Transient Heat Transfer of Automobile A/C System

1
Transient Heat Transfer of Automobile A/C System
December 2, 2005 UTC ENCH 435

• Prepared by Jason Hixson,
• Don Scott, and
  Michael Hickey

2
Objectives

• Perform material and energy balance.
• Observe pseudo steady-state transient behavior.

3
A/C Schematic
R-134a
R-134a
M3,T3
M4,T4
Recycled Air
Cooled Air
M2,T2
M1, T1
4
Variables Assumptions

• Entrance temperature
• Exit temperature
• Fan speed setting
• Velocity
• Engine RPM
• Time
• Fan Speed Setting

• Cp.24 BTU/lbR
• H37.39 BTU/lb
• H4100.9 BTU/lb
• T3T440 C
• Vent area19.4 in2
• Cab volume81 ft3
• m1m2
• m3m4

5
Energy and Material Balance

• Air Side
• ?Hm2Cp(T2-T1)
• ?HUA ?Tlm
• Refrigerant Side
• ?Hm3(H4-H3)
• m3m4

6
Setting 1
Setting 4
2000 RPMs
Setting 2
Setting 2
Setting 3
600 RPMs
Setting 1
Setting 3
Setting 4
7
2000 RPMs
600 RPMs
8
2000 RPMs
600 RPMs
9
2000 RPMs
600 RPMs
10
2000 RPMs
600 RPMs
11
600 RPMs
2000 RPMs
12
RECOMMENDATIONS

1. Look at measuring the power used by the system do
   determine impact on battery and alternator
   performance.
2. Look at the systems impact on gas mileage while
   running.

13

• QUESTIONS
• COMMENTS