TXV's: any available in 70-200W cooling capacity?

[aaron_k]

The smallest TXV's I've found (commercial off the shelf) have been much larger than the stated size I'm interested in. Does anyone know of a manufacturer of "micro" TXV's for very small systems?

The refrigeration system I'm working on needs to operate at a huge range of loads and temperatures. the system uses a Danfoss BD35F variable speed compressor, and I'd like to have the opportunity to use the variable speed capability to further reduce power consumption. Does anyone have a lead for me?

Many thanks in advance,

Aaron_K

[Magoo]

The Danfoss tx 0X orifice range are minimal rated. failing that select a capillary tube

[mad fridgie]

If TXV is a pressure drop device, if you want to go down this track, you are able to down size by introducing a pressure drop between the TXV outlet and the evap inlet. This effectively reduces the pressure drop across the TXV thus reducing the capacity of the valve. (A bit of experimentation is likely required.) Or perhaps a simpler way is to have 2 capillaries, switching between the 2 depending upon the circumstances

[aaron_k]

Thanks for the ideas. I've had issues in the past running a TXV that has significantly excess capacity hunting. Looking at Danfoss' data, correcting for subcooling in some operating ranges the valve has 1.5X the rated capacity. That would be more than 3X the max capacity required.

The current design is based on a TXV, but I need to improve pull down and energy efficiency across a temperature range. The refrigerator is battery / solar powered, so every watt counts. Even one solenoid coil consumes too much power to be considered.

I'll do some more digging. Thanks again.

Aaron_K

[mad fridgie]

Thanks for the ideas. I've had issues in the past running a TXV that has significantly excess capacity hunting. Looking at Danfoss' data, correcting for subcooling in some operating ranges the valve has 1.5X the rated capacity. That would be more than 3X the max capacity required.

The current design is based on a TXV, but I need to improve pull down and energy efficiency across a temperature range. The refrigerator is battery / solar powered, so every watt counts. Even one solenoid coil consumes too much power to be considered.

I'll do some more digging. Thanks again.

Aaron_K

When it comes to sizing imagine you are installing a distributor (pressure drop), you will need a externally equallised valve.
The duty is based upon the inlet conditions (liquid pressure and temperature) and the outlet pressure of the valve, so for example yo have liquid at 30C pressure and 28C actual temp(2C sub-cooling)
You actually want -20C in the evap,so go backwards install a small pipe between the valve with a 15C pressure drop, calclate at your load, with 30SCT, 2C sub-cooling and SST of -5C. Play around with the figures until you get the desired result

[hanif]

Danfoss has one used by YORK in YCav &yciv BUT DOSE HAVE MACHANICAL FAILURES TOO

[Brian_UK]

Would a small electronic valve do the job ?

Such as used inside Misti etc units.

[aaron_k]

Thanks again everyone. I looked at small electronic valves; is the "Misti" part available OEM? I'm not familiar with the brand.

@mad_fridgie - I'll work on your idea some more - thanks!