Drew

31-03-2017, 07:29 AM

Hi all,

im trying to get my head around how to measure the capacity in kw of what could be delivered out of an air diffuser.

im used to measuring the capacity of what coils deliver based on the following formula

kw = l/s x 1 X 1.2 x temp difference.

i understand I can measure the return air and get a temp difference.

what I'm battling with is say I have 2 rooms each with a diffuser that's delivering the same temp air and same air quantities but the rooms are different temps then my td will change and then the capacity changes ??

why if each diffuser is delivering the same temp and l/ s isn't the capacity the same of the air being introduced . Why would the room temp influence the capacity.

( I have assume the td to be based on the supply air temp and the room temp.)

if the one room is colder and we introduce the same warm air into both the formula dictates that we are introducing more capacity into the colder room.

therefore how can the colder room be getting more capacity than the warmer room if the flow rates and temps are the same out of the diffuser??

i have bought the the flir tg165 Infra red thermometer and have being thinking of how to measure the capacity of airdiffusers once I've measured flow rates and temps but I've stumbled on how to measure the temp difference . Obviously I've got the supply temp and the return air temp so it is easy enough but have got stuck on how the room temp , which is the temp I was going to use as the return air temp influences the capacity.

Is there a way to measure the capacity of air being introduced without a temp difference based on only the supply air temp and flow rate or do you need a temp difference???

my head aches.

im trying to get my head around how to measure the capacity in kw of what could be delivered out of an air diffuser.

im used to measuring the capacity of what coils deliver based on the following formula

kw = l/s x 1 X 1.2 x temp difference.

i understand I can measure the return air and get a temp difference.

what I'm battling with is say I have 2 rooms each with a diffuser that's delivering the same temp air and same air quantities but the rooms are different temps then my td will change and then the capacity changes ??

why if each diffuser is delivering the same temp and l/ s isn't the capacity the same of the air being introduced . Why would the room temp influence the capacity.

( I have assume the td to be based on the supply air temp and the room temp.)

if the one room is colder and we introduce the same warm air into both the formula dictates that we are introducing more capacity into the colder room.

therefore how can the colder room be getting more capacity than the warmer room if the flow rates and temps are the same out of the diffuser??

i have bought the the flir tg165 Infra red thermometer and have being thinking of how to measure the capacity of airdiffusers once I've measured flow rates and temps but I've stumbled on how to measure the temp difference . Obviously I've got the supply temp and the return air temp so it is easy enough but have got stuck on how the room temp , which is the temp I was going to use as the return air temp influences the capacity.

Is there a way to measure the capacity of air being introduced without a temp difference based on only the supply air temp and flow rate or do you need a temp difference???

my head aches.