Final Examination in ME 413 (Problem-Solving - Part 1)

Calculate the specific volume of an air-vapor mixture in cubic meters per kilogram of dry air when the following conditions prevail: t = 30°C, ω = 0.015 kg/kg, and Pt = 90 kPa.

• 0.69 m³/kga
• 0.89 m³/kga
• 0.79 m³/kga
• 0.99 m³/kga

A 4 m x 4 m x 4 m room has a relative humidity ratio of 80%. The pressure in the room is 120 kPa and temperature is 35°C (Psat = 5.628 kPa). What is the mass of vapor in the room? Use Rvapor = 0.4615 kN-m/kg- K.

• 2.03 kgv
• 5.03 kgv
• 3.03 kgv
• 1.03 kgv

The mass of an outside air at 50°C in an air conditioning unit is 60 kg. Find the temperature after mixing if the outside air mixed with 40 kg with recirculated air at 35°C.

• 55°C
• 65°C
• 44°C
• 35°C

In an air conditioning system, if the re-circulated air is three times the outside air and the mass of supply air is 20 kg/s, what is the mass of the outside air?

• 5 kg/s
• 5.5 kg/s
• 6 kg/s
• 0 kg/s

A room being air conditioned is being held at 25°C dry bulb and 50% relative humidity. A flow rate of 5 m³/s of supply air at 15°C dry bulb and 80% RH is being delivered to the room to maintain that steady condition at 100 kPa. What is the sensible heat absorbed from the room air in kW?

• 60.5 kW
• 88 kW
• 60.5 hP
• 214.2 kW

If the latent and sensible heat loads are 20 kW and 80 kW respectively, what is the sensible heat ratio?

• 1
• 0.5
• 2
• 0.8

In an auditorium maintained at a temperature not to exceed 24°C and relative humidity not to exceed 60%, a sensible heat load of 132 kW and 78 kg of moisture per hour to be removed. Air is supplied to the auditorium at 18°C. How many kilograms of air must be supplied per hour?

• 79200 kg/hr
• 79002 kg/hr
• 97200 kg/hr
• 72900 kg/hr

Determine the approximate load on a cooling tower if the entering and leaving temperatures are 96°F and 88°F, respectively and the flow rate of the water over the tower is 30 gpm.

• 2000 kW
• 2000 hP
• 2000 BTU/min
• 2000 BUT/s

The natural draft cooling tower has a 400 ton heat rejection load. The temperature of the water entering the cooling tower is 90°F and leaving at 82°F. Compute the approach, range and cooling tower efficiency when the outdoor wet-bulb temperature is 75°F.

• R = 8°C, A = 7°C, e = 53.33%
• R = 8°C, A = 8°C, e = 53.33%
• R = 7°C, A = 7°C, e = 53.33%
• R = 7°C, A = 8°C, e = 53.33%

Copra enters a dryer containing 60% water and 40% of solids and leaves with 5% water and 95% solids. Find the weight of water removed based on each pound of original product.

• 0.85 lb
• 0.24 lb
• 0.58 lb
• 0.42 lb