>>>>>> revving the engine up while I'm working on it. Thoughts?????
>>>>>>>>
>>>>>>>> Hi.
>>>>>>>> There is a over flow bottle for coolant/anti-freeze. Ever
>>>>>>>> cleaned/flushed your rad. and maintain proper level of
>>>>>>>> coolant/anti-freeze in your rad.? If the car is old, messing with cap
>>>>>>>> can spring
>>>>>>>> a leak.- Hide quoted text -
>>>>>>>>
>>>>>>>> - Show quoted text -
>>>>>>>
>>>>>>> AMEN!
>>>>>> A water pump cannot produce system pressure because it just moves
>>>>>> water from one side of the pump to the other. Expansion due to heat is
>>>>>> what builds pressure..
>>>>>
>>>>> I guess you need to know how a centrifugal pump works. Pressure rise
>>>>> across the pump is function of the square of its speed. Double the pump
>>>>> speed and the delta P across the pump increases 4X. Expansion due to
>>>>> heat
>>>>> will increase system pressure if it is in a closed system. If a fluid
>>>>> can
>>>>> expand without being constrained---no significant change in pressure.
>>>>> MLD
>>>>
>>>> Well, I give each of you half credit. LOL! At a certain RPM, the pump
>>>> head (outlet-inlet pressure) and flow rate are both are fairly indept of
>>>> the coolant temperature as long as the coolant stays a liquid (normal
>>>> condition) when going through the pump. The engine heat raises the
>>>> coolant temperature and the pressure (remember this from skool...
>>>> PV=nRT), but (and this is a big butt) as long as the pump turns at the
>>>> same RPM, the head should stay about the same.
>>>>
>>>> FWIW, here's a decent drawing of a water pump cross-section
>>>> http://assets.hemmings.com/story_image/83720-500-0.jpg
>>>>
>>>> A couple of comments--PV=nRT is an equation used in gas flow
>>>> calculations not when the fluid is a liquid. Don't understand where you
>>>> are coming from. Just for the record, at constant speed the pressure
>>>> rise across a centrifugal pump does not remain constant. Typically,
>>>> there is a droop (loss of delta P) as the pump flow demand increases.
>>>> Relatively insignificant at first but if the flow demand gets large
>>>> enough, then the Pump Delta P can drop significantly. Flow demand is
>>>> dictated by the characteristics of the the system in question--that is,
>>>> how the delta P vs Flow of the system (line losses etc.) matches up with
>>>> the delta P vs flow of the pump. Where the two intersect will be the
>>>> operating point of the System. The idea is to match them so that the
>>>> intersection takes place where the droop in pump deta P is relatively
>>>> insensitive to flow demand.
>>>> MLD
>>>>
>>> Riddle me this.
>>> In a CLOSED system FILLED with INCOMPRESSIBLE liquid, the pressure is
>>> whatever
>>> the pressure is.
>>> The pump can't put more pressure on the output side than is on the input
>>> side because it's a CLOSED system FILLED with INCOMPRESSIBLE liquid.
>>>
>>> Do pump principles applied to OPEN systems really apply?
>>
>>
>> Great Question. My original question remains unanswered .... Does the
>> water pump ADD another 10 to 30 psi internal pressure (as the sources
>> I originally was looking at claimed) and if it does, how come that
>> extra pressure, on top of the already existing 12 psi heat pressure,
>> not cause the cap to blow off from the excess pressure now totaling
>> from 20 to 40 psi? All I can think is that the pump only adds perhaps
>> 2 to 5 psi and that by the time it "gets" to the cap area, flow
>> resistance has dissipated it down to 1 or 2 psi and it has ceased to
>> be a problem. Or maybe the pump only "adds" negative pressure, i.e.
>> suction at the inlet, or some combo of all that.
>>
>It's my contention that the pump can add no pressure unless it has
>somewhere to get the water to pump.
>If it's coming from the closed system, there ain't none available
>unless you vaporize some on the source side.
>
The water pump can develop mabee a couple of pounds pressure on the
outlet side into a plugged rad with the cap off. With the cap on, with
no air in the system, significantly less. But at best, only a pound or
two. Will running the water pump dead headed cause a temp increase?
Sure, a very small amount. Inconsequential compared to the heat output
of the engine. It will NOT cause a pressure increase in the closed
system. The increased pressure increases the boiling point of the
coolant. It also helps get and keep entrained air out of the cooling
fluid. The only thing that causes the pressure rize is temperature.
The pressure reduces back to atmospheric when the temperature drops
back to room temperature. Current production vehicles have a "catch
tank" that holds excess coolant if any is forced out to regulate the
pressure, and it is drawn back in on cooldown.

"mike" > wrote in message
...
> On 5/1/2014 4:46 PM, MLD wrote:


> operation
> can the pressure on the output side of the pump significantly exceed
> the pressure on the input side?



Yes, and it looks like a lot of you have no idea how much it can, and does.

On 5/1/2014 9:08 PM, Rick wrote:
>
> "mike" > wrote in message
> ...
>> On 5/1/2014 4:46 PM, MLD wrote:
>
>
>> operation
>> can the pressure on the output side of the pump significantly exceed
>> the pressure on the input side?
>
>
>
> Yes, and it looks like a lot of you have no idea how much it can, and does.
>
I'd like to hear the rationale in a closed system.

"mike" > wrote in message
...
> On 5/1/2014 9:08 PM, Rick wrote:
>>
>> "mike" > wrote in message
>> ...
>>> On 5/1/2014 4:46 PM, MLD wrote:
>>
>>
>>> operation
>>> can the pressure on the output side of the pump significantly exceed
>>> the pressure on the input side?
>>
>>
>>
>> Yes, and it looks like a lot of you have no idea how much it can, and
>> does.
>>
> I'd like to hear the rationale in a closed system.

Simply put, it's a pump and there is a restriction on the outlet side. An
engine cooling system isn't a swimming pool with a pump in the middle of it.