The Experts below are selected from a list of 60 Experts worldwide ranked by ideXlab platform
A B Biswas - One of the best experts on this subject based on the ideXlab platform.
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frictional pressure drop of air non newtonian liquid flow through helical coils in horizontal orientation
Canadian Journal of Chemical Engineering, 2008Co-Authors: A B BiswasAbstract:Investigations have been carried out to evaluate the two-phase frictional pressure drop for air non-Newtonian liquid flow through helical coils in horizontal orientation. The experiments performed using 36 different helical coils and 4 different concentrations of sodium salt of carboxymethyl—cellulose (SCMC) as non-Newtonian liquids. The effects of air and liquid flow rate, coil diameter, helix angle and liquid properties- on two-phase frictional pressure drop have been discussed. An attempt has been made to fit the experimental two-phase frictional pressure drop data by the Lockhart and Martinelli, Chem. Eng. Prog. 45, 39–48 (1949) Correlation and the modified Lockhart-Martinelli Correlation as presented by different authors. In another approach, friction factor method was adopted to correlate the experimental data by dimensional analysis. The Correlation developed predicts the two-phase frictional pressure drop with acceptable statistical accuracy. On a effectue des recherches afin d'evaluer la perte de charge frictionnelle diphasique pour un ecoulement liquide non newtonien d'air dans des serpentins helicoidaux orientes horizontalement. Les experiences ont ete menees avec trente-six serpentins helicoidaux differents et quatre concentrations differentes de sel de sodium de carboxymethylcellulose (SCMC) comme liquides non newtonien. Les effets du debit d'air et de liquide, du diametre de serpentin, de l'angle d'helice et des proprietes de liquide sur la perte de charge frictionnelle diphasique ont ete examines. Une tentative a ete faite pour caler les donnees experimentales de la perte de charge de pression frictionnelle diphasique par la Correlation de Lockhart et Martinelli (Chemical Engineering Progress, 45, 39-48 (1949) et la Correlation de Lockhart-Martinelli modifiee telles qu'elles sont presentees par differents auteurs. Par ailleurs, la methode du facteur de friction a ete adoptee pour correler les donnees experimentales par l'analyse dimensionnelle. La Correlation developpee predit la perte de charge frictionnelle diphasique avec une precision statistique acceptable.
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two phase frictional pressure drop of gas non newtonian liquid flow through helical coils in vertical orientation
Chemical Engineering and Processing, 2008Co-Authors: A B BiswasAbstract:Abstract Investigations have been carried out to evaluate the two-phase frictional pressure drop for gas–non-Newtonian liquid flow through helical coils in vertical orientation. The experiments performed using nine coils and four different non-Newtonian liquids. The effects of gas and liquid flow rate, coil diameter, and liquid properties on two-phase frictional pressure drop have been illustrated. An attempt has been made to fit the experimental two-phase frictional pressure drop data by the Lockhart and Martinelli [R.W. Lockhert, R.C. Martinelli, Proposed Correlation of data for isothermal two-phase two components flow in pipes, Chem. Eng. Prog. 45 (1949) 39–48] Correlation and the modified Lockhart–Martinelli Correlation as presented by different authors. In another approach, friction factor method was adopted to correlate the experimental data by dimensional analysis. The Correlation developed predicts the two-phase frictional pressure drop with acceptable statistical accuracy.
Eiji Hihara - One of the best experts on this subject based on the ideXlab platform.
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boiling heat transfer of hfo 1234yf flowing in a smooth small diameter horizontal tube
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Shizuo Saitoh, Chaobin Dang, Yoshitaka Nakamura, Eiji HiharaAbstract:The flow boiling heat transfer coefficient of the low-GWP (global warming potential) refrigerant HFO-1234yf inside a smooth small-diameter horizontal tube (inner diameter: 2 mm) was experimentally investigated. The local heat transfer coefficient was measured at heat fluxes of 6–24 kW m -2 , mass fluxes of 100–400 kg m -2 s -1 , evaporating temperature of 288.15 K, and inlet vapor quality of 0–0.25. The results show that the effect of heat flux on the heat transfer was large at low vapor quality, while the effect of mass flux was large at high vapor quality. The heat transfer coefficient of HFO-1234yf was almost the same as that of R-134a. The heat transfer coefficients calculated based on Correlations with Saitoh et al. agreed well with the measured values compared to other Correlations. The measured pressure drop agreed well with that predicted by the Lockhart-Martinelli Correlation.
