• Asian-Australasian Journal of Animal Sciences
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• v.11 no.3
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• pp.293-299
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• 1998

This study was undertaken to measure the concentrations of estradiol-$17{\beta}$, progesterone and testosterone, and to study their relationship with each other and with follicular size in individual buffalo ovarian follicles categorized as small (4 to 5 mm diameter), medium (6 to 9 mm diameter) and large (${\geq}10mm$ diameter). Steroid hormone concentrations varied markedly within follicles of each size category. Estradiol-$17{\beta}$ concentrations (pmol/ml) were positively related to follicular diameter (R = 0.34, n = 308, p < 0.001) and were significantly higher (p < 0.001) in large (1$118.46{\pm}30.25$), compared to those in medium follicles ($50.32{\pm}8.29$) which, in turn were significantly higher (p < 0.001) than those in small follicles ($19.70{\pm}$5.57). Progesterone and testosterone concentrations (pmol/ml) were not related to follicular diameter and were not different among small ($330.99{\pm}27.32$ and $17.68{\pm}2.44$ respectively), medium ($384.84{\pm}26.20$ and $36.47{\pm}4.55$, respectively) and large follicles ($253.25{\pm}32.23$ and $22.57{\pm}4.48$, respectively). Estradiol-$17{\beta}$ and progesterone concentrations were positively related (R = 0.39, n = 47, p < 0.01) in small, unrelated in medium and negatively related in large follicles (R = -0.59, n = 23, p < 0.01). There was no relationship between estradiol-$17{\beta}$ and testosterone concentrations in follicles of all the three size categories. Progesterone and testosterone concentrations were positively related in large follicles (R = 0.57, n = 18, p < 0.02). There was no relationship between the two hormones in small and medium sized follicles. When the follicles with estradiol-$17{\beta}$/progesterone molar ratios of > 1.00 were considered non-atretic, and the rest at different stages of atresia, 197/208(95%) follicles were found to be atretic.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.7
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• pp.649-658
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• 2005

Flow condensation heat transfer coefficients (HTCs) of R22, R410, Propane (R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of $0.1\~0.9$ at mass flux of $200\~400kg/m^2s$ and heat flux of $7.3\~7.7kW/m^2$ at the saturation temperature of $40^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within $25\%$ deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than $20\%$ for all data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.163-172
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• 2003

Boiling heat transfer coefficients and pressure drops for R-22 and R-407C were measured in horizontal micro-channels. The test section is stainless steel tube, inner tube diameters are 1.8mm and 2.8mm, and the respective lengths are 1500mm and 3000mm. The range of mass flux is 300-600kg/$m^2$s and heat flux is 5-15kW/$m^2$. In this results, pressure drop increased linearly for both R-22 and R-407C with increased mass flux, but the increase of heat flux did not affect the pressure. In addition, the pressure drop was fairly increased in the high quality region rather than low quality region. In the range of low quality, the mass flux had a small affect on the heat transfer coefficients, however, in high quality region, the heat transfer coefficients increased even more with increasing mass flux. Under the low quality region and low mass flux, the heat transfer coefficients increased with increasing heat flux densities. The effects of inner tube diameter were clearly observed. Namely, the measured pressure drop inside inner tube diameter 1.8 mm is higher than 2.8 mm with increasing the mass flux and heat flux. Also, the measured local heat transfer coefficient inside inner tube diameter 1.8 mm is higher than 2.8 mm in the range of high qualities. The experimental data for R-407C compared with proposed correlation using pure refrigerant. The experimental data for R-407C was more decreased than the proposed correlation for pure refrigerant up to 50% or more.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.249-255
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• 2005

Flow condensation heat transfer coefficients(HTCs) of R22, R4IO, Propane(R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53 m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of 0.1 ${\sim}$ 0.9 at mass flux of $200{\sim}400$ $kg/m^2s$ and heat flux of $7.3{\sim}7.7$ $kW/m^2$ at the saturation temperature of $4^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within 25% deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than 20% for all data.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1270-1275
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• 2004

Flow condensation heat transfer coefficients(HTCs) of R22 and R134a were measured on horizontal aluminum multi-channel tube. The experimental apparatus was composed of three main parts ; a refrigerant loop, a water loop and a water-ethylene glycol loop. The test section in the refrigerant loop was made of aluminum multi-channel tube of 1.4 mm hydraulic diameter and 0.53 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. The data scan vapor qualities $(0.1{\sim}0.9)$, mass flux ($200{\sim}400$ $kg/m^{2}s$) and heat flux ($7.3{\sim}7.7$ $kW/m^{2}$) at $40{\times}0.2^{\circ}C$ saturation temperature in small hydraulic diameter tube. It was found that some well-known previous correlations were not suitable for multichannel tube. So, It must develop new correlations for multi-channel tubes.

