A bubble cycling heat exchanger includes a closed fluid loop in contact with a heat absorbing source through a heat conducting block. The loop has a bubble generator. An expanding area for generating bubbles is installed at the loop. The loop is also formed with a radiator and a guide region from which bubbles are easily separable. The heat conducting block is connected to the heat absorbing source. Since the overheating of the heat absorbing source will cause the loop to generate bubbles by an unequilibrium formed at the guide region of the loop, the bubbles will separate from the guide region so that the liquid in the loop flows for transferring heat and so that heat is radiated by the fins or other elements of the radiator from the primary element of a computer at the heat absorbing source. The loop operates continuously until a thermal equilibrium is achieved.