جستجوی مقالات مرتبط با کلیدواژه « خنک کننده تبخیری مستقیم » در نشریات گروه « مکانیک »

In this investigation, performance enhancement of direct evaporative cooling system using storage reservoir of cold water has been studied. The water in the reservoir is aimed to store the cold energy overnight and use it during daytime to reduce the temperature of exhaust air from cooler. In this paper, at first stage, the governing equation of above mentioned hybrid direct evaporative cooler is extracted and then, the effect of water storage reservoir mass on the temperature of exhaust air from cooler is investigated. Take a typical summer day in Tehran for example; the results indicate that the use of storage reservoir containing water with a mass of three times larger than the mass of dry air passed through cooler per hour decreases the temperature of the cooled air by 2.02℃ at 14:00 clock. The major advantages of this system are shifting the hours for the maximum and minimum cooled air temperatures towards other hours of a day (e.g., from 05:00 and 14:00 to 06:00 and 18:00, respectively) as well as reducing the cooled air temperature range from 6 to 3.5℃.

In the present paper, cooling performance of a hybrid system of air underground channel and direct evaporative cooler to provide cooling load for residential spaces was investigated in summer and its performance evaluation was studied for Tehran,Iran. The study was performed in hottest day of the year in Tehran which has hot and dry condition. At first, mathematical modeling of the hybrid system components was developed then by using the mathematical modeling, outlet air temperature distribution of any component of the proposed hybrid system was calculated. The obtained results imply that air temperature drops about 10°C in underground air channel and 6°C in direct evaporative cooler. andAccording to the obtained temperatures and thermal comfort zone, it was found that the hybrid system is capable in the hottest days of the year to provide thermal comfort for the residental occupants in Tehran. Then, by calculation of the system efficiency, it was found that the efficiency is more than 1 which indicate high performance of the hybrid system. Eventually by comparison between efficiency of the hybrid system and direct evaporative cooler it was found that efficiency of the hybrid system is 45 percent more than direct evaporative cooler. Also the system efficiency is higher than conventional mechanical systems efficiency and it is eco-friendly because of the system is passive. Thus according to present work, the proposed hybrid cooling system could be a suitable alternative for conventional HVAC systems.

A hybrid cooling system encompassing; cooling tower، cooling coil and evaporative cooler have been discussed in present study. Thereinafter، the hybrid system model is used to predict cooling potential of the system under various operational conditions. In order to have an accurate performance prediction of the hybrid cooling system، a numerical simulation was performed and the results validated using experimental measurements. The presented hybrid cooling system provides the necessary pre-cooling effects، enabling a direct evaporative cooler that cools the air even below outdoor air wet-bulb temperature. Besides، the potential of presented hybrid cooling system to provide thermal comfort in various outdoor design conditions evaluated and compared with conventional direct evaporative cooler. Numerical simulation revealed that the hybrid system complements direct evaporative cooling. Based on the simulation results، the overall cooling effectiveness of hybrid system is tangibly magnified 10%-20% and also it is able to fulfill the comfort condition in extended climate conditions rather than stand-alone direct evaporative coolers. Also in present study water loss amount of hybrid system and direct evaporative cooler were verified in various climate conditions of Iran.