Technoeconomic optimization of solar natural convection hybrid hot water systems

In this paper a techno-economic model for a hybrid domestic hot water system operating under natural convection mode is presented. Three modes of auxiliary energy supply viz.

• A electric heater fitted in the solar hot water tank.
• B electric heater fitted in a small water tank in series with the solar hot water tank, and
• C an instant electric heater fitted in the tap

have been considered. Taking into account the life and the capital and maintenance costs of the solar and electrical equipments, the cost of useful energy (Rs/kWh) has been calculated for different values of the collector area and the tank capacity, and thereby the optimum collector area and tank capacity (for a given demand), corresponding to minimum cost of useful energy, has been determined. From numerical calculations made for the climate of Delhi, India (a representative composite climate) corresponding to the two cases of monthly hot water demand viz. (i) constant monthly demand, and (ii) variable monthly demand, it is seen that case (C) is the most economic design of the hybrid hot water system; numerical calculations have also been made for this case corresponding to the climates of Srinagar and Madras (representing cold and hot climates). The effect of government subsidy on the optimized values of collector area, tank capacity and cost of useful energy has also been investigated for the climate of Delhi.     

Additive manufactured portable vertical axis windmill

ABSTRACT

The vertical axis windmill is a type of wind turbine in which the main rotor shaft is set vertically. The main aim of this is to make it more compatible and accessible. According to the research, there is plenty of enough wind available globally to meet the human energy requirements – if it is harvested on a large scale effectively. If the wind turbine efficiency is increased, then there is a chance for more power generation and to drastically decrease the use of power generators which are rather expensive and also cause pollution. In comparison to horizontal axis wind turbines, the vertical axis wind turbines may be efficient as them and are also cheaper to build and maintain. In this paper, we designed and fabricated a vertical axis wind turbine and fabricated the same using the ‘3D printing technique’ which is one of the additive manufacturing processes used now.     

Effect of fermentation on HCl-extractability of minerals from rice-defatted soy flour blend

Buttermilk fermentation at 25, 30 and 35°C for 12, 18 and 24 h brought about a significant increase in non-phytate and HCl-extractable phosphorus with a corresponding decline in phytate phosphorus of a rice-defatted soy flour blend mixed in a 50 : 50 proportion. The HCl-extractabilities of calcium, iron, zinc, copper and manganese from the rice-defatted soy flour blend also improved. Higher HCl-extractability of minerals may be partly ascribed to the decreased content of phytic acid, as a significant negative correlation between the phytic acid and HCl-extractability of dietary essential minerals was obtained.     

Sick building syndrome—A case study in a multistory centrally air-conditioned building in the Delhi City

Recently, airtight envelope system has become popular in the design of office buildings to reduce heating and cooling loads. Maintaining allowable indoor air quality (IAQ) for such airtight buildings totally depends on mechanical ventilation systems. Subsequently, poor operation of the ventilation system in such office buildings causes ineffective removal of polluted indoor air, and displays a sign of “sick building syndrome” (SBS). User's perception is an important parameter for evaluating IAQ. A questionnaire study was carried out to investigate the prevalence of the SBS at a multistory centrally air-conditioned Airport Authority of India (AAI) building in the New Delhi city. Quantification of the perceptions of the users regarding IAQ was done by converting their responses to a SBS score. The quantified answers were then subjected to statistical analysis. Qualitative analysis of the questionnaire was carried out to evaluate relationships between SBS score and carbon dioxide (CO₂) and other parameters related to building and work environment. Quantitative analysis of IAQ was also conducted by monitoring indoor concentrations of four pollutants, namely, nitrogen dioxide (NO₂), sulphur dioxide (SO₂), suspended particulate matter (SPM) and carbon monoxide (CO). Concentrations of pollutants were complying with IAQ standards as given by ASHRAE and WHO. The SBS was higher on the third floor as compared to other floors and the control tower. The main symptoms prevailing were headache (51%), lethargy (50%), and dryness in body mucous (33%). The third floor and the control tower were affected by infiltration, mainly from entrance doors. A direct relation between the average SBS score and CO₂ concentration was found, i.e., the average SBS score increased with CO₂ concentration and vice versa, clearly signifying the usefulness of SBS score in IAQ.     

Occurrence of rota- and enteroviruses in drinking and environmental water in a developing nation

Rotaviruses have been implicated as a major cause of childhood and traveler's diarrhea in developing countries. Since water is known to be a vehicle of transmission of other enteric viruses, we sought to determine if water could play a role in the transmission of rotavirus infections in a developing nation by applying recently developed techniques for the concentration of viruses from tapwater and environmental (lake, river, ocean and aqueduct) water in Mexico. In an initial survey during the rainy season in August 1978, rotavirus was detected in 10 of 10 drinking water samples and coxsackie B4 or B6 virus in 5 of 10. In a larger survey during the dry season in December 1979, rotavirus was recovered from 3 and enteric viruses from 8 of 21 drinking water samples. Water quality data, available for the 1979 survey, indicated that while many tapwater samples did not meet U.S. coliform standards, some samples containing infectious virus did. Our data suggest that current bacteriological water quality standards for potable water do not reflect viral contamination.     

