![](\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/05\/04-05-2023-1683206958-mceclip1.png\")
<\/p>\nAfternoon!<\/p>\n
I have written a UDF to calculate the saturation temperature of water vapour for use with the Lee model of evaporation and condensation.<\/p>\n
The problem I am testing the UDF on is:<\/p>\n
<\/p>\n
The primary phase is a mixture of water vapour and air (initialised to mass_fraction_air = 1 at inlet), and the secondary phase is liquid water, patched into the tank as indicated by the region with t_sat = 372K in the image below.<\/p>\n
The saturation temperature (and therefore the UDF) appears to be appropriate at all points in the domain upon Initialisation:<\/p>\n
![](\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/05\/04-05-2023-1683207456-mceclip2.png\")
<\/p>\n
However! I am not observing any mass transfer, and for the life of me can’t figure out what’s amiss. Even with significant run-time (the simulation is, of course, transient), the saturation temperature throughout the domain remains unchanged, reinforcing the fact that no mass transfer of water vapour has occured!<\/p>\n
On a physical basis, there should be evaporation in the interface region from the get-go. The entire problem domain is initialised to 20degC (293.15K), and there are cells in the interface region with a non-zero volume fraction of liquid water (secondary phase) at this temperature which is above the saturation temperature in those cells<\/em>.<\/p>\n To demonstrate, along a horizontal line near the top of the interface region, the volume fraction of water is ~0.1,<\/p>\n the saturation temperature is ~283K,<\/p>\n and the total temperature (mixture) is 293K<\/p>\n yet there is no mass transfer!<\/p>\n I have adjusted the ‘From Phase Frequency’ and ‘To Phase Frequency’ through a wide range of values to no avail.<\/p>\n Would anyone that has worked on a similar problem before be able to make some suggestions that I can work on? Any help would be warmly appreciated.<\/p>\n","protected":false},"template":"","class_list":["post-282364","topic","type-topic","status-closed","hentry","topic-tag-multiphase_models-1","topic-tag-evaporation-condensation","topic-tag-lee-model-1","topic-tag-mass-transfer","topic-tag-mixture","topic-tag-transient","topic-tag-udf"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["14299","199"],"_bbp_author_ip":["23.220.96.181"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["4719"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["282364"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","14299"],"_bbp_voice_count":["2"],"_bbp_reply_count":["14"],"_bbp_last_reply_id":["283272"],"_bbp_last_active_id":["283272"],"_bbp_last_active_time":["2023-05-10 12:52:45"]},"test":"julio-guzmancampoyqanalytica-co-uk"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/282364","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/282364\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=282364"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![](\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/05\/04-05-2023-1683209822-mceclip3.png\")
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