Les caloducs et les chambres à vapeur (CV) sont largement utilisés dans les produits électroniques de forte puissance ou à haute intégration. Correctement utilisés, ils peuvent être considérés comme des composants à très haute conductivité thermique. On comprend aisément que les caloducs et les CV permettent d'éliminer efficacement la résistance thermique de diffusion.
Mots clés
Caloduc
Chambre à vapeur
Contenu de l'article
The most common application example of heat pipe is embedded in the heat sink, the heat of the chip fully spread on the radiator substrate or fin. When the heat emitted by the chip is transferred to the radiator through the heat-conducting interface material, the heat can be transmitted along the heat pipe with very low thermal resistance due to the high thermal conductivity of the heat pipe. In this case, the heat pipe is connected to the radiator fin, so that the heat can be more effectively dissipated through the radiator into the air. For the heat sink embedded only in the substrate, when the heating area of the chip is relatively small, it is directly transferred to the substrate of the radiator, which will make the temperature distribution of the substrate have a large non-uniformity. After the addition of heat pipes, due to the high thermal conductivity of heat pipes, it can effectively reduce the uneven temperature and improve the heat dissipation efficiency of the heat sink.
Heat pipe and VC have high equivalent thermal conductivity because their internal heat transfer mechanism is phase transformation heat. From the range of surface heat transfer coefficient, it can be seen that the phase transformation heat is the most efficient convective heat transfer. In heat pipe or VC, boiling heat transfer is carried out in the evaporation section, and steam condensation is carried out in the condensation section.
The most important performance indexes of heat pipe and VC are the maximum heat transfer Qmax, thermal resistance R and starting temperature T0. Defined respectively as follows: maximum heat transfer rate Qmax: the calorific value of Qmax value equal to the following situation: heat pipe evaporation or VC joint calorific value of Q fever source, the measured temperature difference between evaporation and condensation within the prescribed scope (usually used in engineering 5 ℃ as decision criteria), the unit is W. thermal resistance R: when heat transfer size of Q, the actual measured the temperature difference between the evaporator and condenser Δ T, thermal resistance value is Δ T/Q, the unit is ℃ / W or K/W.
Starting temperature T0: The heat pipe is a process of evaporation and condensation. But the evaporation and condensation of fluid must occur under certain temperature and pressure conditions. Starting temperature T0 refers to the minimum temperature required for the formation of phase transformation heat cycle in the heat pipe or VC cavity.
There are many factors affecting the performance of heat pipe and VC, and the mechanism analysis needs to clarify the heat transfer process in the cavity. When the evaporation section of the heat pipe is heated, the liquid in the suction core inside the evaporation section evaporates, and the pressure here increases, and the vapor transfers to the condensing section under the action of pressure difference. When the gas is transferred to the condensate section, it is condensed into a liquid. The condensed liquid is transferred to the evaporation section through capillary force in the suction core, forming a cycle. As follows:
R1 : résistance au transfert de chaleur (convectif) entre la source de chaleur et la paroi extérieure de la section d'évaporation
R2 : résistance radiale à la conduction thermique de la paroi de la section d'évaporation.
R3 : résistance de conductivité thermique (radiale) du noyau d'aspiration de la section d'évaporation
R4 : résistance thermique d'échange de chaleur d'évaporation sur la surface interne de la section d'évaporation
R5 : résistance thermique du flux axial de vapeur
R6 : résistance thermique de l'échange de chaleur de condensation sur la surface intérieure de la section de condensation
R7 : résistance de conductivité thermique du noyau d'aspiration de la section de condensation
R8 : résistance de conductivité thermique de la paroi du tube de la section de condensation
R9 : résistance au transfert de chaleur (convection) de la surface extérieure de la paroi de la source froide et de la section de condensation R10 : résistance thermique axiale de la paroi du tube et du noyau d'aspiration
