CFD Analysis of Demand Control Ventilation (DCV) for Laboratory Spaces

Kishor Khankari, AnSight LLC

Often high airflow rates or air change rates per hour (ACH) are specified to cover the risk of chemical exposure in laboratory spaces. High ACH often incurs high energy demands for laboratories. Laboratory ventilation rates can be reduced by using a demand-controlled ventilation (DCV) system that regulates the ACH based on the contaminant concentration in the laboratories monitored by the sensors. Several factors can affect the DCV performance, including the sensor locations, sampling interval, contaminant generation rate, and airflow patterns in the space.

This presentation, with the help of Computational Fluid Dynamics (CFD) analysis, will evaluate the performance of DCV for typical laboratory space. This study investigates the impact of number and location contaminant sensors and the sampling frequency on the exposure. Time-varying concentration levels are predicted at the face level of three occupants located at three different locations in the lab, as well as in the exhaust duct. Based on these concentrations the time-varying chemical exposure (dose) for each occupant is calculated. The ventilation effectiveness of the HVAC system is analyzed with the help of two non-dimensional indices: Spread Index (SI)TC and Purge Time (PT)TC.

The analysis results will be presented with insightful animations showing the progression and movement of contaminant cloud in the space.

Learning Objectives

• Understand the impact of airflow patterns on the performance of Demand Control Ventilation (DCV) for laboratories;
• Understand the impact of sensor locations on the relative exposure levels (dose) of occupants with demand control ventilation;
• Understand the definitions of Spread Index (SI)TC and Purge Time (PT)TC and how they can be employed to evaluate the ventilation effectiveness of laboratory HVAC systems; and
• Understand how Computational Fluid Dynamics (CFD) can be employed in evaluating the ventilation effectiveness of laboratory HVAC systems with DCV.

Biography:

Dr. Kishor Khankari, Ph.D., is a noted expert in Computational Fluid Dynamics (CFD) with several years of experience in providing engineering insights and optimized HVAC design solutions using analytical techniques. He has developed patented technology for exhaust fan assembly. Dr. Khankari is ASHRAE Fellow member and ASHRAE Distinguished Lecturer.

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