Taking the Heat Off a Café – Part 2

The day is about to end and it is only now that I got the time to post a blog. I do not want to violate my self-imposed rule that I will blog everyday for this whole month so I really have to struggle to get true to myself. I made a fast review of my previous topics and maybe because of the heat striking us today and the days to come, the above topic is the first that comes to my mind.

The topic was first tackled in my blog here and my additional information on the subject will have to come from  “Keeping it Cool” thread in ULOP where I replied to a question and here it goes:

reviber wrote:
nakita ko yung P3xxx na industrial exhaust fan sa ace, chineck ko yung wattage (150W) tapos yung mga 12″ eh 50W P1xxx ang price. di ba parang mas maganda ang airflow and more energy efficient kung buy 2 or 3 nung non-industrial fan which would only consume 150W than a single industrial fan na 150W kasi pag konti naman ang tao pwede mo patayin yung ibang maliliit.

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Bien wrote:
hmm… in arithmetic, parang pwede. unfortunately, hindi ganun in actual. iba pa din talaga higop ng isang 150w sa tatlong 50w exhaust.

not sure why, but it may be because of the air resistance. a 50w motor is less able to resist air resistance than a 150w motor.

And this is mine . . .

Let me share my two-cents worth of idea on this subject. Actually, what we are discussing here is ventilation which is one of the item in HVAC (Heating, Ventilation and Air-Conditioning). Ventilation is a factor that is directly affected by the number of air changes occurring in a certain space per unit time. The higher the number of air changes the better the ventilation.

Applying the definition of ventilation to a lanshop, one must compute the total volume of space inside it, L x W x H (in cubic feet, during my time) and multiply by the number of air changes that you want per minute (example, a bar with many smoking customers need 10 air changes per minute) in order to arrive at the CFM (cubic feet per minute) rating of the exhaust fan needed.

Kung ang CFM ratings ng tatlong 50-watt exhaust fans ay parehas lang ng CFM rating ng isang 150-watt exhaust then okay lang na mag-substitute. Please note that CFM ratings are geometrically proportional to the diameter of an exhaust fan if the designs are the same.