Optimum Air Flow Rate Research Articles

Predictive optimization of the air flow rate for a residential heat pump in seasonal performance conditions

The seasonal performance has become increasingly important for residential heat pumps which occupy a majority of household power consumption. Thus, the heat pump system and its components are requested to be re-designed with reflecting the part load characteristics. Furthermore, actuators should be optimally operated for each test condition to maximize system efficiency. Among them, indoor and outdoor fan speeds are the only variable that can be independently controlled and have the widest operation range. Therefore, in this study, a non-iterative heat pump simulation model is presented to precisely predict the optimum air flow rate for each part load condition by introducing the modified effectiveness. The non-dimensional correlation is developed for the modified effectiveness and semi-empirical efficiency models are utilized for estimating the compressor performance. Validating experiments identify that the model can predict the optimum air flow rate for various part load conditions within an error of 10%. Consequently, the optimum air flow rate can be instantly obtained for various operating conditions.

Determining the optimal airflow rate to minimize air pollution in tunnels

With the spreading of the green environmental protection concept, increasing attention has been paid to improving the tunneling environment. In this paper, the distribution characteristics of airflow fields, the diffusion laws of pollutants, and the influence of airflow rate changes on pollutants in tunnels under single-forced ventilation conditions were simulated according to the computational fluid dynamics (CFD) theory. In addition, the reliability of the simulation results was verified through field measurements. A three-stage distribution was observed once the dust concentration stabilized: we noticed areas with relatively low dust concentrations (<300 mg/m3), high dust concentrations (>500 mg/m3), and medium dust concentrations (~400 mg/m3, near the tunnel exit). Meanwhile, after stabilizing, the gas concentration was 0.67%. Properly increasing the airflow rate (Q) can effectively improve the tunnel environment: when Q reached 600 m3/min, the air in the tunnel was effectively purified. However, under a continuous increase of the airflow rate, there is a risk of pollution rebound.We conclude that, to effectively improve the tunnel environment and achieve a sustainable utilization of resources, the optimal operation airflow rate should be 600 m3/min.

벤치규모 생물반응기에서 Shinella granuli CK-4에 의한 1,4-Dioxane의 생분해에 영향을 미치는 물리화학적 요인

Our previous research has demonstrated that Shinella granuli CK-4 is capable of utilizing 1,4-dioxane as its sole source of carbon and energy when isolated from industrial wastewater [1]. In this study, we have extended this work to investigate the relationships between 1,4-dioxane degradation and the strain CK-4 and several relevant physicochemical environmental parameters in 3 L bench-scale bioreactors. One gram of 1,4-dioxane per liter was completely degraded within 96 hours of incubation, and the optimum temperature for 1,4-dioxane degradation was 30oC. 1,4-Dioxane degradation by CK-4 gradually increased as a function of airflow rate and agitation speed, and the optimum airflow rate and agitation speed were 2.5 L/min and 500 rotation per minutes, respectively, in this study. The addition of 50 mg/L tetrahydrofuran as a supplemental carbon source was found to stimulate the maximal bacterial growth and 1,4-dioxane degradation. The optimum results obtained from these experiments were combined and applied for 1,4-dioxane degradation. As a result, the complete degradation of 1,4-dioxane was achieved with the CK-4 culture within 72 hours of incubation. We explored the feasibility of using the cultures of S. granuli CK-4 for the degradation of 1,4-dioxane with the aim of microbial application in industrial wastewater treatment in bench-scale bioreactors.

Coupling Effect of Air Flow Rate and Operating Conditions on the Performance of Electric Vehicle R744 Air Conditioning System

The air flow rate on the gas cooler side is one of the key parameters affecting the performance and running safety of transcritical CO2 electric vehicle air conditioning systems. After experimentally analyzing the effects of the air volume flow rate in the gas cooler on the cycle parameters and system performance, a novel method to evaluate the optimal air flow rate was proposed. In addition, the effect of the gas cooler air volume flow rate on the key performance parameters of the system (e.g., optimal discharge pressure) was explored. Finally, the coupling effects of the compressor speed, ambient temperature and optimal air flow rate on the system performance was also exhaustively assessed. It was found that as the discharge temperature, the CO2 temperature at the gas cooler outlet and the discharge pressure did not vary more than ±2%, the corresponding gas cooler air volume flow rate was optimal. For the single-row and dual-process microchannel evaporator used in this work, the recommended value of the optimal gas cooler air volume flow rate was 2500 m3·h−1. The results could provide reference for the fan speed design of electric vehicle CO2 air conditioning systems, especially for the performance under idling model.

