Conversion Factors

[ab12cd]

Converting l/s to kg/hr for air.

Info given is 23 l/s of air at 15C and 4 barg.

To convert 23 l/s to SCFM you multiply by 2.12 = 50.6ft3/min. 50.6 x 0.02831 = 1.43 m3/min.

Mass = D x V = 1.29 x 1.43 = 1.8kg/min = 110 kg/hr

Does this seem correct?

 

[saxon]

ab12cd, Why ar you converting from metric to english then to back to metric? Run the conversion in the same system.

l/s x 3600 = l/hr

l/hr x d = kg/hr

where:
d: gas density in kg/l @ 15c & 4 barg

 

[EGT01]

I agree with Saxon, I don't know why are you not using common conversion factors for metric
1 m3 = 1000 lit
except that your incorrectly trying to convert your actual flow to flow at standard conditions.

First, you need to be sure of what you are calling you standard conditions. Standard conditions for the metric system is generally taken as 0°C, 1 atm versus the English system of 60°F, 14.7 psia, the difference being the reference temperature.

Your conversion from l/s to ft3/min is essentially correct depending on the rounding of your conversion factor but this conversion is not to SCFM but rather actual cfm (ACFM). Your conversion from ft3/min to m3/min is essentially correct again depending on the rounded accuracy of your conversion factor but your resulting flow in m3/min is not standard or normal m3/min (Nm3/min) but rather actual m3/min.

Though you don't indicate the units for air density, it appears that you are using the standard denisty of air at 0°C, 1 atm. Therefore, your final Mass = D x V calculation is not correct since what you are doing is multiplying actual volumetric flow rate by the standard density. You need to either correct the standard density to actual flow conditions or correct the actual volumetric flow to standard conditions by using the ideal gas relationships.

 

[TD2K]

ab12cd, you sure make it difficult.

If the 23 litre/sec is the volumetric flow at 15C and 4 barg, I would determine the density of the air at these conditions and multiply by the flow rate, that will give you mass per time.

If the 23 litre/sec is at standard or normal conditions, I would again determine the density at those standard or normal conditions and get my mass flow.

 

[patrickraj]

Calculate density in lb/cu.ft as follows:
(4/.0689+14.7)*144*29/1545/(15*1.8+492)= .3789lb/cu.ft

Calculate flow in cu.ft/hr as follows:
23*3600/1000*35.31= 2923.7cu.ft/hr
Flow= .3789*2923.7 lb/hr
= 1107.8lb/hr
= 502.5kg/hr

Hope this solves your plm.