spridgets
[Top] [All Lists]

## Re: "Oil Pressure" & "old" overheating problem

 To: "Peter C." , "Geoff Branch" , "Mike MacLean" Re: "Oil Pressure" & "old" overheating problem Fri, 28 Sep 2001 12:10:21 -0400 <21144-3BB44A7A-2896@storefull-226.iap.bryant.webtv.net> <5.0.2.1.2.20010928080637.02182740@mailbag.com>
 ```----- Original Message ----- From Peter C. > The coolant needs to go slow enough through the engine to pick up > the heat, but not too slow or the temperature difference between iron and > coolant wont be great enough. I barely remember my 4th year thermodynamics - but here goes. The RATE of heat transfer between a FIXED surface area of engine metal and coolant linearly depends on the temp difference (delta T). So cooler coolant equals more transfer. The metal don't care if the coolant is moving or at speed. Therefore slower flow means the coolant next to the metal warms up more, the delta T is less, and heat transfer is less (assuming the metal temp remains constant, i.e. let's call the metal to be at momentary equilibrium). The other thing you cannot avoid with slow flow in the engine is that you will wind up with a cool end and a hot end of the motor. The potential for design hot spots is increased. Also --- flow rates introduce the topic of turbulence and boundary layers (Reynolds numbers) next to the metal. Boundary layers (slower flow) are effectively insulators. Turbulence (high speeds) is better for heat transfer. I don't know if internal engine water passages are experiencing turbulence, except for sure at the water pump impellers and probably not at all in the rad cores. Rads are more complex in that you have fluid flow on one side and varying temperature/speed air flow on the other. Unlike motors rads are not so restricted to an "operating temperature" or a "mechanical configuration" and therefore can have long passages for increased time exposure, can have space shuttle fin technology, can have a hot end and a cool end etc. Has anyone noticed that the water passages in a motor block have not changed much in 100 years, but look at what has happened to rad technology in terms of size, weight and efficiency. There is a long engineering equation that tries to simulate reality for practically everything, up to and including rising bubbles in a boiling pot. A lot of car stuff such as balancing the heat output of the engine with the heat dissipation at the rad and in the engine compartment is derived from empirical test data and component suppliers specs. This thread is struggling with the end result of a 30's Brit low production volume engineering mentality, that designed everything with a minimum theoretical calculation contingency safety factor. No allowance for loss of strength due to corrosion, for Arizona temperatures, for poor owner maintenance and lastly they designed RHD cars and converted (with compromises) 80% of them to LHD. Bottom line, with marginal cooling, you have to guess or figure out where your weakest and or cheapest link is - and say goodbye. My take - speed it up in the engine (without cavitation), slow it down in the rad (bigger rad), max air movement (shrouds and fans). When you have excess cooling capacity, then the thermostat can once again become the Controller. Mike L 60A,67E,59Bug ```
 Current Thread RE: "Oil Pressure" & "old" overheating problem, (continued) RE: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown RE: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown <= Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown RE: "Oil Pressure" & "old" overheating problem, Unknown RE: "Oil Pressure" & "old" overheating problem, Unknown RE: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown Re: "Oil Pressure" & "old" overheating problem, Unknown