Pressure Drop Of Nanofluid Research Articles

Performance Evaluation of AI2O3/Water Nanofluid as Coolant in a Double-Tube Heat Exchanger Flowing under a Turbulent Flow Regime

Nanofluids are expected to be a promising coolant candidate in chemical processes for water waste remediation and heat transfer system size reduction. This paper focuses on the potential mass flowrate reduction in exchanger with a given heat exchange capacity using nanofluids. Al2O3 nanoparticles with diameters of 7 nm dispersed in water with volume concentrations up to 2% are selected as a coolant, and their performance in a horizontal double-tube counterflow heat exchanger under turbulent flow conditions is numerically studied. The results show that the flowrate of nanofluid coolant decreases with the increase of concentration of nanoparticles in the exchanger with a given heat exchange capacity. The mass flowrate of the nanofluid at a volume concentration of 2 vol.% is approximately 24.5% lower than that of pure water (base fluid) for given conditions. For the pressure drop, the results show that the pressure drop of nanofluid is slightly higher than water and increases with increase of volume concentrations. In addition, the reduction of wall temperature and heat transfer area is estimated.

Experimental studies on heat transfer and friction factor characteristics of Al<SUB align="right">2O<SUB align="right">3/water nanofluid under laminar flow with spiralled rod inserts

An experimental investigation on the convective heat transfer and friction factor characteristics in the plain and spiralled rod inserts (pitch = 15 mm, 30 mm) in a plain tube under laminar flow with constant heat flux is carried out with Al2O3-water nanofluids. We study the effect of the inclusion of nanoparticles on heat transfer enhancement, thermal conductivity, viscosity, and pressure loss in the laminar flow region. For this, we synthesised Al2O3 nanoparticles by using microwave assisted chemical precipitation method and we measured size of nanoparticles by using XRD. The average size of particle is 40.3 nm, and then the nanoparticles dispersed in distilled water to form stable suspension containing 0.3%, 0.4%, 0.5% volume concentration of nanoparticles. The experimental results of Nusselt number for 0.5% nanofluid with spiralled rod inserts under laminar flow showed a maximum of 24% higher than the plain tube and the isothermal pressure drop of nanofluids with spiralled rod inserts were about 5% to 15% higher than the plain tube.

Analysis of flow and heat transfer characteristics of micro-pin fin heat sink using silver nanofluids

Silver nanofluids with three different volume fractions are prepared by a one-step chemical reduction method (Ultrasound-assisted Membrane Reaction (UAMR)). The convective heat transfer and friction characteristics of silver nanofluid in micro-pin fin heat sink are investigated experimentally. The results indicate that the pressure drops of nanofluids with different volume fractions have little difference. Compared to the base fluid (polyvinylpyrrolidone (PVP) solution), the pressure drop of nanofluids increases slightly at the same volume flow rate. When the flow rate is small, the increment is not obvious. The introduction of surfactant increases the fluid viscosity, so the pressure drops of nanofluids are larger than those of pure water, under the same flow rate. However, the maximum difference is no more than 10%. The volume fraction of silver nanoparticles significantly affects the convection heat transfer coefficient of micro-pin fin heat sink. The presence of nanoparticles improves significantly the heat transfer performance. However, high viscosity of the nanofluids hinders the heat transfer strengthening effect of nanofluids. In the present work, when the volume fraction of silver particles reaches to 0.012%, the thermal resistance of nanofluid gradually becomes lower than that of deionized water, which indicates the integrated heat transfer enhancement of nanofluids.

Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration.

Investigation of turbulent convective heat transfer and pressure drop of TiO 2/water nanofluid in circular tube

Turbulent heat transfer behavior of titanium dioxide/water nanofluid in a circular pipe was investigated experimentally where the volume fraction of nanoparticles in the base fluid was less than 0.25%. The experimental measurements have been carried out in the fully-developed turbulent regime for various volumetric concentrations. The results indicated that addition of small amounts of nanoparticles to the base fluid augmented heat transfer remarkably. There was no much effect on heat transfer enhancement with increasing the volume fraction of nanoparticles. The measurements also showed that the pressure drop of nanofluid was slightly higher than that of the base fluid and increased with increasing the volume concentration. In this paper, experimental results have been compared with the existing correlations for nanofluid convective heat transfer coefficient in turbulent regime. Finally, a new correlation of the Nusselt number will be presented using the results of the experiments with titanium dioxide nanoparticles dispersed in water.

Numerical investigation of effective parameters in convective heat transfer of nanofluids flowing under a laminar flow regime

This article presents a numerical investigation on heat transfer performance and pressure drop of nanofluids flows through a straight circular pipe in a laminar flow regime and constant heat flux boundary condition. Al 2O 3, CuO, carbon nanotube (CNT) and titanate nanotube (TNT) nanoparticles dispersed in water and ethylene glycol/water with particle concentrations ranging between 0 and 6 vol.% were used as working fluids for simulating the heat transfer and flow behaviours of nanofluids. The proposed model has been validated with the available experimental data and correlations. The effects of particle concentrations, particle diameter, particles Brownian motions, Reynolds number, type of the nanoparticles and base fluid on the heat transfer coefficient and pressure drop of nanofluids were determined and discussed in details. The results indicated that the particle volume concentration, Brownian motion and aspect ratio of nanoparticles similar to flow Reynolds number increase the heat transfer coefficient, while the nanoparticle diameter has an opposite effect on the heat transfer coefficient. Finally, the present study provides some considerations for the appropriate choice of the nanofluids for practical applications.

