Frictional Pressure Drop Characteristics Research Articles

Experimental investigation of forced convective condensation heat transfer of hydrocarbon refrigerant in a helical tube

In this paper, the characteristics of two-phase heat transfer and frictional pressure drop for hydrocarbon refrigerant propane condensation in a helical tube were experimentally investigated. A new experimental facility was designed to directly measure the wall temperature along a helical tube with the hydraulic diameter of 10 mm. The experimental conditions were set as: mass flux from 200 to 400 kg/(m2·s), heat flux from 1.4 to 9.6 kW/m2 and saturated temperatures from −40 to 27 °C. Also, the effects of mass flux and vapor quality on heat transfer coefficient and frictional pressure drop were studied. Compared with the experimental data, it showed that Shah correlation could well predict heat transfer coefficients within a mean deviation of ±20%, and Friedel correlation and Müller-Steinhagen & Heck correlation both well predicted frictional pressure drop with a mean deviation less than ±20%. These results will provide important instructions for the tube-side design of spiral wound heat exchanger.

Experiment investigation of two-phase flow pattern transition and frictional pressure drop of R600a in a horizontal tube

With the growing concern of environment problems, there are urgent demands for environment-friendly refrigerants in the refrigeration industry. As a natural refrigerant, R600a not only has zero ozone depletion potential and quite low global warming potential, but also has better cooling performance than other refrigerants. Due to its good cooling performance and environment-friendly characteristics, R600a has been used as an alternative refrigerant in heat transfer applications such as refrigerators, freezers, and heat pumps. It is known that accurate prediction of two phase flow pattern transition and frictional pressure drop of R600a in a horizontal tube play an important role in design and optimization of refrigerators, freezers, and heat pumps. According to this issue, a detailed experimental study was carried out to investigate the two-phase flow pattern transition and frictional pressure drop characteristics of R600a in a smooth horizontal tube with an inner diameter of 6 mm. The experiments were performed at conditions covering saturation temperature from 282.4 to 304 K, mass fluxes from 67 to 194 kg/(m2 s). Based on a high speed camera, four main flow regimes can be observed: plug flow, stratified-wavy flow, slug flow and annular flow. The flow map of R600a has been drawn and comparisons between the experimental data of flow patterns and transition lines in the literature have been made. The results showed that with the increase of mass flux, the inception of the annular flow regime occurs earlier. The intermittent flow regime takes place over a narrow range of vapor quality and annular flow regime occupies a wide range of vapor quality. In addition, the trend of Barbieri and Ong and Thome I / A transitions lines are consistent with the experimental data. However, both of them overestimate the inception of the annular flow regime. After taking the influence of vapor inertia, liquid viscous and surface tension forces into account, a modified Weber number We * has been introduced to the new flow pattern transition model. Based on the relationship of X tt and We *, a new correlation has been proposed and it can well fit with the experimental data of flow pattern. Furthermore, a detailed discuss of frictional pressure drop of annular flow and non-annular flow has been made. The results indicated that frictional pressure drop increases with the increases of vapor quality. The tendency of frictional pressure drop presents different the changing laws in different flow regime. The frictional pressure drop increases slowly in the non-annular flow regime while it increases rapidly when the flow pattern turns into the annular flow regime. The reason is that the vapor-phase pressure drop often dominates the total two-phase frictional pressure drop. The annular flow regime owns higher void fraction than the non-annular flow regime. Nine classic prediction correlations of pressure drop were evaluated and the results showed that the correlation of Gronnerud and Muller-Steinhagen and Heck give the best fit to the experimental frictional pressure drop of annular flow and non-annular flow with a mean absolute relative deviation of 38.5% and 19.7% respectively.

Effect of inclination on frictional pressure drop of supercritical water flows in internally ribbed tubes: An experimental study

Internally ribbed tubes are highly advantageous for heat transfer enhancement in high pressure water flows. But these tubes increase the frictional pressure drop in comparison with smooth tubes. In this paper the frictional pressure drop characteristics of subcritical, near critical and supercritical water upward flows inside the inclined rifled tube with inclinations angles of 5, 20, 30, 45 and 90° with respect to the horizontal plane are studied experimentally. The test pressures were 15, 21.5, 22.5, 25 and 28MPa, the heat and mass fluxes were kept at 400kW/m2kW/m2 and 800kg/m2s. The effect of heat and mass fluxes on frictional pressure drop in inclined tubes was also investigated. The results showed the least frictional pressure drop for both subcritical and supercritical flows occurs at 5°. The effect of mass flux on frictional pressure drop in all water flow conditions was more considerable than the heat flux.

