Effect of Channel Geometry Variations on the Performance of a Constrained Microscale-Film Ammonia-Water Bubble Absorber

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Jeromy Jenks ◽  
Vinod Narayanan
Keyword(s):  
Weak Solution ◽  
Gas Flow ◽  
Water Solution ◽  
Flow Rate Ratio ◽  
Solution Flow Rate ◽  
Inlet Temperature ◽  
Ammonia Vapor ◽  
Solution Flow ◽  
Flow Rates ◽  
Ammonia Water

An experimental study of the absorption of ammonia vapor in a constrained thin film of ammonia-water solution is presented. A large aspect ratio microchannel with one of its walls formed of a porous material is used to constrain the thickness of the liquid film. Experiments are performed at a pressure of 2.5 bar absolute and 4 bar absolute and at a fixed weak solution inlet temperature. Weak solution flow rates are varied from 10 g/min to 30 g/min (corresponding to the weak solution Reynolds number, Re, from 15 to 45), inlet mass concentrations are varied from 0% to 15%, and gas flow rates are varied between 1 g/min and 3 g/min (corresponding to the vapor Re from 160 to 520). Six geometries, including three smooth-bottom-walled channels of differing depths and three channels with structured bottom walls, are considered. Results indicate that, for identical rates of vapor absorption, the overall heat transfer coefficient of the 400 μm absorber is in most cases significantly larger than that of other absorbers. For the 150 μm and 400 μm absorbers, a trade-off between the high overall heat and mass transfer coefficients is achieved for the highest vapor to solution flow rate ratio.

An Experimental Study of Ammonia-Water Bubble Absorption in a Large Aspect Ratio Microchannel

2006 ◽  
Author(s):  
Jeromy Jenks ◽  
Vinod Narayanan
Keyword(s):  
Experimental Study ◽  
Weak Solution ◽  
Aspect Ratio ◽  
Gas Flow ◽  
Water Solution ◽  
Inlet Temperature ◽  
Large Aspect Ratio ◽  
Solution Flow ◽  
Flow Rates ◽  
Ammonia Water

An experimental study of absorption of ammonia into a constrained thin film of ammonia-water solution is presented. A large aspect ratio microchannel with one of its walls formed by a porous material is used to constrain the thickness of the liquid film. An exit visualization section was used to confirm absorption of ammonia gas within the microchannel. Experiments were performed at a pressure of 1 bar and a fixed inlet temperature of the weak solution, for weak solution flow rates from 10 to 30 g/min, inlet mass concentrations from 0 to 15 percent, and gas flow rates between 1 and 3 g/min. Results indicate that the overall heat transfer coefficient changes little for lower inlet weak solution concentrations and for lower gas flow rates, but increases noticeably for a higher solution and gas flow rate. The solution side log-mean temperature distribution increases with an increase in inlet solution concentration. Absorber exit visualization revealed the presence of periodic ammonia bubbles, occurring in varying sizes and periods, indicating that improvements to the current design are necessary to ensure complete absorption within the microchannel.

A Numerical Study of Ammonia-Water Absorption Into a Constrained Microscale Film

2008 ◽  
Author(s):  
Ruander Cardenas ◽  
Vinod Narayanan
Keyword(s):  
Weak Solution ◽  
Steady State ◽  
Parametric Study ◽  
Numerical Study ◽  
Porous Plate ◽  
Coolant Fluid ◽  
Geometrical Parameters ◽  
Ammonia Vapor ◽  
Ammonia Water ◽  
Vapor Distribution

A one-dimensional, steady state, semi-empirical model of an ammonia-water microscale bubble absorber is presented. The geometry consists of a microchannel through which a solution of ammonia-water flows. Ammonia vapor is injected through one of the walls of the channel. A counter flowing coolant solution removes the heat generated due to absorption from the opposite wall. The 1-D, steady state species and energy transport equations are solved to yield, along the length of the channel, concentration and temperature profiles of the solution stream and the temperature profile of the coolant fluid stream. Values for the overall heat transfer coefficient from experimental results are used in this model. A parametric study of fluid and geometrical parameters based on the model is presented. The varied fluidic parameters include the mass flow rates of the weak solution, coolant, and vapor, the inlet coolant temperature, and the weak solution concentration. Two variations of the vapor distribution that resulted from a geometrical variation of the porous plate are considered: (a) variation in length of the non-porous section, and (b) variation in the number of intermittent sections in which there was no injection of vapor. Trends of the parametric study were consistent with those of experiments. A salient result of the parametric study indicates that incomplete absorption occurs with an increase in weak solution flow rate due to the decrease in residence time within the microchannel for absorption. At a specific fixed flow condition, a single porous section followed by a non-porous section provides the optimal vapor distribution for absorption within the channel. The length of this non-porous section for optimal absorption within the channel is also determined using the model.