Co-Design of CVT-Based Electric Vehicles

For an electric vehicle (EV) with a continuously variable transmission (CVT), a novel convex programming (CP)-based co-design method is proposed to minimize the total-cost-of-ownership (TCO). The integration of the electric machine (EM) and the CVT is the primary focus. The optimized system with co-design reduces the TCO by around 5.9% compared to a non-optimized CVT-based EV (based on off-the-shelf components) and by around 2% compared to the EV equipped with a single-speed transmission (SST). By taking advantage of the control and design freedom provided by the CVT, the optimal CVT, EM and battery sizes are found to reduce the system cost. It simultaneously finds the optimal CVT speed ratio and air-flow rate of the cooling system reducing the energy consumption. The strength of co-design is highlighted by comparing to a sequential design, and insights into the design of a low-power EV that is energy-efficient and cost-effective for urban driving are provided. A highly integrated EM-CVT system, which is efficient, low-cost and lightweight, can be expected for future EV applications.

Process optimization of S (IV) oxidation in flue gas desulfurization scrubbers

At present, the control of oxidation process is imprecise in the wet flue gas desulfurization system. In this study, a modified oxidation model is established to investigate convective mass transfer of O2 and the oxidation of S (IV) under natural and forced oxidation conditions. By comparison, the model results are in good agreement with experimental results. Based on the motion of droplet in the scrubber and bubble in the slurry pool, natural oxidation rate is calculated to provide guidance for forced oxidation and recommended oxidation air flow rate. Droplet accelerates until it reaches terminal velocity. Mass transfer resistance mainly occurs in the liquid film. The mass transfer flux of the droplet with diameter of 1.5 mm increases continuously until it remains stable. The natural oxidation rate increases with the increasing of inlet O2 concentration while the forced oxidation rate increases with the increasing of oxidation air flow rate. Several gas flow rates are taken into consideration to obtain the optimal oxidation air flow rate, showing that smaller drop diameter has positive impact on oxidation process in flue gas desulfurization scrubbers.

Analysis of Air Fuel Ratio on Combustion Flames of Mixture Waste Cooking Oil and Diesel using Preheating Method

Fossil fuels are a non-renewable energy source results in depletion of fossil fuel reserves. Utilization of used cooking oil as an alternative fuel is one solution to overcome this problem. This study objective is to design a stove fueled by waste cooking oil and determine the optimum air flow rate and fuel flow rate in combustion. This study uses the used cooking oil as the main fuel, and diesel fuel as a mixture with a mixture of 100% used cooking oil, used cooking oil 80:20, 70:30, and 60:40 to diesel fuel. Fuel valve opening variations used are ¼ open, ½ open, ¾ open, and fully open, while the variation in air flow rate used is 14.91; 19.24; 27.64; and 31.28 m/s. The fuel samples used were tested for the heating value, flash point and fire point, fuel density, and water fuel ratio (AFR) analysis and water boiling test (WBT). The results showed that used cooking oil had a heating value of 37,231.11 kJ/kg, flash point 289ºC, and fire point 305ºC. To achieve optimum AFR conditions (12-16:1) at a fuel flow rate of 2.5 mL/min (¾ valve open) and an airflow rate of 27.64 m/s, and WBT analysis with 221 mL fuel consumption requires a long time boiling water 16’23” minutes. Conversion of used cooking oil to kerosene fuel is 1 liter of used cooking oil equal to 0.3 liters of kerosene.

