The utility mode relates to a tubular heat exchanger, belonging to the cooling and heating technical field. The plate-type (or bushing-type) heat exchanger of the prior art has the problems of no dirtresistance, no incrustant resistance, no freezing resistance, large flow resistance, complex technology, high price and the like. The heat exchanger is formed by combining a medium channel formed bya curved pipeline with another medium channel which is sleeved outside the curved pipeline and is formed by a thick straight pipeline. When medium flows in each pipeline, the heat energy of a medium can be transferred to another medium to the greatest extent. The utility model has the advantages of high heat exchanging efficiency, energy resource saving, simple manufacture, convenient use, long service life and the like. The utility model serves as a condenser or an evaporator in a cooling air-conditioning device and as an air-water or water-water heat exchanger in a heating system.