CFD Chiller Venting Performance Development

This technical article addresses the continuous improvement project refining the venting system for the client's chiller core. Employing a four-stage vapour compression cycle, these chillers are integral to absorbing thermal energy from water, generating chilled drinking water. The efficiency of this process depends on the optimal rejection of heat, which is crucial for minimising the runtime of noisy and energy-intensive compressors. This article outlines the systematic approach taken to identify, analyse, and address inefficiencies in the existing venting system, culminating in a validated solution that significantly improves the overall unit efficiency.

Observations and Hypothesis

Observations of the current venting system revealed constrictions hindering effective heat rejection and an inefficient flow path within the chiller unit. A hypothesis was formulated, suggesting suboptimal handling of hot air, which prompted the initiation of a Computational Fluid Dynamics (CFD) study to delve into internal airflow characteristics.

Computational Fluid Dynamics Study

Prior to the CFD study, basic hand calculations were performed using known fan flow rates and cross-sectional areas to predict velocity disparities and stagnation points. These calculations guided the creation of a mesh for the CFD study, optimized for computational efficiency while accurately representing airflow dynamics. The results validated the initial hypothesis, indicating that the airflow was directly impacting the system's performance.

Proposed Solution and Validation

Based on the CFD study results, a new sheet metal vent design was proposed. This design aimed to prevent air from passing the hot tank through the coils, creating a stagnant section around the tank and reducing velocity disparities for a consistent airflow. The revised CFD simulation with the new vent geometry demonstrated the desired effects

Validation testing confirmed a reduced runtime for compressors to achieve the same cooling load, providing empirical evidence of the efficiency improvements brought about by the proposed modifications.

Conclussion

This technical article outlines a comprehensive approach to identify, analyze, and address inefficiencies in the venting system of a client's chiller core. The proposed solution, validated through rigorous testing and simulations, demonstrates a significant improvement in overall unit efficiency, paving the way for enhanced performance and reduced energy consumption.