Heating/cooling circuit designed to transfer heat from a hot body to a cold body using a two-phase fluid as the working fluid, the circuit comprising an evaporator device adapted to receive heat from the hot body, a condenser device adapted to transmit heat to the cold body, a first conduit through which the working fluid, in vapour phase, flows from the evaporator device to the condenser device, and a second conduit through which the working fluid, in liquid phase, flows from the condenser device to the evaporator device, wherein the evaporator device comprises a first evaporator portion, which is in fluid communication with the second conduit and acts as a reservoir or compensation chamber containing the working fluid in liquid phase, a second evaporator portion, which is in fluid communication with the first conduit and contains the working fluid in vapour phase, and a porous wick arranged between the first and second evaporator portions (18, 22) in such a manner that the working fluid moves by capillarity from the first evaporator portion to the second evaporator portion through the porous wick, characterized in that it further comprises at least one first thermal expansion valve placed upstream of the evaporator device and at least one first thermal expansion valve placed downstream of the evaporator device, said first thermal expansion valves (30, 32) being sensitive to the temperature of the working fluid through the evaporator device and being movable between a closed position, in which they interrupt the flow of the working fluid along the circuit when the temperature of the working fluid sensed by them is lower than a first threshold value, and an open position, in which they adjust the flow of the working fluid along the circuit depending on the temperature of the working fluid sensed by them, when said temperature is higher than said first threshold value, and at least one second thermal expansion valve placed upstream of the condenser device and at least one second thermal expansion valve placed downstream of the condenser device, said second thermal expansion valves (34, 36) being sensitive to the temperature of the working fluid through the condenser device and being movable between a closed position, in which they interrupt the flow of the working fluid along the circuit when the temperature of the working fluid sensed by them is higher than a second threshold value less than the first threshold value, and an open position, in which they adjust the flow of the working fluid along the circuit depending on the temperature of the working fluid sensed by them, when said temperature is lower than said second threshold value. at least one first thermal expansion valve placed upstream of the evaporator device and at least one first thermal expansion valve placed downstream of the evaporator device, said first thermal expansion valves (30, 32) being sensitive to the temperature of the working fluid through the evaporator device and being movable between a closed position, in which they interrupt the flow of the working fluid along the circuit when the temperature of the working fluid sensed by them is lower than a first threshold value, and an open position, in which they adjust the flow of the working fluid along the circuit depending on the temperature of the working fluid sensed by them, when said temperature is higher than said first threshold value, and at least one second thermal expansion valve placed upstream of the condenser device and at least one second thermal expansion valve placed downstream of the condenser device, said second thermal expansion valves (34, 36) being sensitive to the temperature of the working fluid through the condenser device and being movable between a closed position, in which they interrupt the flow of the working fluid along the circuit when the temperature of the working fluid sensed by them is higher than a second threshold value less than the first threshold value, and an open position, in which they adjust the flow of the working fluid along the circuit depending on the temperature of the working fluid sensed by them, when said temperature is lower than said second threshold value.