Efecto de la hormona de crecimiento sobre los parámetros seminales, el hemograma parcial y el nivel de testosterona en búfalos Nili Ravi

The purpose of this trial was to examine the possible effects of exogenous growth hormone (GH) on semen quality, hematological variables and serum testosterone concentration in Nili Ravi buffalo. Bulls of the treatment group (n=3) were injected with recombinant GH 500 mg in a 15 day interval for 10 consecutive weeks, while bulls of control group (n=3) received equal volume of normal saline solution. Semen samples were collected twice per week and analyzed for physiological parameters. Blood samples collected fortnightly were analyzed for red blood cells count (RBC), hemoglobin concentration (Hb), packed cell volume (PCV), mean corpuscular volume (MCV), white blood cell (WBC), neutrophils, lymphocytes, and serum testosterone levels. Data were analyzed statistically using t-test. Results indicated that GH treatment of Nili-Ravi buffaloes significantly (p<0.05) increased ejaculatory volume (8.8±0.2 vs 7.7±0.2 ml), sperm motility (72.6±0.4 vs 67.4±0.7%), mass activity (3.35±0.07 vs 2.52±0.08), sperm concentration (982.2±67.8 vs 731.9±50.5 million/ml), live sperm (80.1±0.3 vs 75.8±0.5%) and serum testosterone (4.02±0.21 vs 2.37±0.07 ng/ml) compared to control bulls. Among hematological variables, lymphocytes were increased (p<0.05), but MCV, WBC count, and neutrophils decreased (p<0.05). Hb, RBC and PCV remained unchanged. However, values of these variables were within normal ranges for buffalo bulls. In conclusion, treatment of Nili-Ravi bulls with GH improved semen quality and increased serum testosterone without ostensible adverse effects on the general state.El propósito de este ensayo fue examinar los posibles efectos de la hormona de crecimiento exógena (GH) sobre la calidad del semen, algunas variables del hemograma y la concentración de testosterona en suero de toros bubalinos Nili Ravi. Los búfalos del grupo tratado (n=3) fueron inyectados con 500 mg de somatotropina recombinante cada 15 días durante 10 semanas consecutivas, mientras que los del grupo control (n=3) recibieron igual volumen de solución fisiológica salina. Las muestras de semen fueron tomadas dos veces por semana y analizadas para evaluar los parámetros fisiológicos. Las muestras de sangre colectadas quincenalmente fueron analizadas para establecer el recuento de glóbulos rojos, la  concentración de hemoglobina, el hematocrito, el volumen corpuscular medio (MCV), recuento de glóbulos blancos (WBC), tasa de neutrófilos y linfocitos, así como los niveles séricos de testosterona. Los datos obtenidos fueron analizados estadísticamente por medio del test-t de Student. Los resultados indicaron que el tratamiento con somatotropina aumentó significativamente (p<0,05) el volumen eyaculado (8,8±0,2 versus 7,7±0,2 ml), la motilidad del semen (72,6±0,4 versus 67,4±0,7%), la actividad de masa (3,35±0,07 versus 2,52±0,08), la concentración de espermatozoides (982,2±67,8 versus 731,9±50,5 millones/ml), los espermatozoides vivos (80,1±0,3 versus 75,8±0,5%) y el nivel de testosterona sérica (4,02±0,21 versus 2,37±0,07 ng/ml), comparados con los animales controles. En el hemograma aumentaron los linfocitos (p<0,05) y disminuyeron variables como volumen corpuscular medio, recuento de leucocitos y tasa de neutrófilos (p<0,05). Hemoglobina, concentración de eritrocitos y hematocrito permanecieron inalterados. Todos los parámetros investigados se situaron dentro de los rangos normales para toros bubalinos. En conclusión, el tratamiento de búfalos Nili-Ravi con somatotropina mejoró la calidad del semen y aumentó la testosterona sérica, sin provocar ostensibles efectos adversos en el estado general de los toro

An improved non-dimensional model of wet-cooling towers

Abstract: A general non-dimensional mathematical model of cooling towers is improved by including evaporation of water. The solution still consists of adjusting the assumed straight air-saturation line to the real air-saturation data, but a new constant (H) is added as well. Two solutions are proposed and the accuracy of each method is checked against data from the literature and also compared with the original solution. The first method shows a maximum decrease of 4.4 per cent in error, whereas in the second method, the maximum error was found to be 3.3 and 6.8 per cent when the inlet air was unsaturated and saturated, respectively. Keywords: cooling tower, non-dimensional model, evaporatio

Prediction of evaporation losses in wet cooling towers

The accurate prediction of all aspects of cooling tower behavior is very important. Accurately predicting evaporation losses is significant because water in cooling towers is cooled primarily through the evaporation of a portion of the circulating water, which causes the concentration of dissolved solids and other impurities to increase. An empirical relation is developed on the basis of ASHRAE’s rule of thumb that is simple and accurate with a wide range of applicability. The predicted values are in good agreement with experimental data as well as predictions made by an accurate mathematical model

