Increased Temperature Levels Research Articles

The effects of injection rate of gaseous additives on the characteristics of liquid spray flames

An experimental study of the effects of diluent (nitrogen) injection into the near-nozzle region of a liquid (kerosene) spray flame produced from a twin-fluid atomizer is presented. The primary variable in this study is the diluent injection rate. Measurements include visible flame length, radiative fraction of heat release, axial temperature profiles, radial profiles of temperature and concentrations of carbon monoxide, oxygen, nitric oxide and soot in the far-nozzle region. Results indicate that (i) the visible flame length and radiative fraction of heat release decrease, flame temperature level increases, nitric oxide concentration increases and soot/carbon monoxide emissions decrease when diluent is injected at a rate approximately equal to the atomizing air flow rate and (ii) a further increase in rate of diluent injection does not result in proportionate amounts of changes.

Modelling the effect of shelterbelts on maize productivity under climate change: An application of the EPIC model

The potential of shelterbelts to ameliorate climate change induced crop stress, particularly in semi-arid regions such as the North American Great Plains, is examined. Specifically, the microlimate effects of shelterbelts, synthesized from empirical studies in the literature, are inserted into the Erosion-Productivity Impact Calculator (EPIC) crop model to simulate the response of dryland maize to shelter at The University of Nebraska Agricultural Research and Development Center (ARDC) near Mead, Nebraska. Though lack of extensive observed maize yield data precluded rigorous validation, the shelterbelt version of EPIC and a version simulating an unsheltered control were tested with 2 years of observed maize yield data from ARDC. EPIC underpredicted the observed ratio of shelter to open field maize yields as expected because not all benefits of shelter to crops can be incorporated into EPIC. However, the two versions correctly simulated the magnitude of difference in the shelterbelt to open field ratios between the 2 years. The two EPIC versions were then subjected to prescribed increments to temperature, and increments/decrements to precipitation and windspeed to examine differences in crop productivity between the two EPIC versions. The results show that simulated shelter increases dryland maize yields above corresponding unsheltered yields for almost all levels of climate change. The model results suggest that shelterbelts provide a night-time cooling that partially compensates the tendency of warming to shorten the growing season. They also suggest that evapotranspiration is reduced in shelter, thus reducing crop moisture stress. The positive effect of shelter on dryland maize at all levels of temperature increase is greatest for the most severe changes: maximum precipitation deficiency and greatest increase in windspeed. Despite methodological limitations, the findings suggest that shelterbelts may afford important protection from climate warming.

Study of Hydrology and Drought in the Flood Region of Sudan

ABSTRACT An attempt is made to thoroughly investigate the important hydrological features ofhe flood region that is located in the southern part of Sudan. The hydrologic data that were used in the study include temperature, precipitation, sunshine duration. radiation, humidity, wind speed, and evaporation. The investigation also includes the stream flow records of the Nile River in the region. In this region, a huge amount of the Nile water is lost by evaporation and overspilling. The hydrological data of Malakal meteorological station, taken as the index station, and the long-term flow data of the White Nile and its principal tributary, the Sobat, have been analyzed. The effect of changes in the behavior of the hydrological factors on the degree of aridity is also assessed. The study clearly indicates significant changes in the hydrological behavior of the region characterized by an increase in temperature levels and a substantial reduction in rainfall and river flows.

Combustion Wave Development in Enclosed H2/02Mixtures Enriched with Carbonaceous Particles

A one-dimensional mathematical approach is proposed to study gaseous flame reactions in the presence of reactive particles. The non-stationary model is based on the reactive Navier-Stokes equations for the gas phase, and on the reactive Euler equations for the particle phase, both phases being modeled as continua. The flux terms were treated by flux difference splitting schemes. Calculations were performed for a confined stoichiometric hydrogen/oxygen mixture enriched with carbonaceous particles and ignited y a temperature non-uniformity. The results show that the presence of particles has a damping influence on the ignition-induced pressure wave. The peak pressure and its propagation velocity decrease, and the sharp contour of the pressure wave is smeared out compared to the particle-free case. The increase of the temperature in the reaction zone is reduced due to heat absorption in case of non-reacting particles. With increasing particle reactivity, the equilibrium temperature is achieved earlier and the temperature level increases.

