I have been in the field for over 10 years and have never heard of this term. I love this ❤
@ponkrapujari679
3 жыл бұрын
God bless you Jenny
@bmorbyustech7645
6 жыл бұрын
Thanks so much for the information so hard to find calculations explained online! Knowledge is great!
@sshah9563
6 жыл бұрын
very nice illustration, Thanks a lot!
@Na-hm2so
2 жыл бұрын
Very happy
@thomasvanhooser4890
4 жыл бұрын
Great training aid. Thank you.
@TitusHVAC
9 жыл бұрын
Thanks!
@sajeshsajespp6687
4 жыл бұрын
In hvac systems, ACH is calculated for the fresh air in the room? Considering the split ac, there is No outside air coming in the room and the example you showed that, extra water is poured in the existing filled water. This means fresh air quantities how much to be added or removed per hour in the room Is it right
@TitusHVAC
4 жыл бұрын
Air changes per hour generally refers to the volume of “ventilation” air passing through a space. The entire supply air mixture is assumed cleaner than the room air and thus fits within the definition of “ventilation” air. Certain applications use air changes per hour to quantify the amount of outside air passing through a space. For example ASHRAE Standard 170 requires that a total of four air changes with two of those being outside air be delivered to a patient room.
@mike777meridian
9 жыл бұрын
good illustration.
@arjunshetty7612
2 ай бұрын
Solar decathlon brought me here
@mmarsc2323
5 жыл бұрын
Is there a way to estimate the average air speed in a room, given the ACH and room geometry? In an idealised room where one entire wall is an inlet and the opposite wall is an outlet and there is constant air flow, I would imagine that the ACH * room length gives a good estimate of wind speed. Could I apply this logic to a different cross-ventilated space (where window placement/sizes are known), or is that too much of a stretch?
@TitusHVAC
5 жыл бұрын
While your example of average air velocity for a room with one wall as in an inlet and an opposite wall as an outlet is correct, it’s not possible to apply this same logic to an actual room. Room air distribution can be quite complicated. There are different types of air distribution, like fully-mixed systems that use ceiling diffusers or high sidewall grilles and there are fully-stratified systems that use displacement ventilation diffusers or underfloor air distribution. These systems can deliver air outside the occupied zone or inside the occupied zone. Discharge velocities from diffusers can vary wildly and there are many different types of discharge air patterns to choose from. In addition, the temperature of the supply air determines the effect of buoyancy and how the supply air will mix with room air. Even tools like computational fluid dynamics (CFD) software can yield incorrect results with regard to room air velocity if the discharge jet isn’t correctly modeled. I’ve often said that air distribution is more of an art than a science. If room air velocity is of critical importance, I recommend following industry guidelines with regard to diffuser selection and placement to avoid problems. Randy Zimmerman, Chief Engineer
@TitusHVAC
5 жыл бұрын
Room air distribution can be quite complicated. There are different types of air distribution, like fully-mixed systems that use ceiling diffusers or high sidewall grilles and there are fully-stratified systems that use displacement ventilation diffusers or underfloor air distribution. These systems can deliver air outside the occupied zone or inside the occupied zone. Discharge velocities from diffusers can vary wildly and there are many different types of discharge air patterns to choose from. In addition, the temperature of the supply air determines the effect of buoyancy and how the supply air will mix with room air. Even tools like computational fluid dynamics (CFD) software can yield incorrect results with regard to room air velocity if the discharge jet isn’t correctly modelled. I’ve often said that air distribution is more of an art than a science. If room air velocity is of critical importance, I recommend following industry guidelines with regard to diffuser selection and placement to avoid problems.
@ZEESHANUSTAD
3 жыл бұрын
What is mean by 4 air changes out of total minimum 20 air change? NABH Guidelines for OT 2018 says "FA required to be min 4 Air changes out of total minimum 20." I'm a bit confused. In my case for 2390 CFM and 972 vol I'm getting 147 ACH. How much fresh air to be considered in this case? Thanking you
@TitusHVAC
3 жыл бұрын
The term “FA” relates to the amount of fresh air that must be included in the total air supply. If 20 total air changes are required, this means 4 shall be outside air and the remaining 16 can be filtered recirculated air. To address your question, your calculation would be correct. If you were to supply 2,390 CFM to a space whose volume is only 972 ft3, that would equate to 147 total air changes. However, this would seem to be a very high airflow rate for such a small space. Assume your room height is 10 feet, the airflow rate would be some 24.5 CFM per square foot. Typical cooling loads require between 0.5 and 2 CFM per square foot. Conversely, a total air change rate of 20 would only require an airflow rate of 325 CFM in the room you describe. To determine the required airflow rate (CFM), multiply the room volume times its required air change rate, then divide by 60.
