Finding air temperature

[Complex Potential]

I'd go for the new model setup because it gives you more options to play with. When you say you are looking for the air temperature distribution 5m from the roof surface, do you mean the external air temperature? If so, I would suggest that IES may not be the most appropriate program for such a study.

To be honest, it sounds like you are trying to get to a level of detail where you should really be using some sort of CFD or finite element package like ANSYS CFX. IES is great for looking at whole building scale stuff but it is not designed to examine the fine details.

[tkc]

hi CP,

Yeah I am looking at the external air temp effect due to the change in reflectivity of the roof surface. From the results I obtained, the layer nearer to the roof has a high temp and slowly decreases as it goes further away. I did tried this on CFD (solar loading) but I do not know the exact boundary condition to input in. I was told by my supervisor that I can use IES who will auto adjust the boundary conditions and hence here I am . Anyway, for a typical solar loading model on a building to find the air temp distribution, do you have any ideas on what are the input boundary conditions? I came across a video on youtube on solar loading and I e-mail the uploader on what are the boundary conditions that he set. But he told me to register for their course instead of actually giving me the answer to my questions

In using IES, it is actually mainly for me to find out the differences in roof and ceiling temperature of a coated roof. However, I am stuck with finding which layer and which setting is the roof/ceiling temperature again. (Life is full of obstacles).

Hence, to check with you, if I use my NEW model, under surface temperature in apacheSim, which layer should be my actual roof/ceiling temperature? *Take "A" as the top layer which I drawn as roof layer and "B" as the btm layer which I drawn as ceiling layer.

Ceiling of A / Floor of A = > roof temperature?
Ceiling of B / Floor of B => ceiling temperature?

**The floor of A should have exact temperature as the ceiling of B? am I right to say this?
***What do you think I should input for my construction for the internal wall setting? concrete + plaster will do? or other materials?

[Complex Potential]

I don't have much experience with solar loadings and boundary conditions but it sounds as though your supervisor is an expert so perhaps he can help?

Anyway, I can answer your last two questions:

**The floor of A should have exact temperature as the ceiling of B? am I right to say this?
Answer - no, the surface temperatures will be different on opposite sides of the construction layer.

***What do you think I should input for my construction for the internal wall setting? concrete + plaster will do? or other materials?
Answer - It should be whatever the design team tell you it will be

[tkc]

Hi CP,

he actually doesn't know how to use fluent too

**The floor of A should have exact temperature as the ceiling of B? am I right to say this?
Answer - no, the surface temperatures will be different on opposite sides of the construction layer

=> I thought the floor of A should be the ceiling of B? I mean if I were to expand the individual room, they state the floor of A as the ceiling of B?

So they actually do not reflect the same surface? Hmmm, so do u actually mean that the surface temp is for ceiling of A, then floor of A, followed by ceiling of B and then floor of B? Such that they do not overlap each other?

If I were to draw 2 such layers, based on your experience, which surface should be the ACTUAL roof and ceiling temperature?

[Complex Potential]

Hiya

Try to think of it this way:

You have two rooms, one directly above the other. The separation between them is a horizontal plane with a construction applied which IES refers to as the "ceiling" as applied from below. The outside face of this "ceiling" construction is the "floor" of the room above whereas the inside face of this "ceiling" construction is the "underside" of the ceiling of the room below.

Between the "floor" surface and the "underside" surface there is actually a construction thickness made up of various layers as defined by your ceiling construction and IES calculates the heat transfer from one side of it to the other.

Dont forget that a normal ceiling construction from inside to outside is going to be (simplified) something like plasterboard, void, concrete, timber flooring, carpet. The surface temperature of plasterboard will obviously be quite different to carpet.

[tkc]

Hi CP,

I think I know what you meant now. However, as u mentioned there is some thickness between each room, does it refer to the height I set for my rooms?

If I drew the 2 rooms at a height of 200mm each, does the construction details which I used is inside this 200mm height that I drew? Or is the constructions details that I drawn is actually the gap between the 2 rooms?

I am quite confused on the construction actually. As I drew a height for my room at 200mm, but the materials contain 203mm of concrete + 19mm of plaster which is actually more than the height of my room already.

So does it mean that the 200mm height of room that I draw is made up of 203mm concrete + 19mm plaster, so does the concrete + plaster is the GAP between the 2 rooms?

Hope you can clarify my doubts on this! Thanks.

In addition, the initial simulation I did does look practical for the air temperature layer I am intending to find out. However, the temperature of the top surface peaks in the evening instead of the afternoon, which I am not sure why.

[Complex Potential]

Hi

I think you may benefit from reading through the ModelIT help document which details how the geometry should be defined. However, I shall answer your question here.

When it comes to room heights, you should be building from the finished floor of your room to the finished floor of the room above. The ceiling construction thickness is then applied DOWNWARDS from the highest point. In other words, you should make an allowance for the ceiling thickness when you set your room height.

If you want a visual representation of this, activate internal volumes within your model and you should see these thicknesses at surface level view within ModelIT (although not within the 3D model viewer). WARNING - Make a copy of your model before you do this because activating internal volumes can mess up your windows and doors if you have not set the thicknesses correctly.

By the way, IES also applies thicknesses for roofs and walls but in similar ways which vary slightly depending on whether the wall is internal or external.

[tkc]

hi CP,

just to check if I did not cater to the extra allowance as I just set the plan of the upper room as the max height of the lower room,will it actually affect my simulation?

In addition, how do I know the exact thickness of the ceiling? is it based on the construction materials total thickness?

Just to bring back a previous question, in my new model, which surface could be the ACTUAL surface of the actual building roof and actual building ceiling? the construction for both my CEILING and ROOF layer setting are the same.

[Complex Potential]

It's unlikely to have much impact on your model I think.

Yes the thickness of the ceiling is based upon the construction total thickness.

In vista the results will be different depending on whether you look a the "ceiling" construction from above or below. If you want the roof surface you would need to select the air "room" and then go to its floor which would be the external roof surface.

[tkc]

thanks a lot CP,

Will continue working on this research after my exams end. Currently I am preparing for my semester exams.

Greatly appreciated. Will post here again if I face any problems!