![]() Previously, the code was used for the calculation of water and steam two-phase flows in nuclear steam generators and for the prediction of critical heat flux in pool boiling. The mass and momentum balance equations are written and numerically solved for each phase, while the gas-liquid interfacial transfer processes are calculated with the application of corresponding empirical closure laws. The applied modelling approach assumes that the liquid and gas phase are interpenetrating media in space. In this presented study, the refrigerant two-phase flow in the headers of compact heat exchangers is numerically simulated and analysed with an “in-house” code that is based on the Computational Multi Fluid Dynamics (CMFD) method. A positive effect of the introduction of flow restrictions in the parallel pipes is presented in. The improvement was also achieved with the intrusion of evaporator channels into the header. A solution with insertions of throttle plates within the header is shown in. An atomization orifice and a splashing grid at the header inlet is presented in. A variation of a branched inlet header was presented in. Solutions were proposed for the problem of header two-phase flow maldistribution. In a commercial CFD code is used for three-dimensional simulations of two-phase flows in the header. The one-dimensional analytical model of gas-liquid two-phase distribution from the header towards parallel pipes is presented in. Due to its complexity, the problem of two-phase maldistribution from the header has been less investigated analytically or numerically with Computational Fluid Dynamics (CFD) approach. The experimental results show that two-phase maldistribution in the header is influenced by a number of conditions, such as headers’ position in respect to gravity action, headers’ length and inner diameter, orientation and a number of parallel evaporating channels, two-phase mixture velocities and qualities at the header inlet, etc. The investigation of uneven feeding of horizontal evaporating channels from vertical headers is presented in. ![]() Uneven liquid and vapour phase distributions both to upward and downward vertical channels are reported. Results of stratified liquid and vapour flow in horizontal headers are presented in. The maldistribution of the two-phase mixture from the header into the parallel channels has been a topic of extensive experimental investigations. Channels with a lower inlet liquid flow rate are dried-out and the hotter outside air stream could not be effectively cooled only by the remaining refrigerant vapour flow. The cause of this problem is uneven feeding of the evaporator’s parallel channels with the refrigerant liquid phase from the two-phase mixture stream in the header. Under medium operating conditions, temperature stratification in the air stream at the exit of the evaporator is observed, which might lead to passengers’ discomfort. ![]() N Seeds, in Vehicle Thermal Management Systems Conference Proceedings (VTMS11), 2013 1 IntroductionĪutomotive air conditioning systems operate under variable loads in order to provide passengers’ comfort under wide outside temperature conditions. Refrigerant maldistribution in an evaporator of automotive air conditioning system: investigation and a design improvement by numerical simulations
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