Bypass Airflow
What is Bypass Airflow in a Data Centre?
Bypass airflow in a data centre refers to the phenomenon where conditioned (cooled) air meant to cool IT equipment bypasses the intended equipment and flows into other areas of the data centre, such as return air plenums, ceiling spaces, or directly back to the cooling units. This air does not contribute to cooling the IT equipment, leading to inefficiencies in the cooling process.
Bypass airflow typically occurs due to poor airflow management, such as gaps in raised floors, improperly sealed cable openings, or unsealed spaces between equipment racks. This results in cool air mixing with hot air, reducing the effectiveness of the cooling system and often leading to higher energy consumption as the cooling units work harder to maintain the desired temperatures.
What are the impacts of Bypass Airflow on Data Centre efficiency?
1. Increased energy consumption:
Bypass airflow reduces the efficiency of cooling systems, as cool air that bypasses the equipment needs to be recirculated or additional cooling is required to compensate for the lost cooling capacity. This leads to increased energy consumption and higher operational costs.
2. Hot spots and equipment overheating:
When cool air bypasses the IT equipment, some areas may not receive adequate cooling, resulting in hot spots. These hot spots can lead to equipment overheating, reduced performance, or even hardware failure, impacting the reliability of the data centre.
3. Reduced cooling efficiency:
The mixing of cool and warm air due to bypass airflow reduces the overall cooling efficiency of the data centre. The cooling system needs to work harder to achieve the desired temperature, leading to increased wear and tear on cooling equipment and potentially shortening its lifespan.
4. Higher operational costs:
Inefficient cooling due to bypass airflow results in higher energy usage, directly increasing operational costs. This can also affect the data centre’s Power Usage Effectiveness (PUE), a key metric used to measure the efficiency of data centre operations.
5. Environmental impact:
Increased energy consumption not only raises costs but also contributes to a larger carbon footprint, making the data centre less environmentally friendly.
What are the strategies to reduce Bypass Airflow?
1. Proper sealing of raised floors:
Ensure that all cable openings, gaps, and penetrations in raised floors are properly sealed to prevent cool air from escaping into spaces where it is not needed. Use grommets and brush strips to seal cable openings effectively.
2. Implementing hot and cold aisle containment:
Hot and cold aisle containment strategies physically separate the cool air (cold aisles) from the warm air (hot aisles). This containment prevents the mixing of air, ensuring that cool air reaches the equipment and warm air is directed back to the cooling units.
3. Use of blanking panels:
Install blanking panels in server racks where there are empty slots. This prevents cool air from flowing through unused rack spaces and bypassing the equipment, directing it instead to where it is needed.
4. Optimising floor layout and airflow management:
Properly design the data centre layout to optimise airflow paths. Place perforated tiles only in cold aisles to ensure cool air is directed towards the front of the server racks and not dispersed elsewhere.
5. Sealing cable entries and unused openings:
Seal all cable entry points and any unused openings in racks, walls, and floors to prevent air from bypassing the IT equipment. This can be done using foam gaskets, blanking panels, or other sealing materials.
6. Installing airflow management devices:
Use airflow management devices such as directional airflow panels, underfloor baffles, and containment curtains to guide cool air to where it is needed most and prevent it from bypassing the equipment.
7. Monitoring and adjusting airflow:
Regularly monitor airflow patterns and temperatures in the data centre using sensors and thermal imaging. Adjust the placement of perforated tiles, containment systems, and cooling unit settings to optimize airflow and reduce bypass.
8. Using Variable speed fans:
Implement variable speed fans in cooling units that can adjust their speed based on the actual cooling demand. This helps in optimising airflow and reducing bypass, as the fans will not push more air than necessary.
9. Pressure management:
Control the pressure within the raised floor plenum to ensure that cool air is evenly distributed and does not escape through unintended openings. Adjusting the plenum pressure can help manage airflow more effectively.
10. Regular maintenance and audits:
Conduct regular maintenance and airflow audits to identify areas where bypass airflow may be occurring. Address any issues promptly to maintain optimal cooling efficiency.
