Energy source

RaulMG · July 10, 2014, 11:12

Hi,

I want to add a heat flux in my outlet boundary but it is not a constant heat flux, it depends of the room temperature. Does the source coefficient option works for that?. I set the source coefficient but the program doesn´t allow me to use it without set the source value that I imagine is a constant quantity, then I can´t see the point of set both values, a constant value and a temperature dependent value that is the one I want to set. If the boundary where I want to set this heat source is an outlet, Do I still have to use the negative sign to indicate that this heat flux is going out of my domain (cooling)?

singer1812 · July 10, 2014, 12:01

I dont see what you are modeling. Adding a source at the outlet will not effect your interior results. You are cooling the flow after it leaves your domain. Is that what you want to see?

RaulMG · July 10, 2014, 13:04

I want to add a cooling source, but I´m not sure how to do this then. The only two thinks I have from the heat exchanger is the air flow rate, the inlet temperature of the air entering from the heat exchanger and the cooling heat flux per grade (W/°F) of the heat exchanger. I set the the inlet boundary with the flow rate a the given static temperature, and I set the outlet with the same flow rate and the heat flux per grade. This is run then?, how can I set the heat flux that the heat exchanger is taking out of the interior?

singer1812 · July 10, 2014, 13:07

Mass Flow inlet and outlet = not good.

Is this inlet and outlet you are talking about placed inside a larger domain you are modeling? Or are you really talking about an inlet to your domain and also an outlet to your domain?

RaulMG · July 10, 2014, 13:27

A heat exchanger take out warm air of a larger domain and introduces the same air at lower temperature, of course it has to do it at the same flow rate that´s why I use mass flow in and out. I have the temperature at which the cooler air is coming in and the heat flux per grade of temperature the heat exchanger is removing from the domain. Which is the best form of establish these parameters as boundary conditions?

singer1812 · July 10, 2014, 13:44

Ok. Model the heat exchanger as a subdomain. Use momentem source to drive your flow rate. Apply energy source to remove the heat.

If you have a closed system, and you use mass flow or velocity for both your inlet and outlet you can introduce numerical instability.

July 10, 2014, 11:12	Energy source	#1
RaulMG New Member Join Date: Jul 2014 Posts: 3 Rep Power: 11	Hi, I want to add a heat flux in my outlet boundary but it is not a constant heat flux, it depends of the room temperature. Does the source coefficient option works for that?. I set the source coefficient but the program doesn´t allow me to use it without set the source value that I imagine is a constant quantity, then I can´t see the point of set both values, a constant value and a temperature dependent value that is the one I want to set. If the boundary where I want to set this heat source is an outlet, Do I still have to use the negative sign to indicate that this heat flux is going out of my domain (cooling)?

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July 10, 2014, 12:01		#2
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	I dont see what you are modeling. Adding a source at the outlet will not effect your interior results. You are cooling the flow after it leaves your domain. Is that what you want to see?

July 10, 2014, 13:04		#3
RaulMG New Member Join Date: Jul 2014 Posts: 3 Rep Power: 11	I want to add a cooling source, but I´m not sure how to do this then. The only two thinks I have from the heat exchanger is the air flow rate, the inlet temperature of the air entering from the heat exchanger and the cooling heat flux per grade (W/°F) of the heat exchanger. I set the the inlet boundary with the flow rate a the given static temperature, and I set the outlet with the same flow rate and the heat flux per grade. This is run then?, how can I set the heat flux that the heat exchanger is taking out of the interior?

July 10, 2014, 13:07		#4
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	Mass Flow inlet and outlet = not good. Is this inlet and outlet you are talking about placed inside a larger domain you are modeling? Or are you really talking about an inlet to your domain and also an outlet to your domain?

July 10, 2014, 13:27		#5
RaulMG New Member Join Date: Jul 2014 Posts: 3 Rep Power: 11	A heat exchanger take out warm air of a larger domain and introduces the same air at lower temperature, of course it has to do it at the same flow rate that´s why I use mass flow in and out. I have the temperature at which the cooler air is coming in and the heat flux per grade of temperature the heat exchanger is removing from the domain. Which is the best form of establish these parameters as boundary conditions?

July 10, 2014, 13:44		#6
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	Ok. Model the heat exchanger as a subdomain. Use momentem source to drive your flow rate. Apply energy source to remove the heat. If you have a closed system, and you use mass flow or velocity for both your inlet and outlet you can introduce numerical instability.