Learning Forum

[Crammer1]

Please I need help on this simulation.

I'm a simulating a water-liquid/water-vapor natural convective heat transfer. below is the detail of my simulation.

Method: Boussinesq Assumption

working fluid: water-liquid and water-vapor at 443.15K.

i set 453.15K as the wall temperature of heat source and 433.15K as the wall temperature of heat sink

i used wall temperature of heat source, that is 453.15 as the Boussinesq operating temperature.

i used Phase Coupled SIMPLE and Second Order Upwind in the solution methods.

i run the calculation and got converged solution but there is no volume fraction (zero volume fraction).

i do not know how to calculate Diameter of the material (water-vapor at 443.15K) in the secondary phase.

i also don not know how to measure vapor volume fraction in the ANSYS fluent. i used volume integral which used the solid walls of the domain to measure the volume fraction. am I right?

Below are some pictures of the simulations for your considerations. 

[Crammer1]

I'm very sorry for the pictures

 

[Rob]

Boussinesq is only usable for a temperature range of about 10K, so you may want to review the material properties. Does the domain have openings? 

Re phase interaction, I assume you've added a method for the liquid to boil? 

Vapour bubble diameter just needs to be representative so it's model dependent. If it's a small domain 50microns may be OK, for a large domain 1-10mm may be more suitable. 

Monitoring vapour volume fraction is dependent on what you need to know. Volume average may be a good measure; click on "Help" on the reports panel and read though the definitions. 

[Crammer1]

do you mean temperature range between surface (hot wall) temperature and fluid temperature? or between the heat source (hot wall) and the heat sink (cold wall)? which one please!.

I used closed domain, has no opening as seen below.

the diameter of the domain is 0.1m, and for another domain is 0.2m, so how much value should i give the property diameter of the secondary phase (vapor)?

What i actually want to know whether boiling occur during the heat transfer and the mass flow rate.

Thank you for your respond. i need further responds to other previous and just mention questions  

[Rob]

Typically you want a (fluid) material dT under 10K.  

However, think through the model. Liquid expands as temperature rises then boils so gas is formed. If the system is fixed volume, and the liquid density doesn't actually change (Boussinesq is a body force method) where does the gas go, and what will it's density be?