Histopathological changes induced by thermal exposure in the rat liver

To clarify the effects of a thermal environment on rats, histopathological changes, and temperatures in the rectum and eyes of Fischer strain rats exposed to a thermal environment of 32 degrees C for 2 days or 7 days were investigated. Thermal exposure to 32 degrees C induced elevations in rectal and ocular temperatures. The increased temperature levels persisted during the thermal exposure. Vacuolar degeneration surrounding the hepatic vein was observed in rat livers exposed to 32 degrees C for 7 days. No abnormalities were observed in other organs. These results indicate that thermal exposure to 32 degrees C induces vacuolar degeneration in hepatocytes due to the elevation of body temperature.

Surface tension measurement of aqueous polymer solutions

The surface tension of aqueous polymer solutions of polyacrylamide (PAM), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and hydroxyethyl cellulose (HEC) was studied over a range of polymer concentrations by using the maximum bubble pressure method at temperatures ranging from 20 to 65°C. The surface tension of water was also measured by the maximum bubble pressure method as well as by the DuNoüy ring method over the same temperature range. The experimental water data are in excellent agreement with the well-established tabulated data in the literature. For a fixed concentration, all of the polymer solutions exhibited a decrease in surface tension with increasing temperature level. When compared with water at a fixed temperature level, the PAM and CMC solutions showed slightly higher surface tension values, whereas the PAA solutions yielded values equal to those found for water. In the case of the HEC solutions, the measured surface tensions decreased with concentration at a fixed temperature level and were lower than the values found for water. For a concentration of 2000 wppm the surface tension values for the hydroxyethyl cellulose were of the order of 10% lower than those for water at a fixed temperature level. A comparison of the new measurements with the relatively limited previously published studies showed good agreement.

Thermal propagation of normal zone with increasing temperature level in helium-cooled and high temperature superconductors

Normal zone propagation is investigated above the maximum equilibrium current l ∗, where a superconductor has no stable state in the normal region. This monostable thermal wave is shown to have constant front velocity although its crest grows infinitely with time. Various monostable regimes are analysed by numerical simulation of zone propagation both in helium-cooled and in high T c superconductors (HTSC), and the velocity-current dependences are obtained. Unlike in HTSC, transition to monostable propagation in helium-cooled superconductors is accompanied by jump in velocity at l = l ∗. A constant coefficient model for HTSC is presented which gives analytical expressions for monostable zone velocity. Over a wide range of currents the velocity is given by universal formula dependent on normal substrate properties only. The effect of transient heat transfer is analysed.

Pressurized water reactor blockage—prediction of laminar flow and temperature distributions following a loss of coolant accident

During the unlikely occurrence of a loss of coolant accident (LOCA) in a pressurized water reactor, it has been postulated that the fuel rod cladding may swell due to the combination of a pressure differential across the cladding and the increased temperature levels in the core. In this event, adjacent fuel rods may ‘balloon’ until they make contact with their neighbours, leading to a reduction in subchannel flow area, subchannels of highly noncircular cross-section, and worsening heat transfer in the blocked region of the core. A particularly important measure in predicting an upper limit on the severity of this core blockage is the peripheral variation of the wall temperature for a representative blocked subchannel. This paper is concerned with the prediction of the temperature variations in the duct wall and the fluid for fully developed laminar flow. A single subchannel is modelled as a four-cusped duct, bounded by a conducting wall of constant thickness, which is subject to uniform heat flux from the fuel. Results for this idealized problem are presented for different values of the thickness and thermal conductivity of the cladding. The important wall temperature distributions have been calculated for superheated steam to cover fluid flow conditions which might be envisaged during a LOCA. Here it must be observed that two-phase flow effects are unlikely to lead to worse heat transfer than can be predicted for single-phase steam cooling. Thus, the predicted temperature variations represent an upper bound for the low Reynolds number end of the Reflood phase in the LOCA.

