Help with Heat Load Calculation please.

[Proximity]

Hi Guys,

I've been a long time lurker and need some help

A new client I have has decided to air-condition a brooder house (A small building of only a few square meters that is used to house chickens right after they were hatched.) and I'm lost when it comes to working out the required heating and cooling capacity.

Usually, air-conditioner sizing isn't an issue however the temperatures and fresh air requirements are a bit out of my depth.

• The space is going to be insulated with 50mm polystyrene refrigeration panels (Walls and roof only).
• Room size is 10m long X 5m wide X 2.2m high.
• The air-conditioned temperature needs to remain between 25°C and 30°C
• Ambient temperatures range from 2°C to 32°C
• Humidity ranges between 33% and 63%
• +-1kW of lighting/fans etc.
• And for the kicker, 100% fresh air is to be used.

Any advise, formula or input would be appreciated.

[frank]

How many air changes per hour are required?

[Proximity]

How many air changes per hour are required?

The client hasn't stipulated the number of air changes required.

Based on the information received from the client and internet :

• 1500 chicks @ 0.42 m3/hour = 630m3/hour
• +-6 Air changes per hour.

Hope this helps.

[frank]

I'm not sure that the total fresh air volume required 0.175m3/s (630/3600) will be sufficient to deliver the total heat load needed when the outdoor temp is 2C.

You will need to carry out a fabric heat loss calc to see what the maximum heat load input will need to be.

If your room temp needs to be +35C with an ambient of +2C your delivery temperature will need to be at least 15K above the room target temp, which will give a dt of (+2 to +50) = 48K

So, for 0.175m3/s :

Q = Massflow x SHC x DT

Q = (0.175x1.28) x 1.012 x 48

Q = 10.88kW

The problem with using DX as the heat source is that it will struggle when the ambient temps are low on full fresh air supply.

[Proximity]

I'm not sure that the total fresh air volume required 0.175m3/s (630/3600) will be sufficient to deliver the total heat load needed when the outdoor temp is 2C.

You will need to carry out a fabric heat loss calc to see what the maximum heat load input will need to be.

If your room temp needs to be +35C with an ambient of +2C your delivery temperature will need to be at least 15K above the room target temp, which will give a dt of (+2 to +50) = 48K

So, for 0.175m3/s :

Q = Massflow x SHC x DT

Q = (0.175x1.28) x 1.012 x 48

Q = 10.88kW

The problem with using DX as the heat source is that it will struggle when the ambient temps are low on full fresh air supply.

@frank

Thanks for the insight and help.

I'll chat to the client and see if we can reduce the fresh air during low ambient conditions.

I'll keep you guys in the loop

Regards
Proximity