Hi All,
Generally we are using 1TR =400CFM in most of our HVAC system design. But which is wrong and there is no theoretical calculations on this too.
Before discussing further, I just want to describe what is TR and what is CFM.
TR is called as ton of refrigeration TR or refrigeration ton RT. TR means amount of heat extracted to produce one ton of ice.
CFM is the unit of measure of air flow, CFM stands for cubic feet per minute. CFM means volume of air entering the room in a minute.
Coming back to the topic, 1 TR may be equal to 400 CFM or 300 CFM or 450 CFM or some other value . It will differ one manufacture to another manufacture .
However, there is a standard equation available to relate the BTU/HR and CFM .
BTU/HR=1.08×density correction factor ×CFM×Delta T
Where,
1.08 is constant for air at standard condition
Delta T is difference between inlet and outlet air
CFM is cubic feet per minute
By using the above formula, we can calculate the CFM for any TR cooling equipment.
I would like to add another point that as per the ASHRAE,we don't have any formula to relate the TR and CFM.
As per the human comfort standard, 1TR of air conditioned should have a discharge of air 400 CFM .If we discharge below 400CFM,the people who using the equipment will feel suffocated even though we maintained low temperature.
The conclusion of this topic that if we want to calculate the CFM of equipment roughly, please use the below thumb rules or otherwise you want to calculate the CFM exactly ,please use the equation 1 .
For centralized air conditioning system
1TR =400CFM
For non centralized air conditioning system
1TR=300CFM
Thanks for reading our blog post. Please post your doubts in the comment box if any.
By
Ashokraj S
