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sahasushank
Associate

Join Date: Apr 2008
Posts: 50

Valve and pump Control for Mixing Application

04/21/2008 7:44 AM

Hello

I am trying to simulate a fluid heating curve from ambient to max operating temp. To accomplish this I have proposed a system with 2 tanks, one at ambient temp and the other at the max op. temp. The flow is moderated using two proportional control valves with a 4-20 mAmp input.

From there on the pipes meet at a mixing manifold and the mixed fluid is pumped for the simulation rig testing. the simulation rig consists of 3 tanks with constant pressure drop across each. now i need a variable flow (VFD) pump since i might decide to bring any compination of tanks online (one or two or all three).

The valves are controlled using a PLC which takes in inputs based on temperature of the three pipes (the two inputs and the final mixed temp). I need the final temp to follow a preexisting curve.

the min flow factor for the valves is 3 and the max is 15.

Heres the first question, does this absurd or quite doable? I have all the parts (quotes on them atleast) and i jsut want to get a confirmation before i order anything.

The pump is 1 hp end suction centrifugal pump (w/inverter motor) with rated flow capacity of 70 GPM.

The second question comes here. would a VFD work for the application im proposing. To maintain the flow rate im going to be using a differential pressure transmitter and a plc. or even input pre determined values into the vfd which just switches or just manual.

Does the whole system sound viable?

Im an engineering student doing my co-op at a company and well need help. Thank you, i really appreciate any response or assistance.
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Pathfinder Tags: Fluid Mixing Valve Control VFD
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Ried
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Join Date: Dec 2005
Posts: 1602
Good Answers: 19
#1

Re: Valve and pump Control for Mixing Application

04/24/2008 12:15 AM

I do not quite understand what information you are trying to track.

Are you trying to determine the specific heat of athe fluid? If so, I think you would want to use a "Bomb Calorimeter" to get the information. (And no, it does not normally explode. Just be careful which fluids you test and use good engineering judgement.)

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sahasushank
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Join Date: Apr 2008
Posts: 50
#2
In reply to #1

Re: Valve and pump Control for Mixing Application

04/24/2008 7:01 AM

Nope, im trying to simulate engine coolant warmup.
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Ried
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Good Answers: 19
#3
In reply to #2

Re: Valve and pump Control for Mixing Application

04/24/2008 11:01 PM

Howis fluid recirculated back to the supply tanks? I am assuming it might be critical to keep constant pressure on pump suction?

Is coolant system open or closed? Will simulation equipment be an open opr closed system?

Is discharge pressure through three tanks kept constant?

I think the temperature control scheme is do-able, but based on previous experience with diesel engine test cell work the system pressures may cause problems if not kept under close control.

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sahasushank
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Join Date: Apr 2008
Posts: 50
#4
In reply to #3

Re: Valve and pump Control for Mixing Application

04/28/2008 6:39 AM

well the two initial tanks are open to the atmosphere. and the recirculated fluid is returned to the two tanks , half after being passed through a radiator the other directly after after-treatment phase..

the mixing manifold is closed and even though it may appear that the system is open (since it is open to atmosphere), it is actually closed and yes youre right pressure will play a critical role in determining and managing the flow rate.

discharge pressure through the three tanks is constant. Well for the temperature screen ive been playing around with a PLC but it doesnt really offer me much. i mean ic an use a rtd input for temperature and generate required setpoint values but after that im stuck. the pressure one im planning to use aplc to monitor the back pressure and accordingly control the vfd.
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Ried
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#5
In reply to #4

Re: Valve and pump Control for Mixing Application

04/28/2008 11:24 PM

I am normally the last person you want to discuss PLC programming. Isn't there a way to program a temperature setpoint that varies or is reset based on time? At Time0, t=ambient, Time 1, t=ambient+x1, Time=2, t=ambient+x2, etc., etc., based on data from your temperature curve.

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sahasushank
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#6
In reply to #5

Re: Valve and pump Control for Mixing Application

04/29/2008 6:29 AM

This is the first time im doing PLC ever :). Im a 3rd year engineering student on my co-op and well this project was put on my lap and my boss on my ass to get everything done although i dont even know the deadline. But oh well, i did make 2 programs in PLC. one with a PID loop with a variable setpoint but i dont know if that would work and the other with a for loop which uses multiple if conditions.
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Ried
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#7
In reply to #6

Re: Valve and pump Control for Mixing Application

04/29/2008 11:14 AM

Start a new link on the electrical engineering forum and ask for advice on programming your PLC.

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