{"id":1571,"date":"2005-08-01T11:06:29","date_gmt":"2005-08-01T16:06:29","guid":{"rendered":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/?p=1571"},"modified":"2012-12-06T11:14:47","modified_gmt":"2012-12-06T17:14:47","slug":"where-did-my-compressor-power-go","status":"publish","type":"post","link":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/2005\/08\/where-did-my-compressor-power-go\/","title":{"rendered":"Where did my Compressor Power Go?"},"content":{"rendered":"

In a previous \u201cTip of the Month\u201d we briefly discussed the problems of how to \u201cname\u201d the various regions of the phase diagram. To decide if this \u201cnaming game\u201d can be a problem, look at Figure 1.<\/p>\n

This is a typical two-stage compressor system with intercoolers. This particular system however is being used to compress gas to a pressure above the cricondenbar of the gas for \u201cdense phase\u201d transportation. Note that the streams are only labeled with letters because I used numbers on the phase diagram. As a \u201cprocess engineer\u201d I find it difficult to discuss streams with out seven digit numbers identifying them.<\/p>\n

Point A is easily \u201cdefined\u201d as a saturated vapor. Point B will be superheated vapor or possibly dense phase. Point C might be 2 phase, super heated vapor, dense phase, or liquid phase. From an equipment point of few in all cases but the two-phase case, separator V-2 is not needed, in theory. In practice, we would always install V-2 as very minor changes in temperature or pressure can sometimes dramatically change the quantity of liquid in stream E.<\/p>\n

For computer simulation of this process, the designation of the \u201cphases\u201d of stream C becomes quite important. Assuming the simulator has the ability to calculate Vapor-Liquid equilibrium properly, the two-phase case is the only case where the simulator can be trusted to give the proper duty requirements for compressor C-2.<\/p>\n

Figure 2 is the \u201cgeneric\u201d phase diagram for a light mixture that we previously discussed. The general areas are: to the left of the phase diagram \u2013 liquid; area to the right of the phase diagram \u2013 vapor; the area inside the phase diagram \u2013 two phase; and the area above the phase diagram \u2013 dense phase.<\/p>\n

My personal preferences for the sub areas are listed below:
\nArea 1 \u2013 Vapor
\nArea 2 \u2013 Vapor
\nArea 3 \u2013 Vapor
\nArea 4 \u2013 Vapor
\nArea 5 \u2013 Dense phase
\nArea 6 \u2013 Liquid
\nArea 7 \u2013 Liquid
\nArea 8 \u2013 Liquid
\nArea 9 \u2013 Vapor<\/p>\n

The stream labels from figure 1 are plotted on the diagram. Note this assumes that the phase diagram represents the composition of the gas leaving separator V-1.<\/p>\n

If stream C is \u201cnamed\u201d vapor by the simulator, then most computer simulations will properly calculate the power requirements of C-2. If stream C is \u201cnamed\u201d liquid by the simulation program then C-2 will have no flow through it. The program will either \u201cfail\u201d or worse yet give meaningless answers. Worse yet some simulators identify point C as two-phase with an arbitrary split between the flow rates of streams D and E.<\/p>\n

The current trend in commercial simulators is to always \u201cgive an answer\u201d no mater how \u201cstupid the question is.\u201d Most simulators will generally give warnings when calculating a \u201cmeaningless\u201d answer, but with the current shortage of engineers, the chances of these being identified are fairly small.<\/p>\n

This is a simple example of how \u201cnaming\u201d can get you in trouble. There are many more that occur subtly inside simulations. Many of these errors go undetected because the program is quite \u201chappy\u201d with whatever phase it calculates.<\/p>\n

For examples of how the choice of the name might be important in your process simulation calculations, contact JMC@jmcampbell.com for test simulations that you can use with your process simulator.<\/p>\n

At a future date we will discuss the meaning of \u201ccondensate\u201d and why this is so politically important even today.<\/p>\n

In the meantime Chapter 4 and 5 of Volume I and chapter 15 of Volume II of Gas Conditioning and Processing and Chapter discusses these topics in more detail.<\/p>\n

The stream labels from figure 1 are plotted on the diagram. Note this assumes that the phase diagram represents the composition of the gas leaving separator V-1.<\/p>\n

WHAT If stream C is \u201cnamed\u201d vapor by the simulator, then most computer simulations will properly calculate the power requirements of C-2. If stream C is \u201cnamed\u201d liquid by the simulation program then C-2 will have no flow through it. The program will either \u201cfail\u201d or worse yet give meaningless answers. Worse yet some simulators identify point C as two-phase with an arbitrary split between the flow rates of streams D and E.<\/p>\n

The current trend in commercial simulators is to always \u201cgive an answer\u201d no mater how \u201cstupid the question is.\u201d Most simulators will generally give warnings when calculating a \u201cmeaningless\u201d answer, but with the current shortage of engineers, the chances of these being identified are fairly small.<\/p>\n

This is a simple example of how \u201cnaming\u201d can get you in trouble. There are many more that occur subtly inside simulations. Many of these errors go undetected because the program is quite \u201chappy\u201d with whatever phase it calculates.<\/p>\n

For examples of how the choice of the name might be important in your process simulation calculations, contact JMC@jmcampbell.com for test simulations that you can use with your process simulator.<\/p>\n

At a future date we will discuss the meaning of \u201ccondensate\u201d and why this is so politically important even today.<\/p>\n

In the mean time Chapter 4 and 5 of Volume I and chapter 15 of Volume II of Gas Conditioning and Processing and Chapter discusses these topics in more detail.<\/p>\n

By: Dr. Larry L. Lilly<\/em><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n","protected":false},"excerpt":{"rendered":"

In a previous \u201cTip of the Month\u201d we briefly discussed the problems of how to \u201cname\u201d the various regions of the phase diagram. To decide if this \u201cnaming game\u201d can be a problem, look at Figure 1. This is a typical two-stage compressor system with intercoolers. This particular system however is being used to compress […]<\/p>\n","protected":false},"author":29,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[3],"tags":[],"coauthors":[21],"class_list":["post-1571","post","type-post","status-publish","format-standard","hentry","category-gas-processing"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p1pQc4-pl","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/posts\/1571","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/users\/29"}],"replies":[{"embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/comments?post=1571"}],"version-history":[{"count":2,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/posts\/1571\/revisions"}],"predecessor-version":[{"id":1575,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/posts\/1571\/revisions\/1575"}],"wp:attachment":[{"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/media?parent=1571"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/categories?post=1571"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/tags?post=1571"},{"taxonomy":"author","embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/coauthors?post=1571"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}