Numerical Investigation of Optimal Air Flowrate for Cooling 600 W Brushless Direct-Current Motor

Abstract Personal mobility devices have drawn growing attention to relieve the congestion of traffic and air pollution. The efficiency of electric motors is significant in terms of energy utilization, driving range, and lifetime of the devices. In this study, a brushless direct-current (BLDC) motor is numerically investigated to maximize the system efficiency. The inevitable energy losses in the motor are evaluated using heat sources generated in the motor components. The resulting copper and iron losses generate heat and decrease the motor efficiency. With these, the developed three-dimensional numerical model accurately predicts the temperature variations of the motor components in accordance with the experimental results. Numerical simulations are conducted by supplying air flow at a rate of 0 to 40 l/min. The results show that the decreased temperature at copper windings improves the efficiency of the motor as more air flowrate is supplied. Nonetheless, after the temperature at the copper windings reaches 42.5 °C at an air flow of 30 l/min, the temperature remains constant despite additional increase in the air flow. Through a comparison between the improved electrical work by cooling and the consumed energy to supply the air flowrate, the maximum efficiency of the air-cooled BLDC is found to be 86.3% with an optimal air flowrate of 30 l/min.

Optimizing vertical flow aerated steel slag filter system with nitrifiers bacteria for nutrients' removal from domestic wastewater: a pilot study

AbstractBACKGROUNDThe present study aimed to optimize the removal efficiency of ammonia nitrogen (NH3‐N) and total kjeldhal nitrogen (TKN) from domestic wastewater as a function of hydraulic loading rates (HLRs) (0.16–5.44 m3 m–3 day–1) and the aeration rate (3, 5 and 10 L min–1) in a vertical flow aerated steel slag filter (VFASSF) system with nitrifier bacteria. The nitrifier bacterial cell morphology was determined using scanning electron microscopy (SEM) analysis.RESULTSThe HLRs affected the performance of the VFASSF in removing TKN and NH3‐N from domestic wastewater. The optimal air flow rate for removing NH3‐N and TKN was recorded with 10 L min–1 and HLR 2.72 m3 m–3 day–1, at which the removal efficiency was &gt;91% compared to 90% and 88% with 3 L min–1 and 5 L min–1 air flow rate, respectively. The high removal was a consequence of the high aeration which enhances the nitrification process performed by the nitrifying bacteria in the VFASSF.CONCLUSIONSThese findings reflected the applicability of VFASSF in the treatment and removal of nutrients from domestic wastewater. © 2020 Society of Chemical Industry

Dual needle corona discharge to generate stable bipolar ion for neutralizing electrosprayed nanoparticles

The performances of dual needle corona discharge (NCD) as bipolar ion source to neutralize the electrospray (ES) particles were characterized and optimized. The NCD was constructed from a tungsten needle and grounded mesh electrode in the needle-to-plane configuration. The dual NCD created a bipolar ion environment by mixing the balanced concentration of positive and negative ions produced by each NCD. The dual NCD was placed in an electrospray aerosol generator (EAG) apparatus to reduce the charge state of the ES particles. Polystyrene latex (PSL) suspensions having the particle size range of 96–256 nm were used as the precursor solution for the electrospray process. Some characterizations to the NCD were carried out to obtain optimum operating voltage and air flow rate. The size distribution and charge fraction of the electrospray PSL (ES-PSL) particles exiting the EAG were also investigated. The result showed the dual NCD could generate stable bipolar ions by mixing positive and negative ions with balanced concentration. The bipolar ions from the dual NCD were capable of neutralizing and reducing the charge state of highly charged ES-PSL particles larger than 100 nm. The EAG, equipped with the dual NCD, could generate ES-PSL particles with stable concentration and consistent size distribution. The charge fraction calculation of the ES-PSL particles showed that more than 80% of the particles exiting the EAG were positively charged.

Experimental investigation and two-level model-based optimisation of a solar photovoltaic thermal collector coupled with phase change material thermal energy storage

This paper presents an experimental investigation of an air-based solar photovoltaic thermal (PVT) collector coupled with a centralised phase change material (PCM) thermal energy storage (TES) system, and the development of a model-based strategy to facilitate optimisation of the PVT-PCM systems. The originality of this study includes using statistical analysis to reveal the practical deficiencies of PVT-PCM systems, and orientating the system optimisation using a two-level model-based strategy. A set of experiments were designed and performed based on a lab-scale experimental facility to examine both electrical and thermal performance of the PVT-PCM system with various air flow rates, and different slopes and orientations of the PVT collector. The optimisation strategy was developed to identify the optimal design and at the same time to generate a performance map that can be used for control optimisation. The experimental results showed that there existed an optimal air flow rate for the PVT-PCM system under a given solar radiation for maximal overall system efficiency. To better utilise the PCM latent heat storage capacity, both the useful thermal energy generated from the PVT collector and the heat transfer within the TES unit need to be optimised. Compared to a baseline case without optimisation, the average overall system efficiency increased from 37.6% to 40.2%, and the average daily utilisation ratio of the latent TES capacity improved from 13.3% to 79.5%.

