A cooling system load is 96,000 BTUh sensible. How much chilled air is required to satisfy the load if the system is designed for a 20°F temperature rise? How much flow is required for 15°F rise?

Respuesta :

Answer:

For [tex]20^{\circ}[/tex] - 5.556 lb/s

For [tex]15^{\circ}[/tex] - 7.4047 lb/s

Solution:

As per the question:

System Load = 96000 Btuh

Temperature, T = [tex]20^{\circ}[/tex]

Temperature rise, T' = [tex]15^{\circ}[/tex]

Now,

The system load is taken to be at constant pressure, then:

Specific heat of air, [tex]C_{p} = 0.24 btu/lb ^{\circ}F[/tex]

Now, for a rise of [tex]20^{\circ}[/tex] in temeprature:

[tex]\dot{m}C_{p}\Delta T = 96000[/tex]

[tex]\dot{m} = \frac{96000}{C_{p}\Delta T} = \frac{96000}{0.24\times 20} = 20000 lb/h = \frac{20000}{3600} = 5.556 lb/s[/tex]

Now, for [tex]15^{\circ}[/tex]:

[tex]\dot{m}C_{p}\Delta T = 96000[/tex]

[tex]\dot{m} = \frac{96000}{C_{p}\Delta T} = \frac{96000}{0.24\times 15} = 26666.667 lb/h = \frac{26666.667}{3600} = 7.4074 lb/s[/tex]