Mohammad Ali Akhavan; Vahid Hejazi
Abstract
In this research, heat transfer enhancement and simultaneous effect of that on pressure drop inside condensers with twisted tape inserts are investigated. A refrigeration system is designed for attaining to maximum level of heat transfer with minimum pressure drop. The test condenser is a double pipe ...
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In this research, heat transfer enhancement and simultaneous effect of that on pressure drop inside condensers with twisted tape inserts are investigated. A refrigeration system is designed for attaining to maximum level of heat transfer with minimum pressure drop. The test condenser is a double pipe heat transformer with inner and outer diameter of 10.7mm and 12.7mm for internal pipe, respectively. The test tube’s length is 104mm. Experiments are performed for a plain tube and four tubes with twisted tape inserts with different twist ratios of 6, 9, 12 and 15. Also data are collected for mass velocities of 56.44, 69.49, 82.38, 96.52, 113.32 and 130.9kg/m2s. In conclusion, data analysis showed that insertion of twisted tapes inside tubes has increased the heat transfer and pressure drop by as much as 40% and 240% above the plain tube values on a nominal area basis, respectively.
Ali Asghar Hamidi; Asghar Sedighzadeh; Monireh Taherkhani; Ali Reza Kamizi
Abstract
In this investigation, the performance of a tower for absorption of sulphur dioxide gas into calcium carbonate solution has been studied. The trays had no downcomer and the tower itself was a scaled down pilot from industrial equipment. The industrial scale tower was used for clean up of 110000 m3/hr ...
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In this investigation, the performance of a tower for absorption of sulphur dioxide gas into calcium carbonate solution has been studied. The trays had no downcomer and the tower itself was a scaled down pilot from industrial equipment. The industrial scale tower was used for clean up of 110000 m3/hr gas using 40 m3/hr alkaline solution. The study was composed of two parts. In the first section, hydraulic experiments were carried out and the pressure drops both for dry and wet trays were measured. The measured data were in good agreement with the correlations found in literature. In the second part of the study, the effect of operating parameters such as liquid flow rate, gas flow rate, alkaline solution concentration and sulphur dioxide concentration on the separation efficiency were investigated. Overall, it has been concluded that the separation of sulphur dioxide from air in this tower is always above 80% complete and the equipment offers fairly good efficiency in all the operating conditions considered. The main operating parameters were alkaline solution flow rate 500 – 2000 Lit/hr, alkaline solution concentration 0.1 – 3%, air/sulphur dioxide flow rate 0.15 – 0.4 m3/s and sulphur dioxide concentration in inlet air 100ppm.
Mohammad Ali Akhavan Behabadi; Hossein Shokouhmand; Masoud Jamali Ashtiani; Amir Mohammadpour
Abstract
The pressure drop of refrigerant R-134a flow boiling inside a horizontal tube has been investigated experimentally. The test set-up which was used in this investigation is a well instrumented vapor compression refrigeration system. These instruments are thermocouples, flow meter, pressure gauges and ...
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The pressure drop of refrigerant R-134a flow boiling inside a horizontal tube has been investigated experimentally. The test set-up which was used in this investigation is a well instrumented vapor compression refrigeration system. These instruments are thermocouples, flow meter, pressure gauges and the pressure drop measuring apparatus. This system consisted of three electrically heated evaporators called as pre-evaporator, test evaporator and after evaporator, respectively. The empirical pressure drop data for two phase flow boiling of R-134a inside a horizontal tube of 7.5mm internal diameter has been collected. The ranges of mass velocities and vapor qualities are 54-136 kg/m2s and 0.2-1, respectively. The collected data were compared with the predicted pressure drop values by seven different correlations. Finally, a new correlation was developed to predict the pressure drop of two phase flow inside evaporators.
