scholarly journals Price-performance comparison of HEPA air purifiers and lower-cost MERV 13/14 filters with box fans for filtering out SARS-Cov-2 and other particulate aerosols in indoor community settings

2021 ◽  
Author(s):  
Devabhaktuni Srikrishna
Keyword(s):  
Lower Cost ◽  
High Efficiency ◽  
Filter Design ◽  
Low Noise ◽  
Delivery Rate ◽  
High Price ◽  
Noise Generation ◽  
Clean Air ◽  
Hvac Filters ◽  
Do It Yourself

BackgroundSARS-Cov-2 aerosols have potential to accumulate in airspaces of poorly ventilated, indoor spaces such as classrooms, offices, homes, restaurants, and bars. Separately, toxic aerosol pollution (e.g. wildfires, wood burning) is frequently encountered in these locations with ventilation relying on outside air. Portable high efficiency particulate air (HEPA) air purifiers are useful to remove both types of aerosols without relying on outside ventilation. To meet or exceed recommended 4 to 6 air exchanges per hour (ACH), high price-points for select HEPA air purifier models without incurring excessive noise generation make them unaffordable for many households and communities. Do-it-yourself (DIY) alternatives with box-fans and HVAC filters can be much lower cost but their clean air delivery rate (CADR) and noise generation varies greatly depending on choices of filters, number of filters, and fan speeds.ObjectiveTo compare cost-effectiveness and noise-generation of aerosol filtration by commercially available, portable HEPA air purifiers and do-it-yourself (DIY) alternatives built from box fans and HVAC filters rated at MERV 13 or 14 using single and quad filter designs.MethodsThe comparison is based on three metrics: clean air delivery rate (CADR), the noise generated (dBA), and affordability ($$) using an ISO-certified aerosol measurement device to measure input/output particle filtration of particles sizes ranging from 0.3 microns to 10 microns, airspeed meter to measure airflow, and NIOSH sound meter app to measure noise.ResultsAccounting for reduced filtration efficiency of MERV 13/14 filters compared to HEPA, estimated clean air delivery rate (CADR) of a do-it-yourself (DIY) setup using 2” and 4” filters with a box fan running at fan speed 1 for tolerable noise was 278 cfm ($38) to 371 cfm ($58), comparable or better than a commercial HEPA air purifiers running at maximum speed with low noise generation at 282 cfm ($375). However the quad filter designs, popularly known as the Corsi-Rosenthal box, achieved gains in CADR of only 60% over a single filter design but in contrast to 200-250% gains reported by UC-Davis.ConclusionsDIY alternatives using single 1”, 2” and 4” MERV 13/14 filters compare favorably to commercially available systems in terms of estimated CADR and noise but at five to ten times lower cost. Compared to use of one filter, an improvement in CADR (air flow) was observed with a popular DIY configuration involving quad filter design, popularly known as the Corsi-Rosenthal box, not as high as reported by a recent study by UC-Davis

scholarly journals Characterizing the performance of a DIY air filter

2022 ◽  
Author(s):  
Rachael Dal Porto ◽  
Monet Kunz ◽  
Theresa Pisotchini ◽  
Richard L Corsi ◽  
Christopher D Cappa
Keyword(s):  
Suspended Particle ◽  
Decay Rates ◽  
Delivery Rate ◽  
Indoor Environments ◽  
Air Filtration ◽  
Air Filter ◽  
Clean Air ◽  
Do It Yourself ◽  
Fan Speed

Air filtration serves to reduce concentrations of particles in indoor environments. Most standalone, also referred to as portable or in-room, air filtration systems use HEPA filters, and cost generally scales with the clean air delivery rate. A 'do-it-yourself' lower-cost alternative, known as the Corsi-Rosenthal Box, that uses MERV-13 filters coupled with a box fan has been recently proposed, but lacks systematic performance characterization. We have characterized the performance of a five-panel Corsi-Rosenthal air filter. Measurements of size-resolved and overall decay rates of aerosol particles larger than 0.5 microns emitted into rooms of varying size with and without the air filter allowed for determination of the apparent clean air delivery rate, both as a function of size and integrated across particle sizes. The measurements made in the different rooms produced similar results, demonstrating the robustness of the method used. The size-integrated apparent clean air delivery rate increases with fan speed, from about 600 to 850 ft3 min-1 (1019 to 1444 m3 h-1). Overall, our results demonstrate that the Corsi-Rosenthal filter efficiently reduces suspended particle concentrations in indoor environments.

