Excessive heat buildup, at best, shortens the life of networking equipment. At worst, it shuts down equipment permanently. Most IT professionals believe in keeping the IT room cool. If the room temperature is lower, the internal cabinet temperature will be lower, as well.
With this approach, problems--including condensation and potential equipment corrosion when any dust is added--can cause higher operational costs of oversized cooling equipment and additional energy costs.
Key is to channel or duct cool air to the equipment and provide a path for heated air to leave the cabinet. Nearly all network equipment draws in cool air in the front while exhausting hot air out the back. Equipment is stacked into the cabinet vertically, where cool, dry air must be available at the inlet to each piece, and exhaust air must be actively removed from the back of each. Testing several cabinet configurations shows which one offers the best thermal profile for network equipment:
Configuration #1. Cabinets with solid front and back doors, with fans off or without fans, performed worst. The equipment is not provided with cool air to its intakes, nor with an outlet for heated air. Air passing through the cabinet is already heated by adjacent equipment, then trapped in the cabinet top. With perforated front and back doors, a boundary along the perforated surface acts as a barrier to airflow in the absence of a clear channel for heated air to escape. Airflow for both is dependent on naturally rising warm air, due to heat generated within the cabinet. The amount of airflow or volume of cool air is limited and results in higher temperature as compared to the other cases. Configuration #2. Fully perforated front and rear doors work with low heat loads, but simply adding fans is not the answer for increased loads. Fully perforated doors, with or without fans, yield nearly the same performance. The perforations permit cool air in the front and heated air out the back, allowing maintenance of an acceptable temperature. Airflow improves by adding a vented top. When more equipment is added and the heat load intensifies, just adding fans will not maintain the same acceptable inside air temperature.
With fully perforated front and rear doors with fans running, the air stream is short circuited--drawing from a region with least resistance, the air through the top of the perforated doors. The cool air is not distributed evenly to all of the equipment, and hot spots occur in the equipment mounted in the center of the cabinet.
Configuration #3. The cabinet design can direct the cool air to cabinet hot spots and direct the warm air out of the cabinet. Fans dramatically increase the cooling performance of a solid-door configuration. The solid surrounding sides of the cabinets, along with running fans, draw in cool air from the floor and provide a path for heated air to escape. A limited amount of cold air can be drawn in between the floor and the cabinet's base.
Configuration #4. Moving air through a cabinet, from bottom to top, results in the lowest internal cabinet temperatures. Perforating the entire front door and the lower part of the back door, combined with fans mounted to the top, clearly provides the best scenario for cooling.
Cool air is drawn through the perforated front door, into the network equipment, where it is heated and exhausted through the rear of the servers. Heat is dispersed by the fan-induced volume of air entering through the lower perforated area in the rear door, passing over all of the heat-producing equipment and exhausting out the top of the enclosure. The chimney effect is the most effective way to keep network equipment cool inside a cabinet.
Many HVAC systems are positioned directly above the cabinets, which simplifies installation of cabinet exhaust ducts and takes advantage of the existing room HVAC system by ducting exhausted air to the return vents to be conditioned and recycled.
The method of cooling equipment is dependent upon how many servers are installed in the cabinet and their location. Different airflow patterns and hot spots will exist if the servers are concentrated in one section vs. being evenly distributed within the cabinet. Different scenarios require different configurations to give the best results
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