An evaporator device configured to be in thermal communication with a heat source, the evaporation device comprising: a chamber comprising an inlet, an outlet, and a surface, wherein said inlet is configured to direct a liquid coolant into said chamber and said outlet is configured to direct a vapor coolant away from said chamber, and wherein said surface is in thermal communication with said liquid coolant or said vapor coolant; and a porous unit disposed adjacent to said surface of the chamber and in direct contact therewith, wherein said porous unit is configured to (i) absorb said liquid coolant, (ii) bring said liquid coolant into thermal communication with said surface of the chamber to permit heat to flow from the heat source to said liquid coolant, (iii) subject said liquid coolant to a phase transition to a vapor coolant, and (iv) direct said vapor coolant away from said surface of the chamber by the porous unit to cool the heat source, wherein: - said surface of the chamber and said porous unit are of different materials, and are configured such that vapor nucleation sites form at an interface between said surface of the chamber and said porous unit, specifically at locations in which the porous unit contacts the surface of the chamber; and - said porous unit is thermally insulating having a thermal conductivity of less than or equal to 1 watt per meter-Kelvin (W/m-k), which is less than a thermal conductivity of said surface of the chamber. a chamber comprising an inlet, an outlet, and a surface, wherein said inlet is configured to direct a liquid coolant into said chamber and said outlet is configured to direct a vapor coolant away from said chamber, and wherein said surface is in thermal communication with said liquid coolant or said vapor coolant; and a porous unit disposed adjacent to said surface of the chamber and in direct contact therewith, wherein said porous unit is configured to (i) absorb said liquid coolant, (ii) bring said liquid coolant into thermal communication with said surface of the chamber to permit heat to flow from the heat source to said liquid coolant, (iii) subject said liquid coolant to a phase transition to a vapor coolant, and (iv) direct said vapor coolant away from said surface of the chamber by the porous unit to cool the heat source, wherein: - said surface of the chamber and said porous unit are of different materials, and are configured such that vapor nucleation sites form at an interface between said surface of the chamber and said porous unit, specifically at locations in which the porous unit contacts the surface of the chamber; and - said porous unit is thermally insulating having a thermal conductivity of less than or equal to 1 watt per meter-Kelvin (W/m-k), which is less than a thermal conductivity of said surface of the chamber. - said surface of the chamber and said porous unit are of different materials, and are configured such that vapor nucleation sites form at an interface between said surface of the chamber and said porous unit, specifically at locations in which the porous unit contacts the surface of the chamber; and - said porous unit is thermally insulating having a thermal conductivity of less than or equal to 1 watt per meter-Kelvin (W/m-k), which is less than a thermal conductivity of said surface of the chamber.