Modern automotive paint plants use water-bornefinishes to minimize the emission of volatile organiccompounds (VOC's) from the plant. In order toproduce a high quality finish, the temperature andrelative humidity in the spray booth must be closelycontrolled. An 'air house' is a small structure thathouses the components necessary to supply, filterand control the temperature and humidity of outsideair, which is then delivered to the spray booth. Forthis problem, design the necessarycomponent layout for an air house, and determinethe energy requirements to operate the air house.
The objective of this problem is to design an air house for a Jeep plant in Toledo, OH.
Somedesign constraints are:
- Summer Outside Air Design Condition: 88 °F (DB), 78 °F (WB)
- Summer Spray Booth Set-Point: 73 °F (DB), 64 °F (WB)
- Winter Outside Air Design Condition: 0 °F (DB), φ = 1.0
- Winter Spray Booth Set-Point: 73 °F (DB), 64 °F (WB)
- Air Flow Rate (Delivered): 110,000 cfm
You must include/answer at least the following:
1. Design constraints.
2. A schematic layout of the air house, identifying each component (Can be hand drawn. Does not need to be very nice or complex. Just illustrate the idea)
3. A psychrometric chart, illustrating the processes.
4. Condensate and/or Make-up water required, (lbm/hr)
5. Natural gas required, (scfm)
6. An estimate of hourly operating costs, based on energy consumption by component. Uselocal electricity and gas rates. (Note: Natural gas is priced per unit, where 1 unit = 100sft3.)
7. All assumptions, references andall detailed calculations
Estimating Operating Costs for Electricity - Electricity might be used to run the fan to draw air through the system, and also to run a chiller.
Things to consider:
- What is a typical COP for a commercial chiller?
- Typical air house pressure drop is about 4 in. water. How might you estimate fan power requirements?
When using Natural gas, Natural Gas Composition - Natural gas would typically be used to operate any pre-heat or reheat sections, due to the current cost advantage over electricity. For your energy calculations, use the following composition for natural gas:
Natural Gas Composition
Component: Percent by Volume:
CH481.0
C2H6 5.4
C3H8 4.8
C4H10 3.4
N2 5.4
Additional Information
Assume Paint house room dimensions are 100' x 100' x 18' (Length, Width, Height, ft)
Work in US units.
You may neglect things like heat loss/transfer from ducts to surrounding, paint house to surrounds, etc. Also you may neglect things like heat transfer from people to surrounding, machine to surroundings, or vice versa, etc.