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effect of tube diameter on boiling heat transfer of r 134a in horizontal small diameter tubes
International Journal of Heat and Mass Transfer, 2005Co-Authors: Shizuo Saitoh, Hirofumi Daiguji, Eiji HiharaAbstract:Abstract The boiling heat transfer of refrigerant R-134a flow in horizontal small-diameter tubes with inner diameter of 0.51, 1.12, and 3.1 mm was experimentally investigated. Local heat transfer coefficient and pressure drop were measured for a heat flux ranging from 5 to 39 kW/m 2 , mass flux from 150 to 450 kg/m 2 s, evaporating temperature from 278.15 to 288.15 K, and inlet vapor quality from 0 to 0.2. Flow patterns were observed by using a high-speed video camera through a sight glass at the entrance of an evaporator. Results showed that with decreasing tube diameter, the local heat transfer coefficient starts decreasing at lower vapor quality. Although the effect of mass flux on the local heat transfer coefficient decreased with decreasing tube diameter, the effect of heat flux was strong in all three tubes. The measured pressure drop for the 3.1-mm-ID tube agreed well with that predicted by the Lockhart–Martinelli Correlation, but when the inner tube diameter was 0.51 mm, the measured pressure drop agreed well with that predicted by the homogenous pressure drop model. With decreasing tube diameter, the flow inside a tube approached homogeneous flow. The contribution of forced convective evaporation to the boiling heat transfer decreases with decreasing the inner tube diameter.
Seungjin Kim - One of the best experts on this subject based on the ideXlab platform.
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air water two phase bubbly flow across 90 vertical elbows part ii modeling
International Journal of Heat and Mass Transfer, 2018Co-Authors: Shouxu Qiao, Ran Kong, Seungjin KimAbstract:Abstract Following Part (I) of the current study, which presents the experimental results of the elbow effects on two-phase flow parameters in bubbly flow, Part (II) develops models and Correlations to predict the evolution of these parameters across and downstream of 90° vertical-upward and vertical-downward elbows. To quantify the length requires for the effects of the elbows to dissipate (or the dissipation length), the strength of elbows is defined as the variance of the local void fraction distribution. The axial development of the elbow-strength is modeled by an exponential function of the axial development length based on the experimental data. Then, the dissipation length of the elbow is determined by characterizing the evolution of the elbow-strength parameter. The elbow-strength parameter is also used to correlate the void-weighted bubble velocity and covariance terms in the interfacial area transport equation (IATE). The two-phase pressure drop across vertical elbows is modeled with a modified Lockhart-Martinelli Correlation which considers the additional pressure drop induced by elbows. To evaluate the above developed models and Correlations, they are implemented into the IATE applicable to the elbow-influenced region. The established IATE together with the available IATE of different flow orientations in straight channels are implemented to predict the interfacial area transport from the vertical-upward to horizontal to vertical-downward two-phase flow across elbows. It is found that the interfacial area concentration predictions are in good agreement with the experimental data with an average absolute percent difference of ±6% throughout the test section. The individual contributions to the interfacial area concentration transport due to each source and sink term in the IATE are discussed, demonstrating that the models and Correlations developed for the two-phase flow parameters in elbow regions are reliable.
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interfacial area transport across a 90 vertical upward elbow in air water bubbly two phase flow
International Journal of Multiphase Flow, 2016Co-Authors: Shouxu Qiao, Seungjin KimAbstract:This study develops a one-group interfacial area transport equation (IATE) for vertical-upward-to-horizontal air–water bubbly two-phase flows through a 90° elbow with a non-dimensional centerline radius of curvature of three. In order to develop the model, an extensive database is established by acquiring local two-phase flow parameters using a four-sensor conductivity probe upstream and downstream of the elbow. The data show there exist three characteristic regions in void distribution, including a bimodal-to-bimodal region, a bimodal-to-single-peaked region, and a developed horizontal flow region with void accumulated at the top of the pipe cross-section. Using the database, the preliminary dissipation length model developed by Yadav et al. (2014b) is improved by including the transition region near the exit of the elbow in addition to the dissipation region. To close the IATE model, the bubble velocity advection term and bubble interaction terms in the IATE are correlated with the parameter characterizing the “elbow-strength”. The two-phase pressure drop across the elbow is modeled using the modified Lockhart–Martinelli Correlation which takes into account the minor loss effect. The closed IATE model is implemented to predict interfacial area transport in vertical-upward-to-horizontal two-phase flow. It is found that the developed model is capable of predicting interfacial area concentration with an average percent difference of less than ±6%.
