Thermal Effects on Micro-Sized Tesla Valves

2014 ◽  
Author(s):  
Basil J. Paudel ◽  
Tausif Jamal ◽  
Scott M. Thompson ◽  
D. Keith Walters
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
High Performance ◽  
Check Valve ◽  
Channel Cross Section ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Working Fluids ◽  
In Series ◽  
Tesla Valve

The Tesla valve is a no-moving-parts check valve that may be used in a variety of mini- or micro-fluidic applications for passive flow promotion and/or rectification. Its effectiveness is measured via its diodicity which depends on the Reynolds number and its unique design features. The valve may be aligned in-series to further increase its fluidic diode effect — forming a multi-staged Tesla valve (MSTV). Using Computational Fluid Dynamics (CFD) and high performance computing, the current investigation assesses the effects of heat transfer on the overall MSTV diodicity and the extent to which the MSTV enhances heat transfer. For laminar, single-phase flow, thermal boundary conditions were imposed to include an isothermal MSTV wall at 20 °C and a flow inlet temperature of either: 20 °C, 50 °C or 80 °C. The flow outlet temperature and MSTV diodicity was then determined for the various inlet temperatures, Reynolds numbers, working fluids (i.e. Prandtl number, Pr) and number of Tesla valves in MSTV. Working fluids were varied between: air (Pr ∼ 0.7), water (Pr ∼ 5) and ethylene glycol (Pr ∼ 200). The MSTV channel cross-section was set to 1 mm2 and the valve-to-valve distance was held constant while varying the number of Tesla valves. Results indicate that there is a significant decrease in diodicity for water and ethylene glycol as the inlet temperature increases, suggesting higher performance of the MSTV when there is less heat transfer. For air, MSTV performance was found to actually increase with temperature. Due to mixing effects, the MSTV was demonstrated to function as an efficient heat exchanger relative to an un-valved mini-channel of similar size.

Numerical Investigation of Multistaged Tesla Valves

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
S. M. Thompson ◽  
B. J. Paudel ◽  
T. Jamal ◽  
D. K. Walters
Keyword(s):  
Reynolds Number ◽  
High Performance ◽  
Three Dimensional ◽  
Check Valve ◽  
Reynolds Numbers ◽  
Fitting Procedures ◽  
In Series ◽  
Computational Fluid Dynamics Cfd ◽  
Using Data ◽  
Tesla Valve

The Tesla valve is a passive-type check valve used for flow control in micro- or minichannel systems for a variety of applications. Although the design and effectiveness of a singular Tesla valve is somewhat well understood, the effects of using multiple, identically shaped Tesla valves in series—forming a multistaged Tesla valve (MSTV)—have not been well documented in the open literature. Therefore, using high-performance computing (HPC) and three-dimensional (3D) computational fluid dynamics (CFD), the effectiveness of an MSTV using Tesla valves with preoptimized designs was quantified in terms of diodicity for laminar flow conditions. The number of Tesla valves/stages (up to 20), valve-to-valve distance (up to 3.375 hydraulic diameters), and Reynolds number (up to 200) was varied to determine their effect on MSTV diodicity. Results clearly indicate that the MSTV provides for a significantly higher diodicity than a single Tesla valve and that this difference increases with Reynolds number. Minimizing the distance between adjacent Tesla valves can significantly increase the MSTV diodicity, however, for very low Reynolds number (Re < 50), the MSTV diodicity is almost independent of valve-to-valve distance and number of valves used. In general, more Tesla valves are required to maximize the MSTV diodicity as the Reynolds number increases. Using data-fitting procedures, a correlation for predicting the MSTV diodicity was developed and shown to be in a power-law form. It is further concluded that 3D CFD more accurately simulates the flow within the Tesla valve over a wider range of Reynolds numbers than 2D simulations that are more commonly reported in the literature. This is supported by demonstrating secondary flow patterns in the Tesla valve outlet that become stronger as Reynolds number increases. Plots of the pressure and velocity fields in various MSTVs are provided to fully document the complex physics of the flow field.

Heat Transfer to Supercritical Water in Vertical Annular Channel and 3-Rod Bundle

2009 ◽  
Author(s):  
V. G. Razumovskiy ◽  
Eu. N. Pis’mennyy ◽  
A. Eu. Koloskov ◽  
I. L. Pioro
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Supercritical Water ◽  
Annular Channel ◽  
Heat Fluxes ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Rod Bundle ◽  
Temperature Regimes ◽  
Outside Diameter

The results of heat transfer to supercritical water flowing upward in a vertical annular channel (1-rod channel) and tight 3-rod bundle consisting of the tubes of 5.2-mm outside diameter and 485-mm heated length are presented. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within the range from 800 to 3000 kg/m2·s, inlet temperature from 125 to 352°C, outlet temperature up to 372°C and heat flux up to 4.6 MW/m2 (heat flux rate up to 2.5 kJ/kg). Temperature regimes of the annular channel and 3-rod bundle were stable and easily reproducible within the whole range of the mass and heat fluxes, even when a deteriorated heat transfer took place. The data resulted from the study could be applicable for a reference estimation of heat transfer in future designs of fuel bundles.

