Ultrasonic Humidifier Research Articles

Two Sporadic Cases of Legionellosis Associated with the Use of Domestic Ultrasonic Humidifiers.

Two sporadic cases of legionellosis occurring in consecutive years were confirmed by positive antigenuria to Legionella pneumophila serogroup 1 in individuals with limited mobility who were confined to their homes. Both cases had a history of using ultrasonic humidifiers and of low exposure to other possible sources of infection. This study was conducted through an expanded epidemiological survey and home inspection. Samples were collected from domestic hot water and humidifiers. Environmental isolates were characterised by immunoagglutination and immunofluorescence. The Dresden panel is employed for the determination of groups and subgroups of serogroup 1. The amoebae were isolated by water filtration and subsequent cultivation of the filters. Identification of the isolates was conducted through the sequencing of PCR products. In both cases, epidemiological studies identified the ultrasonic humidifiers as the probable source of infection. The presence of Legionella pneumophila was confirmed in the sanitary water installation and in the humidifiers, where high values of Legionella pneumophila serogroup 1 counts were also obtained. The isolates were characterised as Olda Oxford and Olda OLDA. Furthermore, in addition to the Legionella isolates, the presence of Vermamoeba vermiformis was also identified in samples obtained from domestic hot water and humidifiers in one of the residential addresses under investigation. It has been demonstrated that humidifiers can act as an amplification mechanism for pathogenic microorganisms when they are not cleaned and maintained correctly. This can pose a health danger, especially to people with previous respiratory pathologies, the immunosuppressed, and the elderly. Therefore, it is of the utmost importance that professionals who recommend the therapeutic use of this equipment should issue warnings regarding the importance of its correct use, cleaning, and disinfection. Finally, humidifiers should be considered in epidemiological surveys and in the study of sporadic cases.

Experiment and modeling of an improvised atmospheric water harvester for arid and semi-arid conditions

Freshwater scarcity is a severe challenge in arid and semi-arid climatic conditions wherein the water harvesting from the atmosphere using active cooling condensation technique (ACC) is the only option. In this regard, we performed extensive experiments on a classical atmospheric water harvester (AWH) that relies on moisture condensation via a typical 1TR refrigeration cycle. We developed a MATLAB-SIMULINK based AWH model to note that the classical system has reasonable water harvesting rates in humid climates, but is inadequate for arid and semi-arid climatic conditions. We add an ultrasonic humidifier (160 W power input) before the evaporator section of the classical AWH system to address this issue. The modified system only needs a small amount of water (≈250 ml) for start-up, and further operates without perpetual water supply. We measure the water overflow from the humidifier tank (subtract the water added via the humidifier from the total water harvest) to show a net water harvesting in extremely hot and dry conditions (49 °C DBT and 12 % RH) resembling the weather conditions of Jaisalmer, India. A significant improvement of up to 70 % in water harvesting was also observed under warm and dry climates (35 °C DBT and 21 % RH) mimicking Jaipur, India. We believe that our system shows path for developing active AWH systems with substantial water harvesting in arid climates where active moisture condensation using the conventional strategy is otherwise not possible.

Ultrasonic humidifier aerosols: Observed high heavy metal enrichment and a new emission control method

Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols. However, there have been various health concerns associated with humidifier use, largely due to aerosols generated during operation. Here, we investigated the size distribution, chemical composition, and charged fraction of aerosol particles emitted from commercial ultrasonic humidifiers. Heavy metals in water used for humidifiers were found to be highly enriched in the ultrasonic humidifier aerosols (UHA), with the enrichment factors ranging from 102 to 107. This enrichment may pose health concerns for the building occupants, as UHA concentrations of up to 106 particles/cm3 or 3 mg/m3 were observed. Furthermore, approximately 90% of UHA were observed to be electrically charged, for the first time according to our knowledge. Based on this discovery, we proposed and tested a new method to remove UHA by using a simple electrical field. The designed electrical field in this work can efficiently remove 81.4% of UHA. Therefore, applying this electrical field could be an effective method to significantly reduce the health risks by UHA.

