If i have water at 90 C, (pressure 16 bar) with a flow rate of 80 kg/s and i need to reduce the flow rate to 20 kg/s before running it through a heat exchanger, can i achieve that with a flow control valve without a drop in temperature ? And if there is a drop in temperature would it be negligible ?
And if the water leaves the heat exchanger at 50C with a flow rate of 20 kg/s can i do so with a liquid pump without an increase in temperature ?
hello,
why do you expect temperature drop?
do the fluid expand and gets cooled? meaning you have such loss of pressure that water evaporates during the valve pass.
The other question is you close the valve to give you 20 kg/s instead of 90 kg/s correct? well you have to be clear on what you want to do becase if 90 kg/s is what comes to you system but you want to send 20 kg/s to the heat exchanger then from mass balance you must know where the other 70 kg/goes.
Valves contol volume that passes throught them.
The temperature change will be quite small at these pressures, but you can easily calculate it with an Excel spreadsheet having steam property function calls. If you don't have such, these can be found on my web site. If you intend to throttle the flow for control purposes, it makes a difference if you throttle upstream or downstream from a control standpoint. For example, all feed water heaters and moisture separator reheaters throttle on the downstream side. I also share Reald's concern for where the rest of the flow will go if you throttle. Note also that throttling and diverting (splitting) are two very different processes.
Difference in temperature will be very low - i don't think it will affect the efficiency in your case.
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