scholarly journals Experimental investigation of heat transfer performance coefficient in tube bundle of shell and tube heat exchanger in two-phase flow

2014 ◽  
Vol 35 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Marcin Karaś ◽  
Daniel Zając ◽  
Roman Ulbrich
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Tube Bundle ◽  
Limiting Current ◽  
Phase Flow ◽  
Two Phase ◽  
Tube Heat Exchanger

Abstract This paper presents the results of studies in two phase gasliquid flow around tube bundle in the model of shell tube heat exchanger. Experimental investigations of heat transfer coefficient on the tubes surface were performed with the aid of electrochemical technique. Chilton-Colburn analogy between heat and mass transfer was used. Twelve nickel cathodes were mounted on the outside surface of one of the tubes. Measurement of limiting currents in the cathodic reduction of ferricyanide ions on nickel electrodes in aqueous solution of equimolar quantities of K3Fe(CN)6 and K4Fe(CN)6 in the presence of NaOH basic solution were applied to determine the mass transfer coefficient. Controlled diffusion from ions at the electrode was observed and limiting current plateau was measured. Measurements were performed with data acquisition equipment controlled by software created for this experiment. Mass transfer coefficient was calculated on the basis of the limiting current measurements. Results of mass transfer experiments (mass transfer coefficient) were recalculated to heat transfer coefficient. During the experiments, simultaneously conducted was the the investigation of two-phase flow structures around tubes with the use of digital particle image velocimetry. Average velocity fields around tubes were created with the use of a number of flow images and compared with the results of heat transfer coefficient calculations.

A Natural Circulation Model of the Closed Loop, Two-Phase Thermosyphon for Electronics Cooling

2001 ◽  
Author(s):  
S. I. Haider ◽  
Yogendra K. Joshi ◽  
Wataru Nakayama
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Closed Loop ◽  
Two Phase Flow ◽  
Natural Circulation ◽  
Saturation Temperature ◽  
Electronics Cooling ◽  
Phase Flow ◽  
Two Phase

Abstract The study presents a model for the two-phase flow and heat transfer in the closed loop, two-phase thermosyphon (CLTPT) involving co-current natural circulation. Most available models deal with two-phase thermosyphons with counter-current circulation within a closed, vertical, wickless heat pipe. The present research focuses on CLTPTs for electronics cooling that face more complex two-phase flow patterns than the vertical heat pipes, due to closed loop geometry and smaller tube size. The present model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser, and the falling tube. The homogeneous two-phase flow model is used to evaluate the friction pressure drop of the two-phase flow imposed by the available gravitational head through the loop. The saturation temperature dictates both the chip temperature and the condenser heat rejection capacity. Thermodynamic constraints are applied to model the saturation temperature, which also depends upon the local heat transfer coefficient and the two-phase flow patterns inside the condenser. The boiling characteristics of the enhanced structure are used to predict the chip temperature. The model is compared with experimental data for dielectric working fluid PF-5060 and is in general agreement with the observed trends. The degradation of condensation heat transfer coefficient due to diminished vapor convective effects, and the presence of subcooled liquid in the condenser are expected to cause higher thermal resistance at low heat fluxes. The local condensation heat transfer coefficient is a major area of uncertainty.

Experimental Investigation of Heat Transfer Enhancement of Shell and Tube Heat Exchanger Using SnO2-Water and Ag-Water Nanofluids

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
S. V. Sridhar ◽  
R. Karuppasamy ◽  
G. D. Sivakumar
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer Coefficient ◽  
Two Phase ◽  
Tube Heat Exchanger ◽  
Shell And Tube

Abstract In this investigation, the performance of the shell and tube heat exchanger operated with tin nanoparticles-water (SnO2-W) and silver nanoparticles-water (Ag-W) nanofluids was experimentally analyzed. SnO2-W and Ag-W nanofluids were prepared without any surface medication of nanoparticles. The effects of volume concentrations of nanoparticles on thermal conductivity, viscosity, heat transfer coefficient, fiction factor, Nusselt number, and pressure drop were analyzed. The results showed that thermal conductivity of nanofluids increased by 29% and 39% while adding 0.1 wt% of SnO2 and Ag nanoparticles, respectively, due to the unique intrinsic property of the nanoparticles. Further, the convective heat transfer coefficient was enhanced because of improvement of thermal conductivity of the two phase mixture and friction factor increased due to the increases of viscosity and density of nanofluids. Moreover, Ag nanofluid showed superior pressure drop compared to SnO2 nanofluid owing to the improvement of thermophysical properties of nanofluid.

