Abstract
The paper presents an experimental analysis of the influence of dynamic disturbances on the size of the condensation zone of the appropriate new R1234yf environment-friendly refrigerant in circular mini-channels. Experimental tests were conducted for single minichanells placed horizontally, with an inner diameter d = {1.44; 2.30; 3.30} mm. A range of frequencies from f = 0.2 - 5 Hz of periodically generated disturbances showed an explicit and unfavourable influence on the decrease of the length of the proper condensation region. This influence reduced the efficiency of the process. A computational model was developed to calculate the length of the two-phase region under disturbance conditions. The model proposed was verified by the results of the experiment, and compliance was obtained in the range of ±25%.
Highlights
A heat exchanger known as the condenser is one of the basic components of a power system that performs a reversed thermodynamic cycle
The onset of instabilities, both static and dynamic, may cause the disturbance of distribution of sub-zones inside the condenser, including a shrinkage of the active area of proper condensation characterized by the highest heat transfer coefficient [12]
In order to determine the size of the proper condensation sub-zone for the R1234yf refrigerant for flow condensation inside minichannels under periodic dynamic instabilities, a novel model developed for the R134a and R404A refrigerants was used [12]
Summary
A heat exchanger known as the condenser is one of the basic components of a power system that performs a reversed thermodynamic cycle. The manufacturing process of the above-mentioned systems require the employment of heat exchangers (condensers and evaporators) based on channels with a hydraulic diameter significantly smaller than the socalled conventional ones. The classification of those systems has already been developed. During the condensation phase change in minichannel based systems, as well as in conventional systems, there are plenty of thermal-hydraulic, structural and operational problems Those problems include the possibility of the occurrence of unsteady working conditions induced by instabilities of internal (static) and dynamic (external) origin. There are no publications that concern those phenomena regarding new pro-ecological refrigerants that are meant as a substitutes for those being phased out
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