Calculating Ventilation Effect Watts in a Room

In summary, the conversation discusses the use of an equation to calculate the effect in watts of a ventilation system in a room. The equation is: \dot Q = \dot V \cdot 0,335 \cdot \left( {T_A - T_O } \right), where 0,335 represents the Cp of air and TA and TO are the temperatures of the air entering and outside the room, respectively. It is mentioned that the units should be checked to ensure accuracy, as the left and right sides of the equation do not match. The possibility of changing from volume flow to mass flow is also discussed.
  • #1
TSN79
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I want to calculate how much effect in Watts a ventilation system brings into a room. Will it be correct to use the following equation for this:

[tex]
\dot Q = \dot V \cdot 0,335 \cdot \left( {T_A - T_O } \right)
[/tex]

where 0,335 is actually the Cp of air derived from [itex]{{1005} \over {3600}} \cdot 1,2[/itex]
TA is the temperature the air enters the room with, and TO is the outside temp.

If the air enters the room with a lower temp than the room, how can the energy needed to heat up this air to room temp be taken into account?
 
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  • #2
I would think that should work, however, check your units. On the left you have watts, or J/s, on the right you have (m^3/s)(J/kgK)(K) giving you...well not what your looking for. I'm pretty sure you need to change your volume flow to mass flow.
 
  • #3


Yes, the equation you have provided is commonly used to calculate the ventilation effect in watts in a room. The value of 0.335 is the specific heat capacity of air, which takes into account the energy required to heat up the air to room temperature. This equation assumes that the air entering the room has the same temperature as the outside temperature.

If the air entering the room has a lower temperature than the room, then the energy needed to heat up the air to room temperature would need to be taken into account separately. This can be done by calculating the specific heat capacity of the air at the lower temperature and using that value in the equation. Alternatively, you can also subtract the energy needed to heat up the air from the total ventilation effect calculated using the given equation.

It is important to accurately calculate the ventilation effect in watts in a room to ensure proper ventilation and maintain a comfortable indoor environment. Other factors such as air flow rate, humidity, and air quality should also be considered when designing a ventilation system.
 

1. How do you calculate the ventilation effect watts in a room?

To calculate the ventilation effect watts in a room, you will need to know the volume of the room in cubic feet, the air change rate (ACR) in air changes per hour, and the specific heat of air. The formula for calculating ventilation effect watts is: ACR x Volume x 1.08 x (Temperature difference between supply and exhaust air).

2. What is the purpose of calculating ventilation effect watts in a room?

Calculating ventilation effect watts helps to determine the amount of heat that is being removed from a room by the ventilation system. This information is important for determining the appropriate size and type of heating and cooling system needed for the room.

3. How does the air change rate affect ventilation effect watts?

The air change rate (ACR) is a measure of how many times the air in a room is replaced with fresh air in an hour. The higher the ACR, the more ventilation effect watts will be needed to maintain a comfortable temperature in the room.

4. What factors can impact the ventilation effect watts in a room?

There are several factors that can impact the ventilation effect watts in a room, including the size and shape of the room, the number of occupants, the type of ventilation system, and the outdoor temperature.

5. Is there a standard or recommended ventilation effect wattage for a room?

There is no standard or recommended ventilation effect wattage for a room, as it can vary depending on the factors mentioned above. It is important to consult with a professional to determine the appropriate ventilation effect watts for a specific room.

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