#3351 TRIAL OF ISOLATED HAEMODIALYSIS WITH PATIENT-ENTRY TENT AND HYPOCHLORITE MIST

Abstract Background and Aims The global spread of COVID-19 has posed a serious threat to patients receiving renal replacement therapy and to the staff who treat them. Every time they treat a patient or operate a machine, they have to wear personal protective equipment (PPE). In order to reduce the burden on our staff, we have introduced two pieces of equipment. One is a hypochlorous acid mist for room and surface disinfection using CLFine®. The other is an AIR ZIPPER® patient isolation tent in the existing isolation room. Both products were manufactured by Nipro Corporation of Osaka, Japan. However, there was no evidence to support the use of hypochlorous acid in an ultrasonic humidifier. Therefore, Nipro Corporation conducted a “28-day repeated inhalation toxicity study” on rats with a third party organisation and confirmed the results as toxicologically safe. According to the Occupational Safety and Health Act, also in the school environmental health, the concentration of chlorine in the air is 0.5 ppm or less (8 hours/day, 5 days/week or less). CL Fine® has shown an antiviral effect within these regulations. The size of the AIR ZIPPER® is about a fifth of the standard 10m3 size, down to about 2m3. Powerful, high-efficiency particulate air filter pumps have been fitted to replace the air in the tent in less than 5 minutes at low flow rates (0.4 m3/min airflow), enabling it to operate below the negative pressure standard of 2.5 Pascal. In addition, the AIR ZIPPER® is equipped with air intake valves that open and close in a single direction towards the inside of the tent. Prior to the introduction of the AIR ZIPPER®, staff had to wear PPE with an N95 mask when operating the machine, puncturing and returning blood to the patient. Method Patients with a fever or who have been in contact with COVID-19 patients and infected patients were asked to enter the AIRZIPPER®. The haemodialysis machine is placed outside. The zipper of the AIRZIPPER® could not be closed until the puncture procedure had been completed. To reduce the spread of viruses outside the tent, the high air volume (air flow rate 0.9 m3/min) allows a one-way air flow from the outside to the inside. Following the puncture, the tent zipper was sealed and the air pressure was adjusted to reach the recommended negative pressure of 2.5 Pa and above within 1 minute. Furthermore, the hypochlorous acid mist with CLFine® has the ability to disinfect viruses from the outside of the AIR ZIPPER®. Therefore, after the 30 minutes with the zip closed in the isolation room, the outside of the AIR ZIPPER® was operated as a safe zone. Results On 13 January 2022, two pieces of equipment arrived at the Toshin Clinic and all patients carrying COVID-19 who subsequently developed the disease were isolated and haemodialysed. Quarantine dialysis was performed in 156 patients, including those who had close contact with a COVID-19 patient or who had fever. A total of 96 isolation haemodialysis sessions using AIR ZIPPER® and CL Fine® were performed on 22 COVID-19 patients (male/female: 19/3, age: 69.8 ± 14.2 years, HD duration: 5.38 ± 3.8 years) with SARS-CoV-2 infection in our clinic. Fortunately, there was no transmission to staff or other patients, and no patients died. Conclusion These infection control measures helped to reduce staff workload and prevent infections. In conclusion, the present method should be equipped by all haemodialysis providers to deal with Covid 19 infections as well as with new infections in the future.

Study of a new humidifier configuration designed for climatic chambers

Climate chambers are crucial for testing and developing different products under specific atmospheric conditions. To ensure the accuracy and reliability of the results, it is essential to maintain precise control over the chamber's relative humidity and temperature levels. However, designing a humidifier that meets the stringent requirements of a climate chamber remains a challenge. This paper presents a modular piezoelectric ultrasonic humidifier designed to fulfill the high reliability and homogeneity standards demanded in industrial and pharmaceutical applications. The experimental design and testing of the prototype are discussed, and the simulations performed to evaluate the humidifier's homogeneity and airflow orientation are presented. The prototype was tested by coupling it to an 85 m3 climate chamber dedicated to storage and validated under a temperature condition of 25 °C ± 2 °C and relative humidity of 60% ± 5%. Compared to commercial humidifiers, the specific design of the prototype allowed for better insulation while ensuring the required homogeneity in the climate chamber. During the tests, the relative humidity was 60% ± 3% with temperatures of 25 °C ± 0.5 °C. The results also show that the prototype enabled quick and efficient rebalancing of the relative humidity level while keeping the chamber within the permitted relative humidity limits. Overall, this work contributes to the advancement of climate chamber technology, which is critical in product development and research applications.

