18 May 2017
Currently, the development of hybrid and electric vehicles has been promoted. Along with this, since the impact reduction for cruising distance and the securing of the heat source are problems, changes are also required for the air conditioner. Therefore, high efficiency of the air conditioning system by improving efficiency of the heat exchanger and changing to heat pump system has become more and more necessary. However, due to frost formation of the outside heat exchanger by the use of a cold climate region, increase of pressure drop and decrease of heat transfer rate are expected to be an application difficulty of HP systems.
The objective of this study is to analyse the mechanism of frosting phenomenon in fin-less heat exchanger. This is intended to clarify the advantage in terms of frost strength and defrosting performance fin-less heat exchanger for the future candidate of heat exchanger.
We investigate basic characteristic of frost formation of the flow path between flat plate with concavity and convexity under forced convection. Test section is a flow path that is placed opposite to a flat plate having a periodic concavity and convexity groove on the surface. By using microscope and high speed VTR, we achieved a visualization of overall test section and observation of frost layer growth and frost formation are analysed by using of the VTR image. Finally, the relation between duration until incipient passage blockage and channels geometry becomes clear.