Issue with Heat Transfer Simulation Results in WINDOW

[吕潇洋]

Dear Program Development Team for WINDOW,

I'm a South China University of Technology student who has used the software WINDOW7.7.1.0. However, today I found something wrong with calculating the heating transfer coefficient. Our lab developed a new material for windows. After testing the necessary parameters for the material, we input the data into the software for calculation. We then used a similar glass from the software’s library for heat transfer performance calculations. However, we noticed a significant discrepancy between the results of the new material and those obtained from the library glass, whose correlation indicators for the heat transfer coefficient are similar, including thickness, thermal conductivity, and surface emissivity. Please refer to the figure below for more details (I don't know why I can't upload the picture, so please click the link https://i.postimg.cc/t4hRsKNy/1.png).

Given the substantial difference in values, we are wondering if there might be an underlying issue with the software’s calculation model or a potential mismatch in the input parameters.

Could you kindly assist us in investigating this matter further? We would greatly appreciate any insights or suggestions you might have on how to address this discrepancy.

Thank you for your time and support. I look forward to your response.

Best regards,

​Yours sincerely Xiaoyang Lv

State Key Laboratory of Subtropical Building and Urban Science

South China University of Technology

[D. Charlie Curcija]

Hi 吕潇洋,

The reason for discrepancy in U-factor results is that T_IR for the glass that you created is non-zero (T_IR=0.17). That is why there is such a difference. If T_IR=0, then results are within the third decimal point.

Best,

Charlie

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D. Charlie Curcija, Ph.D.                              Tel: (510) 495-2602

Lawrence Berkeley National Laboratory         Fax: (510) 486-4089

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[Robin Mitchell]

The glass layer you are using has a non-zero T_IR 

That is why the results are different. 

If T_IR is set to zero, then the results are within the third decimal point. 

Robin

On Thu, Jan 2, 2025 at 6:14 PM 吕潇洋 <tose...@gmail.com> wrote:

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Robin Mitchell

Building Technology and Urban Systems Division
Energy Technologies Area
Lawrence Berkeley National Laboratory

[吕潇洋]

Thank you very much for your helpful answer. And I have a new question about this.  What is the wavelength range considered for the parameter T_IR?    

I'm looking forward to hearing back from you. Thanks.

Best,

Xiaoyang

[Jacob C. Jonsson]

On 1/9/2025 10:59 PM, 吕潇洋 wrote:
> Thank you very much for your helpful answer. And I have a new question
> about this. What is the wavelength range considered for the parameter T_IR?
> I'm looking forward to hearing back from you. Thanks.

TIR is represents the transmittance in the same range as the
thermal emissivity which as a minimum is measured in the
range 5000-25000 nm.

Best,
Jacob