CFD Assessment of Heat Pump Exhaust-Air Recirculation
A CFD-based assessment of exhaust-air recirculation within an open-top heat pump plant room, examining how equipment loading, wind speed and wind direction influence airflow around the heat pump intakes.
Evaluating exhaust recirculation in a confined plant arrangement
The project involved an open-top plant room containing six heat pump units arranged within a partially enclosed space.
The primary engineering concern was whether discharged air could return toward the heat pump intakes and adversely affect equipment performance.
CFD was used to examine airflow interaction between the heat pump exhaust plumes, surrounding walls, louvred openings and external wind.
Testing equipment performance across changing wind conditions
Multiple operating scenarios were evaluated to understand how exhaust behavior changed with equipment load and external wind conditions.
Both full-load and part-load operation were assessed together with different wind directions and wind speeds.
Exhaust Plume Behavior
CFD was used to track how discharged air moved upward and away from the heat pump fan banks.
Wind Interaction
Different external wind conditions were assessed to identify plume deflection, downwash and local recirculation.
Intake Conditions
Conditions near the heat pump intakes were reviewed to identify units most susceptible to exhaust-air recirculation.
Localised recirculation without a plant-wide airflow problem
The simulations showed that the open-top configuration provided an effective primary discharge path for heat pump exhaust air.
No severe plant-wide exhaust recirculation was identified. Localised recirculation was observed under selected operating and wind conditions, with units near the louvred wall showing the greatest sensitivity.
Wind direction and speed influenced plume behavior, highlighting the importance of considering surrounding airflow rather than assessing the heat pumps in isolation.
CFD-supported assessment of plant-room robustness
The CFD study showed that the overall plant-room arrangement was suitable for the assessed operating conditions, with no severe plant-wide recirculation identified.
The analysis also identified the locations and environmental conditions most likely to produce local exhaust-air interaction, providing useful guidance for targeted airflow improvements.
Minor refinements to louvre orientation or local airflow control could further improve separation between heat pump discharge and intake paths and increase operational robustness.