Stanford Engineering
Wind Engineering Lab

Natural Ventilation in Emergency Healthcare Facilities

Streamlines of flow inside a healthcare shelter

Jack Hochschild

Motivation and Objective

The COVID-19 pandemic prompted our group to investigate natural ventilation in the rudimentary health-care facilities found in refugee camps. The World Health Organization (WHO) states that these facilities should have 140 l/s per person of airflow to sufficiently dilute airborne pathogens. By simulating a patient treatment shelter’s airflow and thermal environment,  we seek to find what effect this large amount of airflow has on the indoor thermal environment. Further, we seek to find out if there are configurations (which windows are opened, for example) that mitigate viral spread without making indoor temperatures uncomfortable for occupants.

Left: A COVID patient screening tent at a refugee camp. Right: viral concentration on a horizontal plane inside the tent, assuming 5 COVID-positive patients.

Results

Viral concentration heatmaps of the shelter with infectious patients placed (a) next to windward openings and (b) next to leeward openings

We have run RANS CFD simulations to model flow through a cross-ventilated treatment shelter. From the results, we can infer three practical recommendations for refugee camp operators in hot climates:

  1. Set-up shelter with windows aligned with the dominant wind direction, since ventilation rates significantly decrease with off-normal wind angles
  2. Maximize ventilation at any time of day: at night, thermal comfort is increased by bringing cooler air inside. During the day, maximizing ventilation has a negligible (< 1.0°C) effect on thermal comfort, but decreases airborne viral concentration.
  3. Place infectious patients near leeward windows if possible: this way, exhaled infectious aerosols are drawn out of windows rather than being advected across the shelter (see concentration heatmaps on the right). 

Acknowledgements and Resources

This research is funded by a Stanford ChEM-H (Chemistry, Engineering and Medicine for Human Health) RISE award for COVID-19 research.