Indoor dryness and humidification-induced arsenic inhalation exposure above 4200 m in Ngari, China.

Ngari Prefecture, Tibet, China, features its ultrahigh altitude above 4200 m, very little annual precipitation and extremely low relative humidity. Residents who have migrated to Tibet from the plains use indoor humidification to reduce the respiratory discomfort caused by prolonged exposure to dry indoor air. In this study, field investigations and analysis of residential indoor environments and humidification methods in Ngari Prefecture revealed that ninety-eight percent of humidifier consumers in the prefecture used low-cost ultrasonic humidifiers filled with indoor tap water. The results revealed that the arsenic (As) concentration of the tap water was 41.6μg/L, over four times China's standards for drinking water quality (10μg/L). The source As concentration in the air humidified by the tap water-filled ultrasonic humidifier is (619.8 ± 59.1) (ng/m3 ·air), while no As was detected in the air humidified by the evaporative humidifier. For ultrasonic humidifier with tap water-filled, the inhalation dose of a healthy adult was 45.4ng/d. The minute ventilation volume of migrated residents who had been in Ngari for less than two years (12.5 ± 4.3L/min) was greater than those of the long-term residents (10.0 ± 4.5L/min), which may exacerbate the short-term inhalation exposure risk for migrated residents. To reduce the health risks associated with As exposure, evaporative humidifiers are recommended for households using domestic water. If ultrasonic humidifiers are used, the tap water must be purified with terminal filters.

Environmental risks from consumer products: Acceptable drinking water quality can produce unacceptable indoor air quality with ultrasonic humidifier use

The commonly used consumer product of an ultrasonic humidifier (e.g., cool mist humidifier) emits fine particles containing metals from tap water used to fill the humidifier. The objectives are: 1) predict emitted indoor air inhalable metal concentrations produced by an ultrasonic humidifier filled with tap-water containing As, Cd, Cr, Cu, Mn, and Pb in 33 m3 or 72 m3 rooms with varying air exchange rates; 2) calculate daily ingestion and 8-h inhalation average daily dose (ADD) and hazard quotient (HQ) for adults and children (aged 0.25–6 yr); and 3) quantify deposition in respiratory tract via multi-path particle dosimetry (MPPD) model. Mass concentrations of indoor air metals increase proportionally with aqueous metal concentrations in fill water, and are inversely related to ventilation. Inhalation-ADDs are 2 magnitudes lower than ingestion-ADDs, using identical water quality for ingestion and fill-water. However, in the 33 m3, low 0.2/h ventilated room, inhalation-HQs are >1 for children and adults, except for Pb. HQ inhalation risks exceed ingestion risks at drinking water regulated levels for As, Cd, Cr, and Mn. MPPD shows greater dose deposits in lungs of children than adults, and 3 times greater deposited doses in a 33 m3 vs 72 m3 room. Rethinking health effects of drinking water and consumer products to broaden consideration of multiple exposure routes is needed.

Combined cooling of photovoltaic module integrated with thermoelectric generators, by using earthenware water tank and ultrasonic humidifier: An experimental study

