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what does CFM stands for?
why when you look at an evaporator as the BTUH -20F increases, the CFM decreases
An evaporator of 6400 BTUH -20F has 2140 CFM
Another evaporator with 9300 BTUH -20F has 1910 CFM. Both have two motors, same kind of connections.
I think it stands for Cubic Feet per Minute and has to do with the design velocity of air through the evaporator.
If an evaporator has more CFM should it cool faster?
I was looking on another site and they used CFM to describe the volume of refrigerant through the evaporator. You would think that more refrigerant flowing through would be more powerful, but I am not sure. Hopefully someone else will shed some light.
In this case, I imagine that CFM means Cubic Feet per Minute AIRFLOW.
2140 CFM=35.66 CF/second
35.66 CF/Second = 1009 LITRES per Second.
That's a hell of a lot of refrigerant to push through an evaporator.
CFM represents the amount of air flow the evaporator requires from the evaporator fans to maintain its design duty in BTUs
cubic feet per min
Fan rating for the evaporator ; even many a times condenser fan also is mentioned in cfm . Cubic feet of air per minute ; fan flow rate
Maybe it has only 1 pipe through it? ;)Quote:
Originally Posted by Voyager
Should have thought about it a bit more, sorry!
All the abbreviation means is Cubic Feet per Minute.
Compressors are rated in CFM Swept Volume; ACFM (actual CFM) and SCFM (Standard Cubic Feet per Minute, for an air compressor refers to the normal intake conditions, which would be at Standard Temperature and Atmospheric Pressure.
For refrigeration compressors, you will also see Suction CFM and Discharge CFM; only useful for the actual operating conditions.
Your rating sheet should say CFM air; but the unit with the higher rating probably has a greater coil depth or denser finning...Either one would cause the same fans to blow less air, due to the higher resistance.
CFM=cubic feet per minute
there is a relation between 1 ton of refrigeration and cfm
1 ton= 400 CFM
,I use it to calculate CFM FOR 1.5 Ton of refrigeration for fan coil units located at the hotel where i am working..there a cfm meter which u simply hold it in front of a fan from where chilled air is coming,the meter gives the value in ft/min. then u simply multiply this valve with th grill area from where this air is coming ,finally u have the answer in CFM.It also gives an idea whether the unit is of 1 ton or 2 tons and whether the coil is choked or cleaned.
Quote:
Originally Posted by kamal12341
Not always. You cannot use examples like this for all applications. What works for air conditioning systems will not apply to refrigeration systems.
Some evaporators may also have different fan blade pitches for the same diameter. Or, they might be listed as different airflow due to higher static pressures, which will cause a change in the delivered airflow volume.
For A/C systems a better rule of thumb is the equation:
BTU=1.09*CFM*dT(air)
and 1 ton of ref = 12,000 Btuh
But don't go trying to apply it to other systems as the 1.09 encompasses the density and specific heat of air at sea level and at approximately room temperature.