Au1 - ABSTRACT: The performance of a Double Effect...

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ABSTRACT: The performance of a Double Effect Evaporator was tested by using the water as solvent and the steam as heating medium. The steam economy in the first effect was found to be 0.120 while in the second effect was 0.969. The rates of heat transfer in the first effect and in the second effect were 58,650 and 9,735.6 (kJ/hr) respectively. So that, the overall heat transfer coefficient in the first effect was higher than that of second effect as calculated. INTRODUCTION:
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In many industrial applications, evaporation is a physical treatment in which water with high concentration of total dissolved solids is boiled up to produce salts free water vapor. A two-stage evaporation technique is employed to produce high economy of the steam. There are four commonly types of evaporators in which a non-volatile solute vaporizes a volatile solvent. Namely, they are forced circulation evaporators, natural circulation evaporators (thermosiphon), falling film evaporators, and rising film evaporators. In this experiment, the amount of heat absorbed ( q ) will be calculated in both stages, hence different heat transfer coefficient. In other words, the performance of the double effect evaporator will be tested by this transfer medium. The steam economy will be determined by knowing the total mass flow rate of the vapor in both effects. Values of enthalpies for mass and energy balance equation are obtained from literature. THEORETICAL BACKGROUND: To do a performance test for a multiple effect evaporators, the best parameter is steam economy. It is the ratio of the mass of water vapor generated to the mass of steam supplied. In this process, one kilogram of steam is condensed for each one kilogram of water evaporated. Furthermore, heat transfer is considered as a second parameter in importance. Both parameters cold be calculated from the following equations: Steam Economy : E = M v / M s (1) Heat Transfer Rate : q = U A (T s - T p ) (2) A mass balance and an energy balance are required for determining the heat transfer rate. By the assumption of saturation condition for the steam, then: q = m s λ s (3) which is a given heat to the process. On the other hand, the heat absorbed that used for partial vaporization, can be
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This note was uploaded on 12/28/2010 for the course CHEMICAL CHEM 409 taught by Professor Abdullahal-shammari during the Fall '08 term at King Fahd University of Petroleum & Minerals.

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Au1 - ABSTRACT: The performance of a Double Effect...

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