Interesting science Rate analysis - HVAC Materials

The weight of the GI Sheet is based on Weight in Kg. 

So, if 0.56 mm GI sheet cost 2000 Rs. then, 0.8 mm cost = Rs. 2000x0.8/0.56

For plain insulation also, it takes the same formula as above. 

But, for Tube type insulation (weight)

= (pi x (d1+t1)^2 /4)- (pi x d1^2/4) x length x density

= pi/4(   d1^2+2d1t1+t1^2)-d1^2)x length x density

=pi/4(2d1t1+t1^2) x length x density

= length x density x pi/4 x t1 (2d1+t1)  

weight = constant x t1(2d1 +t1)    

Example, if we have to find the rate of 12 mm dia insulation of 19 mm thick, and if we know the rate of 6 mm insulation of 12 mm thick, then the rate of 19 mm thick insulation of 12 mm dia

=weight ratio x rate

=19(12x2+19)/12(2x6+12)

=817/288

19 mm thick insulation of 12 mm      =2.833 times the rate of 6 mm dia insulation of 12 mm thickness

When the thickness is very less, less than 1, then the rate is proportional to the thickness and dia of the pipe. In the case of copper pipe:

The cost of the copper pipe of 34 mm of 1.2 mm thickness, if 6mm pipe of 0.8 mm thickness has Rs. 80, = Rate of 6 mm dia x (34/6)x (1.2/0.8)

FAN Science

Two 150 CFM at 150 pascal = 300 CFM @ 150 Pascal (when used in parallel)= 150 CFM @ 300 Pascal (in series)

Using Fan laws, question may arise; 150 CFM fan @ 300 Pascal can deliver how many CFM @ 200 Pascal?

Description: Understanding and Applying the 3 Basic Fan Laws - Eldridge

Generally for the above problem, refer to the Fans curve diagram. But if we want to use the Fans Ideal equation Laws,  combining Fans law1 and Fans law 2

CFM2= CFM1(SP2/SP1)^(1/2)

CFM ∝ RPM

Static Pressure ∝ RPM2

So, if Static pressure is increased by Four times, then CFM is increased by 2 times. Static pressure doesn’t decrease in the proportion to the increase in CFM.

Power (in HP) ∝ Pressure (Static Pressure) X Volume (CFM)

But, What if both RPM is same. Static pressure and CFM remains same. So, having constant RPM means CFM and static pressure remains unchanged?

n general, the fan performance curve can be divided into three regions: the free delivery region, the normal operating region, and the surge region.

In the free delivery region, the fan is operating at low static pressure and high flow rate, the curve is linear. CFM ∝ 1/Static pressure

In the normal operating region, the fan is operating at moderate static pressure and flow rate, the curve will tend to be parabolic. CFM∝

Description: Straightening Out Fan Curves

In the surge region, the fan is operating at high static pressure and low flow rate, the curve will not be parabolic. It will be more like a straight line.

It is important to note that the fan curve should be provided by the manufacturer and not assumed to follow a parabolic equation.

 

1 HP motor used 600 Gram of Copper.

 

 

 

 

 

 

 

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