A Study Of Thermal Resistance For Vapor Chamber Heat Spreader On The Performance Of Thermoelectric Module

Thermoelectric system is not being widely used due to its low efficiency which is strongly influenced by thermal design associated towards hot side.This study has focused on improving efficiency of thermoelectric system by using a vapor chamber heat spreader which has enhanced its thermal performance by providing low total thermal resistance and efficient spreading capability to distribute temperature uniformly and avoid formation of hotspot region associated with the hot side of thermoelectric modules.For this study,following research work has been carried out;1)Modeling of thermoelectric module:In this study,performance of thermoelectric module is numerically simulated using MATLAB based on correlations of Peltier effect,Joule's effect and conduction heat transfer;TEC1-12710 module with area of 40 mm x 40 mm is considered as research object with reference to cold side temperature of 290 K,temperature difference of 0 K—70 K and variable input current from 0.1A—15A;two major issues are formulated based on conduction heat losses,high temperature and thermal resistance at hot side of thermoelectric module.2)Studied the effect of vapor chamber heat spreader with hot side of thermoelectric module and developed the mathematical model of vapor chamber based on continuity equation for wick and vapor-core region and energy conservation equations for three regions of vapor chamber which are composed of wall,porous medium wick structure and vapor-core;orthotropic approach is used to obtain effective thermal conductivity of vapor chamber,spreading and conduction resistances.3)Simulation analysis:COMSOL Multiphysics is used as simulation platform for vapor chamber heat spreader based on various parameters;heat input from 80 W–400 W,convection coefficient of 100 W/m~2K—2000 W/m~2K,variable thickness and area.Analyzed and compared with conventional copper and aluminum solid metal heat conduction plates.The simulation results obtained for this study are as given;1)It is found that efficiency of thermoelectric module has robust correlation with conduction heat transfer and temperature difference.For thermal resistance less than 0.1 K/W,the performance COP will be greater than 2.40 at small input current.Similarly,for thermal resistance lies in range of 0.001—0.1 K/W the hot side temperature can be minimized to the range of 310 K—335 K.This shows that significant enhancement in COP can be achieved with low total thermal resistance and small temperature difference.2)At any input heat flux,percentage rise of temperature between bottom and top surface of vapor chamber is low as compared to conduction heat plates.For heat input of 160 W,percentage rise of temperature in copper is 48.46%whereas for aluminum is 76.76%which is greater than temperature rise of vapor chamber.This means that vapor chamber has high effective thermal conductivity which can provide low temperature difference between bottom and top surfaces.3)Total thermal resistance of vapor chamber is found in range of 0.27 K/W—0.28 K/W for heat input of80 W,160 W and 240 W.However,thermal resistance is similar for conduction heat plates on these heat inputs such as for copper is 0.326 K/W and aluminum is 0.458 K/W,which shows that vapor chamber offer17%less total thermal resistance than copper and 41%total thermal resistance less than aluminum heat conduction plates.This indicates significance of vapor chamber with low thermal resistance for enhancing performance of thermoelectric module.4)Increasing the area ratio will decrease total thermal resistance;for area of 150 mm x 150 mm vapor chamber shows total thermal resistance of 0.163 K/W whereas copper and aluminum conduction plates shows 0.266 K/W and 0.427 K/W,respectively,which means that vapor chamber can achieve 38.72%and61.82%less total thermal resistance than copper and aluminum conduction plates,respectively.This shows an importance of increasing area ratio of vapor chamber which will increase its heat spreading capability by offering lower thermal resistance.5)Lateral conductivity of vapor chamber obtained from the simulation are in the range of 1480—1944W/(mK)which indicates that temperature is distributed uniformly along the top surface and can overcome the hotspot area in comparison with copper(401 W/(mK))and aluminum(171 W/(mK))heat conduction plates.This study has revealed that using vapor chamber heat spreader with hot side of thermoelectric module can achieve 26.15—56.15%greater COP than conventional copper and aluminum heat conduction plates.This study also put forward the efficient capability of vapor chamber in terms of spreading and total resistances with high effective thermal conductivity.This proposed study will provide guidelines for design and application of vapor chamber used with thermoelectric modules.