Experimental and numerical study on the thermal plumes of a standing and lying human in an operating room

Abstract

This paper presents a study regarding the thermal plumes generated by two thermal manikins in different positions, both numerically and experimentally. The numerical model represents an operating room with two surgeons, a patient, and a ventilation system with a unidirectional airflow diffuser, also called a laminar airflow diffuser, and outlets placed in the corners. The experimental study was made in a climatic chamber, similar with the numerical model, using particle image velocimetry and infrared thermography measurements. The thermal plumes of the two manikins were obtained by numerical and experimental studies. Another purpose of the study was to see how these thermal plumes will interfere with a low velocity ventilation system, like a unidirectional airflow system. The studies showed thermal plume velocities up to 0.35-0.4 m/s for a human subject that is standing and up to 0.2 m/s for a human subject that is lying on a bed. Analyzing the interaction of the thermal plumes with a diffuser that has low airflow velocities, like a laminar airflow system, one can observe that velocities !0.2 m/s will have difficulties in overcoming the thermal plumes generated by human subjects that have a sedentary to moderate activity.

Virus-laden droplet nuclei in vortical structures associated with recirculation zones in indoor environments: A possible airborne transmission of SARS-CoV-2

“…Jet dispersion has been widely documented in fluid mechanics ( Li et al, 2020 ), and it presents the formation of recirculation flow around the jet (see Fig. 1 a), as reported by ventilation studies conducted by Tacutu et al (2019 , 2021 ). On the other hand, the air patterns in an indoor environment present the formation of recirculation zones in the corners of the room by an internal airflow interaction, as shown in Fig.…”

“…The thermal plume could cause the formation of recirculation zones in vertical ventilation systems operated at very low injection air velocities because the airflow momentum of supply air cannot overcome the thermal plume generated by the heat source. For instance, Yang et al (2015) , Lin et al (2020) , Tacutu et al (2021) , and Liu et al (2022c) studied the vertical airflow dispersion in a room under the unidirectional airflow (UAF) or known as laminar airflow (LAF) system. This ventilation system injects air from the room's ceiling and discharges it by outlet diffusers on the lateral walls or corners of the room.…”

“…Then high bioaerosol concentration (96 cfu m −3 ) was found in some regions, while droplets were entrained towards the airflow in other zones (10 cfu m −3 ). Tacutu et al (2019 , 2021 ) studied the air circulation near an operating table under the UAF, known as the LAF scheme. Numerical simulation exhibited the formation of a peripheral recirculation by jet dispersion, a recirculation zone behind the operating table, and a recirculation zone on the patient by the thermal plume ( Fig.…”

“…In both cases, the UAV scheme allows the formation of a large recirculation zone (see Fig. 3 ) at low air injection velocities less than or equal to 0.2 m/s ( Yang et al, 2015 ; Lin et al, 2020 ; Tacutu et al, 2021 ; Liu et al, 2022c ). These vortical structures are possible because the UAV operates at low air-injected velocities (0.2-0.3 m/s), according to Sadrizadeh et al (2021) , but a lack of information cannot verify this phenomenon.…”

Effect of thermal manikin shape on thermal comfort parameters prediction uncertainties: a numerical study

“…Empirical correlations for definition of the thermal comfort parameters were suggested during last decades (see, e.g., [3][4][5]), and now the verified relations suitable for engineering estimates could be found in the international standards (see, e.g., [6]). Today the thermal comfort parameters could be estimated not only as integral quantities, but as local quantities using the 3D computational fluid dynamic (CFD) airflow modelling results [7,8].…”