Thermal Energy Balance in Multicomponent Mixtures and Nonisothermal Effectiveness Factors via Coupled Heat and Mass Transfer in Porous Catalysts

2003 ◽  
pp. 727-755
Keyword(s):  
Mass Transfer ◽  
Energy Balance ◽  
Heat And Mass Transfer ◽  
Thermal Energy ◽  
Multicomponent Mixtures ◽  
Porous Catalysts ◽  
Effectiveness Factors

scholarly journals Experimental and numerical studies of heat and mass transfer in low-temperature heat accumulator with phase transformations of accumulating material

2018 ◽  
Vol 240 ◽  
pp. 01009 ◽  
Author(s):  
Valery Gorobets ◽  
Ievgen Antypov ◽  
Viktor Trokhaniak ◽  
Yurii Bohdan
Keyword(s):  
Mass Transfer ◽  
Phase Transformations ◽  
Heat And Mass Transfer ◽  
Thermal Energy ◽  
Experimental Studies ◽  
Experimental Plant ◽  
Chemical Transformations ◽  
Heat Accumulator ◽  
Tube Bundles ◽  
Melting And Crystallization

Accumulation of thermal energy is produced with the aim of storing at certain times, when there is an overabundance of this energy and its further use in other periods of time when there is a deficit thermal energy. Thermal energy storage may be carried out under heating of any material (water, solid materials etc.) or by using the phase or chemical transformation of the material (melting and crystallization processes, direct and reverse chemical reaction). Thermal accumulators with phase or chemical transformations are allowed to concentrate a large amount of energy in a relatively small volume of accumulating material. In this paper an experimental study and numerical modeling of heat and mass transfer in the heat accumulator during phase transformations of the accumulating material are presented. The experimental plant consists of a chamber filled with paraffin. In experimental studies, the changes of the temperature distribution in heat accumulating material and tube bundles have investigated. Numerical simulation of melting and solidification of heat accumulating material during the heated and cooled of tube bundles were performed. As the results of research, the basic laws of melting and crystallization processes in heat accumulator during phase transformations of heat accumulating material were determined.

Heat Transfer Design in Adsorption Refrigeration Systems for Efficient Use of Low Grade Thermal Energy

2010 ◽  
Author(s):  
R. Z. Wang ◽  
Z. Z. Xia ◽  
L. W. Wang ◽  
Z. S. Lu ◽  
S. L. Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Thermal Energy ◽  
High Performance ◽  
Low Grade ◽  
Adsorption Refrigeration ◽  
High Efficient ◽  
Sorption Systems

Adsorption refrigeration and heat pump systems have been considered as very important means for the efficient use of low grade thermal energy in the temperature range of 60–150°C. Sorption systems are merely heat exchanger based thermodynamic systems, and therefore a good design to optimize heat and mass transfer with reaction or sorption processes is very important for high performance of the systems. Studies on heat and mass transfer enhancement in adsorption beds have been done extensively. Notable techniques is whereby the adsorbent bed is fitted with finned heat exchanger embedded with adsorbent particles, or the adsorbent particles may be compressed and solidified and then coupled with finned tube or plate heat exchangers. The use of expanded graphite seems to be an effective method to improve both heat and mass transfer in the reaction bed. Studies have also shows the need to enhance the heat transfer in adsorption bed to match with the heat transfer of thermal fluids. Use of heat pipes and good thermal loop design could yield higher thermal performances of a sorption system, when coupled with adsorption beds to provide heating and cooling to the beds. A novel design with passive evaporation, known as rising film evaporation coupled with a gravity heat pipe was introduced for high cooling output. It has also been shown that heat and mass recovery in the internal sorption systems is critical, and novel arrangement of thermal fluid and refrigerant may result in high performance sorption systems. Based upon the above researches, various sorption systems have been developed, and high efficient performances have been reached. Typical sorption systems include (1) A silica gel-water adsorption water chillier with a COP about 0.55 when powered with 80°C hot water, (2) A CaCl2-ammonia adsorption refrigerator with a COP over 0.3 at −20 °C when powered with 120 °C water vapor, which has a specific cooling power about 600 W/kg-adsorbent. The above mentioned systems have shown that solid sorption systems have become market potential products, and low grade thermal energy, which is usually considered as waste heat, could be utilized to provide high grade cooling. This paper gives details of high efficient solid sorption systems recently developed, their heat transfer design, thermodynamic system coupling, and performance test results. Some examples of low grade thermal powered cooling systems are also presented.

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