An experimental study on high temperature and low oxygen air combustion

ho~cuon,Recently, much attenhon has been paid to uhliZinghidly Preheated air up to l,(XX)"C through waste gas inindustrial furnaces, in which about 15% of totalnational energy in KOrea were consumed, because ofhigh efficiency of energy savings. Moreover, one ofthree major issues in the fiscal 1996," UnderstandingEnhancement of ugh TemP~ Air COmbushon" hasbeen stUdied as successive subject in the Japanesenational Project tO reduce CO, for Protechon of earth.IntrDduction of high regenera…     

Effect of temperature and mass fraction on viscosity of crude oil-based nanofluids containing oxide nanoparticles

In this study the effects of various oxide nanoparticles on viscosity of crude oil-based nanofluid were investigated. Furthermore, the effects of temperature and mass fraction of TiO₂, NiO, Fe₂O₃, ZnO and WO₃ nanoparticles on relative viscosity of nanofluid were studied. The morphology and stability of nanoparticles were characterized by using TEM and DLS analysis. The results of characterization showed that the average nanoparticle diameter ranged from 10 to 40 nm for different oxide nanoparticles. Also the results of experiments showed that with the increment of temperature the ratio of the nanofluid viscosity to basefluid declined. Moreover, for nanofluid containing nanoparticles with higher density the relative viscosity increases significantly and with the temperature enhancement higher than 50 °C the values of relative viscosities are less than unity declaring a lower viscosity of nanofluids with respect to basefluid. Finally, an empirical correlation comprising nanoparticle density, temperature, and mass fraction was obtained based on regression analysis for estimation of relative viscosity of nanofluid. The results exhibited that the deviation of the correlation from the experimental values was mostly less than 20% and the results of other researchers agree well with the data predicted by the correlation of this study.     

An experimental study on local interfacial area concentration using a double-sensor probe

Interfacial area concentration is an important parameter in modeling the interfacial transfer terms in the two-fluid model. In this paper, the interfacial area concentration, void fraction, and bubble Sauter mean diameter for air-water bubbly flow through a vertical transparent pipe with 40 mm internal diameter was investigated experimentally using both digital high-speed camera system and a double-sensor conductivity probe. Based on the experimental data of digital high-speed camera system, the statistical models derived by different researchers for local interfacial area concentration measurement using double-sensor conductivity probe were evaluated. The results show that there are obvious differences among the values of local interfacial area concentration calculated by different statistical models even from the same probe signals. The section-averaged values of the local interfacial area concentration calculated using the statistical model by Kataoka et al. agree best with experimental data of digital high-speed camera system. Therefore, the statistical model developed by Kataoka et al. is recommended for the local measurement of interfacial area concentration using a double-sensor conductivity probe in bubbly two-phase flow. Using the verified double-sensor probe method, we carry out experiment to study the local distribution characteristic of the interfacial area concentration and void fraction in air-water bubbly flow through a vertical pipe.     

Low and intermediate temperature oxidation of ethanol and ethanol-PRF blends: An experimental and modeling study

In this brief communication, we present new experimental species profile measurements for the low and intermediate temperature oxidation of ethanol under knock-prone conditions. These experiments show that ethanol exhibits no global low temperature reactivity at these conditions, although we note the heterogeneous decomposition of ethanol to ethylene and water. Similar behavior is reported for an E85 blend in n-heptane. Kinetic modeling results are presented to complement these experiments and elucidate the interaction of ethanol and primary reference fuels undergoing cooxidation.     

Effects of temperature and salt concentration on distilled water production

The paper studies the influence of salt concentration and temperature on the distillation flow rate in a single effect multi-stage system for small water distillation units for low purchasing communities of 50 to 100 people. The distillation process has been evaporation–condensation under variable conditions: temperature of the evaporation and salt concentration. The results have shown there is a dependence of the amount of the distilled water on temperature and salt concentration whose effects are more significant as the temperature rises and salt concentration lowers. The amount of the distilled water has been increased with the use of the multistage system, 103% for sea water, and 56% for brackish water. The ratio of the quantities of distilled water for both cases, sea water and brackish water, has increased from 15.8% for one single stage to 55.7% for the four stages.     

