Abstract Air Conditioning Systems Research Articles

Performance Improvement of Membrane Energy Exchanger Using Ultrasound for Heating, Ventilation, and Air Conditioning Application

Abstract Air conditioning (AC) systems consume the maximum proportion of the total electricity used in the building sector. The demand for AC systems is expected to increase exponentially in the coming years due to various reasons such as climate change, and an increase in affordability and living floor space. A membrane-based liquid desiccant AC system along with energy recovery ventilating equipment is considered as a prospective alternative to the conventional air conditioning system (CACS). It has the potential to meet the increasing current and future AC demand in a sustainable manner. Its efficiency and energy-saving potential with respect to CACS depend on the performance of the membrane-based dehumidifier, regenerator, and energy recovery ventilating equipment, commonly referred to as membrane energy exchangers (MEEs). MEE is an indirect exchanger type in which a membrane separates the working streams. This intermediate membrane creates an additional resistance for the heat and mass transfer processes in the MEE. To reduce the resistance, this study experimentally and numerically investigate the influence of ultrasound on the performance of the MEE for dehumidification, humidification (applicable for membrane-based evaporative cooling and desiccant regeneration devices), and energy recovery processes. It is found that the vibration due to ultrasound has the potential to improve the mass transfer performance of MEE by the resistance at the air-membrane interface.

Analysis of the Behavior of an Air Conditioning System Based on the Solar Energy Natural Regulation in Amazonian Climatic Conditions

Abstract Air conditioning systems (ACSs) represent one of the main demands for electricity in residential, commercial, and industrial buildings. The use of a photovoltaic air conditioning unit (PVACU) represents an attractive application to this demand for reasons such as environmental concerns and the match between diurnal cooling load and solar resource. A PVACU consists of a photovoltaic generator (PVG) that supply an ACS through direct current to direct current and frequency converters, without energy storage. This system considers the natural adjustment of the ACS cooling capacity according to the PVG power. Modeling the ACS, the PVG, and the thermal load (TL) makes possible to evaluate PVACU performance. For this, a small library’s TL and an ACS supplied by a PVG were used as case study. The PVG installed capacity assumes values of 700, 1000, and 1400 Wp. The simulation results show that the PVACU with a 1400 Wp PVG would be sufficient to regulate internal temperature within international comfort standards in the range of 20 °C to 24 °C. According to the data obtained in the simulations, it was possible to conclude that the PVACU has a large potential to be used in air conditioning of other environments in regions with Amazonian climatic conditions.

Dominance of Gas-Eating, Biofilm-Forming Methylobacterium Species in the Evaporator Cores of Automobile Air-Conditioning Systems.

Microbial communities in the evaporator core (EC) of automobile air-conditioning systems have a large impact on indoor air quality, such as malodor and allergenicity. DNA-based microbial population analysis of the ECs collected from South Korea, China, the United States, India, and the United Arab Emirates revealed the extraordinary dominance of Methylobacterium species in EC biofilms. Mixed-volatile organic compound (VOC) utilization and biofilm-forming capabilities were evaluated to explain the dominance of Methylobacterium species in the ECs. The superior growth of all Methylobacterium species could be possible under mixed-VOC conditions. Interestingly, two lifestyle groups of Methylobacterium species could be categorized as the aggregator group, which sticks together but forms a small amount of biofilm, and the biofilm-forming group, which forms a large amount of biofilm, and their genomes along with phenotypic assays were analyzed. Pili are some of the major contributors to the aggregator lifestyle, and succinoglycan exopolysaccharide production may be responsible for the biofilm formation. However, the coexistence of these two lifestyle Methylobacterium groups enhanced their biofilm formation compared to that with each single culture.IMPORTANCE Air-conditioning systems (ACS) are indispensable for human daily life; however, microbial community analysis in automobile ACS has yet to be comprehensively investigated. A bacterial community analysis of 24 heat exchanger fins from five countries (South Korea, China, the United States, India, and the United Arab Emirates [UAE]) revealed that Methylobacterium species are some of the dominant bacteria in automobile ACS. Furthermore, we suggested that the predominance of Methylobacterium species in automobile ACS is due to the utilization of mixed volatile organic compounds and their great ability for aggregation and biofilm formation.

Comparing Cooling Energy between Existing Air-Conditioning System and Proposed Design System

Air-conditioning (AC) system is typically used to remove the sensible and latent heat loads in buildings. It provides cool and dehumidified air to meet the occupants comfort and good indoor air quality (IAQ). Improper design and analysis of AC process resulted in high cooling energy and unsatisfied indoor humidity level in tropical climate. The objective of this study is to identify the cooling energy in hotel restaurant by comparing the design with proper fresh air ventilation design. The hotel restaurant was designed with primary air unit (PAU) and air handling unit (AHU) as to remove sensible and latent loads. The performance of the AC system has been monitored and analysed using psychrometric chart. For the AC air side system, 296.2 kW of cooling energy was used in standard operation. An alternative design was proposed for the said hotel restaurant employing only one AHU, with a cooling capacity of 165.9 kW which was 43 % lower than the existing system. The difference in temperature, humidity ratio and air flow rate influenced the cooling energy for AC system.