# UDF for heat and mass transfer, transient simulation

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 November 11, 2018, 23:46 UDF for heat and mass transfer, transient simulation #1 New Member   Akash Siddique Join Date: Apr 2018 Posts: 10 Rep Power: 5 Hi Everyone !!! I'm stuck with the UDF for heat and mass transfer between air and desiccant material. In this problem, air passes between the desiccant block, heat & mass transfer happen due to the humidity of air adsorbed by desiccant material on its surface I'm facing difficulty in writing UDF for this problem Equations are given as: dfsfd.PNG Equation 1: Variable Air Temperature(Ta) = 1162 – (100/z), (z = distance along axis=0.01-0.4m) Equation 2: Variable Adsorbent Temperature = .06+ (.05/t^.19), (t=time duration =0-3600) Equation 3: Variable Air Humidity Ratio = -22(41*t^.1)-.625(4/z), (z= distance along axis, t=time) I need your help badly, and I hope you will cooperate afzalkhangm001@gmail.com Here is my email address

 November 13, 2018, 00:08 #2 Senior Member   Alexander Join Date: Apr 2013 Posts: 1,763 Rep Power: 28 imagine, you have codes for those tree equations Code: ```Equation 1: Variable Air Temperature(Ta) = 1162 – (100/z), (z = distance along axis=0.01-0.4m) Equation 2: Variable Adsorbent Temperature = .06+ (.05/t^.19), (t=time duration =0-3600) Equation 3: Variable Air Humidity Ratio = -22(41*t^.1)-.625(4/z), (z= distance along axis, t=time)``` what will you do with them? How are you going to connect them to fluent solver? best regards Akash Siddique likes this.

 November 13, 2018, 05:43 #3 New Member   Akash Siddique Join Date: Apr 2018 Posts: 10 Rep Power: 5 Well, I will interpret the UDF in fluent and complete my simulation. I hope this will get good results. I will be thankful to you if you help me in any way.

 November 13, 2018, 20:47 #4 Senior Member   Alexander Join Date: Apr 2013 Posts: 1,763 Rep Power: 28 I mean, which model you a going to use for this simulation? So you have: - Variable Air Temperature(Ta), function of coordinate - Variable Adsorbent Temperature, function of time - Variable Air Humidity Ratio, function of both time and coordinate Fluent has only one temperature, which is calculated using energy equation. So I can imagine you will initialize temperature field according to Variable Air Temperature(Ta). But what you are going to do with Variable Adsorbent Temperature and Variable Air Humidity Ratio How they are connected to energy/flow equations? best regards Akash Siddique likes this.

 November 27, 2018, 00:28 #5 New Member   Akash Siddique Join Date: Apr 2018 Posts: 10 Rep Power: 5 Thanks for your kind reply I must say this is a good question. I'm at the beginning level in Ansys. So, I will try to explain it according to my abilities. Kindly correct me if you find my reasoning inappropriate. I'm learning Ansys by watching youtube videos on similar topics. So, as per my understanding, I need to use " Species model" for air humidity ratio. I think these Two models (Energy, Species) are enough to complete my simulation. Am I on right Track ?? Please enlighten me And I'm extremely sorry for late reply. I hope you will cooperate

 December 5, 2018, 08:12 #6 New Member   Akash Siddique Join Date: Apr 2018 Posts: 10 Rep Power: 5 please somebody help me with UDF

 December 6, 2018, 22:57 #7 Senior Member   Alexander Join Date: Apr 2013 Posts: 1,763 Rep Power: 28 As I understand, your problem is some kind of condensation/evaporation simulation. SO I suggest you to start with regular condensation/evaporation simulation, later you may move to implementation of UDF inside, which is not a big deal, actually best regards Akash Siddique likes this.

 December 7, 2018, 06:32 #8 New Member   Akash Siddique Join Date: Apr 2018 Posts: 10 Rep Power: 5 Thanks for your reply Actually, I have already completed my work but only missing piece in completing the simulation is UDF. I'm also in the process of learning how to write code but it is taking too much time and I want to complete my simulation soon. So any help will be appreciated Best Regards

 Tags heat and mass transfer, transient simulations, udf