An experimental study on the effect of ultrasonication on viscosity and heat transfer performance of multi-wall carbon nanotube-based aqueous nanofluids

Four samples of 1 wt% multi-walled carbon nanotube-based (MWCNT) aqueous nanofluids prepared via ultrasonication were thermally characterized. Direct imaging was done using a newly developed wet-TEM technique to assess the dispersion state of carbon nanotubes (CNT) in suspension. The effect of dispersing energy (ultrasonication) on viscosity, thermal conductivity, and the laminar convective heat transfer was studied. Results indicate that thermal conductivity and heat transfer enhancement increased until an optimum ultrasonication time was reached, and decreased on further ultrasonication. The suspensions exhibited a shear thinning behavior, which followed the Power Law viscosity model. The maximum enhancements in thermal conductivity and convective heat transfer were found to be 20% and 32%, respectively. The thermal conductivity enhancement increased considerably at temperatures greater than 24 °C. The enhancement in convective heat transfer was found to increase with axial distance. A number of mechanisms related to boundary layer thickness, micro-convective effect, particle rearrangement, possible induced convective effects due to temperature and viscosity variations in the radial direction, and the non-Newtonian nature of the samples are discussed.     

An experimental study on the thermal conductivity and dynamic viscosity of TiO2-SiO2 nanofluids in water: Ethylene glycol mixture

The hybrid nanofluid has been thriving among researchers due to its potential to improve heat transfer performance. Therefore, various studies on heat transfer properties need to be carried out to provide a better understanding on hybrid nanofluid performance. In this paper, the experimental work is focused on the thermal conductivity and dynamic viscosity of TiO₂-SiO₂ nanofluids in a mixture of water and ethylene glycol (EG) with volume ratio of 60:40. The stable suspension of TiO₂-SiO₂ prepared at volume concentrations of 0.5 to 3.0%. The measurements of thermal conductivity and dynamic viscosity were performed at a temperature range of 30 to 80 °C by using KD2 Pro Thermal Properties Analyser and Brookfield LVDV III Ultra Rheometer, respectively. The thermal conductivity of TiO₂-SiO₂ nanofluids was improved by increasing the volume concentration and temperature with 22.8% maximum enhancement. Besides, the viscosity of TiO₂-SiO₂ nanofluids showed evidence of being influenced by nanofluid concentration and temperature. Additionally, the TiO₂-SiO₂ nanofluids behaved as a Newtonian fluid for volume concentration up to 3.0%. The properties enhancement ratio suggested that TiO₂-SiO₂ nanofluids will aid in heat transfer for concentrations of more than 1.5% and within the range of the temperature studied. A new correlation for thermal conductivity and dynamic viscosity of TiO₂-SiO₂ nanofluids were developed and found to be precise.     

采用甲基硅油作为测定油品运动粘度所需恒温浴液体的分析与实践

通过应用实践 ,提出并说明了采用甲基硅油代替甘油作为油品粘度测定时的恒温浴液体不仅可行 ,且更有效。     

废旧轮胎与机油共裂解油气联产实验研究

由于轮胎胶粉的导热性能较差,导致胶粉颗粒裂解过程中易出现热质传递效率低、裂解油产率低、产品附加值不高等问题。文章提出废旧轮胎与机油共裂解的解决方法,在自制的固定床热解装置上进行了不同机油掺混比下混合物热解特性的实验研究,并利用热重分析仪研究了不同机油掺混比、升温速率和热解温度对废旧轮胎与机油混合物热失重行为的影响,利用气相色谱分析仪对气体产物进行了定性和定量分析,并将液体产物油精馏以分析各馏分含量。研究结果表明:胶粉、机油以及胶粉和机油的混合物的热解过程均分为3个阶段,当机油的掺混比为40%时,混合物热解的失重速率最大,为45%/min;添加的机油不仅具有导热剂作用,而且和胶粉之间存在明显的协同反应,能够促进胶粉的热解和抑制炭黑的生成,并提高热解油和热解气的产量和品质。     

Effects of temperature and substrate concentration on biological hydrogen production from starch

This study investigates the effects of temperature and substrate concentration on biological hydrogen production from starch using mixed cultures. In this work, although hydrogen was successfully produced under the thermophilic condition, stable hydrogen production was not observed under the mesophilic condition. In the thermophilic reactor, the maximum hydrogen yield was 2.8 mol H₂/mol glucose at 20 g/l-starch; however, hydrogen yield decreased drastically with the change of by-product distribution when substrate concentration was over 30 g/l-starch. A negative correlation was observed between the hydrogen yield and the total concentration of undissociated acids.     

An experimental study on thermal conductivity of MgO nanoparticles suspended in a binary mixture of water and ethylene glycol

In the present study, the effects of solid volume fraction and temperature on the thermal conductivity of MgO/water–EG (60:40) nanofluid are discussed. Samples of nanofluid are provided by two step method at different solid concentrations, including 0.1%, 0.2%, 0.5%, 0.75%, 1%, 1.5%, 2% and 3%. The experiments are performed for different temperatures ranging from 20 to 50 °C, using KD2 pro thermal analyzer which employed transient hot wire to measure thermal conductivity. The finding shows that thermal conductivity of nanofluid increases with increasing solid volume fraction or temperature. Based on the experimental data, new correlation for modeling the thermal conductivity of MgO/water–EG (60:40) for different solid volume fractions and temperatures was proposed.     