Microcalorimeters for X-Ray Spectroscopy

1988 ◽  
Vol 102 ◽  
pp. 41
Author(s):  
E. Silver ◽  
C. Hailey ◽  
S. Labov ◽  
N. Madden ◽  
D. Landis ◽  
...  
Keyword(s):  
High Resolution ◽  
High Efficiency ◽  
Thermal Response ◽  
Low Noise ◽  
High Resolution Spectroscopy ◽  
Superconducting Transition ◽  
Sapphire Substrates ◽  
Laboratory Plasmas ◽  
Adiabatic Demagnetization ◽  
Theoretical Predictions

The merits of microcalorimetry below 1°K for high resolution spectroscopy has become widely recognized on theoretical grounds. By combining the high efficiency, broadband spectral sensitivity of traditional photoelectric detectors with the high resolution capabilities characteristic of dispersive spectrometers, the microcalorimeter could potentially revolutionize spectroscopic measurements of astrophysical and laboratory plasmas. In actuality, however, the performance of prototype instruments has fallen short of theoretical predictions and practical detectors are still unavailable for use as laboratory and space-based instruments. These issues are currently being addressed by the new collaborative initiative between LLNL, LBL, U.C.I., U.C.B., and U.C.D.. Microcalorimeters of various types are being developed and tested at temperatures of 1.4, 0.3, and 0.1°K. These include monolithic devices made from NTD Germanium and composite configurations using sapphire substrates with temperature sensors fabricated from NTD Germanium, evaporative films of Germanium-Gold alloy, or material with superconducting transition edges. A new approache to low noise pulse counting electronics has been developed that allows the ultimate speed of the device to be determined solely by the detector thermal response and geometry. Our laboratory studies of the thermal and resistive properties of these and other candidate materials should enable us to characterize the pulse shape and subsequently predict the ultimate performance. We are building a compact adiabatic demagnetization refrigerator for conveniently reaching 0.1°K in the laboratory and for use in future satellite-borne missions. A description of this instrument together with results from our most recent experiments will be presented.

scholarly journals A High Efficiency Low Noise RF-to-DC Converter Employing Gm-Boosting Envelope Detector and Offset Canceled Latch Comparator

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1078
Author(s):  
Thi Thuy Pham ◽  
Dongmin Kim ◽  
Seo-Hyeong Jeong ◽  
Junghyup Lee ◽  
Donggu Im
Keyword(s):  
Power Consumption ◽  
High Efficiency ◽  
Supply Voltage ◽  
Current Source ◽  
Low Noise ◽  
The Body ◽  
Common Source ◽  
Conversion Gain ◽  
Input Transistor ◽  
Envelope Detector

This work presents a high efficiency RF-to-DC conversion circuit composed of an LC-CL balun-based Gm-boosting envelope detector, a low noise baseband amplifier, and an offset canceled latch comparator. It was designed to have high sensitivity with low power consumption for wake-up receiver (WuRx) applications. The proposed envelope detector is based on a fully integrated inductively degenerated common-source amplifier with a series gate inductor. The LC-CL balun circuit is merged with the core of the envelope detector by sharing the on-chip gate and source inductors. The proposed technique doubles the transconductance of the input transistor of the envelope detector without any extra power consumption because the gate and source voltage on the input transistor operates in a differential mode. This results in a higher RF-to-DC conversion gain. In order to improve the sensitivity of the wake-up radio, the DC offset of the latch comparator circuit is canceled by controlling the body bias voltage of a pair of differential input transistors through a binary-weighted current source cell. In addition, the hysteresis characteristic is implemented in order to avoid unstable operation by the large noise at the compared signal. The hysteresis window is programmable by changing the channel width of the latch transistor. The low noise baseband amplifier amplifies the output signal of the envelope detector and transfers it into the comparator circuit with low noise. For the 2.4 GHz WuRx, the proposed envelope detector with no external matching components shows the simulated conversion gain of about 16.79 V/V when the input power is around the sensitivity of −60 dBm, and this is 1.7 times higher than that of the conventional envelope detector with the same current and load. The proposed RF-to-DC conversion circuit (WuRx) achieves a sensitivity of about −65.4 dBm based on 45% to 55% duty, dissipating a power of 22 μW from a 1.2 V supply voltage.

Development of a New Design Method for High Efficiency Swept Low Pressure Axial Fans With Small Hub/Tip Ratio

2014 ◽  
Author(s):  
Thore Bastian Lindemann ◽  
Jens Friedrichs ◽  
Udo Stark
Keyword(s):  
High Efficiency ◽  
Design Method ◽  
Tangential Velocity ◽  
Pressure Rise ◽  
Low Pressure ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Angle Distribution ◽  
Sweep Angle ◽  
Reduced Pressure

For a competitive low pressure axial fan design low noise emission is as important as high efficiency. In this paper a new design method for low pressure fans with a small hub to tip ratio including blade sweep is introduced and discussed based on experimental investigations. Basis is an empirical axial and tangential velocity distribution at the rotor outlet combined with a distinctive sweep angle distribution along the stacking line. Several fans were designed, built and tested in order to analyze the aerodynamic as well as the aeroacoustic behavior. For the aerodynamic performance particular attention was paid to compensate the influence of reduced pressure rise and efficiency due to increasing blade sweep. This was achieved by a method of increasing the blade chord depending on the local sweep angle which is based on single airfoil data. The tested fans without this compensation revealed a significant noise reduction effect of up to approx. 6 dB(A) for a tip sweep angle of 64° which was accompanied by an unsatisfactory effect of reduced overall aerodynamic performance. The second group of fans did not only confirm the method of the aerodynamic compensation by a nearly unchanged pressure rise and efficiency characteristic but also revealed an increased aeroacoustic benefit of in average 9.5 dB(A) compared to the unswept version. Beside the overall characteristics the individual differences between the designs are also discussed using results of wall pressure measurements which show some significant changes of the blade tip flow structure.