scholarly journals Heat transfer studies in compact heat exchanger using ZnO and TiO2 nanofluids in ethylene glycol/water

2018 ◽  
Vol 24 (4) ◽  
pp. 309-318
Author(s):  
Srinivasan Manikandan ◽  
Rajoo Baskar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Ethylene Glycol ◽  
Volume Fraction ◽  
Inlet Temperature ◽  
Percentage Increase ◽  
Cold Side ◽  
Volume Fractions ◽  
Experimental Values ◽  
Tio2 Nanofluids

This paper reports an experimental study on the heat transfer characteristics of a nanofluid consisting of ZnO/water/ethylene glycol (EG) and TiO2/water/ /ethylene glycol. In this study, the base fluids of ethylene glycol (EG):water (W) with volume fractions of 30:70, 40:60, and 50:50 were prepared, and 0.2 to 1.0 volume fractions of ZnO and TiO2 nanofluids were used as a cold side fluid. The prime objective of this study is to identify the effects of nanofluid concentration and three different hot fluid inlet temperatures viz., 55, 65 and 75?C C on the heat transfer enhancement of cold side fluid. The results are compared with base fluids and the percentage increase of the Nusselt number because of nanoparticle addition is noted both experimentally and theoretically. The results showed that at the hot fluid inlet temperature of 75?C, the increase in the Nusselt number is maximum with volume concentrations of 0.6 and 0.8% for ZnO and TiO2 nanofluids, respectively. The corresponding maximum Nusselt number enhancements are about 11.5 and 21.4%, respectively, for the base fluid volume fraction of 30:70 (EG:W). There is good agreement between the results calculated from experimental values and the correlation.

Optimum Design of Vent Pipe of Fire Station by Using Analytical Approach of Heat Transfer

2017 ◽  
Vol 865 ◽  
pp. 143-148
Author(s):  
Gyung Ju Kang ◽  
Seok Swoo Cho ◽  
Sung Riong Lee
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Kinematic Viscosity ◽  
Orthogonal Arrays ◽  
Temperature Series ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Objective Functions ◽  
Heat Transfer Theory ◽  
Fire Station

This paper presents the optimal design of vent pipe in a fire station by using design of experiments and analytical method of heat transfer theory. In order to calculate formulation without using tables, equations in terms of temperature are developed for five air properties such as specific heat, thermal conductivity, kinematic viscosity, density and Prandtl number. It is shown that the equations accurately approximate the variations of air properties in terms of temperature. Series of design analysis are performed under considering the process parameters such as inlet temperature, pipe diameter and heat transfer rate. Orthogonal arrays of L27 are used. The signal-to-noise (S/N) and analysis of variance (ANOVA) are utilized to determine the effect of parameters on objective functions, surface temperature and outlet temperature. From the results it is clear that inlet temperature is prominent on objective function.

scholarly journals Research on the Heating of Deicing Fluid in a New Reshaped Coiled Tube

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Mengli Wu ◽  
Chiyu Wang ◽  
Yunpeng Li ◽  
Qi Nie
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
Heating System ◽  
High Viscosity ◽  
Negative Influence ◽  
Heating Time ◽  
Temperature Fields ◽  
Outlet Temperature ◽  
Coiled Tube ◽  
Deicing Fluid

Aircraft ground deicing operation is significant to ensure civil flight safety in winter. Helically coiled tube is the important heat exchanger in Chinese deicing fluid heating system. In order to improve the deicing efficiency, the research focuses on heat transfer enhancement of deicing fluid in the tube. Based on the field synergy principle, a new reshaped tube (TCHC) is designed by ring-rib convex on the inner wall. Deicing fluid is high viscosity ethylene-glycol-based mixture. Because of the power function relation between high viscosity and temperature, viscosity has a negative influence on heat transfer. The number of ring-ribs and inlet velocity are two key parameters to the heat transfer performance. For both water and ethylene glycol, the outlet temperature rises when the number of ring-ribs increases to a certain limit. However, the increasing of velocity reduces heating time, which results in lower outlet temperature. The heating experiment of the original tube is conducted. The error between experiment and simulation is less than 5%. The outlet temperature of TCHC increases by 3.76%. As a result, TCHC efficiently promotes the coordination of velocity and temperature fields by changing the velocity field. TCHC has enhanced heat transfer of high viscosity deicing fluid.