@ZEESHANUSTAD
3 жыл бұрын
@@TitusHVAC Addition of 4 FACH would help in creating +ve pressure Which is must in OTs, NOW my question is fresh ACH is min 4 out of min 20 Supply ACH, but how much Max FACH we can go upto. What is the basis we are adding fresh ACPH?
@TitusHVAC
3 жыл бұрын
@@ZEESHANUSTAD I would think you can make all 20 air changes (or even 24 as you suggest) fresh air but it has to be adequately filtered and there will likely be an energy penalty involve with its conditioning.
@g18210
6 жыл бұрын
How can you calculate the airflow in a window opening 1 m2 ( 1x1) ?
@TitusHVAC
6 жыл бұрын
I asked our Director of Technology. This is what he suggested. When running loads ASHRAE has suggestions for wind speed on the exterior of the building. They have one for summer and one for winter. You could take the windspeed and use it as a velocity through the window. All that being said that would be a conservative value (high) value for most normal days and would change for area and location. If there is no wind then I would guess little to no movement. Sustained winds in an area would probably be the best guess, national weather sites might have that information.
@joseguardado48
8 жыл бұрын
which software is that you're using, to make the illustration?
@TitusHVAC
8 жыл бұрын
+Jose Guardado I use the Explain Everything app on my iPad to do the drawings.
@fmepengineering3435
4 жыл бұрын
How to find out ACH for different areas ,like store and parking ??
@TitusHVAC
4 жыл бұрын
The number of air changes is always the volumetric airflow rate (in ft3 or m3 per hour) divided by the volume of the space. If you have an irregular sized shape (other than a cube) it may be a little harder to define the volume of the space but the relationship remains the same. ACH-1 = CFM x 60/ ft3 or m3/h / m3. We hope this helps.
@fmepengineering3435
4 жыл бұрын
@@TitusHVAC in this case we know CFM all ready, but if we don't know CFM and ACPH , then how to find out ? If you see Ashrae 62.1 , they given ACPH for different area for fresh air , but I wana to know about exhaust ...
@TitusHVAC
4 жыл бұрын
@@fmepengineering3435 Table 6.5 of Standard 62.1-2016 defines minimum exhaust rates for various applications such as parking garages but they are expressed in CFM/ft2 and not air changes per hour. In this case, the number of air changes can be calculated by the following equation: ACH-1 = CFM/ft2 x area (ft2) x 60 / Volume of space (ft3) That table recommends an exhaust airflow rate of 0.75 CFM/ft2. If the ceiling height of the garage is ten feet, this would equate to an air change rate of 4.5. The exhaust airflow rate prescribed by Standard 62.1 is thus independent of the space height, although it only applies when the parking garage does not have at least two walls whose open area is 50% or more.
@fmepengineering3435
4 жыл бұрын
@@TitusHVAC Yes there mentioned some information but at mean time in Ashrae 62.1 , they said store area exhaust ACPH can find by other standard. Have you other sources to find out ACPH, because all area and height no equal.
@TitusHVAC
4 жыл бұрын
@@fmepengineering3435 Standard 62.1 table 6.5 does not specify a separate exhaust rate for retail facilities. It does specify a breathing zone outdoor airflow rate and default occupancy for these spaces in Table 6.2.2.1. Note that Table 6.5 only applies to spaces where other contaminants override CO2 as the primary pollutant. Each space listed has some type of contaminant generation that requires a minimum exhaust rate to keep the contaminant level safe for the occupants. Although CO2 is not considered a dangerous contaminant, the level of CO2 should be controlled, thus the specification of breathing zone outdoor airflow rates in Table 6.2.2.1. As for the ventilation rate in the store, it is assumed that the supply and exhaust airflow rate will be the same. In that case you must use Table 6.2.2.1 to determine the space minimum outdoor airflow rate and then calculate the air changes as follows: Minimum breathing zone airflow rate per person (Rp): 7.5 CFM (3.8 L/s) Minimum breathing zone airflow rate per area (Ra): 0.12 CFM/ft2 (0.6 L/s-m2) Minimum outdoor airflow rate = Rp x #occupants + Ra x area You then calculate the minimum outdoor air change rate as follows: Minimum outdoor air change rate = CFM x 60/(space volume, ft3) or L/s x 3.6/(space volume, m3) You need to calculate this for every enclosed space, thus you need the height of each space to calculate its volume. If you have a single space with multiple heights, the average height can be used. In reality though there is no need to calculate the air change rate for a store as Standard 62.1 prescribes the minimum outdoor airflow rate as a finite volumetric flow rate.
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