The purpose of the present research is to reduce the temperature of photovoltaic (PV) module using a combined cooling method in order to improve electrical output, having better performance and simultaneous integration of thermoelectric generators (TEG) with it and to generate surplus electricity from the existing temperature difference in the proposed system. An L-shaped earthenware water tank as the passive cooling method and an ultrasonic humidifier inside the tank as the active cooling method formed the combined cooling sections of the proposed system. The ultrasonic humidifier converts the cooled water inside the earthenware tank to cold mist in the enclosed space backside of the PV module by a piezoelectric actuator based on the cavitation phenomenon (reduction of PV module temperature occurs by heat transfer and conductivity). Temperature difference between the surface of the PV module and cold mist on backside of the PV module converts to surplus electricity by TEG. In this study, three cold mist creation capacities of 250, 400 and 550 mL/h were investigated and the greatest improvement in the utilization of solar energy compared to the control PV module was for the cold mist creation capacity of 550 mL/h. Temperature reduction of PV section of about 5.2 °C, PV maximum power improvement of 5.1% and total efficiency improvement of 4.96% were obtained in the proposed system with cold mist creation capacity of 550 mL/h compared to control PV module. It was concluded that unlike cooled PV module, the share of TEG array is very negligible in the total efficiency improvement.

EVALUATION OF STARCH AND CELLULOSE BASED CONSOLIDATION MATERIALS ON THE MECHANICAL PROPERTIES OF PAPYRUS

In this study, polysaccharides, namely, potato starch, ethyl hydroxyethyl cellulose and cellulose nanocrystals (CNC), were used as consolidation materials for papyrus. The starch solution was applied on papyrus strips by two different methods: by brush and by an ultrasonic humidifier, the latter being a new approach for the application of consolidation materials. The consolidated papyrus was subjected to a thermal ageing study and several measurements were conducted to evaluate the efficiency of the selected consolidation materials and of the two different application methods of starch. The mechanical properties of the consolidated papyrus strips were evaluated by measuring the tensile strength and elongation. FT-IR spectroscopy and scanning electron microscopy of the papyrus strips were performed before and after thermal ageing. The study showed that CNC and ethyl hydroxyethyl cellulose improved the mechanical properties of the tested strips. Applying potato starch using the ultrasonic humidifier improved the mechanical properties of the consolidated strips more significantly than its application by brush.

Monitoring and management ion concentrations in the air of industrial and public premises

This paper reports a substantiated method and a designed device for controlling the concentrations of air ions in premises in accordance with the European standards SBM 2015. The use of an ultrasonic humidifier with a capacity of 25 W for two hours increases the concentration of negative ions around the device from 240 to 560 cm-3, positive ones ‒ from 260 to 410 cm-3. The intensity of the electrostatic field of a polymeric coating decreases from 5.1 to 0.2 kV/m. The disadvantage of the humidifier is a small radius of influence (1.0–1.5 m) and the inability to control the polarity of ions. It has been experimentally established that air cooling systems (split systems) deionize the air of the premises. Degrees of deionization and dominating polarity are unpredictable and different for devices of different manufacturers and brands. To control the ion composition of the air simultaneously with the maintenance of normative relative humidity and stresses of static fields, the structure was proposed and the effectiveness of a bipolar ultrasonic air ionizer with adjusted performance and dominating polarity has been tested. The maximum productivity of the ionizer is 4,000–5,000 cm-3. The radius of exposure is 5 m (reducing the concentration of ions with a distance to 500 cm-3). To pass the ionized air through an air capacitor, the number and predominant polarity of air ions are regulated by the polarity and voltage on the covers of the capacitor. It was established that in order to service a room with an area of 50 m2, an ultrasonic emitter with a capacity of 25 W would suffice. The adjustability of the device performance makes it possible to reduce or increase the service area. The ability to purify air from suspended particles is shown. During the two hours of operation of the ionizer, the dust content decreased from 4.3–4.4 mg/m3 to 1.4–1.6 mg/m3.

Enhancement of the Evaporation and Condensation Processes of a Solar Still with an Ultrasound Cotton Tent and a Thermoelectric Cooling Chamber

In this paper, an experimental investigation study was conducted to show the effect of enhancing the evaporation and condensation processes inside a modified solar still by placing ultrasonic humidifiers inside a cotton mesh tent in the basin water and by installing a cooling chamber with thermoelectric elements on top of the solar still. Various parameters were recorded every hour, such as temperatures at different points within the solar still, the weather conditions (e.g., solar irradiance intensity, ambient air temperature, and wind speed), the yield of distilled water, and thermal efficiency on 29 July 2021 at the Ural Federal University (Russia). The production cost of distilled water from modified and traditional solar stills was also estimated. The experimental results showed that the productivity of the modified solar still increased by 124% compared with the traditional solar still, and the highest thermal efficiency was recorded at 2:00 p.m. (approximately 95.8% and 35.6% for modified and traditional solar stills, respectively). Finally, the productivity cost of distillate water (1 L) was approximately 0.040 and 0.042 $/L for the modified and traditional solar stills, respectively. The current work has contributed to increasing solar still productivity by applying simple and new technologies with the lowest possible capital and operational costs.

