3 replies to this topic

[rsk]

Mr Art I regret for the inconvenience, its great u keep us reminding of our mistakes. Now i have completely modified my post.

As show in schematic
1. Heat dissipated by nuclear spent fuel in system tank at rate of q MW is being removed by circulating water through HX in a primary closed loop system which in turn transfers heat to secondary cooling system.

2. Pump Required Flow through HX for a specified differential temperature DT can be found as
(q/cp* DT ) & taking margin for purification flow as 5%. Gross pump flow is 1.05(q/cp* DT ).

3. Pump developed head will be to cater for frictional losses through suction & discharge lines & HX ie (hs+hd+h HX).

4. System inventory including piping & equipment is 500m3 & normal temperature is 40 deg & expected variation is +/- 2 deg.

5. How shall i approach for sizing of expansion tank ie Volume & elevation abovepump centre line.
6. shall i consider expansion tank to be riding at suction or at discharge & where on suction or discharge lines. what is the basis.
7. additional Data are Pv vapour press of water at 40deg & Hs is the NPSH required for the pump.
8. How elevation of expansion tank will affect hydraulics ie system resistances curves.

Attached Files

•  hydraulics.xls   56.5KB   108 downloads

[Art Montemayor]

RSK:

You are a veteran member of this Forum so you know that I always treat students as I would a fellow Chemical Engineer – with frank, honest truth and candor. I believe that all students deserve to be treated that way and not "cuddled" or "babied" because a lot of serious and hard work is expected out of them by their universities and it is best that they find out bad news before they go into their classes.

My comments are as follows:

1. It is not possible to intelligently understand what you mean when you open your query with a phrase instead of a clear and concise sentence composed of noun, verb, adjectives, and object. I don't know what your first phrase means – I doubt if anyone can guess.

2. Your submitted Excel schematic sketch (if you can call it that) is horrible. My 9-yr old granddaughter can create a far better, intelligent, readable, and understandable sketch than the one you submitted. I am not criticizing your artwork; I am criticizing your inability to convey or communicate in a normal, conventional engineering manner. Your sketch makes no sense. You titled this thread "Expansion Tank In Closed Loop System", yet you show an OPEN LOOP. There can be no difference in level between your reception tank and your expansion tank since both are connected to the same line and are at the same pressure: atmospheric.

3. I can't even draw my own version of what you depict because I don't know what kind of system or equipment you are proposing. Please download my Workbook on How to Draw Engineering Sketches with Excel and practice & practice using it as a guide. You need to know how to communicate with graphics.

4. You ask for engineering answers (expansion tank level) but you fail to give us basic data and detailed information. What is the volume of liquid in the system? What are all the heights? What are the pressure drops? If I answered your query in the same manner you have put together the questions and sketch, you wouldn't understand me either. Is that what we are expected to do as engineers? I don't think so ......!

5. There are no standards on expansion tanks. You design and apply what you need.

6. You haven't even HINTED or IDENTIFIED THE FLUID that you propose to pump. How basic and real is that?

7. The best insight I can give you at present is a request that you put together a solid, detailed, understandable graphic description of what you propose. Before you attempt to calculate and work with a pump Performance Curve and a System Curve, you need to improve your ability to understand how to describe and sketch your problem. That is the basic requirement in all Fluid Mechanics. If you can't describe it, people (your future bosses) won't be able to understand it.

Good Luck.

[rsk]

sorry for inconvenience, Please revisit my modified post.

[djack77494]

rsk,
Thank you for clarifying your situation. Yours appears to be a very typical closed loop system with the required expansion tank. Thinking about the function of the tank, it needs to handle the expansion and contraction of the circulating fluid through normal thermal cycles. We can picture your situation as follows:

Initially your system may be cold, for example at the beginning of a startup. As you proceed with the startup, you circulating fluid will remove heat from the Spent Fuel Tank. It will continue to warm until it reaches the normal operating temperature. This warming is accomplished, of course, with a corresponding expansion of the fluid. Take this a bit further, and cover the full range from minimum to maximum expected temperature. At minimum temperature, the contained fluid volume will be a minimum due to its high density at low temperature. Your liquid should be at its low point in the Expansion Tank at this time. You should be able to measure the level, so it will probably be at least (say) 6" above the bottom tangent line of the tank. At the maximum temperature, the level will be at its highest point, but you should still be able to measure it, so it will be (say) 6" below the top tangent line of the tank. Be very conservative in estimating minimum and maximum temperatures and total system volume and allowances for instrumentation. The result should be a robust design.