Sharif Digital Repository

Although evaporative coolers consume much lower electricity than the vapor compression systems, they are not applicable in humid climates. Combination of desiccant wheels and evaporative coolers, known as desiccant-based evaporative cooling systems, allows evaporative coolers to be used in humid climates, which provide significant energy and environmental advantages with respect to vapor compression systems. However, one of the main disadvantages of evaporative cooling is the high water. Regarding the global water crisis, a cooling system which saves both water and energy will be an attractive alternative to the current cooling systems. To this aim, this paper presents a novel... 

Desiccant-based evaporative cooling systems are considered as an energy efficient alternative to conventional vapor compression systems in humid climates. A novel hybrid desiccant-based ejector cooling (hybrid DEC) system is here presented to utilize low grade heat. In order to evaluate the system performance under subtropical humid climates, a dynamic hourly simulation of the system is performed for a typical building in Sydney. The results indicate that the hybrid DEC system is able to provide comfort conditions in subtropical and humid climates. Hybrid DEC system has a significant higher coefficient of performance compared to the conventional vapor compression system resulting to 84%... 

Nowadays, one of the most important challenges in developing greenhouses is meeting their energy demand. The other challenge is the high water consumption of evaporative-cooling systems in arid and semi-arid regions. In this study, a integrated dynamic model is developed to determine the greenhouse relative humidity, carbon dioxide, and temperature, considering transpiration. The model is applied to a greenhouse utilizing a ground to air heat transfer system, located in the Alborz province of Iran and the results are validated with experimental data. Energy and water performance of the greenhouse are evaluated for the case study greenhouse. Then, the model is applied to a greenhouse (similar... 

The gas turbine (GT) is known to feature low capital cost to power ratio, high flexibility, high reliability without complexity, short delivery time, early commissioning and commercial operation and fast starting-accelerating. Hence, researchers all over the world are working to increase the output power and efficiency of gas turbine cycle. One of the important techniques to increase the output power of such cycles is the compressor inlet air cooling method. The objective of this paper is to analysis the gas turbine cycle from both energy and exergy point of view. Thus, two important methods for increasing the output power, i.e. fog and media inlet air cooling systems are discussed.... 

Two new designs of wind towers were tested side by side with a conventional wind tower in the city of Yazd, Iran. All the towers were of identical dimensions. The two new designs were one with wetted column, consisting of wetted curtains hung in the tower column, and the other one with wetted surfaces, consisting of wetted evaporative cooling pads mounted at its entrance. The air temperature leaving the wind towers with evaporative cooling provisions were much lower than the air temperature leaving the conventional design, and its relative humidity much higher. The air-flow rate was reduced slightly in these new towers. It was found that the wind tower with wetted column performs better with... 

In this paper, analysis of the throughput and delay in a spectrally phase-encoded optical code-division multiple-access (OCDMA) system, using a simplified slotted packet network protocol is conducted. Steady-state throughput and average packet delay of the system are derived. In evaluating the performance of the system, only multiple access interference is considered and other sources of noise are neglected. Comparing different systems with the fixed bit rate and chip duration leads us to conclude that increasing the code length will improve the performance of networks with small average activity; but in highly active networks, decreasing the code length will result in a significant... 

A new design for heat pump integrated humidification-dehumidification (HDH-HP) desalination cycles was proposed in the current experimental study. An evaporative condenser was designed and fabricated instead of a separate humidifier, heater, and air/water-cooled condensers find in previous HDH-HP systems. Meanwhile, the air dehumidification process in this work directly occurred inside the heat pump evaporator. The effect of several operating parameters such as ambient wet-bulb temperature, spraying saline water and airflow rates, compressor speed, superheat, and evaporator saturation temperature control modes of the electronic expansion valve (EEV) on freshwater production and GOR were...