Natural draft dry cooling tower modelling

Predictions based on a numerical simulation of a natural draft dry cooling tower (NDDCT) has been compared with those obtained theoretically and experimentally. Experiments are conducted in a lab-scale NDDCT and are validated with a three-dimensional numerical simulation of the flow in and around the heat exchangers, which is modelled as a porous medium. Both vertical and horizontal arrangements of the heat exchangers are examined. The experimental, numerical and theoretical approaches lead to very close prediction for the air velocity and temperature at the exit of the cooling tower. Results of this study are expected to be useful for future work on the development of air-cooled condensers for geothermal power plants in Australia

Oxygen consumption and ammonia excretion of the searobin Prionotus punctatus (Scorpaeniformes, Triglidae) at two different temperatures

Routine oxygen consumption and ammonia excretion were measured at 20ºC and 25ºC in the searobin Prionotus punctatus collected in Ubatuba region (22º30'S), SP, Brazil, in western South Atlantic, to investigate energy expenditure and losses through metabolic processes. IndividuaIs ranging from 1.00g to 88.47g and from 1.79g to 56.50g were used in experiments at 20ºC and 25ºC, respectively. At 20ºC and 25ºC, the averages of weight-specific oxygen consumption for the weight class of 1.00 - 10.00g, common to both temperatures, were 162.46µ 39.51 µ.10z/g/h and 200.47µ 92.46 µ.10z/g/h, respectively; for the weight class of 50.01 - 60.00g these values were 112.30 µ 22.84 µ.10z/g/h and 114.60 µ 20.36 µ.10zlg/h. At 20ºC and 25ºC, the averages of weight-specific ammonia excretion for the weight class of 1.00 to 1O.00g were 1.03 µ 0.37 fJ.M/g/h and 1.21 µ 0.65 µ.M/g/h, respectively; for the weight class of 50.01 -60.00g these values were 0.68 µ 0.13 fJ.M/g/h and 0.60 µ 0.22 µ.M/g/h. The energy budget for the species was calculated at both temperatures using the experimental data and a model for marine teleosts proposed in the literature.<br>O consumo de oxigênio de rotina e a excreção de amônia de Prionotus punctatus coletados na região de Ubatuba (22º30'S), SP, Brasil, foram medidos a 20ºC e 25ºC, para avaliar os gastos e perdas de energia com os processos metabólicos. Foram utilizados indivíduos variando de 1,00g a 88,47g e de 1,79g a 56,50g, em experimentos a 20ºC e 25ºC, respectivamente. As médias de consumo específico de oxigênio a 20ºC e 25ºC para a classe de peso de 1,00 - 10,00g, comum a ambas as temperaturas, foram 162,46µ 39,51 µ.10z/g/h e 200,47 µ 92,46 µ.10z/g/h, respectivamente; para a classe de peso de 50,01 - 60,00g esses valores foram 112,30 µ 22,84 µ.10z/g/h e 114,60 µ 20,36 µ.10z/g/h. A 20ºC e 25ºC, as médias de excreção específica de amônia para a classe de peso de 1,00 a 10,00g foram 1,03 µ 0,37 e 1,21 µ 0,65 µ.M/g/h, respectivamente; para a classe de peso de 50,01 - 60,00g esses valores foram 0,68 µ 0,13 µ.M/g/h e 0,60 µ 0,22 µ.M/g/h. O orçamento energético para a espécie foi calculado para cada temperatura utilizando-se os da.dos experimentais e modelo proposto na literatura