Showing 5 results for Evaporator
Volume 7, Issue 1 (11-2008)
Abstract
In the present work, investigation on flow boiling heat transfer of R-134a inside a horizontal tube and also the tubes with coiled wire inserts has been done experimentally. The experimental setup which was used in this investigation was a well instrumented vapor compression refrigeration system. This set-up consists a test evaporator which all the experiments were carried out on it. Refrigerant which flows inside the tube of test evaporator is electrically heated by the coils around it. The evaporator tube is a copper tube with 7.5 mm internal diameter. The range of some operating parameters are: refrigerant mass velocities 54-136 kg/m2s, vapor qualities 0.2-1.0 and heat fluxes 2-6 kW/m2. The empirical data were collected for plain tube and tubes with seven different coiled wire inserts (different coil pitches and different wire diameters). The results show that the insertion of a helically coiled wire inside the evaporator tube increases the heat transfer coefficient by as much as 83% above the plain tube values on a nominal area basis. An empirical correlation was developed to predict the heat transfer coefficient during flow boiling of R-134a inside horizontal coiled wire inserted tubes.
Mohammad. Ali. Akhavan-Behabadi, Hamid. Ramezanzadeh,
Volume 8, Issue 1 (10-2008)
Abstract
Abstract
In the present work, investigation on flow boiling heat transfer of R-134a inside a horizontal tube and also the tubes with coiled wire inserts has been done experimentally. The experimental setup which was used in this investigation was a well instrumented vapor compression refrigeration system. This set-up consists a test evaporator which all the experiments were carried out on it. Refrigerant which flows inside the tube of test evaporator is electrically heated by the coils around it. The evaporator tube is a copper tube with 7.5 mm internal diameter. The range of some operating parameters are: refrigerant mass velocities 54-136 kg/m2s, vapor qualities 0.2-1.0 and heat fluxes 2-6 kW/m2. The empirical data were collected for plain tube and tubes with seven different coiled wire inserts (different coil pitches and different wire diameters). The results show that the insertion of a helically coiled wire inside the evaporator tube increases the heat transfer coefficient by as much as 83% above the plain tube values on a nominal area basis. An empirical correlation was developed to predict the heat transfer coefficient during flow boiling of R-134a inside horizontal coiled wire inserted tubes.
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Volume 13, Issue 15 (3-2014)
Abstract
Developing the high performance electrical devices requires high capacity heat transfer manners, which could be the pulsating heat pipes (PHPs). PHPs have a better performance in compare with conventional heat pipes (HPs), besides, they can be used to improve cooling systems for electrical devices, in future. There are some other applications for PHPs in other industries as heat transfer converters, either. The effect of the evaporator’s length on the PHPs’ performance is investigated experimentally by hiring a five turns PHPs and ferrofluid as set-up and working nanofluid, respectively. The results show that PHPs’ performance is enhanced by increasing the evaporator’s length.
B. Habibnezhad Ledari, M. Sabzpooshani,
Volume 20, Issue 4 (4-2020)
Abstract
The heat pipe is an efficient heat transfer device and can transfer large amounts of heat with a small temperature difference between the hot and cold sources quickly. In the present study, a two-dimensional numerical simulation method was used to analyze the thermal performance of heat pipes with double-ended cooling with the middle evaporator and to investigate the effect of operating conditions, wick and retaining chamber characteristics on it. The governing equations were discretized by ANSYS Fluent software and then solved using suitable boundary conditions. The wall temperature profile of the heat pipe was obtained. Then, to validate the results and to investigate the effect of using two condensers on the thermal resistance of the heat pipes, an experimental apparatus was used. Numerical results were compared with the valid numerical and experimental results that had very good and acceptable accordance. The results showed that the heat pipes with double-ended cooling with a middle evaporator had a lower thermal resistance than conventional heat pipes. The amount of thermal resistance increased with increasing the thickness and porosity of the wick. However, increasing the evaporators and condensers length, as well as increasing the thickness and internal diameter of the retaining chamber, reduced the thermal resistance. The results also showed that the heat pipes, which the materials with higher thermal conductivity were used in their wick and retaining chamber's manufacturing, had a lower thermal resistance. Finally, it was found that the increase of thermal power had no significant effect on the thermal resistance.
Volume 23, Issue 2 (3-2021)
Abstract
This study was conducted to evaluate the efficiency of Microwave-Assisted Vacuum Evaporation (MAVE) and Microwave-Assisted Evaporation (MAE) techniques for production of barberry juice concentrate in comparison to the conventional evaporation techniques. The barberry juice was concentrated by two different methods (indirect heating and the microwave evaporation under pressures of 100 and 30 kPa) to reach 60 °Brix. The results showed that the evaporation rates of MAVE and MAE methods were, respectively, 48.86 and 48.27% higher than indirect heating. The minimum changes in color parameters of barberry juice concentrate (L*, a*, b*, ΔE) were observed for vacuum-microwave evaporation. In addition, applying this method could better preserve anthocyanin content, antioxidant activity, and total phenol content of barberry juice compared to the conventional method.