나노입자 형상 변화에 따른 알루미나 나노유체의 유동 특성

본 연구에서는 다양한 형상의 나노입자를 분산시킨 알루미나 나노유체의 유동 특성을 실험적으로 조사하기 위하여 나노입자의 형상 변화에 따른 알루미나 나노유체의 압력강하를 층류영역에서 측정하였다. 이를 위해 Sphere, Rod, Platelet, 그리고 Brick 의 형태를 갖는 알루미나 나노입자를 물에 분산시켜 부피비 0.3%를 갖도록 Two-step 방법으로 제작하였다. 제작된 나노유체의 분산성을 파악하기 위하여 제타포텐셜을 조사하였으며, 나노입자의 형상을 파악하기 위하여 TEM 사진을 측정하였다. 다양한 형상의 나노입자를 분산시켜 0.3%의 부피비를 갖는 나노유체의 압력강하를 측정하였을 때, 입자형상이 나노유체의 유동특성에 영향을 미치는 것을 확인하였다. 실험 결과를 바탕으로 나노입자의 단위질량당 표면적과 분산된 나노입자의 크기를 이용하여 나노유체의 압력강하 특성을 설명하였다.

Local convective boiling heat transfer and pressure drop of nanofluid in narrow rectangular channels

Abstract This paper reports an experimental study on convective boiling heat transfer of nanofluids and de-ionized water flowing in a multichannel. The test copper plate contains 50 parallel rectangular minichannels of hydraulic diameter 800 μm. Experiments were performed to characterize the local heat transfer coefficients and surface temperature using copper–water nanofluids with very small nanoparticles concentration. Axial distribution of local heat transfer is estimated using a non-intrusive method. Only responses of thermocouples located inside the wall are used to solve inverse heat conduction problem. It is shown that the distribution of the local heat flux, surface temperature, and local heat transfer coefficient is dependent on the axial location and nanoparticles concentration. The local heat transfer coefficients estimated inversely are close to those determined from the correlation of Kandlikar and Balasubramanian [An extension of the flow boiling correlation to transition, laminar and deep laminar flows in minichannels and microchannels, Heat Transfer Eng. 25 (3) (2004) 86–93.] for boiling water. It is shown that the local heat flux, local vapor quality, and local heat transfer coefficient increase with copper nanoparticles concentration. The surface temperature is high for de-ionized water and it decreases with copper nanoparticles concentration.

An experimental study on the heat transfer performance and pressure drop of TiO 2-water nanofluids flowing under a turbulent flow regime

Nanofluid is a new class of heat transfer fluids engineered by dispersing metallic or non-metallic nanoparticles with a typical size of less than 100 nm in the conventional heat transfer fluids. Their use remarkably augments the heat transfer potential of the base liquids. This article presents the heat transfer coefficient and friction factor of the TiO 2-water nanofluids flowing in a horizontal double tube counter-flow heat exchanger under turbulent flow conditions, experimentally. TiO 2 nanoparticles with diameters of 21 nm dispersed in water with volume concentrations of 0.2–2 vol.% are used as the test fluid. The results show that the heat transfer coefficient of nanofluid is higher than that of the base liquid and increased with increasing the Reynolds number and particle concentrations. The heat transfer coefficient of nanofluids was approximately 26% greater than that of pure vol.%, and the results also show that the heat transfer coefficient of the nanofluids at a volume concentration of 2.0 vol.% was approximately 14% lower than that of base fluids for given conditions. For the pressure drop, the results show that the pressure drop of nanofluids was slightly higher than the base fluid and increases with increasing the volume concentrations. Finally, the new correlations were proposed for predicting the Nusselt number and friction factor of the nanofluids, especially.

An experimental study on the pressure drop of nanofluids containing carbon nanotubes in a horizontal tube

This article reports an experimental study on the flow characteristics of the aqueous suspensions of carbon nanotubes (CNTs). Stable nanotube suspensions were made for pressure drop measurements by two different methods. One of them is to disperse nanotubes using a surfactant, and the other is to introduce oxygen-containing functional groups on the CNT surfaces by acid treatment. The pressure drops in a horizontal tube and viscosities of nanofluids were measured and the effects of CNT loading and different preparation methods were investigated. Viscosity measurements show that both CNT nanofluids prepared by two methods are shear thinning fluids and at the same volume fraction, the nanofluids prepared by the acid treatment have much smaller viscosity than the ones made with surfactant. Under laminar flow conditions, the friction factor of CNT nanofluids stabilized by adding surfactant is much larger than that of CNT nanofluids prepared by acid treatment, and both nanofluids show larger friction factors than distilled water. In contrast to this, under turbulent flow conditions, the friction factors of both nanofluids become similar to that of the base fluids as the flow rate increases. It is also shown that as CNT loading is increased, laminar regime of nanofluids has been extended to further higher flow rates, therefore, nanofluids could have low friction factors than pure water flows at certain range of flow rates.