Solvent Effects on Short Time Dyeings of Acrylics

The absorption of CI basic green 4 by acrylic yam in the presence of different solvents is studied by means of the short dyeing time method. The quantity of absorbed dye is related to the dyeing temperature through an equation of the Williams-Landel- Ferry type. Using the theory of fractional contribution to the solubility parameter, linear correlations are found between the ratio of polar to nonpolar contributions to the solubility parameter and the lowering of the dyeing transition temperature of polyacrylonitrile caused by the solvents, and between the same and the quantity of absorbed dye. Increases in temperature level the effect of the different solvents on dye absorption.

NUMERICAL STUDY OF THE THERMAL PROCESSES IN A FURNACE

A detailed numerical study of the combined modes of heat transfer in a furnace is carried out. The furnace considered is a heat treatment furnace and the conjugate modes involving radiation )particularly gas radiation), conduction, and convection are considered in order to determine the transient temperature variation in the furnace and in the material undergoing heat treatment. The thermal processes are coupled through the boundary conditions and the property variations. Strong non-linearity is introduced due to the radiative heat transfer mechanisms. The nonlinear coupled system of partial differential equations is solved numerically by time marching, which allows study of the time-dependent temperature field in the system. The initial temperature of the system and the inflow temperature of the hot gases are the main inputs. Interest lies in determining the temperature decay in the gases as they flow from the inlet to the outlet and in the transient increase in temperature level in the furnace. By use o...

Numerical Study of the Thermal Processes in a Furnace

A detailed numerical study of the combined modes of heat transfer in a furnace is carried out. The furnace considered is a heat treatment furnace and the conjugate modes involving radiation )particularly gas radiation), conduction, and convection are considered in order to determine the transient temperature variation in the furnace and in the material undergoing heat treatment. The thermal processes are coupled through the boundary conditions and the property variations. Strong non-linearity is introduced due to the radiative heat transfer mechanisms. The nonlinear coupled system of partial differential equations is solved numerically by time marching, which allows study of the time-dependent temperature field in the system. The initial temperature of the system and the inflow temperature of the hot gases are the main inputs. Interest lies in determining the temperature decay in the gases as they flow from the inlet to the outlet and in the transient increase in temperature level in the furnace. By use o...

Microbial conversion of hymexazol in soil.

The metabolism of hymexazol (3-hydroxy-5-methylisoxazole) in soil was studied by using 14C-labeled chemical (14C-labeled at the 3 position on the isoxazole ring) to obtain fundamental information on its persistence in disease controlling activity and on residue analysis. Radioactive hymexazol was degraded in the unsterilized soil, and three radioactive metabolites were identified with carbon dioxide, acetoacetamide, and 5-methyl-2(3H)-oxazolone. The amount of 14CO2 evolved from radioactive hymexazoltreated soil increased with time, whereas those of the other metabolites decreased. The breakdown of hymexazol in unsterilized soil is biological, since only a trace of 14CO2 was evolved from the sterilized soil. Production of 14CO2 was remarkable in submerged condition compared to that in moist one. The amount of 14CO2 evolved from radioactive hymexazol treated soil increased with increasing temperature levels from 15C to 35C. Hymexazol was also degraded to CO2, acetoacetamide, and 5-methyl-2(3H)-oxazolone in the soil infested with Bacillus subtilis, Streptomyces griseus, Aspergillus niger, Arthrinium sp., or Penicillium sp. A certain portion of hymexazol and/or its metabolites were so tightly adsorbed by the soil that it could not be removed by extraction with 1N HCl and subsequent elution with 1N NaOH or methanol. Since acetoacetamide and 5-methyl-2(3H)-oxazolone were found to be less effective than hymexazol against Fusarium wilt of cucumber, the metabolism of hymexazol in soil can be considered as a detoxication step.

