High pressure float expansion devices.

[DaBit]

Do these still exist; expansion devices with a float-operated needle valve? I am still searching for a suitable method of expanding my low stage refrigerant. When combined with a low pressure receiver, this seems a quite ideal method of flooding the evaporator.

[Peter_1]

Why not using a simple capillary tube? If you can maintain a stable condensor pressure (p.a. watercooled), then there could be no poblem with a capillary tube. (which is in fact the most reliable expansion device ever 'invented')
We made and serviced several cascade systems (R502 - and ethylene, down to -90°C) 1 st stage TEV, 2nd stage capilalry tube. The lenght of the 1 st tube we found it by.... trial and error.(we mounted a manual shutt off valve on the outlet of the condensor)
Serviced also some autocascade systems (down to -110°C) and there also where several capillary tubes.
Perhaps your configuration is a little different as i have in mind.

[DaBit]

My problem is the hugely varying load. A captube can cope with it, but only so far.

Furthermore: I hate captube tuning

BTW: information about my configuration can be found here.

[Andy]

Dabit,
we use a Danfoss OUB oil separator as a float on small hot gas fed rectifiers. You blank off the bottom gas connection on the oil sep, feed it with condenser liquid onto the top connection and feed the evaporator with the 1/4" flare oil return line. That is the smallest float that we can find, but it still maybe too large for your application. Differential or the time period between one opening and another maybe too large.
Floats are still common, with Danfoss making the SV as a main and pilot assembly comming to mind.
Regards. Andy.

[DaBit]

Indeed, it is too large for my application.

Could one detect liquid electronically and pulse a solenoid?

[Peter_1]

There exists level switches for monitoring the refrigerant level in liquid tanks. We use those for monitoring low liquid level, coupled on supervising systems.
In this switch, there is a little heating element build into it. As long as there is refrigerant around the heating element, level is OK. When the level goes down under the heating element, the switch will be tripped. This system is commonly used in alle the Mitsubishi Electric VRF systems to measure sufficuient level in the liquid tanks.
Second version is wit a LED sending his light into the liquid. In the switch there is a LDR wich "senses" a liquid or no-liquid situation.
I try to find the brand names of it.

Tis is one
http://www.medibix.com/runsearch.jsp...duct_id=456833

[DaBit]

Those sensors might come in handy. Any idea who stocks them in The Netherlands?