Fractional Ammonium Research Articles

The Effects of Adding Lactic Acid Bacteria and Cellulase in Oil Palm (Elais Guineensis Jacq.) Frond Silages on Fermentation Quality, Chemical Composition and in Vitro Digestibility

The main objective of the current study was to evaluate whether oil palm frond (OPF) can be successfully ensiled without or with the additives cellulase or lactic acid bacteria (LAB). Thus, fresh OPF was ensiled either without additives or with cellulase or LAB or their combination. Ensiling was carried out by storing 2 kg samples in airtight glass jars at 25-30°C for 12 weeks. Thereafter, the silage samples were subjected to proximate analyses, an in vitro digestibility assay and measures on selected indices of fermentation. Fermentation of OPF without additives appeared to be unsuccessful as both pH and ammonia content were too high (4.9 and 9.9%, respectively). In contrast, the use of cellulase or LAB resulted in silages with a pH<4.5 and ammonia fractions <8.4%, but the lowest values were found when both cellulase and LAB were used, i.e. pH=4.1 and ammonia fraction=6.7%. In vitro digestibility of dry matter was significantly higher in the cellulase treated silages. The process of ensiling was associated with both a significant decrease of the fat content of OPF and a significant change of the fatty acid profile. However, the proportions of major fatty acids (C16:0 and C18:2n-6) were not affected by the process of ensiling. In conclusion, the use of cellulase additive appears a practical tool to safeguard the process of fermentation. Using a cellulase enzyme or its combination with LAB improves the fermentation profile and increases the nutritional value of the OPF silage.

Effect of a Composite Phytochemical Feed Additive onIn VitroSubstrate Degradation and Methanogenesis andIn VivoRumen Fermentation

The present study was carried out to evaluate the potential of a composite phytogenic feed additive (cPFA) on rumen fermentation characteristics under in vitro as well as in vivo conditions. The cPFA was formulated using different parts of 11 herbal plants, well acclaimed for their therapeutic virtues. Graded levels (0, 1.0, 1.5, 2.0, 2.5, 5.0, 7.5 and 10%) of cPFA were supplemented to the basal substrate and incubated with rumen liquor of sheep for in vitro gas production test and methanogenesis. For in vivo study 28 Malpura hogget lambs (7–8 months; 17.8±2.04 kg) were divided in four equal groups and fed diets supplemented with cPFA at 0 (Control), 1.0 (L-cPFA), 1.5 (M-cPFA) and 2.0 (H-cPFA) percent of feed intake. At the end of experimental feeding of 180d, rumen liquor was collected at 4h post feeding. Results indicated that, in vitro supplementation of cPFA reduced (P<0.05) total gas production and improved (P<0.05) the microbial biomass production. There was a linear increase (P<0.05) in ammonia concentration accompanied by a reduction (P<0.05) in acetate concentration. There emerged a linear decrease (P<0.05) in methane production up to a level of 5% cPFA supplementation. In vivo study revealed that there was no effect of cPFA supplementation on pH, ammonia and different nitrogen fractions in strained rumen liquor (SRL) among the groups; however, a trend of improvement in the total N was evident in cPFA supplemented groups when contrasted against control. The level of 1.5 and 2.0% cPFA supplementation showed higher (P=0.02) acetate concentration values. The cPFA supplementation did not have significant effect on enzyme activities of CMCase, avicellase and xylanase in the SRL. The present study revealed that supplementation of cPFA at level of 1.5–2.0% level possesses a potential to modulate rumen fermentation both under in vitro as well as in vivo conditions.