Environmental Risks from Consumer Products: Acceptable Drinking Water Quality Can Produce Unacceptable Indoor Air Quality with Ultrasonic Humidifier Use

Environmental Risks from Consumer Products: Acceptable Drinking Water Quality Can Produce Unacceptable Indoor Air Quality with Ultrasonic Humidifier Use

Portable ultrasonic humidifier exacerbates indoor bioaerosol risks by raising bacterial concentrations and fueling pathogenic genera.

Portable ultrasonic humidifiers are frequently used in heating rooms to ease air dryness. However, it has also posed serious health concerns such as "humidifier fever" because the bioaerosol concentration and community in the humidified space may alter quickly before the occupants could even notice. We compared the microbial proliferation rates in the humidifiers' reservoirs filled with three commonly used water types and investigated the impacts of the ultrasonic humidifiers on the temporal concentration, size distribution, and community variations of indoor bacterial and fungal aerosols during two-week humidification. The concentration of indoor bacterial aerosols increased exponentially, concentrating in the respiratory size ranges (≤1.1µm), and was proportional to the humidification level, which soon exceeded 1000CFU/m3 in one week (at RH=70%), while the fungal concentration always remained low (≤177CFU/m3 ). The indoor bioaerosol community, significantly associated with the humidifier water, was substantially distorted after humidification and dominated by the pathogenic Pseudomonas spp. (40.50%), Brevundimonas spp. (3.02%), Acinetobacter spp. (0.98%) and Legionella spp. (0.69%). Our results show that ultrasonic humidification contaminates indoor air by raising bacterial concentrations and fueling the pathogenic genera. To minimize the exposure risks, occupants should avoid long-term and excessive humidification (RH≥70%) and clean the ultrasonic humidifier weekly.

The Air-Water Interface of Water Microdroplets Formed by Ultrasonication or Condensation Does Not Produce H2O2.

Recent reports on the production of hydrogen peroxide (H2O2) on the surface of condensed water microdroplets without the addition of catalysts or additives have sparked significant interest. The underlying mechanism is thought to be ultrahigh electric fields at the air-water interface; smaller droplets present larger interfacial areas and produce higher (detectable) H2O2 yields. To gain insights into this phenomenon, we performed condensation experiments and quantified H2O2 formation as a function of the vapor source. Specifically, we compared the H2O2 concentration in water microdroplets condensed from the vapor realized via (i) heating water in the range of 50-70 °C and (ii) ultrasonic humidification (as exploited in the original report). Experimental results revealed that the H2O2 level inside water microdroplets condensed via heating water was below our detection limit (≥0.25 μM), regardless of the droplet size or the substrate wettability. In contrast, water droplets condensed via ultrasonic humidification contained significantly higher (∼1 μM) H2O2 concentrations. We conclude that the ultrasonic humidifiers contribute to H2O2 production, not droplet interfacial effects.

The impact of using portable humidifiers on airborne particles dispersion in indoor environment

