不同材料对壳体表面温度的比较

一个密闭的壳体,内部有一定的热量. 如果采用塑料和铝挤作为外壳材料.假设表面热辐射系数一样. 壳体表面的温度有差异吗?

there should be some difference between these two different materials. i remember some testing done before for one natural convection application case. in the early stage, i used plastic material to build fixture, and thereafter, aluminium alloy used to shape its fixture. of course, these two case shared the same MLB, the only differene lied in their chassis material. as I remember, metal chassis is better than plastic one, I mean the surface temperature is lower when metal chassis is applied. but the feeling is different when you touch your finger onto the surface. it should feel worse when metal surface is used. you can build one model and do simulation in software to check out if I said is right or not.

说一下自己的看法
如果材料的表面属性差不多，那么自然对流系数是一样的。辐射能力相同，那肯定是表面温度一样。但是这个表面温度，应该是整个表面的平均值。
至于触感不同，应该是，金属的外壳，温差范围围绕相同的表面平均温度波动比较小。塑料的温差范围比较大。LZ可能刚好摸到了塑料外壳温度较低的地方。

thanks for ggliang and Rosicky sharing. actually i have done simulation for plastic and metal. metal surface temperature is very even and have no large temp gradient. but Plastic surface has big gradient.  in my case, enclosure dimension is 40mmx200mmx68mm total power is 12W. metal surface temp is 60C@ Ta=40C, Plastic is about 72C(Maximum)..
i just don't know how to analysis from heat transfer theory?/  i don't think heat transfer coefficient has large difference between METAL and non-metal.

To bertfan, I think, for metal enclosure case, the total series thermal resistance from heat source to ambient is much smaller compared to non-metal one, which will result in the smaller temperature difference between the heat source and ambient, and also the smaller Delta T between enclosure surface to ambient.

hi, Eggliang. i agree. but could you show some quantized calculation bewteen metal and non-metal?

it's easy, right? for example, we assume thermal resistance from ambient to surface is Theta_sa=6C/W, and conduction resistance is Theta-con=2C/W, and from inner surface to case is 8C/W. and for non-metal case, from ambient to enclosure surface is Theta-sa=6C/W, and conduction resistance is Theta-non=4C/W, and from inner surface to case is 8C/W. and we assume the total power is 5W, and ambient temp is 35C. so we can get below calculation:
(1) for metal enclosure:Tc=35+5*(6+2+8)=115C, and Ts=35+5*(6+2)=75C.
(2) for non-metal enclosure: Tc=35+5*(6+4+8)=125C, and Ts=35+5*(6+4)=85C.
from the above, we can see the difference from these two cases.

from thermal theory, if the two enclosure is same except for their material, the differene of their surface temperature should lie in their conduction thermal resistance. I think the convection and radiation heat tranfer should  be identical.

if you anyone have the better understanding on this problem, please share with us.