Effect of rolling motion on two-phase frictional pressure drop of boiling flows in a rectangular narrow channel

In order to investigate the two-phase frictional pressure drop characteristics of boiling flow in a rectangular narrow channel under rolling motion, a series of experiments and theoretical analysis are performed. The results demonstrate that the total additional pressure drop fluctuation has the same period with the rolling motion, and the fluctuation amplitude increases with the increase of rolling amplitude and rolling frequency. The time average additional pressure drop is 2–3 orders of magnitude smaller than that of frictional pressure drop in the boiling region. The fluctuation amplitude of the two-phase frictional pressure drop increases with increasing rolling amplitude, rolling period and heat flux, while it decreases with the increase of system pressure. Compared with the additional pressure drop in two-phase regions the outlet quality of channel and the space variation of the experimental loop are the main reasons that induce the fluctuation of two-phase frictional pressure drop. The mass flux fluctuation varies with the fluctuation of two-phase frictional pressure drop, and the fluctuation amplitude of mass flux increases with the increase of rolling amplitude and rolling period. The phase lag between the fluctuation of mass flux and frictional pressure drop is approximately equal to 1/4 rolling period.

마이크로핀관내 냉동기유가 초임계 이산화탄소의 열전달과 압력강하에 미치는 영향

본 논문은 수평 마이크로핀관내 초임계 <TEX>$CO_2$</TEX>와 PAG 혼합물의 열전달과 압력강하 특성에 대해서 실험적으로 연구한 것이다. <TEX>$CO_2$</TEX>와 PAG 혼합물의 열전달계수는 압력이 10 MPa이고, 질량유속은 520 kg/<TEX>$m^2s$</TEX>이며, PAG 오일 농도는 0.06~2.26%에서 측정하였다. PAG 오일농도가 0.3%인 경우, <TEX>$CO_2$</TEX>와 PAG 혼합물의 열전달계수와 압력강하는 순수 <TEX>$CO_2$</TEX> 냉매의 열전달계수와 동일한 경향을 나타내었다. 그리고 PAG 질량농도가 2.26%인 경우, 초임계 온도근처에서 측정한 열전달계수는 순수 <TEX>$CO_2$</TEX>의 열전달계수 보다 약 50%정도 낮게 나타났다. 마찰압력강하는 <TEX>$60^{\circ}C$</TEX>의 <TEX>$CO_2$</TEX> 평균온도에서 순수 <TEX>$CO_2$</TEX>의 압력강하보다 약 1.6배 더 높게 나타났다. This paper presents an experimental study of heat transfer and pressure drop characteristics of supercritical carbon dioxide with PAG inside a horizontal microfin tube. Heat transfer coefficient and pressure drop gradients were measured at 10 MPa in pressure and 520 kg/<TEX>$m^2s$</TEX> in mass flux with variation of PAG mass concentration from 0.06% to 2.26%. The tendencies of both heat transfer and frictional pressure drop characteristics show the same as those of pure <TEX>$CO_2$</TEX> up to 0.3% in PAG mass concentration. In case of 2.26% in PAG mass concentration, measured heat transfer coefficients showed 50% lower than those of pure <TEX>$CO_2$</TEX> near the pseudocritical temperature and measured frictional pressure drop gradients show 1.6 times higher in comparison with those of pure <TEX>$CO_2$</TEX> at <TEX>$60^{\circ}C$</TEX> in <TEX>$CO_2$</TEX> bulk temperature.

