a heat dissipating system includes : a heat - absorbing unit having at least one cavity body adapted to contact a heat source , and a working fluid received in the cavity body ; a condenser to condense the working fluid ; and a tubing unit connected fluidly to the condenser and the heat - absorbing unit . the working fluid flows through the tubing unit to circulate from the condenser to the heat - absorbing unit by gravity and from the heat - absorbing unit to the condenser by natural convection . the tubing unit forms a closed circulating loop with the heat - absorbing unit and the condenser .