Energy and Exergy Analysis of the Kalina Cycle for Use in Concentrated Solar Power Plants with Direct Steam Generation

In concentrated solar power plants using direct steam generation, the usage of a thermal storage unit based only on sensible heat may lead to large exergetic losses during charging and discharging, due to a poor matching of the temperature profiles. By the use of the Kalina cycle, in which evaporation and condensation takes place over a temperature range, the efficiency of the heat exchange processes can be improved, possibly resulting also in improved overall performance of the system. This paper is aimed at evaluating the prospect of using the Kalina cycle for concentrated solar power plants with direct steam generation. The following two scenarios were addressed using energy and exergy analysis: generating power using heat from only the receiver and using only stored heat. For each of these scenarios comparisons were made for mixture concentrations ranging from 0.1 mole fraction of ammonia to 0.9, and compared to the conventional Rankine cycle. This comparison was then also carried out for various turbine inlet pressures (100bar to critical pressures). The results suggest that there would be no benefit from using a Kalina cycle instead of a Rankine cycle when generating power from heat taken directly from the solar receiver. Compared to a baseline Rankine cycle, the efficiency of the Kalina cycle was about around 5% lower for this scenario. When using heat from the storage unit, however, the Kalina cycle achieved efficiencies up to 20% higher than what was achieved using the Rankine cycle. Overall, when based on an average assumed 18hours cycle, consisting of 12hours using heat from the receiver and 6hours using heat from the storage, the Kalina cycle and Rankine cycle achieved almost equal efficiencies. A Kalina cycle operating with an ammonia mole fraction of about 0.7 returned an averaged efficiency of about 30.7% compared to 30.3% for the Rankine cycle.

Is vehicular emission a significant contributor to ammonia in the urban atmosphere?

To investigate emissions of NH3 from on-road vehicles and their contribution to atmospheric NH3, we analyzed a suite of measurements including NH3, NO, SO2, black carbon (BC), NH4+ in PM2.5, etc., collected in summer 2007 at a site near a highway with the highest traffic density in Canada. From 26 to 28 August 2007, large variations of NO mixing ratio (from <1 ppb to >110 ppb) and BC concentration (from <0.5 to >6 μg m−3) were simultaneously observed and were found to be associated with varying contributions of air pollutants emitted by vehicles on the highway. Using NO as a tracer of vehicular plumes, the estimated emission factor of NH3 relative to NO from on-road vehicles was less than 0.5–0.9 ppb NH3 per 50 ppb NO. The average mixing ratios of NH3 and NO during the three days were 4.0 ± 2.4 ppb and 23 ± 33 ppb, respectively. The NH3 derived from on-road vehicular emissions was estimated to be less than 0.4 ppb on average during the measurement period, accounting for ∼10% of the mixing ratio of NH3 measured at the sampling site. Several spikes of NH3 were observed on these days with the maximum mixing ratio of NH3 reaching 16.9 ppb. The observed spikes of NH3 were probably ascribed to non-traffic emissions of NH3 near the sampling site. We conclude that emissions of NH3 from on-road vehicles only accounted for a much small fraction of urban atmospheric ammonia, and more important sources are yet to be identified. However, it is still unknown whether negligible emissions of NH3 from vehicles in Toronto are just the result of its local traffic composition or they are generally true world wide. In addition, the negligible emissions could also be due to unknown loss in the GP-IC, although it is not found so far.

Sanitation ability of anaerobic digestion performed at different temperature on sewage sludge

A small amount of ammonia is used in full-scale plants to partially sanitize sewage sludge, thereby allowing successive biological processes to enable the high biological stability of the organic matter. Nevertheless, ammonia and methane are both produced during the anaerobic digestion (AD) of sludge. This paper describes the evaluation of a lab-scale study on the ability of anaerobic process to sanitize sewage sludge and produce biogas, thus avoiding the addition of ammonia to sanitize sludge.According to both previous work and a state of the art full-scale plant, ammonia was added to a mixture of sewage sludge at a rate so that the pH values after stirring were 8.5, 9 and 9.5. This procedure determined an ammonia addition lower than that generally indicated in the literature. The same sludge was also subjected to an AD process for 60days under psychrophilic, mesophilic and thermophilic conditions. The levels of fecal coliform, Salmonella spp. helmints ova, pH, total N, ammonia fractions and biogas production were measured at different times during each process.The results obtained suggested that sludge sanitation can be achieved using an AD process; however, the addition of a small amount of ammonia was not effective in sludge sanitation because the buffer ability of the sludge reduced the pH and thus caused ammonia toxicity.Mesophilic and thermophilic AD sanitized better than psychrophilic AD did, but the total free ammonia concentration under the thermophilic condition inhibited biogas production. The mesophilic condition, however, allowed for both sludge sanitation and significant biogas production.