Experimental and Analytical Investigation of Ammonia Absorption into Ammonia-Water Solution: Estimated Interface Concentration

2010 ◽  
Vol 297-301 ◽  
pp. 785-789
Author(s):  
Hatem Mustafa
Keyword(s):  
Pressure Difference ◽  
Water Solution ◽  
Water System ◽  
Initial Pressure ◽  
Test Cell ◽  
Major Influence ◽  
Ammonia Vapor ◽  
Ammonia Water ◽  
Interface Concentration ◽  
Ammonia Absorption

Ammonia absorption process of ammonia vapor into ammonia water solution has been investigated experimentally, by inserting superheated ammonia vapor into a test cell containing a stagnant pool of ammonia water solution of several ammonia mass fractions, Ci. Before commencing the experiment, the pressure in the test cell corresponds to the equilibrium vapor of the ammonia-water system at room temperature. When the valve is opened, mechanical equilibrium is established quickly and the ammonia vapor diffuses into ammonia solution [1]. The difference between the initial pressure in the vapor cylinder and the initial pressure in the test cell ΔPi is found to have a major influence not only on the absorption rate but also on the estimated interface concentration. The interface concentration Cint of the cases ΔPi = 50 and 100 kPa exhibits a similar tendency, Cint decreases rapidly compared to other initial pressures ΔPi = 150 and 200 kPa. On the other hand, the interface concentration Cint of the cases ΔPi = 250 and 300 kPa are increasing within about 50 sec, then are hardly changing with time. They behave almost in a similar way as of Cint = 0.27 kg/kg. A correlation which gives the total absorbed mass of ammonia as a function of the initial concentration, the initial pressure difference and time is derived. In addition, the absorbed mass at no pressure difference could be estimated from the absorbed mass at initial pressure difference.

scholarly journals Effect of Nutrient Solution Flow Rate on Hydroponic Plant Growth and Root Morphology

Plants ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1840 ◽  
Author(s):  
Bateer Baiyin ◽  
Kotaro Tagawa ◽  
Mina Yamada ◽  
Xinyan Wang ◽  
Satoshi Yamada ◽  
...  
Keyword(s):  
Plant Growth ◽  
Root Growth ◽  
Surface Area ◽  
Flow Rate ◽  
Root Morphology ◽  
Root Surface ◽  
Solution Flow Rate ◽  
Root Surface Area ◽  
Solution Flow ◽  
Flow Rates

Crop production under hydroponic environments has many advantages, yet the effects of solution flow rate on plant growth remain unclear. We conducted a hydroponic cultivation study using different flow rates under light-emitting diode lighting to investigate plant growth, nutrient uptake, and root morphology under different flow rates. Swiss chard plants were grown hydroponically under four nutrient solution flow rates (2 L/min, 4 L/min, 6 L/min, and 8 L/min). After 21 days, harvested plants were analyzed for root and shoot fresh weight, root and shoot dry weight, root morphology, and root cellulose and hemicellulose content. We found that suitable flow rates, acting as a eustress, gave the roots appropriate mechanical stimulation to promote root growth, absorb more nutrients, and increase overall plant growth. Conversely, excess flow rates acted as a distress that caused the roots to become compact and inhibited root surface area and root growth. Excess flow rate thereby resulted in a lower root surface area that translated to reduced nutrient ion absorption and poorer plant growth compared with plans cultured under a suitable flow rate. Our results indicate that regulating flow rate can regulate plant thigmomorphogenesis and nutrient uptake, ultimately affecting hydroponic crop quality.

