Marine Hospital Contamination Control And Ameliorating Measures Of IAQ

The development and prevalence of no pollution furniture will transform main indoor microcontamination caused by building materials VOC into that caused by biocontamination. Indoor biocontamination and HVAC system secondary contamination problems are causing wide public concerns. Biocontamination control is the next step to achieving better IAQ. The most efficient and safe way to control biocontamination is by limiting relative humidity in HVAC system and conditioned environment within the range that are most unsuitable for microorganism to survive. That's true for key departments in marine hospital to control biocontamination.HVAC systems are required to maximize their IAQ improving function and minimize their negative effect. To develop new style IAQ-guarantee-target HVAC systems, designers must refer to HVAC system as a contamination source and recognize residue humidity as a contaminant. In this paper, by referring to bio-clean project experiences, a design mode which is to replace primary return air by secondary return air or self recirculation is recommended. This replacement doesn't affect zone ventilation effieciency while does mitigate the risk of secondary contamination. With this design mode, a system-based humidity control priority manner is come into being, which is by lowering outdoor air humidity ratio to eliminate all indoor latent load and using self recirculation units to bear indoor sensible load. With this concept in mind, we designed a full-sized HVAC system model and were engaged on theretic and experimental study, to find that system-based humidity control priority manner is most applicable for key departments in marine hospital.In this paper, a steady state model for coil, which is the key role in humidity control, is developed in the case of film condensation existence on fin surface. It is applicable for predicting condensate carryover phenomena in coil with nonuniform distributed face velocity, also for investigating nonlinear humidity control characteristic of coil and HVAC system. The mode by handling outdoor air to enthalpy point can adapt well to indoor latent load fluctuation, while the mode by handling outdoor air to perfectly eliminate latent load has poor adpation.With whole-course residue humidity contaminant control concept, dynamic step models for coil and conditioned zone are developed to describe mass and energy conservation and transformation processes. Moisture adsorption and desorption feature of wall and floor materials is taken into account in zone model. Model equations are solved using variable separation method, linearized by Taylor approximation and time delay introduction and converted into a transfer function matrix of exit parameters after Laplace transformation. Whole system models, which are consisted of HVAC system and conditioned zone dynamic models are established in Matlab/Simulink platform to investigate optimized regulation types, input signatures and control logics. Decoupling between cooling and dehumidification processes can be achieved and more simplified and stable control system, which are the requirement of key department in marine hospitals, can be acquired by system-based humidity control priority manner.Verification design method for evaluating HVAC system contamination control measures is developed. These measures should be regulable and redundant in some degree according to the reliability requirement. On the premise of performance requirement being met, reliability of parallel system should be readjusted and reallocated when there is a lack of resource.