Portable humidifiers are extensively employed to increase indoor humidity; however, the generated particles could affect people indoors and cause a heavy disease burden. This study aims to compare the potential for an ultrasonic humidifier and an evaporative humidifier to release suspended materials contained in the charging water in a room-sized chamber and estimate the disease burden attributed to PM 2.5 released by humidifiers. Size distributions and concentrations of indoor particles were measured when humidifiers were filled with five types of water with varying total dissolved solids (TDS). Results showed a linear association (R 2 =0.980) between particles produced by the ultrasonic humidifier and the TDS in water. Evaporative humidifiers could produce a small number of particles when tap water was used, but the linear relationship between the released particles and TDS in water was weak (R 2 =0.028). The disability-adjusted life years (DALY) attributed to PM 2.5 generated by the ultrasonic humidifier was 22.4 times that of the evaporative humidifier when using tap water. This study provides valuable data on characteristics of particles released by two different humidifiers and highlights the potential disease burden of exposure to PM 2.5 generated by humidifiers, which may help exclude any adverse effects of using portable humidifiers. • The impact of portable humidifiers on airborne particles is explored. • Ultrasonic humidifiers can release dissolved solids from the charging water. • Evaporative humidifiers have few influences on airborne particles. • Ultrasonic humidifiers can cause heavy burden of disease when using tap water.

Combining Indoor Positioning Using Wi-Fi Round Trip Time with Dust Measurement in the Field of Occupational Health.

Monitoring of personal exposure to hazardous substances has garnered increasing attention over the past few years. However, no straightforward and exact indoor positioning technique has been available until the recent discovery of Wi-Fi round trip time (Wi-Fi RTT). In this study, we investigated the possibility of using a combination of Wi-Fi RTT for indoor positioning and a wearable particle monitor (WPM) to observe dust concentration during walking in a simulated factory. Ultrasonic humidifiers were used to spray sodium chloride solution inside the factory. The measurements were recorded three times on different routes (Experiments A, B, and C). The error percentages, i.e., measurements that were outside the expected measurement area, were 7% (49 s/700 s) in Experiment A, 2.3% (15 s/660 s) in Experiment B, and 7.8% (50 s/645 s) in Experiment C. The dust measurements were also recorded without any obstruction. A heat map was created based on the results from both measured values. Wi-Fi RTT proved useful for computing the indoor position with high accuracy, suggesting the applicability of the proposed methodology for occupational health monitoring.

Risks to children from inhalation of aerosolized aqueous manganese emitted from ultrasonic humidifiers can be greater than for corresponding ingestion

The essential trace element manganese (Mn) can cause neurotoxicity with inhalation acknowledged as a more severe health and cognition threat than ingestion. Methods: Over a range of aqueous Mn concentrations present in tap water, this research characterizes exposures and risks for adults and 0.25, 1, 2.5, and 6 yr old children who ingest the water and inhale respirable particles produced by a room-sized ultrasonic humidifier filled with the same water. Aqueous Mn concentrations evaluated included 50 µg/L USEPA esthetic guideline, 80 µg/L WHO infant guideline, and 120 µg/L Canadian regulatory level. Airborne-particle-bound Mn concentrations were generated for water filling an ultrasonic humidifier under four realistic room conditions (33 m3 small or 72 m3 large) with varying ventilation rates from 0.2/h -1.5/h. Average daily doses (ADD) and reference intake doses were calculated for ingestion and 8-h inhalation of humidified air. Hazard quotients (HQ) compared the intake doses and reference doses. Multi-path particle dosimetry (MPPD) model quantified the particle deposition and deposited dose in children's and adults’ respiratory tracts. Results: At only 11 µg/L Mn, the resulting humidified air Mn exceeds USEPA's reference concentration of 0.05 µg/m3 Mn in small room with low, energy-efficient ventilation. Inhalation ADD are 2 magnitudes lower than ingestion ADD for identical water Mn concentrations and daily exposure frequency. Even so, ingestion HQs are approximately 0.2 but inhalation risk is significant (HQ>1) for children and adults when breathing Mn-humidified air under most small room conditions at 50, 80 or 120 µg/L Mn. MPPD model indicates inhaled Mn deposits in head and pulmonary regions, with greater Mn dose deposits in children than adults. Conclusion: Inhalation of Mn-particles produced from ultrasonic humidifiers can pose greater risks than ingestion at the same water concentration, especially for children. Aqueous Mn concentration and room size influence risks. Limiting manganese exposures and setting regulations requires consideration of both ingestion and inhalation of water.

Ammonia Generation System for Poultry Health Research Using Arduino.

