Abstract: A heat exchanger, comprising at least a double shell, wherein the lower portion of the inner space of the inner shell is filled with liquid phase change medium, and at least one coiler is provided in the upper portion. The heated fluid flows in the coiler. After the downstream side pipe of the coiler is pierced through the inner shell, at least one surrounding pipe is formed in the cavity between the double shells. The bottom heat exchange plate of heat exchanger of the inner shell is located above the heat source. The cavity between the two shells forms the flue gas passage. After bottom heat exchange plate of the inner shell is heated by the heat source, the flue gas rises from the bottom of perimeter of the inner shell along the flue gas passage and the heat is transferred to the heated fluid in the surrounding pipe. The heat device using the heat exchanger according to the present invention can significantly improve the efficiency of heat utilization.

Abstract: A heat exchanger, comprising at least a double shell, wherein the lower portion of the inner space of the inner shell is filled with liquid phase change medium, and at least one coiler is provided in the upper portion. The heated fluid flows in the coiler. After the downstream side pipe of the coiler is pierced through the inner shell, at least one surrounding pipe is formed in the cavity between the double shells. The bottom heat exchange plate of heat exchanger of the inner shell is located above the heat source. The cavity between the two shells forms the flue gas passage. After bottom heat exchange plate of the inner shell is heated by the heat source, the flue gas rises from the bottom of perimeter of the inner shell along the flue gas passage and the heat is transferred to the heated fluid in the surrounding pipe. The heat device using the heat exchanger according to the present invention can significantly improve the efficiency of heat utilization.