Introduction

In 1965, Gary Moore co-founder of Intel predicted that the number of transistors located on a square inch of integrated circuit would double every eighteen months. This is often referred to as Moore’s Law. This prediction has been relatively correct to date. The exponential increase in processor speed associated with the increase in transistors has also resulted in higher processor power consumption. This power consumption results in rejected heat. Computer equipment manufacturers have at the same time installed more processors in smaller and smaller physical space compounding the amount of rejected heat in a given area.

In order to keep the components within the data processing equipment from overheating, the manufacturers use external ambient air as the heat rejection medium. In most applications this cooling air flow is generated by internal fans forcing cooling air from front to back, side to top or side to back of the equipment case. The lower the cooling air temperature entering the equipment case, the greater the heat transfer from the components to the existing air.

Traditional racks or cabinets housing this data processing equipment using traditional data room cooling methods have, until recently, provided adequate cooling. However, as the amount of heat rejection from a standard rack increased 2 or 3 KW, cooling problems began to develop. This problem is particularly noticeable (and measurable) near the top of a standard rack when ambient room cooling is provided from a raised floor air plenum.