# Water consumption in cooling

Consider that you are cooling a mass of steel from 1,000 °C to 920 °C. To accomplish this a water flow of 2,000 liters/min is required, and the water outlet temperature increases 10 °C. The water pressure at the inlet is 5 kg/cm2.

Now suppose that you increase 30% the water pressure by means of a booster pump.

Is this going to result in less water consumption for the same drop in the temperature of the steel?

Related General Engineering News on Phys.org
How is the steel being cooled by the water?

russ_watters
Mentor

The steel bar is very long because of the rolling; and has a round cross section. To cool it the bar
travels across a set of hollow castings placed one after the other. The castings have water chambers,
provided with many holes so that the water fills the chambers, and with the water pressure a shower
takes place, with water getting in contact with the steel, in such a way that the steel bar is cooled.

russ_watters
Mentor
That does help; So this is a real-world situation.

It appears to me that the primary limiting factor is going to be the heat transfer between the rollers and the product; a 10C rise in water temperature is not much considering just how hot the steel is, so the method of cooling is keeping heat from easily getting to the water.

Now that isn't to say you can't impact it by changing the water parameters, but changing the pressure is an odd parameter to pick. It seems like you meant increasing the flow by increasing the pressure, but then you asked if it would reduce water consumption, which seems like a contradiction. And even then, "consumption" is an odd choice of words here, as I would think the water is being re-circulated to make the actual "consumption" very small. So again, some more details about the water supply system would be useful.

Just an outside guess about the configuration, but if you are using once-through water from a tap and you use a pump to boost the pressure on a system with no controls, you will see an increase in flow, an almost proportional decrease in delta-T and a very small decrease in the temperature of the steel.

OK Russ. Now you are helping me to clarify things. You wrote: "...but changing the pressure is an odd parameter to pick..." I agree 100% with this point. Increasing pressure won´t help. So I see 3 options:
1) Increase water flow. But this goes in the opposite way; will increase water consumption.
2) Find a way to recirculate the water. At this moment I don´t know how.
3) Redesign the hollow castings in such a way that water could be in contact with steel for a greater time and so take more heat away, and then reducing water consumption. Again, at this point I don´t know how to accomplish this.

russ_watters
Mentor
2) Find a way to recirculate the water. At this moment I don´t know how.
That requires a pump, a cooling tower and a mechanical engineer to design it for you. It isn't something that can be done here.
3) Redesign the hollow castings in such a way that water could be in contact with steel for a greater time and so take more heat away, and then reducing water consumption. Again, at this point I don´t know how to accomplish this.
If you just reduce the water flow by closing a valve partway, the delta-T will go up proportionally without affecting the cooling capability much.

And I don't think the water is the heat transfer bottleneck: its the way the rollers touch the steel that limits heat flow. A mechanical or process engineer would probably be needed. If you are spending a lot of money dumping water down a drain, it is probably worthwhile to put dome serious effort into the investigation.