Comparison of Three-Rod Bundle Data With Existing Heat-Transfer Correlations for Bare Vertical Tubes

2010 ◽  
Author(s):  
Krysten King ◽  
Amjad Farah ◽  
Sahil Gupta ◽  
Sarah Mokry ◽  
Igor Pioro
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Annular Channel ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Rod Bundle ◽  
Nuclear Systems ◽  
Heat Transfer Correlations ◽  
Vertical Tubes ◽  
Bare Tube

Many heat-transfer correlations exist for bare tubes cooled with SuperCritical Water (SCW). However, there is very few correlations that describe SCW heat transfer in bundles. Due to the lack of extensive data on bundles, a limited dataset on heat transfer in a SCW-cooled bundle was studied and analyzed using existing bare-tube correlations to find the best-fit correlation. This dataset was obtained by Razumovskiy et al. (National Technical University of Ukraine “KPI”) in SCW flowing upward in a vertical annular channel (1-rod channel) and tight 3-rod bundle consisting of tubes of 5.2-mm outside diameter and 485-mm heated length. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within a range from 800 to 3000 kg/m2s, inlet temperature from 125 to 352°C, outlet temperature up to 372°C and heat flux up to 4.6 MW/m2. The objective of this study is to compare bare-tube SCW heat-transfer correlations with the data on 1- and 3-rod bundles. This work is in support of SuperCritical Water-cooled Reactors (SCWRs) as one of the six concepts of Generation-IV nuclear systems. SCWRs will operate at pressures of ∼25MPa and inlet temperatures of 350°C.

Numerical and Experimental Investigations on Heat Transfer Phenomena of an Aluminium Microchannel Heat Sink

2011 ◽  
Vol 145 ◽  
pp. 129-133 ◽  
Author(s):  
Thanhtrung Dang ◽  
Ngoctan Tran ◽  
Jyh Tong Teng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Sink ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Microchannel Heat Sink ◽  
Maximum Heat

The study was done both numerically and experimentally on the heat transfer behaviors of a microchannel heat sink. The solver of numerical simulations (CFD - ACE+software package) was developed by using the finite volume method. This numerical method was performed to simulate for an overall microchannel heat sink, including the channels, substrate, manifolds of channels as well as the covered top wall. Numerical results associated with such kinds of overall microchannel heat sinks are rarely seen in the literatures. For cases done in this study, a heat flux of 9.6 W/cm2was achieved for the microchannel heat sink having the inlet temperature of 25 °C and mass flow rate of 0.4 g/s with the uniform surface temperature of bottom wall of the substrate of 50 °C; besides, the maximum heat transfer effectiveness of this device reached 94.4%. Moreover, in this study, when the mass flow rate increases, the outlet temperature decreases; however, as the mass flow rate increases, the heat flux of this heat sink increases also. In addition, the results obtained from the numerical analyses were in good agreement with those obtained from the experiments as well as those from the literatures, with the maximum discrepancies of the heat fluxes estimated to be less than 6 %.

Design of a Micromix Fuel Injector for High Temperature Hybrid Concentrated Solar Power Plants

2014 ◽  
Author(s):  
Shane Coogan ◽  
Klaus Brun ◽  
David Teraji
Keyword(s):  
Power Plants ◽  
Solar Power ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Fuel Injector ◽  
Concentrated Solar Power ◽  
Output Variability ◽  
Increased Risk ◽  
In Series ◽  
Solar Power Plants

The hybrid air Brayton concentrated solar power plant (CSP) combines a natural gas fired combustor in series with a traditional CSP system. The combination boosts turbine inlet temperature above the receiver temperature and reduces output variability. However, a combustor operating in this mode must tolerate an inlet air temperature equal to the solar receiver outlet temperature, which is expected to be as much as 1,000°C for next generation designs. High inlet temperature hybrid combustors must achieve low NOx emissions in spite of the increased risk for autoignition and flashback. In addition, the hybrid injector must be able to adjust to the variability inherent to the solar source. The design of a multibank micromix injector that meets these challenges is described with emphasis on its NOx and CO emissions characteristics.

Heat Transfer to Supercritical Water in Vertical 7-Rod Bundle

2008 ◽  
Author(s):  
V. G. Razumovskiy ◽  
E. N. Pis’mennyy ◽  
A. E. Koloskov ◽  
I. L. Pioro
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Supercritical Water ◽  
Heat Fluxes ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Rod Bundle ◽  
Temperature Regimes ◽  
Outside Diameter ◽  
Heated Length

The results of heat transfer to supercritical water flowing upward in a vertical tight 7-rod bundle consisting of tubes of 5.2-mm outside diameter and 485-mm heated length are presented. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within the range from 700 to 1500 kg/m2s, inlet temperature from 125 to 325°C, outlet temperature up to 379°C and heat flux up to 1.6 MW/m2 (heat flux rate up to 1.5 kJ/kg). Temperature regimes of the bundle cooled by supercritical water were stable and easily reproducible within the whole range of the mass and heat fluxes, even when a deteriorated heat transfer took place. The data resulted from the study could be applicable for a reference estimation of heat transfer in future designs of the fuel bundles.

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