Effects Of Volume Flow Rate Research Articles

Numerical analysis of photothermal conversion performance of MXene nanofluid in direct absorption solar collectors

A newly direct absorption solar collector (DASC) based on MXene nanofluid is proposed herein. The excellent optical properties of MXene nanofluids are experimentally determined, and a three-dimensional steady-state numerical model is developed to investigate the synergistic effect of the optical properties of MXene nanofluids and the structural parameters of the DASC. The effects of volume flow rate, working temperature, and solar concentration ratio on the photothermal conversion performance of the DASC are also analyzed. The results show that the transmittance of the MXene nanofluid evidently decreases because of the enhanced absorption of solar radiation of MXene. With the addition of MXene, the photothermal conversion efficiency of the nanofluid rapidly increases and then slightly decreases. The optimal MXene mass fraction is inversely proportional to the collector height. A mere 100 ppm of MXene nanofluid can achieve a maximum intercept efficiency of 77.49%, which is 55.47% higher than that of the base fluid. This work demonstrates the potential for the application of MXene nanofluids in the utilization of solar energy.

Effect of different nanoparticle-dispersed nanofluids on hydrothermal-economic performance of minichannel heat sink

Hydrothermal and energy-economic performances of minichannel heat sink are experimentally compared by using water-based different nanoparticle-dispersed mono and hybrid nanofluids. Al2O3, AlN, CNT, Cu and capric acid as phase change material (PCM) are considered. Different nanoparticles combinations (oxide–PCM, oxide–nitride, oxide–carbon nanotube and oxide–metal) in 50/50 volume ratio with water (base fluid) are taken as working fluids. The effects of volume flow rate (0.1–0.5 LPM) or Reynolds number (50 to 500) and total particle volume concentration (0.01–0.1%) are investigated. Convective heat transfer coefficient and pressure drop increase by about 42.3% and 22%, respectively, for Al2O3 + CNT nanofluid. The maximum reduction of 26.6% in thermal resistance is obtained for Al2O3 + CNT nanofluid as compared to base fluid. Heat transfer effectiveness and figure of merit are above one for all the hybrid nanofluids, which conclude that hybrid nanofluid is a better option over base fluid for minichannel heat sink. Al2O3 + CNT hybrid nanofluid is better in terms of heat transfer effectiveness, but Al2O3 + AlN hybrid nanofluid yields higher heat transfer coefficient to pressure drop ratio and coefficient of performance. The lower nanoparticle volume concentration in nanofluid is preferable due to higher stability, lower clogging and lower cost per cooling capacity of heat sink.

Experimental hydrothermal characteristics of minichannel heat sink using various types of hybrid nanofluids

The hydrothermal characteristics of minichannel heat sink are analyzed experimentally by using deionized (DI) water based different nanoparticles mixture dispersed hybrid nanofluids. Al2O3, MgO, SiC, AlN, MWCNT and Cu nanoparticles are considered for this study. Different nanoparticles combinations (oxide-oxide, oxide-carbide, oxide-nitride, oxide-carbon nanotube and oxide-metal) in 50/50 vol ratio with base fluid (DI water) have been taken as coolants for volume concentration of 0.01%. Effects of volume flow rate (0.1–0.5LPM), fluid inlet temperature (20–40 °C) and Reynolds number (50–500) are studied for heat flux of 50 W/cm2. Convective heat transfer coefficient and pressure drop are increased by about 42.24% and 22% for Al2O3 + MWCNT hybrid nanofluid. The maximum reduction of 21.36% in thermal resistance is obtained for Al2O3 + MWCNT hybrid nanofluid in comparison to DI water. Heat transfer effectiveness and figure of merit are above one for all the hybrid nanofluids which conclude that hybrid nanofluid is better option for electronics cooling over DI water. Al2O3 + MWCNT hybrid nanofluid is better in terms of heat transfer effectiveness; whereas, Al2O3 + AlN hybrid nanofluid (oxide-nitrite mixture) has maximum heat transfer coefficient to pressure drop ratio and coefficient of performance.

Kinetic Study on Esterification of Acetic Acid with Isopropyl Alcohol Catalyzed by Ion Exchange Resin.