Mass Transfer Rate Enhancement in Sparged Vessel for Ammonia-Water Nano-Fluid in VARS by Adding Nanoparticles

2020 ◽  
Author(s):  
Rahul Bhujbal ◽  
Sanjay Nakate ◽  
Sunil V. Dingare
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Solution Flow Rate ◽  
Low Grade ◽  
Efficient Design ◽  
Operation Condition ◽  
Solution Flow ◽  
Ammonia Water

Abstract The refrigeration systems are used in domestic and commercial freezing applications. These systems are needed to be used energy efficiently to get the economic operation condition. The vapor compression refrigeration cycle (VCR) is getting replaced by vapor absorption refrigeration system (VARS) as they can use low grade energy. This VARS can be used by making use of waste energy in the form of heat which is readily available for many applications. Performance of the VARS is dependent on the generator and absorber performance. In absorber it is based on the amount of refrigerant absorbed and the solution flow rate. Experimental and Numerical study of bubble absorber and effect of nanoparticle on ammonia water mass transfer is carried out. In this study, different designs for the absorber chamber are viewed and compared together, based on the research did earlier. Looking at the aspects of bubble type absorber designs, these designs give better mass transfer performance as compared to other designs. These designs may be improved to get the energy efficient design of the absorber. Present study includes the enhancement of mass transfer rate by the addition of nanoparticles using aluminum oxide (Al2O3). Here, sparged vessels with NH3-H2O binary fluid are arranged with varying percentage of nanoparticle (Al2O3). This study includes the study of mass transfer enhancements by using nanoparticles. Based on the experimental results carried out for the varying mass flow rates it is found that the mass transfer rate is enhanced significantly, it is because the interfacial area is enhanced by the addition of nanoparticles to the base fluids.

The Effect of Processing Parameters Onpoly (Lactic Acid)/Poly(Ethylene Oxide)Bicomponentultrafine Fibersby Co-Electrospinning

2013 ◽  
Vol 701 ◽  
pp. 254-258 ◽  
Author(s):  
Suttipan Pavasupree ◽  
Kawee Srikulkit ◽  
Ratthapol Rangkupan
Keyword(s):  
Lactic Acid ◽  
Flow Rate ◽  
Applied Voltage ◽  
Water Soluble ◽  
Flow Rate Ratio ◽  
Poly Lactic Acid ◽  
Solution Flow Rate ◽  
Electrospinning Technique ◽  
Solution Flow ◽  
Water Soluble Polymer

Poly (lactic acid) (PLA)/polyethylene oxide (PEO) bicomponent fibers werefabricated by co-electrospinning technique in a side by side configuration. Effect of PEO concentration, PLA and PEO solution flow rate and an applied voltage on formation, size and morphology of the fibers were investigated. The results showed that the fibers size increased with increasing PEO concentration, PEO flow rate ratio and applied voltage. The composition of the fibers was confirmed by IR spectrum. Additionally, by pairing PEO, which is a water soluble polymer, with PLA, follow by PEO phase removal in water, a C-shaped ultrafine fiber was prepared.

Ammonia-Water Low-Temperature Thermal Storage System

1998 ◽  
Vol 120 (1) ◽  
pp. 25-31 ◽  
Author(s):  
J. J. Rizza
Keyword(s):  
Low Temperature ◽  
Heat Pump ◽  
Water Solution ◽  
Storage System ◽  
Water Concentration ◽  
Thermal Storage ◽  
Ammonia Vapor ◽  
Peak Period ◽  
Ammonia Water ◽  
Absorption Refrigeration System

An analysis of a low-temperature thermal storage system using an ammonia-water solution both as a refrigerant and as a low-temperature thermal storage material is considered. The thermal storage is useable at a temperature of −27°C and higher. The proposed system is designed to shift electric demand from high to low-demand periods. The system utilizes a heat-operated absorption refrigeration system; however, the generator heat is supplied by a self-contained vapor compression heat pump. The heat pump is operated during the off-peak period to recover the low-temperature thermal storage by reprocessing the stored ammonia-water solution to a lower ammonia-water concentration. The ammonia vapor liberated from solution in the dephlegmator is used in the compressor to produce the generator heat. Three different configurations are considered, including a solar-assisted system. The results are compared to an eutectic salt storage system.