Experimental Study of Two-Phase Flow Regime and Pressure Drop in a Particulate Bed Packed with Multidiameter Particles

This paper documents an experimental study on two-phase flow regimes and frictional pressure drop characteristics in a particulate (porous) bed packed with multidiameter (1.5-, 3-, and 6-mm) glass spheres. The experimental results provide new data to validate/develop hydrodynamic models for coolability analysis of debris beds formed in fuel-coolant interactions during a postulated severe accident. The POMECO-FL test facility is employed to perform the experiment, with the spheres packed in a test section of 90 mm diameter and 635 mm height. The pressure drops are measured for air/water two-phase flow through the packed bed, and flow patterns are obtained by means of visual observations. Meanwhile, local void fraction in the center of the bed is measured by a microconductive probe.The experimental results show that the frictional pressure drop of single-phase flow through the bed can be predicted by the Ergun equation, if the area mean diameter of the particles is chosen in the calculation. Given the so-determined effective particle diameter, the estimation of the Reed model for two-phase flow pressure gradient in the bed has a good agreement with the experimental data. The characteristics of the local void fraction can be used to predict flow pattern and mean void fraction. It is observed that slug flow prevails when the mean void fraction is <0.5, whereas annular flow dominates after the mean void fraction is >0.7. If the effective particle diameter is further used as an influential parameter in flow pattern identification, the observed flow regimes of two-phase flow in porous media are well predicted by the existing flow pattern map.

Two-Phase Frictional Pressure Drop Characteristics of R410A-Oil Mixture Flow Condensation inside 4.18 mm and 1.6 mm I.D. Horizontal Smooth Tubes

Two-phase frictional pressure drop characteristics of R410A-oil mixture flow condensation inside 4.18 mm (0.165 in) and 1.6 mm (0.063 in) I.D. diameter horizontal smooth tubes were investigated experimentally. The experimental condensing temperature is 40°C (104°F), and the nominal oil concentration range is from 0% to 5%. The test results indicate that the presence of oil always decreases the flow condensation frictional pressure drop, and the decrement increases with the nominal oil concentration. The decrements for 4.18 mm (0.165 in.) and 1.6 mm (0.063 in.) are 1%~19.5% and 1.5%~17.4% tubes, respectively. A new correlation for the frictional pressure drop of R410A-oil mixture flow condensation inside smooth tubes is proposed and agrees with 96% of the experimental data within a deviation of −20%~+30%.

Experimental Investigation of Two-Phase Pressure Drop in a Microchannel

Experimental results of two-phase pressure drop in a horizontal circular microchannel are reported in this paper. A test tube was made of fused silica having an internal diameter of 781 μm with a total length of 261 mm and a heated length of 191 mm. The outer surface of the test tube was coated with an electrically conductive thin layer of ITO (indium tin oxide) for direct heating of the test section. Refrigerants R134a and R245fa were used as the working fluids, and mass flux during the experiments was varied between 100 and 650 kg/m2-s. Experiments were performed at two different system pressures corresponding to saturation temperatures of 25°C and 30°C for R134a and at three different system pressures corresponding to saturation temperatures of 30°C, 35°C, and 40°C for R245fa. Two-phase frictional pressure drop characteristics with variation of mass flux, vapor fraction, saturation temperature, and heat flux were explored in detail. Finally, the prediction capability of some well-known correlations available in the literature, some developed for macrochannels and others especially developed for microchannels, was assessed.

Measurement and correlation of frictional pressure drop of refrigerant-based nanofluid flow boiling inside a horizontal smooth tube

The objective of this paper is to investigate the effect of nanoparticle on the frictional pressure drop characteristics of refrigerant-based nanofluid flow boiling inside a horizontal smooth tube, and to present a correlation for predicting the frictional pressure drop of refrigerant-based nanofluid. R113 refrigerant and CuO nanoparticle were used for preparing refrigerant-based nanofluid. Experimental conditions include mass fluxes from 100 to 200 kg m −2 s −1, heat fluxes from 3.08 to 6.16 kW m −2, inlet vapor qualities from 0.2 to 0.7, and mass fractions of nanoparticles from 0 to 0.5 wt%. The experimental results show that the frictional pressured drop of refrigerant-based nanofluid increases with the increase of the mass fraction of nanoparticles, and the maximum enhancement of frictional pressure drop is 20.8% under above conditions. A frictional pressure drop correlation for refrigerant-based nanofluid is proposed, and the predictions agree with 92% of the experimental data within the deviation of ±15%.