Development of High Efficiency and Low Noise Cross-Flow Fans for Room Air Conditioner Indoor Unit

2014 ◽  
Author(s):  
Hironobu Yamakawa
Keyword(s):  
High Efficiency ◽  
Length Distribution ◽  
Cross Flow ◽  
Low Noise ◽  
Navier Stokes ◽  
Outer Diameter ◽  
Air Conditioner ◽  
Blade Edge ◽  
Sinusoidal Shape ◽  
Cross Flow Fan

Cross flow fans are used for fan systems in a household room air conditioner indoor unit. In recently, in the view of environmental problem and cost saving, energy saving performance is important specification for users. Reducing fan motor electric power consumption is effective for this purpose. And also low noise fans are needed for comfortable circumferences. To meet these user needs, we developed a high efficiency and silent cross flow fan using CFD (Computational Fluid Dynamics) and experiments. In CFD, numerical model is calculated by commercial software using steady state, Reynolds-averaged Navier-Stokes (RANS) and k-ε turbulent flow model. The developed cross flow fan is geometrically characterized by the solidity (the ratio of the blade pitch and blade cord length) distribution, and the blade edge shape. The solidity average of developed fan was larger than the conventional fan and the solidity distribution was smooth. And the developed fan has the sinusoidal shape of the outer diameter edge. This sinusoidal shape edge makes pressure distribution on the tongue to be more dispersed compare to that of conventional straight edge so that tonal noise was restrained.

Permanent Magnet Heater for Special Applications

2015 ◽  
Vol 792 ◽  
pp. 476-481
Author(s):  
Michele Forzan ◽  
Fabrizio Dughiero
Keyword(s):  
Magnetic Field ◽  
Rare Earth ◽  
Induction Heating ◽  
Permanent Magnets ◽  
Lower Cost ◽  
High Efficiency ◽  
Mechanical Design ◽  
Fixed Position ◽  
Dc Magnetic Field ◽  
Research Activities

This paper presents a review of the research activities carried out at the Laboratory for Electroheat of Padova University (LEP) in the field of high efficiency through heating of aluminum workpieces. Induction heating obtained by rotating a billet in a DC magnetic field produced by superconductive coils was the first attempt to reach high electrical efficiency in mass heating of high conductive metals, like aluminum, copper and brass. More recently, the same concept has been applied by rotating rare earth permanent magnets around a metal billet kept in a fixed position. This technology appears much more promising because of lower cost of installation and a more robust mechanical design.

scholarly journals Flow-Induced Vibration on the Control Valve with a Different Concave Plug Shape Using FSI Simulation

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Akram Zeid ◽  
Mohamed Shouman
Keyword(s):  
High Efficiency ◽  
Complex Structure ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Simulation ◽  
Control Valve ◽  
Low Noise ◽  
Flow Induced Vibration ◽  
Nonlinear Characteristics ◽  
Flow Phenomena

Control valves have always been recognised as being among the most crucial control equipment, commonly utilised in versatile engineering applications. Hence, the need has arisen to identify the flow characteristics inside the valve, together with the incurred vibration induced as a result of the flow passing through the valve. Thanks to the tangible and fast progress made in the field of the flow simulation and numerical techniques, it has become possible to better observe the behavior of the flow passing inside a valve with view to examining its performance. Hence, the paper at hand is mainly concerned with introducing the modeling and simulation of a control valve. On the contrary, the flow system in a control valve is marked by a complex structure and nonlinear characteristics. The reasons for those qualities could be attributed to its construction as well as the fluid flow phenomena associated with it. It is especially for the sake of investigating and observing the flow characteristics, pertaining to a control valve equipped with different concave plug shapes and different openings, that the three-dimensional FSI simulation is conducted. In addition, it would be possible to make use of the obtained results relating to the three-dimensional analysis to achieve low noise and high efficiency improvement. Furthermore, all results will be validated on experimental grounds.

scholarly journals Facile preparation of low-cost HKUST-1 with lattice vacancies and high-efficiency adsorption for uranium

RSC Advances ◽  
2019 ◽  
Vol 9 (18) ◽  
pp. 10320-10325 ◽  
Author(s):  
Aili Yang ◽  
Ping Li ◽  
Jingrong Zhong
Keyword(s):  
Benzoic Acid ◽  
Lower Cost ◽  
High Efficiency ◽  
Low Cost ◽  
Uranium Removal ◽  
Facile Preparation ◽  
Lattice Vacancies

HLV was prepared using benzoic acid with lower cost as the modulator to replace part of the traditional ligand H3BTC for uranium removal.

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