Temperature- and pH-dependent aqueous-phase kinetics of the reactions of glyoxal and methylglyoxal with atmospheric amines and ammonium sulfate

Reactions of glyoxal (Glx) and methylglyoxal (MG) with primary amines and ammonium salts may produce brown carbon and N-containing oligomers in aqueous aerosol. 1H NMR monitoring of reactant losses and product appearance in bulk aqueous reactions were used to derive rate constants and quantify competing reaction pathways as a function of pH and temperature. Glx + ammonium sulfate (AS) and amine reactions generate products containing C–N bonds, with rates depending directly on pH: rate = (70 ± 60) M−1 s−1fAld [Glx]totfAm [Am]tot, where fAld is the fraction of aldehyde with a dehydrated aldehyde functional group, and fAm is the fraction of amine or ammonia that is deprotonated at a given pH. MG + amine reactions generate mostly aldol condensation products and exhibit less pH dependence: rate = 10[(0.36 ± 0.06) × pH − (3.6 ± 0.3)] M−1 s−1fAld [MG]tot [Am]tot. Aldehyde + AS reactions are less temperature-dependent (Ea = 18 ± 8 kJ mol−1) than corresponding amine reactions (Ea = 50 ± 11 kJ mol−1). Using aerosol concentrations of [OH] = 10−12 M, [amine]tot = [AS] = 0.1 M, fGlx = 0.046 and fMG = 0.09, we estimate that OH radical reactions are normally the major aerosol-phase sink for both dicarbonyl compounds. However, reactions with AS and amines together can account for up to 12 and 45% of daytime aerosol-phase glyoxal and methylglyoxal reactivity, respectively, in marine aerosol at pH 5.5. Reactions with AS and amines become less important in acidic or non-marine aerosol, but may still be significant atmospheric sources of brown carbon, imidazoles, and nitrogen-containing oligomers.

Experimental study of the thermal conductivity of ammonia + water refrigerant mixtures at temperatures from 278 K to 356 K and at pressures up to 20 MPa

The thermal conductivity of binary ammonia + water mixtures was measured over the temperature range from 278 K to 356 K and at pressures to 20 MPa using the steady-state hot-wire method. Measurements were made for ten compositions over the entire concentration range from 0 to 1 mole fraction of ammonia, namely, 0.0, 0.1905, 0.2683, 0.3002, 0.4990, 0.5030, 0.6704, 0.7832, 0.9178, and 1.0 mole fraction of ammonia. In total, 316 experimental data points were obtained. The expanded uncertainty, with a coverage factor of k = 2, of the thermal conductivity, pressure, temperature, and concentration measurements is estimated to be 3%, 0.05%, 0.02 K, and 0.0014%, respectively. The average absolute deviation (AAD) between the measured and calculated reference values for pure water and ammonia is 1.3% and 1.4%, respectively. Correlation models for the thermal conductivity of liquid ammonia + water mixtures were also developed.

Metabolism of soluble rapeseed meal (Brassica rapa L.) protein during incubations with buffered bovine rumen contents in vitro

