(734) 327 4079 info@ansight.com
AnSight’s Solutions for COVID-19

Displacement Ventilation For Hospital Patient Room

May 30, 2020 | Blogs | 0 comments

In displacement ventilation systems, as opposed to the traditional overhead supply mixing ventilation systems, cold air which is supplied at low velocity near the floor captures sensible heat from the space, and rises due to buoyancy, and thus, creates a stratified temperature distribution – cold air near the floor and hot air near the ceiling. This potentially can help in displacing airborne contaminants from the floor to the ceiling, and thus, can create a better indoor environment in the occupied zone. ASHRAE/ASHE Standard 170 – Ventilation of Health Care Facilities has a provision for displacement ventilation for patient rooms.

Recently we performed a comparative study between the traditional overhead supply and displacement ventilation system for a typical patient room using Computational Fluid Dynamics (CFD). Under identical cooling loads the overhead supply system shows recirculating inductive airflow patterns which results in relatively uniform air temperature distribution in the room. Whereas the displacement system shows stratified layers of temperature with predominantly horizontal and vertical airflow patterns. Additionally, thermal comfort analysis indicates displacement system can provide relatively better thermal comfort for occupants at relatively low supply airflow rate. In the case of overhead supply the airborne particles released from the patient’s face can get entrained back into the supply air stream and eventually spread into the entire room. Whereas in the case of displacement system the buoyancy forces keep these particles afloat near the ceiling creating relatively cleaner environment in the occupied zone.

The sensitivity analysis for supply airflow rate or Air Changes per Hour (ACH) indicates that in the case of displacement ventilation 6 ACH and 2 ACH can create respectively too cold and too hot thermal sensation for the occupants whereas the 4 ACH can create thermal neutral environment with optimum conditions for thermal comfort. It should be noted the dynamics of displacement ventilation can change with varying cooling loads and may require modifications in the supply airflow rate and/or supply air temperature to maintain the similar level of thermal comfort. Future study will involve sensitivity study of the displacement ventilation system for various cooling loads in a patient room.
Numerical computations for this study were performed using ANSYS/Fluent CFD software.

About the author

Dr. Kishor Khankari

ASHRAE Fellow, ASHRAE Distinguished Lecturer

Dr Kishor Khankari is the founder of AnSight LLC. As a specialist in Computational Fluid Dynamics (CFD), his passion for solving engineering problems and providing sound scientific solutions has led to innovations and optimized designs in the industry.

A noted expert in his field, he has a Ph.D. from the University of Minnesota and has published in several technical journals and trade magazines. As a well sought-after speaker Dr. Khankari makes regular presentations in various technical conferences and professional meetings worldwide.

Recent Posts

Ventilation Guidance for Residential Kitchen with Gas Stove

Recently the residential gas stoves were in the News due to the generation of pollutants during their operation. Cooking activities as well as the combustion of natural gas through gas stove burners produce several indoor pollutants. Exhausting these pollutants from...

CFD Analysis of Residential Kitchen Ventilation with Gas Stove

Proper ventilation of the kitchen is essential to reduce the occupant exposure to various pollutants generated during the cooking and the combustion of natural gas through the gas stove burners. Several parameters related to the design and operation can affect the...

CFD Analysis of Demand Control Ventilation for Laboratories

What is Demand Control Ventilation (DCV)? Often high air change rates per hour (ACH) are specified for laboratories to meet the goal of ventilation. The ACH numbers specified are mostly consensuses based on simplistic approaches of perfect mixing of contaminants with...

CFD Analysis Evaluates Efficacy of Reactive Air Cleaning Technology

What is reactive air cleaning? Reactive air cleaning involves the release of reactive agents in the room to actively mitigate airborne pathogens and other pollutants. Unlike traditional dilution ventilation in which the concentration of the airborne pathogens in the...

Share This