Pressure drop during horizontal flow boiling of R410A/oil mixture in 5 mm and 3 mm smooth tubes

Two-phase frictional pressure drop characteristics of R410A/oil mixture flow boiling in horizontal small smooth tubes with outside diameters of 5.0 mm and 3.0 mm were investigated experimentally. Experimental conditions cover nominal oil concentrations from 0% to 5%. The test results show that the frictional pressure drop of R410A initially increases with the increase of vapor quality and then decreases, presenting a local maximum in the vapor quality range between 0.6 and 0.8; the presence of oil increases two-phase frictional pressure drop about 0–120% and 0–90% in present test conditions for 5.0 mm O.D. smooth tube and 3.0 mm O.D. smooth tube, respectively, and the increase is evident at high vapor qualities. The vapor-phase multiplier of R410A/oil mixture based on the mixture properties decreases with the decrease of tube diameter. A new vapor-phase multiplier correlation to predict the local frictional pressure drop of R410A/oil mixture flow boiling inside smooth tubes is developed based on local properties of refrigerant–oil mixture, and the deviations of the new correlation are within ±25% from the experimental data.

Adiabatic Horizontal and Vertical Pressure Drop of Carbon Dioxide Inside Smooth and Microfin Tubes at Low Temperatures

This paper presents the pressure drop data and the analysis of adiabatic CO2 flow in horizontal and vertical smooth and microfin tubes at saturation temperatures around −20°C. The test tubes had 3.48mm inner diameter smooth tube and a 3.51mm melt-down diameter microfin tube. The test was performed over a mass flux range of 200–800kg∕m2s and at saturation temperatures of −25°C and −15°C. The effects of various parameters—mass flux, saturated temperature, and tube diameter—on pressure drop were qualitatively analyzed. The analyses showed that the frictional pressure drop characteristics of vertical two-phase flow were much different from that of the horizontal two-phase flow. The microfin tube can be considered as “very rough tube” having the roughness of “fin height.” The data were compared with several correlations. The existing frictional pressure drop correlation is sufficient to predict the horizontal pressure drop in smooth tube. For the vertical pressure drop, the simple combination of the frictional pressure drop and void fraction model was in comparatively good agreement. However, the qualitative results showed that there were some limits to cover the different mechanisms related to the interfacial shear stress. The average enhancement factors and penalty factors evidenced that it was not always true that the internally finned geometry guaranteed the superior in-tube condensation performance of microfin tube in refrigeration system and air-conditioning systems.

Measurement and Correlation of Frictional Pressure Drop of R-410A/Oil Mixture Flow Boiling in a 7 mm Straight Smooth Tube

Two-phase frictional pressure drop characteristics of an R-410A/oil mixture flow boiling inside a straight, smooth tube with an outside diameter of 7.0 mm were investigated experimentally. Experimental parameters include an evaporation temperature of 5°C, mass fluxes from 200 to 400 kg/(m2·s), heat fluxes from 7.56 to 15.12 kW/m2, inlet vapor qualities from 0.2 to 0.7, and nominal oil concentrations from 0% to 5%. The test results show that frictional pressure drop of an R-410A/oil mixture increases with the mass flux, the presence of oil enhances two-phase frictional pressure drop, and the effect of oil on frictional pressure drop is found to be more evident at higher vapor qualities where the local oil concentrations are higher. A new correlation to predict the local frictional pressure drop of an R-410A/oil mixture flow boiling inside a straight, smooth tube is developed based on the local properties of the refrigerant/oil mixture, and it agrees with 92% of the experimental data within a deviation of ±15%.

Measurement and correlation of frictional two-phase pressure drop of R410A/POE oil mixture flow boiling in a 7 mm straight micro-fin tube

Two-phase frictional pressure drop characteristics of R410A/POE oil mixture flow boiling inside a straight micro-fin tube with the outside diameter of 7.0 mm were investigated experimentally. Experimental parameters include the evaporation temperature of 5 °C, the mass flux from 200 to 400 kg/(m 2 s), the heat flux from 7.56 to 15.12 kW/m 2, the inlet vapor quality from 0.2 to 0.7, and nominal oil concentration from 0% to 5%. The test results show that frictional pressure drop of R410A/POE oil mixture increases with the mass flux, the presence of oil enhances two-phase frictional pressure drop, and the effect of oil on frictional pressure drop is more evident at higher vapor qualities where the local oil concentrations are higher. New correlations to predict the local frictional pressure drop of R410A/POE oil mixture flow boiling inside the straight micro-fin tube are developed based on local properties of refrigerant–oil mixture, and the measured local frictional pressure drop is well correlated with the empirical correlations proposed by the authors.

