Abstract: A high EER air conditioning apparatus with a special heat exchanger of a condensing unit having a water evaporating system composed of a plurality of thin water-holding layers of porous hydro material coated on the heat conducting surfaces of metal plates and medium coils in the exhaust air passages to provide an extra cooling efficiency to cool the medium to an extreme low temperature due to the water been evaporated by the blow of the exhaust air thereby, in which a low compression ratio compressor of low pressure will be enough to liquefy the medium in such a low temperature so as to save a large consumption power of the compressor for obtaining a high EER therefor.