Accurate quantitative information on the fate of dietary protein in the rumen is central to modern metabolizable protein systems developed to improve the efficiency of nitrogen utilization in ruminants. An in vitro method was developed to estimate the rate of soluble rapeseed meal (Brassica rapa L.) protein (SRMP) degradation. Unlabeled and 15N-labeled solvent-extracted rapeseed meal were incubated alone or as an equal mixture (125mg of N/L) with buffered rumen contents and a mixture of carbohydrates formulated to provide a constant source of fermentable energy during the course of all incubations. Incubations were made over 0.33, 0.67, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 6.0, 8.0, and 10.0h. Enrichment of 14N and 15N isotopes in total N of ammonia (AN), soluble nonammonia (SNAN), and insoluble (ISN) fractions liberated during incubations with test proteins was determined. A model with 4 pools that accounted for both intracellular and extracellular N transformations was used to estimate the rate of SRMP degradation. Parameter values used in the model were adjusted based on the size of A14N, A15N, SNA14N, SNA15N, IS14N, and IS15N pools, measured at different time points during incubations with buffered rumen fluid. The mean rate of N degradation for SRMP was estimated at 0.126 (SD 0.0499) h−1. No substantive difference in the rate of protein degradation or microbial protein synthesis was observed during incubations of labeled and unlabeled substrates with rumen fluid. In conclusion, combined use of data from incubations of unlabeled and 15N-labeled rapeseed protein with buffered rumen inoculum provided sufficient information to allow for estimation of parameter values in a complex dynamic model of soluble protein degradation. Results indicate the potential of the technique to evaluate the degradability of SNAN of other dietary protein sources and implicate ruminal escape of soluble rapeseed protein as an important source of amino acids in ruminants.

Performance Analysis of the Low-Temperature Solar-Boosted Power Generation System—Part I: Comparison Between Kalina Solar System and Rankine Solar System

On the base of the two classical thermodynamic cycles (Kalina cycle and Rankine cycle), solar-boosted Kalina system (Kalina solar system) and solar-boosted Rankine system (Rankine solar system) with traditional nonconcentrating flat plate solar collector (FPSC) and evacuated tube solar collector (ETSC) are investigated in the present paper. The proposed solar systems are considered to be the hybrid of power generation subcycle and solar collector subcycle. Their electricity generating performances are compared under their respective optimal operating conditions to clarify which one is more competitive in solar utilization. Results show that ETSC is the better choice for the both solar systems. Further, the performance comparison shows that the low-temperature solar energy utilized in Kalina cycle is predominant to generate electricity. Meanwhile, the study also find that mass flow rate of the power generation subcycle, mass flow rate of the solar collector subcycle, mass fraction of ammonia and the regenerator performance are important operational parameters for high performance of the Kalina solar system. Finally, with the aid of the weather conditions of Kumejima Island in Japan, the perceptual knowledge for Kalina solar system by using an application case is shown in the paper.

The Short-term Effects of Temperature and Free Ammonia on Ammonium Oxidization in Granular and Floccular Nitrifying System

The short-term effects of temperature and free ammonia (FA) on ammonium oxidization were investigated in this study by operating several batch tests with two different partial nitrification aggregates, formed as either granules or flocs. The results showed that the rate of ammonium oxidation in both cultures increased significantly as temperature increased from 10 to 30 °C. The specific ammonium oxidation rate with the granules was 2–3 times higher than that with flocs at the same temperature. Nitrification at various FA concentrations and temperatures combination exhibited obvious inhibition in ammonium oxidation rate when FA was 90 mg·L−1 and temperature dropped to 10 °C in the two systems. However, the increase in substrate oxidation rate of ammonia at 30 °C was observed. The results suggested that higher reaction temperature was helpful to reduce the toxicity of FA. Granules appeared to be more tolerant to FA attributed to the much fraction of ammonia oxidizing bacteria (AOB) and higher resistance to the transfer of ammonia into the bacterial aggregates, whereas in the floc system, the bacteria distributed throughout the entire aggregate. These results may contribute to the applicability of the nitrifying granules in wastewater treatment operated at high ammonium concentration.