Efficacy of commonly used disinfectants for the inactivation of calicivirus on strawberry, lettuce, and a food-contact surface

Norwalk and Norwalk-like viruses (NLVs) are important causes of foodborne gastroenteritis in restaurant-related outbreaks. Efficacy of common disinfection methods against these viruses on food-contact surfaces and fresh produce is not known partially because of their nonculturability. Seven commercial disinfectants for food-contact surfaces and three sanitizers for fruits and vegetables were tested against cultivable feline calicivirus (FCV). Disks of stainless steel, strawberry, and lettuce were contaminated with known amounts of FCV. The disinfectants were applied at one, two, and four times the manufacturer's recommended concentrations for contact times of 1 and 10 min. The action of disinfectant was stopped by dilution, and the number of surviving FCVs was determined by titration in cell cultures. An agent was considered effective if it reduced the virus titer by at least 3 log10 from an initial level of 10(7) 50% tissue culture infective dose. None of the disinfectants was effective when used at the manufacturer's recommended concentration for 10 min. Phenolic compounds, when used at two to four times the recommended concentration, completely inactivated FCV on contact surfaces. A combination of quaternary ammonium compound and sodium carbonate was effective on contact surfaces at twice the recommended concentration. Rinsing of produce with water alone reduced virus titer by 2 log10. On artificially contaminated strawberry and lettuce, peroxyacetic acid and hydrogen peroxide was the only effective formulation when used at four times the manufacturers' recommended concentration for 10 min. These findings suggest that FCV and perhaps NLVs are very resistant to commercial disinfectants. However, phenolic compounds at two to four times their recommended concentrations appear to be effective at decontaminating environmental surfaces and may help control foodborne outbreaks of calicivirus in restaurants.     

Enhanced production of α‐amylase from Bacillus subtilis subsp. spizizenii in solid state fermentation by response surface methodology and its evaluation in the hydrolysis of raw potato starch

This is an attempt to lower the cost of starch hydrolysis by the discovery of new generation α‐amylase. A natural isolate of Bacillus subtilis subsp. spizizenii was capable of producing appreciable amounts of raw potato starch digesting α‐amylase in solid state fermentation of wheat bran. The enzyme productivity has been substantially enhanced by supplementing various nutrients and statistically studying their interactions by response surface methodology. A central composite design for amylase production system elucidated a wheat bran‐based medium supplemented with soybean meal, threonine, and B‐complex vitamins predicting a yield of 521 391 U/g dry solids. The enzyme preparation could effectively digest 5–15% suspension of insoluble potato starch in 6 h revealing the dextrose equivalent of 32–44. The supplementation of a glucoamylase preparation, thereafter, brought about complete saccharification. The yield achieved in the statistically optimized amylase system may be one of the best to date and its capability in directly liquefying raw potato starch granules makes this study novel.     

Adsorption of chromium by activated carbon from aqueous solution

Adsorption isotherms of Cr(III) and Cr(VI) ions on two samples of activated carbon fibres and two samples of granulated activated carbons from aqueous solutions in the concentration range 20–1000 mg/l have been studied. The adsorption isotherms have been determined after modifying the activated carbon surfaces by oxidation with nitric acid, ammonium persulphate, hydrogen peroxide and oxygen gas at 350°C and after degassing at different temperatures. The adsorption of Cr(III) ions increases on oxidation and decreases on degassing. On the other hand, the adsorption of Cr(VI) ions decreases on oxidation and increases on degassing. The increase of Cr(III) and the decrease of Cr(VI) on oxidation and the decrease of Cr(III) and the increase of Cr(VI) on degassing have been attributed to the fact that the oxidation of the carbon surface enhances the amount of acidic carbon–oxygen surface groups while degassing eliminates these surface groups. Thus while the presence of acidic surface groups enhances the adsorption of Cr(III) cations, it suppresses the adsorption of Cr(VI) anions.     

QoS and multipoint support for multimedia applications over the ATMABR service

Multimedia applications with stringent delay requirements are usually supported by the constant bit rate (CBR) or real-time variable bit rate (rt-VBR) service categories of ATM. This article shows that the available bit rate (ABR) service, which was originally designed for data, can also support multimedia applications under certain circumstances. Issues related to the design of proper ABR traffic management algorithms for such support are presented     

Impact of Dual Material Gate Design and Retrograde Channel Doping on β-Ga2O3 MOSFET for High Power and RF Applications

Silicon - In the present work, dual material gate design and retrograde doping has been implemented on lateral β-Ga2O3 MOSFET with the aim to improve Power Figure of Merit (PFoM) as well as to...