Methane steam reforming in a Pd-Ag membrane reformer: An experimental study on reaction pressure influence at middle temperature

In this experimental work, methane steam reforming (MSR) reaction is performed in a dense Pd-Ag membrane reactor and the influence of pressure on methane conversion, CO_x-free hydrogen recovery and CO_x-free hydrogen production is investigated. The reaction is conducted at 450 °C by supplying nitrogen as a sweep gas in co-current flow configuration with respect to the reactants. Three experimental campaigns are realized in the MR packed with Ni-ZrO catalyst, which showed better performances than Ni-Al₂O₃ used in a previous paper dealing with the same MR system. The first one is directed to keep constant the total pressure in both retentate and permeate sides of the membrane reactor. In the second case study, the total retentate pressure is kept constant at 9.0 bar, while the total permeate pressure is varied between 5.0 and 9.0 bar. As the best result of this work, at 450 °C and 4.0 bar of total pressure difference between retentate and permeate sides, around 65% methane conversion and 1.2 l/h of CO_x-free hydrogen are reached, further recovering 80% CO_x-free hydrogen over the total hydrogen produced during the reaction. Moreover, a study on the influence of hydrogen-rich gas mixtures on the hydrogen permeation through the Pd-Ag membrane is also performed and discussed.     

A novel phase change material containing mesoporous silica nanoparticles for thermal storage: A study on thermal conductivity and viscosity

In this research, mesoporous silica (MPSiO₂) nanoparticles were dispersed in n-octadecane as an organic phase change material (PCM) in order to produce a novel composite for thermal storage. Stable PCMs containing 1 wt.%, 3 wt.% and 5 wt.% MPSiO₂ nanoparticles (PCM/MPSiO₂) were fabricated by dispersing MPSiO₂ in PCM. MPSiO₂ particles were investigated by SEM and TEM techniques, which showed high order of porosity and spherical particles of ca. 300 nm. The thermal conductivity in both solid and liquid phases was measured by transient plane source (TPS) technique in the temperature range of 5–55 °C. A maximum thermal conductivity enhancement of 5% for 3 wt.% MPSiO₂ at 5 °C, and 6% for 5 wt.% MPSiO₂ at 55 °C was experimentally obtained. Moreover, it was observed that enhancement in thermal conductivity is non-monotonic in solid phase with increasing MPSiO₂ particle loading. The viscosity results showed that for mass fractions of nanoparticles greater than 3% in liquid PCM, the behavior of liquid is non-Newtonian. Also, the viscosity of PCM containing MPSiO₂ nanoparticles was measured to be increased up to 60% compared to the liquid PCM for 5 wt.% MPSiO₂ at 35 °C.     

An experimental study on performance and exhaust emissions of a diesel engine fuelled with tobacco seed oil methyl ester

Tobacco seeds are a by product of tobacco leaves production. To the author’s best knowledge, unlike tobacco leaves, tobacco seeds are not collected from fields and are not commercial products. However, tobacco seeds contain significant amounts of oil. Although tobacco seed oil is a non-edible vegetable oil, it can be utilized for biodiesel production as a new renewable alternative diesel engine fuel. In this study, an experimental study on the performance and exhaust emissions of a turbocharged indirect injection diesel engine fuelled with tobacco seed oil methyl ester was performed at full and partial loads. The results showed that the addition of tobacco seed oil methyl ester to the diesel fuel reduced CO and SO₂ emissions while causing slightly higher NO_x emissions. Meanwhile, it was found that the power and the efficiency increased slightly with the addition of tobacco seed oil methyl ester.     

相变蓄热装置内部温度场的理论与实验研究

对螺旋盘管相变蓄热装置性能和相变材料 (PCM)的传热特性开展理论和试验研究,建立相变蓄热装置物理和数学模型,对蓄热温度场进行了数值模拟和实验测试。结果表明 ：自然对流换热对PCM的熔化过程影响很大,当考虑自然对流时,相变蓄热速率加快,相变分层现象明显;实验实测温度与模拟温度相近,说明所建立的模型适用于相变装置内部温度场的模拟。     

