Abstract A control strategy for a machine must take care of different operation situations. A machine is typically confronted with different boundary conditions during operation. The control of this machine must find adequate settings for the actuators within the machine to adjust to each specific operation situation. In vapor compression cycles, which are used for refrigeration and heat pump machines, there are multiple actuators to adjust the cycle performance to the requirements, for example the expansion device, the compressor and possibly some actuators within the heat exchangers. An additional way to adjust a cycle to varying operation requirements is a dedicated shift of the composition in the working fluid of the cycle. Of course this option is only available to vapor compression cycles which have a mixture as a working fluid. This situation is encountered quite often nowadays as pure refrigerants, for example, are not in line with international regulations. This contribution analyses the options for control strategies of vapor compression cycles in part-load situations. In the first part of the paper, the variable speed control for the compressor, the variable speed control of the air-side ventilation fans of the evaporator and the condenser and the expansion valve are taken as possible actuators. Experimental and theoretical results are presented to show the manifold possibilities in parameter setting, of which only one setting will result in an optimal COP efficiency value. In the second part of the contribution the benefits of a possible shift in the composition of the working fluid mixture are discussed. The composition shift can be achieved during operation by means of a rectificator. This part is on a theoretical level only, so far.
Performance Control of Refrigeration Cycles by Adjustment of the Composition of the Working Fluid
2016-12-08
10 pages
Article/Chapter (Book)
Electronic Resource
English
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