Calculating Ventilation Effect Watts in a Room

[TSN79]

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:

$$\dot Q = \dot V \cdot 0,335 \cdot \left( {T_A - T_O } \right)$$

where 0,335 is actually the Cp of air derived from ${{1005} \over {3600}} \cdot 1,2$
T_A is the temperature the air enters the room with, and T_O 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?

 

[minger]

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.

 

[ravenprp]

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.