An experimental study on pool boiling of milk

This research paper reports the results for convective heat transfer coefficient and nucleate boiling heat flux for pool boiling of milk during khoa making. Various indoor experiments were conducted for different heat flux inputs varying from 9638.55 to 14457.83 W/m². Experimental data obtained for pool boiling of milk were analyzed by using the Rohsenow correlation with the help of simple linear regression analysis. The convective heat transfer coefficients were estimated in the range of 334.48 to 837.78 W/m² °C for the given heat inputs. The results for heat flux were found to be varying from 3344.8 to 8377.8 W/m² at 10 °C excess temperature of the aluminum pot surface above the saturation temperature of the milk. The experimental errors in terms of percent uncertainty were also calculated. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/htj.20336     

Mothballing in power markets: An experimental study

The deregulation of many electricity markets over the last two decades raises a number of issues, among which: securing adequate investments in capacity, and the possibility of cyclical behavior in capacity, are important for security of supply. A number of policies and market mechanisms aiming for capacity adequacy and market stability exist; in this paper we focus on one of these, mothballing of generation capacity. In electricity markets, mothballing is the possibility for a power generation company to temporarily withdraw generation capacity for a time, often for a year or more. Our hypothesis is that mothballing will help to stabilize markets, but at the same time increase prices. We test this hypothesis using laboratory experiments, with a simplified model of a generic electricity market. We report an experiment with twelve markets, where subjects make investment decisions; half of them had full capacity utilization (T1) and the other half had the option to mothball capacity (T2). The predictions of the effects of mothballing were confirmed in the experimental markets: prices and generation capacity exhibit clear cycles in T1, and damped cycles in the second set of experiments, T2. Furthermore, mothballing leads to higher prices on average.     

The influence of oil viscosity and refrigerant quality on evaporator performance

The presence of oil in an evaporator degrades performance by reducing evaporator heat pick-up and by increasing the evaporator pressure drops. It can be demonstrated that there is an optimum refrigerant mass flow rate for a given refrigerant-oil combination and oil concentration. Also, oil viscosity has an effect on the evaporator performance at low oil concentrations. Finally, it is suggested that low viscosity oil be used at low oil concentrations and high viscosity oil at high oil concentrations.     

不同浓度脂肪乳对血流速度影响的实验研究

目的通过观察动脉灌注不同浓度、不同剂量脂肪乳（LE）对血流速度的影响，探讨LE作为载体的作用机制。方法以２０％和３０％LE进行动脉灌注，剂量分别为２ml 和２０ml ，分为４组:A组（２０％LE，２ml ）、B组（２０％LE，２０ml ）、C组（３０％LE，２ml ）、D组（３０％LE，２０ml ）。用２只健康杂种犬，在DSA引导下分别置管于肝动脉、脾动脉进行灌注。统计各组从导管头端对比剂显现至脾动脉、肝动脉选定点血管显影所需的帧数，并记录造影时间。结果不同浓度和剂量的LE灌注后均可减缓血流速度，但减缓的持续时间和最大减缓速度（减缓峰值）有所不同（P＜０．０５）。A组约５min血流速度恢复正常，B组需５～１０min，C组需２０min，D组需２０～３０min；流速减缓峰值于A组为１８帧（１．４４s），B组为３０帧（２．４s），C组为９帧（０．７２s），D组为１４帧（１．１２s）。结论LE经动脉灌注后均可造成局部血流速度减缓，３０％LE造成流速减缓程度比２０％LE轻，但其持续时间较长。     

An experimental investigation on heat transfer characteristics of multi-walled CNT-heat transfer oil nanofluid flow inside flattened tubes under uniform wall temperature condition

An experimental investigation on heat transfer characteristics of MWCNT-heat transfer oil nanofluid flow inside horizontal flattened tubes has been carried out under uniform wall temperature condition. Nanoparticle weight fractions were 0%, 0.1%, 0.2%, and 0.4%. The copper tubes of 14.5 mm I.D. were flattened and used as the test section of oblong shape with inside heights of 13.4 mm, 11.7 mm, 10.6 mm, and 8.6 mm. The nanofluid flowing inside the tube was heated inside a steam chamber to keep the temperature of the tube wall constant. The required data were acquired for laminar hydrodynamically fully developed regime. The effects of different parameters such as volumetric flow rate, nanoparticle weight fraction, and hydraulic diameter on the heat transfer behavior of the tested systems have been investigated experimentally. For a given flattened tube at a constant nanoparticle weight fraction, increasing volumetric flow rate results in heat transfer enhancement. In addition, as the tube profile becomes more flattened and the hydraulic diameter decreases, the heat transfer coefficient goes up at constant volumetric flow rate. Utilizing nanofluids instead of the base fluid, the heat transfer rate enhances remarkably. The higher the nanoparticles weight fraction, the more the rate of heat transfer enhancement. Finally, the results show that the amount of increase in heat transfer coefficient caused by employing nanofluid instead of the base fluid is comparable to what caused by flattening the tube.