Compost Physical Properties Study on Degradation of Poultry Manure Composting in Closed-Aerated Composter

A variety of parameters including physical, chemical, and biological properties of different input materials contribute to different composting performance. This study aimed to investigate the compost physical properties (bulk density, porosity, specific surface area and water holding capacity) on the composting process at different initial moisture content (MC). The degradation of total organic carbon (TOC) for the compost inoculated with Bacillus coagulans (BC) and effective microorganism (EM) was determined. The composting materials consisted of 50 % sawdust, 12 % chicken dung and 38 % rice husk with a fixed initial C/N ratio of 30. A closed-aerated composter was fabricated with an optimum air flow rate of 0.3 L/min.kg compost to avoid O2 limitation for 7 d of composting. The compost temperature was recorded to exhibit the active reaction between microorganisms and compost materials will generate a considerable amount of heat. The effect of the initial MC of the compost bed has been intensively investigated with regards to compaction analysis and compost particle for the composting inoculated with BC or EM in an aerated closed-system composter. The results showed that composting using the single strain of BC provides comparable results to that degraded by the commercial mixed culture EM.

Numerical analysis of the effect of air pressure and oil flow rate on droplet size and tool temperature in MQL machining

Dry machining is undesirable for machining of good surface quality products, because the thermal properties of a material may contribute to a reduction of tool life when machining difficult to cut materials. Likewise, the conventional lubrication through a jet or flood cooling is not economical or eco-friendly and increases the environmental burden. Owing to the above facts it becomes necessary to implement Minimum Quantity Lubrication (MQL) in end milling process. In this study, a numerical analysis has been carried out to investigate the impact of compressed air pressure and the oil flow rate on Sauter mean diameter of MQL spray and on tool temperature. Sauter Mean Diameter (SMD) of MQL spray and temperature distribution in the end milling tool are calculated for three different air pressure (2, 3, and 4 bar) and oil flow rate (100, 150, and 200 ml/hr). ANSYS Fluent software is used for the analysis with discrete phase model (DPM) for predicting the spray particle size. From the analysis, SMD and tool temperature are found to decrease with increase in air pressure for constant oil flow rate whereas there is no considerable change in SMD as the flow rate of oil is changed beyond 150 ml/h. This study has been used for selecting the optimum air pressure and flow rate of the oil for efficient lubrication and cooling in MQL aided machining.

Evaluation of the thermal efficiency and a cost analysis of a new rice husk gas cookstove for the rural areas of Northern Thailand

ABSTRACT The objective of this study was the design and creation of a gas stove that is able to use renewable biomass as an alternative to liquefied petroleum gas. In the research, the representative sample group was located in the rural area of Lampang province of Thailand, It was found by the survey that the average time of cooking the food was 1 hour and a quantity of 1.5 kg of rice husk was used. Following this, the data was analyzed in order to determine the ideal dimensions of the combustion chamber of the rice husk gas stove, which included a height of 60 cm and a diameter of 16 cm. The copper heat exchanger tubes were installed and the air flow rate in the heat exchanger tubes was determined at five levels, which are 0.008, 0.012, 0.016, 0.020, and 0.024 m3s−1. Following this, the rice husk fuel gas test was conducted in order to compare the performance of the rice husk gas stove (RHGS) furnace using the flow rate of the boiling water. It was shown by the results that the optimal air flow rate in a copper tube for the heat exchange area and the reactor of the rice husk gas stove was 0.024 m3s−1, which refers to the RHGS-5. Under this ideal condition, it was determined that the thermal efficiency of RHGS-5 was 34%. It was also found that the levels of emission of pollutants from the rice husk fuel during the burning of the rice husks for the gas stove are suitable for use of the stove in a rural kitchen. Furthermore, the actual payback period of the RHGS-5 was calculated as approximately seven months and 28 days. In addition, the criteria for the design and operational procedures of the rice husk gas stove are also described in this article.