Esterification kinetics on acetic acid with isopropyl alcohol was studied in an intensified fixed bed reactor at 333–353 K with Amberlyst 36 Wet. The effects of volume flow rate, molar ratio of reactants, catalyst loading, and operating temperature were investigated and optimized. The method of UNIFAC was applied to calculate the activity coefficient of each component for correcting the nonideality of the solution. Reaction enthalpy, entropy, and Gibbs free energy were calculated in different cases. The pseudohomogeneous model, Eley–Rideal model, and Langmuir–Hinshelwood–Hougen–Watson model were used to establish kinetic equations of the reaction conducted in the IFBR. It was proved that the LHHW model can accurately describe the esterification kinetics in the intensified fixed bed reactor.

Three-dimensional multiphase flow modeling of membrane humidifier for PEM fuel cell application

Purpose In this paper, a single module of cross-flow membrane humidifier is evaluated as a three-dimensional multiphase model. The purpose of this paper is to analyze the effect of volume flow rate, dry temperature, dew point wet temperature and porosity of gas diffusion layer on the humidifier performance.Design/methodology/approach In this study, one set of coupled equations are continuity, momentum, species and energy conservation is considered. The numerical code is benchmarked by the comparison of numerical results with experimental data of Hwang et al.Findings The results reveal that the transfer rate of water vapor and dew point approach temperature (DPAT) increase by increasing the volume flow rate. Also, it is found that the water recovery ratio (WRR) and relative humidity (RH) decrease with increasing volume flow rate. In addition, all mixed results decrease with increasing dry side temperature especially at high volume flow rates and this trend in high volume flow rates is more sensible. Although the transfer rate of water vapor and DPAT increases with increasing the wet inlet temperature, WRR and RH reduce. Increasing dew point temperature effect is more sensible at the wet side is compared with the dry side. The humidification performance will be enhanced with increasing diffusion layer porosity by increasing the wet inlet dew point temperature, but has no meaningful effect on other operating parameters. The pressure drop along humidifier gas channels increases with rising flow rate, consequently, the required power of membrane humidifier will enhance.Originality/value According to previous studies, the three-dimensional numerical multiphase model of cross-flow membrane humidifier has not been developed.

Performance Study of Water Harvesting Unit Working Under Iraqi Conditions

The scarcity of water facing the world is one of the biggest challenges of this century. This challenge requires research plans in the field of water desalination that is not suitable for human use or the harvesting of water from the air. In this work, the performance of the water harvesting unit from the ambient air is studied. For this purpose, a vapor compression system is designed and built, a 372[Formula: see text]W reciprocating compressor is selected depending on the use of a small family consisting of four persons. The components of the vapor compression system are designed depending on the compressor power. The unit evaporator is modified to condensate the water vapor associated with the air instead of cooling the air. The effect of volume flow rate of air across the evaporator is studied. The range of air volume flow rate is from 224 to 244[Formula: see text]m3/h, as well as the operation mode of the unit which either continues to condensate or freeze the water vapor on the evaporator is also studied. The result showed that the water harvesting unit can work at a relative humidity as low as about 20%. The maximum water production for the unit is 7.9[Formula: see text]l/day with a power consumption of 1.76[Formula: see text]kW-h/l at the volume flow rate of air is 230[Formula: see text]m3/h. When an evaporative cooler is turned on in the test chamber, the amount of water production increases to about 13.11[Formula: see text]l/day with a power consumption of 1.068[Formula: see text]kW-h/l, for the same volume flow rate of air mentioned above.

Experimental Studies of Ethyl Acetate Saponification Using Different Reactor Systems: The Effect of Volume Flow Rate on Reactor Performance and Pressure Drop

Microreactors intensify chemical processes due to improved flow regimes, mass and heat transfer. In the present study, the effect of the volume flow rate on reactor performance in different reactors (the T-shaped reactor, the interdigital microreactor and the chicane microreactor) was investigated. For this purpose, the saponification reaction in these reactor systems was considered. Experimental results were verified using the obtained kinetic model. The reactor system with a T-shaped reactor shows good performance only at high flow rates, while the experimental setups with the interdigital and the chicane microreactors yield good performance throughout the whole range of volume flow rates. However, microreactors exhibit a higher pressure drop, indicating higher mechanical flow energy consumption than seen using a T-shaped reactor.