An experimental study of flow pattern and pressure drop for flow boiling inside microfinned helically coiled tube

In this paper, flow patterns and their transitions for refrigerant R134a boiling in a microfinned helically coiled tube are experimentally observed and analyzed. All the flow patterns occurred in the test can be divided into three dominant regimes, i.e., stratified-wavy flow, intermittent flow and annular flow. Experimental data are plotted in two kinds of flow maps, i.e., Taitel and Dukler flow map and mass flux versus vapor quality flow map. The transitions between various flow regimes and the differences from that in smooth straight tube have also been discussed. Martinelli parameter can be used to indicate the transition from intermittent flow to annular flow. The transition from stratified-wavy flow to annular or intermittent flow is identified in the vapor quality versus mass flux flow map. The flow regime is always in stratified-wavy flow for a mass flux less than 100 kg/m 2 s. The two-phase frictional pressure drop characteristics in the test tube are also experimentally studied. The two-phase frictional multiplier data can be well correlated by Lockhart–Martinelli parameter. Considering the corresponding flow regimes, i.e., stratified and annular flow, two frictional pressure drop correlations are proposed, and show a good agreement with the respective experimental data.

Mixed Convective Low Flow Pressure Drop in Vertical Rod Assemblies: I—Predictive Model and Design Correlation

A predictive theory has been developed for rod bundle frictional pressure drop characteristics under laminar and transitional mixed convection conditions on the basis of the intraassembly and intrasubchannel flow redistributions due to buoyancy for a wide spectrum of radial power profiles and for the geometric arrangements of practical design interest. Both the individual subchannel correlations and overall bundle design correlations have been formulated as multipliers applied to the isothermal friction factors at the same Reynolds numbers. Standard and modified subchannel friction factors have been obtained to be used with spatial-average and bulk-mean densities, respectively. A correlating procedure has been proposed to assess the effects of interacting subchannel flows, developing mixed convective flow, wire wrapping, power skew, rod number, and transition from laminar flow. In contrast to forced convection behavior, a strong rod number effect is present under mixed convection conditions in bundle geometries. The results of this study are of design importance in natural circulation conditions because the mixed convection frictional pressure losses exceed the corresponding isothermal values at the same Reynolds numbers.

Pressure Drops in C0&lt;SUB&gt;2&lt;/SUB&gt; Supercritical Boilers : 2nd Report Dynamic Characteristics of Frictional Pressure Drop

Experimental and analytical investigations were conducted on the dynamic behaviors of the frictional pressure drop in a CO2 forced flow heated loop at supercritical and subcritical pressures near the critical pressure. The step responses of the pressure drop to the step changes of inlet flow rate, heat flux and exit pressure were measured. The analytical results obtained by using a smsll perturbation method and Laplace transformation agreed approximately with the experimental results.

Pressure Losses in Supercritical Pressure Boilers : 1st Report, Static Characteristics of Frictional Pressure Drop

Pressure Losses in Supercritical Pressure Boilers : 1st Report, Static Characteristics of Frictional Pressure Drop

Frictional Pressure Drop in Steam Generating Tubes: 1st Report Static Characteristics of Frictional Pressure Drop

Frictional Pressure Drop in Steam Generating Tubes: 1st Report Static Characteristics of Frictional Pressure Drop

Heat Transfer and Frictional Pressure Drop Characteristics of White Fuming Nitric Acid

An e x p e r i m e n t a l i nves t iga t ion was c o n d u c t e d t o d e t e r m i n e t h e h e a t t r ans f e r a n d fluid f r ic t ion cha rac t e r i s t i c s of w h i t e f u m i n g n i t r i c ac id (WFNA) u n d e r cond i t i ons s i m u l a t i n g regenera t ive cool ing of a rocke t m o t o r w i t h WFNA. U n d e r c o n d i t i o n s w h e r e n o local boi l ing occur red i n t h e t e s t sec t ion t h e r e c o m m e n d e d h e a t t r ans f e r e q u a t i o n (modified C o l b u r n e q u a t i o n ) is j = 0.023 NRe -0 .2