Oxidation of ammonia on woven and knitted platinoid gauzes

The results from pilot tests of catalytic systems equipped with 7–12 woven or 5–14 knitted platinoid gauzes in the oxidation of ammonia are considered. OAO Yekaterinburg Non-Ferrous Metal Processing Plant produces gauzes of the two types: Pt092 0.092-mm wire woven and Pt076 0.076-mm wire loosely knitted (large-mesh) gauzes. Both types of gauzes are made of PdRdRu 15-3.5-0.5 alloy (referred to as alloy no. 5) and have the following elemental composition: Pt, 81%; Pd, 15%; Rh, 3.5%; Ru, 0.5% (STO (Branch Standard) 00195200-013-2007 and STO (Branch Standard) 00195200-014-2007). The third type is 0.076-mm tightly knitted (small-mesh) gauzes (Uncore, Germany), which differ from the Russian knitted Pt076 gauze by their greater mass and external surface area per unit reactor cross section. The effect of the mass, external surface area, and free volume of woven and knitted platinoid gauzes on the yield of nitrogen oxide is studied in this work, and the residual concentration of ammonia downstream of a stack of gauzes is determined in dependence on their number. The efficiency of the unit surface of knitted gauzes depends on the influence exerted by transfer phenomena and the direct homogeneous ammonia reduction of nitrogen oxide in the free volume of a platinoid catalyst stack. Loosely-knitted Pt076 gauzes are less efficient than woven Pt092 gauzes within a ≥91.5% range of nitrogen oxide yields. Tightly knitted gauzes are suitable for use within a ≤94.5% range of nitrogen oxide yields. Yields equivalent to those obtained on woven gauzes cannot be attained on tightly knitted gauzes even after their external surface area is enlarged considerably. Maximum nitrogen oxide yields (≈95%) are attained on Pt092 woven gauzes. From the results of our tests of loosely and tightly knitted platinoid gauzes, it follows that the latter (with less free volume in a stack) are preferable for use. The free volume of gauzes and the fraction of ammonia for nontargeted conversion can be minimized by placing a smaller number of loosely knitted platinoid gauzes on a regular honeycomb block catalyst or packing bed.

Vapor–liquid equilibrium of ammonia–water–lithium nitrate solutions

AbstractExperimental results on the pressure–temperature data for the NH3‐H2O binary and NH3‐H2O‐LiNO3 ternary solutions are reported. The pressure was varied between 100 and 800 kPa, while the mass fraction of ammonia was varied in the range 0–0.30. The lithium nitrate concentration of the solution was chosen in the range of 10–50% of mass ratio of lithium nitrate in pure water. An analytical equation for the equilibrium pressure as a function of temperature and concentration was obtained with a good fit to experimental data. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.20351

암모니아-물 작동유체의 부분증발유동을 적용한 재생 랭킨사이클에 관한 연구

ABSTRACT:The power cycle using ammonia-water mixture as a working fluid is a possible way to improve efficiency of the system of low-temperature source. In this work thermodynamic performance of the ammonia-water regenerative Rankine cycle with partial-boiling flow is analyzed for purpose of extracting maximum power from the source. Effects of the system parameters such as mass fraction of ammonia, turbine inlet pressure or ratio of partial-boiling flow on the system are parametrically investigated. Results show that the power output increases with the mass fraction of ammonia but has a maximum value with respect to the turbine inlet pressure, and is able to reach 22 kW per unit mass flow rate of source air at 180℃.Keywords:Rankine cycle(랭킨사이클), Regeneration(재생), Partial-boiling(부분증발), Ammonia- water mixture(암모니아-물 혼합물), Maximum specific work(최대비동력) †Corresponding author Tel.: +82-54-478-7292; fax: +82-54-478-7319 E-mail address: khkim@kumoh.ac.kr 기 호 설 명   ：정압비열 [kJ/kgK] ：깁스자유에너지 [kJ/kg] ：비엔탈피 [kJ/kg]

저온 열원 활용을 위한 암모니아-물 재생 랭킨 사이클의 성능 해석

It is a great interest to convert more energy in the heat source into the power and to improve the efficiency of power generating processes. Since the efficiency of power generating processes becomes poorer as the temperature of the source decreases, to use an ammonia-water mixture instead of water as working fluid is a possible way to improve the efficiency of the system. In this work performance of ammonia-water regenerative Rankine cycle is investigated for the purpose of extracting maximum power from low-temperature waste heat in the form of sensible energy. Special attention is paid to the effect of system parameters such as mass fraction of ammonia and turbine inlet pressure on the characteristics of system. Results show that the power output increases with the mass fraction of ammonia in the mixture, however workable range of the mass fraction becomes narrower as turbine inlet pressure increases and is able to reach 16.5kW per unit mass flow rate of source air at .