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two phase minor loss in horizontal bubbly flow with elbows 45 and 90 elbows
Nuclear Engineering and Design, 2010Co-Authors: Seungjin Kim, Gunol Kojasoy, Tangwen GuoAbstract:Abstract The present study investigates the geometric effects of a 45° elbow on the pressure drop due to the minor loss in horizontal bubbly flow. A round glass tube with inner diameter of 50.3 mm is employed as a test section, along which a 45° elbow is installed at L/D = 353.5 from the two-phase mixture inlet. In total, 15 different flow conditions are examined. The local static pressures are measured at four axial locations at L/D = 197, 342, 363 and 419 from the two-phase mixture inlet. The effect of the elbow is clearly demonstrated in the pressure data along the axial direction. In the data analysis, the pressure data previously acquired with a 90° elbow is also utilized as well. The conventional Lockhart–Martinelli Correlation with parameter C = 30 predicts the overall two-phase frictional pressure loss between the inlet and exit of the test section relatively well for both the 90° and 45° elbow experiments. However, it fails to predict the pressure loss across the elbows, because the existing model does not account for the additional loss due to the flow restrictions. In view of this, a new Correlation analogous to Lockhart and Martinelli’s is developed for the two-phase frictional pressure loss across the elbows. The new Correlation with the parameter C = 65 and the minor loss factors of k = 0.58 and k = 0.35 for the 90° and 45° elbows, respectively, yields the best fit to the data. The average percent differences between the predictions made by the new Correlation and the data are ±2.1% and ±1.3% for 90° and 45° cases, respectively.
Shizuo Saitoh - One of the best experts on this subject based on the ideXlab platform.
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boiling heat transfer of hfo 1234yf flowing in a smooth small diameter horizontal tube
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Shizuo Saitoh, Chaobin Dang, Yoshitaka Nakamura, Eiji HiharaAbstract:The flow boiling heat transfer coefficient of the low-GWP (global warming potential) refrigerant HFO-1234yf inside a smooth small-diameter horizontal tube (inner diameter: 2 mm) was experimentally investigated. The local heat transfer coefficient was measured at heat fluxes of 6–24 kW m -2 , mass fluxes of 100–400 kg m -2 s -1 , evaporating temperature of 288.15 K, and inlet vapor quality of 0–0.25. The results show that the effect of heat flux on the heat transfer was large at low vapor quality, while the effect of mass flux was large at high vapor quality. The heat transfer coefficient of HFO-1234yf was almost the same as that of R-134a. The heat transfer coefficients calculated based on Correlations with Saitoh et al. agreed well with the measured values compared to other Correlations. The measured pressure drop agreed well with that predicted by the Lockhart-Martinelli Correlation.
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effect of tube diameter on boiling heat transfer of r 134a in horizontal small diameter tubes
International Journal of Heat and Mass Transfer, 2005Co-Authors: Shizuo Saitoh, Hirofumi Daiguji, Eiji HiharaAbstract:Abstract The boiling heat transfer of refrigerant R-134a flow in horizontal small-diameter tubes with inner diameter of 0.51, 1.12, and 3.1 mm was experimentally investigated. Local heat transfer coefficient and pressure drop were measured for a heat flux ranging from 5 to 39 kW/m 2 , mass flux from 150 to 450 kg/m 2 s, evaporating temperature from 278.15 to 288.15 K, and inlet vapor quality from 0 to 0.2. Flow patterns were observed by using a high-speed video camera through a sight glass at the entrance of an evaporator. Results showed that with decreasing tube diameter, the local heat transfer coefficient starts decreasing at lower vapor quality. Although the effect of mass flux on the local heat transfer coefficient decreased with decreasing tube diameter, the effect of heat flux was strong in all three tubes. The measured pressure drop for the 3.1-mm-ID tube agreed well with that predicted by the Lockhart–Martinelli Correlation, but when the inner tube diameter was 0.51 mm, the measured pressure drop agreed well with that predicted by the homogenous pressure drop model. With decreasing tube diameter, the flow inside a tube approached homogeneous flow. The contribution of forced convective evaporation to the boiling heat transfer decreases with decreasing the inner tube diameter.
Taewoo Lim - One of the best experts on this subject based on the ideXlab platform.
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pressure drop in two phase flow boiling of r134a r123 and their mixture in horizontal tube
International Journal of Air-conditioning and Refrigeration, 2004Co-Authors: Taewoo LimAbstract:An experimental study on the pressure drop during flow boiling for pure refrigerants R134a and R123, and their mixture was carried out in a uniformly heated horizontal tube. Tests were run at a pressure of 0.6 ㎫ and in the ranges of heat flux 5~50 ㎾/㎡, vapor quality 0~100 percent and mass velocity of 150~600 ㎏/㎡s. Generally, the two-phase frictional multiplier is used to predict the frictional pressure drop during the two-phase flow boiling. The obtained results have been compared to the existing various Correlations for the two-phase multiplier. Also, the frictional pressure drop was compared to a few available Correlations; The Lockhart-Martinelli Correlation considerally overpredicted the frictional pressure drop data for mixture as well as pure components in the entire mass velocity ranges employed in the present study, while the Chisholm Correlation underpredicted the present data. The Friedel Correlation was found to satisfactorily correlate the frictional pressure drop data except for a low quality region.