Development of a lightweight, 'on-bed', portable isolation hood to limit the spread of aerosolized influenza and other pathogens.

BackgroundThe annual seasonal influenza epidemics in the winter season lead to many hospital admissions, increasing risks of nosocomial infections. Infectious diseases caused by contagious respiratory pathogens also pose a great risk to hospitals as has been seen in the current epidemic by a novel coronavirus infection. Such risk occurs in high density patient settings with few or no partitions, since the pathogens are transmitted by aerosols discharged from the patients. Possible interventions against the transmission are needed.MethodsWe developed a compact, lightweight, and portable hood designed to cover just the top half of a patient sitting or lying in bed, to limit the dissemination of infectious aerosols, constructed out of lightweight pipes, transparent plastic curtains, and a fan-filter-unit (FFU). The containment efficacy of the product was tested using an aerosolized cultured influenza virus tracer and an optimal airflow rate was determined according to the test results. It was tested for use in hospital wards during the 2016–2018 influenza seasons.ResultsThe hood, named as Barrihood®, had dimensions height 172 cm, width 97 cm, length 38 cm, weighed 26 kg, and easily strolled and unfolded from its stored to its fully operational state of length 125 cm within a few minutes by a single operator. Optimal operational airflow-rate of the FFU was 420 L/min for containment of the aerosol particles. Eighty-one uninfected patients remained for 176 cumulative person-days within 1–4 m of influenza-infected patients isolated within the hood, without acquiring influenza infection.ConclusionsWith the use of the hood, secondary influenza infection cases significantly decreased, compared to previous influenza seasons. It may be suited to hospitals with not enough/no negative pressure facilities, or without enough number of individual patient isolation rooms, and could contribute to decrease the risk of nosocomial infections.

New applications of a portable isolation hood for use in several settings and as a clean hood.

BackgroundWe previously reported that we developed a compact and portable isolation hood that covers the top half of a patient sitting or lying in bed. The negative pressure inside the hood is generated by a fan-filter-unit (FFU) through which infectious aerosols from a patient are filtered. The outside area is kept clean which decreases the risk of nosocomial infections in hospital wards. We tried new applications of the hood.MethodsThe negative pressure hood was newly applied in an intensive care unit (ICU) as a place where a staff performs the practice of suctioning that generates much aerosol from the patient, as well as a waiting space for patients. Furthermore, the possibility that the hood can be converted to a positive pressure hood as a clean hood by switching the airflow direction of FFU was assessed. The cleaning efficacy of the inside of the hood was tested using an aerosolized cultured influenza virus tracer and an optimal airflow rate was determined according to the test results.ResultsThe hood, named Barrihood, was found to be competent to be used (I) for tracheal suctioning in ICU, (II) as a waiting space for a child in a nursery who suddenly showed symptoms of the disease and waiting to be picked-up by the guardian, and (III) as a waiting space in a special outpatient clinic in a hospital for COVID-19 suspected cases to prevent dissemination of airborne pathogens. The positive pressure hood was also competent in keeping clean air quality that meets the standard class 100 of NASA’s bio-clean room category.ConclusionsThe proposed new applications will broaden the range of the hood’s usage. The isolation hood could be useful in many settings to protect people outside the hood from a patient inside, or to protect an individual inside from air particles outside the hood, such as airborne pathogens, allergens, or hazardous particulate matter like PM2.5.

Performance of stratum ventilated heating for sleeping environment

Occupants show different thermal requirements in the sleeping environment in comparison with the activity environment. A new sleeping environment provided by stratum ventilation (SV) is proposed to satisfy the requirements on indoor air quality, thermal comfort and energy efficiency. This study comprehensively investigates the effects of operation parameters on heating performance of SV for the sleeping environment, using validated Computational Fluid Dynamics (CFD) simulations. The operation parameters include the supply vane angle, supply airflow rate and supply air temperature, and outdoor weather conditions. The performance parameters include the operative temperature, local partial thermal sensation (PTS), local mean age of air (LMAA), air change efficiency (ACE) and energy utilization coefficient (EUC). It is found that stratum ventilated heating renders an operative temperature distribution satisfying the occupants’ local thermal requirement in the sleeping environment, i.e., a warmer head zone relative to the body zone. Moreover, stratum ventilated heating also performs well in terms of indoor air quality and energy utilization coefficient. Among these, the maximal bed zone air change efficiency (BACE) and room zone air change efficiency (RACE) are 0.80 and 0.57 respectively, which are higher than the value of 0.5 in a conventional uniform environment. The maximal EUC of stratum ventilated heating reaches 1.45, outperforming the conventional uniform environment with a EUC of unity. Lastly, to facilitate stratum ventilated heating, the optimal supply airflow rate, supply vane angle and supply air temperature are determined upon the consideration of thermal comfort, indoor air quality and energy utilization efficiency.

