Abstract
Keywords - air conditioning, transient, simulation, amesim, ac loop
Abstract - To optimise the ratio 'thermal comfort / fuel consumption', the thermal management of the vehicle appeals more often than previously to the numerical simulation tools. In this area, the physical simulation of an AC loop became an unavoidable element for the car manufacturers.
By "physical simulation" we mean a set of virtual components like ducts, expansion valves, receivers, accumulators, condensers, evaporators or compressors, which can be interconnected to build a virtual AC loop under a Friendly graphical user interface like AMESIM®. This is possible if we are able to represent mathematically the physical behaviour of every component by taking into account the involved transient aspects.
The heat-exchangers models we developed are based on the finite volume method. In this way, the heat flow rate can be analysed according to the exact technology of the condenser or the evaporator. Concerning the evaporator, the developed models predict the total heat flow rate as well as the sensible/total heat flow rate ratio.
Concerning the compressor, we developed an innovatory model based on the dimensional analysis of the performance measurements concerning the mass flow rate and the discharge temperature. For the short-tube orifice model, we simply implemented an empirical model found in the literature which gives good results.
For the accumulator and receiver, we developed a special model based on the separation between liquid and vapour under the gravity effect. This model is indispensable to the calculation of mass transfer between the AC components during a transient simulation.
Applying all these models to a complete AC loop, we obtained good correlations in stabilized mode as well as in transient mode. We give here an example of results obtained with an AC loop including a fixed displacement compressor, a short-tube orifice and an accumulator.