Mass Transfer Coefficient behind an Orifice in Two-phase Flow

2016 ◽  
Vol 2016.21 (0) ◽  
pp. D114
Author(s):  
Takayuki YAMAGATA ◽  
Hidefumi TSURUTA ◽  
Yuhei NISHII ◽  
Nobuyuki Fujisawa ◽  
Fumio INADA
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase

Impact of Channel Geometry on Two-Phase Flow Heat Transfer Characteristics of Refrigerants in Microchannel Heat Exchangers

1998 ◽  
Vol 120 (2) ◽  
pp. 485-491 ◽  
Author(s):  
T. S. Ravigururajan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Heat ◽  
The Heat Transfer Coefficient

Microchannel surfaces, often machined to 20 to 1000 μm in width and depth, are employed in high-heat-flux applications. However, a large number of variables, control the two-phase flow heat transfer coefficient. The pressure, the surface heat flux, and the mass flux significantly affect the thermal transport. Experiments were conducted on a setup that was built for testing microchannel heat exchanges. The parameters considered in the study are power input: 20 to 300 W, volume flow rate: 35 to 300 ml/min, quality: 0 to 0.5, inlet subcooling: 5 to 15°C. The results indicate that the heat transfer coefficient and pressure drop are functions of the flow quality, the mass flux, and, of course, the heat flux and the related surface superheat. The heat transfer coefficient decreases from a value of 12,000 W/m2-K to 9000, W/m2-K at 80°C, when the wall superheat is increased from 10 to 80°C. The coefficient decreases by 30 percent when the exit vapor quality is increased from 0.01 to 0.65.

An Inverse Method for Drying at High Mass Transfer Biot Number

2003 ◽  
Author(s):  
Gligor H. Kanevce ◽  
Ljubica P. Kanevce ◽  
George S. Dulikravich ◽  
Marcelo J. Colac¸o
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Heat And Mass Transfer ◽  
Biot Number ◽  
Temperature Sensitivity ◽  
Sensitivity Coefficient ◽  
The Heat Transfer Coefficient

The inverse problem of using temperature measurements to estimate the moisture content and temperature-dependent moisture diffusivity together with the heat and mass transfer coefficients is analyzed in this paper. In the convective drying practice, usually the mass transfer Biot number is very high and the heat transfer Biot number is very small. This leads to a very small temperature sensitivity coefficient with respect to the mass transfer coefficient when compared to the temperature sensitivity coefficient with respect to the heat transfer coefficient. Under these conditions the relative error of the estimated mass transfer coefficient is high. To overcome this problem, in this paper the mass transfer coefficient is related to the heat transfer coefficient through the analogy between the heat and mass transfer processes in the boundary layer. The resulting parameter estimation problem is then solved by using a hybrid constrained optimization algorithm OPTRAN.

Two-Phase Flow Conjugate Heat Transfer in Wavy Microchannel

2018 ◽  
Author(s):  
Nishant Tiwari ◽  
Manoj Kumar Moharana
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Bubble Nucleation ◽  
Bottom Surface ◽  
Substrate Thickness ◽  
Phase Flow ◽  
Two Phase

Flow boiling in microchannel heat sink offers an effective cooling solution for high power density micro devices. A three-dimensional numerical study based on volume of fraction model (VOF) coupled with evaporation condensation model accounting for the liquid-vapor phase change is undertaken to recreate vapor bubble formation in saturated flow boiling in wavy microchannel. Constant wall heat flux imposed at the bottom surface of the substrate while other faces are insulated. To understand the conjugate effects, simulations has been carried out for substrate thickness to channel depth ratio (δsf ∼ 1–5), substrate wall to fluid thermal conductivity ratio (ksf ∼ 22–300) and waviness (γ ∼ 0.008–0.04). Bubble nucleation, growth, and departure of bubble plays a significant role in heat transfer and pressure drop characteristics in two-phase flow in wavy microchannel. The coolant (water) temperature at the inlet is taken to be 373 K while flow was at atmospheric pressure. This makes shorter waiting period of bubble nucleation, and the number density of bubbles on the solid surface increases. This results in enhancement of the boiling effect, and thus with the presence of bubbles, the mixing of laminar boundary layers improves and enhances the overall heat transfer coefficient. Channel amplitude play an important factor that can suitably reduce the friction factor and enhances the heat transfer coefficient.

Mass Transfer Coefficient Measurement in Water/Oil/Gas Multiphase Flow

2000 ◽  
Vol 123 (2) ◽  
pp. 144-149 ◽  
Author(s):  
H. Wang ◽  
D. Vedapuri ◽  
J. Y. Cai ◽  
T. Hong ◽  
W. P. Jepson
Keyword(s):  
Mass Transfer ◽  
Multiphase Flow ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Slug Flow ◽  
Limiting Current ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Average Mass ◽  
Water Cut

Mass transfer studies in oil-containing multiphase flow provide fundamental knowledge towards the understanding of hydrodynamics and the subsequent effect on corrosion in pipelines. Mass transfer coefficient measurements in two-phase (oil/ferri-ferrocyanide) and three-phase (oil/ferri-ferrocyanide/nitrogen) flow using limiting current density technique were made in 10-cm-dia pipe at 25 and 75 percent oil percentage. Mass transfer coefficients in full pipe oil/water flow and slug flow were studied. A relationship is developed between the average mass transfer coefficient in full pipe flow and slug flow. The mass transfer coefficient decreased with a decrease of in-situ water cut. This was due to the existence of oil phase, which decreased the ionic mass transfer diffusion coefficient.

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