Fluid flow in a spiral device used for irradiation of biological fluids

The manufacture of plasma-derived therapeutics includes dedicated viral inactivation steps to minimize the risk of infection. Traditional viral inactivation methods are effective for the removal and inactivation of enveloped viruses, but less effective against small nonenveloped viruses. UV-C irradiation has been demonstrated to be an effective means of inactivating such viruses. The UVivatec lab system consists of a spiral tube around an UV-C irradiation source. Flow of a solution through the chamber generates and ensures controlled mixing and uniform exposure to irradiation. A detailed assessment of the effect of flow rate, alternate cross sectional design and scale up of the irradiation chamber on Dean vortices was performed using the smoothed particle hydrodynamics method. The aim was to provide a basis for setting flow rate limits and using a laboratory scale apparatus to model viral inactivation in larger manufacturing scale equipment. The effect of flow rate related changes on the fluence rate was also investigated through chemical actinometry studies. The data were consistent with the simulations indicating that Dean vortices were present at low flow rates, but dissipated at higher flow rates through the spiral chamber. Importantly, this work also allowed a correlation between the small system and large scale system to be established. This will greatly facilitate process development and viral validation studies.