• Clean Technology
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• v.13 no.2
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• pp.151-158
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• 2007

An experimental study to investigate the condensing heat transfer characteristics of small diameter horizontal double pipe heat exchangers with R-22 and R-410A was performed. Experimental facility was constructed to calculate and observe HTC(heat transfer coefficients), flow patterns and pressure drop. The main components include a liquid pump, an evaporator, a condenser(test section), a sight-glass, pressure taps and measurement apparatus. Two pipes of different diameters are tested; One 5.35 mm ID 0.5 mm thick, the other 3.36 mm ID 0.7 mm thick. The mass flow rate ranged from 200 to $500\;ks/m^2{\cdot}s$ and heating capacity were form 1.0 to 2.4 kW. The flow patterns of R-22 and R-410A were observed with a high speed camera through the sight-glass. The tests revealed that HTC of R-410A was higher than that of R-22 by maximum 5%. Annular pattern was observed for the most cases but stratified flow was also detected when x<0.2. The pressure drop in 3.36 mm ID pipe was higher than that of 5.35 mm by $30{\sim}50%$. Comparing with previous correlations such as Shah, Fujii and Soliman's, Fujii' showed the best good agreement with my data with a maximum deviation of 40%.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1528-1535
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• 2009

Characteristics of R-22 and R-134a two-phase vaporization in horizontal small tubes were investigated experimentally. In order to obtain the local heat transfer coefficients, the test was ran under heat flux range of 10 to $40\;kW/m^2$, mass flux range of 200 to $600\;kg/m^2s$, saturation temperature range of 5 to $10^{\circ}C$, and quality up to 1.0. The test section, which was made of stainless steel tube and heated uniformly by applying an electric current to the tube directly, have inner tube diameters of 0.5, 1.5 and 3.0 mm, and lengths of 0.33 and 2.0 m. The effects on heat transfer coefficient of mass flux, heat flux and inner tube diameter were presented. The experimental heat transfer coefficients were compared with the predictions using existing heat transfer coefficient correlations. A new boiling heat transfer coefficient correlation based on the superposition model, with considering the laminar flow, was developed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.8
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• pp.748-755
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• 2004

Flow boiling heat transfer in small-diameter round tubes has been experimentally studied. The experimental apparatus consisted mainly of refrigerant pump, condenser, receiver, test section of a 1.67 mm inner-diameter round tube and pre-heater for control of refrigerant quality at the inlet of test section. To investigate the effect of bubble nucleation site characteristics of different tube materials, three different tubes of copper, aluminum and brass were used. The ranges of the major experimental parameters were 5∼30 ㎾/$m^2$ of the wall heat flux, 0.0∼0.9 of the inlet vapor quality and the refrigerant mass flux was fixed at 600 kg/$m^2$s. The experimental results showed that the flow boiling heat transfer coefficients in small tubes were affected only by heat flux, but independent of mass flux and vapor quality. The effect of tube material on flow boiling heat transfer was observed small.

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.120-120
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• 2004

• Clean Technology
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• v.14 no.1
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• pp.53-60
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• 2008

The condensation heat transfer coefficients and pressure drops of hydrocarbon refrigerants (R-290 and R-600a) and hydrochlorofluorocarbon (HCFC) refrigerants were measured in the two horizontal double pipe heat exchangers with inner diameters of 10.07 mm and 5.80 mm at a mass flux of $35.5{\sim}210.4\;kg/m^2s$ and the condensation temperature of $40^{\circ}C$. The average condensation heat transfer coefficients of hydrocarbon refrigerants were higher than that of HCFC refrigerant(R-22). The pressure drop had a magnitude in the order of R-600a > R-290 > R-22. The pressure drops in the tubes with inner diameter of 10.07 mm were approximately $6{\sim}15%$, $9.8{\sim}12.5%$ and $2.1{\sim}4.6%$ higher for R-600a, R-290 and R-22, respectively, than those with inner diameter of 5.80 mm. The condensation heat transfer coefficients were compared with the published experimental data, and showed the best agreement with Haraguchi et al.'s correlation.