3 replies to this topic

[Stumped Student]

Hi everyone,

I am a Mechanical Engineering student studying Heat Transfer as part of my degree in the UK but am struggling with a few parts to questions and was wondering if anyone could point me in the right direction.

The question is

In a computer chip the silicon substrate is 40 mm square and is enclosed in a plastic case 1.5 mm thick. Components on the surface of the substrate generate heat, and their maximum temperature is to be 80 °C when the upper face of the chip is being cooled by an air flow at 27 °C and 0.3 m/s. Heat transfer from the lower face of the chip is negligible. Thermal conductivity of the case plastic is 1.0 W/m K.

I must find the following

(i) Determine whether the air flow is laminar or turbulent;

(ii) Calculate the heat transfer coefficient on the surface of the chip;

(iii) Calculate the maximum allowable heat generation rate in the components

The first problem I have is deciding on whether to treat this as a flat plate or not, if not which formula do I use to solve (i)

I know this is a lot for a first question but am struggling with this, if anyone could recommend any good text books that explain problems like these I would be very grateful.

Thanks in advance

Andy

[ankur2061]

Andy,

Yours is a typical convective heat transfer problem with air as the convection medium. Since you are supposed to do your own assignment the best I am going to do is provide text book references for you. You may refer the following books to get your answer:

1. Process Heat Transfer by D.Q. Kern

2. Heat ransfer by J. P. Holman (specifically used in the mechanical engineering curriculum for heat transfer)

3. A Heat Transfer Textbook by John H. Lienhard IV / V

Hope this helps.

Regards,
Ankur

[Stumped Student]

Hello Ankur,

Many thanks for your recommendation I shall get a copy.

[breizh]

Hi ,

Let you consider this resource :
http://www.nzifst.or....htm#overplanes

As Ankur suggested let you get a copy of Process Heat transfer (KERN).

Hope this helps
Breizh