Absorption Characteristics of Multilayered Thin Lithium Bromide (LiBr) Solution Film

2015 ◽  
Author(s):  
Mehdi Mortazavi ◽  
Rasool Nasr Isfahani ◽  
Sajjad Bigham ◽  
Saeed Moghaddam
Keyword(s):  
Absorption Rate ◽  
Numerical Models ◽  
Water Vapor Pressure ◽  
Lithium Bromide ◽  
Cooling Water ◽  
Solution Flow Rate ◽  
Inlet Temperature ◽  
Pressure Potential ◽  
Solution Flow ◽  
Uniform Solution

In this study, an alternative absorber design suitable for the plate-and-frame absorber configuration is introduced. The design utilizes a fin structure installed on a vertical flat plate to produce a uniform solution film and minimize its thickness and to continuously interrupt the boundary layer. Using numerical models supported by experiments employing dye visualization, the suitable fin spacing and size and wettability are determined. The solution flow thickness is measured using the laser confocal displacement measurement technique. The new surface structure is tested in an experimental absorption system. An absorption rate as high as 6×10−3 kg/m2s at a driving pressure potential of 700 Pa is achieved, which is considerably high in comparison with conventional absorption systems. The effect of water vapor pressure, solution flow rate, solution inlet concentration, cooling water inlet temperature and solution inlet temperature on the absorption rate is also investigated. The proposed design provides a potential framework for development of highly compact absorption refrigeration systems.

scholarly journals Effect of substrate temperature and precursor ratio on properties of thin ZnS films sprayed by improved method

2014 ◽  
Vol 32 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Rangnath Zaware ◽  
Bhiva Wagh
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Substrate Temperature ◽  
Flow Rate ◽  
Gas Flow ◽  
Impurity Content ◽  
Solution Flow Rate ◽  
Solution Flow ◽  
Precursor Ratio ◽  
Zns Films

AbstractZinc sulphide (ZnS) thin films were prepared by improved spray pyrolysis (ISP) method. The ISP parameters, such as carrier gas flow rate, solution flow rate and substrate temperature, were controlled with an accuracy of ±0.25 lpm, ±1 ml/h and ±1 °C, respectively. The solution was sprayed in a pulsed mode. The substrate temperature was optimized by analyzing substrate temperature dependent properties of thin films. The thin film deposited at a temperature of 450 °C was dense and fairly smooth with satisfactory crystallinity and very small impurity content. The effect of precursor ratio in the solution on structural, compositional and optical properties of thin ZnS films, deposited at a temperature of 450 °C, was studied. A gradual increase in band gap energy from 3.524 eV to 3.634 eV, refractive index from 2.5 to 2.9 and dielectric constant from 6.6 to 8.7 were observed with the variation of solution precursor (Zn:S) ratio from (1:2) to (1:6). The structural and compositional studies support this kind of enhancement in optical properties. The results show that the thin ZnS film prepared by ISP at the substrate temperature of 450 °C from a solution with specific precursor ratio can be used for optoelectronic and photovoltaic applications.

Fabrication and Characterization of Zinc Oxide-Based Electrospun Nanofibers for Mechanical Energy Harvesting

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Suyitno Suyitno ◽  
Agus Purwanto ◽  
R. Lullus Lambang G. Hidayat ◽  
Imam Sholahudin ◽  
Mirza Yusuf ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Fiber Diameter ◽  
Mechanical Energy ◽  
Electrospun Nanofibers ◽  
Solution Flow Rate ◽  
Maximum Power Density ◽  
Solution Flow ◽  
Flow Rates ◽  
Fabrication And Characterization

Doped and undoped zinc oxide fibers were fabricated by electrospinning at various solution flow rates of 2, 4, and 6 μl/min followed by sintering at 550 °C. The nanogenerators (NGs) fabricated from the fibers were examined for their performance by applying loads (0.25–1.5 kg) representing fingers taps on the keyboard. A higher solution flow rate resulted in a larger fiber diameter, thus reducing nanogenerator voltage. The maximum power density for undoped zinc oxide-based and doped zinc oxide-based nanogenerators was 17.6 and 51.7 nW/cm2, respectively, under a load of 1.25 kg. Enhancing nanogenerator stability is a topic that should be investigated further.

Sign in / Sign up

Export Citation Format

Share Document