Heating and ventilation air conditioning systems in hospitals (cleanroom HVAC systems) are used to control the transmission/spreading of airborne diseases such as COVID-19. Air exiting from these systems may contribute to the spreading of coronavirus droplets outside of hospitals. Some research studies indicate that the shortest time of survival of SARS-CoV-2 in aerosol form (as droplets in the air) is four hours and the virus becomes inactive above 60 °C air temperature. Therefore, SARS-CoV-2 droplets cannot exit from the exhaust duct if the temperature is above 60 °C. At the condenser, heat is dissipated in the form of hot air which could be utilized to warm the exhaust air. The objective of this paper is to establish a novel technique for eliminating SARS-CoV-2 from cleanroom HVAC systems using the recovered heat of exhaust air. This can eliminate SARS-CoV-2 and reduce the greenhouse effect.

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In the present study, the optimal location of baffle in the header of air to air plate heat exchangers as well as the geometry of header and the effects of triangular fins arrays on the effectiveness were numerically investigated in different flow rates and Reynolds numbers on different models. The main purpose of inlet baffle and geometry changes is to improve the pattern of flow distribution and assist flow uniformity. The investigations show that the optimal location of inlet baffle in high Reynolds numbers has insignificant effect on effectiveness, while in Reynolds numbers 250-3000, the effectiveness is affected significantly by baffle location. On the other hand, the reduction in flow gradients by changes in geometry can improve flow distribution. Moreover, investigations show that the increase in fin density (fins/mm) up to a special value can enhance the effectiveness. In the present study, the Colburn-j-factor behavior versus different Reynolds number, velocity distributions, pressure drop and velocity vectors are examined.

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