An ammonia gas (NH3) generator was developed to maintain a set concentration of ammonia gas in a controlled environment chamber to study poultry physiological responses to sustained elevated levels of ammonia gas. The goal was to maintain 50 parts per million (ppm) of ammonia gas in a 3.7 m × 4.3 m × 2.4 m (12 ft × 14 ft × 8 ft) controlled environment chamber. The chamber had a 1.5 m3/s (3000 cfm) recirculation system that regulated indoor temperature and humidity levels and a 0.06 m3/s (130 cfm) exhaust fan that exchanged indoor air for fresh outdoor air. The ammonia generator was fabricated by coupling ultrasonic humidifiers with an Arduino-based microcontroller and a metallic oxide MQ-137 ammonia gas sensor. Preliminary evaluation under steady conditions showed the average MQ-137 gas sensor accuracy was within 1.4% of the 65.4 ppm concentration measured using a highly accurate infrared gas analyzer. Further evaluation was performed for a setpoint concentration of 50 ppm where ammonia generator reservoirs were filled with 2% or 10% ammonia liquid. For the system tested, it was found that two generators operating at the same time filled with 3.8 L (1.0 gallon) of 2% ammonia cleaning liquid each (7.6 L or 2.0 gallons total) could maintain a gas level of 49.45 ± 0.79 ppm in the chamber air for a duration of 30 h before refilling was required. One generator filled with 3.8 L of 10% ammonia cleaning liquid could maintain 51.24 ± 1.53 ppm for 195 h. Two ammonia generators were deployed for a six-week animal health experiment in two separate controlled environment chambers. The two ammonia generators maintained an average ammonia concentration of 46.42 ± 3.81 ppm and 45.63 ± 4.95 ppm for the duration of the experiment.

Experimental Investigation of the Effect of a Combination of Active and Passive Cooling Mechanism on the Thermal Characteristics and Efficiency of Solar PV Module

A photovoltaic (PV) module’s electrical efficiency depends on the operating temperature of the cell. Electrical efficiency reduces with increasing PV module temperature which is one of the drawbacks of this technology. This is due to the negative temperature coefficient of a PV module which decreases its voltage significantly while the current increases slightly. This study combines both active and passive cooling mechanisms to improve the electrical output of a PV module. A heat sink made up of aluminum fins and an ultrasonic humidifier were used to cool the panel. The ultrasonic humidifier was used to generate a humid environment at the rear side of the PV module. The cooling process in the study was able to reduce the temperature of the panel averagely by 14.61 °C. This reduction led to a 6.8% improvement in the electrical efficiency of the module. The average power of 12.23 W was recorded for the cooled panel against 10.87 W for the referenced module. In terms of water consumption, a total of 1.5 L was approximately consumed during the whole experimental process due to evaporation. In effect, the proposed cooling approach was demonstrated as effective.

Low Cost and Portable Laboratory Kit for Practicum Learning of Air Conditioning Process in Vocational Education

The purpose of this research is to develop alow-cost and portable air conditioning teaching and learning kits for vocational education. Unlike the existing commercial productsthat available in the market, this product is based on a low-cost concept usingsimple design,as well as affordable materials andcomponents. This research is according to a product development process flow, followed by a technical analysis and testing, especially for targeted end users. The development if this product consists of the main components of a fourinch diameter round air duct made of PVC, a blower, 5 temperature sensors, fivehumidity sensors, an air flow sensor, a refrigeration system, twoelectric heaters and an ultrasonic humidifier. In addition, this kit is relatively small with dimensions of 1500 x 600 x 700 mm and is easy to move and can be used in various places. Total analysis costs less than 3,000 USD, while commercially available offer prices are more than 5,000 USD. Thus the manufacture of this kit is suitable for developing countries with a lot of trial space and limited funding. The performance test results from this kit are also able to show psychometric processes that can be directly observed on the monitor display. Based on open-ended question, student indicated that this product facilitates their learning, improves understanding of the air conditioning process, and increases creativity in problem solving. In the future, this kitcan be integrated with computer devices so that measurement data recording can be more accurate and automatically stored safely.