Patent Number: 
Section: claims

1. A heat exchanger for a passive residual heat removal system to cool a core of a nuclear reactor, the heat exchanger comprising:an emergency cooling tank in which water is received;a housing disposed inside the emergency cooling tank, the housing including an upper portion and a lower portion, wherein an exhaust port is formed in the upper portion of the housing, and through holes are formed at the lower portion of the housing; anda heat exchange tube disposed inside the housing,wherein the heat exchange tube includes a first member positioned corresponding to the upper portion of the housing and a second member positioned corresponding the lower portion of the housing, the first member being connected to a steam pipe through which steam generated from a steam generator of the nuclear reactor circulates, and a second member connected to both of the first member and a feed water pipe used to supply water to the steam generator provided in the nuclear reactor, and the first member has a shape different from that of the second member, andwherein the water is filled to a level of the lower portion of the housing and flows between the emergency cooling tank and the housing through the through holes, and air is filled above the water, so that the steam flowing the first member is air-cooled and the steam flowing the second member is water-cooled. 2. The heat exchanger of claim 1, wherein the first member includes a spiral tube, and the second member includes a straight tube. 3. The heat exchanger of claim 1, wherein the first and second members include spiral tubes, and the first member has spiral turns per length greater than those of the second member. 4. The heat exchanger of claim 1, wherein the first member includes a first spiral tube, and the second member includes a straight tube and a second spiral tube connected to the straight tube. 5. The heat exchanger of claim 4, wherein the first spiral tube has spiral turns per length greater than those of the second spiral tube. 6. The heat exchanger of claim 1, wherein the housing has a lower end. 7. The heat exchanger of claim 1, wherein a heat radiation fin is installed in the heat exchange tube.