The design of air conditioning plants for combustion air has been discussed in Chapter 5. The design of an air conditioned chamber for the testing of complete vehicles is a very much larger and more specialized problem. Figure 18.3 is a schematic drawing of such a chamber, built in the form of a recirculating wind tunnel so that the vehicle on test, mounted on a chassis dynamometer, can be subjected to oncoming air flows at realistic velocities, and in this particular case over a temperature range from +40 to −30?C