Calculation of large meeting room air conditioning systems (High Density Occupancy)

Guidelines For designing air conditioning systems for large meeting rooms with many people (High Density Occupancy)

We cannot use the area multiplication formula (Rule of Thumb) like a normal bedroom because of "heat load from people" and "

Fresh Air" is the most important variable. Here is how to calculate step by step. For meeting rooms 1,000 sq m., height 5 meters, capacity 800 people.

Step 1: Isolate the Heat Source (Heat Load Breakdown)
We need to calculate the main load 3 as follows:
1. Load from area and structure. (Transmission & Solar Load)Think of heat passing through walls, glass, roofs, and lights.
 * Meeting room standard values: approximately 800 - 900 BTU/sq m (due to high ceilings and lots of lights)
 * Calculate: 1,000 \text{ sq m} \times 850 \text{ BTU} = \mathbf{850,000 \text{ BTU/hr}}
2. Occupancy LoadPeople sitting in meetings have heat both in the senses (Sensible) and humidity (Latent).
 * Average heating value per person: 450 - 500 BTU/person (for listening to lecture activities)
 * Calculate: 800 \text{ people} \times 500 \text{ BTU} = \mathbf{400,000 \text{ BTU/hr}}
3. Load from fresh air (Fresh Air / Ventilation Load) is very important.According to the standard, good air must be added to reduce CO2 and not make people sleepy.
 * Aeration rate: approximately 15-20 CFM per person (or calculated according to )
 * Air volume: 800 \text{ people} \times 15 \text{ CFM} = 12,000 \text{ CFM}
 * Cooling load (approximate): Fresh Air wind 1 CFM, load approximately 40-50 BTU (from 35°C reduced to 25°C)
 * Calculate: 12,000 \text{ CFM} \times 45 \text{ BTU} = \mathbf{540,000 \text{ BTU/hr}}

Step 2: Total Cooling Load
Convert units to Tons of Refrigeration (TR):
> Basic Summary: You need a cooling system approximately 150 - 160 tons (to allow for Safety Factor 5-10%).
 
Step 3: Select the type of air conditioning system (System Selection)
For a size of 150-160 tons and a height area of 5 meters, it is not recommended to use a general hanging or wall type air conditioner. The appropriate choice is:
 * Chiller system (Water Cooled/Air Cooled):
   * Run cold water pipes into the AHU (Air Handling Unit).
   * Advantages: Controls humidity very well. Save electricity in the long term Suitable for buildings with other areas that also use air conditioners.
 * VRF / VRV (Variable Refrigerant Flow) system:
   * Use a hot coil connected to a cooling coil connected to an air duct (Ceiling Ducted).
   * Advantages: Easier to install than Chiller, no water system required. Controlled zones in detail
 * Package Unit (Ducted Split System):
   * Large air conditioner, floor-standing or ceiling-mounted cabinet, connected to air ducts
   * Advantages: Cheaper than the first two types. But the sound may be louder.
Additional suggestions from an engineer's perspective
 *Aeration system (OAU/PAU):
 * Due to the very high Fresh Air load (540,000 BTU), do not mix outside air directly with the inside air conditioner. Because the air conditioner will cut off often and the humidity will be high. (Sweating in the air conditioned room)
 * Solution: You must install an OAU (Outdoor Air Unit) to cool and dehumidify the outside air before sending it into the room.
 * Air Distribution:
 * Rooms that are 5 meters tall must use a Jet Diffuser or Nozzle to shoot cool air to reach the person or use a duct to push it down.
 * Zoning:
   * The air conditioner should be divided into several sets (such as AHU 4, each 40 ton) to accommodate the case where not all people use the room. Or in the case of a broken machine, the whole room won't be heated.