One of the important components of a nuclear fuel cycle facility is a hot cell. Hot cells are engineered robust structures and barriers, which are used to handle radioactive materials and to keep workers, public, and the environment safe from radioactive materials. To provide a confinement function for these hot cells, it is necessary to maintain the soundness of the physical structure, but also to maintain the negative pressure inside the hot cell using the operation of the heating, ventilation, and air conditioning (HVAC) systems. The negative pressure inside the hot cells allows air to enter from outside hot cells and limits the leakage of any contaminant or radioactive material within the hot cell to the outside. Thus, the HVAC system is one of the major components for maintaining this negative pressure in the hot cell. However, as the facility ages, all the components of the hot cell HVAC system are also subject to age-related deterioration, which can cause an unexpected failure of some parts. The abnormal operating condition from the failure results in the increase of facility downtime and the decrease in operating efficiency. Although some major parts are considered and constructed in redundancy and diversity aspects, an unexpected failure and abnormal operating condition could result in reduction of public acceptance and reliability to the facility. With the advent of the 4th Industrial Revolution, prognostics and health management (PHM) technology is advancing at a rapid pace. Korea Hydro & Nuclear Power, Siemens, and other companies have already developed technologies to constantly monitor the integrity of power plants and are applying the technology in the form of digital twins for efficiency and safety of their facility operation. The main point of PHM, based on this study, is to monitor changes and variations of soundness and safety of the operation and equipment to analyze current conditions and to ultimately predict the precursors of unexpected failures in advance. Through PHM, it would be possible to establish a maintenance plan before the failure occurs and to perform predictive maintenance rather than corrective maintenance after failures of any component. Therefore, it is of importance to select appropriate diagnostic techniques to monitor and to diagnose the condition of major components using the constant examination and investigation of the PHM technology. In this study, diagnostic techniques are investigated for monitoring of HVAC and discussed for application of PHM into nuclear fuel cycle facilities with hot cells.

This study investigated the odor-associated bacterial community in automobile HVAC systems. Through a metagenome analysis, it was found that; Massilia (42.426%), Sphingomonas (28.200%), (10.780%), and Methylobacterium (5.756%) were abundant in the HVAC systems. Massilia can cause the biodegradation of polycyclic aromatic hydrocarbons (PAHs) producing odor in automobiles. Sphingomonas produces volatile halogenated compounds or degrades organic pollutants. Rhodococcus is reported to produce sulfur compounds which give off an odor similar to rotting eggs and cabbages. Methylobacterium is one of the most representative bacteria that causes odor in automobile HVAC systems. The evaporator is considered as the appropriate habitat for microorganisms in automobiles because of its high humidity and organic adsorption. Massilia, Sphingomonas, Rhodococcus, Methylobacterium, Bacillus, Staphylococcus, Arthrobacter, Micrococcus, and Pseudomonas, listed in order from most to least present, were isolated as abundant bacteria in the evaporator of the HVAC systems.

In this research, the heat and flow analysis in a condenser of vehicle HVAC system was investigated numerically regarding the different shapes of the condenser tube. The velocity, pressure, and temperature distribution of the test fluid(R-134A) inside the tube were numerically calculated for the optimum design of the condenser tube for two different length with four different inlet velocities. In addition, the local pressure and temperature distributions for total tube length were calculated and the variation of pressure drop of the R-134A with flow rate were also calculated numerically. The tube at case 1 with less curved elbows was determined for the better design than case 2 in the aspect of energy-effective shape of the condenser tube.

Under controlled conditions in an environmental chamber, 24 experiments were performed to compare the ability of a Variable-Air-Volume/Bypass Filtration System(VAV/BPFS) to remove indoor pollutants and to conserve energy with the ability of conventional Variable Air Volume(VAV) system. The specific conclusions of this paper were; first, the VAV/BPFS was more efficient than the VAV system in removing particulate matter, TVOC, and target VOCs. The total effective removal rate of PM for the VAV/BPFS was two times as high as that of the VAV system. The total effective removal rate of TVOC for the VAV/BPFS was 20 percent higher than that of the VAV system. Also each target VOC concentration was reduced by using the VAV/BPFS. Second, clean air delivery rate was increased by using VAV/BPFS due to additional filtration rate. Otherwise, the VAV/BPFS decreased outdoor supply air rate above 25 percent relative to the rate of VAV system. Third, total energy consumption by the VAV/BPFS was lower than that of the VAV system during the period with indoor thermal load, occupied time. The energy saving of the VAV/BPFS ranged from 11 to 16 percent. The VAV/BPFS improves indoor air quality more efficiently than the VAV system, and it reduced energy consumption. Retrofitting the VAV system with the VAV/BPFS was easy. The use of VAV/BPFS is, therefore, recommended for buildings with VAV system as well as for buildings at designing stage.