Numerical and experimental investigations on heat transfer and pressure drop characteristics of Al2O3-TiO2 hybrid nanofluid in minichannel heat sink with different mixture ratio

Heat transfer and pressure drop characteristics of minichannel heat sink are analysed experimentally and numerically (two-phase mixture model) by using hybrid nanofluids. Minichannel heat sink consists of 9 parallel rectangular shaped minichannels having depth of 3 mm and width of 1 mm. The Al2O3–TiO2 hybrid nanofluid with nanoparticles volume concentration of 0.1% with different nanoparticle mixture ratios (10:0 to 0:10) has been used as coolant to analyze the effect of volume flow rate (0.1 to 0.5 LPM), Reynolds number (90 < Re < 500) and inlet temperature (20 to 40 °C). Two-phase mixture model has good agreement with the experiment data as compared to single phase (homogenous model) approach. The developing length slightly increases by using hybrid nanofluid. A maximum enhancement of 8.5% (numerical) and 12.8% (experimental) has been observed for convective heat transfer coefficient with Al2O3 (10:0) hybrid nanofluid. Pressure drop and friction factor increase with decrease in temperature and increase in volume fraction of nanoparticles. Both numerical and experimental results reveal that the hybrid nanofluids yield no synergetic effect in heat transfer while mixing dissimilar nanoparticles with similar shape and size.

Experimental study of heat transfer enhancement due to the surface vibrations in a flexible double pipe heat exchanger

In this study, the heat transfer enhancement due to the surface vibration for a double pipe heat exchanger, made of PVDF, is investigated. In order to create forced vibrations (3–9 m/s2, 100 Hz) on the outer surface of the heat exchanger electro-dynamic vibrators are used. Experiments were performed at inner Reynolds numbers ranging from 2533 to 9960. The effects of volume flow rate and temperature on heat transfer performance are evaluated. Results demonstrated that heat transfer coefficient increases by increasing vibration level and mass flow rate. The most increase in heat transfer coefficient is 97% which is obtained for the highest vibration level (9 m/s2) in the experiment range.

Optimum design of triangular shaped micro mixer in micro channel heat sink

The focus of the present study is on the effect of triangular shaped micro mixers placed between the main stream channels in micro channel heat sink (MCHS). These micro mixers are constructed based on three parameters (inner and outer angle and depth of the joining point) and positioned periodically at an assigned distance. A single unit wall with separated channels is selected from the simple MCHS and micro channel with a triangular shaped micro mixer (MTM) as the computational domain for the numerical simulation. The performance of both micro channels are compared at identical boundary conditions. The effect of volume flow rate of the fluid, flow direction, position of the micro mixer (parallel or alternating), and geometrical parameters of micro mixer on the flow and heat transfer performance of MTM is studied. It is found that the performance of MTM is greatly dependent on the variation of all geometrical parameters. It has to be also highlighted that overall enhancement factor of MTM improved up to 1.53 times compared to simple MCHS with slight reduction in friction factor. This binary benefit of MTM makes it highly possible to be implemented in the practical application.

Numerical study of nonisothermal polymer extrusion flow with a differential viscoelastic model

AbstractA numerical study of nonisothermal viscoelastic flow is conducted to investigate the complex flow characteristics of polymer melts in the extrusion process. A general thermodynamic model for the energy conversion related to viscoelastic fluid flow is introduced. The mathematical model for three‐dimensional nonisothermal viscoelastic flow of the polymer melts obeying a differential constitutive equation (Phan‐Thien and Tanner model) is established. A decoupled algorithm based on the penalty finite element method is performed on the calculation. The discrete elastic‐viscous split stress (DEVSS) algorithm, incorporating the streamline‐upwind Petrov‐Galerkin (SUPG) scheme is employed to improve the computation stability. Essential flow characteristics of polymer melts in the extrusion die for hollow square plastic profile is investigated based on the proposed numerical scheme with ignoring the outer thermal resource. The energy partitioning, which quantified the conversion of mechanical energy into thermal energy, is discussed. The effects of volume flow rate and die contraction angle upon the flow patterns are further investigated. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers