{"id":1881,"date":"2014-04-01T08:00:12","date_gmt":"2014-04-01T13:00:12","guid":{"rendered":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/?p=1881"},"modified":"2014-04-03T10:34:41","modified_gmt":"2014-04-03T15:34:41","slug":"simple-equations-to-approximate-changes-to-the-properties-of-crude-oil-with-changing-temperature","status":"publish","type":"post","link":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/2014\/04\/simple-equations-to-approximate-changes-to-the-properties-of-crude-oil-with-changing-temperature\/","title":{"rendered":"Simple Equations to Approximate Changes to the Properties of Crude Oil with Changing Temperature"},"content":{"rendered":"

This Tip of the Month describes simple equations to approximate changes to the properties of crude oil with changing temperature.\u00a0\u00a0 Changes in crude oil density and specific heat, or heat capacity, can be estimated from graphs and\/or more elaborate computer simulation.\u00a0 The latter generally requires access to a process simulator and characterization data for the crude oil.\u00a0 A suitable, tuned computer model is likely the most accurate method of estimating the fluid properties, but is not always available.\u00a0 Direct laboratory measurement is also possible if facilities and oil samples are available and a high degree of accuracy is required.<\/p>\n

Graphs, which were originally generated from empirical data, can be useful, and their accuracy is suitable for most engineering applications. However; use of the data in subsequent calculations requires users to interrupt the calculation, look up a number from a graph, and then proceed with the calculation.\u00a0 The simple curve-fit equations presented provide the required data suitable for use in spreadsheet or hand calculations.<\/p>\n

Crude Oil Density<\/strong><\/p>\n

Figure 1A (1) depicts the change in specific gravity with temperature for crude oils of varying API gravity.<\/p>\n

\"\"<\/a>
Figure 1A Crude Oil Specific Gravity vs Temperature (1)<\/figcaption><\/figure>\n

This graph was compared with density-temperature data from Table D-1, API Publication 421, \u201cMonographs on Refinery Environmental Control \u2013 Management of Water Discharges\u201d (2).\u00a0 The colored lines in Figure 1B show the API data superimposed on the original graph. The two show good agreement.<\/p>\n

\"\"<\/a>
Figure 1B Data from API Publication 421 superimposed on Figure 1A (data from (2))<\/figcaption><\/figure>\n

Curve fitting data from Figure 1A resulted in Equation 1 for FPS units.\u00a0 Equation 2 provides the SI equivalent.<\/p>\n

\"\"<\/p>\n

Figure 1C displays the output from Equation 1 superimposed as colored lines on the original graph (Figure 1A). Although the simple equation does not align perfectly, results are sufficiently accurate for most engineering calculations.\u00a0 Compared to the data from API Publication 421,\u00a0 Equation 1 produces a maximum errors of +0.25% and -0.3%.<\/p>\n

\"\"<\/a>
Figure 1C Simple Equation 1 superimposed on Figure 1A<\/figcaption><\/figure>\n

 <\/p>\n

Heat Capacity<\/strong><\/p>\n

A similar approach was used to develop a simple equation for the variation of the Heat Capacity or Specific Heat of crude oil as a function of API gravity and Temperature.\u00a0 Data, extracted from Figure 2A (1), was regressed to obtain the algorithm presented as Equation 3 for FPS units: Equation 4 for SI units.\u00a0 Note that the algorithm was developed for a crude oil with a UOP index of 11.8 (indicating intermediate, paraffinic-naphthenic crude).\u00a0 If the UOP index is known, the correction factor illustrated on the graph could be applied to the output from Equation 3 or 4.<\/p>\n

\"\"
Figure 2A Heat capacity of crude oil vs Temperature (1)<\/figcaption><\/figure>\n

The resulting equation is presented as Equation 3 for FPS units, and Equation 4 for SI units.<\/p>\n

\"\"<\/p>\n

\"\"
Figure 2B Simple Equation 3 superimposed on Figure 2A<\/figcaption><\/figure>\n

 <\/p>\n

Summary<\/strong><\/p>\n

The simple equations provide approximations for the variation of density and specific heat of crude oils of varying API gravity.\u00a0 Neither algorithm provides a perfect match with the underlying data.\u00a0 However; data from varying sources do not always correlate.\u00a0 Figure 3A (1) depicts an alternate source of density correction for crude oils for varying API gravity and temperature.\u00a0 Figure 3B shows data from API Publication 421 (colored lines) superimposed on a portion of Figure 3A.\u00a0 Unfortunately, overlap of the data is limited, but clearly there is a very poor correlation \u2013 even the trend as API gravity increases is reversed between the API data and the data presented in Figure 3A.\u00a0 Note that the trend represented in Figure 1A is supported by data from API 421 Appendix D.\u00a0 These data (from the API Publication 421) are taken here as being most reliable.\u00a0 Overall, Figure 1A shows quite good agreement with the API data, so the algorithm (Equations 1 and 2) was developed using data from Figure 1A as the source.<\/p>\n

\"\"
Figure 3A Crude Oil Density Correction Factor (Hankinson et al, 1979) (1)<\/figcaption><\/figure>\n
\"\"
Figure 3B Portion of Figure 3 A with data from API 421 superimposed<\/figcaption><\/figure>\n

To learn more about similar cases and how to minimize operational problems, we suggest attending our G40<\/strong> (Process\/Facility Fundamentals<\/a>)<\/a>, G4 (<\/a><\/strong>Gas Conditioning and Processing<\/a>)<\/a>, PF81 (<\/a><\/strong>CO2<\/sub> Surface Facilities<\/a>)<\/a>, and PF4 (<\/a><\/strong>Oil Production and Processing Facilities<\/a>)<\/a> <\/strong>courses.<\/p>\n

John M. Campbell Consulting (JMCC) <\/em>offers consulting expertise on this subject and many others. For more information about the services JMCC provides, visit our website at\u00a0www.jmcampbellconsulting.com<\/a>, or email us at consulting@jmcampbell.com<\/a>.<\/p>\n

By Wes Wright<\/p>\n

Works Cited<\/strong><\/p>\n

1. Manning, Francis S. and Thompson, Richard E.<\/strong> OILFIELD PROCESSING Volume Two: Crude Oil. <\/em>Tulsa\u00a0: PennWell Publishing Company, 1995. ISBN 0-87814-354-8.<\/p>\n

2. Institute, American Petroleum.<\/strong> Management of Water Discharges: Design and Operation of Oil-Water Separtors. <\/em>Washington\u00a0: API, 1990. API Publication 421.<\/p>\n

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

This Tip of the Month describes simple equations to approximate changes to the properties of crude oil with changing temperature.\u00a0\u00a0 Changes in crude oil density and specific heat, or heat capacity, can be estimated from graphs and\/or more elaborate computer simulation.\u00a0 The latter generally requires access to a process simulator and characterization data for the […]<\/p>\n","protected":false},"author":192,"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_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[6,10,4],"tags":[],"coauthors":[20],"class_list":["post-1881","post","type-post","status-publish","format-standard","hentry","category-pipeline","category-process-facilities","category-refining"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p1pQc4-ul","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/posts\/1881","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\/192"}],"replies":[{"embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/comments?post=1881"}],"version-history":[{"count":4,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/posts\/1881\/revisions"}],"predecessor-version":[{"id":1893,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/posts\/1881\/revisions\/1893"}],"wp:attachment":[{"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/media?parent=1881"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/categories?post=1881"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/tags?post=1881"},{"taxonomy":"author","embeddable":true,"href":"http:\/\/www.jmcampbell.com\/tip-of-the-month\/wp-json\/wp\/v2\/coauthors?post=1881"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}