No thermostat?

[larso1]

Egon wrote: "Are there not some types of graphs that show the fluid state versus pressure versus temperature???"

Yes, I think you're referring to the "Steam Tables", AKA "Thermodynamic Properties of Water at Saturation," and give characteristics such as specific volume, enthalpy, and entropy, all at a given temperature and corresponding absolute pressure. I'm sure there are graphs too, I just use the table because it's easy to use. HTH's.

Bill

 

[patrick_g]

Some engines run on a thermosiphon principle that does not include a water pump.

Perhaps do some googling and all will become clear.

There are simple low maint diesel gen sets and stationery engines that not only don't have a water pump, they don't have a radiator either. They just have a tank built around the cyl head(s) and you just top them off from time to time as when refueling.

Pat

 

[Egon]

At one time those were a very common type of engine Pat. Back before you were a young lad!!

Bill, I was referring to specific fluid charts in general. Not just tables/charts for steam.

 

[SPYDERLK]

Bill, did you turn on a light switch and put some illumination on the topic???

Said enuf ways, and from multiple sources, it sinks in.
larry

 

[patrick_g]

In otherwords, what you said was "not valid" (<to slow coolant down so that it spends enough time in radiator to effectively transfer liquid heat to air>) is indeed a valid statement IMHO.

Actually it is BALDERDASH!!!!

For years I have heard various shade tree mechanics talk about how if the water goes through the radiator toooooo fast it doesn't have time to lose the heat and it is not as effective.

This is JUNK SCIENCE and is totally bassackwards!!!!

Heat loss is the cumulative effect of many factors including the ambient temp, RH, Thermal conductivity of the radiator, coolant used and on and on and on but we can simplify the situation and consider two identical setups with one having slow flow and the other fast flow.

Delta T is the chief thing driving heat transfer in a radiator. This heat exchanger device (radiator) is actually poorly named as radiation is not the primary means of shedding heat in it. If all the radiator is hot then all of it is shedding the maximum amount of heat. If only part of the radiator is hot (near the water inlet) and the rest, especially near the water outlet is cool due to heat loss of the water then that part of the water sheds less heat and the net result is less heat is removed from the radiator. This assumes the same extant conditions of ambient air temp, RH, speed, etc and the same type of coolant and on and on.

Rather than drag calculus into the discussion lets simplify to make it totally obvious. Lets consider the argument that slower moving radiator flow cools better. If slower is better lets go really slow and see the results. Hot water enters the radiator and starts losing heat to the moving air. Since the water is flowing really slow the water is cooled really well before it reaches the outlet pipe (a good thing?) There is a lot of heat being generated in the engine and if the flow rate is reduced to say a teaspoon an hour there is no way for a teaspoon of water to transfer the heat generated in the engine in an hour! Ok this is too slow, agreed?

Lets speed up the flow and consider what happens. Faster flow moves more hot water into the radiator and it makes its way further across the radiator before being cooled "X" degrees. Now more of the radiator is hotter so it is more effectively shedding heat. Lets get magical and move the water through our imaginary radiator faster than the speed of light. Now the water makes it through the radiator before it can drop so much in temp as before. In this case the whole radiator is nearly uniformly hot (at the temp of the water coming into the radiator.) Now since the whole radiator is hot the whole radiator is shedding heat over all its area of contact with the air flow.

It should be clear that a radiator that is hot all over looses more heat to the air flow than a radiator that is only hot in a small area. Remember delta T. The hotter the average radiator temp is above ambient the more heat it can shed.

There is NO FLOW RATE that results in more heat transfer than a faster flow rate. Improvements in heat transfer with increasing flow rate run into the law of diminishing returns where additional increments in flow rate yield smaller and smaller increases in efficiency. Faster is always more effective at moving heat but at some point the additional gains are too small to justify the effort of getting them. In most instances rather than run a 40 HP water pump the engineers just put in a larger radiator (more frontal area) or a deeper radiator (more rows.) Each additional row of a radiator does less than the previous one because the last rows are receiving hotter air across them due to the hot rows in front of them. At some point it is way better to go larger in frontal area than more and more rows.

Pat

 

[3RRL]

Well then balderdash it is!
Spyderlik has been explaining this since post #7 and his subsequent posts have already made it clear to me.
School's out...

 

[patrick_g]

Whew, glad I didn't get a penalty for piling on!

Pat P.S. School may be out but this may be on the final exam so don't forget it!

 

[patrick_g]

At one time those were a very common type of engine Pat. Back before you were a young lad!!

Egon, Although not seen as often as in the olden days before the big rocks cooled when we were young but there are NEW diesel gensets with that sort of cooling system. No radiator, no fan, no fan belt, no water pump, just a water jacket (open to the atmosphere with no pressurization.) The idea is that you top off the cooling water when you refuel the generator. Some folks use larger fuel supply tanks and make a little gravity based "water minder" like a chicken waterer made with a Mason jar in function but with greater capacity. Then the low oil shutoff is the only thing to kill your backup electricity.

Pat

 

[Egon]

On the water jacket/evaporation cooling system I am not too familiar but whats new?

Now for radiators should we be thinking crossflow or vertical tubes? ehh

 

[woodchuckie]

Does it work the same with a heater core. Although the air is cooler on high speed,does it heat the car quicker or does the low air flow which is warmer heat the car faster. And how about the air conditioner on max and low speed.