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Numerical Simulations on Flow Process of Iso-butane in Non-adiabatic Capillary Tube

Author: YaoShuQiang
Tutor: ZhouShaoXiang；ZhouGuoBing
School: North China Electric Power University (Beijing)
Course: Refrigeration and Cryogenic Engineering
Keywords: Diabatic capillary Numerical Simulation R600a Isobutane
CLC: TK124
Type: Master's thesis
Year: 2011
Downloads: 39
Quote: 1
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Abstract

In small refrigeration apparatus, since the condensing temperature and the evaporation temperature changes, the cooling capacity is not large, the capillary tube in place of the expansion valve as the throttling element in a refrigeration system in order to simplify the structure, and are generally used. As early as in the 1930s, the capillary had applied to the refrigeration system. Almost the same period, the the regenerator principle is applied to the expansion of the capillary throttling process, forming a heat recovery capillary, improving the refrigeration efficiency of the refrigeration system. The starting point of this article has two aspects: environmental factors: the destruction of the atmospheric ozone layer and the greenhouse effect has become the focus. In order to protect the environment, the world's refrigerator manufacturers have considered a substitute refrigerant-CFCs. For the study of non-adiabatic capillary object: The capillary was born in the 1930s, and patented in 1942. It is a drawing process produced a hollow copper tube, an inner diameter is typically 0.5-3mm, to run the system are different in length substantially between 400 ~ 6000mm. To keep a certain degree of subcooling in order to allow the refrigerant in the capillary, usually formed in parallel to the return duct Recuperative capillary, i.e. referred to the non-adiabatic capillary. There are two modes: welding and embedded. Based on these two factors, the need to establish a mathematical model to reflect the the capillary thermodynamic and flow characteristics. Despite its simple structure, but the working fluid flow in which the process and heat transfer phenomenon is very complex. Especially for non-adiabatic capillary has yet to pipe flow more in-depth studies, theoretical formula is quite scarce. Practice, most still with a the experiment match to determine the length of the tube or flow, workload considerable. This article can only do some simple calculations inside thoughts can do something for future research reference from a valuable role. Firstly, homogeneous flow mathematical model, and partition the preparation of the simulation program, the operating characteristics analysis program to simulate the results of part of the heat exchanger state. Some parameters that affect its performance. Simulation results show that the operating characteristics of the non-adiabatic capillary adiabatic capillary, which is obvious. When the heat exchange section starts at the cold section, the refrigerant in the heat exchange section will continue cooling, undercooling is further increased so that the length of the outlet section of the capillary is also increased. If the heat exchange section begins when the two-phase section, the time, the capillary tube and the suction tube heat exchanger is quite strong, neatly re-condensed portion of the refrigerant will become subcooled liquid.

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