Thermal and exergy analysis for evaluation and optimization of performance of cooling towers for fresh water and seawater

In this study, thermal, exergetic analysis and performance evaluation of seawater and fresh wet cooling tower and the effect of parameters on its performance is investigated. With using of energy and mass balance equations, experimental results, a mathematical model and EES code developed. Due to lack of fresh water, seawater cooling is interesting choice for future of cooling, so the effect of seawater in the range of 1gr/kg to 60gr/kg for salinity on the performance characteristics like air efficiency, water efficiency, output water temperature of cooling tower, flow of the exergy, and the exergy efficiency with comparison with fresh water examined. Decreasing of air efficiency about 3%, increasing of water efficiency about 1.5% are some of these effects. Moreover with formation of fouling the performance of cooling tower decreased about 15% which this phenomena and its effects like increase in output water temperature and tower excess volume has been showed and also accommodate with others work. Also optimization for minimizing cost, maximizing air efficiency, and minimizing exergy destruction has been done, results showed that optimization on minimizing the exergy destruction has been satisfy both minimization of the cost and the maximization of the air efficiency, although it will not necessarily permanent for all inputs and optimizations. Validation of this work is done by comparing computational results and experimental data which showed that the model have a good accuracy.

The potential impact of Ocean Thermal Energy Conversion (OTEC) on fisheries

The commercial development of ocean thermal energy conversion (OTEC) operations will involve some environmental perturbations for which there is no precedent experience. The pumping of very large volumes of warm surface water and cold deep water and its subsequent discharge will result in the impingement, entrainment, and redistribution of biota. Additional stresses to biota will be caused by biocide usage and temperature depressions. However, the artificial upwelling of nutrients associated with the pumping of cold deep water, and the artificial reef created by an OTEC plant may have positive effects on the local environment. Although more detailed information is needed to assess the net effect of an OTEC operation on fisheries, certain assumptions and calculations are made supporting the conclusion that the potential risk to fisheries is not significant enough to deter the early development of IDEe. It will be necessary to monitor a commercial-scale plant in order to remove many of the remaining uncertainties. (PDF file contains 39 pages.)

Effect of thermal pollution on the hydrological parameters of River Jhelum (J & K)

The Buniyar hydroelectric project and the lower Jhelum Barrier at Gantamulla constructed across river Jhelum are in operation from several years. The two power stations have changed the hydrological features of the area where dam is situated. Therefore, the impact of hydroelectric projects on fishery resources of river Jhelum is a matter of great concern. The treated water from the power house is released through turbines, having cooling effect on them. The change in the hydrological parameters such as increase in temperature, depletion of oxygen etc. might have brought fishes under stress which is the main cause in decreased population of finfishes from site to site. The golden mahseer, Tor putitora which was once an abundant species in river Jhelum has disappeared due to human intervention. The prevailing water quality around hydroelectric projects is unsuitable for finfishes of river Jhelum.

Studies on thermal deffusivity [i.e. diffusivity] and conductivity of fresh and dry fish

Thermal diffusivity (α) and conductivity (K) of fresh and dry cured fish at different moisture levels were investigated by a calorimeter (regular regime) method and transient line source technique. Thermal conductivity has a linear correlation with packing density and percentage water content. K values calculated from formula method and line source technique are comparable.

Merging effects of vitamin E and C on biological factors, blood characteristics and resistance against thermal stress in rainbow trout (Onchorhyncus mykiss)

This study was conducted to assay the effects of different levels of dietary vitamins C and E on growth indices and survival and resistance against thermal stress of rainbow trout (Oncorhynchus mykiss) in pond culture of Marzan abad from December 2011 to February 2011. Seven diets were supplemented. 300 fish with the average weight of 17 g were introduced to ponds for 60 days. The results showed that the highest and the lowest weight gain were in fish fed with diet containing 50 mg/kg vitamin C and E and 0 mg/kg vitamin C and E(control) , respectively. The highest and the lowest Feed Conversion Ratio (FCR) were measured in control and diet 50 mg/kg vitamin C and E. There is a significant difference in their treatments (P<0.05). Also, the lowest and highest amount of Weight Gain (WG) were observed in (E) treatment with 165.04% and 117.5% in control, the highest and lowest Specific Growth Rate (SGR), Protein Efficiency Ratio (PER), Condition Factor (CF) was found in control and treatment 50 mg/kg vitamin C and E, respectively(P<0.05). In conclusion vitamin C and E have an important role in enhancement of growth performance and feed efficiency of rainbow trout.The highest red blood cells were found in combined treatments and which the vitamin C was added.The highest RBC were found in E treatment(1.1×104 /mm3) and the lowest one in control (P˂0.05). Counting white blood cells also confirmed highest quantity in combined treatments with (69.83×104/mm3) and the lowest one (28.83×104 /mm3) in control. In conclusion these vitamins have a significant role in blood characteristics. Meantime, the resistance against termal stress was measured at the end of 60 days by facing fishes into 5 centigrade warmer water so consentration of Cortisol and Glucose measured for this reason.The lowest cortisol amount was measured in E treatment with 188.74 ng/ml and the highest was found in control(P<0.05). There was a significant difference in blood glucose consentration of fishes in F treatment with (78.66 mg/dl) and control with 136 mg/dl as a highest one(P<0.05).

Nutrient status and thermal stratification in Lake Victoria

Worldwide, human activity in the watershed has been found to induce lake responses at various levels, including at population and ecosystem scale. Recently, Carignan and Steedman (2000) reported on disruptions of biogeochemical cycles in temperate lakes following watershed deforestation and lor wildfire and Carignan et al., (2000 a, b) concluded that water quality and aquatic biota are strongly influenced by disturbances in the watershed. Similarly, Lake Victoria is no exception as people in its catchment have exploited it for the last hundred years or more, but have now begun to understand the extent to which they have thrown the lake into disorder and how their increasing activity in the watershed have driven some environmental changes within and around the lake.

Environmental factors influencing composition, abundance and distribution of water hyacinth

Relationships between nutrient concentrations and water hyacinth biomass and composition have been studied in the shallow inshore bays of lakes Victoria, Kyoga and Albert. Additional information was obtained from Victoria Nile, Albert Nile and Kagera River. In this section, seasonal changes in nutrients and oxygen concentrations are used to explain changes in water hyacinth composition, biomass and distribution in Lake Victoria. Lake Victoria is of particular interest because it experienced strong hyacinth infestations in 1995, a sink in 1998 and resurgence in 2001. The lake has also been extensively sampled and provides time series data in nutrient, oxygen, mixing and thermal stratification which provide an opportunity to relate water hyacinth distribution and biomass to environmental factors. The possible origins and impacts of nutrient loads into Lake Victoria are also discussed in relation to water hyacinth proliferation and distribution especially in relation to known 'hot-spots'.