Distinctive Features of Fatigue Cracks. Application to Estimating Fatigue Life for Two-Step Temperature Test

Fatigue under varying temperature conditions and thermal fatigue are important problems for designing machines and plants used at elevated temperatures. In order to deduce a fatigue life rule under these complex conditions, it is necessary to find the physical changes which correspond to the“damage”, and then to clarify the effect of applied conditions on these changes.The authors examined the feature of cracks in the partially fatigued specimens and the effect of two-step temperature level on fatigue life.As the result of this investigation, the following conclusions have been obtained:(1) The number of cycles to failure of a low carbon steel decreases monotonously with increasing temperature level from R. T. to 600°C for a total strain range of 1%.(2) Submacro-cracks (30∼50μm depth) initiate and grow in the early stage of fatigue test at the temperature level of 500°C, but at R. T. level they do not appear until the later stage.(3) The order of application of the two temperature levels affects the fatigue life only when the upper temperature exceeds 400°C.(4) The total crack area seems to be a more realistic measure of damage, and it is useful for estimating fatigue life under the two-step temperature level test.

The Influence of Some Environmental and Cultural Conditions On Rearing Populations of Xiphinema and Longidorus1)

Trials were carried out with hand-picked populations of Xiphinema spp. and Longidorus spp. to determine the effect of different environmental and cultural conditions on the nematode multiplication rate. Using Longidorus africanus as a test organism, a four-fold population increase within 5 months was recorded in polyethylene bottles as compared with that in clay pots; population build-up of L. africanus, Xiphinema brevicolle, X. diversicaudatum, X. index, and X. italiae in polyethylene bottles was quicker in a heavy than in a light soil. The increased multiplication rates were attributed to the smaller moisture fluctuations in the polyethylene containers and the heavier soil. Population build-up of X. brevicolle, X. index, X. italiae and L. brevicaudatus was quicker, and the duration of their life cycles was shorter, with increasing temperature levels between 16 and 28°C. Soil drenches with a nutrient solution at a normally recommended concentration were found to suppress drastically populations of L. africanus, while foliar sprays with a number of pesticides had no adverse effect. Attempts to introduce a single plant variety as a standard host in cultures of Xiphinema and Longidorus spp. were unsuccessful. Among the nematodes successfully cultured to date, the Longidorus spp. appear to have a shorter life cycle than the Xiphinema spp. X. mediterraneum and all the bisexual species of the two genera tested so far, have failed to thrive well in artificial cultures.

The preparation and properties of some urethane foams from castor oil and elaidinized castor oil

SummaryThe preparation and properties of two series of castor oil urethane foams, one from castor oil and the other from elaidinized castor oil, were investigated. The first series of foams was made from prepolymers containing 60% of castor oil prepared at increasing temperature levels to vary the degree of crosslinking in the final foams. These foams had lower tensile strengths than observed for a previously prepared foam of 60% castor oil and did not show significant differences in water resistance as crosslinking varied. They were increased nearly 100% in compressive strength with increased crosslinking and had very good shrinkage characteristics as values of only 1 to 2% were obtained.A second series of foams was prepared from 50, 60, 70, and 80% of elaidinized castor oil to compare with foams from a similar series from castor oil. This series of foams of 50 to 80% elaidinized castor oil contents was similar in density (1.7 to 6.7 lbs./cu. ft.), had improved shrinkage characteristics (11, 1, 3, and 4%, respectively), showed increased compressive and tensile strengths (up to 12.1 p.s.i. at 50% compression modulus and 34.7 p.s.i. ultimate tensile for the 60% foam formulation), and had better water‐resistance properties (411 to 155%vs. 515 to 170% water absorption) than the analogous foams from castor oil. In general, humid aging only slightly affected the values obtained for the foams and was significant in only a few instances,e.g., decreased tensile in the elaidinized castor oil series.Thus increasing crosslinks in the foam apparently did not improve water resistance but did improve shrinkage characteristics in addition to some increased strength properties, as would be anticipated. Foams from elaidinized castor oil, while similar in density and foaming characteristics to analogous foams from castor oil, exhibited less shrinkage and improved water‐resistance.