Experimental investigation on an ammonia–water–lithium bromide absorption refrigeration system without solution pump

Experimental researches were carried out on a novel ammonia–water–lithium bromide ternary solution absorption refrigeration and air-conditioning system without solution pump and distillation equipments. The experiments were conducted by using three kinds of NH 3–H 2O binary solution and 17 kinds of ternary solution with difference in mass fraction of NH 3 and LiBr. The experimental results showed that the vapor pressure of the generator in the system would be lower than that of the generator in an ammonia–water absorption system. In above two situations the same ammonia mass fraction and the same solution temperature were kept. The amplitude of vapor pressure decrease of the system generator would be larger with the increase of the mass fraction of LiBr. The maximum amplitude of decrease would be of 50%. With the increase of the mass fraction of LiBr, the coefficient of performance (COP) of the system would be increased initially, and then decreased later when the mass fraction of LiBr exceeded a certain value. This value was about 23% for the solution with ammonia mass fraction of 50% and 55%, and about 30% for the solution with ammonia mass fraction of 60%. Compared with the ammonia–water system, the COP of the ternary solution system with the same mass fraction of ammonia would increase up to 30%. With the ammonia mass fraction of 60% and LiBr mass fraction of 30% applied, the COP of the ternary solution system was increased up to 0.401. It was 51.89% higher than that when binary ammonia–water solution with ammonia mass fraction of 50% was applied. In above two operating situations, the temperature of hot water, cooling water and chilled water in the system would be kept almost constant, respectively.

The influence of gas-particle partitioning and surface-atmosphere exchange on ammonia during BAQS-Met

Abstract. The Border Air Quality and Meteorology study (BAQS-Met) was an intensive field campaign conducted in Southwestern Ontario during the summer of 2007. The focus of BAQS-Met was determining the causes of the formation of ozone and fine particulate matter (PM2.5), and of the regional significance of trans-boundary transport and lake breeze circulations on that formation. Fast (1 Hz) measurements of ammonia were acquired using a Quantum Cascade Laser Tunable Infrared Differential Absorption Spectrometer (QC-TILDAS) at the Harrow supersite. Measurements of PM2.5 ammonium, sulfate and nitrate were made using an Ambient Ion Monitor Ion Chromatograph (AIM-IC) with hourly time resolution. The median mixing ratio of ammonia was 2.5 ppb, with occasional high spikes at night resulting from local emissions. Measurements were used to assess major local emissions of NH3, diurnal profiles and gas-particle partitioning. The measurements were compared with results from A Unified Regional Air-quality Modelling System (AURAMS). While the fraction of total ammonia (NHx≡NH3 + NH4+) observed in the gas phase peaks between 0.1 and 0.8, AURAMS tended to predict fractions of either less than 0.05 or greater than 0.8. The model frequently predicted acidic aerosol, in contrast with observations wherein NHx almost always exceeded the observed equivalents of sulfate. One explanation for our observations is that the net flux of ammonia from the land surface to the atmosphere increases when aerosol sulfate is present, effectively buffering the mixing ratio of gas phase ammonia, a process not included in the model. A simple representation of an offline bi-directional flux parameterization using the ISORROPIA thermodynamic model was successful at reducing the population of zero gas fraction points, but not the higher gas fraction points.

