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View Full Version : how to test the superheat setting value of a thermo expansion valve?





27143721
05-06-2006, 07:25 PM
we ask the supplier to give us the expansion valve with required superheat already.
the problem is, how to testify it during incoming check?

Brian_UK
05-06-2006, 08:21 PM
You can check the setting on the orifice cage if it is a TEV made up from body and power head.

Otherwise you will have to test it when the system is operating.

Tricky name you have, it doesn't run easily off the tongue ;)

Peter_1
05-06-2006, 08:58 PM
What brand is it?

NoNickName
05-06-2006, 10:47 PM
Static superheat is normally published on the datasheet as SS= something.
Then if the TXV is adjustable you will be able to reduce or increase the dinamic superheat.
And if the TXV has an equilibrium capillary, then it will also be insensitive to the evaporator pressure drop

afeef
06-06-2006, 06:12 AM
hi
the TEV is working on specific rang of evaporator KW ,
if you need to have the exact superheat, you can check it while running the system, and readjust the orifice , to match the superheat required by system manufacturer,,

afeef

27143721
06-06-2006, 04:46 PM
Hi, friends, thanks for reply. but, is there not a way to check before installation?

if check during running, we offcourse can get the value, but, I don't want the test to be made for each equipment. that means wasting time.

NoNickName
06-06-2006, 05:25 PM
Hi, friends, thanks for reply. but, is there not a way to check before installation?


Yes, read the data sheet of that valve.

Brian_UK
06-06-2006, 06:57 PM
Hi, friends, thanks for reply. but, is there not a way to check before installation?

if check during running, we offcourse can get the value, but, I don't want the test to be made for each equipment. that means wasting time.
Some details of the valve you propose using would help get a more informed reply.

frank
06-06-2006, 11:07 PM
if check during running, we offcourse can get the value, but, I don't want the test to be made for each equipment. that means wasting time.
Well, if you do manage to find a way of short circuiting the process of correctly setting up a fridge circuit then I'm sure we would all appreciate the info as it would save us all a load of cash :rolleyes:

Temprite
07-06-2006, 12:03 PM
Connect the inlet of the valve to a bottle of nitrogen.(With a regulator of course:rolleyes: ).
On the outlet connect a low pressure gauge and a small opening to allow nitrogen to escape.A small pressure vessel would be helpful too.
Place bulb of TEV into container of crushed ice.0 degrees c.
Difference between 0 degrees C and pressure on outlet side converted to a temp for refrigerant you are using is superheat.

Josip
07-06-2006, 01:28 PM
Hi,

maybe is possible to do that on some other way, like...

yes, depend on brand and type of valve

Best regards,

Josip :)

Dan
08-06-2006, 03:34 AM
I think of static pressure as spring pressure. And if I had to measure it, I would be testing the spring pressure. All the other pressures involved in TEV operation are dynamic... Powerhead, equalizing line, outlet and inlet pressures. More than likely a static superheat is one established with a given inlet and outlet pressure possibly compensating for an equalizing line pressure and a given powerhead pressure.

Temprite's advice makes sense to me, considering that.:)

27143721
08-06-2006, 03:38 AM
Connect the inlet of the valve to a bottle of nitrogen.(With a regulator of course:rolleyes: ).
On the outlet connect a low pressure gauge and a small opening to allow nitrogen to escape.A small pressure vessel would be helpful too.
Place bulb of TEV into container of crushed ice.0 degrees c.
Difference between 0 degrees C and pressure on outlet side converted to a temp for refrigerant you are using is superheat.


Thanks, I think this is a good idea, I will try it.

Best regards!

frank
08-06-2006, 07:14 PM
Total Pressure is defined as the sum of Static Pressure + Velocity Pressure.

Static pressure can be compared to the energy force acting on the outer walls trying to escape and velocity pressure is the pressure produced by the flow of the fluid through the device.

Peter_1
08-06-2006, 07:59 PM
Total Pressure is defined as the sum of Static Pressure + Velocity Pressure.

... is the pressure produced by the flow of the fluid through the device.

It's the pressure generated when the flow is sudden complete stopped.;)

Dan
08-06-2006, 11:03 PM
Total Pressure is defined as the sum of Static Pressure + Velocity Pressure.

Of course. My bad. I meant "static superheat" Not Pressure.

Chris Burton
11-06-2006, 09:17 AM
If you need to roughly set up TEV during production then calibrate one system vavle at design conditions then strip it apart & measure compression of orifice cage spring (alco danfoss) or adjusting spindle(sporlan) with a vernier & repeat length on other valves. If small vavle then measure turns of adjustment. Better still make sure all systems are correctly commisioned on site to load conditions by qualified engineer.

phil
11-06-2006, 04:18 PM
gentlemen

many suppliers in thier catalogues give the size in kwatt output to that orifice of each manufacturer

it really depends upon the application and how it is designed so if it was designed by the supplier of the room things should be right but if you have any doubts and are asking the question here i repectfully suggest you get futher advice and training

Erik Detroit
13-06-2006, 10:30 PM
The method that Temprite posted is pretty much how the superheat is set before the valve leaves the factory. They use usually an automated system, a bath that is carefully controlled, pressure transducers for upstream and downstream pressures, a PLC to read the parameters and turn the bias screw to get the required static superheat, and of course datalogging for the purposes of process control.

I'm in automotive where almost all valves are between 1 ton and 2 ton with 95% being 1.5 ton. The standard orifice size is 0.8mm for these valves. I would think your valve supplier could tell you what orifice size to use for other tonnage.

I would think however that your time would be better spent insuring that their process and quality control is robust. Maybe ask for a plant tour, and ask to see the process they follow?

Regards, Erik