An integral heat pipe, heat exchanger, and clamping plate. A base plate functioning as an evaporator has disposed in it a multiplicity of intersecting parallel and perpendicular internal channels extending laterally substantially across the base plate. A sintered copper thermal wick is applied to all channels. Thin-walled condenser tubes forming a condenser region are joined to the base plate at intersections of width wise and cross wise channels contained in the base plate. A multiplicity of fins extend to all condenser tubes. For heat pipe arrangements operating in horizontal configurations, all wick-lined channels within the base plate remain open. For heat pipe arrangements intended to operate in oblique or vertical configurations, horizontally extending channels vertically displaced relative to other horizontal channels are isolated from the latter by a multiplicity of plugs. The vertically isolated horizontally extending channels constrain the working fluid and its vapor to remain within a single horizontal channel and yet disperse laterally within the maximum internal dimensions of the evaporator. Condensed working fluid returning from the condenser region to the base plate and subsequently to the heated region via capillary action is cycled more rapidly through the evaporation and condensation phases, thereby increasing the efficiency of the integral heat pipe arrangement.