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[Chad]

I have a question about blowers. We have several pneumatic conveying lines for our product, plastic pellets (400-1200 micron in size). I am trying to cool the conveying air before the product is dropped into the line. The problem is the air is very hot coming from the blowers, but varies from blower to blower.

The blowers are outside in the open and sitting next each other. One will heat the air up to 180 degF the other 145 degF. I don't understand why the air is getting so hot in the first place and secondly, why it would vary from pump to pump?

The pumps are:

1) DuroFlow, model 4509. Motor RPMs 1750, Motor Sheave Dia: 12.5, Blower Sheave Dia: 8.0 in., blower speed (calculated): 2734, 550 CFM <- this one runs the coolest. (air is 120 degF)
2) DuroFlow, model 4509. Motor RPMs 1750, Motor Sheave Dia: 12.5, Blower Sheave Dia: 7.1 in., blower speed (calculated): 3081, 600 CFM <- this one runs the hottest. (air is 140 degF)
3) DuroFlow, model 4509. Motor RPMs 1750, Motor Sheave Dia: 12.5, Blower Sheave Dia: 8.5 in., blower speed (calculated): 2573, 530 CFM (air is 125 degF)

Another set of pumps:

1) DuroFlow, model 4512 VT. Motor RPMs 1770, Motor Sheave Dia: 11.05 in., Blower Sheave Dia: 6.32 in., blower speed (calculated): 3098, 820 CFM. (air is 140 degF)
2) Big Jack, model A412C. Motor RPMs 1770, Motor Sheave Dia: 11.05 in., Blower Sheave Dia: 6.32 in., blower speed (calculated): 3098, 800 CFM <- runs the hottest (air is 180 degF)
3) Big Jack, model A412C. Motor RPMs 1770, Motor Sheave Dia: 11.05 in., Blower Sheave Dia: 6.32 in., blower speed (calculated): 3098, 825 CFM. (air is 155 degF)

Thanks,

Chad

(I graduated from school over 4 years ago, but this is my first job that I actually have to use any engineering.)

[pleckner]

Blowers are like compressors. They increase the air pressure from some inlet condition (atmospheric perhaps in your case) to some required amount. This increase in pressure will increase the air temperature. Some factors that influence this are pressure ratio (outlet pressure to inlet pressure) and blower efficiency.

You don't give your process conditions so we can't go through the exercise of calculating the temperature rise but you can easily do it yourself. All you need is Perry's Chemical Engineering Handbook and look up blowers/compressors. You can also do a Google search on blowers/compressors. Better yet, go to the vendor's website.