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Abstract
This thesis is concerned with numerical modelling of flow distribution in a minichannel evaporator for airconditioning. The study investigates the impact of nonuniform airflow and nonuniform distribution of the liquid and vapour phases in the inlet manifold on the refrigerant mass flow distribution and on the cooling capacity of the evaporator. A one dimensional, steady state model of a minichannel evaporator is used for the study.
An evaporator consisting of two multiport minichannels in parallel is used as a test case and two different refrigerants, R134a and R744 (CO2), are applied in the numerical experiments using the test case evaporator.
The results show that the reduction in cooling capacity due to nonuniform airflow and nonuniform liquid and vapour distribution is generally larger when using R134a than when using CO2 as refrigerant. Comparing the capacity reductions with reductions of the area covered by refrigerant in a twophase condition shows that the capacity decreases significantly more than the twophase area when imposing a nonuniform airflow. On the other
hand the reductions in capacity and in twophase area are almost equal when imposing a nonuniform distribution of the liquid and vapour in the inlet manifold.
Combining nonuniform airflow and nonuniform liquid and vapour distribution shows that a nonuniform airflow distribution to some degree can be compensated by a suitable liquid and vapour distribution. Controlling the
superheat out of the individual channels to be equal, results in a cooling capacity very close to the optimum.
A sensitivity study considering parameter changes shows that the course of the pressure gradient in the channel is significant, considering the magnitude of the capacity reductions due to nonuniform liquid and vapour distribution and nonuniform airflow. It is found that a large pressure gradient in the first part of the channel is beneficial.
Original language  English 

Place of Publication  Kgs. Lyngby, Denmark 

Publisher  Technical University of Denmark 
Number of pages  196 
ISBN (Print)  9788790416270 
Publication status  Published  Sep 2010 
Series  DCAMM Special Report 

Number  S114 
ISSN  09031685 
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Dive into the research topics of 'Modelling refrigerant distribution in minichannel evaporators'. Together they form a unique fingerprint.Projects
 1 Finished

Analyse og optimering af energisystemer baseret på en kombination af termodynamiske og fluidmekaniske beregningsmetoder
Markussen, W. B., Elmegaard, B., Hansen, M. O. L., Jakobsen, A., Sørensen, J. N., Thybo, C., Carlsen, H. & Palm, B.
01/06/2006 → 29/09/2010
Project: PhD