A complete model of wet cooling towers with fouling in fills

Abstract A cooling tower basically consists of three zones; namely, spray zone, packing and rain zones. In cooling towers, a significant portion of the total heat rejected may occur in the spray and rain zones. These zones are modeled and solved simultaneously using engineering equation solver (EES) software. The developed models of these zones are validated against experimental data. For the case study under consideration, the error in calculation of the tower volume is 6.5% when the spray and rain zones are neglected. This error is reduced to 3.15% and 2.65% as the spray and rain zones are incorporated in the model, respectively. Furthermore, fouling in cooling tower fills as well as its modeling strategy is explained and incorporated in the cooling tower model to study performance evaluation problems. The fouling model is presented in terms of normalized fill performance index (gF,norm) as a function of weight gain due to fouling. It is demonstrated that the model is asymptotic, which is similar to typical asymptotic fouling model used in conventional heat exchangers. � 2006 Elsevier Ltd. All rights reserved. Keywords: Cooling tower; Spray zone; Rain zone

Second-law-based performance evaluation of cooling towers and evaporative heat exchangers

Abstract In this paper, we present thermodynamic analysis of counter flow wet cooling towers and evaporative heat exchangers using both the first and second laws of thermodynamics. A parametric study is carried out to determine the variation of second-law efficiency as well as exergy destruction as a function of various input parameters such as inlet wet bulb temperature. Irreversible losses are determined by applying an exergy balance on each of the systems investigated. In this regard, an engineering equation solver (EES) program, with built-in functions for most thermodynamic and transport properties, is used. The concept of total exergy as the sum of thermomechanical and chemical parts is employed in calculating the flow exergies for air and water vapor mixtures. For the different input variables investigated, efficiencies were, almost always, seen to increase or decrease monotonically. We notice that an increase in the inlet wet bulb temperature invariably increases the second-law efficiency of all the heat exchangers. Also, it is shown that Bejan’s definition of second-law efficiency is not limited in evaluating performance. Furthermore, it is understood that the variation in the dead state does not significantly affect the overall efficiency of the system. © 2006 Elsevier Masson SAS. All rights reserved. Keywords: Exergy; Evaporative cooler; Evaporative condenser; Dead stat

Second-law-based performance evaluation of cooling towers and evaporative heat exchangers

Abstract In this paper, we present thermodynamic analysis of counter flow wet cooling towers and evaporative heat exchangers using both the first and second laws of thermodynamics. A parametric study is carried out to determine the variation of second-law efficiency as well as exergy destruction as a function of various input parameters such as inlet wet bulb temperature. Irreversible losses are determined by applying an exergy balance on each of the systems investigated. In this regard, an engineering equation solver (EES) program, with built-in functions for most thermodynamic and transport properties, is used. The concept of total exergy as the sum of thermomechanical and chemical parts is employed in calculating the flow exergies for air and water vapor mixtures. For the different input variables investigated, efficiencies were, almost always, seen to increase or decrease monotonically. We notice that an increase in the inlet wet bulb temperature invariably increases the second-law efficiency of all the heat exchangers. Also, it is shown that Bejan’s definition of second-law efficiency is not limited in evaluating performance. Furthermore, it is understood that the variation in the dead state does not significantly affect the overall efficiency of the system. © 2006 Elsevier Masson SAS. All rights reserved. Keywords: Exergy; Evaporative cooler; Evaporative condenser; Dead stat

A comprehensive design and rating study of evaporative coolers and condensers. Part II. Sensitivity analysis

Abstract Sensitivity analysis can be used to identify important model parameters, in particular, normalized sensitivity coefficients; by allowing a one-on-one comparison. Regarding design of evaporative coolers, the sensitivity analysis shows that all sensitivities are unaffected by varying the mass flow ratio and that outlet process fluid temperature is the most important factor. In rating evaporative coolers, effectiveness is found to be most sensitive to the process fluid flow rate. Also, the process fluid outlet temperature is most sensitive to the process fluid inlet temperature. For evaporative condensers, the normalized sensitivity coefficient values indicate that the condensing temperature is the most sensitive parameter and that these are not affected by the value of the mass flow ratio. For evaporative condenser design, it was seen that, for a 53% increase in the inlet relative humidity, the normalized sensitivity of the surface area increased 1.8 times in value and, for a 15 8C increase in the condenser temperature, the sensitivity increased by 3.5 times. The performance study of evaporative condensers show that, for a 72% increase in the inlet relative humidity, the normalized sensitivity coefficient for effectiveness increased 2.4 times and, for a 15 8C increase in the condenser temperature, it doubled in value. q 2005 Elsevier Ltd and IIR. All rights reserved. Keywords: Refrigeration; Air conditioning; Cooling tower; Evaporative condenser; Modelling; Research; Paramete