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yuhonghai
23-04-2007, 02:15 AM
Hi sirs;

Normally there are different sizes of surge drums you can select from the supplier's catalogue,and you know the diameter,length and sizes of nozzles,and also the supplier offers the capacites of them with ammonia at certain condition,if I want to use another refrigerant,such as R134a or R507,how can I check it with new refrigerant,are there some tips for them?

Thanks

US Iceman
23-04-2007, 02:26 AM
The ASHRAE Refrigeration Handbook has some suggested guidelines for this. Basically, it involves finding the maximum separating velocity for the liquid & vapor at some given condition for a specific refrigerant.

The volume flow required (by the desired system capacity) divided by the maximum separating velocity is the minimum separator cross-sectional area required.

yuhonghai
23-04-2007, 11:05 AM
Hi Us iceman,
thank you for your answer.From your replys on the forum,you should be a expert in refrigeration field.I think the diameter of the surge drum is one factor that influence the separating effect,and we have to pay attention to the distance from the inlet and outlet of nozzles.How to caculate them?If you can offer me some information about the sizing of the surgedrum,that would be great!By (yuhonghai@bingshan.com.By) the way,if you have chance,welcome to China and enjoy Olympic game in 2008 Beijing.

TXiceman
24-04-2007, 04:04 AM
The ASHRAE data and formulas are based on Stokes equation. You will need to know the density of the liquid and vapor as well as the surface tension of the refrigerant.

For the newer refrigerants, there has not been much work in publishing short cut sizing charts.

You will need to determine if you are using a vertical drum or a horizontal drum. If horizontal, the number of inlets and outlets must be considered. You can use 2 outlets with a baffle and divide the total flow by 4, as 1/4 of the flow will approach the nozzle from each side.

When you say surge drum, we you meaning a suction accumulator or is it a recirculated over feed drum?

I afraid that thee are a lot of questions, more than there are answers.

In any case, you need to check you separation velocities as yo do the initial pull down on the system to be sure you have adequate separation under more than just the single point design. As a safety, I use 80 to 90% of the calculated maximum separation velocity in gravity type separators. If yo want to use a dimister pad design, you can run a bit higher velocity still achieve separation.

As a word of caution, process design engineers use a design criteria that allows fro a certain percentage of carry over. They feel 1 to 2 % liquid carry over is suitable. However in a refrigeration system,the compressor generally can not take this much carry over. And you run head on into a different set of design criteria.

One -40 d, R22 system which we are revamping (175 TR) has a thermosiphon drum supplied by a process evaporator supplier with a velocity approaching 500 feet per minute (FPM). From Stokes Equations we can justify a maximu of about 120 FPM. However from experience, I will not go over 90 FPM for this type application. Since we are not suppling or guaranteeing the evaporator and drum, we are leaving an old suction accumulator in line to protect the compressor and given the customer a written warning about the design criteria falling outside of normal refrigeration design.

Ken

US Iceman
24-04-2007, 04:51 AM
I had a long reply to this thread this morning and lost it when posting. I see TXiceman is on the job with good recommendations.

You need to spend some time looking for design equations and ASHRAE is the best starting point. Look for the Refrigeration Handbook.

It's important to understand all of this before you start to use ANY equation(s).

Also, I would suggest you remove your email address and use the Private Messaging system to discuss private information. Spammers can find your email address like they found one of my old ones.:mad:

yuhonghai
24-04-2007, 06:14 AM
Hi,every one,thanks a lot of your answer.
I'll learn from you here