The dust diffusion modeling and determination of optimal airflow rate for removing the dust generated during mine tunneling

Dust pollution produced in tunneling process can seriously threaten safety in construction and the workers’ occupational health. Aiming at improving the construction environment in the tunnel, this study combined numerical simulation and field measurement for investigating temporal-spatial evolution laws of dust diffusion in the tunnel under single press-in ventilation condition. It was found that the airflow field in the tunnel can be divided into three segments, which were located 0~10 m, 10~45 m and 45~110 m from the working face, respectively. Accordingly, dust concentration exhibited three-zone distribution pattern after reaching the stability. In order to reduce dust concentration, dust removal performance was enhanced by increasing the pressing airflow rate of the air duct (denoted as Q) within a certain range. As Q increased to 600 m³/min, dust concentration was significantly reduced by 49.6% compared with the condition when Q = 200 m³/min. Dust removal performance tended to be stable with the further increase of Q. By taking into account sustainable utilization of energy, the optimal dust-removal pressure airflow rate was determined as Qoptimal = 600 m3/min.

Influence of photobioreactor configuration on microalgal biomass production.

Biodiesel production from microalgae depends on the biomass concentration and lipid content in microalgal cells. Photobioreactors (PBRs) facilitates cultivation of microalgae and renders better process control than open systems. However, reactor configuration and consequential hydrodynamics considerably influence biomass and lipid production from microalgae. Here, four different configurations of PBRs, viz. airlift and bubble column with orifice sparger and newly designed ring sparger, were investigated. Resulting volumetric mass transfer coefficient, mixing time, and shear stress were analyzed at different air flow rates to realize their influence on biomass and lipid production from Neochloris oleoabundans UTEX 1185. Bubble column reactor with ring sparger was observed to exhibit superior performance, which was subsequently simulated using a two-phase Eulerian model to comprehend the influence of air flow rates on mixing time. The developed computational model corroborates well with the experimental findings of optimum air flow rate for maximum biomass yield in bubble column configuration.

Remediation of ciprofloxacin-contaminated soil by nanosecond pulsed dielectric barrier discharge plasma: Influencing factors and degradation mechanisms

Abstract The continuous release of antibiotics in soil environment poses a serious threat for soil and water quality and consequently human health. However, research efforts focused on the effective remediation of antibiotic-polluted soil are still very limited. In this study, a nanosecond pulsed dielectric barrier discharge (nsp-DBD) plasma system was used for the first time to remediate soil contaminated by ciprofloxacin which is one of the most widely used, persistent and genotoxic antibiotics. Various cold atmospheric plasma (CAP) operating parameters were investigated and optimized. The optimal moisture content and air flow rate were determined at 5% and 1.0 L min−1, respectively. Ciprofloxacin degradation increased with pulse voltage and pulse repetition rate and decreased with higher initial concentrations in the soil. At optimal conditions (pulse voltage 17.4 kV, pulse frequency 200 Hz), ciprofloxacin was completely degraded (~99%) in soil, at very short nsp-DBD treatment time (~3 min), with the corresponding energy efficiency being 4.6 mg/kJ. The relative distribution and identity of major ciprofloxacin degradants generated was determined by UPLC-MS analysis. This led to the generation of a degradation map that is consistent with hydroxyl radical-driven successive hydrogen atom abstractions and hydroxyl radical recombination events at the onset of the process followed by singlet oxygen mediated degradation. Interestingly, the degradation pattern observed under nsp-DBD conditions shares several aspects with the in-vivo metabolic profile of ciprofloxacin.