D116 ウエハラサイクルを用いた発電システムの特性(OS2 再生可能エネルギー(太陽・地熱・温度差))

This paper described a performance analysis of the power system using Uehara cycle utilizing warm wastewater as a heat source. Uehara cycle utilizes ammonia/water mixtures as working fluid. The facters in performance analysis consist of the inlet temperature of warm wastewater, the mass fraction of ammonia and each overall heat transfer coefficient of the heat exchangers. In this analysis, the thermal efficiency of Uehara cycle becames larger when the inlet temperature of warm wastewater is increased. Also, the thermal efficiency of Uehara cycle becames larger when the mass fraction of ammonia is increased because the rate of bleed of the turbine is increased. The thermal efficiency of Uehara cycle is compared with that Carnot cycle.

Experimental Study of Startup Characteristics and Performance of Low-Power Arcjet

A radiation-cooled low-power arcjet thruster is tested in order to study the startup characteristics and performancewith nitrogen and ammoniamixtures as the propellant in a vacuumwith chamber pressures lower than 5 Pa. In the ignition tests, two different starter circuits, i.e., high-frequency and high-voltage pulse ignition techniques, are used to initiate the discharge. The results of the ignition tests show that arc current, electrode temperature, inlet pressure, andmole fraction of ammonia in the propellant have significant effects on arcjet startup characteristics. Experimental studies are also carried out to reveal the effects of different molar mixing ratios of nitrogen/ammoniamixtures on arcjet thruster performance. It is found that the important performance parameters of arcjet such as thrust, specific impulse, and thrust efficiency increase with an increased amount of ammonia in the propellant. The molar mixing ratio of the nitrogen/ammonia mixtures has significant effects on arcjet currentvoltage characteristics.

Experimental study on enhancement of ammonia–water falling film absorption by adding nano-particles

Based on the preparation of Al 2O 3, Fe 2O 3 and ZnFe 2O 4 nanofluid, the comparative experiments on the falling film absorption between ammonia–water and ammonia–water with various kinds of nano-particles are carried out. Experimental results show that the sorts and mass fraction of nano-particles, the viscosity and stability of nanofluid, as well as the mass fraction of ammonia in the basefluid are considered as the key parameters. The absorption of ammonia is weakened by only adding surfactants or adding poorly dispersed nano-particles. The increase of mass fraction of nano-particles with matched surfactants can improve the absorption rate of ammonia under the condition that the viscosity of nanofluid does not increase remarkably, and there is an optimal mass fraction for each kind of nano-particles and surfactant. With the increase in ammonia mass fraction of initial nanofluid, the absorption potential capacity decline, but the enhancing effect induced by the nanofluid is more obvious compared to that without nano-particles. The effective absorption ratio can be increased by 70% and 50% with Fe 2O 3 and ZnFe 2O 4 nanofluid respectively when the initial ammonia mass fraction is 15%. The absorption enhancement by the nanofluid is attributable to the heat transfer enhancement and the decrease in viscosity of nanofluid, which are strongly proved by the temperature differences in cooling water and nanofluids as well as the falling film flowing time.

Enhancement of nucleate pool boiling heat transfer in ammonia/water mixtures (Effect of surface‐active agent)

AbstractNucleate boiling heat transfer coefficients of ammonia/water mixtures have been measured when a surface‐active agent was added into the mixtures. The experiment has been carried out on a horizontal heated wire at a pressure of 0.4 MPa. The effect of concentration of the ammonia and the surface‐active agent on the coefficients was investigated experimentally for the ammonia fractions C = 0.3 and 0.7 and the surfactant concentration CS = 0 to 3500 ppm. The result shows that just after onset of boiling the nucleate boiling heat transfer coefficient enhances at the lower ammonia fraction i.e., C = 0.3. It was found that the enhancement effect by the surface‐active agent disappeared when the surfactant concentration is more than 1000 ppm at an ammonia fraction C = 0.3.It is also shown that the generated heat of mixing near the vaporBliquid interface can be removed easily and the pressure and temperature in the system can be controlled easily by placing a cooling pipe on the vaporBliquid interface, resulting in improvement of accuracy in measuring the heat transfer coefficients. We correlated the effect of the surfactant on the heat transfer coefficient using the improved measurement data in the current paper. 8 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20328