Can anyone give me some information on orifice plates, as a metering device, please?
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Can anyone give me some information on orifice plates, as a metering device, please?
Tony
What info are you looking for specifically? Let me know and I'll try and help you out.
Frosty
Any info really. Its just that I've never come across them.
What sort of systems would use them?
Why they would be used, as opposed to other metering devices?
How do they work- is it just like a capilliary tube?
Tony, oriface plates can be used in replacement for electronic expansion valves on flooded systems. Usually used to meter liquid to evaporators in pairs, each equiped with a solinoide valve. One off pulse/bleed solinoid to keep the flow in the system moving and one on pulse/main to feed the main liquid to the evaporator and in some cases to over-feed the evaporator for liquid subcooling purposes. Switching of the main valve/oriface plate is by High Pressure Float switch, Low Pressure Float Switch or on the degree of liquid subcooling accross a heat exchanger, as in a Low Pressure Receiver System.
Other aplications for an oriface are oil metering on simple oil return lines from separators or small fixed load refrigeration coils where a means of separating liquid, such as an accumulator has been fitted (oil coolers and refrigerant purgers).
I hope this is of some help, post again if you require any clarification or just more information.
Regards. Andy.
The short tube orifices, aka, "plug" orifices, used in the majority of residential a/c and heat pump systems are essentially orifice plates. They are a precisely formed hole for refrigerant to flow thru. The flow equation for an orifice is:
m = C<sub>f</sub> * A * (2 * g<sub>c</sub> * <FONT FACE="Symbol">r</font> * <FONT FACE="Symbol">D</font>p)<sup>1/2</sup>
where:
m = refrigerant flow, lb<sub>m</sub>/sec
C<sub>f</sub> = flow coefficient
A = area of orifice, ft<sup>2</sup>
g<sub>c</sub> = gravitational conversion factor, 32.174 lb<sub>m</sub>-ft/lb<sub>f</sub>-sec<sup>2</sup>
<FONT FACE="Symbol">r</font> = refrigerant density, lb<sub>m</sub>/ft<sup>3</sup>
<FONT FACE="Symbol">D</font>p = pressure drop across the orifice, lb<sub>f</sub>/ft<sup>2</sup>
Thanks Andy and Prof Sporlan.
Your help and information is much appreciated.