14 the enclosures 14 are closely spaced vertically e g tenths of an inch separation and have a horizontal box or u201c pizza box u201d form many enclosures 14 are typically mounted in the rack 10 for example each enclosure 14 may be less than 17 inches wide 10 inches deep and 1 7 inches high and as many as 44 enclosures 14 can be provided in a seven foot high rack 10 the enclosures 14 are cooled by generating an inlet airflow solid arrows into each enclosure from one side of the enclosure 14 and exhausting heated air dashed arrows pointing to the right out the opposite side of the enclosure 14 in the illustration a wall 18 located close to the rack 10 near the rear of the enclosures 14 obstructs the heated exhaust airflow in another arrangement racks are placed back to back resulting in heated exhaust airflows that are incident on other enclosures 14 in either arrangement the front to rear airflow is restricted and the enclosures 14 cannot be maintained at an acceptable temperature cooling is achieved instead by providing the inlet airflow solid arrows through the front of the enclosure 14 and exhausting the heated airflow dashed arrows pointing to the left back through the front of the enclosure 14 advantageously the thermal management apparatus of the present invention does not result in a.