The goal of an air conditioning test facility is to simulate the impact of an ambient heat load on the power requirements of the vehicle's air conditioning compressor while operating on a specific driving cycle. The environmental facility control elements that are discussed are ambient air temperature and humidity, minimum test cell size, solar heating, and vehicle frontal air flow.
(a) Ambient air temperature.
(1) Ambient air temperature is controlled, within the test cell, during all phases of the air conditioning test sequence to 95 ±2 °F on average and 95 ±5 °F as an instantaneous measurement.
(2) Air temperature is recorded continuously at a minimum of 30 second intervals. Records of cell air temperatures and values of average test temperatures are maintained by the manufacturer for all certification related programs.
(b) Ambient humidity.
(1) Ambient humidity is controlled, within the test cell, during all phases of the air conditioning test sequence to an average of 100 ±5 grains of water/pound of dry air.
(2) Humidity is recorded continuously at a minimum of 30 second intervals. Records of cell humidity and values of average test humidity are maintained by the manufacturer for all certification related programs.
(c) Minimum test cell size.
(1) The recommended minimum environmental exhaust emission test cell size is width 20 feet, length 40 feet, and height 10 feet.
(2) Test cells with smaller size dimensions may be approved by the Administrator if it can be shown that all of the ambient test condition performance requirements are satisfied.
(d) Solar heat loading.
(1)
(i) Acceptable types of radiant energy emitters that may be used for simulating solar heat load are:
(A) Metal halide;
(B) Quartz halogen with dichroic mirrors; and
(C) Sodium iodide.
(ii) The Administrator will approve other types of radiant energy emitters if the manufacturer can show they satisfy the requirements of this section.
(2) The height of the minimal cell size will dictate the type of radiant energy source that will satisfy the spectral distribution and uniformity definitions of this section.
(3) Radiant energy specifications.
(i) Simulated solar radiant energy intensity is determined as an average of the two points measured at:
(A) Centerline of the test vehicle at the base of the windshield.
(B) Centerline of the vehicle at the base of the rear window (truck and van location defined as bottom of vertical window or where an optional window would be located).
(ii) The radiant energy intensity set point is 850 ±45 watts/square meter.
(iii) The definition of an acceptable spectral distribution is contained in the following table:
Definition of the Spectral Distribution
| Band width (nanometers) | Percent of total spectrum |
|
|---|---|---|
| Lower limit (percent) | Upper limit (percent) | |
| <320 | 0 | 0 |
| 320-400 | 0 | 7 |
| 400-780 | 45 | 55 |
| >780 | 35 | 53 |
(iv) The angle of incidence of radiant energy is defined as 90 degrees from the test cell floor.
(v) The requirements for measuring the uniformity of radiant energy are:
(A) The radiant energy uniformity tolerance is ±15 percent of the radiant energy intensity set point of 850 watts/square meter.
(B) The uniformity of radiant energy intensity is measured at each point of a 0.5 meter grid over the entire footprint of the test vehicle at the elevation of one meter including the footprint edges.
(C) Radiant energy uniformity must be checked at least every 500 hours of emitter usage or every six months depending on which covers the shorter time period; and every time major changes in the solar simulation hardware occur.
(vi) The radiant energy intensity measurement instrument specifications (minimum) are:
(A) Sensitivity of 9 microvolts per watt/square meter;
(B) Response time of 1 second;
(C) Linearity of ±0.5 percent; and
(D) Cosine of ±1 percent from normalization 0-70 degree zenith angle.
(e) Vehicle frontal air flow. The Administrator will approve frontal air flow based on “blower in box” technology as an acceptable simulation of environmental air flow cooling for the air conditioning compressor and engine, provided the following requirements are satisfied.
(1) The minimum air flow nozzle discharge area must be equal or exceed the vehicle frontal inlet area. Optimum discharge area is 18 square feet (4.25 × 4.25), however, other sizes can be used.
(2) Air flow volumes must be proportional to vehicle speed. With the above optimum discharge size, the fan volume would vary from 0 cubic feet/minute (cfm) at 0 mph to approximately 95,000 cfm at 60 mph. If this fan is also the only source of cell air circulation or if fan operational mechanics make the 0 mph air flow requirement impractical, air flow of 2 mph or less will be allowed at 0 mph vehicle speed.
(3) The fan air flow velocity vector perpendicular to the axial flow velocity vector shall be less than 10 percent of the mean velocity measured at fan speeds corresponding to vehicle speeds of 20 and 40 mph.
(4)
(i) Fan axial air flow velocity is measured two feet from nozzle outlet at each point of a one foot grid over the entire discharge area.
(ii) The uniformity of axial flow tolerance is 20 percent of the fan speeds corresponding to vehicle speeds of 20 and 40 mph.
(5) The instrument used to verify the air velocity must have an accuracy of 2 percent of the measured air flow speed.
(6) The fan discharge nozzle must be located 2 to 3 feet from the vehicle and 0 to 6 inches above the test cell floor during air conditioning testing. This applies to non-wind tunnel environmental test cells only.
(7) The design specifications discussed in paragraphs (e)(1) through (e)(5) of this section must be verified by the manufacturer prior to conducting certification air conditioning tests.
[61 FR 54897, Oct. 22, 1996, as amended at 70 FR 40434, July 13, 2005]